The present invention relates to a device for stabilising a wheeled trailer towable behind a vehicle.

Wheeled trailers, such as caravans, horse boxes or boat trailers, are commonly towed by vehicles via ball and socket connections. The trailers are designed so that the trailer has a nose weight which is carried by the vehicle. Often, when the trailer itself is heavy or is heavily loaded, the rear of the vehicle will have to carry a considerable weight. This can result in a number of undesirable effects.

Firstly, the weight of the trailer bearing down on the rear of the vehicle can cause the front wheels of the vehicle to be lifted. This results in a loss of traction where the vehicle has front wheel drive. In addition, when the front of the vehicle is lifted and the headlights are on, the headlight beams are raised, dazzling drivers travelling in the opposite direction to the vehicle and trailer, even when the headlights are dipped. Further, the additional weight on the rear of the vehicle increases the wear and tear on the vehicle, particularly on its suspension.

More importantly, the trailer can start to snake from side to side whilst it is being towed by the vehicle. This can be caused by a cross-wind or passing traffic, particularly

heavy lorries, and is a serious problem when the vehicle and trailer are high sided.

At present, when the trailer starts to snake, the recommended practice for drivers towing the trailer is to accelerate to damp the snaking motion, and so stop the trailer overturning. In general, it is found that if a driver decelerates while a trailer is snaking, this increases the snaking motion, possibly overturning the trailer and/or causing an accident.

The snaking motion of the trailer is particularly a problem when the vehicle and trailer combination are travelling in heavy traffic, where it is not possible to accelerate to dampen the snaking motion, without hitting other road users.

Thus, in the past, vehicles towing trailers needed to have a powerful enough engine to have the capacity to accelerate should the trailer start to snake, restricting the types of vehicle able to tow some trailers. In any event, vehicle and trailer combinations often need to travel slowly, to allow drivers the margin to accelerate in case the trailer begins to snake.

It is a further problem determining the correct weight distribution between the vehicle and trailer. Thus, while an amount of nose weight is needed to bear down on the ball

and socket joint linking a vehicle to a trailer for towing stability, as mentioned above, too much nose weight can affect road holding. In practice, it is often difficult to determine the correct balance between trailer and vehicle to avoid snaking movement, and allow a trailer to be safely towed.

The present invention provides a device for stabilising a wheeled trailer towable behind a vehicle, the trailer having a nose weight carried by the vehicle, the device comprising;

(a) a frame attached or adapted for attachment to the trailer forward of said trailer wheels;

(b) a ground engaging wheel mounted on an axle connected to the frame, the wheel able to rotate about a generally upright axis to follow the direction of travel of the trailer, the wheel being arranged to carry a proportion of the nose weight of the trailer;

(c) a clutch operable to damp the rotation of the wheel about said upright axis; and,

(d) means for operating the clutch during deceleration so as to stabilise the trailer.

Accordingly, the device reduces the nose weight carried by the vehicle, thereby reducing the level of wear and tear on the vehicle and ameliorating traction loss. This is because a proportion of the weight of the trailer is carried by the ground engaging wheel of the device, rather

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than by the vehicle itself. This allows a wider range of vehicles to tow a given trailer, eg vehicles with less powerful engines.

In addition, the device allows the vehicle to brake safely, even while the trailer is snaking. This is because, when the vehicle decelerates, the clutch operates to damp the rotation of the ground engaging wheel about its upright axis, thereby helping to stop the snaking motion of the trailer. Thus, the device helps to make it safer and easier to tow a trailer.

Preferably, the clutch comprises a disk movable with the rotation of the ground engaging wheel about its upright axis and means operable to grip the disk to damp its movement. In one embodiment, the means to grip the disk is a caliper having brake shoes lining its inner surfaces, thereby to grip the disk.

Some trailers, for instance caravans, are provided with a brake system that operates to slow the trailer when the vehicle towing the trailer decelerates. In this case, the clutch can advantageously be connected to this brake system, so that the clutch operates to stabilise the trailer when the brake system of the trailer operates. Alternatively, the clutch can be arranged to operate independently of the brake system of the trailer or that of the vehicle.

Conveniently, the device includes means to adjust the proportion of the nose weight of the trailer carried by the device, so that it is possible to optimise the distribution of nose weight of the trailer between the device and the car. Thus, it is possible to adjust the nose weight carried by the device to achieve maximum stability for the vehicle and trailer combination. Suitably, the means to adjust the proportion of the weight is a jack, the jack being connected to the frame and capable of moving the frame to raise or lower the ground engaging wheel.

Preferably, the device includes resilient suspension means, linking the wheel to the frame. This helps to damp the movement at the front of the trailer as the vehicle and trailer travel over bumpy surfaces. Advantageously, the suspension means can also include one or more shock absorbers to help achieve this.

Preferably, the ground engaging wheel is of a trailing link type so that it is offset relative to the generally upright axis about which the wheel can rotate relative to the trailer. This has the advantage that the wheel is capable of rotating about the upright axis to follow the direction of travel of the trailer when the vehicle and trailer reverse direction.

In the present invention, "a generally upright axis" is, unless the context demands otherwise, defined as being

approximately vertical relative to the trailer, unless the axis is deliberately angled for some reason.

Advantageously, the frame of the device is attached or adapted for attachment to an A-frame of the trailer. The device is generally attached using a system of brackets and bolts known in the art. The device is preferably attached to the nearside of the A-frame of the trailer so that it is offset from the trailer's centre line. This has the advantage that the ground engaging wheel helps to support the trailer on the side of the road where the camber is steepest. This increases the stability of the trailer across the road.

The present invention also includes a trailer incorporating a device as described above.

Although the device has been described above particularly with reference to caravans, the present invention is also suitable for fitting to horseboxes, car or motorcycle trailers, boat trailers or any other trailer of the type having a nose weight that is towable behind a vehicle.

A preferred embodiment of the present invention will now be described with reference to the accompanying drawings in which:

Figure 1 shows a partial side view of a stabilising device;

Figure 2 shows a cross-section through the clutch of the stabilising device;

Figure 3 shows a view along line A-A of figure 2, showing the under side of the clutch; and, Figure 4 shows one way of attaching a frame of the stabilising device to a trailer.

In the figures, a stabilising device 2 comprising a frame 4 for attachment to a trailer, a ground engaging wheel 6 and a clutch 8 is shown.

In figure 1, the ground engaging wheel 6 is mounted on an axle 9, the axle 9 being connected to arm 10 and to arm 12 through resilient suspension 14, including shock absorbers. The arms 10,12 are pivotally mounted on frame member 16 and are able to pivot about points 18,20 respectively. The frame member 16 is mounted to frame 4 through bearings 22, so that the wheel 6 can freely rotate about an approximately upright axis. The wheel 6 is a trailing link wheel, so that when the direction of travel of the trailer changes, the wheel 6 will automatically rotate about the upright axis to follow the direction of travel.

The height of the wheel 6 from the ground can be adjusted using a jack 44, to vary the amount of nose weight of the trailer that the stabilising device 2 supports. The jack 44 comprises an apertured member 46, fixedly connected to arm 12, and a screw thread 48 connected to frame member 16

via ball and socket joint 50. The screw thread 48 can therefore rotate in the ball and socket joint 50. The threaded portion of the screw 48 engages the threaded aperture of member 46.

The height of the wheel can be changed by rotating the screw thread 48, driving the member 46 up and down the thread of the screw. This causes the arms 10,12 to move relative to each other about pivots 18,20, lifting or lowering the wheel 6. This is useful as the amount of weight the stabilising device 2 supports can be easily varied to balance the vehicle and trailer combination. If necessary, this also allows the wheel 6 to be easily changed, by using the jack 44 to lift the wheel 6 clear of the ground.

The clutch 8 includes a disk 28 mounted to the frame 4 and connected to the top 26 of the frame member 16 through axle 24 (shown in dotted lines). The disk 28 is separated from the frame 4 by a spacer 30 and bearings 22. The rotation of the wheel 6 is also keyed to the axle 24. Thus, the rotation of the wheel 6 about the upright axis causes the disk 28 to rotate.

Figures 2 and 3 show enlarged views of the clutch 8. The clutch 8 includes a caliper 32 attached to the frame 4 through linking member 34. The caliper 32 is approximately C-shaped, with the disk 28 locating in the mouth of the C.

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The caliper 32 has brake shoes 36 attached to the inside of the C by a split pin 41. The brake shoes have linings 38 that lightly contact the surface of the disk 28 or are held just clear of it.

The clutch 8 is operated through arm 40, the arm 40 depending from the head of bolt 42. The bolt 42 is retained in a threaded aperture in the lower half of the caliper 32. The aperture passes through the caliper 32 and is occupied by a spring 44, held in place against the lower brake shoe 36 by the shank of the bolt 42. The arm 40 is attached to a cable 52 which, when operated, causes the head of the bolt 42 to rotate and move into the aperture. When this happens, the shank of the bolt presses against the spring 44, tightening the grip of the brake shoes 36 on the disk 28 and restricting the movement of the disk 28 and wheel 6 about the upright axis. This serves to damp the movement of the disk. The cable 52 locates in sheath 53, the sheath 53 being fixed to the lower face of the caliper to allow the cable 52 to move in and out of it.

In this example, the clutch 8 is adapted for attachment to the brake system of the trailer being towed. Thus, when the trailer brake system operates, this causes the cable 52 to tighten, pulling arm 40 against spring 54, thereby tightening the grip of the brake shoes 36 on the disk 28 as described above. This has the effect of damping any rotation of the wheel 6 about its upright axis, thereby

helping to prevent the trailer snaking.

When the brakes of the trailer are released, the cable 52 slackens and spring 54 restores the arm 40 to a position where the grip of the brake shoes 36 on the disk 28 is released, allowing the wheel to rotate freely about its upright axis.

The amount of rotational movement of the bolt possible when the arm 40 rotates can be adjusted by moving lock nut 56 up or down the thread of the bolt 42. This provides a way of varying the strength of the damping effect on the disk 28.

Figure 5 shows a portion of the frame 4 of the stabilising device 2 adapted for attachment to the A-frame 56 of a trailer. The frame 4 is provided with attachment brackets 58, the brackets 58 comprising a lipped plate 60 retained on the attachment bracket by nut 62 and bolt 64. The plates 60 locate over the C-section portions of the A-frame 56 the trailer, with the lip locating over the C-section portions of the trailer. Thus, when tightened, the attachment brackets 58 hold the stabilising device 2 to the A-frame.

The stabilising device 2 may either be provided as a kit for attachment to existing trailers or may be fitted to new trailers during manufacture. In either case, the stabilising device 2 is attached to the A-frame 56 of the

trailer forward of the trailer wheels, so as to support at least a proportion of the nose weight of the trailer.

In use, while the vehicle and trailer, combination are travelling along normally, the wheel 6 will rotate about the upright axis to follow the direction of travel. However, when the vehicle decelerates, the clutch 8 will operate, restricting the movement of the wheel 6 about its upright axis and helping to damp or prevent the trailer snaking. Thus, the stabilising device 2 makes it possible to brake while the trailer is snaking, rather than having to accelerate to damp the snaking motion and to avoid the trailer overturning.