GB2074056A

GB2074056A - A hydraulic clamping device

Info

Publication number: GB2074056A
Application number: GB8111838A
Authority: GB
Original assignee: SCHREM WERKZEUGFAB ALBERT
Current assignee: SCHREM WERKZEUGFAB ALBERT
Priority date: 1980-04-17
Filing date: 1981-04-14
Publication date: 1981-10-28
Also published as: IT8120809A0; JPS56163812A; FR2480658A1; DE3014744A1

Abstract

A hydraulic clamping device for clamping a part (22) to a machine component (25) includes a body member (1) and a piston member (6) slidable relative to the body member. Either the body member (1) or the piston member (6) is attached to the machine component (25). The body member (1) is provided with a stop face (23) against which the part (22) to be clamped is pressed by the piston member (6). A pressure screw (18) is arranged to actuate the piston member (6) to press the part (22) against the stop face (23) by way of a hydraulic medium. The clamping device is separate from the machine component and thus it is not necessary to perform the clamping operation in the machine component itself. <IMAGE>

Description

SPECIFICATION A hydraulic clamping device The present invention relates to a hydraulic clamping device for clamping a part, for example, a tool or a workpiece, to a machine component.

German Offenlegungsschrift No. 25 52 873.8 describes a hydraulic clamping fixture in which a hydraulically operated piston is arranged to press the part to be clamped against a stop located on the machine component. However, as the stop is located on the machine component, the clamping operation must always be effected on the machine component itself, and this can be disadvantageous if it is intended to perform tool-changing or workpiecechanging by automatic means.

It is an object of the invention to propose a hydraulic clamping device enabling the part to be clamped to be clamped independently of, and separately from, the machine component.

According to the present invention there is provided a hydraulic clamping device for clamping a part to a machine component, the device comprising a body member having a stop face, a piston member for pressing a part to be clamped against said stop face, one of said body member and said piston member being attachable to a machine component, and a pressure screw arranged to actuate said piston member by way of a hydraulic medium.

As the stop, against which the part to be clamped is clamped, is provided on the body member the clamping operation can be carried out spatially separated from the machine component and the latter itself no longer needs to have a stop provided thereon.

Embodiments of the present invention will hereinafter be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 shows a longitudinal section of a hydraulic clamping device of the present invention, and Figure 2 shows a cross-sectional view taken along the line 2-2 of Figure 1 but showing a further embodiment of the invention.

The embodiment of a hydraulic clamping device illustrated in Figure 1 comprises a body 1 having a circular cylindrical shoulder 2. Circular cylindrical extensions 3 and 4 project from opposite ends of the shoulder 2, the extensions 3 and 4 extending coaxially with the shoulder 2. A cavity 5, which is preferably circular cylindrical, extends in the shoulder 2 and in the extensions 3 and 4, and possesses a larger diameter within the extension 4. A circular cyldindrical piston 6 is slidably received in the cavity 5, the outer wall of this piston 6 being sealed with respect to the cavity 5 by means of two ring-seals 7 and 8. The ring-seal 8 is supported against a shoulder 9 of the piston, this shoulder 9 being located in larger diameter portion of the cavity 5 within the extension 4.The end of the shoulder 9 facing away from the seal 8 is supported on a cup spring 11, which in its turn abuts against a screw part 12. The screw part 12 which, as can be seen from Figure 1, has bores extending therethrough, is ersrowArS intn the. extension 4. As seen in Fiqure 1, the cup spring 11 urges the piston 6 towards the left.

A clamping disc 13 is securely screwed onto the end of the piston 6 opposite to the shoulder 9. The piston 6 contains a cavity 14, which extends axially and in which a pressure piston 15 can be moved.

One end of the piston 15 is sealed from the cavity 14 by means of a seal 16. A clamping screw 18, provided, for example, with an internal hexagon, acts on the opposite end of the pressure piston 15, a ball 17 being interposed between said piston 15 and said screw 18. The screw 18 can be screwed into an internal thread provided in the piston 6.

The cavity 14 is connected, via a passage 19, with an annular chamber 21, located between the inner end surface of the shoulder 2 and the ring-seal 8. The cavity 14, the passage 19, and the chamber 21 are filled with a hydraulic medium.

A part 22 which is to be clamped is provided with a corresponding hole and is pushed onto the external periphery of the extension 3. In the embodiment illustrated the part 22 is a tool for a gear shaping machine. When fitted on the extension 3, the part 22 to be clamped is in contact with a stop face 23 of the base body 1, and is secured in position by the clamping disc 13 which is attached afterwards.

The body 1 is securely attached to a machine component 25 by means of four screws 24, which extend through the shoulder 2. It is possible, for example, for the machine component 25 to be designed to be movable axially backwards and forwards, orto rotate about its axis (as a stub shaft-extension).

The hydraulic clamping device illustrated in Figure 1 functions in the following manner: The body 1 is secured to the machine component 25 by means of the screws 24. Therafter, the part 22 which is to be clamped is pushed onto the extension 3. The clamping disc 13 is then screwed onto the threaded end of the piston 6 but is not tightened. The clamping screw 18 is then screwed in so that the piston 15 and the seal 16 are slid to the right as shown in Figure 1. A hydraulic pressure is thereby created in the chamber 21, between the inner wall of the shoulder 2 and the shoulder 9 which is located on the piston 6, and the piston 6 is pushed forward under the action of this pressure, towards the right as shown in Figure 1.The part 22, which is to be clamped, is thus pressed, by the clamping disc 13 which acts on it, firmly against the stop face 23, and is thereby attached to the machine component 25 with the required, precisely-adjustable force. In order to release the clamped part 22, the clamping screw 18 is rotated in the opposite direction and the clamping disc 13 is then removed, so that the part 22, which was clamped, can be removed again from the extension 3.

in the embodiment illustrated in Figure 1,the screws 24 are arranged in the shoulder 2 such that the body must be attached to the machine component 25 before the part 22, which is to be clamped, can be clamped between the stop face 23 and the clamping disc 13. In an alternative embodiment, the part 22 can be designed in such a way, or the clamping screws 24 can be arranged in the shoulder 2 in such a way, as to enable the part 22, which is to be clamped, and is already clamped securely between the clamping disc 13 and the stop face 23, to be attached afterwards to the machine component 25. In particular, pre-clamping of the part 22 on the hydraulic clamping fixture, is possible in embodiments of the invention in which the extension 4 of the body 1 can be screwed, by means of an external thread, into an internal thread of the machine component 25.The same also applied in embodiments of the invention in which the exterior of the extension 4 is in the shape of a circular cylinder or a cone, and can be securely attached in this manner, as known per se, to the machine component 25.

When the pressure screw 18 is released, the cup spring 11,which alternatively may be a helical compression spring, pushes the piston 6 to the left, as shown in Figure 1, and thus lifts the clamping disc 13 from the clamped part 22.

As can be seen from Figure 1, an additional cylindrical cavity 26 is provided in the shoulder 2 of the base body 1, this cavity 26 being connected, via a passage 27, to the annular chamber 21, so that the same hydraulic pressure as in the chamber 21 always prevails in said cavity 26. In the embodiment shown in Figure 2, a piston 28, with a seal 29, is slidingly located in the cavity 26 which extends substantially tangentially to the annular chamber 21.

At the peripheral surface of the shoulder 2, the cavity 26 is closed by a screw-plug 31, which has a central bore 32. A rod 33 extends through the bore 32, this rod being securely attached to the piston 28. A compression spring 34, located between the piston and the screw-plug 31, presses the piston 28 as far as possible into the cavity 26. The device described acts as a clamping-force indicator and, as such, is known per se. If a hydraulic pressure builds up in the annular chamber 21, this pressure also acts on the piston 28, which slides downwardly as shown in Figure 2 under the action of this pressure and in so doing pushes the end of the rod 33 out of the screw-plug 31. The position of the end of the rod 33 is thus a measure of the prevailing hydraulic pressure and thus also a measure of the clamping pressure applied.

Figure 2 shows a section along the line 2-2 in Figure 1, but of an embodiment is modified with respectto Figure 1. In the case of the embodiment shown in Figure 2, the pressure screw 18 is replaced by a pressure screw 48, which acts on a piston 45 which can slide in a cavity 44. In this embodiment the cavity 44 extends - in exactly the same way as the cavity 26 of the clamping-force indicator - substan tiallytangentiallytothe annular chamber 21, and is connected to this chamber 21 via a passage 49.

Consequently, a hydraulic pressure can also be built up by screwing in the pressure screw 48 which is located, according to Figure 2, in the chamber 21, and it is thereby possible to clamp a part 22 between the stop face 23 and the clamping disc 13, in the manner described with reference to Figure 1.

In the case of other embodiments of the invention, which are not illustrated, a plurality of pressure screws 18,48 can be provided, with associated cavities 14,44, and, for example, one pressure screw, or a plurality of pressure screws 48, located in the base body 1 tangentially to the annular chamber 21, can be combined with a pressure screw 18, located axially in the cylinder 6. It is also possible to provide one pressure screw 48, or a plurality of pressure screws 48, extending tangentially in accordance with Figure 2, and to locate a clampingforce indicator axially in the piston 6, in place of the pressure screw 18.

In yet another embodiment of the invention, the screw connection between the clamping disc 13 and the piston 6 can also be replaced by a bayonet catch or similar fastening. It is also possible to arrange for the piston 6 to be immovably attached, in a known manner, to the machine component 25, so that, in this case, the base body 1, which then is not attached to the machine component, bears, under pressure, with its stop face 23 against the part 22 which is to be clamped, whilst in the case of the embodiment illustrated in Figure 1,the clamping disc 13 pulls the part 22, which is to be clamped, towards the stop face 23. The part 22 which is to be clamped, can be a tool which moves with the machine component 25.

Said part 22 can alternatively be a workpiece which is held stationary and is then machined by a moving tool.

Claims

1. A hydraulic clamping device for clamping a part to a machine component, the device comprising a body member having a stop face, a piston member for pressing a part to be clamped against said stop face, one of said body member and said piston member being attachable to a machine component, and a pressure screw arranged to actuate said piston member by way of a hydraulic medium.

2. A clamping device according to Claim 1, wherein the piston member comprises a piston slidably received within a bore in the body member, and a clamping disc carried by the piston and arranged to press the part against said stop face, and further comprising spring means acting on the piston such that the part is pressed against the stop face against the action of the spring means.

3. A clamping device according to Claim 1 or 2, wherein the body member is provided with a flange for connection to a machine component.

4. A clamping device according to Claim 1 or 2, wherein the body member has a cylindrical or conical shaped portion for insertion into a complementary cavity in the machine component.

5. A clamping device according to Claim 2, wherein the clamping disc is attached to the piston by screwing or by a bayonet catch.

6. A clamping device according to any preceding Claim, wherein one or more pressure screws are located in the body member.

7. A clamping device according to any preceding Claim, wherein the pressure screw extends axially within the piston member.

8. A clamping device according to any preceding Claim, wherein one or more clamping-force indicators are provided in the body member and/or in the piston member.

9. A hydraulic clamping device for clamping a part to a machine component substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.