GB2337731A

GB2337731A - Trailer Assembly

Info

Publication number: GB2337731A
Application number: GB9811212A
Authority: GB
Inventors: John Neenan Deeming
Original assignee: OVERLANDER TRAILERS Ltd
Current assignee: OVERLANDER TRAILERS Ltd
Priority date: 1998-05-27
Filing date: 1998-05-27
Publication date: 1999-12-01
Anticipated expiration: 2018-05-27
Also published as: GB2337731B; GB9811212D0

Abstract

A trailer assembly comprises a trailer chassis and a plurality of pairs of wheels (17) arranged as a forward pair and one or more rearward pairs for supporting the chassis and any load thereon. Each pair of wheels is supported on a suspension system which includes a container (3, 7, 11) for a pressurised gas. The trailer assembly includes means (15) for releasing the gas solely from the forward pair of wheels such that the forward pair of wheels remains in contact with a ground surface but carries no weight of the trailer chassis and any load thereon.

Description

1 2337731 TRAILER ASSEMBLY This invention relates to a trailer assembly

which is adapted to be towed by a prime mover and which is adapted to carry one or more containers of conventional dimensions.

Trailer assemblies are well known in forms which are adapted to carry a range of standard containers (such as one or two twenty foot containers, one thirty foot container or one forty foot container) or in which a standard container can be moved longitudinally of the trailer. Trailers of the former type are generally known as extendable skeletal trailers or sliding bottom frame trailers, while trailers of the second type are generally known as sliding top frame trailers.

In the case of extending skeletal trailers, the trailer can be extended and retracted in the longitudinal direction of the trailer in order to accommodate a range of standard containers, while in the case of sliding top frame trailers, the position of a container on the trailer can be adjusted longitudinally of the trailer, for example to facilitate loading and unloading of the container (in which case the container is moved rearwardly on the trailer) while permitting the centre of gravity of the trailer load to be adjusted forwardly for travel.

The problem with such trailers is that under certain circumstances the centre of gravity of the load can be to the rear of the centre of support of the wheels of the trailer, with the result that the trailer tends to lift the rear of the prime mover. This can, for example, render the prime mover difficult to start or render it difficult for the trailer to be extended or retracted.

It is conventional for such trailers to incorporate a plurality of pairs of wheels, with two or three pairs of wheels being provided. Previously, it has been common practice to overcome the problems referred to above by providing means for lifting the forward pair of wheels clear of the ground, with the result that the trailer is supported by the remaining pair, or two pairs, of wheels. The effect of raising the forward pair of wheels is to move the centre of support for the trailer rearwardly.

The disadvantages of raising the forward pair of wheels clear of the ground are the complexity and cost of the mechanism for lifting the pair of wheels, or in practice of lifting one of the suspension points of each of the wheels, and the fact that in some jurisdictions such liftable wheels affect the manner in which the trailer is assessed for compliance with legal requirements.

It is therefore an object of the present invention to provide a trailer assembly which overcomes the drawbacks of lifting wheels in a simple and economical manner.

According to the present invention there is provided a trailer assembly comprising a trailer chassis and a plurality of pairs of wheels arranged as a forward pair and one or more rearward pairs for supporting the chassis and any load thereon, each pair of wheels being supported on a suspension system which includes a container for a pressurised gas, the trailer assembly including means for releasing the gas solely from the forward pair of wheels such that the forward pair of wheels remains in contact with a ground surface but carries no weight of the trailer chassis and any load thereon.

The trailer assembly may also include means for applying brakes of the wheels of the trailer assembly when the suspension system of the forward pair of wheels is depressurised.

The chassis may comprise two portions which are movable relative to each other in the longitudinal direction of the trailer. Locking pins may be provided for locking the two portions in one of a number of alternative positions.

coupling means may be provided for disengageably supplying pressurised air alternatively to the braking system and to /I- 4 the means for releasing gas. The means for releasing gas may comprise a valve such as a pilot valve, especially a 312 pilot valve.

For a better understanding of the present invention and to show more clearly how it may be carried into effect reference will now be made, by way of example, to the accompanying diagrammatic illustration which shows one embodiment of part of a trailer assembly according to the present invention.

Trailer assemblies of the extendable skeletal type and of the sliding top frame type are well known in themselves and will not be described in detail herein.

Such trailer assemblies all include a trailer chassis for supporting a load in the form of one or more conventional containers and a plurality of pairs of wheels 17 (generally two or three pairs) disposed towards the rear of the trailer for supporting the chassis and any load. The wheels are provided with braking mechanisms, conventionally operated by compressed air, and with suspension systems, again conventionally incorporating containers for pressurised air.

The figure is a diagrammatic illustration of a three axle trailer incorporating a forward axle 1 supported by forward air bags 3, a mid axle 5 supported by mid air bags 7 and a rear axle 9 supported by rear air bags 11. Pressurised air is supplied to brakes (not shown) for the wheels 17 by way of a conventional coupling (not shown) and also to the air bags 3, 7, 11 to maintain the air pressure therein. When the source of pressurised air is uncoupled, the drop in pressure causes the brakes to be applied, but the air bags generally remain inflated.

Particularly in the case of an extendable skeletal trailer, in which the chassis comprises two portions which are slidable relative to each other in a longitudinal direction of the trailer, transverse locking pins (not shown) are provided to lock the two portions of the chassis in one of a number of alternative positions in order to adapt the trailer for a particular container configuration to be carried.

Previously, it has been conventional practice to provide operating means, such as a push button, on a side of the chassis for lifting and lowering the forward wheels. However, in the illustrated embodiment venting of the air bags 3 is controlled by an independent pressurised air system in which a coupling 13 of the type for receiving pressurised air to the brake system is provided for supplying pressurised air for venting the pressurised air from the air bags 3. To effect venting of the air bags 3, the pressurised air system provides pressurised air to a 3/2 pilot valve 15 connected between the forward pair of l- wheels and the rearward two pairs of wheels. In the absence of air pressure, the air bags 3, 7, 11 are able to communicate with each other as illustrated, but when air pressure is applied to the pilot of the valve 15, the pilot slides to isolate the air bags 7 and 11 of the rearward two pairs of wheels (which remain pressurised) and to allow the forward pair of air bags 3 to vent to atmosphere and therefore to depressurise. Simultaneously, the locking pins are disengaged.

When the soUrce of pressurised air is uncoupled from the coupling 13 the locking pins are automatically inserted into corresponding apertures in the chassis to lock the two portions relative to each other and the drop in air pressure at the pilot valve closes the vent to atmosphere and reconnects the forward air bags 3 with the rearward air bags 7 and 11.

When the source of pressurised air is reconnected to the brake line, the brakes are released and pressurised air is supplied to completely reinflate the air bags 3, 7 and 11.

Claims

1. A trailer assembly comprising a trailer chassis and a plurality of pairs of wheels arranged as a forward pair and one or more rearward pairs for supporting the chassis and any load thereon, each pair of wheels being supported on a suspension system which includes a container for a pressurised gas, the trailer assembly including means for releasing the gas solely from the forward pair of wheels such that the forward pair of wheels remains in contact with a ground surface but carries no weight of the trailer chassis and any load thereon.

2. A trailer assembly as claimed in claim 1 and including means f or applying brakes of the wheels of the trailer assembly when the suspension system of the forward pair of wheels is depressurised.

3. A trailer assembly as claimed in claim 1 or 2, wherein the chassis comprises two portions which are movable relative to each other in the longitudinal direction of the trailer.

4. A trailer assembly as claimed in claim 3, wherein locking pins are provided for locking the two portions in one of a number of alternative positions.

r 0 c 0 c c, c 5. A trailer assembly as claimed in any preceding claim, wherein coupling means are provided for disengageably supplying pressurised air alternatively to the braking system and to the means for releasing gas.

5. A trailer assembly as claimed in any preceding claim, wherein the means for releasing gas comprises a valve.

6. A trailer assembly as claimed in claim 5, wherein the valve comprises a pilot valve.

7. A trailer assembly as claimed in claim 6, wherein the pilot valve comprises a 3/2 pilot valve.

8. A semi-trailer assembly substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.

8. A trailer assembly substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.

i 1 i 1 i 41,1 Amendments to the claims have been filed as follows 1. A semi-trailer assembly comprising a trailer chassis and a plurality of pairs of wheels arranged as a f orward pair and one or more rearward pairs for supporting the chassis and any load thereon, each pair of wheels being supported on a suspension system which includes a container for a pressurised gas, the semi-trailer assembly including:

means for releasing the gas solely from the gas container for the forward pair of wheels such that the forward pair of wheels remains in contact with a ground surface but carries no weight of the trailer chassis and any load thereon; and 15 means for applying brakes of the wheels of the trailer assembly in response to depressurisation of the suspension system of the forward pair of wheels. 20 2. A semi-trailer assembly as claimed in claim 1, wherein the chassis comprises two portions which are movable relative to each other in the longitudinal direction of the trailer. 25 3. A semi-trailer assembly as claimed in claim 2, wherein locking pins are provided for locking the two portions in one of a number of alternative positions.

4. A semi-trailer assembly as claimed in any preceding claim, wherein coupling means are provided for disengageably supplying pressurised air alternatively to the braking system and to the means for releasing gas.

5. A semi-trailer assembly as claimed in any preceding claim, wherein the means for releasing gas comprises a valve.

6. A semi-trailer assembly as claimed in claim 5, wherein the valve comprises a pilot valve.

c C. c 0 0 0 c 9 0 7. A semi-trailer assembly as claimed in claim 6, wherein the pilot valve comprises a 3/2 pilot valve.