GB2338261A

GB2338261A - Clamp for a curved bar

Info

Publication number: GB2338261A
Application number: GB9812244A
Authority: GB
Inventors: Maximillian Edward Burgess
Original assignee: Individual
Current assignee: Individual
Priority date: 1998-06-08
Filing date: 1998-06-08
Publication date: 1999-12-15
Anticipated expiration: 2018-06-08
Also published as: GB2338261B; GB9812244D0

Abstract

A clamping device for a curved bar or rod, eg a caravan tow bar, comprises a pair of clamping members 2, 4 and a series of clamping wedges 16 between them. The members are drawn together by bolts, so as to compress the wedges against the curved region of the bar at three locations along its length. A side arm 6 enables the clamp to be attached to a fitting 20, which in turn can be attached eg to a cycle rack.

Description

2338261 1 CLAMPING DEVICE This invention provides a clamping device for

attachment to a curved rod or bar such as the neck of a tow bar, and in particular a tow bar of the Viswannecked" variety.

It is known to attach fittings to the shaft of a tow bar by means of a clamping arrangement. Such fittings can be, for example, the base of a cycle rack or ski rack, or a stabiliser for a caravan or trailer. Clamping arrangements of the aforesaid type typically comprise a pair of clamping halves connected by a pair of tightening bolts disposed either side of the tow bar. Such an arrangement functions adequately when the tow bar is of generally uniform width along its length, but it has been found that such conventional clamping arrangements are less effective when the tow bar is of the tapering or "swannecked" variety. In particular, with swan-necked tow bars, it has been found that conventional clamping devices do not grip adequately and have a tendency to become dislodged either axially or by swivelling around the tow bar.

An object of the present invention is to provide an improved clamping device which is able to grip tow bars of the swan-necked variety in a much more secure manner. It has now been found that this object can be met by providing a clamping device which grips the tow bar at three axially spaced apart locations, one location on one side of the tow bar and two locations on the opposite side of the bar, in a generally triangular configuration. Thus, the clamping device can be arranged to grip the tow bar on one side at the inner 1 11 2 radius of the curved neck, and on the other side at spaced apart locations either side of the point of maximum curvature on the outer radius of the tow bar.

Accordingly, in a first aspect, the invention provides a clamping device for clamping to a curved region of a bar or.rod (such as a tow bar), the clamping device comprising a pair of clamping members, one or both of the clamping members having connecting means enabling the attachment thereto of another object; a plurality of gripping members disposed between the clamping members; and means for drawing the clamping members together so as to compress the gripping members against the curved region of the bar or rod; wherein the number of gripping members is such as to enable the curved region of the bar or rod to be gripped at three or more clamping locations along its length.

The clamping members typically are in the form of a pair of clamping plates which may be, for example, of generally triangular configuration.

The means for drawing the clamping members together preferably are bolts extending between the plates. Such bolts can be, for example, received within apertures in the plates.

It is preferred that the gripping members are rotatably mounted with respect to the plates since this enables the clamping device to accommodate tow bars having a range of different curvatures. Where the means for drawing the clamping members together are bolts extending between the plates, the gripping members are preferably rotatably mounted on the bolts.

in general, a pair of gripping members is provided at each clamping location, and each gripping member preferably has an inclined gripping surface for gripping the bar or rod. The angles of inclination of the gripping members c : ' ' r ' 3 are typically opposed. Although, the gripping members can have gripping faces which are curved or hollow so as to conform to the surface of the tow bar, it has been found that a better grip is obtained when the inclined gripping surface is substantially planar. Whether planar or non- planar, the gripping faces of the gripping members can be provided with grip-enhancing means. Such gripenhancing means can take the form of regular or irregular roughening of the surface or a pattern, regular or irregular of one or more ridges, protrusions (e.g. teeth), indentations or other surface configurations which give rise to improved grip. For example, the gripping elements can have a knurled surface or an array of elongate ridges (preferably sharp-edged ridges) for biting into the surface of the bar or rod.

The clamping locations are most preferably arranged in a triangular array, for example in the form of an equilateral or non-equilateral triangle.

The connecting means for connecting the clamp to another device can take many different forms, but in one embodiment, can be for example, a side arm extending outwardly from one of the clamping members. The side arm may have one or more apertures or protrusions to enable the attachment thereto of another object. For example, the side arm can be of tubular construction, a central bore of the tube being threaded to receive a correspondingly threaded bolt. It will be appreciated however that the precise form of the connecting means is not central to the invention.

In a particularly preferred embodiment, the invention provides a clamping device for clamping to a curved bar or rod, the clamping device comprising a pair of clamping plates, one or both of the clamping plates having connecting means (such as a side arm) enabling the attachment thereto of another object; three pairs of gripping members disposed between the clamping members; and clamping bolts for drawing the clamping plates together so as to compress the 1 - 4 gripping members against the curved bar or rod; the clamping bolts being arranged in a triangular array and each clamping bolt having one of the pairs of gripping members rotatably mounted thereon.

The invention will now be illustrated, but.not limited, by reference to the embodiment shown in the accompanying drawings, of which:

Figure 1 is an exploded view of a clamp according to one embodiment of the invention; Figure 2 is an isometric view of one of the clamping plates of the embodiment of Figure 1; Figure 3 is a view from one side of the clamp of Figures 1 and 2 connected to a tow bar; and Figure 4 is a sectional elevation along line 1-1 in Figure 3.

Referring to the drawings, a clamp according to one embodiment of the invention comprises a pair of triangular clamping plates 2 and 4 formed from mild steel. One of the plates 2 has a tubular side arm 6 welded thereto. Tubular side arm 6, also formed of mild steel, has a threaded bore 8 enabling the clamp to be attached to a range of fittings. Such fittings can include for example a base support for a cycle carrier as shown in Figure 1.

Apertures 10 are provided at the three corners of the triangular clamping plates for receiving bolts 12 for connecting the two plates 2 and 4 together. Lock nuts 14 are attached to each of the bolts.

Rotatably mounted on each bolt, and disposed between the clamping plates, are pairs of gripping wedges 1 6, each of which has an inclined clamping face, the angle of inclination of which is approximately 45 0 in this embodiment.

In use, the clamping plates 2 and 4 are separated and arranged either 1 side of a tow bar as shown in Figures 3 and 4. The clamping plates are positioned such that one of the pairs of clamping wedges bears against the inner radius of the curve of the tow bar whilst the other two pairs of wedges straddle the point of greatest curvature on the outer radius of the curve of the tow bar. Once assembled, the lock nuts and bolts are tightened so as to clamp the tow bar firmly between the gripping wedges.

By arranging for the curved tow bar neck to be clamped at three points, a much more secure connection is provided than is possible with standard clamping arrangements comprising a pair of clamp members. The three clamping points provide for much greater resistance to rotation of the fitting on the neck of the tow bar, a feature which is of considerable importance, for example when the fitting attached to the clamp is a mounting for retaining an upright post of a cycle rack.

- The gripping wedges 16 are arranged to be rotatable on the bolts and the advantage of this is that the clamp can accommodate a range of tow bars having necks of differing length and curvature. Furthermore, it has been found that fixing the gripping wedges to the plate so that they do not rotate gives a markedly inferior gripping action.

The gripping wedges in this embodiment have clamping faces which are inclined but substantially planar rather than curved and it has been found that this gives a better grip on the tow bar than when the clamping faces are hollowed out to conform to the shape of the tow bar. In order to improve still further the grip, the gripping wedges preferably have an array of relatively sharp ridges or protrusions on their surfaces which serve to bite into the surface of the tow bar.

Figure 1 illustrates one type of fitting that can be attached to the side 6 arm 6. The fitting 20 comprises a tubular sleeve 22 to which is attached, e.g. by welding, a generally channel-shaped formation 24 consisting of a pair of side plates 26 connected by cross plates 27 and 28. The ends of the side plates have apertures 30 for receiving bolts or locking bars for connecting the fitting to, for example, a support post for a cycle rack. The fitting'is secured to the side arm 6 by means of a bolt 34 which passes through an opening 36 in the end of the sleeve 22 and engages the thread in the bore of the side arm.

In order to prevent rotation of the fitting on the side arm, provision is made for an additional securing bolt. To this end, the sleeve 22 has an aperture 32 which serves as a pilot hole to enable a transverse hole to be drilled in an appropriate position on the side arm once the clamp has been fitted in place on the tow bar and the sleeve has been located and secured at a desired angular orientation. Once the pilot hole has been drilled, the resulting bore can then be widened to accommodate a suitable bolt (not shown) which passes through both sides of the sleeve 22 and transversely through the side arm and is secured in place by means of a lock-nut.

It will be appreciated that the fitting shown in Figure 1 is merely an example of one of many types of fitting that can be attached to the side arm. It will be appreciated also that the side arm can vary in shape, size and configuration depending on the nature of the fittings intended to be used in. conjunction with the clamp. For example, the side arm could be of hexagonal rather than circular section.

Furthermore, it will be appreciated that numerous modifications and alterations could be made to the embodiment shown in the drawings without departing from the principles underlying the invention and all such modifications and alterations are intended to be embraced by this application.

7

Claims

1 A clamping device for clamping to a curved region of a bar or rod, the clamping device comprising a pair of clamping members, one or both of theclamping members having connecting. means enabling the attachment thereto of another object; a plurality of gripping members disposed between the clamping members; and means for drawing the clamping members together so as to compress the gripping members against the curved region of the bar or rod; wherein the number of gripping members is such as to enable the curved region of the bar or rod to be gripped at three or more clamping locations along its length.

2. A clamping device according to claim 1 wherein the clamping members are in the form of a pair of clamping plates and the means for drawing the clamping members together are bolts extending between the plates.

3. A clamping device according to claim 2 wherein the gripping members are rotatably mounted with respect to the plates.

4. A clamping device according to claim 2 and claim 3 wherein the gripping members are rotatably mounted on the bolts extending between the plates.

A clamping device according to any one of the preceding claims wherein a pair of gripping members is provided at each clamping location.

6. A clamping device according to any one of the preceding claims wherein the clamping locations are arranged in a triangular array.

7. A clamping device according to claim 6 wherein the triangular array is i 1 8 substantially in the form of an equilateral triangle.

8. A clamping device according to claim 6 wherein the triangular array is in the form of a non-equilateral triangle.

9.

A clamping device according to any one of the preceding claims wherein each gripping member has an inclined gripping surface for gripping the bar or rod.

10. A clamping device according to claim 9 wherein the inclined gripping surface is substantially planar.

A clamping device according to any one of the preceding claims wherein the gripping members have gripping surfaces provided with one or more grip-enhancing protrusions and/or recesses.

12. A clamping device according to claim 11 wherein the gripping surfaces are provided with knurling or an array of elongate ridges for enhancing grip.

13. A clamping device for clamping to a curved bar or rod, the clamping device comprising a pair of clamping plates, one or both of the clamping plates having connecting means (such as a side arm) enabling the attachment thereto of another object; three pairs of gripping members disposed between the clamping members; and clamping bolts for drawing the clamping plates together so as to compress the gripping members against the curved bar or rod; the clamping bolts being arranged in a triangular array and each clamping bolt having one of the pairs of gripping members rotatably mounted thereon.

9

14. A clamping device according to any one of the preceding claims wherein the curved bar or rod is a vehicle tow bar.

15. A clamping device according to claim 14 wherein the tow bar has a neck and a ball-end, the neck tapering towards the ball-end.

16. A clamping device according to any one of the preceding claims wherein the connecting means is a side arm extending outwardly from one of the clamping members.

17. A clamping device substantially as described herein with reference to the accompanying drawings.