GB2103124A - Clamping chuck - Google Patents

Abstract

Jaws 3 in each of two diametrically opposed pairs thereof grip a tool 6 under the action of a spring-loaded sleeve 9 having inclined dovetail connections 8.1 with the jaws. Therefore axial movements of the sleeve positively move the jaws radially between gripping and tool releasing positions, the jaws being guided radially in, but held against axial movement in, the body 1. <IMAGE>

Description

SPECIFICATION Clamping chuck The invention relates to a clamping chuck, in particular for use in screw cutting, having a chuck body which can be connected to a drive shaft of a machine tool, and clamping jaws which are radially guided in the chuck body and which are secured against axial movement and are actuated by a positive connection provided on a clamping sleeve for transmitting axial thrust and pull, on clamping surfaces, which converge towards the axis of the chuck, the clamping sleeve being provided on the chuck body externally thereof.

In a clamping chuck of this kind, as disclosed in US patent specification No. 1509061, the clamping sleeve is mounted on the chuck body in such a way as to be rotatable and axially immovable. Arranged between the clamping jaws and the chuck body is a clamping disc on which the clamping jaws are guided for radial movement in dovetail-type guide means. The clamping jaws are also mounted to the clamping sleeve by way of a dovetail-type guide means which extends along the clamping surface thereof so that the clamping sleeve, the clamping jaws and the clamping disc are accordingly non-rotatably connected together, while the clamping disc and the clamping jaws can move axially with respect to the clamping sleeve.The clamping sleeve is supported with respect to the chuck body by way'of inclined surfaces which produce axial movement of the clamping disc relative to the chuck body when the clamping disc and the chuck body are turned relative to each other. The purpose of the abovedescribed arrangement is that, in a turning boring operation, the clamping operation is automatically effected by the torque which is produced in operating the arrangement, and which rotates the chuck body relative to the clamping disc. The resulting axial movement of the clamping disc causes the tool to be clamped.

A disavantage with this known clamping chuck is the structural and operational expenditure involved in the clamping disc, and also the fact that the clamping operation which is produced by the clamping disc cannot be used for clamping chucks which are subjected to an impact loading as in hammer drilling machines or drilling hammers, because the torque required for clamping the tool either is not produced at all, or is only of an insufficient magnitude.

The invention is based on the problem of so designing a clamping chuck of the aboveindicated kind that the clamping operation can be easily performed, without using a clamping disc, more particularly, irrespective of whether the clamping chuck is used for drilling boring or hammer boring, that in addition the clamping chuck is of a simple and operationally reliable construction, and that finally automatic retightening is possible.

According to the invention, this problem is solved by the provision of a clamping chuck having a chuck body that can be connected to a drive shaft of a machine tool, clamping jaws which are radially guided in the chuck body but are secured against axial movement, a clamping sleeve which is axially guided externally on the chuck body and provided with a positive connection to transmit an axial thrust and pull on the jaws by way of clamping surfaces that converge towards the axis of the chuck, and an axially operative clamping spring disposed between the chuck body and the clamping sleeve for urging the clamping sleeve in the direction of movement corresponding to a clamping movement of the clamping jaws.

The advance which is achieved by the present invention is substantially the fact that it is only axial movement of the clamping sleeve which is required for clamping and releasing the tool, the clamping force being produced by the clamping spring which at any time provides a re-tightening action. Although the force of the clamping spring may only be such that the clamping sleeve can be manually displaced against the force of the spring in order to be able to release a tool which is clamped in the chuck, there is in any case no need for a higher spring force when there is no need for the tool to be non-rotatably clamped in the clamping chuck or if the tool is non-rotatably clamped in the chuck by a positive connection between the tool and the clamping jaws in the rotary direction, for example by means of drive faces or the like, as for example in the case of screw cutting taps.The clamping chuck according to the invention is particularly suitable for uses of that kind.

A preferred embodiment of the invention is characterised in that the clamping jaws are provided in pairs with the jaws in each pair in diametrically opposite positions with respect to the axis of the chuck, that the chuck body comprises a guide member which carries the clamping jaws in parallel-wall guide slots and a cover member which closes off forward ends of the guide slots, and overlaps the clamping sleeve by means of a collar portion, and that the clamping jaws bear on the one hand against the rear ends of the guide slots and on the other hand against the cover member. The clamping jaws may jointly form a clamping opening which is of square cross-section, for a boring tool having a square shank.Desirably, for the purposes of forming the positive connection for transmitting thrust and traction forces, the converging clamping surfaces of the clamping sleeve are provided with longitudinal grooves of dovetail cross-section, into which the clamping jaws engage by means of mating portions which are of a corresponding dovetail configuration. It is also desirable for an annular space to be provided between the chuck body and the clamping sleeve, with the clamping spring being disposed in the annular space in the form of a helical compression spring and being supported axially against an annular shoulder on the chuck body on the one hand and against an annular shoulder on the clamping sleeve on the other hand..

An example of the invention is described in greater detail hereinafter with reference to the accompanying drawings in which: Figure 1 shows an elevation in axial section through a clamping chuck; Figure 2 shows a cross-section taken along line Il-Il in Figure 1.

Referring to the drawings, the chuck body is generally indicated therein by reference numeral 1. The chuck body 1 is provided in the usual manner with a mounting 2 for receiving a drive shaft (not shown) of a machine tool (also not shown). The clamping jaws 3 are radially displaceably guided in the chuck body 1 and are prevented from moving axially. More particularly, the clamping jaws 3 are provided in pairs with the jaws in each pair in diametrically opposite positions with respect to the axis 4 of the chuck.

The clamping jaws 3 together form a clamping opening 5 of substantially square cross-section for receiving a tool shank 6 of corresponding square configuration. The chuck body 1 comprises a guide member 1.1 which carries the clamping jaws 3 in parallel-wall guide slots 7, and a cover member 1.2 which closes off the guide slots 7 which are open at the front end towards the tool.

The clamping jaws 3 bear on the one hand against the bottom 7.1 of the guide slots 7 and on the other hand against the cover member 1.2, and are thereby held axially immovably. The cover member 1.2 is connected to the guide member 1.1 by screws 1.3. The clamping jaws 3 are also guided against clamping surfaces 8 which converge towards the axis 4 of the chuck from the cover member 1.2, in a direction towards the guide member 1.1, and are disposed on a clamping sleeve 9 which is disposed on the outside of the chuck body 1.The clamping jaws 3 are guided on the surfaces 8 by means of a positive or interfitting connection for transmitting axial thrust and pull, for which purpose the surfaces 8 are provided with longitudinal grooves 8.1 of dovetail cross-section, into which the clamping jaws 3 engage by means of mating portions 3.1 which are of a corresponding dovetail configuration. The clamping sleeve is prevented from rotating by way of the above-described positive connection. Accordingly, the clamping sleeve 9 is only capable of moving axially on the chuck body 1. The cover member 1.2 has a collar portion 1.4 which overlaps the clamping sleeve 9 in sliding engagement with the outside thereof.

Disposed between the chuck body 1 and the clamping sleeve 9 is an axially operative clamping spring 10 which urges the clamping sleeve 9 in the direction of movement corresponding to tightening the clamping jaws 3, that is to say, downwardly in Figure 1. The spring 10 is in the form of a helical compression spring and is disposed in an annular space 1 1 which is formed between the chuck body 1 and the clamping sleeve 9. The spring 10 bears axially against an annular shoulder 12 on the chuck body 1 at one end and against an annular shoulder 13 on the clamping sleeve 9 at the other end. The force of the spring 10 displaces the clamping sleeve 9 downwardly in Figure 1, which results in radial inward movement of the clamping jaws 3 relative to each other. If the clamping sleeve 9 is displaced axially upwardly against the force of the spring 10, the clamping jaws 3 are displaced radially outwardly.

Claims (5)

1. A clamping chuck having a chuck body that can be connected to a drive shaft of a machine tool, clamping jaws which are radially guided in the chuck body but are secured against axial movement, a clamping sleeve which is axially guided externally on the chuck body and provided with a positive connection to transmit an axial thrust and pull on the jaws by way of clamping surfaces that converge towards the axis of the chuck, and an axially operative clamping spring disposed between the chuck body and the clamping sleeve for urging the clamping sleeve in the direction of movenient corresponding to a clamping movement of the clamping jaws.

2. A chuck according to claim 1, in which the clamping jaws are provided in pairs with the jaws in each pair being in diametrically opposite positions with respect to the axis of the chuck, and in which the chuck body comprises a guide member which carries the clamping jaws in parallel-wall guide slots, and a cover member which closes off forward ends of the guide slots and overlaps the clamping sleeve in sliding engagement therewith, so that the clamping jaws bear on the one hand against the rear ends of the guide slots and on the other hand against the cover member.

3. A chuck according to claim 1 or claim 2, in which for the purposes of making the positive connection for transmitting axial thrust and pull, the converging clamping surfaces of the clamping sleeve are provided with longitudinal grooves of dovetail cross-section, into which the clamping jaws engage by means of mating portions of corresponding dovetail cross-section.

4. A chuck according to any one of claims 1 to 3 in which an annular space is formed between the chuck body and the clamping sleeve, the clamping spring being in the form of a helical compression spring disposed in the annular space and bearing axially against an annular shoulder on the chuck body on the one hand and against an annular shoulder on the clamping sleeve on the other hand.

5. A clamping chuck substantially as hereinbefore described with reference to the accompanying drawings.