GB2187121A - A workpiece clamping device - Google Patents

Abstract

A workpiece clamping device comprises a base portion (11) having a screw clamping member (18, 19, 20) fixable to a support such as a workbench, and a pivoted cam-shape clamping member (24) having a convexly curved surface (25) and a pin (31) by which it can be engaged in holes (21) in the base portion (11). The base portion (11) has an upstanding abutment (12) against which a workpiece can be clamped by turning a handle (40) attached to the clamping member (24) whilst the pin (31) is engaged in a selected hole (21) depending on the size of the workpiece to be clamped between the clamping member (24) and the abutment (12). The clamping device may be made of wood, plastics or metal. <IMAGE>

Description

SPECIFICATION A workpiece clamping device The present invention relates to a workpiece cam ping device, and particularly to a device having a rapid, easy operating action which does not involve laboriouslyturning the screwthread.

Although it is known to utiulise a vice for securing a workpiece in position, vices are usuallyfixed pieces of equipment dedicated to the working operations to be performed thereon. However, there are many situations where it is required to secure a workpiece in a fixed position in orderto be able to perform working operations on it, and in circumstances where a work bench and/or vice are not readily available. The present invention seeks to provide a simple workpiece securing device which can be attached to a fixed support, or can, indeed, be formed to incorporate a fixed support, by means of which it is possible simply and quickly to clamp a workpiece in a desired position to leave both hands of the operator free to perform the required working operations.

The present invention finds particular utility in schools where, with large classes of pupils, it is not always possible to have available a corresponding number of work benches for teaching craft work, or even, in some cases, anywork benches atall, but where, of necessity, the work can only be performed by securing workpieces fixedly in position. The present invention will also be of particular usefulness in the homeforthe home handiman.

The present invention seeks, therefore, to provide an economic, easy to operate and simple device which is both safe, small in size and allows conventional school equipment to be adapted for other purposes than its primary use.

According to one aspect of the present invention there is provided a workpiece clamping device in which the clamping force is applied byturning a cam member about an axis extending transversely ofthe line of action of the clamping force.

Such a device avoids the requirement for screw threads which are expensive to produce, and makes it possible for embodiments ofthe invention to be made simply and economically, largely in wood and utilising techniques which are readily available on a small scale such as to make it possible for school teachers themselves to produce the item. Of course, other embodiments may be made in other materials more suited to commercial production requirements, such as metal or plastics materials.

in a preferred embodiment ofthe invention the cam member is pivotable aboutthe said axis with respect to a counterposed abutment member between which and the cam memberthe workpiece is held in use of the device. Preferably the cam member has a convexly curved surface which is not centred on the said axis such that, upon turning of the cam member, a part of its surface is caused to approach the counterposed abutment member whereby to jam the workpiece between itself and the abutment member.

The form of the convexly curved cam surface may vary in dependence on particular requirements. In one embodiment the surface is an arcuate partcircular surface the centre of gravity ofwhich is offset laterally from the pivot axis ofthe cam member. In an alternative embodiment the curved surface is not circular or part-circular, but may be eliptical or even an irregularcurve having a spiral or other form.

In the preferred embodiment of the invention the counterposed abutment member is an upstanding ridge projecting from a base with respect to which the cam member is turnable. Alternatively, however, the abutment member may take a different form, in pa rticu lar i ncorporati ng fingers or studs, or other in- dividual projections against which a workpiece can be retained and clamped by operation ofthe cam member.

In the preferred embodiment of the invention the cam member is removably engageable with the base, and such a structure has the particularadvantage that it allows the pivot axis of the cam member to be moved, with respect to the base, over a range of different positions whereby to accommodate a wide range of different sizes of potential workpiece which can be accommodated by the device. For this pur posethecam member may be provided with apro- jecting pin whilstthe base may be provided with a plurality of holes into which the pin may beselec- tivelyintroduced in order to determine the interengagement between the cam memberandthe base.

As referred to above, the device of the present invention may be provided with its own fixed support or may be formed as a removable attachment to be mounted on afixed supportsuch as a bench ora table. In embodiments of the invention adapted to be removably attachable to a bench or table, the base may be provided with screw clamping means for attaching itto such fixed support.

In order to ensure a firm engagement between a workpiece and the cam member the latter may be provided with an elongate handle extending transversely of the axis of the said pin whereby to allow a significant leverage in effecting the clamping movement of the cam member by applying a turning force to the said handle.

Embodiments of the invention formed with a ridge as the counterposed abutment member projecting from the face may also incorporate one or a plurality of transverse slots in such ridge to allow the passage of, for example, a saw or other cutting tool in performing cutting operations on a workpiece clamped by the device.

Embodiments of the invention may be produced in which the convexly curved cam surface has a plurality of grooves or recesses therein extending generally parallel to the axis aboutwhich the cam member is turnable for the purpose of ensuring a more certain and secure contact between the cam member and a workpiece to be secured thereby, although for some purposes a smoothly contoured cam surface may be preferred.

According to another aspect, the present invention relates to a workpiece clamping device comprising a base portion fixed orfixableto a support, an up standing abutment and a clamping member having a convexly curved surface and an interengagement surface by which it is engageable against a cooperating part of the base portion, a convexlycurvedwork- piece-clamping surface being in the form of a cam having afirstportion spacedfurtherfrom an axisextending transversely of a line joining the upstanding abutment and the cooperating part of the base portion than a second portion thereof, about which axis the said clamping member is turnable with respectto the base portion whereby to clamp a workpiece positioned between itself and the upstanding abutment bythe effective approach ofthe said workpiece clamping surface and the upstanding abutment.

One embodiment of the present invention will now be more particularlydescribed, by way of example, with reference to the accompanying drawings, in which: Figure lisa partly expioded perspective view of the embodiment; Figure2 is a perspective view from the same angle of a part of the embodiment shown in an inverted position; and Aígure 3 is a plan view from aboveofthecompo- nentillustrated in Figure 2.

Referring nowto the drawings, the clamping device illustrated comprises a base 11 having an upstanding abutment ridge 12 at one end 13 thereof against which a workpiece can be positioned in use of the device. At the other end 14 of the base 11 there is a depending flange 15 from which there extends a further flange 16 generally parallel to and spaced from a plane ofthe base portion 11 to define a channel 17 which receives, for example, the edge of a table top or otherfixed support surface on which the device may be mounted for use.

Passingthrnughthefiange 16 is athreaded hole (not shown) in which is received a clamping screw 18 having a rounded end 19 for contacting the underside of a surface on which the device isfitted, and a handle20 bywhichtheclamping screw 18can be tightened to securethe device in place.

The upperface ofthe base portion 11 has a plura lity of holes 21 in a row extending orthogonallywith respect to the length of the upstanding abutment ridge 12. In other embodiments (notshown)the apertures 21 may be located in different positions aboutthe surface of the base 11, in particular being provided closerto the lateral edges thereof for spe cial purposes which wili be described hereinbelow.

Aclamping member generally indicated 22 comprises a cam 23 having a cam face 24 of arcuate convexly curved form constituting a part-cylindrical surface in which there are formed a plurality of parallel grooves 25 parallel to the axis of the cylindrical surface 24.

The cam body 23 has two parallel major faces 27, 28 lying in planes orthogonally of the axis of cylindrical curvature ofthe surface 24, and two approximately perpendicular side faces 29,30 spanning the'two major faces 27,28. Projecting from the side face 29 is an elongate lever 40 which constitutes an operating handle for the cam 22 and projecting from the majorface 28 is a pin 31 which can be engaged in any selected hole 21 to define a space between its convexly curved surface 24 and the adjacent face 32 of the upstanding abutment ridge 12.

In use of the device described hereinabove, the base 11 is first secured to a fixed surface such as a table top by introducing the edge of the table top into the channel 17 and turning the handle 20 to screwthe tip 19 ofthe clamping screw 18 into contact with the undersurface of the table top so as to fix the base of the device firmly in position. Following this a work piece on which working operations are to be performed is placed on the base 11 and moved into contact with the facing surface 32 of the upstanding abutment ridge 12. The pin 31 ofthe cam 22 isthen introduced into the appropriate hole 21 and the lever 40 turned in an anti-clockwise direction as viewed in Figures 1 and 3 to cause the cam face 24to approach the workpiece and press this against the face 32 of the ridge 12.By appropriate selection of the aperture 21 into which the pin 31 is introduced the forces applied between the workpiece and the cam surface pass through the pin 31 orto the side thereof remote from the lever 40 such that no resultant clockwiseturning moment is applied thereto and the cam is locked in position holding the workpiece firmly against the ridge 12. If the workpiece is highly incompressible and/or with a poor selection of the aperture 21 for receiving the pin 31, it may be necessary to retain the lever 40 in position by applying a force thereto,still retaining theworkpiece firmly in position whilst leaving both hands free to perform the working operationsthereon; alternatively one hand may be used toapplyaturning momenttothelever40whilstthe other perform the working operation. As a further alternative a suitable locking arrangement may include a rim or rig to be inserted into one ofthe holes 21 behind the lever 40 to hold it in the working position and prevent it from unlocking.

The cam shown may of course be replaced with one of opposite handedness so that right or left handed users can work in the most comfortable or convenient position oftheirchoice.

Claims (16)

1. Aworlcpiece clamping device, in which the clamping force is applied by turning a cam member about an axis extending transversely of the line of action oftheclampingforce.

2. Aworkpiece clamping device as claimed in Claim 1, in which the cam member if pivotable about the said axis with respect to a counterposed abutment member between which and the cam member the workpiece is held in use of the device.

3. A workpiece cla m pi ng device as claimed in Claim 1 or Claim 2, in which the cam member has a convexly curved surface which is not centred on the axis.

4. Aworkpiece clamping device as claimed in Claim 3, in which the convexly curved surface is an arcuate part-circularsurface.

5. Aworkpiece clamping device as claimed in Claim 3, in which the convexly curved surface is noncircularorpart-circular.

6. Aworkpiece clamping device as claimed in any of Claims 2 to 5, in which the counterposed abut ment member is an upstanding member projecting from a base with respect to which the cam member is turnable.

7. Aworkpiece clamping device as claimed in Claim 6, in which the cam member is removably engageable with the base.

8. Aworkpiececlamping device as claimed in Claim 6 or Claim 7, in which the cam member has a projecting pin and the base has a plurality of holes into which the pin is selectively introduceable.

9. Aworkpiece ciamping device as claimed in Claim 6, Claim 7 or Claim 8, in which the base is removabley attachable to a fixed support such as a bench,table orthe like.

10. Aworkpiececlamping deviceasclaimed in Claim 9, in which the base is provided with screw clamping means for attaching itto the said fixed support.

11. Aworkpiece clamping device as claimed in any preceding Claim, in which the cam member has an elongate handle extending transversely ofthe axis about which the said cam isturnable to allow the clamping movements of the said cam memberto be applied thereto.

12. Aworkpiece clamping device as claimed in any of Claims 2 to 11, in which the abutment member is in the form of a ridge having one or a plurality of transverse slots therein for the passage of a saw or other cutting tool.

13. Aworkpiece clamping device as claimed in any of Claims 3 to 12, in which the convexly curved cam surface has a plurality o grooves or recesses therein extending generality parallel to the axis about which the cam member isturnable.

14. Aworkpiececlamping device as claimed in any of Claims 6to 13, in which the base is a generally planar member having a transverse flange along one edge with a lip thereon defining a channel for receiv- ing the edge of a table or other fixed support.

15. Aworkpiececlamping device comprising a base portion fixed orfixable to a support, an upstanding abutment and a clamping member having a convexly curved surface and an interengagement surface by which it is engageable against a cooperating part of the base portion, the convexly curved workpiece-clamping surface being in the form of a cam having a first portion spaced further from an axis extending transversely of a line joining the upstanding abutment and the cooperating part of the base portion then a second portion thereof, about which axis the said clamping member is turnable with respect two the base portion whereby to clamp a workpiece positioned between itself and the upstanding abutment by the effective approach ofthe said workpiece clamping surface and the upstanding abutment.

16. Aworkpiece clamping device substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.