GB2110965A

GB2110965A - Jaws for use in clamping devices

Info

Publication number: GB2110965A
Application number: GB08218274A
Authority: GB
Inventors: Josef Steinberger; Heinz Beckers
Original assignee: FORKARDT PAUL GmbH; Paul Forkardt GmbH and Co KG
Current assignee: FORKARDT PAUL GmbH; Forkardt Deutschland GmbH
Priority date: 1981-07-28
Filing date: 1982-06-24
Publication date: 1983-06-29
Also published as: DE3150966C2; GB2110965B; ES265446Y; FR2510441B1; FR2510441A1; IT8222594A0; IT8222594A1; DE3150966A1; CH655262A5; ES265446U; IT1152472B

Abstract

To position and hold a clamping insert (5), in a site on a clamping jaw 1 the insert is located and supported in a recess having a bearing surface (3) inclined to the clamping direction and an abutment surface (4) extending at an angle thereto. The insert engages the bearing surface (3) of the clamping jaw and is provided with a claw-like projections (5g). A holding element (6) for preventing the insert from falling out of the recess is so mounted that it does not hinder automatic adjustment of the insert (5) relative to the clamping jaw (1), the longitudinal axis of the holding element extending at an acute angle to the bearing surface and preferably also the the abutment surface. <IMAGE>

Description

SPECIFICATION Clamping jaws This invention relates to a clamping jaws for clamping devices, for example rotary lathe chucks.

Clamping jaws provided with clamping inserts are known in great variety of forms. Besides case-hardened metal clamping inserts there are available also interchangeable hard clamping claws, which are secured by means of screws to the clamping surface of the clamping jaws or possibly in a recess formed in one of the clamping surfaces. The known forms of such clamping jaws have the disadvantage, that the location of the clamping inserts is determined by the screws securing them, of which the force which can be applied is limited, so that in general the necessary precision of location is not achieved or the required high capacity for a substantial machining effort cannot be transmitted.

According to the present invention there is provided a clamping jaws for a clamping device comprising an exchangeable clamping insert, supported in a recess of the jaws at a bearing surface inclined to the clamping direction and at an abutment surface inclined at an angle thereto.

According to a further feature of the invention the clamping insert engages the bearing surfaces of the clamping jaws with lateral projections in the manner of a cramp. Thus, the clamping insert on exchange adjusts itself automatically relatively to the clamping jaws. It is only necessary, to apply the clamping insert to the inclined bearing surface, the laterally upstanding projections providing for location trans tersely to the clamping jaws and the ultimate location of the clamping insert relative to the clamping jaws is provided by application of pressure in the clamping direction and consequent abutment against the abutment surface. By this positive connection it is possible to achieve a high torque transmission for accommodating high machining forces.

According to a further feature of the invention the clamping insert is secured against dropping out by at least one holding element for example a set screw or bolt which does not interfere with the aforesaid automatic adjustment of the clamping insert relative to the clamping jaws. By an over-dimensioning of the bore penetrated by the shank of the set screw and of the recess for the screw head the screw only serves for securing of the clamping insert on the clamping jaw, if no workpiece is held, and when the clamping chuck is at rest, and so that no interference to the automatic adjustment of the clamping insert arises corresponding to the bearing surfaces and the abutment surface.

A further feature of the invention consists in that the holding element extends with its longitudinal axis at an acute angle to the bearing surface. In this way it is ensured, that even in the case when the holding element is to exert a tightening action on the clamping insert, for example by a screw serving as a holding element to effect tightening, the automatic adjustment of the clamping insert along the bearing surface and towards the abutment surface will not be impaired, since the clamping insert is drawn both against the bearing surface and also against the abutment surface substantially with the longitudinal axis of the holding element in synchronism with the action of the holding element.By this provision for adjustment any erroneous action on the part of the operator which might hinder or even eliminate the exclusive automatic adjustment of the clamping insert towards the bearing surface and the abutment surface by the holding element is avoided.

In one preferred embodiment the holding element can extend with its longitudinal axis in the radial direction of the clamping jaws, since the bearing surface is inclined to the clamping direction. A particularly favourable arrangement of the holding element in accordance with a further feature of the invention is provided when the holding element extends with its longitudinal axis at an angle inclined both to the bearing surface as also to the above abutment surface. In this case to enable securing action by the holding element the clamping insert is formed with an acute angle corner defined by the bearing surface and the abutment surface so that the generation of a gap both between the clamping insert and the bearing surface as also between the clamping insert and the abutment surface will be avoided.

In a preferred embodiment the clamping insert is made in the form of a claw with overhanging projections. These projections of the clamping insert are preferably arranged on circular arcs corresponding substantially with the clamping diameter of the workpiece. This is curved for external clamping in a concave manner and with internal clamping in a convex manner, so that a high tightening force is effected by the sharp projections.

In a preferred embodiment an abutment rod extends radially of the axial location of the workpiece. This abutment rod is made preferably of a soft material and can be exchanged or shortened in accordance with requirements, if axial location of the workpiece to be gripped relative to the clamping jaws is to be changed.

The invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings, in which: Figure 1 is a fragmentary side view of a first embodiment of chuck in accordance with the invention with a clamping insert in section arranged to provide external support for a workpiece; Figure 2 is an end view of the chuck of Figure 1; Figure 3 is a side view of a second embodiment with a clamping insert in section arranged to provide internal support for a workpiece; Figure 4 is an end view of the chuck of Figure 3; and Figure 5 is fragmentary side view, to an enlarged scale, of a third embodiment showing several modes of mounting of the clamping insert in the chuck.

In the embodiments the clamping jaws of a rotary chuck are considered, which at the rear face is provided with a rowoftrapezoidal profile teeth 2 in order to facilitate adjustment relative to a drive jaw of the chuck. The chuck and the drive of the clamping jaws 1 are not illustrated in the drawing as they are wholly conventional. A recess is provided in the jaws 1 which defines a bearing surface 3 inclined to a radially extending clamping direction and an abutment surface 4 extending thereto at an angle. The inclination of the bearing surface 3 is made such that a clamping insert 5 constructed with a complementary opposing surface is displaced by the clamping force against the bearing surface 3, until it comes into abutment with the abutment surface 4.In this way a precise definition of location of the clamping insert 5 is provided both in the axial and also in the radial direction.

As is apparent in Figures 2 and 4, the inserts 5 each possess lateral projections 5a, which engage like claws against the bearing surface 3 of the clamping jaws 1. The clamping surfaces of the cutter inserts 5 are formed by serrations 5b, of which the tips in the case of external gripping according to Figures 1 and 2 lie on a concave circular arc in relation to the clamping jaws 1 and in the case of internal gripping according to Figures 3 and 4 lie on a convex circular arc in relation to the clamping jaws 1. These circular arcs are indicated respectively in Figures 2 and 4. In Figures 1 and 3 the corresponding workpieces W are illustrated. A set screw 6 is provided in order to maintain engagement of the clamping inserts 5 in the clamping jaws 1 with the chuck stationary and in the absence of a workpiece W.The bore provided in the clamping insert 5 for this set screw 6 has a larger diameter than the screw shank and furthermore the recess accommodating the head of the screw 6 in the clamping insert 5 is so dimensioned that an automatic location adjustment of the clamping insert 5 relative to the clamping jaws 1 is not subjected to interference by the screw 6.

In the third embodiment illustrated in Figure 5 a clamping jaws 1 is again illustrated, which is provided at its rear side with a row of trapezoidal teeth 2. As with the hereinbefore described embodiments the clamping jaws have a bearing surface 3 inclined to the radially extending clamping direction and an abutment surface 4 extending thereto at an angle, the abutment surface 4 again lying in a radial plane of the clamping jaws 1.

The clamping insert 5 has two lateral projections 5a and is held by a holding element in the clamping jaws 1, which again takes the form of a set screw 6.

The bore provided for this screw in the clamping insert 5 has a larger diameter than the screw shank.

Also the recess provided by the head of the screw 6 is so dimensioned in the clamping insert 5, that the screw head does not hinder the automatic location adjustment of the clamping insert 5 relative to the clamping jaws 1.

Differing from both of the hereinbefore described embodiments, in which the set screws 6 are mounted with their longitudinal axes 6a extending in the radial direction of the clamping jaws 1, the screw 6 illustrated in broken lines in Figure 5 extends with its longitudinal axis 6a at an acute angle 8 to the bearing surface 3. In Figure 5 two further possibilities are indicated by chain lines for the orientation of the screw 6 in the clamping jaws 1. These indicated positions render it apparent that even in these two extreme cases the longitudinal axis 6a of the screw 6 extends at an acute angle 8 to the bearing surface 3.

This is apparent also when it is the case that the screw 6 is orientated radially.

The location of the set screw 6 illustrated in full lines in Figure 5 renders apparent that the longitudinal axis 6a of the screw 6 also extends at an acute angle 9 to the abutment surface 4, if it is inclined slightly out of the radial orientation outwardly in the direction towards the series of trapezoidal teeth 2. In this way the screw 6 is provided with clearance and guidance in the clamping insert 5 during tightening so that the clamping insert 5 is drawn accurately into the corner of the clamping jaws 1 defined by the bearing surface 3 and the abutment surface 4. In order to achieve independently of the shape of any given clamping jaws 1 an accurate axial location of the workpiece, an abutment rod 7 is provided in each embodiment.This is screwed in the axial direction into the clamping jaws 1 and serves with its end surface as an abutment for the workpiece as is apparent in Figures 1, 3, and 5. When there is to be a change in the axial location of the workpiece W relative to the clamping jaws 1, the abutment rod 7 can be exchanged or its axial length can be foreshortened. For the latter purpose it is preferably made of material which can be readily machined.

With the hereinbefore described construction the insert 5 is held in its pre-determined location both in the radial and axial and even in the tangential directions by the clamping force alone, since it is displaced along the inclined bearing surface 3 to the abutment provided by the abutment surface 4 extending thereto at an angle. The construction of clamping jaws 1 and insert 5 gives rise to the further advantage, that for the chucking of various workpieces it is no longer necessary to change completely the jaws, but only the clamping inserts, which because of their small volume are manufactured of high value material and can be adapted to any specific clamping problem.

Claims

1. A clamping jaws for a clamping device comprising an exchangeable clamping insert, supported in a recess of the jaws at a bearing surface inclined to the clamping direction and at an abutment surface inclined at an angle thereto.

2. A clamping jaws according to Claim 1 wherein the clamping insert engages like a claw on the bearing surface of the clamping jaws with lateral projections thereof.

3. A clamping jaws according to Claim 1 or 2, wherein the clamping insert is secured by at least one holding element against falling out which does not hinder automatic adjustment of the clamping insert relative to the clamping jaws.

4. A clamping jaws according to any one of Claims 1 to 3, wherein the holding element extends with its longitudinal axis at an acute angle to the bearing surface.

5. A clamping jaws according to Claim 4 wherein the holding element is oriented with its longitudinal axis in the radial direction of the clamping jaws.

6. A clamping jaws according to Claim 4, wherein the holding element extends with its longitudinal axis at an inclined angle both to the bearing surface as also to the abutment surface.

7. A clamping jaws according to any one of Claims 1 to 6 wherein the cutter insert is formed with serrations.

8. Aclamping jaws according to Claim 7 wherein the serrations of the clamping insert are arranged on a circular arc corresponding to the curvature of the workpiece.

9. A clamping jaws according to any one of Claims 1 to 8 wherein the clamping jaws incorporates an abutment rod serving to locate the workpiece axially

10. A clamping jaws for use in a clamping device comprising a clamping jaw body having a recess therein for receiving a clamping insert, the recess having a bearing surface inclined to the direction of application of the clamping force and an abutment surface disposed at an angle to the bearing surface, and a clamping insert received in the recess and having surfaces complementary to the bearing and abutment surfaces, the clamping force applied to a workpiece serving automatically to locate the insert against the abutment surface.

11. A clamping jaws substantially as hereinbefore described with reference to Figures 1 and 2: Figures 3 and 4 or Figure 5 of the accompanying drawings.