GB2267134A

GB2267134A - Trailer vehicle

Info

Publication number: GB2267134A
Application number: GB9210938A
Authority: GB
Inventors: Paul Thomas Goy
Original assignee: Paul Goy
Current assignee: Paul Goy
Priority date: 1992-05-22
Filing date: 1992-05-22
Publication date: 1993-11-24
Anticipated expiration: 2012-05-22
Also published as: GB2267134B; GB9210938D0

Abstract

A trailer vehicle of the type having wheel brakes operable by an overrun braking system (2, 6, 7, 9) is provided with additional brake control means (13-15) electrically connectable to the brake-warning light circuit of the towing vehicle and arranged to apply the brake in response to detection of an electrical signal in said circuit. By braking the trailer slightly ahead of the braking of the towing vehicle, snaking of the trailer vehicle may be stopped or reduced. <IMAGE>

Description

TRAILER VEHICLE Field of the Invention This invention relates to a trailer vehicle, and more particularly to the type having wheel brakes operated by an over-run braking system, which uses the momentum of the trailer vehicle to apply the brakes when the towing vehicle is braked.

Background to Invention It is usual for the trailer to be linked to the towing vehicle through a longitudinally slidable arm which is sprung or hydraulically-damped, the arm moving rearwardly relative to the trailer when the towing vehicle is braked, the movement being transmitted via a lever to brake cables, or being applied to a hydraulic brake master cylinder connected to a slave cylinder at each wheel. An example of such a trailer is a trailer caravan.

A problem encountered when towing a trailer at speed, particularly down an incline, is the tendency under certain conditions for the trailer to begin to swing or yaw relative to the towing vehicle, in a movement commonly referred to as "snaking", making control of the vehicle more difficult. Typically, braking of the towing vehicle under these conditions exacerbates the unstable movement of the trailer, the trailer tending to move outwardly of the longitudinal towing axis before its brakes take effect.

Various devices have been made available to reduce the tendency of the trailer to undergo snaking under adverse conditions. These typically involve reducing the freedom of rotation at the coupling between the towing vehicle and the trailer (normally a ball-and-socket coupling) by a friction linkage in parallelogram form, are complicated to fit and to maintain, and often provide only a partial cure for snaking.

In FR-A-2 476 006 an arrangement is proposed in which a pneumatic cylinder is linked to the parking brake lever of a caravan over-run braking system, compressed air from a storage reservoir on the caravan being supplied to the cylinder via an electrically-operated control valve connected to a control switch near to the driver of the towing vehicle. This arrangement is said to permit the driver to control any snaking movement by the selective application of the trailer brakes independently of the towing vehicle's brakes.

While the application of the trailer brakes in advance of the towing vehicle's brakes is desirable in controlling snaking, the arrangement proposed in FR-A-2 476 006 requires modification of the towing vehicle to install additional electrical wiring to that normally required for use in towing, and the installation on the trailer of a relatively bulky and expensive pneumatic system which requires the regular replenishment of the compressed air cylinder to enable it to be effective. Further, the arrangement appears to operate the parking brake lever, which would not be practical in many existing trailers, in which the level is ratchet operated to hold the brakes on when pulled and to requires manual release.

Summarv of the Invention The present invention provides a trailer vehicle having wheel brakes operable by an over-run braking system and having additional brake control means electrically connectable to the brake-warning light circuit of the towing vehicle and arranged to apply the brakes in response to detection of an electrical signal in said circuit.

Most trailer vehicles are provided with an electrical system connectable to that of the towing vehicle and including brake-warning lights which operate with those of the towing vehicle. In such trailer vehicles, the additional brake control means may be directly connected to the trailer vehicle's brake light circuit to derive the controlling electrical signal therefrom.

Suitably, the additional brake control means are arranged to apply a braking force which is less than the maximum which can be applied by the over-run system, since it is undesirable to lock the trailer brakes; it is sufficient to provide an intermediate braking force, so that the trailer is retarded relative to the towing vehicle, to overcome any snaking movement. This is achieved by the driver depressing the brake pedal of the towing vehicle sufficiently to activate the brake-warning lights but not so far as to cause significant application of the towing vehicle's brakes.

Conventionally, a vehicle's brake-warning lights are arranged to operate in this way.

In another aspect of the invention, a trailer vehicle having an overrun braking system is provided with means for detecting the onset of snaking, for example a suitably orientated level switch arrangement, and additional brake control means arranged to apply the brakes in response to a signal therefrom.

The system suitably incorporates both a connection to input a brake warning light signal and a connection to input a snaking detector output signal, either signal serving to cause application of the brakes. Preferably in this embodiment the brakes are applied with a higher force in response to detection of the onset of snaking than in response to detection of brake-warning light signal.

Where the over-run braking system comprises cable-operated brakes, the additional brake control means preferably comprise electrically powered means for applying tension to the cables. For example, a lever may be coupled to the cables, the lever being turned by an electric motor, for example through a lead-screw arrangement. An alternative arrangement could include a solenoid linked to a force-amplifying means.

Brief Description of the Drawings Figure 1 is a perspective view of a trailer chassis in accordance with one embodiment of the invention; and Figure 2 is an enlarged plan view of a brake actuator forming part of the trailer shown in Figure 1.

Detailed Description of the Illustrated Embodiment The trailer chassis 1 illustrated in Figure 1 is a conventional form used for caravans, and has a generally A-shaped configuration, the peak of the A carrying the towing hitch 2, jockey wheel 3, and electrical connecting plug 4. The towing hitch 2 comprises a brake actuator which, when the caravan over-runs the braking towing vehicle causing the coupling head 5 to move rearwardly relative to the caravan, draws a braking cable or rod 6 forwardly. The braking cable 6 extends to a linking plate 7 at the cross-member 8 of the chassis where the movement is translated to a pair of bowden cables 9, each extending to a respective wheel 10 to operate the brake therein.

The electrical connecting plug 4 links the caravan's electrical system to that of the towing vehicle. Connections are made for direction indicators, tail and front lights, rear fog lights and brake warning lights 11, the latter via an electrical connection 12 extending from the plug 4. In the trailer illustrated in Figure 1, the electrical connection 12 extends not directly to the lights 11 but by way of an electrical controller 13 installed, for example, beneath the caravan body. The controller 13 is in turn connected via a wire 14 to an additional brake actuator 15, shown in more detail in Figure 2, mounted on the cross-member 8.

The actuator 15 comprises an electrical motor 16 driving a lead screw 17 on which is threaded a slide member 18 coupled to a forked lever 19 via a peg 20. The lever 19 is pivoted on the casing of the actuator 15 and carries, via a pivoted mount 21 at its free end, a sleeve 22 which fits over the braking cable 6 and is clampable to it by a clamping screw 23.

In use, the controller 13 detects the brake warning light signal from the towing vehicle and supplies current to the motor 16, which rotates at high speed to apply, via the lever 19, a braking force to the bowden cables 9 to operate the brakes. On release of the signal, the controller 13 causes the motor to run in reverse to release the brakes, assisted by the brake release springs.

A separate electrical supply from the towing vehicle's battery will usually be provided for the controller 13, in order to ensure that it can supply sufficient working current for the motor 16 under all operating conditions. Such a supply is often available in a caravan via the plug 4 or a separate auxiliary supply connector supplying a battery in the caravan, or for operating interior lights for the caravan, for example.

The controller 13 may also include therein a motion-sensor to detect the onset of snaking, for example where application of the brakes via light pressure on the towing vehicle's brake pedal is insufficient, or where the driver has failed to use the brakes. This may signal the application of a higher braking force via the actuator 15.

Claims

1. A trailer vehicle having wheel brakes operable by an over-run braking system and having additional brake control means electrically connectable to the brake-warning light circuit of the towing vehicle and arranged to apply the brakes in response to detection of an electrical signal in said circuit.

2. A trailer vehicle according to Claim 1, comprising an electrical system connectable to that of the towing vehicle and including brakewarning lights which operate with those of the towing vehicle, wherein the additional brake control means are directly connected to the trailer vehicle's brake light circuit to derive the controlling electrical signal therefrom.

3. A trailer vehicle according to Claim 1 or 2, wherein the additional brake control means are arranged to apply a braking force which is less than the maximum which can be applied by the over-run system.

4. A trailer vehicle according to Claim 1, 2 or 3, comprising means for detecting the onset of snaking, and the additional brake control means are arranged to apply the brakes in response to a signal therefrom.

5. A trailer vehicle according to Claim 4, wherein the additional brake control means are arranged to apply the brakes with a higher force in response to detection of the onset of snaking than in response to detection of brake-warning light signal.

6. A trailer vehicle having an over-run braking system and comprising means for detecting the onset of snaking, and additional brake control means arranged to apply the brakes in response to a signal therefrom.

7. A trailer vehicle according to Claim 6, wherein the means for detecting the onset of snaking comprises a suitably orientated level switch arrangement.

8. A trailer vehicle according to any preceding claim, wherein the over-run braking system comprises cable-operated brakes, and the additional brake control means comprises electrically powered means for applying tension to the cables.

9. A trailer vehicle according to Claim 8, wherein the electricallypowered means comprise a lever coupled to the cables, the lever being turned by an electric motor, through a lead-screw arrangement.

10. A trailer vehicle according to Claim 8, wherein the electricallypowered means comprise a solenoid linked to a force-amplifying means.

11. A trailer vehicle, substantially as described with reference to, or as shown in, the drawings.