Title of Invention	METHOD OF OPERATING AN ACTUATOR AND APPARATUS FOR CARRYING OUT THE METHOD
Abstract	The invention relates to a method for operating an actuation device (20), ' which is used to clamp and loosen a clamping device which comprises a tie bolt which can be adjusted in an axial manner in a machine spindle (3), for actuating a clamping head (6) which co-operates with clamping claws (5). Initially, force is exerted upon the tie bolt (4) by means of an actuation device (20) which is used to clamp in an axial clamping direction, until the axial length thereof is fixed in relation to the machine spindle (3) by means of self-locking. According to the invention, after self-locking is obtained, the effect of the force in the direction of clamping of the actuation element (20) on the tie bolt is stopped and remains blocked whilst the clamping device is being used, and to release clamping, the tie bolt (4) is displaced by the actuation device (20) in the direction of release which is counter to the clamping direction. The invention relates to a device for carrying out said method.

Title of Invention

METHOD OF OPERATING AN ACTUATOR AND APPARATUS FOR CARRYING OUT THE METHOD

Abstract

The invention relates to a method for operating an actuation device (20), ' which is used to clamp and loosen a clamping device which comprises a tie bolt which can be adjusted in an axial manner in a machine spindle (3), for actuating a clamping head (6) which co-operates with clamping claws (5). Initially, force is exerted upon the tie bolt (4) by means of an actuation device (20) which is used to clamp in an axial clamping direction, until the axial length thereof is fixed in relation to the machine spindle (3) by means of self-locking. According to the invention, after self-locking is obtained, the effect of the force in the direction of clamping of the actuation element (20) on the tie bolt is stopped and remains blocked whilst the clamping device is being used, and to release clamping, the tie bolt (4) is displaced by the actuation device (20) in the direction of release which is counter to the clamping direction. The invention relates to a device for carrying out said method.

Full Text	MSTHOD OP OPERATING AN ACTUATOR AMD APPARATUS FOR CARRYIN5 OUT THE The invention relates to a method of operating an actuator that is used to clanp and release a chuck having a rod that can be axially displeured in a machine spindle for actuating a clanping head with jaws, and where to start with for clanping a force in an axial clanping direction on the rod by means of the actuator until the axial position of the rod is fixed relative to the machine spindle, and after self-locking is established the application of force in the clanping direction by the actuator on the rod is suspended and remains suspended while the chuck is in operation, and to release the clanp the rod is displaced by the actuator in a release direction that is opposite the claiming direction. The invention further relates to an apparatus for carrying out the method. Chucks are known from the prior art, for example from DE 140 638 Al [US 6,568,888], that by means of collet chucks are used to clanp workpieces having, for example, a collet. To actuate such chucks, actuators, also referred to as release units, are used that axially displace a rod associated with the chuck, and to clanp the workpiece the rod is pulled in the direction away from the collet chuck and, with application of the necessary clanping force, is held in this position by the actuator, the correct positioning of the rod being assisted by spring washer assemblies or helical spring washers. The actuator moves the rod in the opposite direction to discontinue the clanping. Although such chucks with associated actuators and the method required for their operation have proven to be successful in practice, the known prior art has limitations when the balance quality nuts be continually improved as rotation speeds of the spindle increases, and in particular the spring-washer asexualizes or helical. spring washers have an adverse effect since they bear continuously on the rod. The object of the present invention, therefore, is to provide a method of operating an actuator that may be carried out in the absence of such springs. A further object of the invention is to provide an apparatus for carrying out the method. The part of the object of the invention relating to the method is attained by use of the above-described method that is characterized in that a force need be exerted on the rod only for claiming and releasing, whereas during operation of the chuck on the machine spindle, which is rotating at high speed, it is not necessary to exert force on the rod. In order to shorten the resetting time, for example for changing tools, it should be noted that during clanping after locking is established it is also possible to reduce the application of force during start-up of the machine swindler i. e the machine spindle may already be started, whereas the force transmission from the actuator to the rod has been suspended. It is also within the scope of the invention, in particular from a safety standpoint, that during release the application of force in the release direction is not commenced until the machine spindle has reached a standstill; i. e only after the machine spindle has reached a complete standstill is the force transinLssion chain between the actuator and the rod reestablished, in order to avoid injury or dotage as the result of insxifficiently clamped workpieces. The part of the object of the invention relating to the apparatus is attained by the fact that a chuck is provided having a rod that is supported in a machine spindle so as to be axially displaceable in order to actuate a claiming head that cooperates with the jaws, the axial position of the rod in the clanped position having been secured by self-locking, and an actuator is provided that in the self-locked position of the rod is decoupled from it in a positive-fit manner. By use of this design, in particular negative effects on the balance quality caused by the part o£ the actuator necessary for actuating the rod may be prevented, and in particular so that the connection of the rod to the actuator does not adversely affect the balance quality. These advantages may be realized in a particularly simple tanner by positioning the actuator so as not to contact the rod in the clanped position of the rod, i. e so that the free-standing rod together with the entire machine spindle is able to rotate without contact with the actuating system In one advantageous embodiment, the rod has a first wire-wound coil that is provided for interaction with a second wire-wound coil of the machine spindle and coaxial with the first wire-wound coil that is coupled in a contact-free manner with a stator of the stationary actuator housing* In principle, this design forms a linear motor that can move the rod in the calcimine direction or the release direction as the resist of different current directions. One very particularly preferred embodiment is characterized in that the rod has an annular collar provided in a piston chamber of a first piston that is located in a cylindrical chamber of the actuator that nay be acted on by a pressure medium In this embodiment in contrast to the embodiment that makes use of the wire-wound coils’ a contact operational method of clanping and releasing is auk-lowed’ it being ensured that the rod together with its annular collar is positioned without contact with the actuator during operation of the chuck, since this is the key criterion for achieving high rotational speeds with good balance quality, whereas during standstill, contact may be allowed for switching on the chuck. It is also within the scope of the invention that, starting from a center position, the displacement stroke of the first piston in the cylindrical chamber is greater in both directions than the displacement stroke of the annular collar in the piston chamber in both displacement directions, so that the additional displacement capability of the first piston not only allows contact to be made between the annular collar and the piston chamber, but also allows the necessary displacement of the rod for actuation of the chuck. It is particularly preferred when a second piston is provided in a second cylindrical chamber in the actuator that bears on the first piston in the clipped position of the rod. For proper functioning of this apparatus it is essential that the annular collar precisely maintains the center position in the piston chattber during operation, this precise positioning being difficult to ensure solely by controlling the pressure conditions in the cylindrical chancre Use of the second piston easily provides this assurance by establishing in the clanped position the correct position of the first piston and thus the position of the annular collar in its piston chancier. To establish the correct position of the second piston in the clasped position, the second piston has a larger effective diameter than the first piston, and the opposite sides of the first piston and the second piston in the clanped position of the rod are acted on with equal pressure via a three-way valve. It is also within the scope of the invention that for stroke control a ring sensor is associated with the actuator for interaction with an indicator associated with the rod, so that this enibodiraent offers the possibility of monitoring the displacement of the rod for introduction of the clanping force. A further alternative embodiment is characterized in that the actuator has a rotary feed through fitting having a manifold shaft connected to the nachine spindle and a rotationally fixed manifold housing that carries pressure medium connections that are used for applying pressure to the two sides of a piston provided in a piston chamber and connected to the rod. In this embodiment it is important that a connection to the rod occurs without contact with the actuator in any operating position during, i* e. clanping, releasing, or during operation, but that in the clanped position the actuator is decoupled from the rod in a positive-fit manner corresponding to the above-described requirements; i. e the pressure medium connections are acted on by pressure only for switching on, and are switched on for unpressurized operation, since in particular at the desired high rotational speeds of up to 120,000 revolutions per minute the seals are subjected to increased wear under pressure lieu. According to a further embodiment, a spindle collar having a circumferential groove is provided on the machine spindle, and at least two diametrically opposite pins engage in the groove for relieving the spindle during clanping and release, the pins being provided on the axially displaceable e cylinder wall of the actuator, and two springs acting in the two displacement directions and supported on the housing being associated with the cylinder wall in order to establish a center position of the pins following clanping and reuse Alternatively or additionally, in order to establish a center position of the pins following clanping and release a funnel-shaped surface nay be associated with the cylinder wall, and a centering element nay be associated with the housing, in the simplest design the centering element being formed by a spring-loaded ball. However, the centering element nay also be formed by a conical pin that nay be acted on by a pressure medium A further embodiment having two pistons associated with the actuator is characterized in that the first piston serves for with the clanping process and bears on the annular collar during clanping, and a release piston that can be displaced independently of the first piston and that bears on the annular collar during release is provided in the actuator. The invention is in greater detail below with reference to the shown endDodiinents shown in the drawing. Therein: FIG. 1 is a longitudinal section through the chuck to be operated by the actuator; FIG. 2 is a somewhat schematic longitudinal section through a first embodiment of the actuator; FIG. 3 is a view like Fig. 2 of a second enbodimeat of the actuator; FIG* 4 is a view like FIG. 2, of a further embodiment of the actuator; FIG. 5 is a view like FIG. 3 with relief of the spindle FIG. 6 is a view like FIG* 5, in an alternative embodiment of relief of the spindly* and FIG. 7 is a further of an actuator having two pistons. The drawing shows a chuck used for clanping a workpiece 2 having a collet 1, or for clanping a tool, to which end the chuck has a rod 4 that is supported so as to be axially displaceable in a body 3 and that is provided for actuating a clanping head 6 that cooperates with jaws 5, namely, by axial displacement of the rod 4 between a release position shown in the lower half of FIG. 1 and a clanped position shown in the upper half of FIG. 1. The workpiece 2 is clanped by pulling the rod 4 from the release position into the clanped position by means of an actuator 20, shown in the drawing in FIGS. 2 through 4 and to be described in greater detail by drawing back jaws 7 and a threaded bolt 8 as well as a threaded ring 9 the clanping head 6 is axial y displaced, thereby radially displacing the outer ends 10 of the jaws 5 so as to make contact with the collet 1. In the chuck shown in FIG. 1, it is noted that a clanping sleeve 11 is provided in the body 3 so as to be axially nondisplaceable, the jaws 7 being axially guided in the clanping sleeve and having their inner faces resting against the rod 4, the rod 4 having a conical head 12, and the jaws 7 having a tapered ring 13, and the clanping sleeve 11 having an internal conical surface 14, resulting in self-locking that locks the axial position of the jaw outer ends 7 when the rod 4 moves from the release position to the clanped position, without the actuator having to exerting additional tension on the rod 4. The force applied by the actuator 20 through the rod 4 is thus stored, so to speak, by means c’ this self-locking action, and the secure clasping of the workpiece 2 at its collet 1 is ensured without having to use a tension spring that with its spring force would have to ensure the axial position of the rod 4 with respect to the body 3 or the clanping sleeve 11 in the clanped position. The security of the clanping therefore is not jeopardized by fatigue of the tension spring. In addition, as the result of using self-locking, the rod 4, which is not engaged by a tension spring, is able to rotate with the entire spindle, i. e, the body 3, without having to be connected with its actuator 20, enabling the balance quality to be improved and the rotational speed to be increased. The drawing also shows that the conical head 12 merges with the rod 4 by a radially extending shoulder 15, and that the jaw outer ends 7 have an inner shoulder 16 for engagement with the shoulder 15, and that the jaw outer ends 7 together with their inner shoulder 16 are able to be spread by the shoulder 15 in the axi2LL region of the conical inner surface 14 of the clanking sleeve 11. In the enbodiment shown in the drawing, the conical haul 12 has an apex angle of 6E, whereas the conical inner surface 14 of the clanping sleeve 11 has an apex angle of 12E* The inclination of the inner circumferential surface and of the outer circumflex rental surface of the tapered ring 13 correspond to the inclination of the corresponding contacting coicponents. The operation of the apparatus is briefly y described below. Starting from the release position shown in the lower half of the figure, the actuator 20 exerts a tension on the rod 4 that moves the rod 4 to the left in the drawing. During this displacement, as a result of the contact of the inner shoulder 16 of the jaw outer ends 7 against the shoulder 15 a£ the rod 4, the rod 4 first entrains the jaw outer ends 7 that to avoid imbalance are guided relative to the clanping sleeve in two elongated holes 17, and by means of the threaded bolt 8, threaded ring 9, and clanping head 6 the jaws 5 with their jaw outer ends 10 pivot radially outward and come to rest against an undercut 18 of the collet 1. The interaction of the shoulder 15 with the inner shoulder 16 restarts in rapid axial displacement of the clanping head 6, and after traveling a predetermined axial distance the inner shoulder 16 of the jaws 7 is able to disengage from the shoulder 15, and with the inner surface of the tapered ring 13 comes to rest against the conical head 12 while at the same time being pressed with the outer circumferential surface agar’s the tapered ring 13 of the clipping sleeve’s 11. The jaws 7 are thus carried along in the axial direction only to a slight degree during continued axial. displacement of the rod 4, but with increasing force between the conical head 12 and the clanping sleeve 11 the jaws are wedged until self-locking is attained that provides the established clanping force when the tension from the actuator 20 is no longer applied to the rod 4. To release the chuck, the rod 4 is moved to the right from the clipped position to the release position, thereby unlocking the jaws 7 from the wedged conical head 12 and the claiming sleeve 11 and also displacing the rod 4 relative to the jaws 7 until the rod =s contact surface 19 come to rest against the threaded ring 9’ and the inner shoulder 16 is once more able to engage behind the shoulder 15 of the rod 4. Continued movement of the rod 4 displaces the clipping head 6, causing the jaws 5 with their jaw outer ends 10 to release the 2. The clanping and release of this chuck may optionally be acconplished by use of one of the actuators 20 shown in FIGS. 2 through 4 that are all characterized in that the force transmission chain from the actuator 20 to the rod 4 is interrupted in the clanped position of the rod 4. In the embodiments of FIGS. 2 and 3 this is accoziplished by the fact that in the clanped position of the rod 4 the actuators 20 are out of contact with the rod, whereby in the embodiment in FIG. 2, the rod 4 is provided with a first wire’wound coil 21 that is provided for interaction with a second wire-wound coil 22 carried on the machine spindle 3, coaxiaaiy surrounding with the first wire’wound coil 21, and coupled in a contact-free scanner with a stator associated with the stationary actuator housing 20 [23], This actuator 20 acts in a contact-free manners on the rod 4 in eJ.1 operating positions for calquing and releasing as well as during operation of the chuck when the latter is rotated together with the machine spindle 3 at high speeds. FIG* 3 shows in which the rod 4 has an annular collar 26 that is provided in a piston chairiber 27 of a first piston 28 that is located in a cylindrical charier 29 of the actuator that inlay be acted on by a pressure median the displacement stroke of the first piston 28 in the cylindrical chairiber 29/ starting from a center position, being greater in both directions than the displacement stroke of the annular collar 26 in the piston chairiber 27 in both displacement directions, so that in addition to the displacement of the first piston 28 for contacting the annular collar 26 with the axial end and back faces of the piston chairiber, the continued displacement nay force actuation of the clanping head 6. However, to ensure that contact with the end and back faces of the piston chamber 27 is once again released for the annular collar 26 when the rod 4 has assumed its working position after achieving self-locking, a second piston 31 is provided in a second cylindrical chairiber 30 in the actuator 20 that acts on the first piston 28 in the clanped position of the rod 4, the second piston 31 having a larger effective diameter than the first piston 28, and the mutually opposing sides of the first piston 28 and the second piston 31 in the clanped position of the rod 4 being acted on with equal pressure via a three-way valve 32, so that the larger effective surface of the second piston 31 ensures contact thereof with the first piston 28, and contact of the second piston 31 with the end face of the second cylindrical chanber 30 is ensured to set the center position of the annular collar 26* In this embodiment, for stroke control a ring sensor 33 is associated with the actuator 20 for interaction with an indicator 34 carried on the rod. FIG. 4 shows a further embodiment in which the actuator 20 has a rotary feed through fitting 35 having a manifold shaft 36 connected to the nachine spindle 3 and a rotationally fixed manifold housing 38 that carries pressure medium connections 37, the pressure medium connections 37 being used for Appl’ ng pressure to the two sides of a piston 40 provided in a chairiber 39 and connected to the rod 4, in this einbodiment the rod 4 having no contact with the actuator 20 in any operating position, but, rather, the desired interruption of the force transmission chain being provided during operation of the chuck, since after self-locking is established the pressure medium connections 37 may be d In ell the embodiments in FIGS, 2 through 7, also associated with the actuator 20 at its axial end is a supply device 25 that may be used for supplying air or a coolant for the rod 4 into the chuck. FIG. 5 shows an exibodixnent in which a spindle collar 41 having a circumflex eventual groove 42 is provided on the neighing spindle 3, and at least two diametrically opposite pins 43 engage in the groove for relieving the spindle during clanping and release, the pins being provided on the axially displaceable cylinder wall 44 of the actuator 20, and two springs 45 acting in the two displacement directions and supported on the housing being provided on the cylinder W2LL1 44 in order to urge the pins 43 into a center position following clanping and release’* in contrast, FIG. 6 shows an that nay be used for assistance, in which in order to center the pins 43 following clanping and release a funnel-shaped surface 46 is associated with the cylinder wall 44, and a centering element 47 is associated with the housing, the centering element being formed either by a spring-loaded ball 48 (FIG. 5) or by a conical pin 49 that nay be acted on by the pressure medium Finally, FIG. 7 shows an embodiment in which, although two pistons are associated with the actuator 20, they do not act independently namely, the first piston 28 is associated with the clanping process and bears on the annular collar 26 during clanping, and a release piston 50 that can be displaced independently of the first piston 28 and that bears on the annular collar 26 during release is provided in the actuator 20. Claims: 1. A method of operating an actuator (20) that is used to clap and release a chuck having a rod that can be axially displaced in a machine spindle (3) for actuating a clanping head (6) that cooperates with jaws (5), and for clanping a force is initially exerted in am a3d.al clanping direction on the rod (4) by means of the actuator (20) until the axial position of the rod is fixed relative to the Reaching spindle (3) as the resist of self-locking, and after self-locking is established the application of force in the clanping direction by the actuator (20) on the rod is suspended and remains suspended while the chuck is in operation^ and to release the clanp the rod (4) is displaced by the actuator (20) in a release direction that is opposite the clanping direction. 2. The method according to claim characterized in that during claiming after self-locking is established, the application of force is reduced during start-up of the machine spindle ( 3). 3* The method according to claim 1 or 2, characterized in that during release the application of force in the release direction is commenced after the nachine spindle (3) has reached a standstill. 4* An apparatus for carrying out the method according to one of claims 1 through 3, characterized in that a chuck is provided having a rod (4) supported in a machine spindle (3) so as to be axial-ly displace e in order to actuate a clanping head (6) that cooperates with jaws (5), in which the axial position of the rod (4) in the clanped position is secured by self-locking, and an actuator (20) is provided that in the clanped position of the rod (4) is decoupled from same in a positive it manner. 5. The apparatus according to claim 4, characterized in that in the clanped position of the rod (4) the actuator (20) is out of contact with the rod. 6. The apparatus according to claim 5, characterized in that the rod (4) has a first wire-wound coil (21) that cooperates with a second wire-wound coil (22) on the machine spindle (3) and coaxial with the first wire^-wound coil (21) that is coupled in a contact-free manner with a stator (24) provided on the stationary actuator housing (23). 7. The apparatus according to claim 6, characterized in that the rod (4) has an annular collar (26) provided in a piston chamber (27) of a first piston (28) that is located in a cylindrical chamber (29) of the actuator (20) that may be acted on by a pressure medium 8. The apparatus according to claim 7, characterized in that, starting from a center position, the displacement stroke of the first piston (28) in the cylindrical chamber (29) is greater in both directions than the displacement stroke of the annular collar (26) in the piston chascber (27) in both displacement directions. 9. The apparatus according to claim 7 or 8, characterized in that a second piston (31) is provided in a second cylindrical chancre (30) in the actuator (20) that bears on the first piston (28) in the clanped position of the rod (4). 10. The apparatus according to claim 9, characterized in that the second piston (31) has a larger diameter than the first piston (28), and the mutually opposing sides of the first piston (28) and the second piston (31) in the clanped position of the rod (4) are acted on with equal pressure via a three-way valve (32). 11. The apparatus according to one of claims 7 through 10, characterized in that for stroke control a ring sensor (33) is provided on the actuator (20) for interaction with an indicator (34) provided on the rod (4). 12. The apparatus according to claim 4, characterized in that the actuator (20) has a rotary feed through fitting (35) having a manifold shaft (36) connected to the arachnid spindle (3) and a rotational-ly fixed manifold housing (38) that carries pressure medium connections (37), the pressure medium connections (37) being used for applying pressure to the two sides of a piston (40) provided in a chider (39) and connected to the rod (4), 13. The apparatus according to one of clarions 7 through 12f characterized in that a spindle collar (41) having a circumflex eventual groove (42) is provided on the nachine spindle (3), and at least two diametrically opposite pins (43) engage in the groove for relieving the spindle during clasping and release, the pins being provided on the axial-ly displaceable cylinder wall (44) of the actuator (20). 14. The apparatus according to claim 13, characterized in that two springs (45) acting in the two displacement directions and supported on the housing are provided on the cylinder wall (44) in order to establish a center position of the pins (43) following clanping and release 15. The apparatus according to claim 13 or 14, characterized in that a funnel-shaped surface (46) is provided on the cylinder wall (44), and a centering element (47) is provided on the housing, in order to establish a center position of the pins (43) following clanping and release 16. The apparatus according to claim 15, characterized in that the centering element (47) is formed by a spring'-loaded ball (48). 17. The apparatus according to claim 15^ characterized in that the centering element (47) is formed by a conical pin (49) that nay be acted on by the pressure medium 18. The apparatus according to claim 7 or 8, characterized in that the first piston (28) is associated with the clanping process and bears on the annular collar (26) during calquing, and a release piston (50) that can be displaced independently of the first piston (28) and that bears on the annular collar (26) during release is provided in the actuator (20). 0PERATIN3 AN ACTUATOR AND APPARATUS FOR CARRYIMS OUT THE ^THOD The invention relates to a method of operating an actuator that is used to clanp and release a chuck having a rod that can be axially displaced in a nachine spindle for actuating a clanping head with jaws, and where to start with for clanping a force is initially exerted in an axial clanping direction on the rod by means of the actuator until the axial. position of the rod is fixed relative to the nachine spindle, and sifter self-locking is established the application of force in the clanping direction by the actuator on the rod is suspended and retains suspended while the chuck is in operation, and to release the clanp the rod is displaced by the actuator in a release direction that is opposite the clanping direction. The invention further relates to an apparatus for carrying out the method. Chucks are known from the prior art, for example from DE 140 638 Al [US 6,568,888], that by means of collet chucks are used to clanp workpiece having, for example, a collet. To actuate such chucks/ actuators, also referred to as release units, are used that axially displace a rod associated with the chuck, and to clanp the workpiece the rod is pulled in the direction away from the collet chuck and, with application of the necessary clanping force, is held in this position by the actuator, the correct positioning of the rod being assisted by spring-dasher assemblies or hike spring washers. The actuator moves the rod in the opposite direction to discontinue the clanping. Although such chucks with

Full Text

MSTHOD OP OPERATING AN ACTUATOR AMD APPARATUS FOR CARRYIN5 OUT THE

The invention relates to a method of operating an actuator that is used to clanp and release a chuck having a rod that can be axially displeured in a machine spindle for actuating a clanping head with jaws, and where to start with for clanping a force in an axial clanping direction on the rod by means of the actuator until the axial position of the rod is fixed relative to the machine spindle, and after self-locking is established the application of force in the clanping direction by the actuator on the rod is suspended and remains suspended while the chuck is in operation, and to release the clanp the rod is displaced by the actuator in a release direction that is opposite the claiming direction. The invention further relates to an apparatus for carrying out the method.
Chucks are known from the prior art, for example from DE 140 638 Al [US 6,568,888], that by means of collet chucks are used to clanp workpieces having, for example, a collet. To actuate such chucks, actuators, also referred to as release units, are used that axially displace a rod associated with the chuck, and to clanp the workpiece the rod is pulled in the direction away from the collet chuck and, with application of the necessary clanping force, is held in this position by the actuator, the correct positioning of the rod being assisted by spring washer assemblies or helical spring washers. The actuator moves the rod in the opposite direction to discontinue the clanping. Although such chucks with

associated actuators and the method required for their operation have proven to be successful in practice, the known prior art has limitations when the balance quality nuts be continually improved as rotation speeds of the spindle increases, and in particular the spring-washer asexualizes or helical. spring washers have an adverse effect since they bear continuously on the rod.
The object of the present invention, therefore, is to provide a method of operating an actuator that may be carried out in the absence of such springs. A further object of the invention is to provide an apparatus for carrying out the method.
The part of the object of the invention relating to the method is attained by use of the above-described method that is characterized in that a force need be exerted on the rod only for claiming and releasing, whereas during operation of the chuck on the machine spindle, which is rotating at high speed, it is not necessary to exert force on the rod.
In order to shorten the resetting time, for example for changing tools, it should be noted that during clanping after locking is established it is also possible to reduce the application of force during start-up of the machine swindler i. e the machine spindle may already be started, whereas the force transmission from the actuator to the rod has been suspended.
It is also within the scope of the invention, in particular from a safety standpoint, that during release the application of force in the release direction is not commenced until the machine spindle has reached a standstill; i. e only after the machine spindle has reached a complete standstill is the force

transinLssion chain between the actuator and the rod reestablished, in order to avoid injury or dotage as the result of insxifficiently clamped workpieces.
The part of the object of the invention relating to the apparatus is attained by the fact that a chuck is provided having a rod that is supported in a machine spindle so as to be axially displaceable in order to actuate a claiming head that cooperates with the jaws, the axial position of the rod in the clanped position having been secured by self-locking, and an actuator is provided that in the self-locked position of the rod is decoupled from it in a positive-fit manner. By use of this design, in particular negative effects on the balance quality caused by the part o£ the actuator necessary for actuating the rod may be prevented, and in particular so that the connection of the rod to the actuator does not adversely affect the balance quality. These advantages may be realized in a particularly simple tanner by positioning the actuator so as not to contact the rod in the clanped position of the rod, i. e so that the free-standing rod together with the entire machine spindle is able to rotate without contact with the actuating system
In one advantageous embodiment, the rod has a first wire-wound coil that is provided for interaction with a second wire-wound coil of the machine spindle and coaxial with the first wire-wound coil that is coupled in a contact-free manner with a stator of the stationary actuator housing* In principle, this design forms a linear motor that can move the rod in the calcimine

direction or the release direction as the resist of different current directions.
One very particularly preferred embodiment is characterized in that the rod has an annular collar provided in a piston chamber of a first piston that is located in a cylindrical chamber of the actuator that nay be acted on by a pressure medium In this embodiment in contrast to the embodiment that makes use of the wire-wound coils’ a contact operational method of clanping and releasing is auk-lowed’ it being ensured that the rod together with its annular collar is positioned without contact with the actuator during operation of the chuck, since this is the key criterion for achieving high rotational speeds with good balance quality, whereas during standstill, contact may be allowed for switching on the chuck.
It is also within the scope of the invention that, starting from a center position, the displacement stroke of the first piston in the cylindrical chamber is greater in both directions than the displacement stroke of the annular collar in the piston chamber in both displacement directions, so that the additional displacement capability of the first piston not only allows contact to be made between the annular collar and the piston chamber, but also allows the necessary displacement of the rod for actuation of the chuck.
It is particularly preferred when a second piston is provided in a second cylindrical chamber in the actuator that bears on the first piston in the clipped position of the rod. For proper functioning of this apparatus it is essential that the annular

collar precisely maintains the center position in the piston chattber during operation, this precise positioning being difficult to ensure solely by controlling the pressure conditions in the cylindrical chancre Use of the second piston easily provides this assurance by establishing in the clanped position the correct position of the first piston and thus the position of the annular collar in its piston chancier.
To establish the correct position of the second piston in the clasped position, the second piston has a larger effective diameter than the first piston, and the opposite sides of the first piston and the second piston in the clanped position of the rod are acted on with equal pressure via a three-way valve.
It is also within the scope of the invention that for stroke control a ring sensor is associated with the actuator for interaction with an indicator associated with the rod, so that this enibodiraent offers the possibility of monitoring the displacement of the rod for introduction of the clanping force.
A further alternative embodiment is characterized in that the actuator has a rotary feed through fitting having a manifold shaft connected to the nachine spindle and a rotationally fixed manifold housing that carries pressure medium connections that are used for applying pressure to the two sides of a piston provided in a piston chamber and connected to the rod. In this embodiment it is important that a connection to the rod occurs without contact with the actuator in any operating position during, i* e. clanping, releasing, or during operation, but that in the clanped position the actuator is decoupled from the rod in a positive-fit manner

corresponding to the above-described requirements; i. e the pressure medium connections are acted on by pressure only for switching on, and are switched on for unpressurized operation, since in particular at the desired high rotational speeds of up to 120,000 revolutions per minute the seals are subjected to increased wear under pressure lieu.
According to a further embodiment, a spindle collar having a circumferential groove is provided on the machine spindle, and at least two diametrically opposite pins engage in the groove for relieving the spindle during clanping and release, the pins being provided on the axially displaceable e cylinder wall of the actuator, and two springs acting in the two displacement directions and supported on the housing being associated with the cylinder wall in order to establish a center position of the pins following clanping and reuse
Alternatively or additionally, in order to establish a center position of the pins following clanping and release a funnel-shaped surface nay be associated with the cylinder wall, and a centering element nay be associated with the housing, in the simplest design the centering element being formed by a spring-loaded ball.
However, the centering element nay also be formed by a conical pin that nay be acted on by a pressure medium
A further embodiment having two pistons associated with the actuator is characterized in that the first piston serves for with the clanping process and bears on the annular collar during clanping, and a release piston that can be displaced independently

of the first piston and that bears on the annular collar during release is provided in the actuator.
The invention is in greater detail below with reference to the shown endDodiinents shown in the drawing. Therein:
FIG. 1 is a longitudinal section through the chuck to be operated by the actuator;
FIG. 2 is a somewhat schematic longitudinal section through a first embodiment of the actuator;
FIG. 3 is a view like Fig. 2 of a second enbodimeat of the actuator;
FIG* 4 is a view like FIG. 2, of a further embodiment of the actuator;
FIG. 5 is a view like FIG. 3 with relief of the spindle
FIG. 6 is a view like FIG* 5, in an alternative embodiment of relief of the spindly* and
FIG. 7 is a further of an actuator having two pistons.
The drawing shows a chuck used for clanping a workpiece 2 having a collet 1, or for clanping a tool, to which end the chuck has a rod 4 that is supported so as to be axially displaceable in a body 3 and that is provided for actuating a clanping head 6 that cooperates with jaws 5, namely, by axial displacement of the rod 4 between a release position shown in the lower half of FIG. 1 and a clanped position shown in the upper half of FIG. 1. The workpiece 2 is clanped by pulling the rod 4 from the release position into the clanped position by means of an actuator 20, shown in the drawing in FIGS. 2 through 4 and to be described in greater detail

by drawing back jaws 7 and a threaded bolt 8 as well as a threaded ring 9 the clanping head 6 is axial y displaced, thereby radially displacing the outer ends 10 of the jaws 5 so as to make contact with the collet 1.
In the chuck shown in FIG. 1, it is noted that a clanping sleeve 11 is provided in the body 3 so as to be axially nondisplaceable, the jaws 7 being axially guided in the clanping sleeve and having their inner faces resting against the rod 4, the rod 4 having a conical head 12, and the jaws 7 having a tapered ring 13, and the clanping sleeve 11 having an internal conical surface 14, resulting in self-locking that locks the axial position of the jaw outer ends 7 when the rod 4 moves from the release position to the clanped position, without the actuator having to exerting additional tension on the rod 4. The force applied by the actuator 20 through the rod 4 is thus stored, so to speak, by means c’ this self-locking action, and the secure clasping of the workpiece 2 at its collet 1 is ensured without having to use a tension spring that with its spring force would have to ensure the axial position of the rod 4 with respect to the body 3 or the clanping sleeve 11 in the clanped position. The security of the clanping therefore is not jeopardized by fatigue of the tension spring. In addition, as the result of using self-locking, the rod 4, which is not engaged by a tension spring, is able to rotate with the entire spindle, i. e, the body 3, without having to be connected with its actuator 20, enabling the balance quality to be improved and the rotational speed to be increased.

The drawing also shows that the conical head 12 merges with the rod 4 by a radially extending shoulder 15, and that the jaw outer ends 7 have an inner shoulder 16 for engagement with the shoulder 15, and that the jaw outer ends 7 together with their inner shoulder 16 are able to be spread by the shoulder 15 in the axi2LL region of the conical inner surface 14 of the clanking sleeve 11. In the enbodiment shown in the drawing, the conical haul 12 has an apex angle of 6E, whereas the conical inner surface 14 of
the clanping sleeve 11 has an apex angle of 12E* The inclination of the inner circumferential surface and of the outer circumflex rental surface of the tapered ring 13 correspond to the inclination of the corresponding contacting coicponents.
The operation of the apparatus is briefly y described below. Starting from the release position shown in the lower half of the figure, the actuator 20 exerts a tension on the rod 4 that moves the rod 4 to the left in the drawing. During this displacement, as a result of the contact of the inner shoulder 16 of the jaw outer ends 7 against the shoulder 15 a£ the rod 4, the rod 4 first entrains the jaw outer ends 7 that to avoid imbalance are guided relative to the clanping sleeve in two elongated holes 17, and by means of the threaded bolt 8, threaded ring 9, and clanping head 6 the jaws 5 with their jaw outer ends 10 pivot radially outward and come to rest against an undercut 18 of the collet 1. The interaction of the shoulder 15 with the inner shoulder 16 restarts in rapid axial displacement of the clanping head 6, and after traveling a predetermined axial distance the inner shoulder 16 of the jaws 7 is able to disengage from the

shoulder 15, and with the inner surface of the tapered ring 13 comes to rest against the conical head 12 while at the same time being pressed with the outer circumferential surface agar’s the tapered ring 13 of the clipping sleeve’s 11. The jaws 7 are thus carried along in the axial direction only to a slight degree during continued axial. displacement of the rod 4, but with increasing force between the conical head 12 and the clanping sleeve 11 the jaws are wedged until self-locking is attained that provides the established clanping force when the tension from the actuator 20 is no longer applied to the rod 4.
To release the chuck, the rod 4 is moved to the right from the clipped position to the release position, thereby unlocking the jaws 7 from the wedged conical head 12 and the claiming sleeve 11 and also displacing the rod 4 relative to the jaws 7 until the rod =s contact surface 19 come to rest against the threaded ring 9’ and the inner shoulder 16 is once more able to engage behind the shoulder 15 of the rod 4. Continued movement of the rod 4 displaces the clipping head 6, causing the jaws 5 with their jaw outer ends 10 to release the 2.
The clanping and release of this chuck may optionally be acconplished by use of one of the actuators 20 shown in FIGS. 2 through 4 that are all characterized in that the force transmission chain from the actuator 20 to the rod 4 is interrupted in the clanped position of the rod 4. In the embodiments of FIGS. 2 and 3 this is accoziplished by the fact that in the clanped position of the rod 4 the actuators 20 are out of contact with the rod, whereby in the embodiment in FIG. 2, the rod 4 is provided with a first

wire’wound coil 21 that is provided for interaction with a second wire-wound coil 22 carried on the machine spindle 3, coaxiaaiy surrounding with the first wire’wound coil 21, and coupled in a contact-free scanner with a stator associated with the stationary actuator housing 20 [23], This actuator 20 acts in a contact-free manners on the rod 4 in eJ.1 operating positions for calquing and releasing as well as during operation of the chuck when the latter is rotated together with the machine spindle 3 at high speeds.
FIG* 3 shows in which the rod 4 has an annular collar 26 that is provided in a piston chairiber 27 of a first piston 28 that is located in a cylindrical charier 29 of the actuator that inlay be acted on by a pressure median the displacement stroke of the first piston 28 in the cylindrical chairiber 29/ starting from a center position, being greater in both directions than the displacement stroke of the annular collar 26 in the piston chairiber 27 in both displacement directions, so that in addition to the displacement of the first piston 28 for contacting the annular collar 26 with the axial end and back faces of the piston chairiber, the continued displacement nay force actuation of the clanping head 6. However, to ensure that contact with the end and back faces of the piston chamber 27 is once again released for the annular collar 26 when the rod 4 has assumed its working position after achieving self-locking, a second piston 31 is provided in a second cylindrical chairiber 30 in the actuator 20 that acts on the first piston 28 in the clanped position of the rod 4, the second piston 31 having a larger effective diameter than the

first piston 28, and the mutually opposing sides of the first piston 28 and the second piston 31 in the clanped position of the rod 4 being acted on with equal pressure via a three-way valve 32, so that the larger effective surface of the second piston 31 ensures contact thereof with the first piston 28, and contact of the second piston 31 with the end face of the second cylindrical chanber 30 is ensured to set the center position of the annular collar 26* In this embodiment, for stroke control a ring sensor 33 is associated with the actuator 20 for interaction with an indicator 34 carried on the rod.
FIG. 4 shows a further embodiment in which the actuator 20 has a rotary feed through fitting 35 having a manifold shaft 36 connected to the nachine spindle 3 and a rotationally fixed manifold housing 38 that carries pressure medium connections 37, the pressure medium connections 37 being used for Appl’ ng pressure to the two sides of a piston 40 provided in a chairiber 39 and connected to the rod 4, in this einbodiment the rod 4 having no contact with the actuator 20 in any operating position, but, rather, the desired interruption of the force transmission chain being provided during operation of the chuck, since after self-locking is established the pressure medium connections 37 may be d
In ell the embodiments in FIGS, 2 through 7, also associated with the actuator 20 at its axial end is a supply device 25 that may be used for supplying air or a coolant for the rod 4 into the chuck.

FIG. 5 shows an exibodixnent in which a spindle collar 41 having a circumflex eventual groove 42 is provided on the neighing spindle 3, and at least two diametrically opposite pins 43 engage in the groove for relieving the spindle during clanping and release, the pins being provided on the axially displaceable cylinder wall 44 of the actuator 20, and two springs 45 acting in the two displacement directions and supported on the housing being provided on the cylinder W2LL1 44 in order to urge the pins 43 into a center position following clanping and release’* in contrast, FIG. 6 shows an that nay be used for assistance, in which in order to center the pins 43 following clanping and release a funnel-shaped surface 46 is associated with the cylinder wall 44, and a centering element 47 is associated with the housing, the centering element being formed either by a spring-loaded ball 48 (FIG. 5) or by a conical pin 49 that nay be acted on by the pressure medium
Finally, FIG. 7 shows an embodiment in which, although two pistons are associated with the actuator 20, they do not act independently namely, the first piston 28 is associated with the clanping process and bears on the annular collar 26 during clanping, and a release piston 50 that can be displaced independently of the first piston 28 and that bears on the annular collar 26 during release is provided in the actuator 20.

Claims:
1. A method of operating an actuator (20) that is used to clap and release a chuck having a rod that can be axially displaced in a machine spindle (3) for actuating a clanping head (6) that cooperates with jaws (5), and for clanping a force is initially exerted in am a3d.al clanping direction on the rod (4) by means of the actuator (20) until the axial position of the rod is fixed relative to the Reaching spindle (3) as the resist of self-locking, and after self-locking is established the application of force in the clanping direction by the actuator (20) on the rod is suspended and remains suspended while the chuck is in operation^ and to release the clanp the rod (4) is displaced by the actuator (20) in a release direction that is opposite the clanping direction.
2. The method according to claim characterized in that during claiming after self-locking is established, the application of force is reduced during start-up of the machine spindle ( 3).
3* The method according to claim 1 or 2, characterized in that during release the application of force in the release direction is commenced after the nachine spindle (3) has reached a standstill.
4* An apparatus for carrying out the method according to

one of claims 1 through 3, characterized in that a chuck is provided having a rod (4) supported in a machine spindle (3) so as to be axial-ly displace e in order to actuate a clanping head (6) that cooperates with jaws (5), in which the axial position of the rod (4) in the clanped position is secured by self-locking, and an actuator (20) is provided that in the clanped position of the rod (4) is decoupled from same in a positive it manner.
5. The apparatus according to claim 4, characterized in that in the clanped position of the rod (4) the actuator (20) is out of contact with the rod.
6. The apparatus according to claim 5, characterized in that the rod (4) has a first wire-wound coil (21) that cooperates with a second wire-wound coil (22) on the machine spindle (3) and coaxial with the first wire^-wound coil (21) that is coupled in a contact-free manner with a stator (24) provided on the stationary actuator housing (23).
7. The apparatus according to claim 6, characterized in that the rod (4) has an annular collar (26) provided in a piston chamber (27) of a first piston (28) that is located in a cylindrical chamber (29) of the actuator (20) that may be acted on by a pressure medium
8. The apparatus according to claim 7, characterized in that, starting from a center position, the displacement stroke of

the first piston (28) in the cylindrical chamber (29) is greater in both directions than the displacement stroke of the annular collar (26) in the piston chascber (27) in both displacement directions.
9. The apparatus according to claim 7 or 8,
characterized in that a second piston (31) is provided in a second
cylindrical chancre (30) in the actuator (20) that bears on the
first piston (28) in the clanped position of the rod (4).
10. The apparatus according to claim 9, characterized in that the second piston (31) has a larger diameter than the first piston (28), and the mutually opposing sides of the first piston (28) and the second piston (31) in the clanped position of the rod (4) are acted on with equal pressure via a three-way valve (32).
11. The apparatus according to one of claims 7 through 10, characterized in that for stroke control a ring sensor (33) is provided on the actuator (20) for interaction with an indicator (34) provided on the rod (4).
12. The apparatus according to claim 4, characterized in that the actuator (20) has a rotary feed through fitting (35) having a manifold shaft (36) connected to the arachnid spindle (3) and a rotational-ly fixed manifold housing (38) that carries pressure medium connections (37), the pressure medium connections (37) being used for applying pressure to the two sides of a piston (40)

provided in a chider (39) and connected to the rod (4),
13. The apparatus according to one of clarions 7 through
12f characterized in that a spindle collar (41) having a
circumflex eventual groove (42) is provided on the nachine spindle (3), and at least two diametrically opposite pins (43) engage in the groove for relieving the spindle during clasping and release, the pins being provided on the axial-ly displaceable cylinder wall (44) of the actuator (20).
14. The apparatus according to claim 13, characterized in that two springs (45) acting in the two displacement directions and supported on the housing are provided on the cylinder wall (44) in order to establish a center position of the pins (43) following clanping and release
15. The apparatus according to claim 13 or 14, characterized in that a funnel-shaped surface (46) is provided on the cylinder wall (44), and a centering element (47) is provided on the housing, in order to establish a center position of the pins (43) following clanping and release
16. The apparatus according to claim 15, characterized in that the centering element (47) is formed by a spring'-loaded ball (48).
17. The apparatus according to claim 15^ characterized

in that the centering element (47) is formed by a conical pin (49) that nay be acted on by the pressure medium
18. The apparatus according to claim 7 or 8, characterized in that the first piston (28) is associated with the clanping process and bears on the annular collar (26) during calquing, and a release piston (50) that can be displaced independently of the first piston (28) and that bears on the annular collar (26) during release is provided in the actuator (20).

0PERATIN3 AN ACTUATOR AND APPARATUS FOR CARRYIMS OUT THE
^THOD
The invention relates to a method of operating an actuator that is used to clanp and release a chuck having a rod that can be axially displaced in a nachine spindle for actuating a clanping head with jaws, and where to start with for clanping a force is initially exerted in an axial clanping direction on the rod by means of the actuator until the axial. position of the rod is fixed relative to the nachine spindle, and sifter self-locking is established the application of force in the clanping direction by the actuator on the rod is suspended and retains suspended while the chuck is in operation, and to release the clanp the rod is displaced by the actuator in a release direction that is opposite the clanping direction. The invention further relates to an apparatus for carrying out the method.
Chucks are known from the prior art, for example from DE 140 638 Al [US 6,568,888], that by means of collet chucks are used to clanp workpiece having, for example, a collet. To actuate such chucks/ actuators, also referred to as release units, are used that axially displace a rod associated with the chuck, and to clanp the workpiece the rod is pulled in the direction away from the collet chuck and, with application of the necessary clanping force, is held in this position by the actuator, the correct positioning of the rod being assisted by spring-dasher assemblies or hike spring washers. The actuator moves the rod in the opposite direction to discontinue the clanping. Although such chucks with

Documents:

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Patent Number

269005

Indian Patent Application Number

1230/CHENP/2008

PG Journal Number

40/2015

Publication Date

02-Oct-2015

Grant Date

28-Sep-2015

Date of Filing

12-Mar-2008

Name of Patentee

ROHM GMBH

Applicant Address

HEINRICH-ROHM-STRASSE 50, 89567 SONTHEIM, GERMANY

Inventors:

#	Inventor's Name	Inventor's Address
1	HANGLEITER, EUGEN	KRONENSTRASSE 3, 89268 HERMARINGEN, GERMANY

PCT International Classification Number

B23B31/26

PCT International Application Number

PCT/DE06/01017

PCT International Filing date

2006-06-14

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	102005048800.5	2005-10-10	Germany
2	102005043722.2	2005-09-13	Germany