SUMMARY OF THE INVENTION According to the invention there is provided a coupling having an elongate construction, the coupling comprising first, second and third joints respectively permitting pivotal movement about first, second and third substantially orthogonal axes, the coupling being characterised in that when the coupling is made in use, the first and second joints are located in substantially the same axial position on the coupling and in that the third joint is spaced axially from said same position.

In the preferred embodiment of the coupling the first and second axes intersect and the third axis is in line with a longitudinal axis of the coupling.

Thus, the third joint permits pivotal movement about the longitudinal axis and in the event that the third axis extends horizontally, the first axis extends substantially vertically and the second axis substantially horizontally, but mutually perpendicular to the first and third axes.

In use, the first and second joints may be provided at or near the towing vehicle and the third joint is then spaced rearwardly therefrom.

The first joint may comprise two spaced lugs provided on a backing plate, the lugs defining registering holes and the backing plate being mountable on the vehicle so that the first axis extends through the registering holes; and a first shaft extending through the registering holes to be rotatable therein about its own longitudinal axis.

The second joint may comprise a second shaft extending through a transverse aperture in the first shaft, the aperture having as its centre axis said second axis, and an elongate member removably securable to the first shaft by said second shaft extending through said aperture in said first shaft, the elongate member being pivotable about said second axis.

The elongate member may comprise a fork- shaped head comprising two spaced prongs defining registering apertures for removably receiving said second shaft.

In use, the prongs straddle said first shaft and the second shaft

permits pivotal movement of the elongate member about the second axis.

In one embodiment the third joint may comprise a sleeve defining a circular bore; and a circular cylindrical region of the elongate member extending through the bore.

The sleeve is permanently mountable on the vehicle to be towed.

The bore of the sleeve may be lined with a bush and the sleeve may comprise a flange for mounting same on the vehicle to be towed.

The sleeve may be sandwiched in an axial direction on the elongate member between said forked shaped head and a stopping member mounted on the elongate member.

Alternatively, the sleeve may be biased by biasing means away from said forked-shaped head towards a stopping member mounted on the elongate member, so that the sleeve is capable of movement in an axial direction on the elongate member.

In another embodiment the third joint may comprise a U-shaped member defining registering holes in opposed legs thereof; and a region of said elongate member extending through said holes to be rotatable relative thereto.

The U-shaped member is permanently mountable on the vehicle to be towed.

The invention also includes within its scope a kit comprising a coupling as hereinbefore defined.

More particularly, there is provided a kit for forming a coupling between a towing vehicle and a vehicle to be towed, the kit comprising - a U-shaped member mountable on the towing vehicle; - the U-shaped member defining registering holes in opposed legs thereof; - a first shaft receivable in said registering holes; - a second shaft receivable in a transverse aperture defined in said first shaft; an elongate member comprising a shaft region and a

forked shaped head comprising two prongs; - the prongs defining registering apertures therein; - the elongate member being securable to the first shaft with the prongs straddling the first shaft and the second shaft extending through the registering apertures of the prongs and the transverse aperture in the first shaft; and - a member mountable on the vehicle to be towed, the member defining a passage way wherein a journal region of the shaft region of the elongate member is receivable to rotate relative to said member.

BRIEF DESCRIPTION OF THE ACCOMPANYING DIAGRAMS The invention will now further be described, by way of example only, with reference to the accompanying diagrams, wherein: figure 1 is a diagrammatic exploded perspective view of a first embodiment of a coupling according to the invention; figure 2 is a diagrammatic perspective view of a second embodiment of the coupling in an assembled form; figure 3 is a diagrammatic plan view of the coupling in figure 2, illustrating pivotal movement about a first axis and a third axis of three orthogonal axes;

figure 4 is a diagrammatic side view of the coupling in figure 2, illustrating pivotal movement about a second of said three orthogonal axes; figure 5 is a diagrammatic exploded perspective view of a third embodiment of the coupling according to the invention; and figure 6 is a diagrammatic perspective view of the coupling in figure 5 in assembled form.

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION A coupling according to the invention for coupling a vehicle to be towed (not shown) such as a caravan or trailer to a towing vehicle (also not shown) is generally designated by the reference numeral 10.1 in figure 1; 10.2 in figures 2 to 4; and 10.3 in figures 5 and 6.

The coupling according to the invention permits pivotal movement about first, second and third mutually orthogonal axes designated X, Y and Z in the figures. The coupling is of generally elongate construction and comprises first, second and third joints 12, 14 and 16 (shown in figures 2 and 6 ) for permitting the aforementioned

pivotal movement. The first and second joints 12 and 14 are located in substantially the same axial position relative to the longitudinal axis of the coupling and the third joint 16 is axially spaced therefrom.

In the embodiments shown, the first joint 12 comprises two spaced lugs 18.1 and 18.2 formed on a backing plate 20. Lugs 18.1 and 18.2 define registering circular holes 22.1 and 22.2. The backing plate 20 is permanently mountable at the rear of the towing vehicle.

The first joint 12 further comprises a first shaft 24 having a circular cylindrical body 24.1 and a head 24.3. Shaft 24 extends through the registering holes 22.1 and 22.2 and is rotatable therein. The shaft is preferably permanently locked in this position by a nut 25 cooperating with a thread on body 24.1.

The second joint 14 comprises a circular transverse aperture 24.2 defined in the body 24.1 of first shaft 24 and a second shaft 26 also having a circular cylindrical body 26.1 and a head 26.2. The second joint further comprises a head region 28.1 of an elongate member 28.

The head region comprises two spaced prongs 30.1 and 30.2. The prongs 30.1 and 30.2 define registering circular apertures 32.1 and

32.2 respectively.

When the coupling is made, the prongs 30.1 and 30.2 straddle body 24.1 and second shaft 26 extends through registering apertures 32.1, 24.2 and 32.2. Spacers 33.1 and 33.2 are provided between shaft body 24.1 and the prongs. The head region 28.1 and shaft 28.2 of elongate member 28 may be integraily formed as shown in figures 1 to 4 or may be separate and permanently securable to one another as shown in figure 5.

In the first and second embodiments of the coupling shown in figures 1 and 2 to 4 respectively, the third joint comprises a sleeve 34 defining a circular bore 36 and a circular cylindrical journal region of shaft 28.2 of the elongate member 28 extending through the bore, so that the elongate member 28 may rotate about its own longitudinal axis within bore 36.

In the second embodiment shown in figures 2 to 4, the region 28.2 and the sleeve 34 are also moveable relative to one another in an axial direction. A spring 40 is provided on region 28.2 to bias the sleeve 34 away from the head 28.1 and towards a stopper ring 42.

The stopper ring 42 is permanently and rigidly secured on the elongate member by a screw 43.

The sleeve 34 is formed on a flange 38 and the flange is permanently mountable on the vehicle to be towed, for example by welding it onto the vehicle.

In the third embodiment shown in figures 5 and 6 the sleeve 34 is substituted by a U-shaped bracket 44 defining registering holes 46.1 and 46.2 in opposed legs thereof. The bracket 44 is also permanently mountable by welding 45 on the vehicle 47 to be towed as shown in figure 6. In this embodiment the third joint is formed by the shaft 28.1 extending through the holes 46.1 and 46.2 and which shaft is rotatable in said holes about its own longitudinal axis.

Pivotal movement about the first axis X is illustrated in figure 3 as well as pivotal movement about third axis Z. Pivotal movement about second axis Y is illustrated in figure 4.

In use, the assembly comprising lugs 18.1 and 18.2 and the first shaft 24 is permanently mounted on the towing vehicle. Sleeve 34 or U-

shaped bracket 42, as the case may be, together with elongate member 28 are permanently mounted on the trailer as described hereinbefore.

In the case of the first and third embodiments shown in figures 1 and 5 and 6 respectively there is no provision for movement in an axial direction between the elongate member 28 on the one hand and either the sleeve 34 or the U-shaped bracket 44 on the other hand, as the case may be. In the embodiment of figure 1, the sleeve 34 is sandwiched in an axial direction on shaft 28.2 between head region 28.1 and a collar 42 permanently locked on shaft 28.2 by a screw 43.

In the embodiment of figures 5 and 6, the bracket 44 is sandwiched in an axial direction on shaft 28.2 between collars 48 and 50. A nut 52 serves to secure the complete assembly on the shaft 28.2.

To couple the trailer to the towing vehicle, shaft 26 is removed from the prongs 30.1 and 30.2, the prongs are then arranged to straddle shaft 24 and then shaft 26 is passed through the registering apertures 32.1, 24.2 and 32.2. Shaft 26 is then locked in this position by a circlip or the like or a lock 54 shown in figure 5.

To separate the trailer from the towing vehicle, shaft 26 is removed, the head 28.1 is removed from shaft 24 and the shaft 26 is re-inserted into registering apertures 32.1 and 32.2 in head region 28.1.

It will be appreciated that there are many variations in detail on the coupling according to the invention without departing from the scope and spirit of the appended claims.