GB1580905A

GB1580905A - Clamps

Info

Publication number: GB1580905A
Application number: GB4201176A
Authority: GB
Original assignee: HMC Brauer Ltd
Current assignee: HMC Brauer Ltd
Priority date: 1976-10-08
Filing date: 1976-10-08
Publication date: 1980-12-10
Also published as: FR2366915A1; DE7730801U1; FR2366915B3

Description

(54) CLAMPS (71) We, HMC-BRAUER LIMITED, a British Company of 27 Hill Street, London W1X 8AS, do hereby declare the invention for which we pray that a Patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to clamps such as are used in engineering and woodwork and are often known as C-clamps, of the kind com prising a bar carrying either a fixed jaw at one end and an adjustable jaw which is capable of being moved to any position along the bar, or a bar with two jaws, both mounted for move ment along it; the movable jaw is carried on an arm that extends laterally from the bar and the arm has an aperture or slot by which the arm embraces the bar, the slot having a pair of off set abutments which engage opposite edges of the bar to cause the arm to become jammed on the bar when a load is applied by the work piece to the associated jaw in a direction parallel to the length of the bar. This provides a coarse adjustment. The fine adjustment, serving to apply the clamping load to the workpiece, is provided either by mounting the jaw on the arm through the medium of a screw that extends parallel to the length of the bar or by making one of the jamming abutments movable with respect to the arm, by mounting it on a screw or by making it in the form of a cam. This kind of clamp is referred to in the following as a clamp of the kind set forth.

One edge of the bar may be serrated to pro vide notches ensuring positive location of the one abutment for the coarse setting, rather than relying solely on friction.

The aim of the present invention is to pro vide further detailed improvements in a clamp of the kind set forth. According to the inven tion in a clamp of the kind set forth, in which the adjustable arm is formed from two stamp ings riveted together with a gap between them to define the aperture through which the bar passes and one of the rivets holding the stamp ings together forms the first abutment and the clamp jaw is secured directly to the free end of the arm in a manner allowing it to tilt and the second abutment is formed by the tip of a screw.

The rivet forming the abutment may serve to locate a spacing bush that lies between the stampings and acts as the abutment. Alternatively the rivet may have an enlarged central portion lying between the stampings to form the abutment. Where the fine adjustment is provided by mounting the jaw on the arm through the medium of a screw, the second abutment may be formed in the same way as the first. However, in a preferred version the jaw is riveted directly to the free end of the arm (though in a manner allowing it to tilt) and the second abutment is formed by a screw.

The bar is preferably formed from rolled metal strip, suitably steel. The mounting for the fixed jaw (where present) may be formed by bending round a portion of one end of the strip in the plane of the strip. Alternatively two movable jaws may be mounted on adjustable arms mounted movably on the strip.

According to a further preferred feature of the invention this screw is received in a threaded block that fits loosely into aligned apertures in the two stampings. For example the block is rectangular or of other non-circular shape and is located solely by the presence of the screw passing through it.

Further features of the invention will be revealed by a study of the following detailed description of a preferred embodiment, and some modifications, with reference to the accompanying drawings, in which: Figure 1 is a view of the clamp in its fully closed position; Figure 2 is an isometric view of the extrusion from which the jaws of the clamp of Figure 1 are made; Figures 3 and 4 show respectively the two jaws made from the extrusion of Figure 2, looking in a direction which lies in the plane of the drawing of Figure 1; Figure 5 is a view of part of a clamp with a modified form of spring; Figure 6 is an isometric view of the spring used in the clamp of Figure 5; Figure 7 is a view of part of a clamp with a third form of spring; Figure 8 is an isometric view of the spring used in the clamp of Figure 7; Figure 9 is a view of part of a damp with a fourth form of spring;; Figure 10 is an isometric view of the spring used in the clamp of Figure 7; Referring first to Figure 1, the clamp comprises basically a bar 1 of mild steel strip, of which one end is bent around in the plane of the major axis of the bar to form a fixed arm 2.

The other end of the bar (not shown) is of any suitable length, according to the work-holding capacity required. Slidably mounted on the bar 1 is a movable arm formed by two flat stampings 3 from metal strip. A rivet 4 secures the stampings together near their central regions and has, between the stampings, an enlarged central portion which has the dual function of spacing the stampings apart and of forming a first abutment for engaging one edge of the bar, this edge being provided with a row of serrations 5, in any one of which the rivet can rest. The rivet 4 may alternatively comprise a cylindrical member and a spacing bush may be located on a central portion of the rivet lying between the stampings, the bush serving to space them apart and form the first abutment.

A second abutment, engaging the opposite edge of the bar 1 (this edge having no serrations) is formed by the tip of a screw 6 which carries a tommy bar 7 and is in screw-threaded engagement with a rectangular block 8 through which it passes. This block is received in square openings 9 formed in the stampings 3. The presence of the screw 6 holds the block loosely in place between the stampings.

Two further rivets 10 form locating means for a leaf spring 11 which bears against the smooth edge of the bar 1 and urges the bar clockwise about the rivet 4 (as viewed in Figure 1) to keep the tip of the screw 6 lightly in contact with the bar. It will be noted that the two abutments formed by the rivet 4 and the top of the screw are offset in relation to the length of the bar 1, so that a clockwise couple exerted on the movable arm will cause it to jam on the bar 1.

The free end of the movable arm carries a jaw 12 having a lug 13 which enters between the ends of the stampings 3 and is secured by a rivet 14 in a manner that leaves the jaw free to rock through a limited arc to align itself with the surface of a workpiece. Arcuate cheeks 15 on the stampings 3 ensure that the load on the jaw 12 is transmitted directly to the arm and not in shear through the rivet 14.

The fixed arm 2 carries a similar jaw 16 but with spaced lugs 17 to embrace the tip of the arm; the jaw is held by a rivet 18.

Both jaws 12 and 16 are produced by cutting off portions of an extrusion, for example of light alloy, of the section shown in Figure 2.

For the jaw 16 a slot is milled in the cut-off portion, as shown in Figure 3, to define the two spaced lugs 17, whilst for the jaw 12 two side portions are cut away, as shown in Figure 4, to leave the single lug 13. This forms a particularly neat and economical way of forming the two kings of jaw without resorting to casting, forging or extensive machining.

Figures 5 and 6 show a modified mounting arrangement for the spring, which, in place of the leaf spring 11 of Figure 1, has ears shown at 11' engaging in spaced holes in the two stampings 3, so that the need for the rivets 10 is eliminated.

Figures 7 and 8 show a third way of mounting the spring, which is shown in Figure 8 as having two ears 11". These are received in the square openings 9 already provided for the block 8, and the presence of the block holds the spring in place.

Figures 9 and 10 show a fourth way of mounting the spring which is similar to that shown in Figures 7 and 8, the spring in this embodiment also having two ears 11" which are received in the openings 9 already provided for the block 8, the presence of the block holding the spring in place. However the spring is mounted in the opposite direction to that of Figure 7, and it is formed with an inwardly curved tongue 19 at its free end which faces and bears against the smooth edge of the bar 1.

Instead of having one fixed arm and one moving arm, the clamp could have a straight bar 1 with the end portion 2 omitted, and this bar could carry two movable arms, both identical with the one described. They could moreover be put on the bar back to back instead of facing each other, allowing the clamp to be used to urge any two surfaces apart instead of together.

WHAT WE CLAIM IS: 1. A clamp of the kind set forth, in which the adjustable arm is formed from two stampings riveted together with a gap between them to define the aperture through which the bar passes and one of the rivets holding the stampings together forms the first abutment and the clamp jaw is secured directly to the free end of the arm in a manner allowing it to tilt and the second abutment is formed by the tip of a screw.

2. A clamp according to Claim 1 in which the rivet forming the abutment has an enlarged central portion lying between the stampings to form the abutment.

3. A clamp according to Claim 1 in which the rivet forming the abutment serves to locate a spacing bush which lies between the stampings and acts as the abutment.

4. A clamp according to Claim 1 in which the screw is received in a threaded block which fits loosely into aligned apertures in the two stampings.

5. A clamp according to Claim 4 in which the block is of non-circular shape and is located solely by the presence of the screw passing through it.

6. A clamp according to any preceding Claim, in which the bar is formed from rolled

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. used in the clamp of Figure 7; Figure 9 is a view of part of a damp with a fourth form of spring; Figure 10 is an isometric view of the spring used in the clamp of Figure 7; Referring first to Figure 1, the clamp comprises basically a bar 1 of mild steel strip, of which one end is bent around in the plane of the major axis of the bar to form a fixed arm 2. The other end of the bar (not shown) is of any suitable length, according to the work-holding capacity required. Slidably mounted on the bar 1 is a movable arm formed by two flat stampings 3 from metal strip. A rivet 4 secures the stampings together near their central regions and has, between the stampings, an enlarged central portion which has the dual function of spacing the stampings apart and of forming a first abutment for engaging one edge of the bar, this edge being provided with a row of serrations 5, in any one of which the rivet can rest. The rivet 4 may alternatively comprise a cylindrical member and a spacing bush may be located on a central portion of the rivet lying between the stampings, the bush serving to space them apart and form the first abutment. A second abutment, engaging the opposite edge of the bar 1 (this edge having no serrations) is formed by the tip of a screw 6 which carries a tommy bar 7 and is in screw-threaded engagement with a rectangular block 8 through which it passes. This block is received in square openings 9 formed in the stampings 3. The presence of the screw 6 holds the block loosely in place between the stampings. Two further rivets 10 form locating means for a leaf spring 11 which bears against the smooth edge of the bar 1 and urges the bar clockwise about the rivet 4 (as viewed in Figure

1) to keep the tip of the screw 6 lightly in contact with the bar. It will be noted that the two abutments formed by the rivet 4 and the top of the screw are offset in relation to the length of the bar 1, so that a clockwise couple exerted on the movable arm will cause it to jam on the bar 1.

metal strip.

7. A clamp according to Claim 6, in which the mounting for the fixed jaw is formed by bending round a portion of one end of the strip in the plane of the strip.

8. A clamp according to Claim 6 in which the bar carries a second movable jaw mounted on a second movable arm.

9. A clamp according to any of Claims 6 to 8, in which the bar and the adjustable arm are formed from steel strip.

10. A clamp according to any of Claims 1 to 9, in which the jaws are formed by cutting blanks from an extruded section of T-section and then machining them approximately, the fixed jaw being formed by machining a slot through the stem of the T to define a pair of spaced lugs, the free end of the fixed arm formed by the bent-round end of the bar being received in the slot and a rivet through the lugs and through this end securing the fixed jaw in place, and the movable jaw being fonned by machining away the sides of the stem of the T to define a single lug that is received between the two stampings of the movable arm.

11. A clamp according to any preceding Claim including spring means acting between the movable arm and the bar in a sense to tilt the arm in a direction to cause the pair of abutments to engage the bar.

12. A clamp according to Claim 11, in which the spring means comprises a leaf spring mounted on the movable arm and bearing against one edge of the bar.

13. A clamp according to Claim 12, in which the spring is in the form of a U-shaped leaf spring located between the stampings and secured in place by one limb of the U passing round rivets that extend through the stampings, whilst the other limb is free and bears against the bar.

14. A clamp according to Claim 10, in which the leaf spring includes laterally projecting ears which locate the spring in the movable arm.

15. A clamp according to Claim 4 and Claim 14, in which the lateral ears engage in the apertures provided for the screw-receiving block and the presence of the block holds the spring in place.

16. A clamp according to Claim 15, in which the spring has an inwardly curved tongue at its free end remote from the ears which is adapted to face and bear against the bar.

17. A clamp according to Claim 15, in which the spaced lateral ears are provided on the spring and engage in separate holes provided in the stampings.

18. A clamp according to any preceding Claim, in which the jaws are extended laterally towards the bar and have apertures or slots by which the bar passes through them.

19. A clamp substantially as herein described with reference to and as illustrated in Figures 1 to 4 of the accompanying drawings.

20. A clamp substantially as herein described with reference to and as illustrated in Figures 5 and 6 of the accompanying drawings.

21. A clamp substantially as herein described with reference to and as illustrated in Figures 7 and 8 of the accompanying drawings.

22. A clamp substantially as herein described with reference to and as illustrated in Figures 9 and 10 of the accompanying drawings.