According to one aspect of the invention there is provided a method of improving the steerability of a vehicle and trailer combination when reversing, which includes the step of locking the trailer to the vehicle so as to resist pivoting of the trailer relative to the vehicle when reversing.

The method may include locking the trailer to the vehicle automatically when reverse gear of the vehicle is selected.

According to another aspect of the invention there is provided a reverse-steerable trailer which includes: a wheeled chassis; a tow-hitch mounted on a leading end of the chassis for pivotally connecting the trailer to a tow bar mounted on a towing vehicle; and locking means for releasable locking the trailer to a said towing vehicle to resist relative pivotal movement of the trailer and vehicle when reversing.

More specifically according to the other aspect of the invention, there is provided a reverse- steerable trailer which includes: a wheeled chassis; a tow-hitch mounted on a leading end of the chassis for pivotally connecting the trailer to a tow bar mounted on a towing vehicle ; a connecting member mounted on the chassis for connecting the trailer to the towing vehicle, the connecting member being displaceable between extended and retracted positions to permit pivotal movement of the trailer about said pivotal connection when towing; and locking means for releasably locking the connecting member at a desired position to resist said pivotal movement thus holding the trailer fast with the towing vehicle when reversing.

The tow-hitch may be a standard ball-and-socket type tow-hitch. The connecting member may comprise a telescopic bar which is telescopically extendable and retractable. Typically, the telescopic bar comprises a tubular outer member and an inner member telescopically slidable within the outer member.

The telescopic bar may be pivotally connectable at one end to the towing vehicle via a standard ball-and-socket type tow-hitch and pivotally connected at its opposite end to a corner of the leading end of the chassis via a universal joint.

In one embodiment, the locking means is operable from the towing vehicle and comprises a solenoid locking mechanism. Preferably, the solenoid locking mechanism is electrically connectable to the towing vehicle so that the solenoid locking mechanism is operable automatically by engaging reverse gear and is inoperative when the towing vehicle is in neutral or a forward gear.

The chassis may comprise a frame having at least one pair of wheels rotatably mounted about a transverse axis and supporting the frame. The frame may be a conventional frame used for trailers and includes a cross-member on which the wheels are rotatably mounted for rotation about said transverse axis. In a preferred embodiment, the cross-member may be connected to the remainder of the frame by a resilient suspension system. The suspension system may include a pair of transversely spaced springs, for example leaf springs.

The wheels may include any suitable trailer wheels, for example, two sets of castor wheels.

Preferably, each set of castor wheels connected to each other by abridge member having an upright pivot attached thereto. The two pairs of castor wheels may be connected via their respective upright pivots to opposite ends of the cross-member.

In this embodiment, the trailer includes and associated locking mechanism operable from the towing vehicle for locking the respective pairs of castor wheels by preventing pivotal movement of said upright pivots, the locking mechanism being adapted to unlock automatically the two pairs of castor wheels when reverse gear is engaged by the towing vehicle and to lock them automatically when reverse gear is disengaged by the towing vehicle.

The locking mechanism may comprise a solenoid locking mechanism as herein above described and electrically connectable in a similar fashion to the towing vehicle.

In yet another embodiment of the invention, the cross-member may be mounted for rotation about a transversely extending axis of rotation, the wheels being connecting to the cross-member such that their axes of rotation are spaced from the axis of rotation of the cross-member, the apparatus including displacement means for rotating the cross-member and thereby adjusting the castor angle of the wheels, i. e. the angle relative to the vertical of a line extending between the axes of rotation of the wheels and the axis of rotation of the cross-member perpendicular thereto, to facilitate steering of the wheels when reversing.

According to another aspect of the invention there is provided a lockable connecting member for connecting a trailer to a towing vehicle, the member, in its unlocked position, being displaceable between extended and retracted positions to permit pivotal movement of the trailer when towing and, in its locked position, preventing said pivotal movement thus holding the trailer fast with the towing vehicle when reversing.

The connecting member may comprise a telescopic bar as herein above described. The telescopic bar may comprise locking means, for example, a solenoid locking mechanism, operable from the towing vehicle as herein above described.

In use, for normal towing, the telescopic bar is unlocked and the two pairs of castor wheels are locked. During turning of the towing vehicle, the telescopic bar extends or retracts to prevent the bar interfering with the pivotal movement of the trailer. When the driver of the towing vehicle wishes to reverse, for example, into a parking space in a car park, the driver will align the trailer longitudinally with the towing vehicle, and engage reverse gear. On engaging reverse gear in the towing vehicle, the solenoid locking mechanisms operate automatically to lock the telescopic bar in a position to prevent pivotal movement of the trailer and to maintain the trailer fast with and in longitudinal alignment with the towing vehicle, and simultaneously to unlock the two pairs of castor wheels which become steerable thereby.

The invention will now be described, by way of example with reference to the accompanying diagrammatic drawings.

DESCRIPTION OF DRAWINGS In the drawings, Figure 1 shows a plan view of a trailer in accordance with the invention; Figure 2 is a side elevation corresponding to Figure 1 ; Figure 3 shows a rear elevation corresponding to Figure 1; Figure 4 shows a sectional elevation taken at IV-IV in Figure I ; Figure 5 shows a sectional elevation taken at V-V in Figure 1; Figure 6 shows a plan view of another trailer in accordance with the invention, certain details has been omitted for the sake of clarity; and Figure 7 shows a side view of the trailer of Figure 6.

Referring to Figure 1 to 5 of the drawings, reference numeral 10 generally indicates a reverse- steerable trailer in accordance with the invention.

The trailer 10 comprises a wheeled chassis, generally indicated by reference numeral 12, a tow- hitch 14 mounted on the leading end 12.1 of the chassis 12, a connecting member in the form of a telescopic bar, generally indicated by reference numeral 16, mounted on the leading end 12.1 of the chassis 12, and locking means in the form of a solenoid locking mechanism 18, located on the telescopic bar 16.

The chassis 12 comprises a frame 20 having two pairs of castor wheels 22, rotatably mounted about a transverse axis and supporting the frame 20. The frame 20 includes a cross-member 24 on which the pairs of castor wheels 22 are rotatably mounted at opposite ends and the frame further includes a resilient suspension system incorporating a pair of springs in the form of leaf springs 26 whereby the cross-member 24 is connected to the remainder of the frame20.

Each pair of the castor wheels 22 is connected to each other by a bridge member 28 having an upright pivot arm 30 attached thereto. The two pairs of castor wheels 22 are connected via pivots 31 protruding upwardly from upper ends of their respective upright pivot arms 30 to said opposite ends of the cross-member 24, and the trailer has associated locking means in the form of a solenoid locking mechanism 32 operable from the towing vehicle (not shown).

The telescopic bar 16 is extendable and retractable and comprises a tubular outer member 16.1 and am inner member 16.2 telescopically slidable within the outer member 16.1.

The telescopic bar 16 is pivotally connected at one end to a standard tow bar (not shown) of the towing vehicle via a standard ball-and-socket type tow-hitch 34 and at its opposite end to the left hand corner of the leading end of the chassis 12.1, as generally indicated by reference numeral 36, via a universal joint 38.

The solenoid locking mechanism 18 is electrically connected to the reverse gear of the towing vehicle e. g. via reverse light. As can best be seen in Figure 4 of the drawings, the inner member 16.2 includes a plurality of longitudinally spaced apart teeth or locking formations 50 cut therein. The solenoid locking mechanism 18 comprises a bracket 52 and outer member 16.1 have radially extending registering holes therein. A solenoid 54 is mounted on the bracket 52 with a core 56 of the solenoid 54 in register with the holes in the bracket 52 and outer member 16.1. A plunger 58 is mounted on an end of the core 56 protruding into the bracket 52 with the plunger 58 being slidably displaceable between a retracted position (shown in Figure 4 of the drawings) in which it is clear of the inner member 16.2 and a protruding position in which it engages the teeth 50 to lock the inner member 16.2 in position relative to the outer member 16.1. Bias means in the form of a coil spring 60 urges the core 56 and hence the plunger 58 resiliently towards its retracted position.

As can best be seen in Figure 5 of the drawings, each solenoid locking mechanism 32 comprises a solenoid 62 mounted on the cross-member 24. The solenoid 62 includes a core 64 which is displaceable between a normally protruding position (shown in Figure 5 of the drawings) and a retracted position. Bias means in the form of a coil spring 66 is provided to urge the core 64 towards its protruding position. A recess 68 is provided in the pivot 31 and is positioned to be in register with the protruding end of the core 64 when the axes of the wheels 22 extend perpendicularly to the length of the trailer 10.

The tow bar is modified at its connecting end by an adaptor bar 40 comprising a hardened steel plate or length of angle iron 42,400 mm in length, having two laterally spaced goose neck connectors 44,46 connected to the standard tow-hitches 14,34 respectively.

In normal towing, the core 56 of the solenoid 54 is in its retracted position and the telescopic bar 16 is hence unlocked. The core 64 of the solenoids 62 are in their protruding positions such that they are positioned in the recesses 68 resulting in the two pairs of castor wheels 22 being locked.

On turning the towing vehicle, the telescopic bar 16 simply extends or retracts and does not interfere with the pivotal movement of the trailer 10 about the pivotal connection 14.

To reverse, for example, into a parking space in a car park, the driver alines the trailer longitudinally with the towing vehicle and, on engaging reverse gear in the towing vehicle, the solenoid locking mechanism 18 and 32 are activated to automatically lock the telescopic bar 16 in position preventing any pivotal movement of the trailer 10 about the pivotal connection 14 and to maintain the trailer 10 fast with and in longitudinally alignment with the towing vehicle, and simultaneously automatically unlocks the two pairs of castor wheels 22 which thereby become steerable when the towing vehicle is reversing. On disengaging reverse gear, the solenoid locking mechanisms 18,32 are inactivated to automatically unlock the telescopic bar 16, and simultaneously automatically lock the two pairs of castor wheels 22 in the forward direction to permit normal towing.

Reference is now made to Figure 6 of the drawings, in which reference numeral 80 refers generally to another trailer in accordance with the invention and where, unless otherwise indicated, the same reference numerals used above are used to designate similar parts. In this embodiment of the invention, the cross-member 24 is circular in cross-section and is supported rotatably within a tubular support 82 which is connected to the remainder of the frame 20 by means of the springs 26. Single wheels 22 are mounded on stub axles 84 which in turn are pivotally mounted on king pins 86 protruding radially from opposite ends of the cross-member 24. Hence, the axes of rotation of the wheels 22 about the stub axles 84 are spaced from the axis of rotation of the cross-member 24 within the tubular support 82. Rotation of the cross- member 24 relative to the tubular support 82 is effected by means of an eclectic motor 88 acting on the cross-member via a reduction gearbox 90. The stub axles 84 are interconnected by means of linkages, generally indicated by reference numeral 92 displacement of which is effected by means of an electric motor 94 driving a gearbox 96.

In use, the castor angle, i. e. the angle of the king pings 86 relative to the vertical will be zero or negative as indicated by the angle A in Figure 7 of the drawings. In other words, the axes of rotation of the wheels 22 will be positioned behind the axis of rotation of the cross-member 24.

When it is desired to reverse, the driver aligns the trailer longitudinally with the towing vehicle and, on engaging the reverse gear in the towing vehicle, the electric motor 88 is energized so as to rotate the cross-member 24 within the tubular support 82 such that the castor angle becomes positive indicated by B in Figure 7 of the drawings. Hence, when reversing the wheels will once again trail the cross-member 24 permitting them to be steered. When disengaging reverse gear, the electric motor 88 rotates the cross-member in the opposite direction so as to return the castor angle to a desired angle for normal towing in a forward direction. Simultaneously, sensors (not shown) sense the position of the wheels 22 and if necessary, the electric motor 94 is energized so as to displace the wheels into their normal or operative position for forward movement.

A steering problem arises with any trailer when the driver of the towing vehicle wishes to revers.

Also, any towing vehicle with a high boot profile makes the trailer almost invisible to the driver and this problem is exacerbated when driving a mini-bus, truck or bus. It is an advantage of the invention that these problems are overcome or minimized by the trailer 10,80.