Convertible gripping device

Abstract

The gripping device includes a holder 100 and two gripper units 210, 210'. Each gripper unit includes a body 211; 211' and two base jaws 212, 213; 212'; 213'. The base jaws can move synchronously in opposite directions relative to the body. The gripper units are adjacent to each other on the holder, so that the base jaws of the two gripper units can move parallel to a common gripper plane. The gripping device is configured as a single gripper by attaching only the first gripper finger 250; 250' to each of the two outer base jaws 212, 212'. The gripping device can be very easily converted into a double gripper by attaching two additional gripper fingers to the inner base jaw or by removing the first gripper finger and attaching a second gripper finger to each of the four base jaws.

Description

Technical Field

[0001] The present invention relates to a gripping device, a processing machine provided with the gripping device, the use of such a gripping device, and a method for operating the same.

Background Art

[0002] So-called two-finger parallel grippers are known from the prior art. The two-finger parallel gripper includes a base body and two gripper fingers. The gripper fingers can move linearly in synchronization with each other on the base body so as to approach and separate from each other. The drive unit used for this stroke movement can be, for example, pneumatic or electric. Two-finger parallel grippers are available in different sizes, different stroke ranges, and different gripping force ranges, for example, from Zimmer Group GmbH, located in Rinaue, Germany, 77866, as the "GPP5000 series" (pneumatic) and the "GEP5000 series" (electric). The fingers can be pre-biased in the direction of the open position or the closed position by a return spring. Pneumatically driven two-finger parallel grippers are also known from the product information of "Universal Gripper PGN-Plus-P 380" by Schunk GmbH & Co. KG, located in Lauffen, Germany, 74348.

[0003] So-called two-finger angle grippers are also known from the prior art. In a two-finger angle gripper, the gripper fingers are rotated in synchronization with each other so as to approach and separate from each other around two parallel pivot axes. The "GPW5000 series" by Zimmer Group GmbH is mentioned as an example. Hereinafter, the two-finger parallel gripper and the two-finger angle gripper are collectively referred to as two-finger grippers.

[0004] In the prior art, it has been proposed to arrange two individual two-finger grippers on a common holder to form a double gripper. For example, in Patent Document 1, it has been proposed to arrange two two-finger angle grippers on a common holder at an angle to each other or parallel to each other adjacent.

[0005] An important application area of the gripper is a handling device for changing workpieces in a processing machine, particularly for changing gears in a gear hobbing machine. The handling device is used to move the workpiece between the work spindle and the work rest. For this purpose, the workpiece is gripped by the gripper of the handling device.

[0006] In order to minimize the cycle time of the processing machine, a handling device with a double gripper may be used. While one two-jaw gripper is used to remove the completed workpiece (finished part) from the work spindle, the other two-jaw gripper is preparing and holding the next blank. Then, the handling device moves the double gripper to a position where the double gripper transfers the blank to the work spindle. Thereafter, the handling device moves the double gripper to a position where the double gripper places the finished part on the work rest and captures the next blank. This can reduce a significant amount of time compared to a single gripper.

[0007] Handling devices with double grippers are mainly used for workpieces with a small diameter. However, due to space reasons, these handling devices often cannot be used for larger workpieces. Therefore, when processing both small and large workpieces on the same machine, the advantages of the double gripper are inevitably lost, or it is necessary to perform a time-consuming replacement or conversion of the entire handling device each time.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Summary of the Invention

[0009] The object of the present invention is to provide a gripping device that can be used for workpieces of different sizes and enables changes for smaller workpieces, in particular enabling rapid workpiece changes.

[0010] This object is achieved by the features of claim 1. Advantageous embodiments are provided in the dependent claims.

[0011] A gripping device is proposed that comprises a holder and two gripper units. Each of the gripper units has a base body that comprises its own drive unit and two base jaws. The base jaws can be moved synchronously in opposite directions with respect to the base body by the drive unit. The two gripper units are arranged side by side with respect to each other in the holder such that the base jaws of both gripper units can move parallel to a common gripper plane. One of the base jaws of each gripper unit forms an inner base jaw, and the other base jaw of each gripper unit forms an outer base jaw. The inner base jaws of the two gripper units are arranged between the outer base jaws. The gripping device is formed as a single gripper, where a first gripper finger is attached to each of the outer base jaws and a first object can be captured using the first gripper fingers, but the inner base jaws are configured not to hold gripper fingers for capturing the object.

[0012] Therefore, the two gripper units are provided side by side on a common holder that can be designed, for example, as a swivel arm. Such a design is essentially a double gripper feature. However, the gripping device does not operate as a double gripper but as a single gripper. Only the outer base joints of each gripper unit are used, while the inner base joints are not involved in the gripping process. The outer base joints of the two gripper units are spaced farther apart from each other than the two base joints of each individual gripper unit. This makes it possible to capture larger objects (especially workpieces) with the gripping device than with a single gripper unit. Each of the two gripper units has its own drive unit and, if necessary, its own return spring, so that a gripping force twice as large as that of a single gripper unit can be generated. This is particularly advantageous in the case of large objects.

[0013] Preferably, in a first operating mode, the gripping device comprises a controller configured to interlock and control the drive units of the two gripper units such that the outer base joints of the two gripper units move synchronously in opposite directions to capture or place an object.

[0014] The gripping device can be easily converted into a double gripper by attaching two additional first gripper fingers to the inner base joints or by removing the two first gripper fingers from the outer base joints and attaching second gripper fingers, which are designed to capture other, usually smaller objects, to each of the outer and inner base joints. In this way, each of the two gripper units can be used to capture a second object independently of the other gripper unit.

[0015] Accordingly, the gripping device can include as a kit the additional gripper fingers necessary for conversion to operate as a double gripper. In particular, the gripping device can comprise the two additional first gripper fingers mentioned or the four second gripper fingers mentioned. These gripper fingers can be attached to the corresponding base jaws for double gripper operation, but are removed from the base jaws in single gripper operation.

[0016] Accordingly, it is advantageous that the controller for double gripper operation can switch to a second operating mode that controls the two gripper units independently of each other.

[0017] So as to be able to reliably determine the operating state of the gripping device, each of the gripper units can be provided with a position detection device designed to determine the position of a target at one of the gripper fingers. This is preferably each outer gripper finger, i.e., the gripper finger attached to each outer base jaw. In this way, the positions of the two outer base jaws can be reliably determined in both single gripper operation and double gripper operation.

[0018] In particular, the position detection device can comprise an inductive position sensor. In this case, the target is preferably a target made of a soft magnetic material. However, other measuring principles, such as optical distance sensors or eddy current sensors, are also conceivable.

[0019] The base jaws can be displaced linearly relative to the base body of each gripper unit, i.e., each gripper unit preferably forms a two-jaw parallel gripper. Alternatively, the base jaws can be pivotable relative to the base body, i.e., each gripper unit can form a two-jaw angular gripper.

[0020] The drive unit for each gripper unit relative to the base joist can, in particular, operate pneumatically or electrically. The base joist can be mechanically coupled to the drive unit such that when the drive unit operates, it forces the base joist to perform a synchronized movement in the opposite direction. Each gripper unit can include a return spring that preloads the gripper jaws in the direction of the closed or open position of the base joist in a non-driven state.

[0021] The first gripper finger and the second gripper finger can be configured to capture various types of objects. One important class of objects is the workpiece of a processing machine. In a preferred embodiment, the gripper fingers are designed to capture toothed workpieces, in particular external gears (spur gears). In this case, the workpiece is captured between the gripper fingers by moving the two gripper fingers synchronously towards each other. Each gripper finger has a gripper jaw that faces inward towards the workpiece, and this gripper jaw is designed such that as a result of this movement, the gripper jaw holds the outer periphery of the workpiece in a force-fitting manner with an inward gripping force. However, it is also conceivable to use the gripping device to capture an annular workpiece, in particular an internally toothed workpiece, at its inner periphery. For this purpose, the gripper fingers can correspondingly have outward-facing gripper jaws or gripper bolts, and these gripper jaws or gripper bolts are designed such that as a result of the gripper fingers moving outward in opposite directions from each other, they hold the inner periphery of the workpiece in a force-fitting manner with an outward gripping force.

[0022] The gripper fingers are preferably of modular design, enabling particularly rapid and flexible adaptation to different types of workpieces. To this end, each of the first gripper finger and / or the second gripper finger comprises a base finger and gripper claws formed separately from the base finger. The base finger can be detachably connected to one of the base joints, particularly at its proximal end. The gripper claws are releasably connected to the base finger, particularly in the region between the proximal end and the distal end of the base finger. In this way, the gripper claws can be exchanged very easily and quickly to adapt the device to different workpieces.

[0023] Particularly rapid change of the gripper claws is possible if each gripper claw can be connected to the associated base finger by a detachable snap connection.

[0024] In an advantageous embodiment, the gripper claw has for this purpose at least one fastening cam. The base finger defines the longitudinal direction of the finger. The base finger has a lateral insertion opening extending in a direction transverse to the longitudinal direction of the finger, into which at least one fastening cam of the gripper claw can be inserted in a direction transverse to the longitudinal direction of the finger. A spring-biased fixing pin having a latching projection is attached to the base finger. The latching projection can be formed, for example, by a lateral pin extending transversely through the fixing pin. At least the latching projection extends into the insertion opening. When a fixing cam is inserted into the insertion opening to establish a releasable snap connection, the latching projection engages in a recess of the fixing cam. The fixing pin defines the longitudinal axis of the pin. The fixing pin is displaceable relative to the base finger along the longitudinal axis of the pin. The fixing pin extends into the region outside the base finger. In this region, an actuating member is formed on or connected to the fixing pin. The actuating member can in particular be designed as a disk or a cap forming a contact surface for the user's finger. The releasable snap connection can be released again by an axial pressure on the actuating member and the resulting displacement of the fixing pin along the longitudinal axis of the pin. The fixing pin can be surrounded by a helical spring in the region outside the base finger. The spring can be compressible, for example, between the outer surface of the base finger and an opposing stop that can be attached to the fixing pin and formed on the actuating member in order to apply a spring force to the fixing pin in the direction of the position fixing at least one fastening cam. The gripper claw has two parallel fixing cams, and it is preferable that the fixing pin penetrates the region of the insertion opening located between the fixing cams in the inserted state. Thus, the fixing pin has two latching projections extending symmetrically with respect to the longitudinal axis of the fixing pin in a direction transverse to the longitudinal axis of the pin. In particular in this case, it is advantageous if the latching projections are formed on both sides of the fixing pin by a lateral pin penetrating the fixing pin transversely.

[0025] It is particularly advantageous to use a gripping device for handling toothed workpieces, in particular for workpiece changing, in a hobbing machine, i.e., to feed a blank into the hobbing machine and to remove the finished part from the hobbing machine. Accordingly, the present invention also relates to a hobbing machine equipped with a gripping device of the type described above.

[0026] The present invention further provides a method of operating a gripping device of the above type. In this method, in single gripper operation, the drive parts of the two gripper units are interlocked and controlled by a first gripper finger so that the outer base joints of the two gripper units move synchronously in opposite directions to capture an object.

[0027] The method can further include converting the gripping device from a single gripper to a double gripper by attaching two additional first gripper fingers to the inner base joints, or by removing the two first gripper fingers from the outer base joints and attaching a second gripper finger to each of the outer base joints and the inner base joints.

[0028] This process can include capturing an object independently of each other by the two gripper units after conversion to a double gripper. For this purpose, the drive parts of the two gripper units are controlled so that the respective base joints of the two gripper units move synchronously in opposite directions independently of the base joints of the respective other gripper units.

[0029] The method can include determining the position of one target in each of the gripper fingers attached to the outer base joints of the two gripper units in single gripper operation and / or double gripper operation.

[0030] Preferred embodiments of the present invention are described below with reference to the drawings, which serve merely for illustration and are not intended to be construed as limiting.

Brief Description of the Drawings

[0031]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Embodiments for Carrying Out the Invention

[0032] <Single Gripper Unit> Figure 1 shows a gripper unit 210 known per se from the prior art. The gripper unit is a pneumatically actuated two-finger parallel gripper commercially available in many different variants. The gripper unit 210 comprises a base body 211 in which a pneumatic drive unit (not shown separately) is accommodated. Compressed air is supplied to the drive unit via a hose connection 214. The gripper unit 210 further comprises two base jaws 212, 213, which are guided on the base body 211 on the same straight line along the displacement direction V. The base jaws 212, 213 can be displaced synchronously in opposite directions relative to the base body 210 by the drive unit. Depending on the embodiment, there may be a return spring within the base body 210, and the return spring applies a return force to close or open the base jaws 212, 213 in the non-driven state.

[0033] <Double gripper design> Figures 2 and 3 show a gripping device in the form of a gripper arm comprising two gripper units 210, 210'. Each of these gripper units is configured according to Figure 1. The gripper units 210, 210' are mounted side by side on a common holder 100 in the form of a swivel arm. The gripper units 210, 210' have substantially the same configuration and are mounted in a mirror-inverted manner with respect to a vertical mirror plane extending through the center between the gripper units 210, 210'. Each of the further components connected to each gripper unit is also arranged in a mirror-inverted manner with respect to the respective component on the other gripper unit.

[0034] The gripper unit arranged on the right side of Figure 2 and all the components connected thereto are hereinafter denoted by reference signs without a prime symbol. The gripper unit arranged on the left side of Figure 2 and all the components connected thereto are denoted by the same reference signs with a prime symbol.

[0035] The base joints 212, 213, 212', 213' of the two gripper units 210, 210' are all displaceable relative to each other in a straight line along the displacement direction V in the common gripper plane E. Among the base joints of each gripper unit, the base joints 213, 213' respectively arranged adjacent to the base joints of the other gripper unit are hereinafter referred to as "inner base joints", and the other two base joints 212, 212' are referred to as "outer base joints". The inner base joints 213, 213' are arranged between the outer base joints 212, 212' with respect to the displacement direction V.

[0036] In the embodiments of FIGS. 2 and 3, the gripping device is designed as a double gripper. For this purpose, the gripper fingers 220, 230, 220', 230' are attached to the respective base joints 212, 213, 212', 213'. The gripper fingers 220, 230 on the base joints 212, 213 of the first gripper unit 210 are formed and arranged to receive the gear-shaped workpiece 310 therebetween. To grip the workpiece 310, the first gripper unit 210 moves the base joints 212, 213 synchronously towards each other, preferably by the closing return force of a return spring. As a result, the workpiece 310 is held in a force-fitting manner by the inward gripping force between the gripper fingers 220, 230. To release the workpiece 310, the first gripper unit 210 moves the base joints 212, 213 synchronously away from each other. The gripper fingers 220', 230' in the second gripper unit 210' are also formed and arranged to be able to receive another workpiece 310' therebetween, so as to be mirror-symmetrical to the gripper fingers 220, 230 in the first gripper unit 210. To grip and release the workpiece 310', the second gripper unit 210' moves the base joints 212', 213' synchronously towards and away from each other. This is done independently of the operation of the first gripper unit 210. In this way, overall, two workpieces can be captured and placed independently of each other by the gripping device.

[0037] The gripper fingers 220, 230, 220', 230' are of a modular configuration. For example, the gripper finger 220 comprises a base finger 221 and a gripper jaw 222. The base finger 221 has a proximal end and a distal end. At the proximal end, the base finger 221 is detachably attached to the outer base joint 212 of the first gripper unit 210. This attachment can be achieved, for example, by a screw connection (not shown). To increase the positioning accuracy, a positioning sleeve can be provided on the base joint in a manner known per se. The gripper jaw 222 is laterally attached to the base finger 221 in a region located between the proximal end and the distal end of the base finger 221. This connection is also releasable. In this example, the attachment of the gripper jaw 222 to the base finger 221 is achieved by a quick-change device which will be described in more detail below. The gripper finger 230 is constructed similarly to the gripper finger 220 and likewise comprises a base finger 231 and a gripper jaw 232. The gripper jaws 222, 232 face each other such that a workpiece 310 can be received therebetween. In so doing, each gripper jaw contacts the workpiece 310 at at least two locations along the circumference of the workpiece in order to prevent the workpiece from tilting. The structure of the gripper fingers 220', 230' is a mirror image of the gripper fingers 220, 230.

[0038] Due to the modular design, the gripper fingers can be very quickly and easily adapted to different workpieces, for example, gears having different diameters, by simply exchanging the gripper jaws.

[0039] Each of the gripper units 210, 210' is provided with a position detection device 240, 240' for determining the operating state of each gripper unit 210, 210'. The position detection devices 240, 240' respectively determine the positions of targets 243, 243' located near the proximal ends of the respective outer gripper fingers 220, 220'. In this example, the position detection devices 240, 240' each include an inductive position sensor (displacement transducer) 241, 241'. Accordingly, the targets 243, 243' are at least partially made of a soft magnetic material such as steel. To protect the position sensors, each position detection device 240, 240' is attached to the base bodies 211, 211' of the respective gripper units 210, 210' and includes housings 242, 242' that cover both the respective position sensors 241, 241' and the respective targets 243, 243'.

[0040] <Single gripper design> Figure 4 shows the conversion to a single gripper. For this purpose, the gripper fingers 220, 230, 220', 230' that were used to operate as a double gripper are removed from the inner base joints 213, 213' and the outer base joints 212, 212'. Instead, here two other gripper fingers 250, 250' are attached to the outer base joints 212, 212'. The inner base joints 213, 213' are left empty or protected by a cover. The inner base joints 213, 213' are no longer involved in the gripping process.

[0041] The gripper fingers 250, 250' are also modular and each include a base finger 251, 251' and a gripper claw 252, 252'. The base fingers 251, 251' and the gripper claws 252, 252' are dimensioned here such that a larger workpiece 320 can be captured between the gripper fingers 250, 250'.

[0042] To grip or place the workpiece 320, the drive units of the two gripper units 210, 210' are interlocked and controlled so that the outer base joints 212, 212' of the two gripper units 210, 210' move synchronously so as to approach and separate from each other.

[0043] Since each of the two outer base joints 212, 212' belongs to different gripper units 210, 210' with their respective drive units and, if necessary, their respective return springs, a gripping force twice as large as that of a single gripper unit 210 can be achieved in this configuration. This is particularly advantageous in the case of larger workpieces.

[0044] The gripper fingers 250, 250' also each hold the targets 243, 243' used together with the position detection devices 240, 240' to determine the operating states of both gripper units 210, 210'.

[0045] The reverse conversion from a single gripper to a double gripper is also easily possible.

[0046] <Quick change device for gripper jaws> With reference to FIGS. 5 to 8, the attachment of the gripper jaw 222 to the associated base finger 221 will be described in more detail. Other gripper jaws are attached to their respective base fingers in the same way.

[0047] As can be seen in Figure 3, the gripper claw 222 has two parallel fastening cams 229. The elongated base finger 221 defines the longitudinal direction of the finger along the main extension direction. As can be particularly seen in Figures 5 and 7, a side insertion opening 223 is formed in the base finger 221 in a transverse direction with respect to the longitudinal direction of the finger. The two fastening cams 229 of the gripper claw 222 can be inserted into the insertion opening 223 in a transverse direction with respect to the longitudinal direction of the finger. A fixed pin 224 is attached to the base finger 221. The fixed pin 224 defines the longitudinal axis of the pin. The fixed pin 224 is displaceable with respect to the base finger 221 along the longitudinal axis of the pin, in a transverse direction with respect to the longitudinal direction of the finger and in a transverse direction with respect to the insertion direction of the two fastening cams 229. When the fastening cam 229 is inserted into the insertion opening 223, the fixed pin extends through the region located between the fastening cams 229 of the insertion opening 223. A transverse pin 225 extends transversely through the fixed pin 224. The transverse pin 225 forms respective latching protrusions on both sides of the fixed pin 224. The latching protrusions latch into corresponding recesses on the lower side of the fastening cam 229 when the fastening cam 229 is inserted into the insertion opening 223. In this way, a releasable snap connection is provided between the gripper claw 222 and the base finger 221. One end of the fixed pin 224 extends into a region located outside the base finger 221. In this region, the fixed pin 224 is surrounded by a helical spring 227. An actuating member in the form of a cap 226 is attached to the relevant end of the fixed pin 224. The inner end face of the cap 226 forms an opposing stop for the helical spring 227. The helical spring 227 is compressible between the outer face of the base finger 221 and the cap 226 so as to bias the fixed pin 224 by a spring force in the direction of the position where the transverse pin 225 fixes the fastening cam 229. In this regard, a circumferential collar 228 on the fixed pin 224 limits the movement range of the fixed pin 224 in the direction of the spring force and ensures a specific spring biasing. Due to the axial pressure applied to the cap 226 and the resulting displacement of the fixed pin 224 along the longitudinal axis of the pin, the transverse pin 225 exits the recess of the fastening cam 229.As a result, the releasable snap connection is released again. From this perspective, the cap 226 functions as a push button.

[0048] <Use in a milling machine> An important use of the proposed gripping device relates to workpiece changing in a milling machine. This is shown by the examples in FIGS. 5 and 6, where an example of a milling machine 400 is shown. In a method known per se, the milling machine 400 comprises a machine bed 410, a workpiece carrier 420, a tool carrier 430, and a machine controller 440 with a control panel 441.

[0049] The workpiece carrier 420 is designed as a turret. The workpiece carrier 420 holds two workpiece spindles 421, and the two workpiece spindles 421 are arranged offset from each other by 180° with respect to the vertical swivel axis of the turret. In FIG. 5, only one of these workpiece spindles is visible. This workpiece spindle is in the workpiece changing position, at which the finished part can be removed from the workpiece spindle and a new blank can be clamped. The other workpiece spindle is hidden by the turret in FIG. 5. This workpiece spindle is in the machining position, at which the pre-clamped workpiece can be machined by a tool on the tool carrier 430 in a method known per se.

[0050] To exchange the workpiece on the workpiece spindle 421 in the workpiece exchange position, the above-described gripping device is used in the double gripper operation in the example of FIG. 5. The gripping device designed as a gripper arm is attached to a gripper arm carrier (not shown). The gripper arm carrier is arranged stationary next to the machine bed 410 but is not connected to the machine bed to isolate vibrations. The gripping device is attached to the gripper arm carrier and can be swiveled relative to the gripper arm carrier about a vertical swivel axis extending parallel to the Z direction by a corresponding drive unit and can move linearly in the Z direction (i.e., along the vertical direction).

[0051] The completed work 310 (completed part) is installed in the work clamping part 422 of the work spindle 421. The related centering jig 423 having the centering tip 424 retracts upward. The gripping device pivots from the position when it is outside the working space of the gear cutting machine 400 to the pivoting position shown in FIGS. 5 and 6, and descends in the Z direction, whereby the first gripper unit 210 can capture the completed part 310 from the work spindle by the attached gripper fingers. The gripping device removes the completed part 310 from the work clamping part 422 by a short-stroke movement. Meanwhile, the second gripper unit 210' already holds the work (blank) 310' to be processed next. Here, the gripping device pivots slightly further so that the blank 310' comes above the work fixing part 422, and descends again in the Z direction, whereby the blank 310' can be placed on the work fixing part 422. Here, the blank 310' is clamped to the work clamp fixing part 422. The gripping device rises again in the Z direction, pivots out of the working area, and reaches the work storage part 500. Here, the completed part 310 previously captured by the gripper unit 210 is placed, and a new blank is captured by the gripper unit 210'. Meanwhile, the blank 310' is further fixed and centered by the centering tip 424, and a meshing operation is performed by a meshing device (not shown) to determine the angular position of the tooth part of the blank 310' with respect to the work spindle axis. The work carrier 420 pivots 180° here, whereby the work spindle 421 with the blank 310' clamped moves to the machining position, while another work spindle with another completed part on it moves to the work change position. Here, the blank 310' is machined by a tool, and the described cycle is repeated for further completed parts.

[0052] Therefore, the workpiece is changed while another workpiece is being processed. Since only a small linear motion and a swiveling motion are required to remove the finished part from one of the work spindles and replace it with a new blank, the change of the workpiece is carried out very quickly. In particular, the gripping device does not require a swivel between the working space of the gear cutting machine 400 and the workpiece storage unit 500 for this purpose. As a result, the entire workpiece change can be carried out within the processing time during which other blanks are being processed, minimizing unproductive idle time.

[0053] However, the operation as a double gripper is only possible for relatively small workpieces. Therefore, when processing larger workpieces, the gripping device is converted to operate as a single gripper as described above. With a single gripper, much larger workpieces can be attached and detached. The maximum diameter of the workpiece that can be handled in the single gripper operation can exceed more than 2.5 times the maximum diameter of the workpiece that can be handled in the double gripper operation. As described above, the change of the workpiece is possible in parallel with the processing time. However, here, the gripping device has to completely reciprocate and swivel between the working area of the gear cutting machine 400 and the workpiece storage unit 500 from the time the finished part is taken out until the next blank is clamped. This requires more time than the short linear motion and swiveling motion by the double gripper. However, on the other hand, processing larger workpieces usually also requires more time. Therefore, even here, although the total cycle time becomes longer, the unproductive non-production time can be kept small.

[0054] <Control and Monitoring of Operating States> All movements of the gripping device relative to the gripper arm carrier and the operation of the two gripper units 210, 210' are controlled by a control device, i.e., the "controller". For this purpose, a separate controller can be provided. Alternatively, this task can also be executed by the controller 440 of the processing machine or by the controller of the workpiece storage unit 500. For this purpose, the corresponding controller has the corresponding software.

[0055] In particular, the software can distinguish between two operating modes, i.e., a first mode in which the gripping device operates as a double gripper and a second mode in which the gripping device operates as a single gripper. In the first operating mode, the two gripper units open and close independently of each other, while in the second operating mode, the two gripper units open and close in conjunction with each other simultaneously.

[0056] The switching between operating modes can be manually executed by making corresponding inputs on the control panel. However, it is also conceivable to provide presence sensors on the base joints of the gripper units to determine whether the gripper fingers are attached to the respective base joints, and to automatically switch between the first operating mode and the second operating mode based on the signals from these sensors.

[0057] The controller preferably receives position signals regarding the two gripper units from the position detection devices 240, 240'. Based on these position signals, in particular, the following states can be distinguished. - The associated gripper unit is open. - The associated gripper unit is fully closed, and - The associated gripper unit is partially closed and the workpiece is being gripped.

[0058] It is also possible to check whether the determined position of the gripper unit in the "work gripping" state corresponds to the expected position. If the determined position deviates from the expected position by more than a predetermined tolerance range (for example, ±1 mm), the controller can determine that an error has occurred and can stop further processing. In this way, it is possible to prevent a blank having an inappropriate diameter, which can damage the centering device and / or the processing tool, from reaching the work spindle.

[0059] <Alternative embodiment> Of course, numerous modifications can be made without departing from the scope of the invention as set forth in the claims.

[0060] For example, the gripper unit can have a greater distance along the displacement direction V than in the exemplary embodiment described above so that it is possible to capture a larger work in a single gripper operation. The gripper units 210, 210' can be mounted on the holder 100 so as to be displaceable along the displacement direction V to conform to different diameters. For this purpose, the holder 100 can optionally have corresponding rails on which the gripper units are displaceably mounted.

[0061] Instead of a two-jaw parallel gripper, the gripper unit can also be designed as a two-jaw angular gripper. Accordingly, the base jaws do not move linearly but pivot with respect to the base body of each gripper unit. The pivoting movement is also performed here for all base jaws in the gripper plane E. In this case, in order to avoid collisions, the gripper unit is preferably mounted at a somewhat greater distance along the direction V than in the exemplary embodiment described above.

[0062] The gripper unit may be driven electrically instead of pneumatically.

[0063] The quick-change device for the gripper claws can also be designed differently from that shown in the figures. In particular, the actuating member can also be designed as a flat disk instead of a cap. Instead of the lateral pins, the latching projections on the fixed pins can also be formed in other ways.

[0064] The gripping device can be used not only with external gears (spur gears), but also with other types of workpieces, in particular other types of workpieces having a cylindrical outer shape. Adaptation to different workpieces is possible in a very short time by changing the gripper claws.

[0065] It is also conceivable to use the gripping device to capture gears with internal teeth or other objects on the inner circumference. For this purpose, the gripper fingers can be provided, for example, with pins protruding downwards or gripper claws protruding downwards and facing outwards. In this case, in order to capture the object, the gripper unit performs an opening operation instead of a closing operation. Therefore, for safety reasons, it may be advantageous to use a gripping device in which the return spring generates an opening return force.

[0066] Instead of the inductive position sensor (displacement transducer), other types of position sensors, for example, optical distance sensors or eddy current sensors, can be used to detect the operating state.

Explanation of reference numerals

[0067] 100 Holder 210, 210’ Gripper unit 211, 211’ Base body 212, 212’ Outer base joist 213, 213’ Inner base joist 214 Hose connection 220, 220’ Outer gripper fingers 221, 231 Base fingers 222, 232 Gripper claws 223 Insertion opening 224 Fixed pin 225 Horizontal Pin 226 Cap 227 Helical Spring 228 Color 229 Fastening Cam 230, 230’ Inner Gripper Finger 240 Position Detection System 241 Position Detection Device 242 Cover 243 Target 250, 250’ Gripper Finger 251, 251’ Base Finger 252, 252’ Gripper Claw 310, 310’ Workpiece 320 Workpiece 410 Machine Bed 420 Work Carrier 421 Work Spindle 422 Work Clamping Section 423 Center Support 424 Centering Tip 430 Tool Carrier 440 Controller of the Processing Machine 441 Control Panel 500 Work Storage Section E Gripper Plane

Claims

Claim 1 A gripping device, comprising: a holder (100); two gripper units (210, 210'); Each of the gripper units (210, 210') comprises a base body (211; 211') including a drive part and two base levers (212, 213; 212', 213'), and the base levers (212, 213; 212', 213') are displaceable in synchronization with each other in opposite directions with respect to the base body (211; 211') on the same straight line or by turning by the drive part. The two gripper units (210, 210') are arranged side by side along a displacement direction (V) in a common gripper plane (E) on the holder (100) such that the base levers (212, 213; 212', 213') of both gripper units (210, 210') are displaceable along the displacement direction (V) in the common gripper plane (E). One of the base levers of each gripper unit (210, 210') is an inner base lever (213; 213'), and the other base lever of each gripper unit is an outer base lever (212; 212'). The inner base levers (212, 212') of the two gripper units are arranged between the outer base levers (213, 213') of the two gripper units. The gripping device is configured as a single gripper, and a first gripper finger (250; 250') is attached to each of the outer base levers (212, 212'), whereby a first object (320) can be captured by the first gripper fingers (250, 250'), while the inner base levers (213, 213') do not hold gripper fingers for capturing an object. The gripping device is characterized by this. Claim 2 The gripping device according to claim 1, further comprising a controller (440) configured to interlock and control the drive parts of the two gripper units (210, 210') in the first operation mode such that the outer base levers (212, 212') of the two gripper units (210, 210') move in synchronization with each other in opposite directions. Claim 3 ​ The gripping device can be converted into a double gripper configuration by attaching two further first gripper fingers to the inner base joints (213, 213'), or by removing the two first gripper fingers (250, 250') from the outer base joints (212, 212') and attaching second gripper fingers (220, 230, 220', 230') to each of the outer base joints (212, 212') and the inner base joints (213, 213'), whereby a second object (310, 310') can be captured by each of the two gripper units (210, 210'). The gripping device according to claim 1 or 2.

4. The controller is switchable to a second operating mode for controlling the two gripper units (210, 210') independently of each other. The gripping device according to claim 2.

5. Each of the gripper units (210, 210') comprises a position detection device (240, 240'), and the position detection device (240, 240') is configured to determine the position of a target (243, 243') on a gripper finger (220, 220') attached to the outer base joint (212, 212') of each gripper unit (210, 210'). The gripping device according to any one of claims 1 to 4.

6. The position detection device (240, 240') comprises an inductive position sensor (241, 241'), and the target (243, 243') comprises a soft magnetic material. The gripping device according to claim 5.

7. Each of the first gripper fingers (250, 250') and / or the second gripper fingers (220, 230, 220', 230') a base finger (251; 251'; 221; 231); a gripper claw (252; 252'; 222; 232); and comprises the base finger (251; 251'; 221; 231) is releasably connectable to one of the base joints (212; 213, 212', 213'); the gripper claw (252; 252'; 222; 232) is releasably connected to the base finger (251; 251'; 221; 231). The gripping device according to any one of claims 1 to 6.

8. The gripping device according to claim 7, wherein the gripper claws (252; 252'; 222; 232) are connectable to the base fingers (251; 251'; 221; 231) by a releasable snap connection.

9. The gripper claws (252; 252'; 222; 232) comprise at least one fastening cam (229), the base fingers (251; 251'; 221; 231) define the longitudinal direction of the fingers and have a side insertion opening (223) extending in a transverse direction with respect to the longitudinal direction of the fingers, and at least one of the fastening cams (229) of the gripper claws (252; 252'; 222; 232) can be inserted into the side insertion opening (223) in a transverse direction with respect to the longitudinal direction of the fingers, a spring-biased fixing pin (224) having a latching projection and extending into the side insertion opening (223) is provided on the base fingers (251; 251'; 221; 231), the fixing pin (224) is formed and arranged such that when the fastening cam (229) is inserted into the side insertion opening (223) to establish the releasable snap connection, the latching projection latches into a recess of the fastening cam (229), and the releasable snap connection is releasable by pressure on an actuating member (226) formed on or connected to the fixing pin (224), the gripping device according to claim 8.

10. A gear cutting machine comprising the gripping device according to any one of claims 1 to 9, wherein the first gripper fingers (250, 250') and / or the second gripper fingers (220, 230, 220', 230') are configured to capture a toothed workpiece, the gear cutting machine.

11. Use of the gripping device according to any one of claims 1 to 9 for capturing a toothed workpiece.

12. A method of operating the gripping device according to any one of claims 1 to 9, the method comprising capturing an object (320) by using the first gripper fingers (250, 250') to interlock and control the drive parts of the two gripper units (210, 210') such that the outer base joints (212, 212') of the two gripper units (210, 210') move synchronously in opposite directions.

13. The method according to claim 12, comprising converting the gripping device from a single gripper configuration to a double gripper configuration by attaching two further first gripper fingers to the inner base jaws (213, 213'), or by removing two of the first gripper fingers (250, 250') from the outer base jaws (212, 212') and attaching second gripper fingers (220, 230, 220', 230') to each of the outer base jaws (212, 212') and the inner base jaws (213, 213').

14. The method according to claim 13, comprising independently controlling the drive parts of the two gripper units (210, 210') such that, after conversion to the double gripper configuration, the base jaws (212, 213; 212', 213') of each of the two gripper units move synchronously in opposite directions independently of the base jaws of the other gripper unit.

15. The method according to any one of claims 12 to 14, comprising determining the position of each target (243) of the gripper fingers (220, 220') attached to the outer base jaws (212, 212') of the two gripper units (210, 210').

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