GB2386592A

GB2386592A - Trailer coupling device

Info

Publication number: GB2386592A
Application number: GB0206384A
Authority: GB
Inventors: Lee Mangnall
Original assignee: Indespension Ltd
Current assignee: Indespension Ltd
Priority date: 2002-03-19
Filing date: 2002-03-19
Publication date: 2003-09-24
Also published as: GB0206384D0

Abstract

A trailer coupling comprises shaft 5 connected to a towed vehicle, and a connector 1 for connection to a towing vehicle, a shaft 3 connects the connector 1 via a damper 6 to a sleeve 7 within which the damper 6 is slidable. Sleeve 7 receives a fitting 8, 9 at each and, one of which ends connects with shaft 3 the end of which connects with a lever 15 which is connected to a brake 17 on the towed vehicle.

Description

TRAILER COUPLING-DEVICE

This invention relates to an improved trailer coupling device, of the kind for coupling a towing vehicle to a towed vehicle for example in an automobile trailer or automobile caravan combination.

5 Because of the risk of jack-knifing of a trailer or caravan where a towing vehicle is forced to decelerate, trailer coupling devices now customarily include devices for protection against overrun, so that for example brakes of the towed vehicle can be applied when the speed of the towed vehicle exceeds that of the towing vehicle during deceleration 10 of the towing vehicle until the speed is equalised. The present invention relates to an improved overrun protection device in a trailer coupling A known overrun protection device in a trailer coupling generally speaking includes a buffer device for absorbing compressive forces arising in the coupling when the towing vehicle decelerates, and a lever 15 responsive to compressive forces to actuate the brakes of the towed vehicle. The coupling normally includes damping devices such as springs or hydraulic shock absorbers, which absorb transient variations in traction exerted on the coupling and an initial component of any deceleration.

20 The coupling normally comprises a first part for connection to the towing vehicle, and a second part for connection to the trailer, and each part includes a respective sleeve, or tubular part one of said sleeves being slidably received within the other said sleeve, so that during deceleration

-2 the inner sleeve will be pushed into the outer sleeve, and vice versa during acceleration. The overall coupling length thus shortens during relative deceleration of the towing vehicle and trailer, and extends during relative acceleration. The sleeves are arranged so that after a certain 5 amount of force has been absorbed by pushing the sleeves together, further force on the first part will displace the assembly yet further, and cause a brake-operating lever to be actuated to apply the brakes of the trailer. In the prior art it is customary to use nylon or other synthetic

10 material slide bushes for the relatively displaceable sleeves. These bushes are prone to being forced apart if corrosion takes place in the coupling tube. Some manufacturers choose to use other materials such as steel, which have a higher co-efficient of friction, such as steel sliding on cast iron. However, the efficient operation of the coupling and braking 15 mechanism requires a smooth load transmission from the drawbar tube to the brake, and higher friction materials, or bushes affected by corrosion have a tendency to operate jerkily with a stick- release action as zones of higher resistance are encountered and then overcome when force has built to a sufficient level, leading to a sudden release and to possible 20 ejection of one or more bushes from their location.

It is thus an abject of the invention to provide a construction of device, which enables a low friction material to be used without

-3 impairment and to ensure a smooth sliding action and a secure retention system, which will not be impaired by corrosion.

According to the invention, in a coupling comprising a first part fixed relatively to a towed vehicle, and a second part relatively moveable 5 to said first part for connection to a towing vehicle, one of said parts providing an outer member and the other of said parts providing an inner member which is slidably received within said outer member wherein said inner member comprises a sleeve which receives at one end as a compression fit in a end portion of a member connected to either first or 10 second part and at its other end a similar fitting to an operating lever for the brake device of said towed vehicle.

The member compression fit at each end of the sleeve may be a low friction em nylon or other synthetic material bush having end slots which allow radial compression of the bush, and having a detent formed 15 on the outer face of the bush for engagement with an internal groovein the sleeve so that a bush can be pushed into each end of the sleeve and snap fitted into the grooves to prevent pulling out of the bushes.

Each bush can then act as a seat or receptor for the end of a shaft one connected to the first part, and the other to the brake-operating lever.

20 The sleeve may be an outwardly smooth steel tube, which is arranged to be slidable within an outer connected to the second part.

-4 A preferred embodiment of coupling according to the invention will now be described by way of example with reference to the accompanying drawings wherein: Figure 1 is a general view of a trailer coupling according to the 5 invention; Figure 2 is an enlarged view of a sleeve member forming a part of the coupling of Figure 1; Figure 3 is a detail showing a bush being inserted into an end of a sleeve of Figure 2; and 10 Figure 4 is a detail similar to Figure 3 showing the bush after insertion into the end of the sleeve.

A trailer coupling comprises a standard connector 1, enclosed by a protective bellows or pleated cylinder 2 which surrounds a tubular shaft 3 and is seated at its inner end on a member 4 which is in turn connected 15 to a shaft 5 which is rigidly connected to a trailer body.

The connector 1 is connected through slots (not shown) in the shaft 3 to a damper 6, which extends axially within the shaft 3 and carries a sleeve 7, within which shaft 3 is slidable.

Sleeve 7 is better shown in figure 2 and comprises a tubular steel 20 sleeve, which receives a tubular nylon bush 8, 9 at each end for mounting the sleeve on the damper. Each bush 8 or 9 comprises an inner end which is provided with cut slots 10 which enable the inner end to be compressed for insertion into the sleeve 7, as shown in figure 3, and a

-5 connected conical flange 11 which provides a rearward step which engages as a detent in a groove 12 formed on the inner surface of sleeve 7 (as shown in figure 4). The bush 8 or 9 also has an outer end formed with wider part 13, which forms a stop, which cooperates with the end of 5 the sleeve 7 to prevent deeper insertion of the bush into the sleeve.

The bushes are mounted on the exterior of the shaft 6, which terminates at the end of the sleeve. This end serves as a seat for one end of a bell crank lever 15, which operates, via a link rod 16, a brake mechanism 17 which is only shown symbolically in the drawing.

10 In use, the damper 6 absorbs traction variations between the towing vehicle and the trailer and an initial component of any relative deceleration. Further deceleration causes damper 6 to be displaced to the right in figure 1 with possible further lost motion using slots in the outer sleeve, 15 until the sleeve 7 reaches the end of shaft 3, and the bell crank lever 15 is activated to operate the brake system 17.

The bushes 8, 9 mounted on shaft 6 are preferably a self lubricating material such as nylon, and the slide surface between the sleeve 7 and shaft 3 may be coated with self-lubricating material.

20 Variations to the trailer coupling may be made within the scope of the invention particularly with regard to the arrangement of shock absorbers and lost motion devices. The use of e.g. nylon bushes as proposed avoids the effects of corrosion on the sliding surface and the

-6 effects of jerky motion, which are likely where high friction coefficient materials are used.

Claims

! CLAI1\IS

1. A trailer coupling comprising a first part fixed relatively to a towed vehicle, - and a second part relatively moveable to said first part for connection to a towing vehicle, one of said parts providing an outer member and the other of said parts providing an inner member which is slidably received within said outer member, wherein said outer member comprises a sleeve which receives at one end an end portion of a member connected to either said first part or said second part, and at its other end a similar fitting connected to an operating i.. lever for the brake device of said towed vehicle.

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2. A coupling according to claim 1, wherein the members which are at each end of the sleeve each comprise respectively a low friction bush having end slots which allow radial compression of the bush, and having a detent formed on the outer face of the bush for engagement with an internal groove in the sleeve so Mr.. -; that one such bush can be pushed into each end of the sleeve and snap fitted .. into the groove to prevent pulling-out of the bushes.

3. a coupling according to claim 2, wherein each bush acts as a seat or receptor , for the end of a shaft, one lever being connected to the first part, and the other . to the brake operating lever.

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4. a coupling according to claim 2 or 3 wherein the sleeve is an outwardly smooth steel tube which is arranged to be slidable within an outer tube connected to the second part.

5. a trailer coupling substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.