Tools having locking adjustments

[57] ABSTRACT

A tool, in particular a G-clamp, having a fixed clamping face on one end of an elongate body member and a further abutment face mounted on a slide member movable along the body member, the abutment face being movable relative to the slide member, and the slide member being capable of being slid along the body member to give quick-setting of the initial spacing between the clamping and abutment faces, subsequent pressure on said latter face effecting locking of the slide member on the support member.

Claims, 3 Drawing Figures

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U.S. Patent Oct. 28, 1975 Sheet 1 of 2 3,914,830

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U.S. Patent Oct. 28, 1975

Sheet 2 of 2

3,914,830

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3,914,830

TOOLS HAVING LOCKING ADJUSTMENTS

The present invention relates to tools having locking adjustment and, in particular to G-clamps although it may be applied to any tool where a force-applying slide member is to have an adjustable position on a substantially rigid support member before force is applied, it being necessary to lock the force-applying member in position relative to the support member when force is being applied. :

Most known G-clamps include a rigid support member provided with a fixed position clamping face and an adjustable member carrying an abutment face movable towards and away from the fixed clamping face. The adjustable abutment face is formed on one end of a threaded stem extending through a correspondingly threaded bore in the support member, the stem being provided at its other end with means for rotation thereof.

These known clamps have the disadvantage that adjustment of the clamp opening is provided for wholly by rotation of the threaded stem and such adjustment is a slow operation.

According to the present invention I provide a tool comprising a support member with rectangular crosssection having opposed first and second surfaces, a slide member mounted on the support member, the slide member having a body portion which embraces the support member and a trapping surface adjacent the first surface of the support member, a jamming member pivotally mounted on the slide member, resilient means urging the jamming member in one rotational direction against the second surface of the support member a stop on the slide member to limit the movement of the jamming member in the other rotational direction, and an abutment face for contacting a workpiece or item to which force is to be applied, this abutment face being mounted on the jamming member and being movable relatively to the slide member, the arrangement being such that pressure on the abutment face further urges the jamming member in the one rotational direction to cause increased pressure of said member against the second surface of the support member, said member thus being gripped between the jamming member and said trapping surface to lock the slide member to the support member, the jamming member being releasable from the support member by pivoting movement of said jamming member and abutment face in the other rotational direction whereby the slide member is slidable in either direction relative to the support member.

Preferably the jamming member includes an arcuate cam surface adapted to press against the second surface of the support member, the abutment face being to the side Of the pivot remote from said cam surface, whereby pressure on said abutment face rotates the jamming member in the one direction to bring an increased-diameter portion of said cam surface into contact with the second surface of the support member to effect said locking.

Conveniently the abutment face is formed at one end of an externally threaded shaft mounted in a threaded bore in the jamming member.

The resilient means may comprise a coil spring reacting between the slide member and a region of the jamming member to the same side of the pivot as the abutment surface. Said spring may be sufficiently light to allow the slide member to be pushed by hand along the support member in a direction opposed to that of the force to be applied to the abutment face. The threaded shaft however constitutes a convenient lever for pivoting the jamming member in the other rotational direction about its pivot against the bias of the spring thereby to permit ready sliding movement of the slide member in either direction relative to the support member.

Thus the invention provides a tool, for example a clamping tool, permitting quick-setting of the clamping opening during initial engagement of a workpiece or item to be gripped, and which is such that the greater the clamping pressure on the item the greater is the locking effect of the mechanism.

An embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings, wherein:

FIG. 1 is a side view of part of a G-clamp having a slidable force-applying member adjustably mounted on a support member in accordance with this invention;

FIG. 2 is a vertical section along the line II—II of FIG. 1, and

FIG. 3 is a vertical section along the line III—III of FIG. 2.

Referring to the drawings a G-clamp 1 has a substantially rigid support member in the form of a metal rod 2 of rectangular cross-section having an abutment surface 2α. A head, member 3 is fixed to one end of the rod 2, conveniently by means of bolts or spring dowels. A slide member 4 is mounted on the rod 2 and is slidable along the rod so that a clamping head 5 can be brought towards the head member 3 to grip an item between them.

The slide member 4 has a generally cylindrical portion 6 of rectangular cross-section that engages the rod 2. In one embodiment of the invention a pair of pins or bolts (not shown) are fixed at the end of the rod 2 opposite the head member 3 and project from the sides of the rod to prevent the member 4 being slid off the rod, the pins or bolts engaging recesses 20 in the member 4.

A pair of lugs 7, integrally formed with the portion 6, provide bearing support for a pivot 8 carrying a jamming member 9 having an internally threaded bore 10. An externally threaded shaft 11 screws into the bore 10 and carries the clamping head 5 at one of its ends. The clamping head is mounted on the shaft 11 by means of a ball-joint 12 so that, over a large range of angular positions of the bore 10 about the pivot 8, the clamping head 5 can grip an item by contact over its abutment face 13. A transverse handle 14 is provided in a bore 15 in the end of the shaft 11 remote from the clamping head 5.

A coil spring 16 is provided in a blind recess 17 in the member 9 and bears on a face 18 of the member 4 to exert a pivoting moment biassing the jamming member 9 onto the rod 2.

The jamming member 9 contacts the abutment surface 2a of the rod 2 with a hardened, curved portion 21 whose radius relative to the pivot 8 increases anticlockwise in the plane of its pivoting movement so that an increasing clockwise moment exerted on the jamming member 9 provides an increasing pressure between the jamming member and the rod 2. The curved portion 21 is serrated, the transverse section through each tooth being slightly V-shaped (for example of the order of 3° from the horizontal) as seen in FIG. 2 thus ensuring

3,914,830 that the jamming member 9 engages with the central region of the associated surface 2a of the rod 2 thereby decreasing the possibility of deformation of said surface 2a of the rod 2 that full face contact of the teeth with the rod might cause. A trapping surface 22 of the portion 6 lies adjacent the lower surface of the rod 2 and co-acts with the jamming member to grip the rod.

The strength of the spring 16 may be such as to permit, when the G-clamp is to grip an item between the head member 3 and the clamping head 5, a “quick-set” movement of the slide member 4 merely by pushing it to slide the rod 2 towards the head member 3, the jamming member pivoting slightly against the relatively weak bias of the spring as the sliding occurs. The spring 16 may be such as to exert a relatively large clockwise moment on the jamming member to make simple pushing of the member 4 along the rod towards the head member 3 difficult. The jamming member 9 can then be disengaged from the rod 2 by applying an anticlockwise moment to the jamming member about its pivot 8 using the shaft 11 as a lever, the top end of the face 18 of the slide member acting as a stop to limit the counterclockwise movement of the jamming member; this position of the jamming member 19 permits ready sliding movement of the member 4 along the rod 2. Similarly, whatever strength spring 16 is used, said disengagement using the shaft 11 as a lever permits sliding movement of the clamping head 5 away from the fixed head member 3. It is preferred that the spring 16 is at least strong enough to hold the member 4 in position on the rod against the weight of the member 4.

Subsequent to the “quick-set” movement of the member 4, the item can be gripped by rotating the shaft 11 using the handle 14 so that the clamping head is translated towards the head member 3. The reaction to the gripping force of the clamping head 5 produces a clockwise moment on the jamming member 9, locking the member 4 in position on the rod. The greater the gripping force exerted by the clamping head the greater is the normal reaction of the jamming member on the rod giving a greater frictional force opposing movement of the member 4 relative to the rod 2.

In an alternative embodiment of the invention, the slide member 4 and its associated components can be slid off the end of the rod 2. In order to prevent possible loss of the spring 16 from this unit when off the tool, a stop member is formed on the jamming member adjacent the lower right hand region thereof, as viewed in FIGS. 1 and 3, and adapted to abut the adjacent sidewall of the member 4 thereby to prevent clockwise rotation of the jamming member 9 into the slide member 4. The spring 16 cannot then completely disengage with the surface 18 of the member 4 and cannot therefore fall out of its recess 17. Clearly the location of the stop member is such as not to come into effect during normal operation of the tool. Such removability enables the member 4 to be turned through 180° on the rod 2 and the tool to be used to provide a spacing or stretching action.

It is to be understood that while the rod 2 has been described as being of rectangular cross-section it could be of round or any other cross-section which provides the rod with sufficient rigidity.

It has been found that the G-clamp described above, which can be modified in various ways, is a versatile and reliable tool which can be used to give quick-set movement and high gripping pressures.