DEVICE FOR CLAMPING A WORKPIECE TO BE MACHINED

Abstract

A device (1) for clamping a workpiece (2) to be machined, in particular a chuck or vice, the device comprising: (i) a chuck body (3) and a drive (5) fastened thereto, and (ii) at least one clamping jaw (6), which is coupled to the drive (5) in a driveable arrangement either directly or via intermediate elements (7) and which is or are held movably in or on the chuck body (3) in the direction of the workpiece (2). On the one hand, reliable and centric clamping of the workpiece (2) in a predetermined position is achieved and, on the other hand, the mounting of the clamping jaw carrier (9) on the chuck body (3) is free of backlash in the clamped condition in order to prevent any possibility of movement of the workpiece (2) relative to the chuck body (3). This is achieved by providing a free space (11) between the chuck body (3) and a clamping jaw carrier (9) accommodating the respective clamping jaw (6), in that an elastically deformable sleeve (12) is inserted in the free space (11), which sleeve (12) rests on the outside (8) of the chuck body (3) at two positions (21) spaced apart from one another, and in that a pressure chamber (14) is created between the chuck body (3), the sleeve (12) and the two support positions (21) thereof, into which pressure chamber (14) a medium (16) can be filled, by means of which a pressure force directed outwards acts on the wall (W2) of the sleeve (12) and bulges the latter in the direction of the clamping jaw carrier (9) between the support positions (21).

Claims

1. A device (1) for clamping a workpiece (2) to be machined, in particular a chuck or vice, the device comprising: a chuck body (3) and a drive (5) fastened thereto, and at least one clamping jaw (6), which is coupled to the drive (5) in a drivable arrangement either directly or via intermediate elements (7) and which is or are held movably in or on the chuck body (3) in the direction of the workpiece (2), characterised in that, a free space (11) is provided between the chuck body (3) and a clamping jaw carrier (9) which accommodates the respective clamping jaw (6), an elastically deformable sleeve (12) is inserted in the free space (11), which sleeve (12) rests on the outside (8) of the chuck body (3) at two positions (21) spaced apart from one another, and a pressure chamber (14) is created between the chuck body (3), the sleeve (12) and their two support positions (21), into which pressure chamber a medium (16) can be filled, by means of which a pressure force directed outwards acts on the wall (W.sub.2) of the sleeve (12) and bulges it out in the direction of the clamping jaw carrier (9) between the support positions (21).

2. The device according to claim 1, characterised in that, the wall thickness (W.sub.1) of the sleeve (12) in the region of the two support positions (21) is substantially thicker than the wall thickness (W.sub.2) of the sleeve (12) between the two support positions (21).

3. The device according to claim 1, characterised in that, the respective clamping jaw carrier (9) is held with a predetermined clearance (S) in or on the chuck body (3) and in that the clamping jaw carrier (9) is connected or clamped to the chuck body (3) without backlash in the clamped condition by the bulge (W) of the sleeve (12).

4. The device according to claim 1, characterised in that, a channel (15) which opens into the pressure chamber (14) is incorporated in the chuck body (3), a reservoir (17) which is filled with the medium (16) and is connected to the channel (15) is provided on the chuck body (3) or externally, and the medium (16) is pressed from the reservoir (17) into the pressure chamber (14) by means of a pump (18) and vice versa.

5. The device according to claim 1, characterised in that, the sleeve (12) is made of a metallic material, of plastic or of a fabric made of these materials.

6. The device according to claim 1, characterised in that, the sleeve (12) is fixed or held against the chuck body (3) by means of a cover (19).

7. The device according to claim 1, characterised in that, two O-ring seals (13) are inserted between the sleeve (12) and the pressure chamber (14), which O-ring seals (13) are sealed by these seals in a liquid-tight and gas-tight manner.

8. The device according to claim 1, characterised in that, an O-ring seal (13) is arranged in the region of each of the support positions (21) of the sleeve (12) on the chuck body (3).

9. The device according to claim 1, characterised in that, the movements of the respective clamping jaws (6) or of the clamping jaw carrier (9) and the bulge (W) of the sleeve (12) are separated from one another.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The drawings show a device in accordance with the present invention, which is explained in more detail below. Wherein:

[0016] FIG. 1 shows a device for clamping a workpiece, consisting of a chuck body in which a drive is provided by means of which a clamping jaw carrier and clamping jaws fastened thereto can be moved in the direction of the workpiece, in section and in the initial state,

[0017] FIG. 2 shows the device according to FIG. 1, in the clamping state of the workpiece,

[0018] FIG. 3a shows a detailed view of FIG. 1, and

[0019] FIG. 3b shows a detailed view of FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] The device 1 shown in FIG. 1 is used to clamp a workpiece 2 to be machined in a position-oriented manner and in a specified position in space. The device 1 can be designed as a chuck or a vice. The machining forces applied by a machine tool or centrifugal forces acting on the workpiece 2 must be supported by the device 1.

[0021] The device 1 consists of a chuck body 3 having a longitudinal axis marked with the reference number 4. A drive 5, for example in the form of a spindle drive, is installed in the chuck body 3, with which a clamping jaw carrier 9 that can be moved in the direction of the workpiece 2 is coupled in a drivable arrangement. The drive 5 acts on an actuating piston 7, which is coupled to the clamping jaw carrier 9. Three clamping jaws 6 are mounted on the clamping jaw carrier 9, so that when the piston 7 is actuated, both the clamping jaw carrier 9 and the clamping jaws 6 attached to it are transferred from the initial position according to FIG. 1 to the clamping position according to FIG. 2, i.e. the clamping jaws 6 are moved in the direction of the workpiece 2 and support this in a centred manner in space after the clamping operation is completed.

[0022] FIGS. 3a and 3b show that a free space 11 is incorporated in the chuck body 3, which runs between the chuck body 3 and the clamping jaw carrier 9. In addition, a channel 15 is incorporated in the chuck body 3, which is connected both to free space 11 and to an external storage tank 17. A medium 15 is stored in the storage tank 17, which can be pressed from this into the channel 15 by a pump 18.

[0023] In order to prevent the medium 15 from escaping from the free space 11, an elastically deformable sleeve 12 is inserted in this. The sleeve 12 has two wall thicknesses of different thicknesses: W.sub.1 and W.sub.2. The thicker wall thickness W.sub.1 is assigned to a support position 21 between the sleeve 12 and the chuck body 3. The sleeve 12 with the smaller wall thickness W.sub.2 runs between the two support positions 21, which are spaced apart from one another. The sleeve 12 can be made of a metallic material, of plastic or of a fabric comprising these two materials. Two O-ring seals 13 are provided to seal the free space 11 between the sleeve 12 and the chuck body 3 against water or gas. Consequently, the O-ring seals 13, the sleeve 12 and the chuck body 3 form a pressure chamber 14, which provides a liquid or gas-tight seal against the outside. The channel 15 emerges into the pressure chamber 14, so that the medium 16 can be injected by pump 18 from the storage tank 17 into the pressure chamber 14.

[0024] During the clamping process, the pressure chamber 14 is completely emptied according to FIG. 3a. Only when the clamping process is completed does the pump 18 force the medium 16 through the channel 15 into the pressure chamber 14. The medium 16 causes a deflection force acting in the direction of the clamping jaw carrier 9 which selects the wall thickness W2 of the sleeve 12 in the direction of the clamping jaw carrier 9. The bulge according to FIG. 3b of the sleeve 12 is schematically marked W. These bulges W therefore have a t-shaped or arc-shaped outer contour in a rotationally symmetrical chuck body 3. Due to the predominant bulge W of the sleeve 12, a force is produced which is directed at the clamping jaw carrier 9 and which presses the clamping jaw carrier 9 into the chuck body 3 without backlash. The bulge W of the sleeve 12 should therefore be permanently present during the machining process in order to fix the clamping jaw carrier 9 without backlash, so that the occurring machining forces are supported in such a way that the predetermined clamping position of the workpiece 2 is permanently maintained.

[0025] After completion of the machining process, the pressure chamber 14 is emptied, i.e. the medium 16 is drawn back by the pump 18 into the storage tank 17 through channel 15. The medium 16 can be a hydraulic oil or a gas mixture.

[0026] In order to prevent the sleeve 12 from slipping axially, it is held against the chuck body 3 by means of a cover 19, for example via a screw-thread connection.

[0027] The idea of the present invention can be applied to all chucks or clamping devices 1 with components that have a clearance S outside the powerflow. The powerflow causes the components to be fixed in the clamped condition. If the components that move relative to each other have a clearance relative to one another that lies outside the powerflow, then there is a clearance between them. An additional force can therefore be provided by means of the sleeve 12, the course of which runs outside the existing powerflow generated by the clamping process.