WO1992009814A1

WO1992009814A1 - A clamp for attachment to an elongate member such as an i-section beam

Info

Publication number: WO1992009814A1
Application number: PCT/GB1991/002056
Authority: WO
Inventors: Keith Riley
Original assignee: Riley (Lifting Equipment) Limited
Priority date: 1990-11-22
Filing date: 1991-11-20
Publication date: 1992-06-11
Also published as: GB9025419D0; AU8921791A

Abstract

A clamp is provided for attachment to an elongate member such as an I-section beam (10). The clamp comprises a pair of jaws (12 and 13) which are relatively movable towards one another to embrace the elongate member and clamp the elongate members between the jaws with a given pressure, the jaws being such that if a force is applied to the clamp tending to move the jaws along the elongate member, the said given pressure increases.

Description

A CLAMP FOR ATTACHMENT TO AN ELONGATE MEMBER SUCH AS AN I-SECTION BEAM

*

The invention relates to clamps, and particularly to clamps arranged to clamp on to elongate members.

One known clamp, designed for clamping on to an I-section beam, is disclosed in GB Patent No. 1567079. Since such a clamp engages around the flanges of the beam, the clamp is ideally suited to withstand heavy loads, when suspended from the clamp.

10

Problems can arise however, if a load is applied to the clamp in a direction tending to pull the clamp along the length of the beam. When the clamp is pulled in such a direction, the forces resisting movement of the clamp in that direction are dependent upon the clamping force produced by the

15 tightening of the clamp on to the beam, and on the co-efficient of friction. The clamping force produced by the tightening of the clamp is not consistent. The tightening is usually produced by bolts or other threaded members and the force produced will vary if the threads are dry or dirty, or both, even assuming that a torque wrench is used to tighten the members. Furthermore

20 the co-efficient of friction between the clamp and the beam can vary substantially depending on whether the beam is wet, dry or painted.

It is therefore questionable whether known clamps have the required factor of safety, which can sometimes be fives times the safe working load of 25 the clamp, if the load is applied in a direction tending to move the clamp along the length of the beam. - 2 -

A further point concerns the well known fact that the static co-efficient of friction is considerably higher than the sliding co-efficient of friction. Thus any initial slight movement as a result of the clamp being subjected to a sudden load could result in a rapid breakaway along the length of the beam.

5

Because of these factors, known clamps are potentially dangerous if loaded heavily in a direction tending to move the clamp along the length of the beam.

10 Accordingly the invention provides a clamp for attachment to an elongate member such as an I-section beam, comprising a pair of jaws relatively movable towards one another to embrace the elongate member and clamp the elongate member between the jaws with a given pressure, the jaws being such that if a force is applied to the clamp tending to move the jaws

15 along the elongate member, the said given pressure increases.

Preferably at least one of the jaws comprises a rotatably mounted first cam member, any tendency for the jaws to move along the elongate member causing the cam member to rotate in a direction which reduces the distance 20 between the jaws.

The other jaw may comprise a second rotatably mounted cam member.

The said first cam member may have a curved abutment face to engage 25 the elongate member.

The said second cam member may have a flat abutment face to engage the elongate member. There may be a pair of carriers, one for each cam member, each carrier having a groove to receive the flange of an I-section beam, the said cam members being respectively mounted in the bases of the said grooves.

The said carriers may be mounted for movement towards and away from one another by a screwthreaded means.

The screwthreaded means may comprise a threaded rod and a tommy bar.

There may be a load attachment device, for example a shackle, connected to the carriers.

Preferably, the load attachment device is pivotally connected to the carriers, for movement about an axis which extends in the direction of clamping movement, such that the load attachment device can align itself with the direction of load, when the direction of loading tends to be along the length of the elongate member.

By way of example, specific embodiments of the invention will now be described, with reference to the accompanying drawings, in which :-

Figure 1 is a part sectional view of an embodiment of clamp according to the invention, looking along the length of an I-section beam to which the clamp is to be attached; Figure 2 is a view in the direction of arrow II of Figure 1, showing the attitude that will be adopted by the clamp when a load is applied to the clamp in a direction having a component extending along the length of the beam;

Figure 3 is a cross-section on line III-III of Figure 1;

Figure 4 is a view similar to Figure 1, but showing an alternative embodiment of clamp according to the invention;

Figure 5 is a view looking in the direction of arrow V of Figure 4;

Figure 6 is a sectional view on line VI-VI of Figure 4, to en enlarged scale:

Figure 7 is a plan view of an alternative embodiment of jaw:

Figure 8 is a view in the direction of arrow VTII of Figure 7; and

Figure 9 is a view in the direction of arrow IX of Figure 7.

The clamp shown in the Figures is intended to clamp on to an I-section beam 10, having a pair of flanges 11. In order to secure the clamp to the beam, the clamp has a pair of jaws 12 and 13, each in the form of a cam.

Each cam 12, 13, is mounted for pivotal movement about a vertical pivot pin 14, each pivot pin 14 forming part of an associated carrier 15. The carriers 15 are movable towards and away from one another by means of a screwthreaded arrangement. Each carrier has a smooth bore 16

(see Figure 1) therethrough, and a screwthreaded bar 17 passes through each bore 16. At one end of the bar 17 there is a fixed nut 18 and at the other end there is a retainable nut 19 to which a tommy bar 20 is attached.

The cam 13 has a substantially flat abutment face 21 with serrations thereon. The cam 12 has a curved abutment face 22, also with serrations thereon. Each carrier 15 has a groove 23 therein and the cams 12 and 13 are positioned so that their abutment faces form the bases of these grooves, as best shown in Figure 1.

Freely rotatable about the rod 17, within each carrier 15, there is a suspension lug 24. To each lug there is attached, by means of a bolt 25, a pair of side plates 26.

The two pairs of side plates are interconnected by a further bolt 27 which passes first through one arm of a shackle 28, then through one of the first pair of side plates 26, then through a washer 29 (see Figure 2) then through a side plate of the second pair, then through a spacer 30, then through the other side plate of the second pair, then through a further washer 31, then through the other side plate of the first pair, then through the second arm of the shackle 28, and finally through a nut 32.

In order to attach the clamp to the beam 10, the nut 19 is unscrewed by means of the tommy bar 20 by an amount sufficient to enable the carriers 15 to be separated sufficiently to pass them round the flanges 11 of the beam. The carriers 15 are then moved towards one another until the flanges 11 of the beam engage in the grooves 23 and the tommy bar is rotated in the opposite direction to clamp the jaws against the beam. Because the cams 12 and 13 are rotatable, they centre themselves and grip the beam as shown in Figure 3.

In this position, the clamp is ideally suited to support vertical loads which may be suspended from the shackle 28. The shackle is also suited to support loads which are inclined to the vertical, but are still perpendicular to the longitudinal axis of the beam 10. Because the shackle 28 can rotate about the bolt 27, the shackle can align itself with loads in this direction, i.e. in the direction of arrow A of Figure 1, and because of the way that the carriers embrace the flanges 11 of the beam, the clamp does not rely purely on frictional forces to resist the load.

If however a load is applied in a direction which has a component extending along the length of the beam, for example in the direction of arrow B of Figure 2, the clamp does have to rely purely on frictional forces. This is where the clamp forming the subject of this embodiment is superior to prior art clamps.

A load in the direction of arrow B will, as already stated, tend to move the clamp along the length of the beam. However because the beam is gripped by the abutment faces and the cams 12 and 13, any tendency for the clamp to move relative to the beam along the length of the beam will cause the cams 12 and 13 to rotate about their pivot pins 14. This will in turn tend to reduce the distance between the two cams and substantially increase the clamping pressure. This makes the clamp very effective in resisting loads in a direction tending to move the clamp along the length of the beam. Because the cams 12 and 13 are symmetrically arranged, the clamp is equally suitable to resist loads in either direction along the length of the beam.

Because the lugs 24 are freely rotatable about the rod 17, the side plates 26, and hence the shackle 28, can align themselves readily with the direction of pull of the load, as best shown in Figure 2.

The embodiment shown in Figures 4 to 6 has a pair of substantial jaw carriers 41 and 42, pivotally connected together at 43. The carriers 41 and 42 can be moved towards and away from one another by a screwthreaded rod 41 and a tommy bar 45. The screwthreaded rod 44 engages in internally threaded knuckle joints 46 and 47 pivotally connected between the plates 48 which form the carriers 41 and 42.

Each carrier 41 and 42 has a part circular cut-out 49 and pivotally mounted in this cut-out is a jaw member 50. Each jaw member has a part circular portion 51 and a pair of rear lugs 52.

In each jaw member there is a cam member 53, mounted for pivotal movement about a vertical pivot bolt 54. Each pivot bolt 54 passes through the lugs 52.

In use, the webs of an I-section beam will extend into slots 55 in the jaw members 51 to engage against the cam members 53 so that the clamp operates in a similar manner to the clamp shown in Figure 1. Because the jaw members 51 can swivel in the jaw carriers 41 and 42, the slots 55 can be aligned with the webs of the I-section beam, regardless of the angle between the carriers 41 and 42.

To maintain the slots 53 facing one another, so that a user of the clamp does not have to manually position the slots 55, each pivot bolt 54 engages with a bracket 56 which is connected to a collar 57 which slides on the threaded bar 44. Thus the slots 55 have a constant orientation with respect to the horizontal threaded bar 44.

A swivel member 57 extends downwardly from the pivot bolt 43, and a shackle 58 is connected to the swivel member 57 by a horizontal pivot bolt 59. This enables the shackle 55 to take up a variety of orientations. For example, the shackle 58 can swivel through 360° about a vertical axis, and that any point in this rotation, it can be pivoted upwardly about the bolt 59. Figure 4 shows one position of the shackle in solid lines and three other positions in dotted lines.

To maintain the cam members 53 in a central, datum position, to facilitate their proper engagement with the I-section beam, without initial manual adjustment, leaf springs 60 are provided as shown in Figure 6 to gently hold the cam members 53 in the position shown in Figure 6.

If an I-section beam tends to slip out of position owing to side loading, the cam members 53 pivot slightly about pivot bolt 64 to increase the grip, and the springs 60 are such that they can accommodate this slight pivoting movement. Once the clamp has been removed from a beam, the cam members 53 will return to the datum position shown, ready to grip another beam.

With the jaw members shown in Figures 4 to 6, there can be a risk of the beam damaging the edges of the jaw member slightly, during the slight rocking movement of the beam which can take place if it slips slightly.

With the alternative jaw member shown in Figure 7 to 9, the risk of damage to the jaw member is reduced.

Each jaw member still has a circular portion 51, and rear lugs 52, but the slots 55 have radiused ends 61.

The web of a beam has been drawn in diagrammatically at 62 in Figure 8 and it will be seen that a certain amount of tilting can be accommodated, point loading occurring at 63 and 64.

As can also be seen from Figure 8, the jaw has a slot 65 therein, in which the associated cam member is mounted.

The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiments). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one. or any novel combination, of the steps of any method or process so disclosed.

Claims

1. A clamp for attachment to an elongate member such as an I-section beam (10), comprising a pair of jaws (12, 13) relatively movable towards one another to embrace the elongate member and clamp the elongate member between the jaws with a given pressure, the jaws being such that if a force is applied to the clamp tending to move the jaws along the elongate member, the said given pressure increases.

2. A clamp as claimed in Claim 1. in which at least one of the jaws (12. 13) comprises a rotatably mounted first cam member (12), any tendency for the jaws to move along the elongate member causing the cam member to rotate in a direction which reduces the distance between the jaws.

3. A clamp as claimed in Claim 2, in which the other jaw comprises a second rotatably mounted cam member.

4. A clamp as claimed in Claim 3. in which the first cam member has a curved abutment face to engage the elongate member.

5. A clamp as claimed in Claim 3 or Claim 4, in which the second cam

• _* member has a flat abutment face to engage the elongate member.

6. A clamp as claimed in any one of Claims 3 to 5, in which there are a pair of carriers (15), one for each cam member, each carrier having a groove

(23) to receive the flange of an I-section beam, the said cam members being respectively mounted in the bases of the said grooves.

7. A clamp as claimed in Claim 6, in which the carriers are mounted for movement towards and away from one another by a screwthreaded means.

8. A clamp as claimed in Claim 7, in which the screwthreaded means comprises a threaded rod and a tommy bar.

9. A clamp as claimed in any one of Claims 6 to 8, in which there is a load attachment (28) device connected to the carriers (15).

10. A clamp as claimed in Claim 9. in which the load attachment device (28) is pivotally connected to the carriers (15), for movement about an axis which extends in the direction of clamping movement, such that the load attachment device can align itself with the direction of load, when the direction of loading tends to be along the length of the elongate member.

11. A clamp constructed and arranged substantially as herein described with reference to Figures 1 to 3, or Figures 4 to 6. or Figures 7 to 9. of the accompanying drawings.