EP2859994A2 - Device for clamping a workpiece - Google Patents

Abstract

Apparatus for clamping a workpiece for processing in a grinding machine, comprising a C-shaped yoke (10) having a yoke spine (12) and a first leg (14) and a second leg (16) angled in the same direction protrude from the yoke back (12), with a in the first leg (14) rotatably received plunger (22) and in the second leg (16) rotatably received counter-ram (28), wherein the plunger (22) and the counter-ram (28 ) are coaxially aligned with each other, wherein the plunger (22) is rotationally driven drivable and wherein the plunger (22) and the counter-plunger (28) by means of a power source (64) axially relative to each other are movable to the workpiece (66) with an axial clamping force between to tension the plunger (22) and the counter-ram (28). The yoke (10) is mountable positioned on the grinding machine so that the axes of the ram (22) and the counter-ram (28) are aligned with a rotatably driven axis (30) of the grinding machine. The plunger (22) can be coupled axially to the rotationally driven shaft (30). A first clamping yoke (42) is mounted on the yoke (10) and supports with an arm (50) the plunger (22) against the clamping force axially. A second clamping bracket (44) is pivotally mounted on the yoke (10) and moves with an arm (56) the counter-ram (28) by force axially. The bearings (46, 48) of the first tension bow (42) and the second tension bow (44) are arranged at the opposite ends of the yoke (10) in the region of the yoke back (12). The clamping force is introduced via the clamping bracket (42, 44) in the plunger (22) and the counter-ram (28).

Description

The invention relates to a device for clamping a workpiece for machining in a grinding machine according to the preamble of patent claim 1.

In fixtures of this type, the workpieces, for example, inserts for lathes for machining with a grinding wheel between two plungers are stretched. In order to have the most free access of the grinding wheel to the workpiece, it is for example from the EP 1 579 955 B1 known to receive the two plungers axially aligned in two legs of a C-shaped yoke. The first plunger is driven rotatably controlled by means of an axis of the grinding machine to align the tensioned workpiece in the circumferential angle against the grinding wheel. The second plunger is rotatably mounted in the yoke and axially supported on the leg of the yoke. The workpiece is tensioned between the two tappets by the yoke with the second plunger force applied on the first plunger is moved axially.

Since the workpiece is only clamped frictionally between the plungers, a high axial clamping force is required. This high clamping force is supported in this known device by the second plunger on the leg of the C-shaped yoke. As a result, a bending of the leg can be caused by which a deviation of the two plungers from the exact axial alignment is effected.

From the DE 1 924 315 A1 it is known to clamp the workpiece between two plungers. The first plunger is rotatably driven and mounted axially supported in the machine. The second plunger is axially displaceable axially guided in the machine.

To generate the axial clamping force of the second plunger is subjected to force by means of a clamping bracket. The clamping bracket is designed as a two-armed lever whose bearing is held by means of a tie rod on the machine frame. The clamping bracket is pivoted by means of a hydraulic cylinder unit. The large axial clamping force does not lead to misalignment of the plunger. The axial clamping force is introduced on the one hand via the tie rod in the machine frame, on the other hand, the storage of the first plunger in the machine frame must absorb the entire axial clamping force. The ram tensioning device is structurally integrated into the grinding machine, so that the grinding machine must be structurally designed for the ram tensioning device.

The invention has for its object to provide a device for clamping a workpiece for machining in a grinding machine, in which large axial clamping forces do not lead to a deformation of the yoke and which is suitable for a modular attachment to a conventional grinding machine.

This object is achieved by a device with the features of claim 1.

Advantageous embodiments of the invention are specified in the subclaims.

The inventive device for clamping a workpiece for processing in a grinding machine has a C-shaped yoke. In each of the two legs of the yoke, one of the two plungers is mounted in such a way that the two plungers are axially aligned. The high axial clamping force with which the workpiece is held between the plungers, is each introduced into a clamping bracket. The clamping straps are mounted on the yoke in such a position that an imaginary connecting line of the two bearing points runs in the yoke back and thus in the mechanically neutral fiber of the yoke. The axial clamping force of the plunger can thus not lead to bending and spreading apart of the legs of the yoke. Even with a high clamping force, the plungers remain axially aligned in the legs of the yoke. The axial clamping force is generated by a suitable power source, in particular by a cylinder unit, and acts on the clamping bracket. The one clamping bracket thereby supports the first plunger axially against the clamping force, while the second clamping bracket moves the second plunger axially force-loaded against the first plunger. As a result, the entire axial clamping force is supported within the device by the two clamping bracket. The device can be mounted with the first plunger on an axis of a grinding machine, without the high axial clamping force acting on the bearing of this axis. The device is thus eminently suitable for modular mounting on an axle of a conventional grinding machine, without the need for the bearing of this axle to be designed to accommodate axial forces or to be rebuilt.

In order to completely exclude any action of the axial clamping force on the yoke, a tie rod is provided in a preferred embodiment in the yoke. The tie rod is fixed only in its position in the yoke and extends with radial play through a bore of the yoke. Preferably, the tie rod is attached at one end to one end of the yoke and extends through the bore to the other end of the yoke. The clamps are mounted at the two ends of the tie rod. The entire axial clamping force becomes exclusive taken up by the tie rod and is not introduced into the yoke. Although the high axial clamping force may optionally lead to a small elongation of the tie rod, under no circumstances causes a deformation of the yoke.

In an expedient embodiment, the clamps are designed as two-armed lever, each attacking with one arm on the associated plunger, while on the other arm, the power source for the clamping force, for example a cylinder unit, attacks. This embodiment allows a compact construction of the device, since the legs of the C-shaped yoke can be short and the hydraulic unit can be arranged on the outside of the yoke back.

While the clamping bracket, which moves the one plunger axially, is pivotally mounted on the yoke and in particular on the tie rod, the other clamping bracket, which supports the associated plunger only axially against the clamping force, to be rigidly mounted on the yoke. Preferably, however, this clamping bracket is pivotally mounted, so that a small axial relative movement of the yoke against the associated plunger is possible. This is advantageous because it can tolerate a slight axial play in the positioned assembly of the yoke with respect to the ram coupled to the axis of the grinder.

Fig. 1

eine Seitenansicht der Vorrichtung in Richtung der Y-Achse der Schleifmaschine,

Fig. 2

eine Draufsicht auf die Vorrichtung in Richtung der Z-Achse der Schleifmaschine,

Fig. 3

eine Schrägansicht der Vorrichtung,

Fig. 4

eine weitere Schrägansicht der Vorrichtung,

Fig. 5

eine Figur 3 entsprechende Ansicht im Axialschnitt der Vorrichtung,

Fig. 6

die Stößel der Vorrichtung in der Offenstellung und

Fig. 7

die Stößel der Vorrichtung mit gespanntem Werkstück.

In the following the invention will be explained in more detail with reference to an embodiment shown in the drawing. Show it

Fig. 1

a side view of the device in the direction of the Y-axis of the grinding machine,

Fig. 2

a top view of the device in the direction of the Z-axis of the grinding machine,

Fig. 3

an oblique view of the device,

Fig. 4

a further oblique view of the device,

Fig. 5

a FIG. 3 corresponding view in axial section of the device,

Fig. 6

the plunger of the device in the open position and

Fig. 7

the ram of the device with a clamped workpiece.

The clamping device according to the invention is in particular provided to clamp a workpiece on parallel ground surfaces purely frictionally. This makes it possible to make grinding operations on the circumference of the workpiece. An example of such workpieces are indexable inserts for machine tools. The tension in a C-shaped yoke between two axially movable rams allows a large pivoting range of the grinding wheel relative to the workpiece, so that not only the circumference of the workpiece can be processed, but possibly also the peripheral contour.

The device according to the invention is suitable for grinding machines in which the workpiece and the grinding tool, namely the grinding wheel, are linearly movable relative to one another in three spatial axes. The workpiece is clamped on a rotational axis aligned in the direction of one of these linear axes in order to be able to rotate the workpiece circumferentially relative to the grinding wheel. Another rotary axis allows the mutual pivoting of Workpiece and grinding wheel to machine the peripheral contour of the workpiece.

In the illustrated embodiment, the grinding machine is designed as a five-axis grinding machine, in which the workpiece and the grinding wheel in the three mutually orthogonal linear axes, the X-axis, the Y-axis and the Z-axis, are movable relative to each other. The workpiece is clamped by means of the clamping device described below on a rotatably rotatable rotary axis, the A-axis, whose axis of rotation lies in the X-axis and which is movable in the X-axis. The drive spindle of the grinding wheel is movable in the Y-axis and the Z-axis and can be pivoted by means of a rotational axis lying in the Z-direction, the C-axis. Other configurations and assignments of the linear axes and the rotational axes are possible within the scope of the invention and are covered by the protection.

The clamping device according to the invention has a yoke 10, which is C-shaped and consists of a straight yoke back 12 and two legs 14 and 16. The legs 14 and 16 are respectively formed at the ends of the yoke back 12 and protrude from the yoke back 12 substantially at right angles and parallel to each other in the same direction. In the first leg 14 and the second leg 16 each have a bearing bore 18 and 20 respectively. The axes of the bearing bore 18 of the first leg 14 and the bearing bore 20 of the second leg 16 are aligned coaxially and extend substantially parallel to the longitudinal extension of the yoke back 12th

In the bearing bore 18 of the first leg 14, a plunger 22 is rotatably mounted. The plunger 22 consists of a shaft 24 and a clamping pin 26. The shaft 24 is by means of a sliding bearing or a needle bearing 25 rotatably mounted in the bearing bore 18 of the first leg 14. The clamping pin 26 is interchangeable inserted coaxially in the second leg 16 facing the end of the shaft 24.

In the bearing bore 20 of the second leg 16 is rotatably and axially displaceable a counter-ram 28 is inserted. The axes of the clamping pin 26 and the counter-ram 28 are thus aligned axially.

The yoke 10 is fixedly mounted on the grinding machine, with the yoke being positioned so that the axes of the plunger 22 and the counter-slide 28 are aligned with the axis of rotation of a rotary drive shaft 30 of the grinding machine. In the illustrated embodiment, the rotationally driven axis 30 is the A-axis of the grinding machine. So that the tensioning device according to the invention can be attached to the grinding machine as an independent module, the shaft 24 can be inserted, for example, with a shaft cone 32 into a receiving cone 34 of the axle 30.

In order to mount the yoke 10 exactly positioned on the grinding machine, a support plate 36 is preferably used, which carries the yoke 10 and on which the yoke 10 is secured to the yoke back 12. The support plate 36 is mounted to a table 38 of the grinding machine carrying the A-axis 30 in such a manner that the axes of the plunger 22 and the counter-slide 28 are aligned with the A-axis 30. For this purpose, the support plate 36 can be mounted for example in T-slots of the table 38, which extend in the direction parallel to the A-axis 30 X-direction. In this X-direction, the support plate 36 is positionable with the yoke 10 so that the plunger 22 with the A-axis 30 can be coupled. For an exact height adjustment of the yoke 10, shims 40 can be inserted between the table 38 and the support plate 36. The table 38 is preferably movable in the X-axis.

At the end formed with the first leg 14 of the yoke 10, a first clamping bracket 42 is arranged. At the opposite, the second leg 16 associated end of the yoke 10, a second clamping bracket 44 is arranged. The clamping bracket 42 and 44 are each formed as a two-armed lever. The bearing point 46 of the first tensioning bow 42 and the bearing point 48 of the second tensioning bow 44 are each arranged at the ends of the yoke 10 so that their imaginary connecting line runs in the neutral fiber of the yoke back 12.

The first clamping bow 42 is arranged substantially parallel to the first leg 14. The first clamping bracket 42 engages with an arm 50 on the plunger 22 and supports it against axial application of force. In the illustrated embodiment, the arm 50 engages around the shaft 24 of the plunger 22 fork-shaped, wherein at the free ends of the fork-shaped arm 50 each have a cam roller 52 is mounted. The cam rollers 52 of the two forked ends of the arm 50 are diametrically opposed to each other in a circumferential groove 54 of the shaft 24. This allows the shaft 24 and thus the plunger 22 rotate relative to the arm 50, but not move axially. Alternative bearings are possible which cause rotation of the shaft 24 and axial pressure support. For example, a pressure sleeve with a thrust bearing enclose the shaft 24 and the arm 50 engages non-rotatably on the pressure sleeve.

The second clamping bow 44 is also designed as a two-armed lever and at its bearing point 48 in the plane of the C-shaped Joches 10 pivotally hinged. The second clamping bracket 44 engages with an arm 56 on the counter-ram 28. Upon pivoting of the second tension bow 44, the arm 56 pushes the counter-plunger 28 axially in the bearing bore 20 of the second leg 16 against the plunger 22. The arm 56 of the second tension bow 44 engages this on the rear end face of the counter-plunger 28. Between the formed with a coaxial pivot bearing 57 rear end face of the counter-ram 28 and the arm 56 of the second tension bow 44, a bearing needle 58 is inserted, which is perpendicular to the axis of the counter-ram 28 and perpendicular to the pivot plane of the second tensioning bow 44. The bearing needle allows the pivoting movement of the arm 56 of the second tensioning bow 44 to be converted into the linear axial movement of the counter-tappet 28 without radial forces acting on the counter-tappet 28 and its bearing in the bearing bore 20.

The bearings 46 and 48 of the clamping bracket 42 and 44 are attached to a tie rod 68 inserted into the yoke 10. As best in the sectional view of FIG. 5 can be seen, the tie rod 68 is formed as a circular cylindrical rod which extends in the longitudinal direction of the yoke back 12 substantially in the neutral fiber. The tie rod 68 is inserted into a through hole 70 of the yoke back 12. At the first leg 14 associated end of the tie rod 68 is screwed with a short thread 72 in the bore 70. To the thread 72 then extends the tie rod 68 with a radial clearance in the bore 70, whose inner diameter is slightly larger than the outer diameter of the tie rod 68. The tie rod 68 strikes at its end associated with the first leg 14 with an outer collar 74 outside at the end of the Yokes 10 on. The bearing point 46 of the first tensioning bow 42 is arranged on the end of the tie rod 68 projecting beyond the outer collar 74. The bearing 48 of the second tension bow 44 is disposed at the free end of the tie rod 68, which projects beyond the second leg 16 associated end of the yoke back 12. The bearings 46 and 48 of the clamping bracket 42 and 44 are thus connected to each other exclusively by the tie rod 68. The tie rod 68 is held with the thread 72 only in the yoke 10 without 72 forces are introduced from the tie rod 68 in the yoke 10 via the thread. It is obvious that the fixation of the tie rod 68 in the yoke 10 may also be provided in another axial position of the bore 70 and the tie rod 68. However, it must be ensured that no axial or radial forces are introduced into the yoke 10 by the tie rod 68.

Between the arm 50 opposite arm 60 of the first tension bow 42 and the arm 56 opposite arm 62 of the second tension bow 44, a power source is used, which is shown in the illustrated embodiment as a cylinder unit 64, in particular as a hydraulic cylinder unit 64. The cylinder unit 64 is arranged on the side opposite the legs 14 and 16 outside of the yoke 10 and extends substantially parallel to the Jochrücken 12. The cylinder unit 64 allows pivoting of the second tensioning bow 44 relative to the first clamping bracket 42nd

The first clamping bracket 42 may be connected at its bearing 46 fixed to the tie rod 68 and thus to the yoke 10. It is also possible that also the first clamping bracket 42 is mounted at its bearing point 46 in the plane of the yoke 10 pivotally mounted on the tie rod 68 and the yoke 10. A pivotable mounting of the first tension bow 42 allows the compensation assembly tolerances of the yoke 10 with respect to the A-axis 30 in the X-direction.

For receiving a workpiece 66, first the second clamping yoke 44 is pivoted by means of the cylinder assembly 64 so that the counter-ram 28 is axially pulled away from the ram 22. This position is for example in the FIGS. 1 and 6 shown. The workpiece 66 is brought for example by means of an insertion aid between the plunger 22 and the counter-ram 28. Thereupon, the cylinder unit 64 is extended to the second clamping bracket 44 in FIG. 1 to pivot counterclockwise. As a result, the second clamping yoke 44 with its arm 56 pushes the counter-ram 28 axially against the ram 22, whereby the workpiece 66 between the clamping pin 26 of the plunger 22 and the counter-ram 28 is clamped non-positively. The cylinder unit 64 can apply the high axial clamping force which is required so that the transverse forces acting on the workpiece 66 during the grinding process can not push the workpiece 66 out of its clamping position. The clamping bracket 42 and 44 form with the cylinder unit 64 and the plunger 22 and the counter-ram 28 is a kind of parallelogram. The high clamping force generated by the cylinder unit 64 acts exclusively axially on the plunger 22 and the counter-plunger 28, wherein this high axial clamping force is supported exclusively by the clamping bracket 42 and 44. The axial clamping force is introduced via the bearings 42 and 44 in the tie rod 68. Although this tensile force can lead to a small longitudinal extent of the tie rod 68, since the tie rod 68, however, is radially free in the bore 70 and is axially positioned only by means of the thread 72, are of the tie rod 68 no forces introduced into the yoke 10. The high axial clamping force can thus no deformation of the yoke 10 and in particular cause no bending of the legs 14 and 16. The exact axial alignment of the bearing bores 18 and 20 and thus of the plunger 22 and the counter-ram 28 is not affected by the high axial clamping force.

Since the entire force acting on the plunger 22 axial clamping force is supported by the parallelogram of the first clamping bracket 42 and second clamping bracket 44, causes this high axial clamping force no axial load on the mounting of the A-axis 30 in the grinding machine. The clamping device can therefore be mounted as a module on a rotatably driven axle of a conventional grinding machine, without requiring an increase in the storage of this axis in the grinding machine. Likewise, an entry of originating from the tension of the workpiece forces in the attachment of the yoke 10 is excluded. The bearing of the plunger 22 in the bearing bore 18 of the first leg 14 and the bearing of the counterpart 28 in the bearing bore 20 of the second leg 16 do not have to support radial forces, so that these rotary bearings rotate easily without being affected by the axial clamping force.

LIST OF REFERENCE NUMBERS

10

yoke

12

Jochrücken

14

first leg

16

second leg

18

Bearing bore of 14

20

Bearing bore of 16

22

tappet

24

wave

25

needle roller bearings

26

dowel pin

28

against ram

30

A axis

32

stem taper

34

receiving cone

36

support plate

38

table

40

underlay pieces

42

first clamp

44

second clamping bracket

46

Depository of 42

48

Depository of 44

50

Arm of 42

52

follower

54

circumferential groove

56

Arm of 44

57

pivot bearing

58

bearing needle

60

Arm of 42

64

cylinder unit

66

workpiece

68

tie rods

70

drilling

72

thread

74

outer collar

Claims (11)

Apparatus for clamping a workpiece for processing in a grinding machine, comprising a C-shaped yoke (10) having a yoke spine (12) and a first leg (14) and a second leg (16) angled in the same direction protrude from the yoke back (12), with a in the first leg (14) rotatably received plunger (22) and in the second leg (16) rotatably received counter-ram (28), wherein the plunger (22) and the counter-ram (28 ) are coaxially aligned with each other, wherein the plunger (22) is rotationally driven drivable and wherein the plunger (22) and the counter-plunger (28) by means of a power source (64) axially relative to each other are movable to the workpiece (66) with an axial clamping force between to tension the plunger (22) and the counter-ram (28),
characterized in that the yoke (10) is mounted mounted on the grinding machine, so that the axes of the plunger (22) and the counter-slide (28) with a rotatably driven axis (30) of the grinding machine are aligned, that the plunger (22) axially on the rotatably driven axis (30) can be coupled, that a first clamping bracket (42) is arranged on the yoke (10) and with an arm (50) axially supports the plunger (22) against the clamping force, that a second clamping bracket (44) pivotally the yoke (10) is arranged and with an arm (56) the axial direction of the counter - ram (28) that the bearing points (46, 48) of the first clamping bracket (42) and the second clamping bracket (44) at the opposite ends of the Joches (10) are arranged in the region of the yoke back (12) and that the clamping force on the clamping bracket (42, 44) in the plunger (22) and the counter-plunger (28) is introduced. Device according to claim 1,
characterized in that the yoke (10) has a tie rod (68) secured to the yoke (10) and extending through a bore (70) of the yoke (10) with radial play, and that the bearings (46, 48) of the clamping bracket (42, 44) at the opposite ends of the tie rod (68) are arranged. Device according to claim 2,
characterized in that the tie rod (68) is screwed with a thread (42) in the bore (70). Device according to one of the preceding claims,
characterized in that the clamping brackets (42, 44) are each designed as two-armed lever, one arm (50 or 56) on the plunger (22) or the counter-ram (28) engages and on the other arm (60 bzw. 62) attacks the power source (64). Device according to one of the preceding claims
characterized in that the power source is between the clamping bracket (42, 44) inserted cylinder unit (64). Device according to one of the preceding claims,
characterized in that the first clamping bracket (42) is pivotally mounted on the yoke (10). Device according to one of the preceding claims,
characterized in that the yoke (10) is adjustably mounted on the grinding machine positioned in an axis of the grinding machine parallel to the rotationally driven axle (30). Device according to one of the preceding claims,
characterized in that the first clamping bracket (42) surrounds the plunger (22) on its outer circumference with an axial thrust bearing. Device according to claim 8,
characterized in that the clamping bracket (42) engages around the plunger (22) fork-shaped and with cam rollers (52) in a circumferential groove (54) of the plunger (22) engages. Device according to one of the preceding claims,
characterized in that the second clamping bracket (44) engages the end remote from the plunger (22) end of the counter-ram (28). Device according to claim 10,
characterized in that the second clamping bracket (44) via a to the pivoting plane of the tensioning bow (44) and the axis of the counter-ram (28) vertically arranged bearing needle (58) on the pivot bearing (57) formed end of the counter-ram (28) engages ,

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