Title of Invention	"METHOD FOR SERVICING THE OUTER COMPONENTS OF A WIND TURBINE SUCH AS THE WIND TURBINE BLADES AND THE TOWER WITH A WORK PLATFORM AND WORK PLATFORM THEREFOR"
Abstract	The invention relates to a method of servicing the outer components of a wind turbine such as the wind turbine blades and the tower with a work platform, said method comprises the steps of: positioning the work platform at the wind turbine tower and connecting the work platform to an upper part of the wind turbine with at least one cable. Further the method comprises the steps of raising the work platform with the cable and cable winding means to a position of use, and holding the work platform to the side of the wind turbine tower with holding means. The invention also relates to a work platform for servicing the outer components of a wind turbine.

Title of Invention

"METHOD FOR SERVICING THE OUTER COMPONENTS OF A WIND TURBINE SUCH AS THE WIND TURBINE BLADES AND THE TOWER WITH A WORK PLATFORM AND WORK PLATFORM THEREFOR"

Abstract

The invention relates to a method of servicing the outer components of a wind turbine such as the wind turbine blades and the tower with a work platform, said method comprises the steps of: positioning the work platform at the wind turbine tower and connecting the work platform to an upper part of the wind turbine with at least one cable. Further the method comprises the steps of raising the work platform with the cable and cable winding means to a position of use, and holding the work platform to the side of the wind turbine tower with holding means. The invention also relates to a work platform for servicing the outer components of a wind turbine.

Full Text	AS THE WIND TURBINE BLADES AND THE TOWER WITH A WORK PLATFORM AND WORK PLATFORM THEREFOR Background of the invention The invention relates to a method of approaching, for servicing the outer components of a wind turbine such as the wind turbine blades and the tower with a work platform and a work platform therefor. Description of the Related Art Normally, wind turbines are erected in places in which the wind conditions are advantageous e.g. in places with few obstacles blocking or altering the path of the wind. This means that the wind turbines often are positioned in more or less remote places with a poor infrastructure such as in terms of road quality. This creates some problems in relation to the necessary maintenance of the outer components of the wind turbines such as the wind turbine blades or the surface of the wind turbine tower. The magnitude of the problems has accumulated significantly in recent years with the increasing size of the wind turbines. Previously, freestanding cranes or lifts have been used in connection with maintenance or reparation of the outer components of the wind turbines. However, with the poor infrastructure, the transportation of the cranes or lifts to the erection places of the wind turbines is somewhat costly and time consuming. In order to overcome the problem of transporting large and heavy equipment to the erection places different solutions have been suggested. WO 2004/092577 PCT/DK2003/000257 2 One has been using persons lowering them selves down the side of the wind turbine tower or blades using ropes connected to the nacelle. However, the method naturally requires experts in climbing and is somewhat restricted in the work possibilities on the wind turbine and as such not a feasible solution to the problems of maintenance or reparation of the outer components of the wind turbines. Another has been the installation of a crane and a cable basket underneath the nacelle of the wind turbine allowing the basket to be lowered down the side of the wind turbine. However, the basket is difficult to position correctly and difficult to work from due to its unstable nature. One of the objects of the invention is to establish a method and system for wind turbines without the above-mentioned disadvantage. It is an object of the invention to create a method and system which allow one or more workers to be positioned at any adjacent position outside the wind turbine such as near one of the wind turbine blades without involving heavy equipment on the ground. Further, it is an object of the invention to create a method and system which allow safe and stable conditions for the workers. The invention The invention relates to a method of servicing the outer components of a wind turbine such as the wind turbine blades and the tower with a work platform, said method comprises the steps of: positioning the work platform at the wind turbine tower, WO 2004/092577 PCT/DK2003/000257 3 connecting the work platform to an upper part of the wind turbine with at least one cable, raising the work platform with the cable and cable winding means to a position of use, and holding the work platform to the side of the wind turbine tower with holding means. Hereby it is possible to establish a method that allows safe and stable conditions for one or more workers performing service on the outer components of a wind turbine such as the wind turbine blades and the tower. In an aspect of the invention, said holding is established with at least two sets of suction or vacuum cups, allowing an easily controllable but still firm hold on the wind turbine tower. In a further aspect of the invention, said holding is enhanced by positioning said suction or vacuum cups on the ends of holding arms, said arms gripping around the exterior of the wind turbine tower. Hereby it is possible to establish a grip around the wind turbine tower, the grip being advantageous in absorbing and withstanding any twists in the work platform. In an even further aspect of the invention, said method further comprises the step of moving the work platform horizontally by extracting or retracting horizontal forcing means of the work platform. Hereby it is possible to position the work platform at any adjacent position outside the wind turbine such as near one of the wind turbine blades. In another aspect of the invention, the extracting or retracting is established telescopically by a number of arm sections in said horizontal forcing means. Hereby WO 2004/092577 PCT/DK2003/000257 4 a preferred embodiment of the invention is achieved that is simple to construct and control during use. In a further aspect of the invention, cable guiding means angles the cable outwards in relation to the wind turbine tower from the starting point of the cable. Hereby an advantageous embodiment of the invention is achieved. In an even further aspect of the invention, said work platform is moved up or down by following and rolling with steering wheels of the platform on the surface of the wind turbine tower. Hereby a further advantageous embodiment of the invention is achieved. The invention also relates to a work platform, said platform further comprises gripping means for holding the work platform to the tower. Hereby it is possible to establish an apparatus that allows safe and stable conditions for one or more workers performing service on the outer components of a wind turbine such as the wind turbine blades and the tower. In an aspect of the invention, said at least one cable comprises a number of outer cables, said set including a main cable and one or more additional cables. In a further aspect of the invention, said at least one cable further comprises an inner cable or cables. The more than one cable may enhance the safety level of the work platform. In an aspect of the invention, said inner and outer cables are fixed to the underside of the wind turbine nacelle at an inner and outer anchorage point in direction from the tower or to anchorage points inside the nacelle. WO 2004/092577 PCT/DK2003/000257 5 In an aspect of the invention, said gripping means comprises at least two sets of suction or vacuum cups. With two or more sets of suction or vacuum cups it is possible to engage the wind turbine tower from more than one side e.g. from opposite sides ensuring a more firm grip. However it shall be emphasized that the gripping means may be established with just one set of suction or vacuum cups engaging the tower in one position. The position is preferably in front of the work platform ensuring a balance for the platform around the position. The suction or vacuum cups may be used in connection with any type of wind turbine tower such as towers made in metal or concrete. In another aspect of the invention, said gripping means comprises at least two sets of electromagnetic means. The electromagnetic means may be one or more electromagnets in which the electric power supply for the magnets is controlled in order to hold on to/let go of the metal surface of the tower. In a further aspect of the invention, said gripping means comprises retaining means surrounding the wind turbine tower such as at least one retaining belt or band. The retaining means surround the tower totally or partly and are connected to the gripping means in which the gripping means may tighten or release the retaining means in order to hold the work platform at the position or to allow movement of the platform, respectively. The belt or band is preferably made in iron or an iron alloy. Further, the belt or band may be made in other materials such as a reinforced composite or woven material. In another aspect of the invention, each of said at least two sets of suction or vacuum cups or electromagnetic means are flexibly mounted to the end of a holding arm. With the flexible mounting of the cups or electromagnetic means an advantageous possibility of adapting the holding arms to the more or less uneven surface of the wind turbine tower is achieved. Further, with the flexible mounting the inclination of the tower does not affect the functionality of the cups or electromagnetic means. WO 2004/092577 PCT/DK2003/000257 6 In a further aspect of the invention, said holding arm includes a base arm section, inner arm section and outer arm section. By the sectioning of the arms, an ability of angling the arms individually is achieved in order to grip different sized wind turbine towers. In an even further aspect of the invention, said inner arm section and outer arm section are pivotally connected and controlled by arm actuating means in at least one direction. Hereby it is possible to adapt the arm sections to the inclination of the tower in question regardless of the (small) size of the inclination. In another aspect of the invention, said gripping means comprises one or more steering wheels. With the steering wheels it is easy to vertically move and roll the work platform to a given position of use. Further the steering wheels help controlling the path that the work platform follows when it is moved up or down the surface of the wind turbine tower. In an aspect of the invention, guard rails and a foundation define a work area of said platform. As modern wind turbines comprises a nacelle height of more than 50 meters the workers need protection from falling of the platform e.g. as a result of an unexpected wind gust or the like. In an aspect of the invention, said gripping means and the foundation are connected through horizontal forcing means. With the ability of forcing or moving the work platform horizontally, it is possible to work with different outer components of the wind turbine regardless of their position in relation to the wind turbine tower. Especially with modern wind turbines, in which the distance between the tower and the wind turbine blades may be between 5 and 10 meters, the ability of moving the work platform horizontally is advantageous. WO 2004/092577 PCT/DK2003/000257 7 In an aspect of the invention, said horizontal forcing means includes a number of horizontal forcing arms. With a number of arms, instead of one long arm, the forcing means may be constructed with a smaller length. In an aspect of the invention, said horizontal forcing arms are integrated into each other as part of telescopic forcing means. With the telescopic adaptation the necessary length may be obtained with a more compact construction of the forcing means. Further, the telescopic forcing means ensures that the horizontal forcing of the work platform is achieved with a linear approach of the forcing means. In an aspect of the invention, the side or sides of said platform includes one or more indentations for receiving and docking one or more wind turbine blades. The receiving and docking of the blade in an indentation is especially important as the indentation defines an area that at least partly surrounds the blade. The surrounding ensures that the blade may be retained from different positions e.g. retraining the leading or trailing edge together with both sides of the blade. Further, the workers may approach and get close to both sides of the blade without dangerously leaning out over the guide rails. In a special embodiment the blade may enter the indentation and subsequently be surrounded by the work platform, wherein the surrounding is achieved by closing a pivotally connected section of the platform behind the blade. The section preferably comprises the necessary guide rails allowing the workers to walk around the blade in its full circumference. It shall be emphasised that the blade may be docked at any position along the sides of the work platform. The indentations are merely adapted for a safer docking by allowing a better retaining of the blade. In an aspect of the invention, said platform includes retaining means for retaining the wind turbine blade in one of said indentations. The retaining means are important as WO 2004/092577 PCT/DK2003/000257 4' 8 they ensure that any movements in the blade is retained e.g. at a wind gust and thus protect the workers from potential injuries during the work on the blade. As the blade is positioned in an indentation the retaining means may attack from opposite side against the surface of the blade ensuring a solid and continuing hold on the blade. In an aspect of the invention, said retaining means includes one or more suction or vacuum cups positioned on one or more rods as base part for the retaining means. The hold by suction or vacuum cups ensures both the solid and continuing hold of the blade and at the same time a gentle hold without any pressure marks on the blade. In an aspect of the invention, said cable is controlled by cable guiding means e.g. by one or more cable guidance wheels in said means. The abrasion of the cable may be avoided and thus ensuring the security of the worker on the platform. In an aspect of the invention, said cable guiding means controls the angling of the cable. By controlling the angling of the cable, it is possible to achieve different advantageous characteristics such as forcing the work platform against the tower. By forcing the platform against the tower the necessary strength of the gripping means may be reduced. In an aspect of the invention, control means at least controls said arm actuating means, horizontal forcing means, said one or more suction or vacuum pumps and/or said cable winding means. In another aspect of the invention, said control means is connected wired or wirelessly to and controlled by at least one remote control. Equipped with a remote control the worker may move more freely on the platform and control the components of the platform more precisely and thus is both the flexibility and the security of the platform enhanced. WO 2004/092577 PCT/DK2003/000257 9 In a further aspect of the invention, said control means and auxiliary devices are controlled with more than one remote control, said controls working in a master and slave configuration. Hereby it is possible to control components of the work platform or with the auxiliary devices components of the wind turbine, such as the turning of the rotor, from different positions e.g. the work platform and the ground or the nacelle. The invention will be described in the following with reference to the accompanying drawings, in which fig. 1. illustrates a large modem wind turbine, fig.2a illustrates a work platform according to the invention moving upwards on the side of a wind turbine tower, fig. 2b illustrates the work platform in a use situation, fig. 3 illustrates in more details the work platform on the side of a wind turbine tower, fig. 4 illustrates the positioning of a wind turbine blade in relation to the work platiorm, the platform seen from below, fig. 5 illustrates in perspective the work platform according to a preferred embodiment of the invention, WO 2004/092577 PCT/DK2003/000257 10 fig. 6 illustrates the connection between the wind turbine and the work platform including a section hereof, figs. 7a and 7b illustrate the work platform in which the pushing actuator means are in two different extraction positions; figs. 8a to 8c illustrate different extraction positions of a preferred embodiment of the pushing actuator means, figs. 9a and 9b illustrate a preferred embodiment of suction or vacuum cups according to the invention in front and rear views, figs. 10a and 10b illustrate a preferred embodiment of cable winding means including a box holding the cable winding means, fig. 11 illustrates a flow diagram relating to a method of servicing the outer components of a wind turbine, and fig. 12 illustrates an embodiment of a control system in connection with a work platform according to the invention. Detailed description Fig. 1 illustrates a modern wind turbine 1 with a tower 2 and a wind turbine nacelle 3 positioned on top of the tower. The wind turbine rotor 5, comprising three wind turbine blades, is connected to the nacelle through the low speed shaft which extends out of the nacelle front. WO 2004/092577 PCT/DK2003/000257 11 As illustrated in the figure, wind beyond a certain level will activate the rotor due to the lift induced on the blades and allow it to rotate in a perpendicular direction to the wind. The rotation movement is converted to electric power, which is usually supplied to the transmission grid as known by skilled persons within the area. Fig. 2a illustrates a work platform 6 according to the invention moving upwards on the side of a wind turbine tower in connection with a maintenance or reparation job on the wind turbine 1. Further, it is illustrated that the wind turbine blades are pitched out of the wind (parallel with the wind) and not moving as the wind turbine is stopped during the job. The figure also illustrates that a worker is positioned inside the work platform. i The work platform is connected to the wind turbine nacelle 3 with at least one cable 7 in which the cables arrive at the nacelle from a position underneath the nacelle. The work platform also comprises gripping means 8 that substantially horizontal reaches out against the side of the wind turbine tower 2. The cables 7 may be an integrated part of the wind turbine located inside the nacelle and lowered to the ground through openings in the bottom of the nacelle. Further, the cable may arrive together with the work platform 6 and be transported to the nacelle e.g. by a worker carrying the cable to the nacelle using the stairs inside the wind turbine, securely fastening one end of the cable to the nacelle and lowering the other end down to the ground. Another way would be to carry a thin rope to the nacelle and lower it down to the ground, tie it to a cable end and drag the cable up to the nacelle on the outside of the wind turbine tower e.g. with the aid of a lifter in the nacelle before securely fastening the cable to the nacelle. WO 2004/092577 PCT/DK2003/000257 12 After the cable has reached the ground or the nacelle, it is fastened to cable winding means of the work platform allowing the work platform to be raised from the ground by winding the cable on the work platform. However, in a further embodiment the cable winding means may be positioned in the nacelle and the cable thus only firmly secured to the work platform. The accumulators may, in another embodiment of the work platform, be replaced or supplemented with a diesel generator positioned on the work platform. Finally, the figure illustrates that the work platform was transported to the place of the wind turbine on a trailer connected to a truck 9 e.g. the normal service truck of the company servicing wind turbines. The truck may include different tools or machinery needed in connection with the maintenance and reparation job. Further, the truck may be used in supplying power to the necessary electric accumulators or air containers of the work platform e.g. during transportation by charging the accumulators from the generator of the truck, or the containers from a compressor. Fig. 2b illustrates the work platform in a use situation at the tip of a wind turbine blade 5 in which the blade is ready for servicing by the worker on the platform. In order to arrive at the position of fig. 2b from the position of fig. 2 a the work platform is lifted with the cable winding means while steering wheels of the gripping means 8 are forced against the wind turbine tower allowing the work platform to roll over the surface of the tower during the displacement. After arrival at the position of use the work platform is still connected to the nacelle through the cables 7 but is also connected to the tower through the gripping means 8 which grippes the wind turbine tower 2 at least two positions (as will be explained in further details below). WO 2004/092577 PCT/DK2003/000257 13 The wind turbine blade is twisted to a position in which the worker has access to the surface of the blade (the blade being in a position substantially perpendicular to the wind at the figure). The wind turbine blade is also secured to the work platform in order to avoid any unintended movement of the blade during the work process. When the work is done at the position the gripping means 8 are released from the tower and the cable winding means lifts (and rolls) the work platform to a new position in which the gripping means 8 are once again secured to the tower. This may be repeated until the blade in its full length has been serviced. Hereafter the other wind turbine blades may undergo the same procedure. The blade to undergo the procedure is rotated to meet the side of the work platform in which the movement may be achieved by turning the high speed shaft linking the generator and the gear in the nacelle e.g. by an auxiliary device comprising an electric motor. Further, the movement may be achieved by using the generator as an electric motor taking electric energy from the public electric grid. Even further, a movement may be achieved by slightly and briefly pitching one or more blades into the wind. Fig. 3 illustrates a preferred embodiment of the work platform 6 according to the invention positioned on (and partly concealed by) the wind turbine tower 2. The work platform is constructed with a foundation 18 surrounded by guard rails 13 in which the foundation and the guide rails defining a work area for the worker or workers. The work platform further comprises cable guiding means 12 guiding two cables 7a, 7b to cable winding means 43. The cable winding means 43 comprises motor and gearing means in which the gearing means has a high gearing ratio e.g. 1500 motor shaft rotations for each cable winding. WO 2004/092577 PCT/DK2003/000257 14 The work platform further comprises a box 10 at the side wherein different hydraulic and/or pneumatic components may be positioned (as will be explained in connection with figs. 10a and 10b). In a first embodiment the cable winding means 43 are positioned at the foot of the cable guiding means 12 in which the winded cables 7 continue freely down under the platform or even stay on the floor of the platform, hi another embodiment of the invention the cables may be accumulated in a cable drum positioned inside the box 10 or another suitable place at the work platform. The cable guiding means 12 comprises a number of guidance wheels that direct the cables 7a, 7b to the cable winding means 43 and protect the cable from abrasion. The cable guiding means is preferably positioned centrally on the platform or the outer section of the platform in relation to the tower. In a situation in which the horizontal forcing means is fully retracted, the cables are vertical or preferably slightly angled to meet the cable guiding means. The angling of the cable is outwardly in relation to the wind turbine tower from its anchorage point of the wind turbine ensuring that the work platform, regardless of the degree of extraction of the horizontal forcing means, is forced against the tower. The angling is established with the positioning of the cable guiding means on the work platform and the anchorage point. In order to freely adapt the work platform to different anchorage points the point of attack of the cable guiding means may be moved horizontally. As the point of attack may be seen as the cable guidance wheels of the cable guiding means the movement of the attack point may be achieved by moving the wheels. The moving may be established by having sets of openings for holding the shafts of the cable guidance wheels in which the sets are spaced apart. WO 2004/092577 PCT/DK2003/000257 15 The work platform also comprises different docking areas lla, lib for a wind turbine blade. The first docking areas lla are indentations on the opposite side of the work platform in which the blade is allowed to enter one of the indentations with the front or trailing edge facing the work platform. When the blade is positioned in the indentation, retaining means from the work platform is forced against the sides of the blade keeping the blade fixed in relation to the work platform. With indentations on opposite side of the work platform it is possible to service wind turbine blades from both sides of the platform but the work platform may also work with just one first docking area lla. The first docking areas and further docking areas are described in relation to fig. 4. The figure further illustrates the one (non-concealed) half of the gripping means 8 of the work platform. The gripping means includes an arm stretching out along the side of the wind turbine tower. The arm fairly follows the surface of the wind turbine tower by comprising a number of arm sections pivotally connected to each other. The gripping means 8 comprises a steering wheel 14 approximately at half-length of the arm, the wheel being forced against the surface of the tower 2. Further, at the end of the gripping means 8, holding means 15 is positioned for holding onto the wind turbine tower 2. Fig. 4 illustrates the positioning of a wind turbine blade in relation to the work platform, the platform seen from below. The figure illustrates blades positioned in docking areas; on one side of the work platform (solid line in the presentation a cross section of the blade) and on the opposite side (dotted line). The blades are both docked with the leading or trailing edge facing the side of the work platform and the diametrical line of the blades being perpendicular to the longitudinal direction of the platform. The figure also illustrates a situation in which the blade is docked parallel with the longitudinal direction of the platform in a further indentation 1 lb (dotted line). The blade may be retained in the WO 2004/092577 PCT/DK2003/000257 16 further indentation by securing a strap around the blade and fixing the strap ends to the guide rail. The figure further illustrates the retaining means being forced against the sides of the wind turbine blade. Each of the retaining means comprises a head and a base 16a, 17a; 16b, 17b, respectively. The retaining means may simply be rubber heads or similar flexible members on rods forced against the sides and fastened to the work platform ensuring that the blade is retained. However, the retaining heads may also be suction or vacuum cups e.g. with connection to a vacuum pump. Fig. 5 illustrates the preferred embodiment of the work platform in its entirety and in perspective. Especially the figure illustrates the gripping means 8 in its entirety with both holding arms stretching out to grip the wind turbine tower at two positions with the holding means 15a, 15b or to roll on the surface of the tower with the two steering wheels 14a, 14b. As it is also seen on the figure each arm of the gripping means 8 comprises a base arm section 21a, 21b connected to an inner arm section 20a, 20b, said inner arm is connected to an outer arm section 19a, 19b. The base arm sections are further connected to each other and the work platform through a base part comprising horizontal forcing means 23. The connection between the base and the inner arm sections is made rigid by a sidepiece. The connection between the inner and the outer arm sections 19a, 20a; 19b, 20b is made variable by using a pivotal connection and arm actuating means 22a, 22b, such as linear electric, hydraulic or pneumatic actuators, allowing the outer arm sections and especially the holding means 15a, 15b to be moved closer to or further away from each other. WO 2004/092577 PCT/DK2003/000257 17 Further, the figure illustrates another cable 7c extending toward the work platform and entering at cable guidance means on the platform. The cable guidance means directs the cable 7c to the cable winding mechanism 44 at the centre of the gripping means 8. Finally, the figure illustrates one of the retaining means 16b, 17b for retaining a wind turbine blade in greater details. The work platform, and especially the essential parts, such as the foundation of the work platform 18, the horizontal forcing means 23 and/or the gripping means 8, are preferably made in steel or steel alloys. However, other metals may be used in the construction of the work platform such as aluminium or aluminium alloys. Further different composite materials may be used such as glass, aramid or carbon fibre materials. The cables connecting the work platform with the upper part of the wind turbine are preferably steel wires. Ropes such as a nylon rope may also be used if the strength of the ropes is significant enough to hold the platform including the workers. Fig. 6 illustrates the connection between the wind turbine and the work platform. The connection comprises several cables 7 that extend from the nacelle 3 to different positions on the work platform 6. The cables are divided in inner or outer cables in which the terms "inner" and "outer" are to be understood as their position in relation to the surface of the wind turbine tower. In a preferred embodiment the inner and outer cables are connected to different anchorage points on the underside of the nacelle. The points are positioned somewhere between the wind turbine tower 3 and the wind turbine rotor 5 with the inner point closer to the tower than the outer point e.g. 0.2 and 1.2 meter from the tower, respectively. WO 2004/092577 PCT/DK2003/000257 18 The inner and outer cables extend to an inner and an outer position at the work platform in which they are connected to separate cable winding mechanisms 43, 44, as explained in relation to figs. 3 and 4. The enlarged section view further illustrates a preferred embodiment of the invention and especially the extension of the inner 7c and outer cables 7a, 7b from the underside of the nacelle. The inner cable is illustrated as one cable 7c that extend from an inner anchorage point to the inner position at the work platform with the inner cable winding mechanism 44. The inner cable forms an angle a with the underside of the nacelle. The angle is preferably 90 degrees, the cable extends vertically, or less than 90 degrees, the cable extends outwardly in relation to the tower from the anchorage point. The outer cables are illustrated as two cables 7a, 7b that extends from an outer anchorage point 45 to the outer position at the work platform. As explained above, the cable guiding means 12 is the outer position at the work platform that guides the cables to the outer cable winding mechanism 43. The outer cables form an angle P with the underside of the nacelle. The angle is preferably 90 degrees, the cables extend vertically, or less than 90 degrees, the cables extend outwardly in relation to the tower from the anchorage point. The anchorage points may be eyelets or similar preinstalled connection points on the underside of the nacelle. In order to get to the anchorage points, the nacelle may comprise one or more small openings in the floor of the nacelle allowing a worker to position the cable at the anchorage point. Alternatively, the cables may enter the nacelle through openings and be fixed to anchorage points inside the nacelle. WO 2004/092577 PCT/DK2003/000257 19 The function of the cables 7a, 7b, 7c is the moving of the work platform, i.e. lifting or lowering the work platform. The inner cable ensures that the inner section of the work platform, including the gripping means 8, is correctly moved regardless of the conditions of the surface that the steering wheels 14 meet on the wind turbine tower. The outer cables ensure that the work platform as such is moved and especially that the outer section of the work platform is moved. The outer cables are divided into a main cable and one or more additional cables for security reasons. The main cable may single-handed carry the weight of the work platform but in case of a cable break the additional cables will maintain the work platform at the position. Further, the winding speed of the cables are monitored by safety means ensuring that the winding speed does not exceed an upper limit such as 4 meters per minute. The safety limit ensures that the work platform is not handled at dangerously high speeds, e.g. by the worker, under normal conditions or at failure situations such as a breakdown in a cable winding mechanism. The overspeed safety means is preferably electro/mechanical devices of a centrifugal or a magnetic motion type that slows down or temporarily stops the work platform. The safety means may also stop the work platform in a situation of cable overwind or weight overload. In order to keep the work platform horizontal or at least relatively horizontal, the platform comprises level indication means. The level indication means may be a part of the control system, described in relation with fig. 12, and as such be part of the system generating control signals for the cable winding mechanisms ensuring the horizontal position of the work platform. The level indication means may be combined with tension means monitoring the tension on each of the different cables. Both at vertical and horizontal movement of the work platform it is important to monitor and ensure the horizontal position of the work platform, and it may be achieved by controlling the cable winding mechanisms individually e.g. in order to achieve the horizontal position and level the strain on the cables. WO 2004/092577 PCT/DK2003/000257 20 In a basic embodiment of the invention the number of cables is set to just one cable wherein the cable is extended to an outer position of the work platform such as the cable guiding means 12. Further, the cables may be fixed to the work platform and connected with cable winding mechanisms in the nacelle. Figs. 7a and 7b illustrate the work platform and especially the horizontal forcing means 23 in two different positions. Fig. 7a illustrates the first position in which the horizontal forcing means 23 is folly retracted. The retraction of the horizontal forcing means 23 will position the work platform close to the wind turbine tower, e.g. allowing inspection and repair of the surface of the tower. Further, the position will be the normal position during truck transportation of the work platform as well as the normal position during the initial lifting of the work platform along the wind turbine tower. Fig. 7b illustrates a second position in which the horizontal forcing means 23 is partly extracted. As seen on the figure, the horizontal forcing means 23 includes a number of horizontal forcing arms. The arms may preferably be four-sided tubes in which the tubes are telescopically integrated into each other. The tubes may be extracted or retracted successively or individually by means of electric, hydraulic or pneumatic means. The electric means may include one or more electric motors driving one or more spindles. The hydraulic or pneumatic means may include a piston driven by the hydraulic or pneumatic forces. WO 2004/092577 PCT/DK2003/000257 21 The extraction of the horizontal forcing means 23 will position the work platform away from the wind turbine tower, e.g. allowing service of the surface of the wind turbine blades. As the distance between the wind turbine tower and the blades are quite significant at modern wind turbines, the horizontal forcing means 23 should at full extraction be of a certain length such as between 5 and 10 meters in order to be able to service any type of modern wind turbine. It should be understood that the term "horizontal forcing means" means that the forcing means preferably acts in a substantially horizontal direction against the wind turbine tower. However, the forcing means may in other embodiments be sloped to an angle significantly above or below the horizontal direction. Figs. 8a to 8c illustrate the structure of a preferred embodiment of the horizontal forcing means 23. The forcing means comprises a fixed part 25 holding the extractable and retractable horizontal forcing arms 23a, 23b. The fixed part is normally mounted underneath the foundation 18 of the work platform in its full length. The dotted lines may be seen as the surface of the wind turbine tower or the holding means 15 which the rest of the work platform is moved away from with the extraction of the forcing means. Fig. 8 a illustrates the structure in a retracted position for the horizontal forcing means 23. Fig. 8b illustrates the structure in an extracted position for a first horizontal forcing ami 23 a of the horizontal forcing means 23. WO 2004/092577 PCT/DK2003/000257 22 Fig. 8c illustrates the structure in an extracted position for a first and second horizontal forcing arm 23 a, 23b of the horizontal forcing means 23. The figure illustrates the horizontal forcing means 23 with both arms in fully extracted positions. However, in further embodiments the number of arms may be more than two arms e.g. the use of three or four arms of a shorter length than the present two Figs. 9a and 9b illustrate a preferred embodiment of the holding means 15 for the wind turbine tower. The holding means are preferably flexible mounted onto the ends of the outer arm sections 19a, 19b of the gripping means 8. The flexibility may be used in order to adapt the holding means to the slightly sloping surface of the wind turbine tower 2. Further, the holding means comprises two substantially oval holding devices (and rather long in an up-down direction) positioned next to each other. However, the number of holding devices and their shapes may be altered in order to meet different situations in which the present shape is preferred in order to advantageously absorb vertical forces. Fig. 9a illustrates the holding means 15 seen perceptively from the front. The holding means comprises an oval first and second suction or vacuum cup 27a, 27b. The second cup 27b includes a suction opening 28 in one end of the cup in which the opening is connected to a suction pump with tube means. Further, the second cup 27b includes a connection opening 29b in the other end of the cup. The opening is connected with a connection tube 30 to a connection opening 29a in the first suction or vacuum cup 27a. The connection between the two suction or vacuum cups ensures that a common pressure condition is established in the cups. The suction or vacuum cups may include rubber rims or lips 32 in order to retain the pressure condition inside the cups. WO 2004/092577 PCT/DK2003/000257 23 The two suction or vacuum cups are rigidly fastened to a connecting rod 31. The connecting rod 31 may on the other hand be flexibly fastened to the gripping means as mentioned above e.g. with some sort of a tip-up hinge. Fig. 9b illustrates the holding means 15 seen perceptively from the opposite side after being rotated half a turn. The figure especially illustrates the outlet of the suction opening 28 in which a tube, with connection to a suction pump, is to be mounted. The two suction or vacuum cups on each side of the gripping means may be used in order to firmly engage the work platform to the wind turbine tower by applying a very low suction pressure or even vacuum inside the cups facing the tower surface. Together with the cable and the cable winding means the work platform may be held in place by the gripping means. Figs. 10a and 10b illustrates the hydraulic and/or pneumatic means positioned in a box 34 at one side of the work platform. Fig. 10a illustrates the box 34 with ventilation opening 33 in a first and second box door 35a, 35b. The doors allow full access to the hydraulic and/or pneumatic means inside the box. Fig. 10b illustrates some of the content in the box including needle valves 36 controlling the hydraulic pump and tank 39 with the,motor 38. The magnetic controlled needle valves 36 thus control the hydraulic fluid pumped to the horizontal forcing means and other hydraulic actuated means of the work platform. The box further comprises a vacuum pump 39 that supplies the different suction or vacuum cups. The box may further comprise such means as electric accumulators and/or a WO 2004/092577 PCT/DK2003/000257 24 diesel generator, a cable drum 37 in which the cables 7, 7a, 7b, 7c are accumulated and one or more containers comprising compressed air. The air containers may be used as an energy source supplying some or all the energy consuming components of the work platform wherein the pressure of the containers preferably are quite high such as up to 40 bar. In an embodiment of the invention, compressed air is used instead of hydraulic pressure in retracting/extracting the horizontal forcing means. Further, the compressed air is used to drive the motors of the cable winding means in which the normally used electric motors are replaced with pneumatic motors. Even further, the compressed air is used to establish the necessary vacuum pressure for the suction or vacuum cups. The containers may be reloaded with compressed air from a compressor installed in the truck (as mentioned above) e.g. during the transportation from one site of wind turbines to another. The remaining components such as the control means may be supplied with electric power from one or more electric accumulators. The necessary energy may in another embodiment be supplied partly or totally from the hydraulic system in which the hydraulic oil is pressurized with nitrogen supplied from nitrogen containers. Even further, in an embodiment the different components may be supplied with electric power e.g. in order to drive the hydraulic and vacuum pumps in which the electric power is supplied from the utility grid. An electric cable may connect the work platform with a power outlet inside the wind turbine e.g. a 400 or 24 V AC outlet. In another embodiment the cable connects the work platform with the generator of the truck wherein the truck is kept running in order to supply the necessary electric power without emptying the truck accumulators. The electric cable may hang freely or be winded with a cable retraction mechanism. WO 2004/092577 PCT/DK2003/000257 25 From the box the necessary air and/or hydraulic tubes extend, to the different components that are supplied with suction or vacuum, pressurized air or hydraulic oil. Further, electric power cables may transfer energy from electric accumulators, a diesel generator or the utility grid to any electric actuated, activated or controlled components. Fig. 11 illustrates a flow diagram relating to a method of servicing the outer components of a wind turbine. The method may include some or all of the following steps of functionality in servicing a wind turbine such as the wind turbine tower: • driving the truck with the work platform to the rural place of the wind turbine or wind turbine park. • positioning the work platform in front of the wind turbine tower with the steering wheels of the gripping means touching the surface of the tower (step a of fig. 11). • connecting a cable to the wind turbine nacelle as described above (step b - part 1). • connection of the cable to the cable winding means of the work platform in which the cable preferably is a bit angled in relation to a vertical angle forcing the work platform slightly against the tower (step b - part 2). • vertically moving the work platform and one or more workers to a use position with the aid of the cable, the cable guiding means and the cable winding means (step c). WO 2004/092577 PCT/DK2003/000257 26 • securing the work platform to the wind turbine tower by activating the suction or vacuum cups 15 of the gripping means 8. • work on the wind turbine tower e.g. checking and repainting areas of the tower. • releasing the holding means and lowering the work platform to the ground and positioning the work platform on a transportation trailer (step f). • recharging the electric accumulators during transportation of the work platform to new rural places of wind turbines. In connection with the servicing of the wind turbine tower, a number of choices may be made including the decision regarding moving up or down when the work is finished in an area of the tower (step e). If the work is completed on the tower the work platform may be lowered to the ground. The method may include some or all of the following steps of functionality in servicing a wind turbine such as the wind turbine blades: • driving the truck with the work platform to the rural place of the wind turbine or wind turbine park. • positioning the work platform in front of the wind turbine tower with the steering wheels of the gripping means touching the surface of the tower (step a of fig. 11). • connecting a cable to the wind turbine nacelle as described above (step b - part 1). WO 2004/092577 PCT/DK2003/000257 27 • connection of the cable to the cable winding means of the work platform in which the cable preferably is a bit angled in relation to a vertical angle forcing the work platform slightly against the tower (step b - part 2). o vertically moving the work platform and one or more workers to a use position with the aid of the cable, the cable guiding means and the cable winding means (step c). • securing the work platform to the wind turbine tower by activating the suction or vacuum cups 15 of the gripping means 8. • altering the horizontal position of the work platform by extracting the horizontal forcing means in order to meet a wind turbine blade (step g). • retaining the wind turbine blade at the work platform, and servicing the section of the blade within reach (step h). • work on the wind turbine blade e.g. checking or cleaning areas of the blade. • altering the horizontal position of the work platform by retracting the horizontal forcing means e.g. allowing the wind turbine blades to turn briefly before securing a new blade to the work platform and performing the service process on this blade (step 1). The distance of the turn of the rotor is preferably approximately one third of a full turn in order to position the new blade in front of the blade docking area. • moving the work platform to a new use position with the aid of the cable and the cable winding means e.g. a higher position (step c). o securing the work platform to the wind turbine tower by activating the suction or vacuum cups 15 of the gripping means 8. WO 2004/092577 PCT/DK2003/000257 28 o altering the horizontal position of the work platform by extracting the horizontal forcing means in order to meet a wind turbine blade (step g). o retaining the wind turbine blade at the work platform and servicing the section of the blade within reach (step h). ... and so forth ... • releasing the holding means and lowering the work platform to the ground and positioning the work platform on a transportation trailer (step m). • recharging the electric accumulators during transportation of the work platform to new rural places of wind turbines. In connection with the servicing of the wind turbine blades a number of choices may be made including the decision regarding moving up or down when the work is finished in an area of the blade (step i). Even further, if the work is completed on one blade it may be decided to continue with servicing another blade (step j). Even further, if the work is completed on all blades in question it may be decided to lower the work platform to the ground (step k). Fig. 12 illustrates an embodiment of a control system 40 in connection with a work platform according to the invention In order to control and monitor the functionalities of the work platform, it is necessary with a control system positioned on the work platform e.g. inside the box containing cable winding m0eans. The control system is preferably a microprocessor- WO 2004/092577 PCT/DK2003/000257 29 based system capable of receiving, transmitting, processing and storing signals. The control system comprises connections to the different means of the work platform that needs controlling or monitoring. The connections of the work platform may be divided into different groups such as control cables 4la-41f ensuring that control signals are transferred to control valves, switches and relays and sensor cables returning monitor signal to the control system, said signals concerning the functionality of the different components. The control cables may be cables 41a controlling the functionality of the suction or vacuum cups 16a, 16b of the retaining means for a wind turbine blade. Further cables 41f may control the functionality of the suction or vacuum cups 15a, 15b of the gripping means. Other control cables 41b, 41 d may control the functionality of the cable winding mechanisms 43,44 for the inner and outer cables, respectively. Even further, control cables 41c may control the functionality of the hydraulic and/or pneumatic components of the box 10. More control cables (not illustrated on the figure) may control the status of the electric accumulators, the air containers, the diesel generator or further components of the work platform. The electric power cables may supply energy directly to mechanical means such as electric actuators converting the electricity to a physical change in position of the actuator rod e.g. the arm actuating means in the case they are electric driven. Further, the electricity may be supplied to pneumatic or hydraulic pumping means in which the pumping means supply pneumatic or hydraulic power to different actuating means such as the forcing means in the case they are pneumatic or hydraulic actuated. Even further, the suction or vacuum cups may be pneumatic supplied from one or more vacuum pumps, said pumps preferably being electrically driven. WO 2004/092577 PCT/DK2003/000257 30 The control cables connect the control systems with control switches and relays e.g. electric switches switching the electric power cables or hydraulic, pneumatic and vacuum pressure switches controlling the air or oil flow through the connection tubes. The monitoring cables may direct different status signals of the work platform to the control system such as the energy level of the accumulators, the pressure levels etc.. If status signals indicate that the normal functionality of the work platform is not possible, e.g. due to low energy level of electric accumulators, the worker may choose to lower the work platform with the aid of a manually operated handle releasing the break of the cable winding means. The break release is preferably only partly ensuring that the lowering speed of the work platform is below the abovementioned speed limit. However, if the speed increases beyond the limit, the over speed break will take effect and slow down or even stop the work platform. If it is possible the manual operation may be supplemented by the remaining electric energy of the accumulators e.g. allowing the electric control of some necessary components of the work platform such as the gripping means. Further, the control system may define a lower limit for the accumulators wherein any normal functionality of the work platform is stopped if the limit is exceeded. After the limit has been exceeded, the work platform may preferably only be lowered. The control system 40 may be wired or wirelessly connected to a remote control 42. The wireless connection is established by using electromagnetic airwaves such as radio or infrared waves. The remote control allows a worker to control the different components of the work platform e.g. movement of the horizontal forcing means, the activation of the suction or vacuum cups or the raising/lowering of the platform. Further, the remote control may comprise display means for monitoring the above-mentioned status signals of WO 2004/092577 PCT/DK2003/000257 31 the different components or other signals such as the position of the horizontal forcing means. Even further, the control means or the remote control may comprise sound generating means in order to inform the workers of the status of the work platform or one or more of the components of the platform. The remote control may be held by one of the workers positioned on the work platform, on the ground or even in the nacelle. The remote control that controls the control system may also control different components of the wind turbine. In an embodiment the remote control controls the means that turns the rotor in connection with the change of wind turbine blades at the work platform, e.g. the above-mentioned auxiliary device comprising an electric motor. Further, the remote control can control any winding mechanism in the nacelle. Even further, the remote controlling of the work platform may be divided between several remote controls e.g. held by a worker on the work platform and a worker on the ground or in the nacelle. The worker on the ground or in the nacelle may remotely activate different components of the wind turbine while the worker on the platform controls the platform components with his remote control. Preferably, the remote control held by the worker on the platform overrules any other remote control e.g. in a master/slave remote control configuration. The invention has been exemplified above with reference to specific examples. However, it should be understood that the invention is not limited to the particular examples described above but may be used in connection with a wide variety of applications. Further, it should be understood that especially the work platform according to the invention may be designed in a multitude of varieties within the scope of the invention as specified in the claims. WO 2004/092577 PCT/DK2003/000257 32 List 1. Wind turbine 2. Wind turbine tower 3. Wind turbine nacelle 4. Wind turbine hub 5. Wind turbine rotor 6. Work platform 7. 7a-7c. Cables; inner and outer cables 8. Gripping means 9. Truck with trailer for transportation of the work platform 10. Cable winding means 11 a, b. Blade docking areas 12. Cable guiding means 13. Guard rail defining a work area 14,14a, 14b. Steering wheel 15,15a, 15b. Holding means for the wind turbine tower 16a, 16b. First and second head of retaining means for the wind turbine blade 17a, 17b. First and second base of retaining means for the wind turbine blade 18. Foundation of the work platform 19a, 19b. Outer sections of holding arm 20a, 20b. Inner sections of holding arm 21 a, 21 b. Base sections of holding arm 22a, 22b Arm actuating means 23. Horizontal forcing means 23a, 23b. First and second horizontal forcing arm 24. Power means 25. Fixed part in the horizontal forcing means 26. Front of fixed part in the horizontal forcing means 27a, 27b. First and second suction or vacuum cups 28. Suction opening WO 2004/092577 PCT/DK2003/000257 33 29a, 29b. Connection openings 30. Connection tube 31. Connecting rod 32. Rubber rim or lips 33. Opening for cable entrance 34. Box containing cable winding means 35a, 35b. First and second box door 36. Electric accumulator means 37. Hydraulic pump and tank means 38. Hydraulic motor 39. Suction or vacuum pump means 40. Control means 41a to 41f. Connections such as control cables 42. Remote control 43. Outer cable winding system 44. Inner cable winding system 45. Anchorage point for cables at the nacelle WO 2004/092577 PCT/DK2003/000257 34 WE CLAIM : 1. A method for servicing the outer components of a wind turbine such as the wind turbine blades and the tower with a work platform, said method comprising the steps of: positioning the work platform at the wind turbine tower, connecting the work platform to an upper part of the wind turbine with at least one cable, raising the work platform with the cable and cable winding means to a position of use, . and holding the work platform to the side of the wind turbine tower by directly gripping the tower with holding means comprised in the work platform. 2. Method as claimed in claim 1, wherein said holding is established with at least two sets of suction or vacuum cups. 3. Method as claimed in claim 1, wherein said holding is established with at least two sets of electromagnetic means. 4. Method as claimed in claim 1, wherein said holding is established with retaining means surrounding said wind turbine tower. 5. Method as claimed in claim 2 or 3, wherein said holding is enhanced by positioning said suction or vacuum cups or electro magnetic means on the ends of holding arms, said arms gripping around the exterior of the wind turbine tower. WO 2004/092577 PCT/DK2003/000257 35 6. Method as claimed in any of the claims I to 5, wherein said method also comprises the step of moving the work platform horizontally by extending or retracting horizontal forcing means of the work platform. 7. Method as claimed in claim 6, wherein the extending or retracting is established telescopically by a number of arm sections in said horizontal forcing means. 8. Method as claimed in any of the claims I to 7, wherein cable guiding means angles the cable outwards in relation to the wind turbine tower from the starting point of the cable. 9. Method as claimed in any of the claims 1 to 8, wherein said work platform is moved up or down by following and rolling with steering wheels of the platform on the surface of the wind turbine tower. 10. A work platform (6) for approaching, to service, the outer components of a wind turbine such as the wind turbine blades (5) and the wind turbine tower (2), said platform comprising - at least one cable (7, 7a, 7b, 7c) connecting the work platform with an upper part of the wind turbine, and cable winding means (43, 44) winding said at least one cable, characterized in that said platform also comprises gripping means (8) for directly holding the work platform (6) to the tower (2). 11. Work platform as claimed in claim 10, wherein said at least one cable (7) comprises a number of outer cables (7a, 7b), said set comprising a main cable (7a) and one or more additional cables (7b). WO 2004/092577 PCT/DK2003/000257 36 12. Work platform as claimed in claim 10 or 11, wherein said at least one cable (7) also comprises an inner cable or cables (7c). 13. Work platform as claimed in claim 11 or 12, wherein said inner and outer cables (7a, 7b, 7c) are fixed to the underside of the wind turbine nacelle (3) at an inner and outer anchorage point (45) in a direction from the tower or to anchorage points inside the nacelle. 14. Work platform as claimed in any of the claims 10 to 13, wherein said gripping means (8). comprise at least two sets of suction or vacuum cups (15a, 15b). 15. Work platform as claimed in any of the claims 10 to 13, wherein said gripping means (8) comprise at least two sets of electromagnetic means. 16. Work platform as claimed in any of the claims 10 to 13, wherein said gripping means (8) comprise retaining means surrounding the wind turbine tower such as at least one retaining belt. 17. Work platform as claimed in claim 14 or 15, wherein each of said at least two sets of suction or vacuum cups (15a, 15b) or electromagnetic means are flexibly mounted to the end of a holding arm (19a, 20a, 21a; 19b, 20b, 21b respectively). 18. Work platform as claimed in claim 17, wherein said holding arm comprises a base arm section (21a, 21b), an inner arm section (20a, 20b) and an outer arm section (19a, 19b). 19. Work platform as claimed in claim 18, wherein said inner arm section (20a, 20b) and outer arm section (19a, 19b) are pivotally connected and controlled by arm actuating means (22a, 22b) in at least one direction. WO 2004/092577 PCT/DK2003/000257 37 20. Work platform as claimed in any of the claims 10 to 19, wherein said gripping means (8) comprises one or more steering wheels (14, 14a, 14b). 21. Work platform as claimed in any of the claims 10 to 20, wherein guardrails (13) and a foundation (18) define a work area of said platform. 22. Work platform as claimed in any of the claims 10 to 21, wherein said gripping means (8) and the foundation (18) are connected through horizontal forcing means (23). 23. Work platform as claimed in any of the claims 10 to 22, wherein said horizontal forcing means (23) comprise a plurality of horizontal forcing arms (23a, 23b). 24. Work platform as claimed in any of the claims 10 to 23, wherein said horizontal forcing arms (23a, 23b) are integrated into each other as part of telescopic forcing means. 25. Work platform as claimed in any of the claims 10 to 24, wherein the side or sides of said platform comprises one or more indentations (11, 11a, 11b) for receiving and docking one or more wind turbine blades (5). 26. Work platform as claimed in any of the claims 10 to 25, wherein said platform comprises retaining means (16a, 17a; 16b, 17b) for retaining the wind turbine blade (5) in one of said indentations (11, 11a, 11b). 27. Work platform as claimed in claim 26, wherein said retaining means (16a, 17a; 16b, 17b) comprises one or more suction or. vacuum cups (16a, 16b) positioned on one or more rods as base part (17a, 17b) for the retaining means. 28. Work platform as claimed in any of the claims 10 to 27, wherein said at least one cable (7, 7a, 7b, 7c) is controlled by cable guiding means (12) e.g. by one or more cable guidance wheels in said means. WO 2004/092577 PCT/DK2003/000257 38 29. Work platform as claimed in any of the claims 10 to 28, wherein the position of said cable guiding means (12) controls the angling of said at least one cable (7, 7a, 7b, 7c). 30. Work platform as claimed in any of the claims 10 to 29, wherein said cable guiding means (12) angles the cable outwards in relation to the wind turbine tower from the anchorage point of the cable e.g. in the event in which the horizontal forcing means is fully retracted. 31. Work platform as claimed in any of the claims 10 to 30, wherein said platform comprises control means (40), said means at least controlling said arm actuating means (22a, 22b), horizontal forcing means (23), said one or more suction or vacuum pumps (39) and/or said cable winding means (43,44). 32. Work platform as claimed in claim 31, wherein said control means (40) is connected wired or wirelessly to and controlled by at least one remote control (42). 33. Work platform as claimed in claim 31 or 32, wherein said control means (40) and auxiliary devices are controlled with more than one remote control, said controls working in a master and slave configuration. The invention relates to a method of servicing the outer components of a wind turbine such as the wind turbine blades and the tower with a work platform, said method comprises the steps of: positioning the work platform at the wind turbine tower and connecting the work platform to an upper part of the wind turbine with at least one cable. Further the method comprises the steps of raising the work platform with the cable and cable winding means to a position of use, and holding the work platform to the side of the wind turbine tower with holding means. The invention also relates to a work platform for servicing the outer components of a wind turbine.

Full Text

AS THE WIND TURBINE BLADES AND THE TOWER WITH A WORK PLATFORM AND
WORK PLATFORM THEREFOR
Background of the invention
The invention relates to a method of approaching, for servicing the outer components of
a wind turbine such as the wind turbine blades and the tower with a work platform and a
work platform therefor.
Description of the Related Art
Normally, wind turbines are erected in places in which the wind conditions are
advantageous e.g. in places with few obstacles blocking or altering the path of the wind.
This means that the wind turbines often are positioned in more or less remote places
with a poor infrastructure such as in terms of road quality.
This creates some problems in relation to the necessary maintenance of the outer
components of the wind turbines such as the wind turbine blades or the surface of the
wind turbine tower. The magnitude of the problems has accumulated significantly in
recent years with the increasing size of the wind turbines.
Previously, freestanding cranes or lifts have been used in connection with maintenance
or reparation of the outer components of the wind turbines. However, with the poor
infrastructure, the transportation of the cranes or lifts to the erection places of the wind
turbines is somewhat costly and time consuming.
In order to overcome the problem of transporting large and heavy equipment to the
erection places different solutions have been suggested.

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One has been using persons lowering them selves down the side of the wind turbine
tower or blades using ropes connected to the nacelle. However, the method naturally
requires experts in climbing and is somewhat restricted in the work possibilities on
the wind turbine and as such not a feasible solution to the problems of maintenance
or reparation of the outer components of the wind turbines.
Another has been the installation of a crane and a cable basket underneath the nacelle
of the wind turbine allowing the basket to be lowered down the side of the wind
turbine. However, the basket is difficult to position correctly and difficult to work
from due to its unstable nature.
One of the objects of the invention is to establish a method and system for wind
turbines without the above-mentioned disadvantage.
It is an object of the invention to create a method and system which allow one or
more workers to be positioned at any adjacent position outside the wind turbine such
as near one of the wind turbine blades without involving heavy equipment on the
ground.
Further, it is an object of the invention to create a method and system which allow
safe and stable conditions for the workers.
The invention
The invention relates to a method of servicing the outer components of a wind
turbine such as the wind turbine blades and the tower with a work platform, said
method comprises the steps of:
positioning the work platform at the wind turbine tower,

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connecting the work platform to an upper part of the wind turbine with at least one
cable,
raising the work platform with the cable and cable winding means to a position of
use, and
holding the work platform to the side of the wind turbine tower with holding means.
Hereby it is possible to establish a method that allows safe and stable conditions for
one or more workers performing service on the outer components of a wind turbine
such as the wind turbine blades and the tower.
In an aspect of the invention, said holding is established with at least two sets of
suction or vacuum cups, allowing an easily controllable but still firm hold on the
wind turbine tower.
In a further aspect of the invention, said holding is enhanced by positioning said
suction or vacuum cups on the ends of holding arms, said arms gripping around the
exterior of the wind turbine tower. Hereby it is possible to establish a grip around the
wind turbine tower, the grip being advantageous in absorbing and withstanding any
twists in the work platform.
In an even further aspect of the invention, said method further comprises the step of
moving the work platform horizontally by extracting or retracting horizontal forcing
means of the work platform. Hereby it is possible to position the work platform at
any adjacent position outside the wind turbine such as near one of the wind turbine
blades.
In another aspect of the invention, the extracting or retracting is established
telescopically by a number of arm sections in said horizontal forcing means. Hereby

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a preferred embodiment of the invention is achieved that is simple to construct and
control during use.
In a further aspect of the invention, cable guiding means angles the cable outwards in
relation to the wind turbine tower from the starting point of the cable. Hereby an
advantageous embodiment of the invention is achieved.
In an even further aspect of the invention, said work platform is moved up or down
by following and rolling with steering wheels of the platform on the surface of the
wind turbine tower. Hereby a further advantageous embodiment of the invention is
achieved.
The invention also relates to a work platform, said platform further comprises
gripping means for holding the work platform to the tower. Hereby it is possible to
establish an apparatus that allows safe and stable conditions for one or more workers
performing service on the outer components of a wind turbine such as the wind
turbine blades and the tower.
In an aspect of the invention, said at least one cable comprises a number of outer
cables, said set including a main cable and one or more additional cables.
In a further aspect of the invention, said at least one cable further comprises an inner
cable or cables.
The more than one cable may enhance the safety level of the work platform.
In an aspect of the invention, said inner and outer cables are fixed to the underside of
the wind turbine nacelle at an inner and outer anchorage point in direction from the
tower or to anchorage points inside the nacelle.

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In an aspect of the invention, said gripping means comprises at least two sets of
suction or vacuum cups. With two or more sets of suction or vacuum cups it is
possible to engage the wind turbine tower from more than one side e.g. from
opposite sides ensuring a more firm grip. However it shall be emphasized that the
gripping means may be established with just one set of suction or vacuum cups
engaging the tower in one position. The position is preferably in front of the work
platform ensuring a balance for the platform around the position.
The suction or vacuum cups may be used in connection with any type of wind
turbine tower such as towers made in metal or concrete.
In another aspect of the invention, said gripping means comprises at least two sets of
electromagnetic means. The electromagnetic means may be one or more
electromagnets in which the electric power supply for the magnets is controlled in
order to hold on to/let go of the metal surface of the tower.
In a further aspect of the invention, said gripping means comprises retaining means
surrounding the wind turbine tower such as at least one retaining belt or band. The
retaining means surround the tower totally or partly and are connected to the gripping
means in which the gripping means may tighten or release the retaining means in
order to hold the work platform at the position or to allow movement of the platform,
respectively. The belt or band is preferably made in iron or an iron alloy. Further, the
belt or band may be made in other materials such as a reinforced composite or woven
material.
In another aspect of the invention, each of said at least two sets of suction or vacuum
cups or electromagnetic means are flexibly mounted to the end of a holding arm.
With the flexible mounting of the cups or electromagnetic means an advantageous
possibility of adapting the holding arms to the more or less uneven surface of the
wind turbine tower is achieved. Further, with the flexible mounting the inclination of
the tower does not affect the functionality of the cups or electromagnetic means.

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In a further aspect of the invention, said holding arm includes a base arm section,
inner arm section and outer arm section. By the sectioning of the arms, an ability of
angling the arms individually is achieved in order to grip different sized wind turbine
towers.
In an even further aspect of the invention, said inner arm section and outer arm
section are pivotally connected and controlled by arm actuating means in at least one
direction. Hereby it is possible to adapt the arm sections to the inclination of the
tower in question regardless of the (small) size of the inclination.
In another aspect of the invention, said gripping means comprises one or more
steering wheels. With the steering wheels it is easy to vertically move and roll the
work platform to a given position of use. Further the steering wheels help controlling
the path that the work platform follows when it is moved up or down the surface of
the wind turbine tower.
In an aspect of the invention, guard rails and a foundation define a work area of said
platform. As modern wind turbines comprises a nacelle height of more than 50
meters the workers need protection from falling of the platform e.g. as a result of an
unexpected wind gust or the like.
In an aspect of the invention, said gripping means and the foundation are connected
through horizontal forcing means. With the ability of forcing or moving the work
platform horizontally, it is possible to work with different outer components of the
wind turbine regardless of their position in relation to the wind turbine tower.
Especially with modern wind turbines, in which the distance between the tower and
the wind turbine blades may be between 5 and 10 meters, the ability of moving the
work platform horizontally is advantageous.

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In an aspect of the invention, said horizontal forcing means includes a number of
horizontal forcing arms. With a number of arms, instead of one long arm, the forcing
means may be constructed with a smaller length.
In an aspect of the invention, said horizontal forcing arms are integrated into each
other as part of telescopic forcing means. With the telescopic adaptation the
necessary length may be obtained with a more compact construction of the forcing
means. Further, the telescopic forcing means ensures that the horizontal forcing of
the work platform is achieved with a linear approach of the forcing means.
In an aspect of the invention, the side or sides of said platform includes one or more
indentations for receiving and docking one or more wind turbine blades. The
receiving and docking of the blade in an indentation is especially important as the
indentation defines an area that at least partly surrounds the blade. The surrounding
ensures that the blade may be retained from different positions e.g. retraining the
leading or trailing edge together with both sides of the blade. Further, the workers
may approach and get close to both sides of the blade without dangerously leaning
out over the guide rails.
In a special embodiment the blade may enter the indentation and subsequently be
surrounded by the work platform, wherein the surrounding is achieved by closing a
pivotally connected section of the platform behind the blade. The section preferably
comprises the necessary guide rails allowing the workers to walk around the blade in
its full circumference.
It shall be emphasised that the blade may be docked at any position along the sides of
the work platform. The indentations are merely adapted for a safer docking by
allowing a better retaining of the blade.
In an aspect of the invention, said platform includes retaining means for retaining the
wind turbine blade in one of said indentations. The retaining means are important as

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8
they ensure that any movements in the blade is retained e.g. at a wind gust and thus
protect the workers from potential injuries during the work on the blade. As the blade
is positioned in an indentation the retaining means may attack from opposite side
against the surface of the blade ensuring a solid and continuing hold on the blade.
In an aspect of the invention, said retaining means includes one or more suction or
vacuum cups positioned on one or more rods as base part for the retaining means.
The hold by suction or vacuum cups ensures both the solid and continuing hold of
the blade and at the same time a gentle hold without any pressure marks on the blade.
In an aspect of the invention, said cable is controlled by cable guiding means e.g. by
one or more cable guidance wheels in said means. The abrasion of the cable may be
avoided and thus ensuring the security of the worker on the platform.
In an aspect of the invention, said cable guiding means controls the angling of the
cable. By controlling the angling of the cable, it is possible to achieve different
advantageous characteristics such as forcing the work platform against the tower. By
forcing the platform against the tower the necessary strength of the gripping means
may be reduced.
In an aspect of the invention, control means at least controls said arm actuating
means, horizontal forcing means, said one or more suction or vacuum pumps and/or
said cable winding means.
In another aspect of the invention, said control means is connected wired or
wirelessly to and controlled by at least one remote control. Equipped with a remote
control the worker may move more freely on the platform and control the
components of the platform more precisely and thus is both the flexibility and the
security of the platform enhanced.

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In a further aspect of the invention, said control means and auxiliary devices are
controlled with more than one remote control, said controls working in a master and
slave configuration. Hereby it is possible to control components of the work platform or
with the auxiliary devices components of the wind turbine, such as the turning of the
rotor, from different positions e.g. the work platform and the ground or the nacelle.
The invention will be described in the following with reference to the accompanying
drawings, in which
fig. 1. illustrates a large modem wind turbine,
fig.2a illustrates a work platform according to the invention
moving upwards on the side of a wind turbine tower,
fig. 2b illustrates the work platform in a use situation,
fig. 3 illustrates in more details the work platform on the side of a
wind turbine tower,
fig. 4 illustrates the positioning of a wind turbine blade in relation
to the work platiorm, the platform seen from below,
fig. 5 illustrates in perspective the work platform according to a
preferred embodiment of the invention,

WO 2004/092577 PCT/DK2003/000257
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fig. 6 illustrates the connection between the wind turbine and
the work platform including a section hereof,
figs. 7a and 7b illustrate the work platform in which the pushing actuator
means are in two different extraction positions;
figs. 8a to 8c illustrate different extraction positions of a preferred
embodiment of the pushing actuator means,
figs. 9a and 9b illustrate a preferred embodiment of suction or vacuum
cups according to the invention in front and rear views,
figs. 10a and 10b illustrate a preferred embodiment of cable winding means
including a box holding the cable winding means,
fig. 11 illustrates a flow diagram relating to a method of
servicing the outer components of a wind turbine, and
fig. 12 illustrates an embodiment of a control system in
connection with a work platform according to the
invention.
Detailed description
Fig. 1 illustrates a modern wind turbine 1 with a tower 2 and a wind turbine nacelle 3
positioned on top of the tower. The wind turbine rotor 5, comprising three wind
turbine blades, is connected to the nacelle through the low speed shaft which extends
out of the nacelle front.

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As illustrated in the figure, wind beyond a certain level will activate the rotor due to
the lift induced on the blades and allow it to rotate in a perpendicular direction to the
wind. The rotation movement is converted to electric power, which is usually
supplied to the transmission grid as known by skilled persons within the area.
Fig. 2a illustrates a work platform 6 according to the invention moving upwards on
the side of a wind turbine tower in connection with a maintenance or reparation job
on the wind turbine 1.
Further, it is illustrated that the wind turbine blades are pitched out of the wind
(parallel with the wind) and not moving as the wind turbine is stopped during the job.
The figure also illustrates that a worker is positioned inside the work platform.
i
The work platform is connected to the wind turbine nacelle 3 with at least one cable
7 in which the cables arrive at the nacelle from a position underneath the nacelle. The
work platform also comprises gripping means 8 that substantially horizontal reaches
out against the side of the wind turbine tower 2.
The cables 7 may be an integrated part of the wind turbine located inside the nacelle
and lowered to the ground through openings in the bottom of the nacelle. Further, the
cable may arrive together with the work platform 6 and be transported to the nacelle
e.g. by a worker carrying the cable to the nacelle using the stairs inside the wind
turbine, securely fastening one end of the cable to the nacelle and lowering the other
end down to the ground.
Another way would be to carry a thin rope to the nacelle and lower it down to the
ground, tie it to a cable end and drag the cable up to the nacelle on the outside of the
wind turbine tower e.g. with the aid of a lifter in the nacelle before securely fastening
the cable to the nacelle.

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After the cable has reached the ground or the nacelle, it is fastened to cable winding
means of the work platform allowing the work platform to be raised from the ground
by winding the cable on the work platform.
However, in a further embodiment the cable winding means may be positioned in the
nacelle and the cable thus only firmly secured to the work platform.
The accumulators may, in another embodiment of the work platform, be replaced or
supplemented with a diesel generator positioned on the work platform.
Finally, the figure illustrates that the work platform was transported to the place of
the wind turbine on a trailer connected to a truck 9 e.g. the normal service truck of
the company servicing wind turbines. The truck may include different tools or
machinery needed in connection with the maintenance and reparation job. Further,
the truck may be used in supplying power to the necessary electric accumulators or
air containers of the work platform e.g. during transportation by charging the
accumulators from the generator of the truck, or the containers from a compressor.
Fig. 2b illustrates the work platform in a use situation at the tip of a wind turbine
blade 5 in which the blade is ready for servicing by the worker on the platform.
In order to arrive at the position of fig. 2b from the position of fig. 2 a the work
platform is lifted with the cable winding means while steering wheels of the gripping
means 8 are forced against the wind turbine tower allowing the work platform to roll
over the surface of the tower during the displacement.
After arrival at the position of use the work platform is still connected to the nacelle
through the cables 7 but is also connected to the tower through the gripping means 8
which grippes the wind turbine tower 2 at least two positions (as will be explained in
further details below).

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The wind turbine blade is twisted to a position in which the worker has access to the
surface of the blade (the blade being in a position substantially perpendicular to the
wind at the figure). The wind turbine blade is also secured to the work platform in
order to avoid any unintended movement of the blade during the work process.
When the work is done at the position the gripping means 8 are released from the
tower and the cable winding means lifts (and rolls) the work platform to a new
position in which the gripping means 8 are once again secured to the tower. This may
be repeated until the blade in its full length has been serviced.
Hereafter the other wind turbine blades may undergo the same procedure. The blade
to undergo the procedure is rotated to meet the side of the work platform in which
the movement may be achieved by turning the high speed shaft linking the generator
and the gear in the nacelle e.g. by an auxiliary device comprising an electric motor.
Further, the movement may be achieved by using the generator as an electric motor
taking electric energy from the public electric grid. Even further, a movement may be
achieved by slightly and briefly pitching one or more blades into the wind.
Fig. 3 illustrates a preferred embodiment of the work platform 6 according to the
invention positioned on (and partly concealed by) the wind turbine tower 2.
The work platform is constructed with a foundation 18 surrounded by guard rails 13
in which the foundation and the guide rails defining a work area for the worker or
workers.
The work platform further comprises cable guiding means 12 guiding two cables 7a,
7b to cable winding means 43. The cable winding means 43 comprises motor and
gearing means in which the gearing means has a high gearing ratio e.g. 1500 motor
shaft rotations for each cable winding.

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The work platform further comprises a box 10 at the side wherein different hydraulic
and/or pneumatic components may be positioned (as will be explained in connection
with figs. 10a and 10b).
In a first embodiment the cable winding means 43 are positioned at the foot of the
cable guiding means 12 in which the winded cables 7 continue freely down under the
platform or even stay on the floor of the platform, hi another embodiment of the
invention the cables may be accumulated in a cable drum positioned inside the box
10 or another suitable place at the work platform.
The cable guiding means 12 comprises a number of guidance wheels that direct the
cables 7a, 7b to the cable winding means 43 and protect the cable from abrasion. The
cable guiding means is preferably positioned centrally on the platform or the outer
section of the platform in relation to the tower.
In a situation in which the horizontal forcing means is fully retracted, the cables are
vertical or preferably slightly angled to meet the cable guiding means. The angling of
the cable is outwardly in relation to the wind turbine tower from its anchorage point
of the wind turbine ensuring that the work platform, regardless of the degree of
extraction of the horizontal forcing means, is forced against the tower. The angling is
established with the positioning of the cable guiding means on the work platform and
the anchorage point.
In order to freely adapt the work platform to different anchorage points the point of
attack of the cable guiding means may be moved horizontally. As the point of attack
may be seen as the cable guidance wheels of the cable guiding means the movement
of the attack point may be achieved by moving the wheels. The moving may be
established by having sets of openings for holding the shafts of the cable guidance
wheels in which the sets are spaced apart.

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The work platform also comprises different docking areas lla, lib for a wind
turbine blade. The first docking areas lla are indentations on the opposite side of the
work platform in which the blade is allowed to enter one of the indentations with the
front or trailing edge facing the work platform. When the blade is positioned in the
indentation, retaining means from the work platform is forced against the sides of the
blade keeping the blade fixed in relation to the work platform.
With indentations on opposite side of the work platform it is possible to service wind
turbine blades from both sides of the platform but the work platform may also work
with just one first docking area lla. The first docking areas and further docking areas
are described in relation to fig. 4.
The figure further illustrates the one (non-concealed) half of the gripping means 8 of
the work platform. The gripping means includes an arm stretching out along the side
of the wind turbine tower. The arm fairly follows the surface of the wind turbine
tower by comprising a number of arm sections pivotally connected to each other. The
gripping means 8 comprises a steering wheel 14 approximately at half-length of the
arm, the wheel being forced against the surface of the tower 2. Further, at the end of
the gripping means 8, holding means 15 is positioned for holding onto the wind
turbine tower 2.
Fig. 4 illustrates the positioning of a wind turbine blade in relation to the work
platform, the platform seen from below.
The figure illustrates blades positioned in docking areas; on one side of the work
platform (solid line in the presentation a cross section of the blade) and on the
opposite side (dotted line). The blades are both docked with the leading or trailing
edge facing the side of the work platform and the diametrical line of the blades being
perpendicular to the longitudinal direction of the platform. The figure also illustrates
a situation in which the blade is docked parallel with the longitudinal direction of the
platform in a further indentation 1 lb (dotted line). The blade may be retained in the

WO 2004/092577 PCT/DK2003/000257
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further indentation by securing a strap around the blade and fixing the strap ends to
the guide rail.
The figure further illustrates the retaining means being forced against the sides of the
wind turbine blade. Each of the retaining means comprises a head and a base 16a,
17a; 16b, 17b, respectively. The retaining means may simply be rubber heads or
similar flexible members on rods forced against the sides and fastened to the work
platform ensuring that the blade is retained. However, the retaining heads may also
be suction or vacuum cups e.g. with connection to a vacuum pump.
Fig. 5 illustrates the preferred embodiment of the work platform in its entirety and in
perspective.
Especially the figure illustrates the gripping means 8 in its entirety with both holding
arms stretching out to grip the wind turbine tower at two positions with the holding
means 15a, 15b or to roll on the surface of the tower with the two steering wheels
14a, 14b.
As it is also seen on the figure each arm of the gripping means 8 comprises a base
arm section 21a, 21b connected to an inner arm section 20a, 20b, said inner arm is
connected to an outer arm section 19a, 19b. The base arm sections are further
connected to each other and the work platform through a base part comprising
horizontal forcing means 23.
The connection between the base and the inner arm sections is made rigid by a
sidepiece. The connection between the inner and the outer arm sections 19a, 20a;
19b, 20b is made variable by using a pivotal connection and arm actuating means
22a, 22b, such as linear electric, hydraulic or pneumatic actuators, allowing the outer
arm sections and especially the holding means 15a, 15b to be moved closer to or
further away from each other.

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Further, the figure illustrates another cable 7c extending toward the work platform
and entering at cable guidance means on the platform. The cable guidance means
directs the cable 7c to the cable winding mechanism 44 at the centre of the gripping
means 8.
Finally, the figure illustrates one of the retaining means 16b, 17b for retaining a wind
turbine blade in greater details.
The work platform, and especially the essential parts, such as the foundation of the
work platform 18, the horizontal forcing means 23 and/or the gripping means 8, are
preferably made in steel or steel alloys.
However, other metals may be used in the construction of the work platform such as
aluminium or aluminium alloys. Further different composite materials may be used
such as glass, aramid or carbon fibre materials.
The cables connecting the work platform with the upper part of the wind turbine are
preferably steel wires. Ropes such as a nylon rope may also be used if the strength of
the ropes is significant enough to hold the platform including the workers.
Fig. 6 illustrates the connection between the wind turbine and the work platform. The
connection comprises several cables 7 that extend from the nacelle 3 to different
positions on the work platform 6. The cables are divided in inner or outer cables in
which the terms "inner" and "outer" are to be understood as their position in relation
to the surface of the wind turbine tower.
In a preferred embodiment the inner and outer cables are connected to different
anchorage points on the underside of the nacelle. The points are positioned
somewhere between the wind turbine tower 3 and the wind turbine rotor 5 with the
inner point closer to the tower than the outer point e.g. 0.2 and 1.2 meter from the
tower, respectively.

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The inner and outer cables extend to an inner and an outer position at the work
platform in which they are connected to separate cable winding mechanisms 43, 44,
as explained in relation to figs. 3 and 4.
The enlarged section view further illustrates a preferred embodiment of the invention
and especially the extension of the inner 7c and outer cables 7a, 7b from the
underside of the nacelle.
The inner cable is illustrated as one cable 7c that extend from an inner anchorage
point to the inner position at the work platform with the inner cable winding
mechanism 44. The inner cable forms an angle a with the underside of the nacelle.
The angle is preferably 90 degrees, the cable extends vertically, or less than 90
degrees, the cable extends outwardly in relation to the tower from the anchorage
point.
The outer cables are illustrated as two cables 7a, 7b that extends from an outer
anchorage point 45 to the outer position at the work platform. As explained above,
the cable guiding means 12 is the outer position at the work platform that guides the
cables to the outer cable winding mechanism 43. The outer cables form an angle P
with the underside of the nacelle. The angle is preferably 90 degrees, the cables
extend vertically, or less than 90 degrees, the cables extend outwardly in relation to
the tower from the anchorage point.
The anchorage points may be eyelets or similar preinstalled connection points on the
underside of the nacelle. In order to get to the anchorage points, the nacelle may
comprise one or more small openings in the floor of the nacelle allowing a worker to
position the cable at the anchorage point. Alternatively, the cables may enter the
nacelle through openings and be fixed to anchorage points inside the nacelle.

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The function of the cables 7a, 7b, 7c is the moving of the work platform, i.e. lifting
or lowering the work platform. The inner cable ensures that the inner section of the
work platform, including the gripping means 8, is correctly moved regardless of the
conditions of the surface that the steering wheels 14 meet on the wind turbine tower.
The outer cables ensure that the work platform as such is moved and especially that
the outer section of the work platform is moved. The outer cables are divided into a
main cable and one or more additional cables for security reasons. The main cable
may single-handed carry the weight of the work platform but in case of a cable break
the additional cables will maintain the work platform at the position. Further, the
winding speed of the cables are monitored by safety means ensuring that the winding
speed does not exceed an upper limit such as 4 meters per minute. The safety limit
ensures that the work platform is not handled at dangerously high speeds, e.g. by the
worker, under normal conditions or at failure situations such as a breakdown in a
cable winding mechanism. The overspeed safety means is preferably
electro/mechanical devices of a centrifugal or a magnetic motion type that slows
down or temporarily stops the work platform. The safety means may also stop the
work platform in a situation of cable overwind or weight overload.
In order to keep the work platform horizontal or at least relatively horizontal, the
platform comprises level indication means. The level indication means may be a part
of the control system, described in relation with fig. 12, and as such be part of the
system generating control signals for the cable winding mechanisms ensuring the
horizontal position of the work platform. The level indication means may be
combined with tension means monitoring the tension on each of the different cables.
Both at vertical and horizontal movement of the work platform it is important to
monitor and ensure the horizontal position of the work platform, and it may be
achieved by controlling the cable winding mechanisms individually e.g. in order to
achieve the horizontal position and level the strain on the cables.

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In a basic embodiment of the invention the number of cables is set to just one cable
wherein the cable is extended to an outer position of the work platform such as the
cable guiding means 12.
Further, the cables may be fixed to the work platform and connected with cable
winding mechanisms in the nacelle.
Figs. 7a and 7b illustrate the work platform and especially the horizontal forcing
means 23 in two different positions.
Fig. 7a illustrates the first position in which the horizontal forcing means 23 is folly
retracted. The retraction of the horizontal forcing means 23 will position the work
platform close to the wind turbine tower, e.g. allowing inspection and repair of the
surface of the tower. Further, the position will be the normal position during truck
transportation of the work platform as well as the normal position during the initial
lifting of the work platform along the wind turbine tower.
Fig. 7b illustrates a second position in which the horizontal forcing means 23 is
partly extracted.
As seen on the figure, the horizontal forcing means 23 includes a number of
horizontal forcing arms. The arms may preferably be four-sided tubes in which the
tubes are telescopically integrated into each other. The tubes may be extracted or
retracted successively or individually by means of electric, hydraulic or pneumatic
means.
The electric means may include one or more electric motors driving one or more
spindles. The hydraulic or pneumatic means may include a piston driven by the
hydraulic or pneumatic forces.

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The extraction of the horizontal forcing means 23 will position the work platform
away from the wind turbine tower, e.g. allowing service of the surface of the wind
turbine blades.
As the distance between the wind turbine tower and the blades are quite significant at
modern wind turbines, the horizontal forcing means 23 should at full extraction be of
a certain length such as between 5 and 10 meters in order to be able to service any
type of modern wind turbine.
It should be understood that the term "horizontal forcing means" means that the
forcing means preferably acts in a substantially horizontal direction against the wind
turbine tower. However, the forcing means may in other embodiments be sloped to
an angle significantly above or below the horizontal direction.
Figs. 8a to 8c illustrate the structure of a preferred embodiment of the horizontal
forcing means 23.
The forcing means comprises a fixed part 25 holding the extractable and retractable
horizontal forcing arms 23a, 23b. The fixed part is normally mounted underneath the
foundation 18 of the work platform in its full length.
The dotted lines may be seen as the surface of the wind turbine tower or the holding
means 15 which the rest of the work platform is moved away from with the
extraction of the forcing means.
Fig. 8 a illustrates the structure in a retracted position for the horizontal forcing means
23.
Fig. 8b illustrates the structure in an extracted position for a first horizontal forcing
ami 23 a of the horizontal forcing means 23.

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Fig. 8c illustrates the structure in an extracted position for a first and second
horizontal forcing arm 23 a, 23b of the horizontal forcing means 23. The figure
illustrates the horizontal forcing means 23 with both arms in fully extracted
positions. However, in further embodiments the number of arms may be more than
two arms e.g. the use of three or four arms of a shorter length than the present two
Figs. 9a and 9b illustrate a preferred embodiment of the holding means 15 for the
wind turbine tower.
The holding means are preferably flexible mounted onto the ends of the outer arm
sections 19a, 19b of the gripping means 8. The flexibility may be used in order to
adapt the holding means to the slightly sloping surface of the wind turbine tower 2.
Further, the holding means comprises two substantially oval holding devices (and
rather long in an up-down direction) positioned next to each other. However, the
number of holding devices and their shapes may be altered in order to meet different
situations in which the present shape is preferred in order to advantageously absorb
vertical forces.
Fig. 9a illustrates the holding means 15 seen perceptively from the front. The holding
means comprises an oval first and second suction or vacuum cup 27a, 27b.
The second cup 27b includes a suction opening 28 in one end of the cup in which the
opening is connected to a suction pump with tube means. Further, the second cup
27b includes a connection opening 29b in the other end of the cup. The opening is
connected with a connection tube 30 to a connection opening 29a in the first suction
or vacuum cup 27a. The connection between the two suction or vacuum cups ensures
that a common pressure condition is established in the cups.
The suction or vacuum cups may include rubber rims or lips 32 in order to retain the
pressure condition inside the cups.

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The two suction or vacuum cups are rigidly fastened to a connecting rod 31. The
connecting rod 31 may on the other hand be flexibly fastened to the gripping means
as mentioned above e.g. with some sort of a tip-up hinge.
Fig. 9b illustrates the holding means 15 seen perceptively from the opposite side
after being rotated half a turn.
The figure especially illustrates the outlet of the suction opening 28 in which a tube,
with connection to a suction pump, is to be mounted.
The two suction or vacuum cups on each side of the gripping means may be used in
order to firmly engage the work platform to the wind turbine tower by applying a
very low suction pressure or even vacuum inside the cups facing the tower surface.
Together with the cable and the cable winding means the work platform may be held
in place by the gripping means.
Figs. 10a and 10b illustrates the hydraulic and/or pneumatic means positioned in a
box 34 at one side of the work platform.
Fig. 10a illustrates the box 34 with ventilation opening 33 in a first and second box
door 35a, 35b. The doors allow full access to the hydraulic and/or pneumatic means
inside the box.
Fig. 10b illustrates some of the content in the box including needle valves 36
controlling the hydraulic pump and tank 39 with the,motor 38. The magnetic
controlled needle valves 36 thus control the hydraulic fluid pumped to the horizontal
forcing means and other hydraulic actuated means of the work platform. The box
further comprises a vacuum pump 39 that supplies the different suction or vacuum
cups. The box may further comprise such means as electric accumulators and/or a

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diesel generator, a cable drum 37 in which the cables 7, 7a, 7b, 7c are accumulated
and one or more containers comprising compressed air.
The air containers may be used as an energy source supplying some or all the energy
consuming components of the work platform wherein the pressure of the containers
preferably are quite high such as up to 40 bar.
In an embodiment of the invention, compressed air is used instead of hydraulic
pressure in retracting/extracting the horizontal forcing means. Further, the
compressed air is used to drive the motors of the cable winding means in which the
normally used electric motors are replaced with pneumatic motors. Even further, the
compressed air is used to establish the necessary vacuum pressure for the suction or
vacuum cups. The containers may be reloaded with compressed air from a
compressor installed in the truck (as mentioned above) e.g. during the transportation
from one site of wind turbines to another. The remaining components such as the
control means may be supplied with electric power from one or more electric
accumulators.
The necessary energy may in another embodiment be supplied partly or totally from
the hydraulic system in which the hydraulic oil is pressurized with nitrogen supplied
from nitrogen containers.
Even further, in an embodiment the different components may be supplied with
electric power e.g. in order to drive the hydraulic and vacuum pumps in which the
electric power is supplied from the utility grid. An electric cable may connect the
work platform with a power outlet inside the wind turbine e.g. a 400 or 24 V AC
outlet. In another embodiment the cable connects the work platform with the
generator of the truck wherein the truck is kept running in order to supply the
necessary electric power without emptying the truck accumulators. The electric cable
may hang freely or be winded with a cable retraction mechanism.

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From the box the necessary air and/or hydraulic tubes extend, to the different
components that are supplied with suction or vacuum, pressurized air or hydraulic
oil. Further, electric power cables may transfer energy from electric accumulators, a
diesel generator or the utility grid to any electric actuated, activated or controlled
components.
Fig. 11 illustrates a flow diagram relating to a method of servicing the outer
components of a wind turbine.
The method may include some or all of the following steps of functionality in
servicing a wind turbine such as the wind turbine tower:
• driving the truck with the work platform to the rural place of the wind turbine
or wind turbine park.
• positioning the work platform in front of the wind turbine tower with the
steering wheels of the gripping means touching the surface of the tower (step
a of fig. 11).
• connecting a cable to the wind turbine nacelle as described above (step b -
part 1).
• connection of the cable to the cable winding means of the work platform in
which the cable preferably is a bit angled in relation to a vertical angle
forcing the work platform slightly against the tower (step b - part 2).
• vertically moving the work platform and one or more workers to a use
position with the aid of the cable, the cable guiding means and the cable
winding means (step c).

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• securing the work platform to the wind turbine tower by activating the
suction or vacuum cups 15 of the gripping means 8.
• work on the wind turbine tower e.g. checking and repainting areas of the
tower.
• releasing the holding means and lowering the work platform to the ground
and positioning the work platform on a transportation trailer (step f).
• recharging the electric accumulators during transportation of the work
platform to new rural places of wind turbines.
In connection with the servicing of the wind turbine tower, a number of choices may
be made including the decision regarding moving up or down when the work is
finished in an area of the tower (step e). If the work is completed on the tower the
work platform may be lowered to the ground.
The method may include some or all of the following steps of functionality in
servicing a wind turbine such as the wind turbine blades:
• driving the truck with the work platform to the rural place of the wind turbine
or wind turbine park.
• positioning the work platform in front of the wind turbine tower with the
steering wheels of the gripping means touching the surface of the tower (step
a of fig. 11).
• connecting a cable to the wind turbine nacelle as described above (step b -
part 1).

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• connection of the cable to the cable winding means of the work platform in
which the cable preferably is a bit angled in relation to a vertical angle
forcing the work platform slightly against the tower (step b - part 2).
o vertically moving the work platform and one or more workers to a use
position with the aid of the cable, the cable guiding means and the cable
winding means (step c).
• securing the work platform to the wind turbine tower by activating the
suction or vacuum cups 15 of the gripping means 8.
• altering the horizontal position of the work platform by extracting the
horizontal forcing means in order to meet a wind turbine blade (step g).
• retaining the wind turbine blade at the work platform, and servicing the
section of the blade within reach (step h).
• work on the wind turbine blade e.g. checking or cleaning areas of the blade.
• altering the horizontal position of the work platform by retracting the
horizontal forcing means e.g. allowing the wind turbine blades to turn briefly
before securing a new blade to the work platform and performing the service
process on this blade (step 1). The distance of the turn of the rotor is
preferably approximately one third of a full turn in order to position the new
blade in front of the blade docking area.
• moving the work platform to a new use position with the aid of the cable and
the cable winding means e.g. a higher position (step c).
o securing the work platform to the wind turbine tower by activating the
suction or vacuum cups 15 of the gripping means 8.

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o altering the horizontal position of the work platform by extracting the
horizontal forcing means in order to meet a wind turbine blade (step g).
o retaining the wind turbine blade at the work platform and servicing the
section of the blade within reach (step h).
... and so forth ...
• releasing the holding means and lowering the work platform to the ground
and positioning the work platform on a transportation trailer (step m).
• recharging the electric accumulators during transportation of the work
platform to new rural places of wind turbines.
In connection with the servicing of the wind turbine blades a number of choices may
be made including the decision regarding moving up or down when the work is
finished in an area of the blade (step i).
Even further, if the work is completed on one blade it may be decided to continue
with servicing another blade (step j).
Even further, if the work is completed on all blades in question it may be decided to
lower the work platform to the ground (step k).
Fig. 12 illustrates an embodiment of a control system 40 in connection with a work
platform according to the invention
In order to control and monitor the functionalities of the work platform, it is
necessary with a control system positioned on the work platform e.g. inside the box
containing cable winding m0eans. The control system is preferably a microprocessor-

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based system capable of receiving, transmitting, processing and storing signals. The
control system comprises connections to the different means of the work platform
that needs controlling or monitoring.
The connections of the work platform may be divided into different groups such as
control cables 4la-41f ensuring that control signals are transferred to control valves,
switches and relays and sensor cables returning monitor signal to the control system,
said signals concerning the functionality of the different components.
The control cables may be cables 41a controlling the functionality of the suction or
vacuum cups 16a, 16b of the retaining means for a wind turbine blade. Further cables
41f may control the functionality of the suction or vacuum cups 15a, 15b of the
gripping means.
Other control cables 41b, 41 d may control the functionality of the cable winding
mechanisms 43,44 for the inner and outer cables, respectively.
Even further, control cables 41c may control the functionality of the hydraulic and/or
pneumatic components of the box 10. More control cables (not illustrated on the
figure) may control the status of the electric accumulators, the air containers, the
diesel generator or further components of the work platform.
The electric power cables may supply energy directly to mechanical means such as
electric actuators converting the electricity to a physical change in position of the
actuator rod e.g. the arm actuating means in the case they are electric driven. Further,
the electricity may be supplied to pneumatic or hydraulic pumping means in which
the pumping means supply pneumatic or hydraulic power to different actuating
means such as the forcing means in the case they are pneumatic or hydraulic
actuated. Even further, the suction or vacuum cups may be pneumatic supplied from
one or more vacuum pumps, said pumps preferably being electrically driven.

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The control cables connect the control systems with control switches and relays e.g.
electric switches switching the electric power cables or hydraulic, pneumatic and
vacuum pressure switches controlling the air or oil flow through the connection
tubes.
The monitoring cables may direct different status signals of the work platform to the
control system such as the energy level of the accumulators, the pressure levels etc..
If status signals indicate that the normal functionality of the work platform is not
possible, e.g. due to low energy level of electric accumulators, the worker may
choose to lower the work platform with the aid of a manually operated handle
releasing the break of the cable winding means. The break release is preferably only
partly ensuring that the lowering speed of the work platform is below the
abovementioned speed limit. However, if the speed increases beyond the limit, the
over speed break will take effect and slow down or even stop the work platform.
If it is possible the manual operation may be supplemented by the remaining electric
energy of the accumulators e.g. allowing the electric control of some necessary
components of the work platform such as the gripping means. Further, the control
system may define a lower limit for the accumulators wherein any normal
functionality of the work platform is stopped if the limit is exceeded. After the limit
has been exceeded, the work platform may preferably only be lowered.
The control system 40 may be wired or wirelessly connected to a remote control 42.
The wireless connection is established by using electromagnetic airwaves such as
radio or infrared waves.
The remote control allows a worker to control the different components of the work
platform e.g. movement of the horizontal forcing means, the activation of the suction
or vacuum cups or the raising/lowering of the platform. Further, the remote control
may comprise display means for monitoring the above-mentioned status signals of

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the different components or other signals such as the position of the horizontal
forcing means. Even further, the control means or the remote control may comprise
sound generating means in order to inform the workers of the status of the work
platform or one or more of the components of the platform.
The remote control may be held by one of the workers positioned on the work
platform, on the ground or even in the nacelle.
The remote control that controls the control system may also control different
components of the wind turbine. In an embodiment the remote control controls the
means that turns the rotor in connection with the change of wind turbine blades at the
work platform, e.g. the above-mentioned auxiliary device comprising an electric
motor. Further, the remote control can control any winding mechanism in the nacelle.
Even further, the remote controlling of the work platform may be divided between
several remote controls e.g. held by a worker on the work platform and a worker on
the ground or in the nacelle. The worker on the ground or in the nacelle may
remotely activate different components of the wind turbine while the worker on the
platform controls the platform components with his remote control. Preferably, the
remote control held by the worker on the platform overrules any other remote control
e.g. in a master/slave remote control configuration.
The invention has been exemplified above with reference to specific examples.
However, it should be understood that the invention is not limited to the particular
examples described above but may be used in connection with a wide variety of
applications. Further, it should be understood that especially the work platform
according to the invention may be designed in a multitude of varieties within the
scope of the invention as specified in the claims.

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List
1. Wind turbine
2. Wind turbine tower
3. Wind turbine nacelle
4. Wind turbine hub
5. Wind turbine rotor
6. Work platform
7. 7a-7c. Cables; inner and outer cables
8. Gripping means
9. Truck with trailer for transportation of the work platform
10. Cable winding means
11 a, b. Blade docking areas
12. Cable guiding means
13. Guard rail defining a work area
14,14a, 14b. Steering wheel
15,15a, 15b. Holding means for the wind turbine tower
16a, 16b. First and second head of retaining means for the wind turbine blade
17a, 17b. First and second base of retaining means for the wind turbine blade
18. Foundation of the work platform
19a, 19b. Outer sections of holding arm
20a, 20b. Inner sections of holding arm
21 a, 21 b. Base sections of holding arm
22a, 22b Arm actuating means
23. Horizontal forcing means
23a, 23b. First and second horizontal forcing arm
24. Power means
25. Fixed part in the horizontal forcing means
26. Front of fixed part in the horizontal forcing means
27a, 27b. First and second suction or vacuum cups
28. Suction opening

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29a, 29b. Connection openings
30. Connection tube
31. Connecting rod
32. Rubber rim or lips
33. Opening for cable entrance
34. Box containing cable winding means
35a, 35b. First and second box door
36. Electric accumulator means
37. Hydraulic pump and tank means
38. Hydraulic motor

39. Suction or vacuum pump means
40. Control means
41a to 41f. Connections such as control cables
42. Remote control
43. Outer cable winding system
44. Inner cable winding system
45. Anchorage point for cables at the nacelle

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WE CLAIM :
1. A method for servicing the outer components of a wind turbine such as the wind
turbine blades and the tower with a work platform, said method comprising the steps of:
positioning the work platform at the wind turbine tower,
connecting the work platform to an upper part of the wind turbine with at least one cable,
raising the work platform with the cable and cable winding means to a position of use, .
and
holding the work platform to the side of the wind turbine tower by directly gripping the
tower with holding means comprised in the work platform.
2. Method as claimed in claim 1, wherein said holding is established with at least
two sets of suction or vacuum cups.
3. Method as claimed in claim 1, wherein said holding is established with at least
two sets of electromagnetic means.
4. Method as claimed in claim 1, wherein said holding is established with retaining
means surrounding said wind turbine tower.
5. Method as claimed in claim 2 or 3, wherein said holding is enhanced by
positioning said suction or vacuum cups or electro magnetic means on the ends of
holding arms, said arms gripping around the exterior of the wind turbine tower.

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6. Method as claimed in any of the claims I to 5, wherein said method also
comprises the step of moving the work platform horizontally by extending or retracting
horizontal forcing means of the work platform.
7. Method as claimed in claim 6, wherein the extending or retracting is established
telescopically by a number of arm sections in said horizontal forcing means.
8. Method as claimed in any of the claims I to 7, wherein cable guiding means
angles the cable outwards in relation to the wind turbine tower from the starting point of
the cable.
9. Method as claimed in any of the claims 1 to 8, wherein said work platform is
moved up or down by following and rolling with steering wheels of the platform on the
surface of the wind turbine tower.
10. A work platform (6) for approaching, to service, the outer components of a wind
turbine such as the wind turbine blades (5) and the wind turbine tower (2), said platform
comprising -
at least one cable (7, 7a, 7b, 7c) connecting the work platform with an upper part of the
wind turbine, and
cable winding means (43, 44) winding said at least one cable,
characterized in that said platform also comprises gripping means (8) for directly holding
the work platform (6) to the tower (2).
11. Work platform as claimed in claim 10, wherein said at least one cable (7)
comprises a number of outer cables (7a, 7b), said set comprising a main cable (7a) and
one or more additional cables (7b).

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12. Work platform as claimed in claim 10 or 11, wherein said at least one cable (7)
also comprises an inner cable or cables (7c).
13. Work platform as claimed in claim 11 or 12, wherein said inner and outer cables
(7a, 7b, 7c) are fixed to the underside of the wind turbine nacelle (3) at an inner and
outer anchorage point (45) in a direction from the tower or to anchorage points inside
the nacelle.
14. Work platform as claimed in any of the claims 10 to 13, wherein said gripping
means (8). comprise at least two sets of suction or vacuum cups (15a, 15b).
15. Work platform as claimed in any of the claims 10 to 13, wherein said gripping
means (8) comprise at least two sets of electromagnetic means.
16. Work platform as claimed in any of the claims 10 to 13, wherein said gripping
means (8) comprise retaining means surrounding the wind turbine tower such as at least
one retaining belt.
17. Work platform as claimed in claim 14 or 15, wherein each of said at least two
sets of suction or vacuum cups (15a, 15b) or electromagnetic means are flexibly
mounted to the end of a holding arm (19a, 20a, 21a; 19b, 20b, 21b respectively).
18. Work platform as claimed in claim 17, wherein said holding arm comprises a
base arm section (21a, 21b), an inner arm section (20a, 20b) and an outer arm section
(19a, 19b).
19. Work platform as claimed in claim 18, wherein said inner arm section (20a, 20b)
and outer arm section (19a, 19b) are pivotally connected and controlled by arm
actuating means (22a, 22b) in at least one direction.

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20. Work platform as claimed in any of the claims 10 to 19, wherein said gripping
means (8) comprises one or more steering wheels (14, 14a, 14b).
21. Work platform as claimed in any of the claims 10 to 20, wherein guardrails (13)
and a foundation (18) define a work area of said platform.
22. Work platform as claimed in any of the claims 10 to 21, wherein said gripping
means (8) and the foundation (18) are connected through horizontal forcing means (23).

23. Work platform as claimed in any of the claims 10 to 22, wherein said horizontal
forcing means (23) comprise a plurality of horizontal forcing arms (23a, 23b).
24. Work platform as claimed in any of the claims 10 to 23, wherein said horizontal
forcing arms (23a, 23b) are integrated into each other as part of telescopic forcing
means.
25. Work platform as claimed in any of the claims 10 to 24, wherein the side or sides
of said platform comprises one or more indentations (11, 11a, 11b) for receiving and
docking one or more wind turbine blades (5).
26. Work platform as claimed in any of the claims 10 to 25, wherein said platform
comprises retaining means (16a, 17a; 16b, 17b) for retaining the wind turbine blade (5)
in one of said indentations (11, 11a, 11b).
27. Work platform as claimed in claim 26, wherein said retaining means (16a, 17a;
16b, 17b) comprises one or more suction or. vacuum cups (16a, 16b) positioned on one
or more rods as base part (17a, 17b) for the retaining means.
28. Work platform as claimed in any of the claims 10 to 27, wherein said at least one
cable (7, 7a, 7b, 7c) is controlled by cable guiding means (12) e.g. by one or more cable
guidance wheels in said means.

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29. Work platform as claimed in any of the claims 10 to 28, wherein the position of
said cable guiding means (12) controls the angling of said at least one cable (7, 7a, 7b,
7c).
30. Work platform as claimed in any of the claims 10 to 29, wherein said cable
guiding means (12) angles the cable outwards in relation to the wind turbine tower from
the anchorage point of the cable e.g. in the event in which the horizontal forcing means
is fully retracted.
31. Work platform as claimed in any of the claims 10 to 30, wherein said platform
comprises control means (40), said means at least controlling said arm actuating means
(22a, 22b), horizontal forcing means (23), said one or more suction or vacuum pumps
(39) and/or said cable winding means (43,44).
32. Work platform as claimed in claim 31, wherein said control means (40) is
connected wired or wirelessly to and controlled by at least one remote control (42).
33. Work platform as claimed in claim 31 or 32, wherein said control means (40) and
auxiliary devices are controlled with more than one remote control, said controls working
in a master and slave configuration.

The invention relates to a method of servicing the outer components of a wind turbine such as the wind turbine blades and the tower with a work platform, said method comprises the steps of: positioning the work platform at the wind turbine tower and connecting the work platform to an upper part of the wind turbine with at least one cable. Further the method comprises the steps of raising the work platform with the cable and cable winding means to a position of use, and holding the work platform to the side of the wind turbine tower with holding means. The invention also relates to a work platform for servicing the outer components of a wind turbine.

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Patent Number

219335

Indian Patent Application Number

01882/KOLNP/2005

PG Journal Number

18/2008

Publication Date

02-May-2008

Grant Date

30-Apr-2008

Date of Filing

21-Sep-2005

Name of Patentee

VESTAS WIND SYSTEMS A/S

Applicant Address

SMED SORENSENS VEJ 5, DK-6950 RINGKOOBING, DENMARK

Inventors:

#	Inventor's Name	Inventor's Address
1	IVERSEN, PAUL	SANKI GERTRUDS VEJ 27, SIG, DK-6800 VARDE, DENMARK

PCT International Classification Number

F03D 1/00 A61Q 13/00

PCT International Application Number

PCT/DK2003/000257

PCT International Filing date

2003-04-15

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA