Clamping arrangement for positioning workpieces in a machine tool

Description

The present invention relates to a clamping device made according to the preamble of claim 1 for holding workpieces to be processed on a machine tool provided with a processing table, in particular a wire spark erosion machine.

[0002] If a tool or workpiece is to be clamped on a machine tool table, the workpiece or tool is usually first fixed on a pallet, which is then clamped onto the chuck. The clamping fixture itself is in most cases permanently connected to the working machine. The actuation of the fastening elements of the mounting fixture is usually manual, electromechanical, pneumatic or hydraulic.

[0003] From EP-B-0 202 452 a clamping and retaining system for a wire EDM machine is known. This clamping and fixing system has reference elements in the form of flat plate hardened steel strips which are fixed on the machine table of the EDM machine. The cross-section of these reference elements has a substantially dovetail contour with the top surface being wider than the bottom surface. The reference element has a side surface adjacent the top surface, forming a right angle with the bottom surface and the front surface and forming the Y reference. The reference element further has a plurality of pin-mounting through holes by which the reference element can be fixed and positioned in the corresponding tapped holes. on the machine table. The reference X is formed by a block cap connected to the reference element face having an abutment surface. The workpiece to be clamped is placed on the side surface of the reference element adjacent to the top surface and clamped with the clamps. Such a clamping and holding system could be especially suitable for lighter workpieces. Besides, the production of the reference elements is laborious and expensive.

[0004] US-A-5,019,129, considered to be the closest prior art, discloses a workpiece fixing system with a clamping frame including a stationary and movable clamping jaw. The fixing table on the machine side is provided with a dovetail-shaped hill on which a fixing plate provided with a corresponding recess is fixed by a clamp structure. A fastener is fixed on the retainer plate, which, also provided with a dovetail, is fixed to the fastening frame. The clamping structure for retaining the retaining plate on the fixing table includes spring loaded pins and a locking screw.

[0005] Finally, EP-A-1 402 985 discloses a clamping device, including a frame, to be attached to a machine table. The frame consists of two side arms and a spacer placed between them. The frame also has two guide elements extending between the side arms on which the sliding of at least one clamping slide is guided. The clamping slide is used to seat and clamp workpieces.

[0006] The object of the invention is to develop a clamping device for fixing the workpieces to be processed on a machine tool, in particular a wire EDM machine, provided with a machining table, such that it is simple and can be manufactured in an inexpensive manner, that it is stable and suitable for use. in particular for clamping workpieces of different shapes and that the workpieces can be clamped or detached quickly and simply.

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[0007] To this end, a fastening device according to claim 1 is provided according to the invention.

[0008] Preferred embodiments and further developments of the subject matter of the invention are described in dependent claims 2-15.

[0009] An embodiment of the fastening device according to the invention will now be explained in more detail with reference to the attached drawings. In the drawings it shows:

1 shows a perspective view of the various parts of the fastening device;

2 shows a top view of the fastening device;

3 is a cross section through the fastening device along line AA in FIG. 2;

4 shows a cross section through the clamping device along line BB in FIG. 2;

5 shows a cross section through the clamping device along line CC in FIG. 2;

6 shows a perspective view of the workpiece clamped on the workpiece holder.

[0010] Fig. 1 shows a perspective view of the fixing device. The clamping device serves to fix the workpieces to be processed on a machine tool (not shown) provided with a processing table 1, in particular a wire EDM machine. The machining table 1 of the machine tool is formed in this case by three rectangular plates 1a, 1b, 1c, arranged in a U-shape, between which there is a free working area, within which the machine tooling elements of the machine tools can freely move in the X, Y and Z directions It is understood that the illustrated processing table 1 is merely exemplary.

The fastening device comprises in the present example three identically made fastening strips 2, 3, 4 and three different object holders 5, 6, 7, the fastening device comprising at least one fastening strip 2, 3, 4 and at least one grip. of the workpiece 5, 6, 7. The respective clamping bar 2, 3, 4 is provided on the bottom surface facing the machine table 1 with a flat contact surface forming a bracket Z. Each of the three fastening strips 2, 3, 4 is permanently connected by means of fastening means, not shown in detail, - screws - to each plate 1a, 1b, 1c of the processing table 1. On the basis of the central fastening strip 3, the basic structure of the fastening strip will be explained in more detail. The fastening bar 3 is provided on its front face facing the machining center with an elongated projection 9 delimiting a substantially rectangular recess 10 between itself and the machine table. The fastening strip 3 thus has a substantially L-shaped cross-section. The projection 9 is provided with a plurality of threaded holes 11 for receiving the fastening elements in the form of screws. Two such screws 13 are represented representatively. The face 12 of the longitudinal projection 9 of the fixing strip 3 is ground flat and forms a stop for the respective object holder 5, 6, 7, as will be explained later. The bottom surface of the clamping bar 3, also ground flat, touches the top surface of the given plate 1b of the processing table 1 during clamping.

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[0012] In order to be able to locate the object holder 5, 6, 7 along the fastening strip, i.e. in the X or Y direction, stop pins are provided which can be positioned in the threaded hole 11 of the respective fastening strip 3 and form a lateral stop for the respective object holder. 5, 6, 7. Instead of the stop pins, also stop elements can be provided, fixed by screws 13 on the respective fastening strip. The stop elements are advantageous in particular when the workpiece rests on only one bar and / or when very small workpieces have to be clamped onto the bar. Even when identical units for the workpieces, i.e. the workpiece holders, are to be fixed with the workpiece repeatedly on the clamping bar, the stop elements or if the workpiece is clamped on two clamping bars staggered to each other by 90 °, no stops are required.

[0013] The first object holder 5 is provided with a clamping projection 15 for clamping the object holder 5 on the clamping bar 3. On the side of the clamping projection 15, the object holder 5 is provided with a reference surface 17. The clamping projection 15 has, on its upper surface, an obliquely ending fastening surface 16, on which the fastening screws 13 of the fastening strip 3 engage in such a way that the object holder 5 is pulled during clamping on the fastening strip 3 into the recess 10 and contacts its reference surface 17 with the surface 12 of the fastening strip 3 and is therefore oriented in the X or Y direction. The bottom surface 18 of the workpiece holder 5 is provided with a flat ground Z-shaped support which, when the workpiece holder 5 is locked, contacts the fastening bar 3 on the top surface of the machine table 1, so that the workpiece holder 5 is oriented in the Z direction. The object holder 5 is provided on the side facing away from the clamping projection 15 with a shoulder 19 which extends downwardly on the flat bottom surface 18, which is provided on its end with a strip-shaped projection 20, the surface of which is designed as a contact surface 21. This contact surface 21 extends in the same plane as the flat bottom surface 18 of the workpiece holder 5 and serves to support the workpieces in the Z direction. When the workpiece holder 5 is fixed on the clamping bar 3, the contact surface 21 of the bar projection runs in the plane of the machine table surface, and thus in the Z plane defined on the machine side. The workpiece holder 5 is further provided with a plurality of threaded holes 22 which are used to seat flange clamping bolts with which workpieces can be clamped onto the workpiece holder 5, as will be explained in more detail below. A workpiece holder 5 of this type is used in particular as a one-sided Z-support for larger workpieces, with larger workpieces preferably being held on at least two workpiece holders.

[0014] Of course, workpiece holders can also be provided, instead of the protrusion 19 running downwards, with a continuously flat bottom surface, so that their front end does not lie below the reference surface Z of the machine table. This is necessary in particular when the clamping device is to be used on a machine table with a continuously flat surface and without a working area extending under the upper surface of the machine table. Instead of the object holders with a continuously flat bottom surface, it is also possible to use a type of intermediate disk the thickness of which at least corresponds to the distance Z of the downward protrusion 19 of the workpiece holder 5, and which is supported when the respective workpiece holder 5 is clamped, so that the shoulder 19 extends downward. does not line up in the Z direction below the table top.

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[0015] The second workpiece holder 6 is made in the form of a 90 [deg.] Angle and is also provided on the front face with two tongue projections 24, 25, staggered to each other by 90 [deg.], The top face of which forms contact surfaces Z for the workpiece. The object holder 6 also has a plurality of threaded holes 32 which are used to seat the flange clamping bolts.

[0016] Along both internal surfaces, the object holder 6 is each provided with two vertically extending slots 29, 30 extending over the entire height of the object holder 6 and dividing the projections 24, 25 into individual sections. These slots 29, 30 enable the threading of EDM wire between a workpiece fixed on the workpiece holder 6 and the workpiece holder 6, as will be further explained below with reference to Figure 2.

[0017] On the rear face, the object holder 6 is provided with two clamping projections 26, 27, mutually staggered by 90 [deg.], By means of which the object holder 6 can be fixed on the securing strip. Between the two mentioned clamping projections 26, 27 is placed another clamping projection 28 which is positioned offset by 45 ° with respect to both of said clamping projections 26, 27. Thereby, the object holder 6 can be fixed on the fastening bar in a total of three different positions. Such a workpiece holder 6 is especially suitable for clamping with the exact position of rectangular and round workpieces. Furthermore, large workpieces can be clamped by means of the two workpiece holders 6 and possibly clamped rotated by 180 ° for processing.

[0018] The third object holder 7 is finally made in the shape of a rectangular holding frame. The workpiece holder 7 is provided with four frame surfaces 43,44,45,46 delimiting the central opening 42 for mounting the workpiece. A clamping projection 34 is formed on one surface 43 of the frame, and instead of a single clamping projection 34, two or three of them can naturally also be provided. The clamping projection 34 is provided on its top surface with a flat clamping surface 35, extending parallel to the bottom surface 36. The bottom surface 36 of the object holder 7 is made continuously flat. The two surfaces 43, 44 of the frame of the object holder 7 are provided on the inner surface with holes 37, 38, made for the mounting of the stop pins 39. The stop pin 39, located in the given hole 37, 38, protrudes slightly beyond the inner wall of the respective frame surface 43, 44 and forms a stop for the workpiece clamped in the workpiece holder 7. By providing such stop pins 39, the object holder 7 can be produced relatively inexpensively, since, for example, plain steel, i.e. not highly tempered steel, can be used as the base material for the production of the object holder 7, and its interior surfaces do not have to be further processed with high precision. since the abutment surfaces in the X and Y directions are only formed by the stop pins 39. The openings 37, 38 can naturally also be used to guide wire EDM when a workpiece is clamped on the workpiece holder 7.

[0019] Both other surfaces 45, 46 of the frame are provided with horizontally extending threaded holes 40, 41 which serve to drive clamping bolts (not shown) for clamping a workpiece into the hole 42.

[0020] In contrast to the two previously produced workpiece holders, the workpiece holder 7 which is designed in the form of a frame is not provided with lath projections whose upper surface forms contact surfaces Z for the workpiece. To be able to fix in hole 42 of the handle

Using the workpiece holder 7, workpieces in the Z direction, you can place the workpiece holder 7 on a flat plate, for example a ground stone plate, and then insert the workpiece into the workpiece holder 7, which is clamped in it with screws placed in the threaded holes 40, 41.

[0021] Fig. 2 shows the fixing device in a top view, each object holder 5, 6, 7 being fixed on the fixing bar. Namely, the first object holder 5 is clamped on the central fastening bar 3, while the second angularly shaped object holder 6 is fixed on the left fastening bar 2, and the third object holder 7 in the form of a fastening frame is fixed on the right fastening bar 4. Each object holder 5, 6, 7 is fixed on the respective fastening strip 2, 3, 4 by means of two fastening screws 13a, 13b; 13c, 13d; 13e, 13f.

[0022] From this view, the third clamping projection 28 of the angularly formed object holder 6 is also noticeable, arranged between the two clamping projections 26, 27 (FIG. 1) which are 90 [deg.] Offset from each other. Moreover, a diagrammatically illustrated workpiece 31 is shown which is fixed on an angularly shaped workpiece holder 6. Through slots 29, 30, which are recessed on the inner surface into the arms of the workpiece holder 6, made angularly, it is possible to pass - pull - the wire for EDM between the workpiece 31, fixed on the workpiece holder 6, and the workpiece holder 6. As a result, the workpiece 31 fixed on the workpiece holder 6 can be machined also from the rear surface by the EDM method, or the position of the workpiece 31 can be assumed automatically in a known manner by feeding wire for EDM from all sides.

[0023] Fig. 3 shows a cross section through the fastening device along line AA in Fig. 2. As can be seen, the clamping screw 13b presses against the clamping projection 15 of the first object holder 5 and thereby fixes it on the fastening bar 3. The clamping screw 13b presses its rounded front surface 14 against the sloping clamping surface 16 of the clamping projection 15 of the workpiece holder 5, so that the workpiece holder 5 is pressed against the table plate 1b with its flat bottom surface 18 on the one hand, and against the table plate 1b on the other hand by its rear reference surface 17 against flat face 12 of the clamping bar 3. Moreover, it can be seen that the contact surface 21 of the projection 20 intended to support the workpiece coincides with the surface 8 of the table plate 1b, and therefore of the processing table. The workpiece is thus positioned while supporting the surface 21 of the projection 20 of the workpiece holder 5 in the Z direction exactly in relation to the surface 8 of the processing table. Moreover, it is seen that the bottom surface 23 of the fastening bar 3 forming the support Z extends at right angles to the face 12 forming the abutment surface. In order to ensure that the object holder 5 rests with its rear reference surface 17 against the flat face 12 of the fastening strip 3, the clamping projection 15 is slightly shorter than the recess depth 10 of the fastening strip 3 (FIG. 1) in the horizontal direction. Thereby, in the clamped state of the object holder 5, there is a gap s between the end face of the terminal strip 15 and the rear wall of the recess. At the same time, this gap s also constitutes a dirt zone in which dirt can accumulate, without this having a negative effect on the accuracy of the fastening of the object holder fixed on the fastening bar, especially as the surface decisive for the positioning of the object holder, namely the flat face 12 of the bar attachment 3 can be easily cleaned.

[0024] Fig. 4 shows a cross section along line BB in Fig. 2. Also in this case, the set screw 13c presses its rounded front surface against the sloping fastening surface of the projection.

ΕΡ 1,834,724 Β1 of the clamping 26 of the workpiece holder 6, so that the workpiece holder 5 is pressed on the one hand with its flat bottom surface 33 forming a support Z against the surface 8 of the table plate 1a, and on the other hand with its rear reference surface against the flat face of the bar The contact surfaces of the projections 24, 25 for holding the workpiece coincide with the surface 8 of the table plate 1a.

[0025] After the clamping projection 26 has been inserted into the recess 10 of the fastening strip 2, the object holder 6 is held in its position by the fastening strip 2, even if the fastening screw 13c is not yet possibly tightened. This has the substantial advantage that the object holder 6 can be released after being roughly positioned on the fastening bar 2, without there being a danger that it tilts to the side.

[0026] Fig. 5 shows a cross section along the line CC in Fig. 2. In this case, the object holder 7, in the form of a fixing frame, is pressed by the clamping screw 13e only at right angles to the surface 8 of the table plate 1c, since the upper surface of the clamping projection 34 is flat and runs parallel to the lower surface 36 of the object holder 7. The workpiece holder 7 is pressed manually against the clamping strip 4 during clamping. After clamping the workpiece holder 7, its flat bottom surface 36 coincides with the top surface 8 of the table plate 1c. Also noticeable from this view is one of the horizontally extending threaded holes 41 for seating a clamping bolt (not shown) for clamping a workpiece to the workpiece holder 7.

[0027] Fig. 6 shows a perspective view of the workpiece holder 6 fixed on the clamping bar 3, together with the workpiece 47 clamped thereon. In order to position the workpiece holder 6 accurately along the clamping bar, 3, a stop is provided, not visible in this view. . The workpiece 47, for example shown in the shape of a cuboid, is clamped by means of two flanges 48, 49 on an angularly formed workpiece holder 6. Workpiece 47 is fixed on both side surfaces of the workpiece holder 6 and on both protrusions 24,25 and thus oriented in the X, Y, and Z directions. The workpiece 47, positioned on the workpiece holder, is largely freely accessible and can be machined. by means of a machine tool, such as a wire EDM machine.

[0028] The fixing device constructed according to the invention is modular in construction, using on the one hand one or more fixing strips and, on the other hand, using object holders of different shapes. By providing for different workpiece holders, virtually any workpiece can be fixed quickly, simply and possibly with exact position on one or more clamping bars. Instead of the previously described item holders, item holders deviating from the above embodiments can naturally be provided within the scope of the invention. For example, object holders in the form of so-called pendulum holders or pendulum heads can be used. A further advantage is that the clamping device is not very susceptible to soiling and is very stable, so that heavy and large workpieces can also be held on it. By providing workpiece holders 5, 6, 7, the respective clamping projection 15, 26, 27, 34 of which is adapted to the recess of the respective clamping strip 3, the clamping device has a further advantage in connection with large and / or heavy workpieces. in that it is possible to place the object holders with the workpiece fixed on them by the operator with both hands in the approximate position and then leave them. The given object holder 5, 6, 7 is held

ΕΡ 1,834,724 Β1 then through the clamping projection 15, 26, 27, 34, inserted into the recess 10, even if the object holder 5, 6, 7 tilts slightly downwards. After that, the object holder 5, 6, 7 can be clamped on the respective fastening bar with the fastening screws. It behaves in the same way while unlocking it. This is a decisive advantage over most other fastening devices, since the object holder usually has to be held with one hand, while at the same time the fastening elements have to be tightened or detached with the other hand.

Marker list:

[0029]

1. Machining table

2. Fastening strip

3. Fastening strip

4. Fastening strip

5. Item holder

6. Item holder

7. Item holder

8. Surface

9. Performance

10. Choosing

11. Tapped hole

12. Flat face

13. Bolts

14. Cave face

15. Clamping lug

16. Fixing surface

17. Reference area

18. The bottom surface

19. Disjunction

20. Performance

21. Contact surface

22. Tapped hole

23. Flat bottom surface (mounting bar)

24. Performance

25. Performance

26. Clamping lug

27. Clamping lug

28. Clamping lug

29. Gap

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30.

Gap

31.

32.

33.

34.

35.

36.

37.

The workpiece

Tapped hole

Flat bottom surface (workpiece holder)

Clamping lug

Fixing surface

Flat bottom surface

Hole

38.

Hole

39.

40.

41.

42.

43.

44.

45.

46.

47.

48.

A stop pin

Tapped hole

Tapped hole

Central opening

First frame surface Second frame surface Third frame surface Fourth frame surface Workpiece Flange

49.

Collar

50.

51.

52.

53.

54.

55.

56.

57.

58.

59.

60.

61.

62.

63.

64.

65.

66.

67.

68.

69.

70.

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