Title of Invention	CLAMPING APPARATUS COMPRISING A CLAMPING CHUCK AND A WORK PIECE CARRIER
Abstract	The clamping apparatus comprises a clamping chuck (1) and a work piece carrier (40), the chuck having a central opening (2) for receiving a clamping pin (30) attached to the work piece carrier (40), having a conical inserting portion (3), and the clamping pin having at least one surface portion (32) corresponding to the inserting portion (3), the clamping chuck also comprises a clamping mechanism (20) for clamping the clamping pin and the top of the clamping chuck having at least one surface portion (5, 6) serving as a Z-stop member, wherein, prior to activating the clamping mechanism, there is a gap between a flat bottom surface (41) of the work piece carrier and the surface portion (5, 6) of the chuck (1).

Title of Invention

CLAMPING APPARATUS COMPRISING A CLAMPING CHUCK AND A WORK PIECE CARRIER

Abstract

The clamping apparatus comprises a clamping chuck (1) and a work piece carrier (40), the chuck having a central opening (2) for receiving a clamping pin (30) attached to the work piece carrier (40), having a conical inserting portion (3), and the clamping pin having at least one surface portion (32) corresponding to the inserting portion (3), the clamping chuck also comprises a clamping mechanism (20) for clamping the clamping pin and the top of the clamping chuck having at least one surface portion (5, 6) serving as a Z-stop member, wherein, prior to activating the clamping mechanism, there is a gap between a flat bottom surface (41) of the work piece carrier and the surface portion (5, 6) of the chuck (1).

Full Text	The present invention relates to a clamping apparatus, comprising a clampinq chuck and a work piece carrier adapted to be releasably attached to the clamping chuck, having a flat bottom surface and comprising a clamping pin protruding from the flat bottom surface. The clamping chuck comprises a central opening with a conical inserting portion for receiving the clamping pin of the work piece carrier. The clamping pin comprises at least one surface portion corresponding in shape to the shape of the conical inserting portion of the central opening for aligning the position of the clamping pin in X- and/or in Y-direction. Moreover, the clamping chuck is provided with a clamping mechanism for fixing the clamping pin of the work piece carrier in the central opening, and at least one surface portion serving as a Z-direction stop member. Such a clamping apparatus is preferably used for clamping work piece carriers carrying one or several work pieces to be machined in the machining area of a machine tool in a well defined and predetermined position. Usually, the clamping chuck of the apparatus is fixed in the machining area of the machine tool, while the work piece carrier, provided with a clamping pin, is releasabiy attached to the clamping chuck. In order to be in a position to clamp work pieces with different dimensions, so-called palletizing systems are known which comprise a plurality of clamping chucks, usually two, four, six or eight of them. By means of these plurality of clamping chucks, a work piece carrier equipped with, depending on its size, two, four, six or eight clamping pins can be clamped. In certain cases, it may happen that the work piece ca+rrier is equipped with an odd number of clamping pins. Since an individual clamping chuck usually has neither means to avoid rotation nor means for determining the angular position of the clamping pin of the clamping pin around the Z-axis, it would be advantageous to provide one or a plurality of clamping chucks with positioning means, for determining, besides the X- and Y-positions, also the angular position around the Z-axis. With this arrangement, if appropriate, workpiece carriers having only one clamping pin also can be clamped to the clamping chuck in an exactly defined linear and angular position. !t is to be understood that in such a case also the work piece carrier has to be provided with positioning means cooperating with the above mentioned positioning means of the clamping chuck. A difficulty observed particularly in connection with large work piece carriers is that a required coarse aligning of the clamping pins of the work piece carrier with the corresponding openings in the clamping chucks is pretty difficult because there is only a small clearance between the front portion of the clamping pin and the opening in the clamping chuck adapted to receive the clamping pin. Moreover, there is a danger that both the clamping pin and the opening in the clamping chuck may be damaged. In addition to clamping apparatuses in which the clamping pin is provided with a cylindrical portion for its positioning within the opening of the clamping chuck, other clamping apparatuses are known in the art in which the clamping chuck is provided with a conical centering surface area for a clearance-free aligning of the clamping pin. For example the document EP 1,044,760 discloses a clamping apparatus of this kind. In this clamping apparatus, the clamping pin is aligned by means of a conical centering surface provided at the top of the opening of the clamping chuck. The housing wall of the clamping chuck is axially resilient in the region of this conical centering surface ; for this purpose, a radial cutout is provided behind the conical centering surface. Thereby, an elastically resilient area is created, which enables the clamp- ing pin to be axially moved and to be pulled in further in 2- direction after having been centered. ELastically resilient sur- face areas of this kind have shown to be efficient particularly in small clamping apparatuses. However, in the case of clamping appa- ratus adapted to receive large and heavy work piece carriers, the clamping chuck is lastingly weakened by the provision of such a cutout. Moreover, it is not possible to provide a Z-reference or a Z-direction stop member in the area around the above mentioned cutout since the clamping apparatus is too resilient in Z- directoin in that area. Finally, there is a danger that the elas- tically resilient area is damaged upon inserting the clamping pin into the clamping chuck because the eiastically resilient area cannot bear high loads neither in axial nor in radial directions. The document DE 41 10 857 discloses an apparatus for coupling a tool holder to a working spindle of a machine tool. The working spindle is provided with an opening for receiving a shaft portion of the tool holder. The opening has an upper and a lower conical portion with an annular recess having a supporting surface located between the two conical portions. The shaft portion of the tool holder is equipped with two cone rings supported by elastic abut- ments. Between the two cone rings, a locking mechanism is located, comprising two radially movable locking pieces. On the top, these locking pieces are provided with wedge shaped surface areas which rest in the locked state on the supporting surface of the annular recess. By providing the elastic abutments, the cone rings are axially movable relative to the shaft portion of the tool holder and enable the shaft portion to be pulled in into the opening af- ter the cone rings having been rested on the conical portions of the opening. The cone rings themselves are provided with slots. The shaft portion is provided with a flange portion constituting at its lower end a flat annular surface serving as a Z-direction stop member, resting on the front face of the working spindle upon clamping the shaft portion. In the opening of the working spindle, both conventional clamping pins (Fig. 5 of said document) and sectional clamping pins (Figs. 1 and 3 of said document) can be clamped. Thus, the basic idea of the invention may be seen in the fact that work piece carriers with differently designed clamping pins can be clamped by the working spindle of the machine tool. It is understood that such a clamping apparatus is not at all suitable for attaching a work piece holder to the working spindle of a machine tool in a highly precise and repeatable manner. U.S.Patent No. 5,722,806 discloses a coupling system that includes a male coupling having a cylindrical distal end including a recess that includes follower surfaces, a female coupling having a cylindrical interior for receiving the distal end of the male coupling, and a pair of opposing jaw members movably mounted within the interior and including external cam surfaces for engaging the follower surfaces of the male coupling when the jaw members are radially moved apart, and a drive train for radially and forcefully moving the jaw members apart. The drive train includes a wedging ball that freely floats in recesses between the opposing jaw members, and a drive rod for axially moving the wedging ball into and out of engagement with wedge surfaces located in the interior of the jaw members. The drive rod includes a distal end having a bore for slidably receiving the wedging ball. The freefloating of the wedging ball within the drive rod bore and between the internal surfaces of the jaw members allows it to apply uniform wedging forces to the jaw members when spreading them apart into a coupling position. U.S.Patent No. 5,918,870 discloses a device for detachable fastening of work pieces to be machined on a processing machine having a pallet on which the work pieces are detachably fastened, and which can be connected detachably via this pallet to the processing machine, wherein the locking between the pallet and one or more quick-clamp cylinders is effected through at east one pull-in bolt which are fastened on the pallet and which engage in clamping manner in corresponding receptacles on the quick-clamp cylinder, and wherein the clamping connection is maintained through tension springs, and for unlocking a hydraulic piston can be actuated which overcomes the clamping force of the tension springs, wherein in the quick-clamp cylinder the space between the central pull-in bolt and the tension springs arranged to the side of the latter is sealed. U.S.Patent No. 5,415,384 discloses an apparatus for clamping a work piece comprising a base and a work piece carrier adapted to be put onto and fixed to the base. The base and the carrier com- prise aligning means to align the position of the carrier relative to the base along three perpendicular coordinate axes as well as the angular position. The aligning means comprises first aligning element pairs in the form of cooperating reference surfaces at the carrier and the base, which define the position of the carrier in the Z-axis. The aligning means further comprises second and third aligning element pairs in the form of cooperating linear aligning element pairs, which define the position of the carrier in the X and Y-axes, respectively. The cooperating pairs each comprise a wedge-shaped centering member and a counterpart member with a matching centering slit. Clamping means is provided for clamping the carrier to the base in a well defined position which is de- fined by the aligning means. The clamping means comprises a plu- rality of clamping members, each including a pin member fixed to the carrier and a chuck member located in the base. The carrier comprises a flat surface which faces the base if the carrier is clamped to the base. The flat surface forms one of the reference surfaces. Each one member of the second and third pairs is di- rectly connected to the flat surface. Each pin member is also di- rectly connected to the flat surface. It is an object of the invention to provide a clamping appa- ratus with a clamping chuck and a work piece carrier releasably connected thereto whose clamping chuck is particularly suitable for palletizing systems, whereby the individual clamping chuck shall be very robust and rigid. It is a further object of the invention to provide a clamping apparatus with a clamping chuck and a work piece carrier releasably connected thereto in which the clamping pin is aligned in X- and/or Y-direction without any clearance. It is a still further object of the invention to provide a clamping apparatus with a clamping chuck and a work piece carrier releasably connected thereto in which a movement of the clamping pin and, thereby, the work piece carrier in Z- direction is possible after the clamping pin has been aligned in X- and/or Y- direction, without the need to provide separate elastically resilient means. In order to meet these and other objects, the present invention provides a clamping apparatus, comprising a clamping chuck, a work piece carrier adapted to be releasably connected to said clamping chuck, having a flat bottom surface and comprising a clamping pin, protruding from said flat bottom surface, said clamping chuck having a central opening for receiving said clamping pin of said work piece carrier and having a conical inserting portion, said clamping pin having at least one surface portion corresponding in shape to the shape of said conical inserting portion of said central opening for aligning the position of said clamping pin in X- and/or in Y-direction, and said clamping chuck also comprising a clamping mechanism for fixing said clamping pin of said work piece carrier in said central opening, and at least one surface portion serving as a Z-direction stop member, characterized in that said clamping pin is dimensioned such that, prior to activating said clamping mechanism, a gap exists between said flat bottom surface of said work piece carrier and said surface portion of said clamping chuck serving as a Z-direction stop member after said clamping pin of said work piece carrier is inserted into said central opening of said clamping chuck with said at least one surface portion of said clamping pin having engaging said conical inserting portion of said central opening and thereby aligning said clamping pin with reference to said clamping chuck in X- and/or Y- directions, whereby at least one of said clamping pin and the region around said central opening of said clamping chuck is adapted to be elastically deformed upon activation of said clamping mechanism to further pull in said clamping pin into said central opening and simultaneously said work piece carrier towards said surface portion of said clamping chuck serving as a Z-direction stop member until said flat bottom surface of said work piece carrier rests on said surface portion of said clamping chuck serving as a Z-direction stop member. Thus, the basic idea of the invention may be seen in the fact that the clamping pin is designed in such a way that it can align itself without clearance in X- and/or Y-direction upon insertion into the opening of the clamping chuck without the work piece carrier resting on the clamping chuck. In other words, during that aligning of the clamping pin, a small gap remains between the bottom surface of the work piece carrier and the top surface of the clamping chuck. This gap is removed when the clamping pin is further pulled in into the opening of the clamping chuck by means of the clamping mechanism, whereby the elasticity of the material of the clamping pin and/or of the region of the clamping chuck around the central opening is used for that purpose. Thereby, the work piece carrier is moved in Z-direction towards the clamping chuck until its flat bottom surface rests on the Z-direction stop member constituted by the corresponding surface areas on top of the clamping chuck. In this way, the provision of means that are elastically resilient in Z-direction can be totally avoided. In the following, an embodiment of the apparatus according to the invention will be further described, with reference to the accompanying drawings, in which: Fig. 1 shows a perspective view of a clamping chuck and of a work piece carrier; Fig. 2 shows a first longitudinal sectional view of the clamping chuck and of the work piece carrier; Fig. 3 shows a longitudinal sectional view of the clamping chuck with the work piece carrier loosely put on; Fig. 4 shows a longitudinal sectional view of the clamping chuck with the work piece carrier clamped thereto; Figs. 5 to 7 show perspective views of different embodiments of clamping pins; Fig. 8 shows a perspective view of a machining table and of a pallet; and Figs. 8a and 8b each show an enlarged view of clamping pins according to Fig. 8. Fig. 1 shows a perspective view of a schematically illustrated clamping apparatus. The clamping apparatus comprises a clamping chuck generally designated by reference numeral 1 and a work piece carrier generally designated by reference numeral 40. The work piece carrier 40 is provided with a clamping pin 30 by means of which the work piece carrier 40 can be fixed to the clamping chuck 1. Such a clamping apparatus is preferably and particularly used for exactly position-defined clamping of a work piece in the working area of a machine tool (not shown). Thereby, as it is the case in the present example, the work piece carrier 40 can simultaneously be the work piece itself. The bottom of the upper portion of the clamping chuck facing an actuating piston 10 preferably extends radially downwards from the centre. The clamping chuck 1, to be fixed to the machine tool by means known per se and not shown in the drawings, comprises a central opening 2 adapted to receive and fix the clamping pin 30 of the work piece carrier 40. The upper area of this opening 2 is designed as a conical inserting portion 3. The top surface of the clamping chuck 1 is provided with two annular surface portions 5, 6 located in concentric relationship to the central opening 2. The annular surface portions 5, 6 serve as Z-references for the work piece carrier 40, i.e. they define the height position of the work piece carrier 40 once the lower surface of the latter one rests on the surface portions 5, 6. As can be seen from Fig. 1, the inner annular surface portion 5 surrounds the opening 2 in a relatively small distance. The work piece carrier 40 comprises a flat lower surface 41 which constitutes a reference surface resting on the surface portions 5, 6 and, thereby, defining the height position, i.e. the Z-position of the work piece carrier 40 relative to the clamping chuck 1. The clamping chuck 1 is provided with a connec- tor 4 for supplying a hydraulic or pneumatic medium to the inte- rior of the clamping chuck 1 to lock and release, respectively, the clamping pin 30 of the work piece carrier 40, as will be ex- plained herein below in more detail. Fig. 2 shows a longitudinal sectional view of the clamping chuck 1 and the work piece carrier 40. The clamping chuck 1 com- prises a cup-shaped lower portion 8, an upper portion 9 connected to the lower portion 8 by means of screws 7, and a piston 10 sup- ported by means of (not shown) biased springs on the upper portion 9. The upper portion 9 is provided with a hollow cylindrical sleeve 12 projecting downwards from the upper portion 9. The inner wall of the sleeve 12 defines the opening 2 constituted by a cen- tral continuous cylindrical bore. The sleeve 12 and the upper por- tion 9 are designed as a one piece construction, whereby the sleeve 12 extends downwards into a circular recess 13 machined into the lower portion 8 of the clamping chuck 1. The upper end of the clamping pin 30 attached to the work piece carrier 40 is provided with a cylindrical reference surface portion 38 as well as with an annular reference surface portion 37. The annular reference surface portion 37 of the clamping pin 30 rests against the flat lower surface 41 of the work piece car- rier; thus, the lower surface 41 of the work piece carrier, serv- ing as a Z-reference, takes a well defined position with regard to the clamping pin 30. A clamping mechanism 20 for clamping the clamping pin 30 com- prises, besides the already mentioned piston 10 and the coil springs (not shown), a plurality of clamping balls 15. The clamp- ing balls 15 are received in radially extending bores 14 provided in the wall of the sleeve 12. In order to enable the piston 10 to be moved, against the bias force of the (not shown) springs, into the here shown upper end position, a pressure chamber 17 is pro- vided between the lower portion 8 of the clamping chuck 1 and the piston 10. The pressure chamber 17 can be hydraulically or pneu- matically pressurized. For clarity's sake, the gaskets required to seal the pressure chamber 17 have been omitted from the drawings. The clamping pin 30, attached to the work piece carrier 40 by means of a screw 31, comprises a truncated cone shaped portion 32 located at the front end of the clamping pin 30. The back side of the truncated cone shaped portion 32 forms a circumferential shoulder 33 on which the clamping balls 15 for pulling in and fix- ing the clamping pin 30 can rest. Preferably, the front edge 36 of the clamping pin 30 is rounded. In the region of its rear end, the clamping pin 30 comprises a further, truncated cone shaped portion 35. The amount of taper of both the front portion 32 and the rear portion 35 are adjusted to the amount of taper of the conical in- serting portion 3 of the central opening 2. However, the front portion 32 is designed such that its minimal outer diameter is appr. 5 to 10 mm less than the greatest diameter of the conical inserting portion 3 of the central opening 2 of the clamping chuck 1. In any case, the maximal diameter of the front portion 32 of the clamping pin 30 is greater than the minimal diameter of the rear portion 35 of the clamping pin 30. The result is that the front portion 32 of the clamping pin 30 provides for a course cen- tering of the clamping pin 30 in the central opening 2, while the rear portion 35 provides for a fine centering to exactly position- ally adjust the clamping pin 30 both in X- and in Y-directions. In order to enable the clamping balls 15 to be radially moved inwards into their operating position, the piston 10 is provided with an inclined pressure surface 18. This pressure surface 18 is designed such that the clamping balls 15 are self-lockingly held in their operating position once the piston 10 is in its locking position. Below the above mentioned pressure surface 18, the piston 10 is provided with an annular groove 19 into which the locking balls 15 can retract when the piston 10 is in its release position shown in Figs. 2 and 3. It is understood that the clamping pin 20 can be readily inserted into and removed from the central opening 2 of the clamping chuck 1 once the piston 10 is in its release position shown here. The upper portion 9 of the clamping chuck 1 comprises an inclined lower surface 21 and the piston comprises a correspondingly inclined upper portion 22. Together with the sleeve 12 extending up to the lower portion 8 of the clamping chuck 1, such a design results in a very rigid assembly by means of which very high pulling forces can be realized without any noticeable deformation of the upper portion 9 of the clamping chuck 1. Moreover, the one piece design of sleeve 12 and upper portion 9 of the clamping chuck 1 ensures that when very high pulling forces act on the work piece carrier 40 clamped to the clamping chuck 1, there is no danger of the work piece carrier 40 moving in axial direction, because it is not resilient in Z-direction, in contrast to clamping systems using a separate clamping ball cage. Furthermore, thanks to the continuous, one-piece design of the sleeve 12, the sealing of the pressure chamber 17 is simplified. Before the clamping pin 30 can be inserted into the central opening 2 of the clamping chuck 1, it has to be coarsely aligned to the opening 2. Thereafter, the work piece carrier can be lowered downwards onto the clamping chuck 1. Upon insertion, first, the clamping pin 30 is coarsely centered due to the fact that its front portion 32 engages the wall portion 3a of the conical inserting portion 3 of the central opening 2. Since the amount of taper of the front portion 32 is equal to the amount of taper of the inserting portion 3 of the central opening 2, and since the work piece carrier 40 is held in a horizontal position during insertion of the clamping pin 30 into the central opening 2, a line contact results between the front portion 32 of the clamping pin 30 and the wall 3a of the inserting portion 3 of the central opening 2. In the case of a line contact, the danger of damage to the clamping pin 30 and to the central opening 2, respectively, is much lower than in the case of a point contact. Upon continued insertion of the clamping pin 30 into the central bore 2 of. the clamping chuck 1, a fine centering of the clamping pin 30 in X- and Y- directions is accomplished under the influence of the rear truncated cone shaped portion 35 of the clamping pin 1. Thereby, the rear portion 35 of the clamping pin 30 rests completely on the wall 3a of the conical inserting portion of the central opening 2. The dimensioning of the clamping is so chosen that a gap S with a width of between 0.01 to 0.02 mm exists between the annular surface portions 5, 6, serving as a Z-reference, and the flat bottom surface 41 of the work piece carrier 40 after fine centering, but before clamping the work piece carrier 40 to the clamping chuck 1, i.e. when the work piece carrier 40 rests only with its mass on the clamping chuck 1, as shown in Fig. 3. It is to be understood that the gap S shown in Fig. 3 is greatly exaggerated for the sake of clarity. Referring to the clamping pin 30, this means that the reference surface portion 37 of the clamping pin 30, serving as a Z-reference of the clamping pin 30, towers above the annular surface portions 5, 6 by the above mentioned amount of between 0.01 and 0.02 mm, when the clamping pin 30 is loosely inserted, i.e. without any pulling force, into the central opening 2 of the clamping chuck 1. Depending on the design, the size and the dimensioning of the clamping apparatus, the above mentioned gap S can vary within wider limits, e.g. between 0.005 mm and 0.1 mm. It is to be understood that the lower surface of the work piece carrier 40 does not compellingly have to be flat, but that it can comprise different surfaces and/or planes. Important is only, the clamping apparatus still being in its released state, that a gap within the above mentioned limits exists between the coaxial surface portions 5, 6, serving as Z-stop members of the clamping chuck 1, and the surface areas of the work piece carrier 40 that are intended to rest on these surface portions 5, 6, such that the clamping pin 30 can align in X- and Y-directions without clearance to the inserting portion 3 of the central opening 2. Further, it is to be understood that the reference surface portion 37 of the clamping pin 30, constituting the Z- reference thereof, is not necessary to coincide with the bottom surface 41 of the work piece carrier 40, but it can, if appropriate, be recessed or protrude therefrom, depending on the design of the clamping pin 30 and/or the work piece carrier 40 and its bottom surface, respectively. Fig. 4 shows a longitudinal sectional view of the clamping chuck 1 with the work piece carrier 40 clamped onto it. In order to clamp the loosely inserted work piece carrier 40 to the clamping chuck 1, the pressure in the pressure chamber 17 is reduced, with the result that the piston 10 is pushed down into the position shown in Fig. 4 under the influence of coil springs 23, 25, as will be described in more detail herein after. Thereby, the clamping balls 15 are radially moved inwards, as is known in the art, where they rest on the shoulder 33 of the clamping pin 30, thereby puling the latter one downwards. When a high pulling force of up to 20 KN is exerted, the length of the clamping pin 30 is slightly increased, with a simultaneous decrease of its diameter, and the conical shaped inserting portion 3 of the central opening 2 is slightly widened. The result is that the clamping pin 30 is pulled into the central opening 2 somewhat deeper, with the work piece carrier 40 moving downwards in Z- direction until its flat bottom surface 41 rests on the surface portions 5, 6 of the clamping chuck 1, serving as Z-stops. Thus, the work piece carrier 40 is positioned not only in X- and Y- directions, but also in Z-direction. In other words: The alignment of the work piece carrier 40 with regard to the clamping chuck 1 in X- and Y- directions is accomplished without any clamping force acting on these two elements, while the movement of the work piece carrier 40 in Z-direction is accomplished exclusively by making use of the elasticity of the material of the clamping pin 30 and of the clamping chuck 1 in the region of its inserting portion 3 of the central opening 2. The elements of the clamping apparatus essential for the operation thereof are adjusted to each other, as far as dimensions and shape is concerned, in such a way that the reduction of the width of the gap S between the flat bottom surface 41 of the work piece carrier 40 and the surface portions 5, 6 of the clamping chuck 1 to zero, after the fine positioning of the clamping pin 30, and, therewith, the work piece carrier 40 in X- and Y-directions, is realized essentially exclusively with the help of the elasticity of the material of the clamping pin 30 as well as of the clamping chuck 1 in the region of the central opening 2. Thus, and in contrast to clamping apparatuses of the prior art, no members or elements that are elastically resilient in Z-direction have to be provided. From Fig. 4, showing a longitudinal sectional view of the clamping chuck 1 together with the work piece carrier 40 clamped thereto, particularly also the coil springs 23, 25 are evident, these springs being provided for biasing the piston 10 and responsible for the pulling force exerted on the clamping pin 30. For clarifying the design of the clamping chuck I, the left side of the drawing shows a sectional view taken through the coil springs of the clamping chuck I, while the right side shows a sectional view taken between adjacent coil springs of the clamping chuck 1. Depending on the required pulling force, both the number of coil springs and their spring force can be selected. For realizing very high pulling forces, twin springs can be provided as can be seen in the left side of Fig. 4, where two coil springs 23, 24 are arranged coaxially one in the other one. For compensating of torque forces that may be exerted to the upper portion 9 of the clamping chuck 1, the winding sense of diametrically opposite coil springs 23, 25 is different. Preferably, the clamping chuck 1 is provided with a plurality of coil springs evenly distributed along a circular path; for example, to reach high pulling forces, prac- tice has shown that a total of 16 coil springs should be used, i.e. 8 outer coil springs 23 and 8 inner coil springs 24. Moreover, the right side illustration in Fig. 4 shows that the clamping mechanism can take high pulling forces due to the one piece design of the sleeve 12 and the upper portion 9 of the clamping chuck 1, and due to the clamping balls 15 being received in the sleeve 12 essentially without clearance. In order to remove the work piece carrier 4 0 from the clamp- ing chuck 1, the piston 10 is pneumatically cr hydraulically moved upwards, against the force of the coil springs. Thereby, the clamping balls 15 are released with the result that they can move back into the groove 19, freeing the clamping pin 30 which now can be pulled upwards out of the central opening 2 of the clamping chuck 1. The clamping mechanism having been released, both the clamping pin 30 and the upper portion of the central opening 2 of the clamping chuck 1 revert to their original dimensions due to their elastic behavior. Figures 5 to 7 show three different embodiments of clamping pins 30, 30a and 30c, respectively, which are suitable to be used in combination with a large pallet comprising several clamping pins. The uppermost clamping pin 30 shown in Fig. 5 corresponds to the embodiment discussed already herein before; it comprises a surface portion 35 in the shape of a truncated cone for centering in X- and Y-directions and located at the rear end of the clamping pin 30. The clamping pin 30a shown in Fig. 6 comprises at its rear end, instead of a truncated cone shaped portion, two diametrically opposite surface portions 35a in the shape of a segment of a trun- cated cone. It is understood that only the frontal surface portion 35a can be seen in Fig. 6, while the rear one is hidden in this view. However, in Fig. 6a showing the clamping pin 30a in a side elevational view, both surface portions 35a are visible. By means of these surface portions 35a, the clamping pin 30a can be cen- tered by means of the conical inserting portion 3 of the central opening 2 (Fig. 1) in one direction only, preferably in X- direction or in Y-direction. In order to enable the clamping pin 30a and its surface portions 35a, respectively, to be properly aligned upon attaching it to the work piece carrier 40, the clamp- ing pin 30a is provided with two diametrically opposite flattened portions 39, adapted to be engaged by a wrench or similar tool. The lowermost clamping pin 30c according to Fig. 7 is provided at its rear end with a surface portion 35c having the shape of a truncated cone. However, that surface portion 35c has an outer di- ameter about 0.1 to 0.2 mm smaller than the outer diameter of the surface portion 35 of the clamping pin 30 according to Fig. 5. Thus, the clamping pin 30c acts as a simple clamping element with- out any centering and positioning function. The clamping apparatus being in its clamped state, i.e. if the flat bottom surface of the work piece carrier rests on the Z-reference surface portions of the clamping chuck, a gap in the region of 0.1 to 0.2 mm exists between the truncated cone shaped portion 35c of the clamping pin 30c according to Fig. 7 and the conical inserting portion 3 of the central opening 2 of the clamping chuck 1 (Fig. 1). Instead of being provided with a truncated cone shaped por- tion 35, the clamping pin 30 according to Fig. 5 could be equipped with four surface portions 35a in the shape of a segment of a truncated cone, evenly distributed along the rear periphery of the clamping pin 30, for aligning it in X- and Y-directions. Fig. 8 shows a perspective view of a machining table 42 equipped with four clamping chucks 1, la, lb and lc, as well as of a work piece carrier 43, called a pallet in the following, equipped with four clamping pins 30, 30a, 30b and 30c. Out of the four clamping pins 30, 30a, 30b and 30c, the frontmost clamping pin 30 corresponds to the one shown in Fig. 5, provided with a truncated cone shaped portion 35 for centering the pin 30 in X- and Y-directions. This clamping pin 30 sets the origin once the pallet 43 having been clamped to the machining table 42. The two lateral clamping pins 30a and 30b are designed according to the embodiment shown in Fig. 6, each comprising two diametrically op- posite surface portions 35a and 35b, respectively, in the shape of a segment of a truncated cone, whereby again only the frontal sur- face portions 35a and 35b, respectively, are visible. The rearmost clamping pin 30c, finally, corresponds to the embodiment according to Fig. 7 and acts only as a clamping member without any centering or positioning functions for clamping the pallet 43 to the machin- ing table 42. Fig. 8a shows an enlarged view of the right clamping pin 30a, and Fig. 8b shows an enlarged view of the left clamping pin 30b. These two clamping pins serve for determining the angular position of the pallet 43 around the origin defined by the clamping pin 30. Thereby, the surface portions 35a of the right clamping pin 30a align the pallet 43 in Y-direction, while the surface portions 35b of the left clamping pin 30b align the pallet 43 in X-direction. As mentioned before, the rearmost; clamping pin 30c serves only for clamping the pallet 43 in Z-direction. Even if two clamping pins 30a, 30b are provided in this em- bodiment for determining the angular position of the pallet 43 around the origin, it could be sufficient to provide only one clamping pin for this purpose. However, the design and arrangement of the clamping pins shown in Fig. 8 and discussed herein before has the advantage that no geometric over-determination of the po- sition of the pallet upon clamping occurs, because thermal dimen- sion changes of the pallet are compensated for by the correspond- ing clamping pins. Tests carried out on this subject have shown that the surface portions 35a of a clamping pin 30a designed ac- cording to the embodiment of Fig. 6 can equalize thermally caused expansions or dimensional deviations of the pallet 43 up to as much as 0.1 to 0.2 mm. Besides the clamping chucks 1 discussed herein before which per se do not comprise any means for determining the angular posi- tion around the Z-axis of the work piece carrier, other clamping chucks could be provided which do comprise means for determining not only the position in X- and Y-directions, but also the angular position around the Z-axis, with the result that, if appropriate, a work piece carrier having only one clamping pin can be clamped "to the clamping chuck both in a desired linear and angular posi- tions. It is understood that, in such a case, the work piece car- rier would be provided with suitable positioning means, whereby the clamping pin serves only for a coarse positioning of the work piece carrier, but not for a fine positioning. Then, the clamping pin would have the design as shown in Fig. 7 and discussed in con- nection therewith. WE CLAIM : 1. A clamping apparatus comprising a clamping chuck and a work piece carrier adapted to be releasably connected to said clamping chuck, having a flat bottom surface and comprising a clamping pin, protruding from said flat bottom surface, said clamping chuck having a central opening for receiving said clamping pin of said work piece carrier and having a conical inserting portion, said clamping pin having at least one surface portion corresponding in shape to the shape of said conical inserting portion of said central opening for aligning the position of said clamping pin in X- and/or in Y -direction, and said clamping chuck also comprising a clamping mechanism for fixing said clamping pin of said work piece carrier in said central opening, and at least one surface portion serving as a Z-direction stop member, characterized in that said clamping pin is dimensioned such that, prior to activating said clamping mechanism, a gap exists between said flat bottom surface of said work piece carrier and said surface portion of said clamping chuck serving as a Z-direction stop member after said clamping pin of said work piece carrier is inserted into said central opening of said clamping chuck with said at least one surface portion of said clamping pin engaging said conical inserting portion of said central opening and thereby aligning said clamping pin with reference to said clamping chuck in X- and/or Y- directions, whereby at least one of said clamping pin and the region around said central opening of said clamping chuck is adapted to be elastically deformed upon activation of said clamping mechanism to further pull in said clamping pin into said central opening and simultaneously said work piece carrier towards said surface portion of said clamping chuck serving as a Z-direction stop member until said flat bottom surface of said work piece carrier rests on said surface portion of said clamping chuck serving as a Z-direction stop member. 2. Clamping apparatus as claimed in claim 1, wherein said gap between said flat bottom surface of said work piece carrier and said surface portion of said clamping chuck serving as a Z-direction stop member has a width of 0.005mm to 0.1mm. 3. Clamping apparatus as claimed in claim 1, wherein said clamping pin has a surface portion constituting a Z-reference which protrudes above said surface portion of said clamping chuck serving as a Z-direction stop member by an amount of 0.005m to 0.1mm after said clamping pin is aligned in X- and / or Y- direction. 4. Clamping apparatus as claimed in claim 1, wherein said clamping pin has a front surface portion serving as a coarse centering portion and a rear surface portion serving as a fine centering portion. 5. Clamping apparatus as claimed in claim 4, wherein said front surface portion of said clamping pin has the shape of a truncated cone. 6. Clamping apparatus as claimed in claim claim 4, wherein said rear surface portion of said clamping pin has the shape of a truncated cone surface adapted to align the position of the clamping pin in X- and Y-directions in cooperation with said conical inserting portion of said central opening of said clamping chuck. 7. Clamping apparatus as claimed in claim 4, wherein the maximal diameter of said front surface portion of said clamping pin is greater than the minimal diameter of said rear surface portion of said clamping pin. 8. Clamping apparatus as claimed in claim 4, wherein the rear portion of said clamping pin has two diametrically opposite surface portions adapted to align said clamping pin in X- or Y-direction. 9. Clamping apparatus as claimed in claim 4, wherein the rear portion of said clamping pin has four surface portions evenly distributed along the periphery of said clamping pin and adapted to align said clamping pin in X- and Y-direction. 10. Clamping apparatus as claimed in claim 8 or 9, wherein said rear surface portions have the shape of a segment of a truncated cone. 11. Clamping apparatus as claimed in claim 1, wherein said central opening of said clamping chuck is designed as a continuous smooth bore. 12. Clamping apparatus as claimed in claim 5, wherein the minimal outer diameter of said front, truncated cone shaped surface portion of said clamping pin is between 3 to 15mm smaller than the maximal diameter of said conical inserting portion of said central bore of said clamping chuck. 13. Clamping apparatus as claimed in claim 5, wherein the taper of said front surface portion of said clamping pin corresponds to the taper of said conical inserting portion of said central bore of said clamping chuck. 14. Clamping apparatus as claimed in claim 1, wherein said clamping pin has a circumferential shoulder; and said clamping mechanism comprises a plurality of clamping balls as well as an actuating piston which is movable, for radially moving the clamping balls, from a release position into a clamping position in which said clamping balls engage said circumferential shoulder of said clamping pin. 15. Clamping apparatus as claimed in claim 14, wherein said actuating piston is axially movable and is received between an upper portion of said clamping chuck and a lower portion of said clamping chuck; and said actuating piston is biased by means of springs resting on said upper portion of said clamping chuck towards said lower portion of said clamping chuck. 16. Clamping apparatus as claimed in claim 14, wherein said actuating piston is pneumatically or hydraulically movable, against the biasing force of said springs, from a clamping position to a release position. 17. Clamping apparatus as claimed in claim 15 or 16, wherein said upper portion of said clamping chuck comprises a hollow cylindrical sleeve member whose interior constitutes said central opening in said clamping chuck adapted to receive said clamping pin and which is provided with radially extending bores adapted to receive said clamping balls. 18. Clamping apparatus as claimed in claim 17, wherein said hollow cylindrical sleeve member extends up to said lower portion of said clamping chuck. 19. Clamping apparatus as claimed in claim 15, wherein at least two diametrically opposite helical springs are provided for biasing said actuating piston, the winding direction of opposite helical springs being different. 20. Clamping apparatus as claimed in claim 19, wherein in each case the two helical coils are coaxially arranged. 21. Clamping apparatus as claimed in claim 15, wherein the bottom of the upper portion of the clamping chuck facing said actuating piston extends from the center radially downwards. 22. A clamping apparatus comprising at least two clamping chucks and a work piece carrier adapted to be releasably connected to said clamping chucks, having a flat bottom surface and comprising a plurality of clamping pins protruding from said flat bottom surface, said clamping chucks each having a central opening for receiving one of said clamping pins of said work piece carrier, said central opening having a conical inserting portion, wherein one of said clamping pins has a surface portion corresponding in shape to the shape of said conical inserting portion of said central opening for aligning the position of said clamping pin in X- and in Y-direction, and wherein at least another one of said clamping pins has a surface portion having a shape for aligning the position of said clamping pin only in X- or only in Y-direction, and each of said clamping chucks also comprising a clamping mechanism for fixing one of said clamping pins of said work piece carrier in said central opening, and at least one surface portion serving as a Z-direction stop member, characterized in that each of said clamping pins is dimensioned such that, prior to activating said clamping mechanism, a gap exists between said flat bottom surface of said work piece carrier and said surface portion of said clamping chuck serving as a Z-direction stop member after a clamping pin of the workpiece carrier is inserted into the central opening of the corresponding clamping chuck with said surface portion of a clamping pin engaging said conical inserting portion of said central opening and thereby aligning the clamping pin with reference to the corresponding clamping chuck in X- and/or Y-directions, wherein at least one of the clamping pin and the region around the central opening of the clamping chuck is adapted to be elastically deformed upon activation of said clamping mechanisms to further pull in the clamping pins into the central opening and simultaneously said work piece carrier towards said surface portions of said clamping chucks serving as a Z-direction stop member until said flat bottom surface of said work piece carrier rests on said surface portions of said clamping chucks serving as a Z-direction stop members. 23. Clamping apparatus as claimed in claim 22, wherein said at least another one of said clamping pins is adapted to align the work piece carrier only in X- direction or only in Y- direction ; and a rear portion of said at least another one of said clamping pins is provided with two diametrically opposite surface portions. 24. A clamping apparatus comprising a clamping chuck and a work piece carrier, substantially as herein described, particularly with reference to the accompanying drawings. The clamping apparatus comprises a clamping chuck (1) and a work piece carrier (40), the chuck having a central opening (2) for receiving a clamping pin (30) attached to the work piece carrier (40), having a conical inserting portion (3), and the clamping pin having at least one surface portion (32) corresponding to the inserting portion (3), the clamping chuck also comprises a clamping mechanism (20) for clamping the clamping pin and the top of the clamping chuck having at least one surface portion (5, 6) serving as a Z-stop member, wherein, prior to activating the clamping mechanism, there is a gap between a flat bottom surface (41) of the work piece carrier and the surface portion (5, 6) of the chuck (1).

Full Text

The present invention relates to a clamping apparatus, comprising a
clampinq chuck and a work piece carrier adapted to be releasably attached to
the clamping chuck, having a flat bottom surface and comprising a clamping pin
protruding from the flat bottom surface. The clamping chuck comprises a central
opening with a conical inserting portion for receiving the clamping pin of the work
piece carrier. The clamping pin comprises at least one surface portion
corresponding in shape to the shape of the conical inserting portion of the central
opening for aligning the position of the clamping pin in X- and/or in Y-direction.
Moreover, the clamping chuck is provided with a clamping mechanism for fixing
the clamping pin of the work piece carrier in the central opening, and at least one
surface portion serving as a Z-direction stop member.
Such a clamping apparatus is preferably used for clamping work piece
carriers carrying one or several work pieces to be machined in the machining
area of a machine tool in a well defined and predetermined position. Usually, the
clamping chuck of the apparatus is fixed in the machining area of the machine
tool, while the work piece carrier, provided with a clamping pin, is releasabiy
attached to the clamping chuck.
In order to be in a position to clamp work pieces with different dimensions,
so-called palletizing systems are known which comprise a plurality of clamping
chucks, usually two, four, six or eight of them. By means of these plurality of
clamping chucks, a work piece carrier equipped with, depending on its size, two,
four, six or eight clamping pins can be clamped. In certain cases, it may happen
that the work piece ca+rrier is equipped with an odd number of clamping pins.
Since an individual clamping chuck usually has neither means to avoid rotation
nor means for determining the angular position of the clamping pin of the
clamping pin around the Z-axis, it would be advantageous to provide one or a
plurality of clamping chucks with positioning means, for determining, besides the
X- and Y-positions, also the angular position around the Z-axis. With this
arrangement, if appropriate, workpiece carriers having only one clamping pin
also can be clamped to the clamping chuck in an exactly defined linear and
angular position. !t is to be understood that in such a case also the work piece
carrier has to be provided with positioning means cooperating with the above
mentioned positioning means of the clamping chuck.
A difficulty observed particularly in connection with large work piece
carriers is that a required coarse aligning of the clamping pins of the work piece
carrier with the corresponding openings in the clamping chucks is pretty difficult
because there is only a small clearance between the front portion of the
clamping pin and the opening in the clamping chuck adapted to receive the
clamping pin. Moreover, there is a danger that both the clamping pin and the
opening in the clamping chuck may be damaged.
In addition to clamping apparatuses in which the clamping pin is provided
with a cylindrical portion for its positioning within the opening of the clamping
chuck, other clamping apparatuses are known in the art in which the clamping
chuck is provided with a conical centering surface area for a clearance-free
aligning of the clamping pin.
For example the document EP 1,044,760 discloses a clamping apparatus
of this kind. In this clamping apparatus, the clamping pin is aligned by means
of a conical centering surface provided at the top of the opening of the clamping
chuck. The housing wall of the clamping chuck is axially resilient in the region of
this conical centering surface ; for this purpose, a radial cutout is provided
behind the conical centering surface. Thereby, an elastically resilient area is
created, which enables the clamp-
ing pin to be axially moved and to be pulled in further in 2-
direction after having been centered. ELastically resilient sur-
face areas of this kind have shown to be efficient particularly in
small clamping apparatuses. However, in the case of clamping appa-
ratus adapted to receive large and heavy work piece carriers, the
clamping chuck is lastingly weakened by the provision of such a
cutout. Moreover, it is not possible to provide a Z-reference or a
Z-direction stop member in the area around the above mentioned
cutout since the clamping apparatus is too resilient in Z-
directoin in that area. Finally, there is a danger that the elas-
tically resilient area is damaged upon inserting the clamping pin
into the clamping chuck because the eiastically resilient area
cannot bear high loads neither in axial nor in radial directions.
The document DE 41 10 857 discloses an apparatus for coupling
a tool holder to a working spindle of a machine tool. The working
spindle is provided with an opening for receiving a shaft portion
of the tool holder. The opening has an upper and a lower conical
portion with an annular recess having a supporting surface located
between the two conical portions. The shaft portion of the tool
holder is equipped with two cone rings supported by elastic abut-
ments. Between the two cone rings, a locking mechanism is located,
comprising two radially movable locking pieces. On the top, these
locking pieces are provided with wedge shaped surface areas which
rest in the locked state on the supporting surface of the annular
recess. By providing the elastic abutments, the cone rings are
axially movable relative to the shaft portion of the tool holder
and enable the shaft portion to be pulled in into the opening af-
ter the cone rings having been rested on the conical portions of
the opening. The cone rings themselves are provided with slots.
The shaft portion is provided with a flange portion constituting
at its lower end a flat annular surface serving as a Z-direction
stop member, resting on the front face of the working spindle upon
clamping the shaft portion. In the opening of the working spindle,
both conventional clamping pins (Fig. 5 of said document) and sectional
clamping pins (Figs. 1 and 3 of said document) can be clamped. Thus, the basic
idea of the invention may be seen in the fact that work piece carriers with
differently designed clamping pins can be clamped by the working spindle of the
machine tool. It is understood that such a clamping apparatus is not at all
suitable for attaching a work piece holder to the working spindle of a machine
tool in a highly precise and repeatable manner.
U.S.Patent No. 5,722,806 discloses a coupling system that includes a
male coupling having a cylindrical distal end including a recess that includes
follower surfaces, a female coupling having a cylindrical interior for receiving the
distal end of the male coupling, and a pair of opposing jaw members movably
mounted within the interior and including external cam surfaces for engaging the
follower surfaces of the male coupling when the jaw members are radially moved
apart, and a drive train for radially and forcefully moving the jaw members apart.
The drive train includes a wedging ball that freely floats in recesses between the
opposing jaw members, and a drive rod for axially moving the wedging ball into
and out of engagement with wedge surfaces located in the interior of the jaw
members. The drive rod includes a distal end having a bore for slidably receiving
the wedging ball. The freefloating of the wedging ball within the drive rod bore
and between the internal surfaces of the jaw members allows it to apply uniform
wedging forces to the jaw members when spreading them apart into a coupling
position.
U.S.Patent No. 5,918,870 discloses a device for detachable fastening of
work pieces to be machined on a processing machine having a pallet on which
the work pieces are detachably fastened, and which can be connected
detachably via this pallet to the processing machine, wherein the locking
between the pallet and one or more quick-clamp cylinders is effected through at
east one pull-in bolt which are fastened on the pallet and which engage in
clamping manner in corresponding receptacles on the quick-clamp
cylinder, and wherein the clamping connection is maintained
through tension springs, and for unlocking a hydraulic piston can
be actuated which overcomes the clamping force of the tension
springs, wherein in the quick-clamp cylinder the space between the
central pull-in bolt and the tension springs arranged to the side
of the latter is sealed.
U.S.Patent No. 5,415,384 discloses an apparatus for clamping
a work piece comprising a base and a work piece carrier adapted to
be put onto and fixed to the base. The base and the carrier com-
prise aligning means to align the position of the carrier relative
to the base along three perpendicular coordinate axes as well as
the angular position. The aligning means comprises first aligning
element pairs in the form of cooperating reference surfaces at the
carrier and the base, which define the position of the carrier in
the Z-axis. The aligning means further comprises second and third
aligning element pairs in the form of cooperating linear aligning
element pairs, which define the position of the carrier in the X
and Y-axes, respectively. The cooperating pairs each comprise a
wedge-shaped centering member and a counterpart member with a
matching centering slit. Clamping means is provided for clamping
the carrier to the base in a well defined position which is de-
fined by the aligning means. The clamping means comprises a plu-
rality of clamping members, each including a pin member fixed to
the carrier and a chuck member located in the base. The carrier
comprises a flat surface which faces the base if the carrier is
clamped to the base. The flat surface forms one of the reference
surfaces. Each one member of the second and third pairs is di-
rectly connected to the flat surface. Each pin member is also di-
rectly connected to the flat surface.
It is an object of the invention to provide a clamping appa-
ratus with a clamping chuck and a work piece carrier releasably
connected thereto whose clamping chuck is particularly suitable
for palletizing systems, whereby the individual clamping chuck shall be very
robust and rigid.
It is a further object of the invention to provide a clamping apparatus with
a clamping chuck and a work piece carrier releasably connected thereto in which
the clamping pin is aligned in X- and/or Y-direction without any clearance.
It is a still further object of the invention to provide a clamping apparatus
with a clamping chuck and a work piece carrier releasably connected thereto in
which a movement of the clamping pin and, thereby, the work piece carrier in Z-
direction is possible after the clamping pin has been aligned in X- and/or Y-
direction, without the need to provide separate elastically resilient means.
In order to meet these and other objects, the present invention provides a
clamping apparatus, comprising a clamping chuck, a work piece carrier adapted
to be releasably connected to said clamping chuck, having a flat bottom surface
and comprising a clamping pin, protruding from said flat bottom surface, said
clamping chuck having a central opening for receiving said clamping pin of said
work piece carrier and having a conical inserting portion, said clamping pin
having at least one surface portion corresponding in shape to the shape of said
conical inserting portion of said central opening for aligning the position of said
clamping pin in X- and/or in Y-direction, and said clamping chuck also comprising
a clamping mechanism for fixing said clamping pin of said work piece carrier in
said central opening, and at least one surface portion serving as a Z-direction
stop member, characterized in that said clamping pin is dimensioned such
that, prior to activating said clamping mechanism, a gap exists between
said flat bottom surface of said work piece carrier and said surface portion of
said clamping chuck serving as a Z-direction stop member after said clamping
pin of said work piece carrier is inserted into said central opening of said
clamping chuck with said at least one surface portion of said clamping pin having
engaging said conical inserting portion of said central opening and thereby
aligning said clamping pin with reference to said clamping chuck in X- and/or Y-
directions, whereby at least one of said clamping pin and the region around said
central opening of said clamping chuck is adapted to be elastically deformed
upon activation of said clamping mechanism to further pull in said clamping pin
into said central opening and simultaneously said work piece carrier towards said
surface portion of said clamping chuck serving as a Z-direction stop member
until said flat bottom surface of said work piece carrier rests on said surface
portion of said clamping chuck serving as a Z-direction stop member.
Thus, the basic idea of the invention may be seen in the fact that the
clamping pin is designed in such a way that it can align itself without clearance in
X- and/or Y-direction upon insertion into the opening of the clamping chuck
without the work piece carrier resting on the clamping chuck. In other words,
during that aligning of the clamping pin, a small gap remains between the bottom
surface of the work piece carrier and the top surface of the clamping chuck. This
gap is removed when the clamping pin is further pulled in into the opening of the
clamping chuck by means of the clamping mechanism, whereby the elasticity of
the material of the clamping pin and/or of the region of the clamping chuck
around the central opening is used for that purpose. Thereby, the work piece
carrier is moved in Z-direction towards the clamping chuck until its flat bottom
surface rests on the Z-direction stop member constituted by the corresponding
surface areas on top of the clamping chuck. In this way, the provision of means
that are elastically resilient in Z-direction can be totally avoided.
In the following, an embodiment of the apparatus according to the
invention will be further described, with reference to the accompanying drawings,
in which:
Fig. 1 shows a perspective view of a clamping chuck and of a work piece
carrier;
Fig. 2 shows a first longitudinal sectional view of the clamping chuck and
of the work piece carrier;
Fig. 3 shows a longitudinal sectional view of the clamping chuck with the
work piece carrier loosely put on;
Fig. 4 shows a longitudinal sectional view of the clamping chuck with the
work piece carrier clamped thereto;
Figs. 5 to 7 show perspective views of different embodiments of clamping
pins;
Fig. 8 shows a perspective view of a machining table and of a pallet; and
Figs. 8a and 8b each show an enlarged view of clamping pins according
to Fig. 8.
Fig. 1 shows a perspective view of a schematically illustrated clamping
apparatus. The clamping apparatus comprises a clamping chuck generally
designated by reference numeral 1 and a work piece carrier generally
designated by reference numeral 40. The work piece carrier 40 is provided with
a clamping pin 30 by means of which the work piece carrier 40 can be fixed to
the clamping chuck 1. Such a clamping apparatus is preferably and particularly
used for exactly position-defined clamping of a work piece in the working area of
a machine tool (not shown). Thereby, as it is the case in the present example,
the work piece carrier 40 can simultaneously be the work piece itself. The bottom
of the upper portion of the clamping chuck facing an actuating piston 10
preferably extends radially downwards from the centre.
The clamping chuck 1, to be fixed to the machine tool by
means known per se and not shown in the drawings, comprises a central
opening 2 adapted to receive and fix the clamping pin 30 of the work
piece carrier 40. The upper area of this opening 2 is designed as a conical
inserting portion 3. The top surface of the clamping chuck 1 is provided with two
annular surface portions 5, 6 located in concentric relationship to the central
opening 2. The annular surface portions 5, 6 serve as Z-references for the work
piece carrier 40, i.e. they define the height position of the work
piece carrier 40 once the lower surface of the latter one rests on
the surface portions 5, 6. As can be seen from Fig. 1, the inner
annular surface portion 5 surrounds the opening 2 in a relatively
small distance. The work piece carrier 40 comprises a flat lower
surface 41 which constitutes a reference surface resting on the
surface portions 5, 6 and, thereby, defining the height position,
i.e. the Z-position of the work piece carrier 40 relative to the
clamping chuck 1. The clamping chuck 1 is provided with a connec-
tor 4 for supplying a hydraulic or pneumatic medium to the inte-
rior of the clamping chuck 1 to lock and release, respectively,
the clamping pin 30 of the work piece carrier 40, as will be ex-
plained herein below in more detail.
Fig. 2 shows a longitudinal sectional view of the clamping
chuck 1 and the work piece carrier 40. The clamping chuck 1 com-
prises a cup-shaped lower portion 8, an upper portion 9 connected
to the lower portion 8 by means of screws 7, and a piston 10 sup-
ported by means of (not shown) biased springs on the upper portion
9. The upper portion 9 is provided with a hollow cylindrical
sleeve 12 projecting downwards from the upper portion 9. The inner
wall of the sleeve 12 defines the opening 2 constituted by a cen-
tral continuous cylindrical bore. The sleeve 12 and the upper por-
tion 9 are designed as a one piece construction, whereby the
sleeve 12 extends downwards into a circular recess 13 machined
into the lower portion 8 of the clamping chuck 1.
The upper end of the clamping pin 30 attached to the work
piece carrier 40 is provided with a cylindrical reference surface
portion 38 as well as with an annular reference surface portion
37. The annular reference surface portion 37 of the clamping pin
30 rests against the flat lower surface 41 of the work piece car-
rier; thus, the lower surface 41 of the work piece carrier, serv-
ing as a Z-reference, takes a well defined position with regard to
the clamping pin 30.
A clamping mechanism 20 for clamping the clamping pin 30 com-
prises, besides the already mentioned piston 10 and the coil
springs (not shown), a plurality of clamping balls 15. The clamp-
ing balls 15 are received in radially extending bores 14 provided
in the wall of the sleeve 12. In order to enable the piston 10 to
be moved, against the bias force of the (not shown) springs, into
the here shown upper end position, a pressure chamber 17 is pro-
vided between the lower portion 8 of the clamping chuck 1 and the
piston 10. The pressure chamber 17 can be hydraulically or pneu-
matically pressurized. For clarity's sake, the gaskets required to
seal the pressure chamber 17 have been omitted from the drawings.
The clamping pin 30, attached to the work piece carrier 40 by
means of a screw 31, comprises a truncated cone shaped portion 32
located at the front end of the clamping pin 30. The back side of
the truncated cone shaped portion 32 forms a circumferential
shoulder 33 on which the clamping balls 15 for pulling in and fix-
ing the clamping pin 30 can rest. Preferably, the front edge 36 of
the clamping pin 30 is rounded. In the region of its rear end, the
clamping pin 30 comprises a further, truncated cone shaped portion
35. The amount of taper of both the front portion 32 and the rear
portion 35 are adjusted to the amount of taper of the conical in-
serting portion 3 of the central opening 2. However, the front
portion 32 is designed such that its minimal outer diameter is
appr. 5 to 10 mm less than the greatest diameter of the conical
inserting portion 3 of the central opening 2 of the clamping chuck
1. In any case, the maximal diameter of the front portion 32 of
the clamping pin 30 is greater than the minimal diameter of the
rear portion 35 of the clamping pin 30. The result is that the
front portion 32 of the clamping pin 30 provides for a course cen-
tering of the clamping pin 30 in the central opening 2, while the
rear portion 35 provides for a fine centering to exactly position-
ally adjust the clamping pin 30 both in X- and in Y-directions.
In order to enable the clamping balls 15 to be radially moved inwards into
their operating position, the piston 10 is provided with an inclined pressure
surface 18. This pressure surface 18 is designed such that the clamping balls 15
are self-lockingly held in their operating position once the piston 10 is in its
locking position. Below the above mentioned pressure surface 18, the piston 10
is provided with an annular groove 19 into which the locking balls 15 can retract
when the piston 10 is in its release position shown in Figs. 2 and 3. It is
understood that the clamping pin 20 can be readily inserted into and removed
from the central opening 2 of the clamping chuck 1 once the piston 10 is in its
release position shown here.
The upper portion 9 of the clamping chuck 1 comprises an inclined lower
surface 21 and the piston comprises a correspondingly inclined upper portion 22.
Together with the sleeve 12 extending up to the lower portion 8 of the clamping
chuck 1, such a design results in a very rigid assembly by means of which very
high pulling forces can be realized without any noticeable deformation of the
upper portion 9 of the clamping chuck 1. Moreover, the one piece design of
sleeve 12 and upper portion 9 of the clamping chuck 1 ensures that when very
high pulling forces act on the work piece carrier 40 clamped to the clamping
chuck 1, there is no danger of the work piece carrier 40 moving in axial direction,
because it is not resilient in Z-direction, in contrast to clamping systems using a
separate clamping ball cage. Furthermore, thanks to the continuous, one-piece
design of the sleeve 12, the sealing of the pressure chamber 17 is simplified.
Before the clamping pin 30 can be inserted into the central opening 2 of
the clamping chuck 1, it has to be coarsely aligned to the opening 2. Thereafter,
the work piece carrier can be lowered downwards onto the clamping chuck 1.
Upon insertion, first, the clamping pin 30 is coarsely centered due to the fact that
its front portion 32 engages the wall portion 3a of the conical inserting portion 3
of the central opening 2. Since the amount of taper of the front portion 32 is
equal to the amount of taper of the inserting portion 3 of the central opening 2,
and since the work piece carrier 40 is held in a horizontal position during
insertion of the clamping pin 30 into the central opening 2, a line contact results
between the front portion 32 of the clamping pin 30 and the wall 3a of the
inserting portion 3 of the central opening 2. In the case of a line contact, the
danger of damage to the clamping pin 30 and to the central opening 2,
respectively, is much lower than in the case of a point contact.
Upon continued insertion of the clamping pin 30 into the central bore 2 of.
the clamping chuck 1, a fine centering of the clamping pin 30 in X- and Y-
directions is accomplished under the influence of the rear truncated cone shaped
portion 35 of the clamping pin 1. Thereby, the rear portion 35 of the clamping pin
30 rests completely on the wall 3a of the conical inserting portion of the central
opening 2. The dimensioning of the clamping is so chosen that a gap S with a
width of between 0.01 to 0.02 mm exists between the annular surface portions 5,
6, serving as a Z-reference, and the flat bottom surface 41 of the work piece
carrier 40 after fine centering, but before clamping the work piece carrier 40 to
the clamping chuck 1, i.e. when the work piece carrier 40 rests only with its
mass on the clamping chuck 1, as shown in Fig. 3. It is to be understood that the
gap S shown in Fig. 3 is greatly exaggerated for the sake of clarity.
Referring to the clamping pin 30, this means that the reference surface
portion 37 of the clamping pin 30, serving as a Z-reference of the clamping pin
30, towers above the annular surface portions 5, 6 by the above mentioned
amount of between 0.01 and 0.02 mm, when the clamping pin 30 is loosely
inserted, i.e. without any pulling force, into the central opening 2 of the clamping
chuck 1. Depending on the design, the size and the dimensioning of the
clamping apparatus, the above mentioned gap S can vary within wider limits, e.g.
between 0.005 mm and 0.1 mm. It is to be understood that the lower surface of
the work piece carrier 40 does not compellingly have to be flat, but that it can
comprise different surfaces and/or planes. Important is only, the clamping
apparatus still being in its released state, that a gap within the above mentioned
limits exists between the coaxial surface portions 5, 6, serving as Z-stop
members of the clamping chuck 1, and the surface areas of the work piece
carrier 40 that are intended to rest on these surface portions 5, 6, such that the
clamping pin 30 can align in X- and Y-directions without clearance to the
inserting portion 3 of the central opening 2. Further, it is to be understood that
the reference surface portion 37 of the clamping pin 30, constituting the Z-
reference thereof, is not necessary to coincide with the bottom surface 41 of the
work piece carrier 40, but it can, if appropriate, be recessed or protrude
therefrom, depending on the design of the clamping pin 30 and/or the work piece
carrier 40 and its bottom surface, respectively.
Fig. 4 shows a longitudinal sectional view of the clamping chuck 1 with the
work piece carrier 40 clamped onto it. In order to clamp the loosely inserted work
piece carrier 40 to the clamping chuck 1, the pressure in the pressure chamber
17 is reduced, with the result that the piston 10 is pushed down into the position
shown in Fig. 4 under the influence of coil springs 23, 25, as will be described in
more detail herein after. Thereby, the clamping balls 15 are radially moved
inwards, as is known in the art, where they rest on the shoulder 33 of the
clamping pin 30, thereby puling the latter one downwards. When a high pulling
force of up to 20 KN is exerted, the length of the clamping pin 30 is slightly
increased, with a simultaneous decrease of its diameter, and the conical shaped
inserting portion 3 of the central opening 2 is slightly widened.
The result is that the clamping pin 30 is pulled into the central opening 2
somewhat deeper, with the work piece carrier 40 moving downwards in Z-
direction until its flat bottom surface 41 rests on the surface portions 5, 6 of the
clamping chuck 1, serving as Z-stops. Thus, the work piece carrier 40 is
positioned not only in X- and Y- directions, but also in Z-direction. In other words:
The alignment of the work piece carrier 40 with regard to the clamping chuck 1 in
X- and Y- directions is accomplished without any clamping force acting on these
two elements, while the movement of the work piece carrier 40 in Z-direction is
accomplished exclusively by making use of the elasticity of the material of the
clamping pin 30 and of the clamping chuck 1 in the region of its inserting portion
3 of the central opening 2.
The elements of the clamping apparatus essential for the operation
thereof are adjusted to each other, as far as dimensions and shape is
concerned, in such a way that the reduction of the width of the gap S between
the flat bottom surface 41 of the work piece carrier 40 and the surface portions 5,
6 of the clamping chuck 1 to zero, after the fine positioning of the clamping pin
30, and, therewith, the work piece carrier 40 in X- and Y-directions, is realized
essentially exclusively with the help of the elasticity of the material of the
clamping pin 30 as well as of the clamping chuck 1 in the region of the central
opening 2. Thus, and in contrast to clamping apparatuses of the prior art, no
members or elements that are elastically resilient in Z-direction have to be
provided.
From Fig. 4, showing a longitudinal sectional view of the clamping chuck 1
together with the work piece carrier 40 clamped thereto, particularly also the coil
springs 23, 25 are evident, these springs being provided for biasing the piston 10
and responsible for the pulling force exerted on the clamping pin 30. For
clarifying the design of the clamping chuck I, the left side of the drawing shows a
sectional view taken through the coil springs of the clamping chuck I, while the
right side shows a sectional view taken between adjacent coil springs of the
clamping chuck 1.
Depending on the required pulling force, both the number of
coil springs and their spring force can be selected. For realizing
very high pulling forces, twin springs can be provided as can be
seen in the left side of Fig. 4, where two coil springs 23, 24 are
arranged coaxially one in the other one. For compensating of
torque forces that may be exerted to the upper portion 9 of the
clamping chuck 1, the winding sense of diametrically opposite coil
springs 23, 25 is different. Preferably, the clamping chuck 1 is
provided with a plurality of coil springs evenly distributed along
a circular path; for example, to reach high pulling forces, prac-
tice has shown that a total of 16 coil springs should be used,
i.e. 8 outer coil springs 23 and 8 inner coil springs 24.
Moreover, the right side illustration in Fig. 4 shows that
the clamping mechanism can take high pulling forces due to the one
piece design of the sleeve 12 and the upper portion 9 of the
clamping chuck 1, and due to the clamping balls 15 being received
in the sleeve 12 essentially without clearance.
In order to remove the work piece carrier 4 0 from the clamp-
ing chuck 1, the piston 10 is pneumatically cr hydraulically moved
upwards, against the force of the coil springs. Thereby, the
clamping balls 15 are released with the result that they can move
back into the groove 19, freeing the clamping pin 30 which now can
be pulled upwards out of the central opening 2 of the clamping
chuck 1. The clamping mechanism having been released, both the
clamping pin 30 and the upper portion of the central opening 2 of
the clamping chuck 1 revert to their original dimensions due to
their elastic behavior.
Figures 5 to 7 show three different embodiments of clamping
pins 30, 30a and 30c, respectively, which are suitable to be used
in combination with a large pallet comprising several clamping
pins. The uppermost clamping pin 30 shown in Fig. 5 corresponds to
the embodiment discussed already herein before; it comprises a
surface portion 35 in the shape of a truncated cone for centering
in X- and Y-directions and located at the rear end of the clamping
pin 30. The clamping pin 30a shown in Fig. 6 comprises at its rear
end, instead of a truncated cone shaped portion, two diametrically
opposite surface portions 35a in the shape of a segment of a trun-
cated cone. It is understood that only the frontal surface portion
35a can be seen in Fig. 6, while the rear one is hidden in this
view. However, in Fig. 6a showing the clamping pin 30a in a side
elevational view, both surface portions 35a are visible. By means
of these surface portions 35a, the clamping pin 30a can be cen-
tered by means of the conical inserting portion 3 of the central
opening 2 (Fig. 1) in one direction only, preferably in X-
direction or in Y-direction. In order to enable the clamping pin
30a and its surface portions 35a, respectively, to be properly
aligned upon attaching it to the work piece carrier 40, the clamp-
ing pin 30a is provided with two diametrically opposite flattened
portions 39, adapted to be engaged by a wrench or similar tool.
The lowermost clamping pin 30c according to Fig. 7 is provided at
its rear end with a surface portion 35c having the shape of a
truncated cone. However, that surface portion 35c has an outer di-
ameter about 0.1 to 0.2 mm smaller than the outer diameter of the
surface portion 35 of the clamping pin 30 according to Fig. 5.
Thus, the clamping pin 30c acts as a simple clamping element with-
out any centering and positioning function. The clamping apparatus
being in its clamped state, i.e. if the flat bottom surface of the
work piece carrier rests on the Z-reference surface portions of
the clamping chuck, a gap in the region of 0.1 to 0.2 mm exists
between the truncated cone shaped portion 35c of the clamping pin
30c according to Fig. 7 and the conical inserting portion 3 of the
central opening 2 of the clamping chuck 1 (Fig. 1).
Instead of being provided with a truncated cone shaped por-
tion 35, the clamping pin 30 according to Fig. 5 could be equipped
with four surface portions 35a in the shape of a segment of a
truncated cone, evenly distributed along the rear periphery of the
clamping pin 30, for aligning it in X- and Y-directions.
Fig. 8 shows a perspective view of a machining table 42
equipped with four clamping chucks 1, la, lb and lc, as well as of
a work piece carrier 43, called a pallet in the following,
equipped with four clamping pins 30, 30a, 30b and 30c. Out of the
four clamping pins 30, 30a, 30b and 30c, the frontmost clamping
pin 30 corresponds to the one shown in Fig. 5, provided with a
truncated cone shaped portion 35 for centering the pin 30 in X-
and Y-directions. This clamping pin 30 sets the origin once the
pallet 43 having been clamped to the machining table 42. The two
lateral clamping pins 30a and 30b are designed according to the
embodiment shown in Fig. 6, each comprising two diametrically op-
posite surface portions 35a and 35b, respectively, in the shape of
a segment of a truncated cone, whereby again only the frontal sur-
face portions 35a and 35b, respectively, are visible. The rearmost
clamping pin 30c, finally, corresponds to the embodiment according
to Fig. 7 and acts only as a clamping member without any centering
or positioning functions for clamping the pallet 43 to the machin-
ing table 42.
Fig. 8a shows an enlarged view of the right clamping pin 30a,
and Fig. 8b shows an enlarged view of the left clamping pin 30b.
These two clamping pins serve for determining the angular position
of the pallet 43 around the origin defined by the clamping pin 30.
Thereby, the surface portions 35a of the right clamping pin 30a
align the pallet 43 in Y-direction, while the surface portions 35b
of the left clamping pin 30b align the pallet 43 in X-direction.
As mentioned before, the rearmost; clamping pin 30c serves only for
clamping the pallet 43 in Z-direction.
Even if two clamping pins 30a, 30b are provided in this em-
bodiment for determining the angular position of the pallet 43
around the origin, it could be sufficient to provide only one
clamping pin for this purpose. However, the design and arrangement
of the clamping pins shown in Fig. 8 and discussed herein before
has the advantage that no geometric over-determination of the po-
sition of the pallet upon clamping occurs, because thermal dimen-
sion changes of the pallet are compensated for by the correspond-
ing clamping pins. Tests carried out on this subject have shown
that the surface portions 35a of a clamping pin 30a designed ac-
cording to the embodiment of Fig. 6 can equalize thermally caused
expansions or dimensional deviations of the pallet 43 up to as
much as 0.1 to 0.2 mm.
Besides the clamping chucks 1 discussed herein before which
per se do not comprise any means for determining the angular posi-
tion around the Z-axis of the work piece carrier, other clamping
chucks could be provided which do comprise means for determining
not only the position in X- and Y-directions, but also the angular
position around the Z-axis, with the result that, if appropriate,
a work piece carrier having only one clamping pin can be clamped
"to the clamping chuck both in a desired linear and angular posi-
tions. It is understood that, in such a case, the work piece car-
rier would be provided with suitable positioning means, whereby
the clamping pin serves only for a coarse positioning of the work
piece carrier, but not for a fine positioning. Then, the clamping
pin would have the design as shown in Fig. 7 and discussed in con-
nection therewith.
WE CLAIM :
1. A clamping apparatus comprising a clamping chuck and a work piece
carrier adapted to be releasably connected to said clamping chuck, having a flat
bottom surface and comprising a clamping pin, protruding from said flat bottom
surface, said clamping chuck having a central opening for receiving said
clamping pin of said work piece carrier and having a conical inserting portion,
said clamping pin having at least one surface portion corresponding in shape to
the shape of said conical inserting portion of said central opening for aligning the
position of said clamping pin in X- and/or in Y -direction, and said clamping
chuck also comprising a clamping mechanism for fixing said clamping pin of said
work piece carrier in said central opening, and at least one surface portion
serving as a Z-direction stop member, characterized in that said clamping pin is
dimensioned such that, prior to activating said clamping mechanism, a gap exists
between said flat bottom surface of said work piece carrier and said surface
portion of said clamping chuck serving as a Z-direction stop member after said
clamping pin of said work piece carrier is inserted into said central opening of
said clamping chuck with said at least one surface portion of said clamping pin
engaging said conical inserting portion of said central opening and thereby
aligning said clamping pin with reference to said clamping chuck in X- and/or Y-
directions, whereby at least one of said clamping pin and the region around said
central opening of said clamping chuck is adapted to be elastically deformed
upon activation of said clamping mechanism to further pull in said clamping pin
into said central opening and simultaneously said work piece carrier towards said
surface portion of said clamping chuck serving as a Z-direction stop member
until said flat bottom surface of said work piece carrier rests on said surface
portion of said clamping chuck serving as a Z-direction stop member.
2. Clamping apparatus as claimed in claim 1, wherein said gap between said
flat bottom surface of said work piece carrier and said surface portion of said
clamping chuck serving as a Z-direction stop member has a width of 0.005mm to
0.1mm.
3. Clamping apparatus as claimed in claim 1, wherein said clamping pin has
a surface portion constituting a Z-reference which protrudes above said surface
portion of said clamping chuck serving as a Z-direction stop member by an
amount of 0.005m to 0.1mm after said clamping pin is aligned in X- and / or Y-
direction.
4. Clamping apparatus as claimed in claim 1, wherein said clamping pin has
a front surface portion serving as a coarse centering portion and a rear surface
portion serving as a fine centering portion.
5. Clamping apparatus as claimed in claim 4, wherein said front surface portion
of said clamping pin has the shape of a truncated cone.
6. Clamping apparatus as claimed in claim claim 4, wherein said rear surface
portion of said clamping pin has the shape of a truncated cone surface adapted
to align the position of the clamping pin in X- and Y-directions in cooperation with
said conical inserting portion of said central opening of said clamping chuck.
7. Clamping apparatus as claimed in claim 4, wherein the maximal diameter
of said front surface portion of said clamping pin is greater than the minimal
diameter of said rear surface portion of said clamping pin.
8. Clamping apparatus as claimed in claim 4, wherein the rear portion of said
clamping pin has two diametrically opposite surface portions adapted to align
said clamping pin in X- or Y-direction.
9. Clamping apparatus as claimed in claim 4, wherein the rear portion of said
clamping pin has four surface portions evenly distributed along the periphery of
said clamping pin and adapted to align said clamping pin in X- and Y-direction.
10. Clamping apparatus as claimed in claim 8 or 9, wherein said rear surface
portions have the shape of a segment of a truncated cone.
11. Clamping apparatus as claimed in claim 1, wherein said central opening of
said clamping chuck is designed as a continuous smooth bore.
12. Clamping apparatus as claimed in claim 5, wherein the minimal outer
diameter of said front, truncated cone shaped surface portion of said clamping
pin is between 3 to 15mm smaller than the maximal diameter of said conical
inserting portion of said central bore of said clamping chuck.
13. Clamping apparatus as claimed in claim 5, wherein the taper of said front
surface portion of said clamping pin corresponds to the taper of said conical
inserting portion of said central bore of said clamping chuck.
14. Clamping apparatus as claimed in claim 1, wherein said clamping pin has
a circumferential shoulder; and
said clamping mechanism comprises a plurality of clamping balls as well
as an actuating piston which is movable, for radially moving the clamping balls,
from a release position into a clamping position in which said clamping balls
engage said circumferential shoulder of said clamping pin.
15. Clamping apparatus as claimed in claim 14, wherein said actuating piston
is axially movable and is received between an upper portion of said clamping
chuck and a lower portion of said clamping chuck; and
said actuating piston is biased by means of springs resting on said upper
portion of said clamping chuck towards said lower portion of said clamping
chuck.
16. Clamping apparatus as claimed in claim 14, wherein said actuating piston
is pneumatically or hydraulically movable, against the biasing force of said
springs, from a clamping position to a release position.
17. Clamping apparatus as claimed in claim 15 or 16, wherein said upper
portion of said clamping chuck comprises a hollow cylindrical sleeve member
whose interior constitutes said central opening in said clamping chuck adapted to
receive said clamping pin and which is provided with radially extending bores
adapted to receive said clamping balls.
18. Clamping apparatus as claimed in claim 17, wherein said hollow
cylindrical sleeve member extends up to said lower portion of said clamping
chuck.
19. Clamping apparatus as claimed in claim 15, wherein at least two
diametrically opposite helical springs are provided for biasing said actuating
piston, the winding direction of opposite helical springs being different.
20. Clamping apparatus as claimed in claim 19, wherein in each case the two
helical coils are coaxially arranged.
21. Clamping apparatus as claimed in claim 15, wherein the bottom of the
upper portion of the clamping chuck facing said actuating piston extends from
the center radially downwards.
22. A clamping apparatus comprising at least two clamping chucks and a
work piece carrier adapted to be releasably connected to said clamping chucks,
having a flat bottom surface and comprising a plurality of clamping pins
protruding from said flat bottom surface, said clamping chucks each having a
central opening for receiving one of said clamping pins of said work piece carrier,
said central opening having a conical inserting portion, wherein one of said
clamping pins has a surface portion corresponding in shape to the shape of said
conical inserting portion of said central opening for aligning the position of said
clamping pin in X- and in Y-direction, and wherein at least another one of said
clamping pins has a surface portion having a shape for aligning the position of
said clamping pin only in X- or only in Y-direction, and each of said clamping
chucks also comprising a clamping mechanism for fixing one of said clamping
pins of said work piece carrier in said central opening, and at least one surface
portion serving as a Z-direction stop member, characterized in that each of said
clamping pins is dimensioned such that, prior to activating said clamping
mechanism, a gap exists between said flat bottom surface of said work piece
carrier and said surface portion of said clamping chuck serving as a Z-direction
stop member after a clamping pin of the workpiece carrier is inserted
into the central opening of the corresponding clamping chuck with said surface
portion of a clamping pin engaging said conical inserting portion of said central
opening and thereby aligning the clamping pin with reference to the
corresponding clamping chuck in X- and/or Y-directions,
wherein at least one of the clamping pin and the region around the central
opening of the clamping chuck is adapted to be elastically deformed upon
activation of said clamping mechanisms to further pull in the clamping pins into
the central opening and simultaneously said work piece carrier towards said
surface portions of said clamping chucks serving as a Z-direction stop member
until said flat bottom surface of said work piece carrier rests on said surface
portions of said clamping chucks serving as a Z-direction stop members.
23. Clamping apparatus as claimed in claim 22, wherein said at least another
one of said clamping pins is adapted to align the work piece carrier only in X-
direction or only in Y- direction ; and
a rear portion of said at least another one of said clamping pins is
provided with two diametrically opposite surface portions.
24. A clamping apparatus comprising a clamping chuck and a work piece
carrier, substantially as herein described, particularly with reference to the
accompanying drawings.
The clamping apparatus comprises a clamping chuck (1) and a work
piece carrier (40), the chuck having a central opening (2) for receiving a clamping
pin (30) attached to the work piece carrier (40), having a conical inserting portion
(3), and the clamping pin having at least one surface portion (32) corresponding
to the inserting portion (3), the clamping chuck also comprises a clamping
mechanism (20) for clamping the clamping pin and the top of the clamping chuck
having at least one surface portion (5, 6) serving as a Z-stop member, wherein,
prior to activating the clamping mechanism, there is a gap between a flat bottom
surface (41) of the work piece carrier and the surface portion (5, 6) of the chuck
(1).

Documents:

674-cal-2002-granted-abstract.pdf

674-cal-2002-granted-claims.pdf

674-cal-2002-granted-correspondence.pdf

674-cal-2002-granted-description (complete).pdf

674-cal-2002-granted-drawings.pdf

674-cal-2002-granted-examination report.pdf

674-cal-2002-granted-form 1.pdf

674-cal-2002-granted-form 18.pdf

674-cal-2002-granted-form 2.pdf

674-cal-2002-granted-form 3.pdf

674-cal-2002-granted-form 5.pdf

674-cal-2002-granted-priority document.pdf

674-cal-2002-granted-reply to examination report.pdf

674-cal-2002-granted-specification.pdf

674-cal-2002-granted-translated copy of priority document.pdf

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Patent Number

224153

Indian Patent Application Number

674/CAL/2002

PG Journal Number

40/2008

Publication Date

03-Oct-2008

Grant Date

01-Oct-2008

Date of Filing

03-Dec-2002

Name of Patentee

EROWA AG

Applicant Address

WINKELSTRASSE 8, CH-5734 REINACH

Inventors:

#	Inventor's Name	Inventor's Address
1	FRIES KARL	BOHNACKERSTRASSE 3, CH-5734 REINACH

PCT International Classification Number

B23Q 1/00,B23Q 3/18

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	2001-2318/01	2001-12-19	Switzerland