Clamping device and method for clamping a workpiece

Abstract

Clamping device (10) for clamping a workpiece (11), comprising a first clamping jaw (15) on a first clamping jaw carrier (13) and a second clamping jaw (16) on a second clamping jaw carrier (14), comprising a base part (12) on which the two clamping jaw carriers (13, 14) are movably mounted in an axial direction (R), comprising a spindle (20) rotatably mounted about a spindle axis (A), the spindle having a first spindle section (21) and a second spindle section (22), wherein the first clamping jaw carrier (13) is arranged on the first spindle section (21) and the second clamping jaw carrier (14) is arranged on the second spindle section (22), which move towards or away from each other in the axial direction (R) when the spindle (20) is rotated about the spindle axis (A), wherein the two spindle sections (21, 22), the two clamping jaw carriers (13, 14) and the two The clamping jaws (15, 16) are arranged symmetrically to a central plane (M),wherein the median plane (M) between the two clamping jaws (15, 16) is arranged perpendicular to the spindle axis (A), wherein the two spindle sections (21, 22) are mounted to be movable relative to each other in the axial direction (R) along the spindle axis (A), and with a drive device (34) which is configured to effect the axial movement of the two spindle sections (21, 22) without rotation of the spindle (20) such that the axial movement of the spindle sections (21, 22) moves the two clamping jaws (15, 16) between a release position in which the workpiece (11) can be inserted and removed between the clamping jaws (15, 16) and a clamping position in which the workpiece (11) is clamped between the clamping jaws (15, 16) and such that the axial movement of the spindle sections (21, 22) and the two clamping jaws (15, 16) always occurs symmetrically to the median plane (M).

Description

The invention relates to a clamping device and a method for clamping a workpiece between two opposite clamping jaws of the clamping device.Clamping devices which are constructed in a similar manner to a vice are known in a variety of configurations. For example, DE 29 43 892 A1 discloses a clamping device with a rotatably mounted spindle, which has a first spindle section and a second spindle section. A body is arranged on each spindle section via a respective thread. During a rotation of the spindle, the two bodies move towards or away from each other. Pivotable holding elements with prisms are seated on the bodies in order to be able to receive a cylindrical workpiece between the prisms. With a known workpiece diameter, the bodies are adjusted via the spindle and subsequently the holding and releasing of the cylindrical workpiece can be carried out by the pivoting movement of the prisms.DE 196 21 754 A1 describes a clamping device with a divided spindle. On each spindle part, a spindle nut is arranged, which serves as a clamping jaw carrier. Each jaw carrier carries a jaw. The two spindle parts are coupled to one another via a force booster. The force booster can be actuated via a push rod. The push rod is connected via a coupling to a rotary drive of the spindle. If the spindle is rotated, a clamping jaw first bears against a workpiece. The entire spindle then performs an axial movement until the second clamping jaw also abuts the workpiece. Since the clamping jaws can then no longer move any further, a continued rotation of the spindle leads to a disengagement of the clutch and to the actuation of the push rod, which in turn actuates the force booster, which contracts the two spindle sections via a hydraulic pressure.The clamping device known from DE 41 05 425 A1 operates similarly. Here again, a split spindle is provided, each spindle part serving to axially displace a jaw when the spindle is rotated. When both clamping jaws abut a workpiece, a coupling is released and a continued rotation of a shaft causes a mechanical force amplification which presses the two spindle parts against each other.Proceeding from this, it can be considered an object of the invention to provide a clamping device or a method which enables simple, automated clamping of a workpiece and can be adapted flexibly to different workpieces.This object is achieved by a clamping device having the features of patent claim 1 and by a method having the features of patent claim 14.The clamping device has a first clamping jaw present on a first clamping jaw carrier and a second clamping jaw present on a second clamping jaw carrier. The two clamping jaw carriers are mounted on a base part of the clamping device so as to be movable in an axial direction parallel to a spindle axis of a spindle. Each jaw carrier is seated on an associated spindle section of the spindle. During a rotation of the spindle, the two clamping jaw carriers and thus the clamping jaws move towards one another or away from one another in the axial direction, depending on the direction of rotation of the spindle. In this case, the clamping jaw carriers and the clamping jaws move relative to one another and relative to the base part. The clamping jaw carriers are not displaceable along the respective spindle section and can only move relative to the spindle during the rotation thereof. In particular, each spindle section has an external thread which is in engagement with an associated internal thread of the respective clamping jaw carrier.The clamping jaw carrier and the clamping jaw arranged thereon can be integrally embodied in one piece or in multiple pieces.The spindle is divided. The two spindle sections are movable relative to one another in the axial direction and are in particular mounted displaceably. They can execute an axial movement toward or away from each other, wherein this axial movement of the spindle sections is transmitted to the clamping jaw carriers and the clamping jaws to the same extent. By means of a drive device, the axial movement of the two spindle sections is effected. In a preferred exemplary embodiment, the drive device is electrically and / or fluidically and / or mechanically controllable or driven for this purpose.An axial movement or an axial stroke of the two clamping jaws can thus be brought about by way of the drive device for clamping a workpiece toward one another or for releasing a clamped workpiece away from one another. By rotating the spindle, the distance between the two clamping jaws can be adjusted so that the respective workpiece can be inserted. The stroke for clamping the workpiece is then carried out by the drive device. The detachment of the workpiece is also initiated via the drive device. Therefore, similar workpieces can be clamped quickly and easily in the clamping device without having to rotate the spindle. The conversion of the clamping device for clamping workpieces having a different dimension can be carried out quickly and easily by positioning the clamping jaws by means of the spindle. The conversion time of a machine tool to the machining of other workpieces is therefore short.The two clamping jaws each have the same distance from a central plane. The central plane is oriented at right angles to the spindle axis or the axial direction and runs between the two clamping jaws. The workpiece is thus always clamped centrally.In each case, a spindle section, the clamping jaw carrier mounted on the spindle section and the clamping jaw arranged on the clamping jaw carrier belong in each case to a clamping unit. The clamping device thus has two clamping units which are movable relative to one another in the axial direction. The components of a clamping unit move together and not relative to one another during a movement caused by the drive device.The axial movement of the spindle sections or of the two clamping jaw carriers and of the two clamping jaws always takes place symmetrically to the central plane.It is advantageous if the two spindle sections are rotationally coupled to one another by a rotational coupling device in the rotational direction about the spindle axis. This ensures that, during a rotation of one of the two spindle sections of the spindle, the same rotational movement is carried out by the respective other spindle section. The rotational coupling device for coupling the two spindle sections in the rotational direction about the spindle axis is preferably always effective, regardless of whether the drive device moves the spindle sections or the clamping jaws toward or away from each other or the clamping jaws assume a clamping position or release position effected by the drive device. The rotational coupling device is designed in such a way that the axial movement is also made possible in the case of existing rotational coupling.In one exemplary embodiment, the rotary coupling device has at least one coupling projection which engages in an associated coupling recess. The coupling projection is present on the one spindle section and projects substantially in the axial direction toward the respective other spindle section and engages there in an associated coupling recess. A plurality of coupling projections and / or coupling recesses can be present on a respective spindle section.It is preferred if the at least one coupling projection and the at least one associated coupling recess are arranged at a distance from the spindle axis. The coupling projection and the coupling recess can support a greater torque about the spindle axis with increasing distance from the spindle axis. The coupling projections and the coupling recesses can be circular in cross section, for example.It is also advantageous if the drive device has a prestressing arrangement which indirectly or directly generates a prestressing force on the two spindle sections, which prestressing force acts parallel to the spindle axis in the axial direction. The prestressing force can urge the two spindle sections away from one another in an exemplary embodiment, i.e. in the direction of the release position of the clamping jaws. It is also possible for the prestressing force to urge the two spindle sections towards one another in the direction of clamping a workpiece, that is to say in the direction of the clamping position of the clamping jaws.The pretensioning arrangement is preferably formed by mechanical means for generating the pretensioning force, for example by a spring arrangement. In one exemplary embodiment, a spring and in particular a helical spring can be arranged between the two spindle sections. The prestressing force can preferably act directly on the spindle sections. Alternatively, it is also possible to exert the prestressing force on the clamping jaw carriers or the clamping jaws.In the exemplary embodiment, the drive device has an actuatable actuating unit which is configured to move the two spindle sections and / or the two clamping jaw carriers and / or the two clamping jaws in the axial direction counter to the prestressing force. In one embodiment, the actuating unit can act directly on the two spindle sections, the axial movement of which is carried out together with the two clamping jaw carriers and the two clamping jaws.The actuating unit can have a force generating unit, in particular a fluid cylinder and in one exemplary embodiment a pneumatic cylinder. Preferably, the force generating unit is coupled to the two spindle sections via a transmission arrangement. A single force generating unit may be sufficient. The actuating unit can also be mechanically actuated by an external force generating unit, for example a gripper, a robot arm or a machine element.The transmission arrangement can have one drive part and two driven parts. The driving part is motion-coupled to the force generation unit. The first output member is coupled to the first spindle portion and the second output member is coupled to the second spindle portion. The drive part is also coupled to the two driven parts, so that a movement of the drive part is transmitted via the two driven parts to the respectively acted upon spindle section. This makes it possible to ensure that the two spindle sections execute movements of equal magnitude in the axial direction and that the distance of the two spindle sections and therefore of the two clamping jaws from the central plane is in each case of equal magnitude.In one embodiment, the two spindle sections each have a flange at their ends assigned to one another, on which flange the respectively assigned output part engages.The drive part in a preferred embodiment has a first drive surface and a second drive surface. The drive surfaces are inclined with respect to the central plane or the spindle axis. A respective free end of the output parts abuts a respective drive surface of the drive part. The distance between the two drive surfaces increases in one direction of movement of the drive part and decreases in the opposite direction of movement. As a result, the two free ends of the output parts can be moved towards or away from one another.It is advantageous if the two output parts are mounted on the base part such that they can be pivoted about a pivot axis in each case. The pivot axes are preferably parallel to one another. The pivot axes are further preferably oriented at right angles to the spindle axis.At least one elevation is present on each driven part and / or each spindle section, said elevation forming a contact point between the first spindle section or the second spindle section and the first driven part or second driven part acted upon by the first spindle section or by the second spindle section. As a result, a defined contact point between the relevant output part and the associated spindle section can be predefined, in particular if the output part is mounted pivotably.With the aid of this clamping device, workpieces of the same type can be clamped very easily:First, the distance between the two clamping jaws, which are located in a position at maximum distance by the drive device (release position), is adjusted by rotating the spindle such that a workpiece can be inserted between the clamping jaws preferably in an automated manner. Subsequently, the workpiece to be machined can be placed between the clamping jaws and, with the aid of the drivable drive device for clamping the workpiece, an axial movement of the two spindle sections-and therefore of the two clamping jaws-towards one another can be carried out, so that the clamping jaws are in the clamping position. After the workpiece machining, the drive device carries out an axial movement of the two spindle sections or clamping jaws away from each other, back into the release position. The processed workpiece can be removed and the next workpiece can be inserted, in particular automatically by means of a gripper or transfer device.In this way, workpieces of the same type can be clamped in succession very quickly. If workpieces of a different type are to be machined which have a different dimension, it is merely necessary to readjust the release position of the clamping jaws via the spindle. Refitting can take place quickly and easily.Advantageous embodiments of the clamping device and of the method are evident from the dependent patent claims, the description and the drawings. Preferred exemplary embodiments of the invention are explained in detail below with reference to the attached drawings. The following are shown: FIG. 1 shows an exemplary embodiment of a clamping device in a schematic illustration similar to a block diagram, FIG. 2 shows a schematic block diagram-like illustration of an exemplary embodiment of the spindle in a sectional partial illustration, FIG. 3 shows a schematic illustration of the force transmission of a force of a drive device of the clamping device to the spindle sections for generating an axial movement or a clamping force, FIG. 4 is a perspective view of an embodiment of an output member used for transmitting the movement of an input member to a spindle portion of an embodiment of the clamping device, FIG. 5 shows the output part from FIG. 4 in a cross section and an exemplary embodiment of a spindle section which is assigned to the output part, FIG. 6 shows the two output parts of an exemplary embodiment of a clamping device in cross section with the spindle sections acting on them and a drive part of the clamping device, FIG. 7 shows the exemplary embodiment of the clamping device in a plan view at right angles to a spindle axis of the spindle of the clamping device.Exemplary embodiments of a clamping device 10 for clamping a workpiece 11 or parts of the clamping device 10 are illustrated in the drawings. The clamping device 10 has a base part 12 which serves, for example, for fastening to a machine table, machine slide or the like of a machine tool. For this purpose, fastening means, not illustrated in more detail, can be present on the base part 12. A first clamping jaw carrier 13 and a second clamping jaw carrier 14 are mounted on the base part 12 so as to be displaceable in an axial direction R. A first clamping jaw 15 is arranged on the first clamping jaw carrier 13 and a second clamping jaw 16 is arranged on the second clamping jaw carrier 14. Each clamping jaw 15, 16 has a clamping surface 17. The two clamping jaws 15, 16 are situated opposite each other in the axial direction R, so that the clamping surfaces 17 face each other. The workpiece 11 can be clamped between the two clamping surfaces 17 of the two clamping jaws 15, 16 and held for machining.The two clamping jaw carriers 13, 14 are preferably movable only in a single degree of freedom, namely in the axial direction R. All further degrees of freedom are preferably accommodated as free of play as possible by the guide between the base part 12 and the two clamping jaw carriers 13, 14.The two clamping jaw carriers 13, 14 are motion-coupled to one another via a spindle 20. The spindle 20 extends along a spindle axis A which is oriented in the axial direction R. The spindle 20 has a first spindle section 21 and a second spindle section 22, the spindle 20 is connected to the first clamping jaw carrier 13 by means of the first spindle section 21, and the spindle 20 is connected to the second clamping jaw carrier 14 by means of the second spindle section 22. The clamping jaw carriers 13, 14 are held displaceably in the axial direction R relative to their respective spindle section 21, 22 in the working state of the clamping device 10. A relative movement between a respective clamping jaw carrier 13, 14 and the associated spindle section 21 or 22 can be caused by the spindle 20 being rotated about its spindle axis A in a circumferential direction U. Depending on the direction of rotation, the two clamping jaw carriers 13, 14 move towards one another or away from one another in the axial direction R. In this way, the distance between the two clamping jaw carriers 13, 14 or the two clamping jaws 15, 16 can be adjusted in the axial direction R.In the exemplary embodiment, the two spindle sections 21, 22 have an external thread which is in engagement with a respective internal thread of the associated clamping jaw carrier 13, 14. The thread pitch is selected such that self-locking occurs, so that no rotation of the spindle 20 can be caused by a force acting in the axial direction R on the two clamping jaw carriers 13, 14. In the exemplary embodiment, the two spindle sections 21, 22 have different rotational directions, so that during a rotation of the entire spindle 20, both clamping jaw carriers 13, 14 respectively cover the same path away from each other or towards each other. For example, the first spindle section 21 can have a right-hand thread and the second spindle section 22 can have a left-hand thread or vice versa.The two spindle sections 21, 22 are designed as separate clamping jaw carriers and can execute an axial movement along the spindle axis A in the axial direction R with a predetermined maximum stroke. The length of the stroke depends on the specific construction and can be, for example, a few millimeters or else a few centimeters. By means of this axial movement, the clamping and releasing of a workpiece 11 can be carried out without rotation of the spindle 20.The two spindle sections 21, 22 each have an outer end 23, at which an engagement element 24 or an operating element can be present in order to be able to rotate the spindle 20. In the exemplary embodiment illustrated here, the engagement element 24 can be formed by an external hexagon, by an internal hexagon or the like. The spindle 20 can be driven manually or also by servo motors in order to adjust the relative position of the two clamping jaws 15, 16 and to adapt it to the dimension of a workpiece 11 to be clamped.At their inner end 25 opposite the outer end 23, the spindle sections 21, 22 each have a flange 26. The two spindle sections 21, 22 are coupled in rotational movement with the two inner ends 25 by means of a rotational coupling device 27 in the circumferential direction U about the spindle axis A. The rotary motion coupling effected by means of the rotary coupling device 27 is always effective, regardless of whether a workpiece 11 is clamped in or not. The rotational coupling is effective during the entire maximum possible path of the axial movement between the release position and the clamping position.In the exemplary embodiment, the rotary coupling device 27 has at least one coupling projection 28 and at least one associated coupling recess 29. The rotary coupling device 27 can be seen in particular in FIG. 2. According to the example, at least two coupling projections 28 are provided, which are each arranged at a distance radially offset to the spindle axis A. The coupling projections 28 are formed by cylindrical pins in the example shown here. The coupling projections 28 extend parallel to the spindle axis A in the axial direction R away from the inner end 25 or from the flange 26.Adapted to the contour or the cross section of the coupling projections 28, cylindrical coupling recesses 29 are present in the respective other spindle section according to the example, which are likewise arranged at a distance from the spindle axis A. The coupling recesses 29 are designed as blind holes which open out at the inner end 25.In the exemplary embodiment shown here, the coupling projections 28 are present on one and, according to the example, the first spindle section 21, while the coupling recesses 29 are present on the respective other and, according to the example, the second spindle section 22. Alternatively, it would also be possible to arrange one or more coupling projections 28 on each of the spindle sections 21, 22, each of which coupling projections would then be provided with a coupling recess 29 and a respectively assigned one on the respectively other spindle section.The coupling projections 28 are preferably arranged uniformly distributed about the spindle axis A. The greater the distance from the spindle axis A, the greater the torque that the rotary coupling device 27 can absorb.The clamping device 10 also has a drive device 34. the drive device 34 is configured to effect the axial movement of the two spindle sections 21, 22. During the axial movement brought about by the drive device 34, each spindle section 21 moves together with the associated clamping jaw carrier 13 or 14 and the associated clamping jaw 15 or 16. in other words, the first spindle section 21, the first clamping jaw carrier 13 and the first clamping jaw 15 form a clamping unit and the second spindle section 22, the second clamping jaw carrier 14 and the second clamping jaw 16 form a further clamping unit, wherein each clamping unit executes the stroke movement brought about by the drive device 34. In this case, no relative movement of the components 21, 13, 15 or 22, 14, 16 relative to one another takes place within a clamping unit.The drive device 34 includes a pretensioning arrangement 35. the pretensioning arrangement 35 is configured to exert a pretensioning force FV indirectly or directly on the two spindle sections 21, 22. In the exemplary embodiment described here, the prestressing arrangement 35 acts directly on the two spindle sections 21, 22.In the exemplary embodiment, the prestressing arrangement 35 has a spring arrangement with at least one spring 36 or is formed by the spring arrangement. In the exemplary embodiment shown here, a single spring 36 in the form of a helical spring is present, which is arranged between the two spindle sections 21, 22 and presses the two spindle sections 21, 22 away from one another by the respective prestressing force FV. The prestressing force FV is therefore directed in the exemplary embodiment in such a way that it urges the two spindle sections 21, 22 away from one another, as a result of which the two clamping jaws 15, 16 are urged into the release position. In a modification to the exemplary embodiment shown, it is also possible to generate the prestressing force FVin such a way that the two spindle sections 21, 22 are forced toward one another and the clamping jaws 15, 16 are thereby forced into the clamping position.The spring 36 is arranged with its two end sections in a central recess 37 of the first spindle section 21 or of the second spindle section 22, respectively. The two central recesses 37 are arranged coaxially to the spindle axis A and open at the respective end 25. The spring 36 is loaded under pressure, for example. As already explained, the spring 36 could also be loaded under tension in order to pull the two spindle sections 21, 22 against one another by the prestressing force FV.In the exemplary embodiment, the prestressing arrangement 35 or the prestressing force FV acts directly on the spindle sections 21, 22. In other exemplary embodiments, the prestressing force FV could also act directly on the clamping jaw carriers 13, 14 and / or the clamping jaws 15, 16 by means of the prestressing arrangement 35.The drive device 34 also has an actuatable actuation unit 40. the actuation unit 40 can be actuatable electrically and / or fluidically and / or mechanically and can have an electrical and / or fluidic force generation unit. In the exemplary embodiment, the actuating unit 40 has, as a force-generating unit, a pneumatic cylinder 41 which is designed as a single-acting cylinder. As a modification, the pneumatic cylinder 41 could also be designed as a double-acting cylinder.A piston 42 of the pneumatic cylinder 41 is connected to a driving part 44 via a piston rod 43. The drive part 44 is movable at right angles to the axial direction R by means of the pneumatic cylinder 41. By supplying a working chamber of the pneumatic cylinder 41 with compressed air via a pneumatic line 45, the piston rod 43 can be extended and the drive part 44 can be moved away from the pneumatic cylinder 41 and, according to the example, toward the spindle axis A. In the exemplary embodiment, an unlockable nonreturn valve 46 is seated in the pneumatic line 45, the pneumatic pressure in the working chamber of the pneumatic cylinder 41 is maintained by the nonreturn valve 46. According to the example, the check valve 46 can be unlocked via a control line 47 when an air pressure is applied to the control line 47. Then, the air can escape from the working chamber of the pneumatic cylinder 41 via the pneumatic line 45.Instead of the pneumatic cylinder 41, a hydraulic cylinder could also be used. It is also possible to use an electric motor as the force generating unit. Furthermore, an external force generating unit can also be used for moving or actuating the drive part 44, for example a gripper or a robot arm or another movable machine part of a machine on which the machining device 10 is arranged.The actuating unit 40 also has a transmission arrangement 50, by means of which the pneumatic cylinder 41 is coupled to the two spindle sections 21, 22 in order to convert the movement of the piston 42 into an axial movement of the spindle sections 21, 22. The transmission arrangement 50 includes the drive part 44 and a first driven part 51 and a second driven part 52, and the two driven parts 51, 52 bear on the one hand on the drive part 44 and on the other hand on the respectively associated spindle section 21 or 22. According to the example, at least one contact point 53 is formed between a respective output part 51 or 52 and the associated flange 26.The first output part 51 is mounted on the base part 12 such that it can be pivoted about a first pivot axis S 1 and the second output part 52 is mounted on the base part 12 such that it can be pivoted about a second pivot axis S 2. The two pivot axes S 1, S 2 are aligned parallel to one another. The two pivot axes S 1, S 2 extend at right angles to the axial direction R or to the spindle axis A. The two pivot axes S 1, S 2 are arranged at a distance from the spindle axis A on the side opposite the drive part 44. At the free end 54 of an output part 51, 52 opposite the pivot axis S 1 or S 2, each output part 51, 52 abuts the input part 44. In particular, the free end 54 of the first output part 54 abuts a first drive surface 55 of the drive part 44 and the free end 54 of the second output part 52 abuts a second drive surface 56 of the drive part 44. The two drive surfaces 55, 56 are inclined by an angle of inclination α relative to the spindle axis A or a center plane M. The central plane M extends at right angles to the spindle axis A centrally between the two spindle sections 21, 22 or between the two clamping jaws 15, 16 or their clamping surfaces 17. The distance between the two drive surfaces 55, 56 at right angles to the central plane M increases in the direction of the clamping axis A. The intermediate space between the two drive surfaces 55, 56 expands, so to speak, in the direction of the spindle axis A.In the exemplary embodiment described here, the drive surfaces 55, 56 are designed as planar surfaces. As a modification to this, the drive surfaces 55, 56 could also be concave or convex at least in sections.An exemplary embodiment for the output parts 51 and 52 is illustrated schematically in perspective in FIG. 4. The output parts 51, 52 are arranged mirror-symmetrically to the central plane M and preferably configured identically.The driven members 51, 52 have a plate-shaped plate member 60 having a through hole 61. The through hole 61 is smaller than the flange 26 of a spindle section 21, 22 at least in a radial direction radially with respect to the spindle axis A, so that the flange 26 cannot be moved along the spindle axis A through the through hole 61. Around the through hole 61, an annular step is formed, for example, with an annular surface 62 annularly surrounding the spindle axis A. The annular surface 62 faces the flange 26 of the associated spindle section 21 or 22. According to the example, the annular surface 62 does not extend in a single plane but extends starting from two elevations 63 diametrically opposite the spindle axis A, at least in sections, inclined. The elevations 63 form elevations which are rounded by a radius and which each define a contact point 53 between the output parts 51, 52 and the associated flange 26 of the relevant spindle section 21, 22. Preferably, the two elevations 63 and the contact points 53 formed thereby are located in a common plane which is aligned at right angles to the central plane M and, according to the example, runs along or at a slight distance from the spindle axis A.In FIG. 5, the annular surface 62 with the elevation 63 which forms an abutment point 53 can be seen more clearly in cross section through the relevant output part 51, 52 than in the perspective illustration in FIG. 4. the elevation 63 and the abutment point 53 formed thereby are illustrated in a highly schematic manner in FIG. 3.The elevation 63 has the effect that the contact point 53 on the flange 26 does not travel away from the spindle axis A or toward the spindle axis A during the pivoting movement of the output parts 51, 52, but remains positioned substantially at a defined point on the flange 26. The introduction of force therefore takes place at a defined point on the flange 26.The plate part 60 is extended by two extensions 64 extending in opposite directions along the respective pivot axis S 1, S 2. In the exemplary embodiment, the extensions 64 serve to be mounted in each case in a bearing recess 65 on the base part 12 (FIG. 7 ) such that it can be pivoted about the respective pivot axis S 1 or S 2. The plate part 60 can pivot about the respective pivot axis S 1, S 2. The free end 54 of the driven part 51 or 52 is located on the side of the through hole 61 opposite the extensions 64.A sliding friction point can be provided between the free end 54 and the respectively associated drive surface 55, 56. Alternatively, it is also possible to provide a rolling body, a roller or the like in the region of the respective free end 54 of the output parts 541, 52 in order to form a rolling bearing point between the input part 44 and the two output parts 51, 52. The provision of a rolling body 66 is illustrated in a highly schematic manner in FIG. 6.The mode of operation of the clamping device 10 can be explained with reference to FIGS. 1 and 3.In FIGS. 1 and 3, the clamping jaws 15, 16 are in their release position, into which they are forced by the pretensioning arrangement 35. The two spindle sections 21, 22 have their maximum distance. The two spindle sections 21, 22, the two clamping jaw carriers 13, 14 and the two clamping jaws 15, 16 are arranged symmetrically to the central plane M. The workpiece 11 can be inserted between the two clamping surfaces 17 of the clamping jaws 15, 16, as is schematically illustrated in FIG. 1.For clamping the workpiece 11, the working chamber of the pneumatic cylinder 41 is acted upon by compressed air, so that the drive part 44 moves along the central plane M toward the spindle axis A. The free ends 54 slide along the drive surfaces 55, 56, as a result of which a pivoting movement of the two output parts 51, 52 about their respective pivot axis S 1 or S 2 is initiated. Due to the inclination of the drive surfaces 55, 56 by the angle of inclination α, the two free ends 54 of the two output parts 51, 52 move towards one another. As a result, the flanges 26 of the two spindle sections 21, 22 are pressed towards one another counter to the prestressing force FV, and the two spindle sections 21, 22 execute an axial movement along the spindle axis A. During this axial movement, the clamping jaws 15, 16 therefore also move towards one another in the axial direction R and clamp the workpiece 11. As already explained, the movement of the drive part 44 is initiated by the application of compressed air to the working chamber of the pneumatic cylinder 41. The clamping force is defined by the air pressure in the working chamber of the pneumatic cylinder 41, the size of the piston surface and the transmission ratio of the transmission arrangement 50. Because of the check valve 46, the clamping force is maintained in the pneumatic line 45 until the working chamber of the pneumatic cylinder 41 is vented again. This can be seen by pressurization of the control line 57.To release the workpiece 11, the working chamber is evacuated as described above. Due to the pretensioning force FVof the pretensioning arrangement 35, the two spindle sections 21, 22 are forced away from one another along the spindle axis A and the free ends 54 of the two output parts 51, 52 likewise experience a force away from one another. The pivoting movement of the two output parts 51, 52 at their free ends 54 away from one another caused by the prestressing force FV veranlasst the displacement of the input part 44 away from the spindle axis A back into the starting position. This is possible because no counterforce acts on the drive part 44 in the working chamber. The clamping cheeks 15, 16 again assume the release position.FIG. 3 illustrates the lever ratios and transmission ratios in a highly schematic manner. Measured at right angles to the pivot axes S 1, S 2, the elevations 53 have a first distance D 1 from the plane in which the two pivot axes S 1, S 2 extend. From the contact points between the two driven parts 51, 52 at the free ends 54 with the respectively associated drive surface 55 or 56 of the drive part 44, the elevations 63 or contact points 53 have a second distance D 2. By means of a corresponding dimensioning of the two distances D 1, D 2, the forces and moments and in particular the clamping raft can be adapted to the specific application. Another variable parameter is the angle of inclination α, which determines the pivoting travel of the free ends 54 and the force exerted on the free ends 54 in the axial direction R. The piston surface of the piston of the pneumatic cylinder 41 also influences the clamping force.It can be seen in FIGS. 5, 6 to 7 that a holding part 69 can optionally be provided. The holding part 69 has a bow-shaped configuration and engages over the two output parts 51, 52 in the region of the relevant pivot axes S 1, S 2 on the side opposite the free ends 54. On the sides of the two output parts 51, 52 oriented away from one another in the axial direction R, a transverse groove 70 can therefore be introduced. The retaining part 69 engages with a web 71 in the transverse groove 70 of the first output part 51 and the transverse groove 70 of the second output part 52. The two webs 71 are connected to one another via a U-shaped connecting part 72 of the holding part 69. The holding part 69 thus has an approximately C-shaped cross section (FIG. 6 ). By means of the holding part 69, the bending open of the two output parts 51, 52 in the region of the pivot axes S 1, S 2 can be avoided by the forces acting between the extensions 64. Depending on the dimensioning and design of the output parts 51, 52, the provision of the holding part 69 may be advantageous. In the region between the bearing recesses 65 of the base part 12, the two output parts 51, 52 extend freely parallel to the central plane M. The holding part 69 offers additional stabilization against undesired deformations. This ensures that the two spindle sections 21, 22 cover the desired path and that a central clamping of the workpiece 11 can take place symmetrically to the central plane M.The clamping device 10 has two clamping units, each of which consists of a spindle section 21 or 22, a clamping jaw carrier 13 or 14 seated on the spindle section 21 or 22, and a clamping jaw 15 or 16 attached to the clamping jaw carrier 13 or 14. Each clamping unit always moves in the axial direction R as a block when the associated spindle section 21, 22 of the spindle 20 carries out an axial movement. The clamping jaw carriers 13, 14 are arranged on the respectively associated spindle section 21, 22 via a threaded connection. By rotating the spindle 20, the distance between the two clamping jaws 15, 16 can be adapted to the workpiece 11 to be clamped. The actual clamping and releasing movement is caused by a drive device 34 which brings about the axial movement of the two spindle sections 21, 22 along the spindle axis A of the spindle 20 towards one another or away from one another. During this axial movement, the clamping jaws 15, 16 move accordingly, so that the workpiece 11 is clamped or released depending on the direction of movement. The clamping device 10 can be quickly and easily set up on different workpieces 11, wherein identical workpieces 11 can then be quickly and securely brought about exclusively by the axial movement of the two clamping units and in particular of the two spindle sections 21, 22 towards each other or away from each other.List of reference numbers:10 Clamping device 11 Workpiece 12 Base part 13 First clamping jaw carrier 14 Second clamping jaw carrier 15 First clamping jaw 16 Second clamping jaw 17 Clamping surface 20 Spindle 21 First spindle section 22 Second spindle section 23 Outer end of a spindle section 24 Engagement element 25 Inner end 26 Flange 27 Rotational coupling device 28 Coupling protrusion 29 Coupling recess 34 Drive device 35 Pretensioning arrangement 36 Spring 37 Central recess 40 Actuating unit 41 Pneumatic cylinder 42 Piston 43 Piston rod 44 Drive part 45 Pneumatic line 46 Nonreturn valve 47 Control line 50 Transmission arrangement 51 First driven part 52 Second driven part 53 Contact point 54 Free end of a driven part 55 First drive surface 56 Second drive surface 60 Plate-shaped part 61 Through hole 62 Annular surface 63 Elevation 64 Extension 65 Bearing recess 66 Rolling body 69 Holding part 70 Transverse groove 71 Web 72 Connecting part α Angle of inclination a spindle axis FV prestressing force M center plane R axial direction U circumferential direction

Claims

Clamping device (10) for clamping a workpiece (11), having a first clamping jaw (15) present on a first clamping jaw carrier (13) and a second clamping jaw (16) present on a second clamping jaw carrier (14), having a base part (12) on which the two clamping jaw carriers (13, 14) are mounted so as to be movable guided in an axial direction (R), having a spindle (20) mounted rotatably about a spindle axis (A) and having a first spindle section (21) and a second spindle section (22), wherein the first clamping jaw carrier (13) is arranged on the first spindle section (21) and the second clamping jaw carrier (14) is arranged on the second spindle section (22), said second clamping jaw carriers moving towards one another or away from one another in the axial direction (R) when the spindle (20) is rotated about the spindle axis (A), wherein the two spindle sections (21, 22), the two clamping jaw carriers (13, 14) and the two clamping jaws (15, 16) are arranged symmetrically to a central plane (M), wherein the central plane (M) between the two clamping jaws (15, 16) is arranged at right angles to the spindle axis (A), wherein the two spindle sections (21, 22) are mounted so as to be movable relative to one another for carrying out an axial movement in the axial direction (R) along the spindle axis (A), and with a drive device (34) which is configured to bring about the axial movement of the two spindle sections (21, 22) without rotation of the spindle (20) in such a way that the axial movement of the spindle sections (21, 22) moves and moves the two clamping jaws (15, 16) between a release position in which the workpiece (11) can be inserted and removed between the clamping jaws (15, 16 and a clamping position in which the workpiece (11) is clamped between the clamping jaws (15, 16) in such a way, the axial movement of the spindle sections (21, 22) and of the two clamping jaws (15, 16) always takes place symmetrically to the central plane (M).Clamping device according to claim 1, characterised in that the two spindle sections (21, 22) are rotationally coupled to one another by a rotational coupling device (27) in the rotational direction about the spindle axis (A).Clamping device according to claim 2, characterised in that the rotary coupling device (27) has at least one coupling projection (28) which engages in an associated coupling recess (29).Clamping device according to claim 3, characterised in that the coupling projection (28) is arranged on the one spindle section (21) and the associated coupling recess (29) is arranged on the respective other spindle section (22).Clamping device according to claim 3 or 4, characterised in that the at least one coupling projection (28) and the at least one coupling recess (29) are arranged at a distance from the spindle axis (A).Clamping device according to one of the preceding claims, characterized in that the drive device (34) has a prestressing arrangement (35) which generates a prestressing force (FV) on the two spindle sections (21, 22), which prestressing force acts parallel to the spindle axis (A) in the axial direction (R).Clamping device according to claim 6, characterised in that the drive device (34) has an actuatable actuating unit (40) which is configured to move the two spindle sections (21, 22) in the axial direction (R) counter to the prestressing force (FV).Clamping device according to claim 7, characterised in that the actuating unit (40) has a hydraulic cylinder and / or a pneumatic cylinder (41) and / or a mechanical actuation.Clamping device according to claim 8, characterised in that the hydraulic cylinder and / or a pneumatic cylinder (41) is coupled to the two spindle sections (21, 22) via a transmission arrangement (50).Clamping device according to claim 9, characterised in that the transmission arrangement (50) has a drive part (44) which is motion-coupled to the hydraulic cylinder and / or a pneumatic cylinder (41), and in that a first output part (51) acting on the first spindle section (21) and a second output part (52) acting on the second spindle section (22) are present, wherein the two output parts (51, 52) are coupled to the drive part (44) and are configured to transmit the movement of the drive part (44) to the respectively associated spindle section (21, 22).Clamping device according to claim 10, characterised in that the drive part (44) has a first drive surface (55) and a second drive surface (56), which run inclined with respect to the spindle axis (A), wherein the first driven part (51) rests with a free end (54) against the first drive surface (55) and the second driven part (52) rests with a free end (54) against the second drive surface (56).Clamping device according to claim 10 or 11, characterised in that the two drive parts (51, 52) are mounted on the base part (12) such that they can be pivoted about a pivot axis (S1, S2) in each case.Clamping device according to one of Claims 10 to 12, characterized in that each driven part (51, 52) and / or each spindle section (21, 22) has at least one elevation (63), which forms a contact point (53) between the relevant driven part (51, 52) and the associated spindle section (21, 22).Method for clamping a workpiece (11) using a clamping device (10) according to one of the preceding claims, having the following steps: - setting the distance between the two clamping jaws (15, 16) by means of the spindle (20), - inserting the workpiece (11) between the clamping jaws (15, 16), - clamping the workpiece (11) exclusively by means of an axial movement of the two spindle sections (21, 22) brought about by means of the drive device (34) together with the clamping jaws (15, 16) without rotation of the spindle (20) in such a way that the axial movement of the spindle sections (21, 22) moves the two clamping jaws (15, 16) between a release position in which the workpiece (11) can be inserted and removed between the clamping jaws (15, 16 and a clamping position in which the workpiece (11) is clamped between the clamping jaws (15, 16), and in such a way that the axial movement of the spindle sections (21, 21, 22) moves the two clamping jaws (15, 16), 22) and of the two clamping jaws (15, 16) are always symmetrical to the central plane (M).

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