GB2249759A - Trailer having a raisable ramp for vehicle inspection - Google Patents

Abstract

A trailer has a carrier (13) suitable for carrying a road vehicle and which carrier can be raised in parallel relation with a chassis (10) of the trailer to facilitate access to the underside of the vehicle on the carrier. Four stabilisers (24, 25) support the trailer when a vehicle is to be inspected on the carrier (13), the stabilisers compensating for any unevenness of the ground. <IMAGE>

Description

Title: Trailer Description of Invention The present invention relates to a trailer for trailing behind a motor road vehicle.

According to the invention, there is provided a trailer comprising a wheeled chassis, a carrier suitable for carrying a motor road vehicle on the trailer, lifting means for raising the carrier relative to the chassis and a plurality of retractable stabilisers carried on the chassis and being adapted to be extended to the ground.

The trailer preferably includes driving means for extending the stabilisers to respective different distances from the chassis. In this way, the trailer is adapted for use on uneven ground.

Preferably, the trailer further comprises control means responsive to resistance to continued extension of all of the stabilisers, the control means being adapted to prevent operation of the lifting means to raise the carrier relative to the chassis unless a predetermined resistance to continued extension of the stabilisers has been established. The provision of such control means substantially avoids the risk of the lifting means being operated before all of the stabilisers have been firmly engaged with the ground. The predetermined resistance may correspond to the reaction to the aggregate force exerted on the ground by the stabilisers when the weight of the trailer is transmitted to the ground by the stabilisers alone.

The control means preferably includes attitude-sensing means associated with the chassis for preventing operation of the lifting means to raise the carrier relative to the chassis unless the attitude of the chassis is substantially horizontal.

An example of trailer embodying the invention will now be described, with reference to the accompanying drawings, wherein: FIGURE 1 shows diagrammatically a side elevation of the trailer and FIGURE 2 is a diagrammatic representation of an hydraulic circuit of the trailer.

The trailer illustrated in Figure 1 comprises a chassis 10 having a pair of road wheels, one of which is shown at 11. The particular example illustrated has a single pair of road wheels but it will be understood that the trailer may comprise additional pairs of road wheels, arranged in a known manner. At a front of the chassis, there is a draw bar 12 having a coupling for coupling the trailer with a towing vehicle. The coupling is preferably a known coupling, for example a socket suitable to fit on a 50 mm tow ball. In the example illustrated, the tow bar is rigid with the chassis 10. A jockey wheel and an overrun braking mechanism may be provided.

A carrier 13 is mounted on the chassis 10 for upward and downward movement relative to the chassis. The carrier is suitable for carrying a road vehicle, for example a passenger car. The carrier has a substantially flat upwardly facing surface on which road wheels of a car can rest. Adjacent to opposite, rear corners of the chassis 10, there are provided on the chassis respective columns, one of which is shown at 14. A corresponding pair of columns is provided at the front of the chassis, one of these being shown at 15.

The columns are adapted to guide the carrier for upward and downward movement relative to the chassis and to support the carrier in an elevated position. For this purpose, the columns and the carrier are provided with respective cooperating formations which facilitate retaining the carrier at a selected height on the columns. In the example illustrated, these formations comprise respective apertures which can be mutually aligned to receive a retaining pin, one pin per column, for retaining the carrier at a selected height on the columns. The retaining pins are preferably formed to ensure that they cannot be withdrawn when they bear the load of the carrier and transmit that load to the columns.For this purpose, the retaining pins may be formed with respective shoulders which engage the columns or the carrier adjacent to openings therein when the retaining pins bear the load, the arrangement being such that these shoulders can be moved through the openings only when the carrier is raised slightly relative to the chassis.

At the rear of the chassis 10, there is preferably provided a hinged ramp 16 having a free end which can be lowered to the ground and an opposite end portion which leads onto the carrier 13, when the carrier is in a lowered position relative to the chassis.

Upper end portions of adjacent ones of the columns are connected to each other by rails, three of which are indicated at 34, 35 and 36 in Figure 1.

These rails are at a height substantially above the highest position to which the carrier 13 can be moved, so that the rail between the columns at the front of the chassis and the rail between the columns at the rear of the chassis will prevent a vehicle on the carrier rolling off the carrier either forwards or rearwards, when the carrier is in the raised position. It will be noted that the carrier cannot be raised to the tops of the columns.

The trailer further comprises lifting means for raising the carrier 13 relative to the chassis 10. The lifting means represented in the accompanying drawing comprises four hydraulic rams 17 to 20 disposed in respective ones of the columns on the chassis. Each ram acts between the chassis and the carrier 13.

Each ram may act on the carrier through the intermediary of a cable or other flexible element which runs over a pulley mounted in the column. Alternatively, the pulley may be driven upwards by the ram, one end of the cable being attached to the carrier and the other end being attached to the column or chassis.

This arrangement provides travel of the carrier through a distance which is twice the stroke of the associated ram.

Alternatively, one or more of the cables may be extended from its column to a ram remote from the column. For example, a single ram may operate the lifting means at all four columns. The ram or rams may be single acting or double acting rams. By way of example, there are represented in Figure 2 four single acting rams connected with a pump 31 via a common supply valve 21 and also connected with a reservoir 22 via a common exhaust valve 23.

A further example of suitable lifting means (not illustrated) comprises one or more electric motors instead of the hydraulic rams shown in Figure 2.

The or each electric motor may be drivingly associated with a cable drum on which there is wound a cable or respective cables for transmitting motion to the carrier 13. Alternatively, the columns may contain respective screw jacks which are rotated by associated electric motors. It would also be within the scope of the invention to provide manually driven lifting means, for example comprising screw jacks or drum and cable means for transmitting motion to the carrier.

Preferably, the lifting means is arranged to move the carrier along all of the columns at the same rate so that the lifting means maintains the carrier in parallel relation with the chassis 10.

The trailer further comprises a plurality of stabilisers. In the example illustrated, there are four stabilisers mounted on the chassis 10 adjacent to respective ones of the columns. Two of the stabilisers are shown at 24 and 25 in Figure 1. Each of the stabilisers illustrated comprises a leg 26 which is pivoted on the chassis and has at its free end a foot 27. The stabiliser further comprises an hydraulic ram 28 which acts between the leg 26 and the chassis. By means of the ram 28, the leg 26 can be swung down relative to the chassis or retracted towards the chassis. As shown in Figure 2, the rams incorporated in the stabilisers are preferably double-acting rams.

There is connected in the hydraulic supply line 29 to the rams of the stabilisers a pressure-detecting switch 30 which responds to establishment in the supply line 29 of a pressure exceeding a predetermined threshold value. The output from the switch 30 is applied electrically to control operation of the supply valve 21 so that hydraulic pressure cannot be applied to the rams 17 to 20 until the threshold pressure has been attained in the supply line 29.

Other forms of extendible stabilisers may be substituted for the pivoted legs shown in Figure 1. For example, each stabiliser may comprise a leg which is guided for reciprocation vertically relative to the chassis and an hydraulic ram for extending and retracting the leg. Alternatively, a screw jack or other mechanical device may be provided for extending and retracting each stabiliser.

Where screw jacks are provided, these may be driven by electric motors or manually. In each case, the arrangement is such that the stabilisers can be extended respective different distances from the chassis so that the stabilisers can be engaged firmly with the ground when the chassis is horizontal, even if the ground is sloping or uneven.

With the stabilisers retracted and the carrier 13 in the lowered position illustrated in Figure 1, the trailer can be towed, either empty or with a vehicle supported on the carrier. For loading of a vehicle onto and unloading of a vehicle from the carrier, the ramp 16 is lowered.

When a vehicle on the carrier 13 is to be raised from the chassis 10, the hydraulic pump 31 is operated and the valve 32 is opened to direct hydraulic fluid under pressure to the rams associated with the stabilisers. The stabilisers are thereby extended downwardly from the chassis into engagement with ground.

If a first stabiliser engages the ground before a second stabiliser engages the ground, then movement of the first stabiliser ceases temporarily until the second and each other stabiliser has engaged the ground. If the ground is uneven, this means that one or more stabilisers will be extended further than another stabiliser. When all stabilisers have engaged the ground, the pressure in the supply line 29 will rise as the chassis 10 is raised by extension of the stabilisers together. Raising of the chassis will take up some movement of the suspension of the trailer but will not necessarily raise the wheel 11 from the ground. When the pressure in the supply line 29 exceeds the threshold value, the switch 30 is operated and this causes the valve 32 to close the supply line 29.Operation of the pressure switch 30 also permits or causes the valve 21 to open and admit hydraulic fluid under pressure from the pump to the rams 17 to 20 of the lifting means. The carrier is thereby raised relative to the chassis to the required height. When this height is reached, the valve 21 is closed and retaining pins are inserted into the columns to prevent the carrier descending to the chassis. The exhaust valve 23 may then be opened briefly to permit the carrier to descend slightly and trap the retaining pins.

When the carrier 13 is required to be lowered to the chassis once more, hydraulic fluid is supplied once again from the pump through the valve 21 to the rams 17 to 20 to raise the carrier slightly and thereby free the retaining pins. The valve 21 is closed once more and the retaining pins are withdrawn.

Hydraulic fluid is then permitted to flow from the rams 17 to 20 thereby permitting the carrier to descend relative to the chassis. Hydraulic fluid may be exhausted from the rams 17 to 20 through the valve 23 and this valve may include a restrictor which limits the rate of descent of the carrier.

Once the carrier has returned to its lowered position, the rams associated with the stabilisers may be operated to raise the stabilisers from the ground. An electrical interlock may be provided to ensure that the valve 32 cannot be operated to raise the stabilisers until the carrier is in the lowered position. Additionally or alternatively, locks may be provided for mechanically locking the stabilisers in respective extended positions until the carrier is in the lowered position. Such locks may be operated manually, electrically or hydraulically.

The pump 31 may be driven manually. Additionally or alternatively, there may be provided a power source suitable for driving the pump. This power source may be a battery pack or an internal combustion engine. In a case where the pump 31 is an electric pump, it may be driven from the battery of a towing vehicle. Other sources of power on a towing vehicle may be used to drive the pump 31.

The upwardly facing surface of the carrier 13 on which a vehicle rests preferably forms a pair of rectilinear channels, one along each side of the carrier.

The carrier may be substantially open between the channels. When a vehicle is loaded onto the carrier, the wheels of the vehicle would roll along the channels.

Chocks may be provided in the channels to prevent inadvertent movement of the vehicle.

There is provided on the chassis 10 a platform which is fixed with respect to the chassis and which is suitable for supporting a person inspecting or working on the vehicle when the carrier is in the raised position. This platform is preferably provided by an open work structure, for example a grid. Beneath the grid, there may be provided a floor and a drain in or at a margin of the floor, the floor sloping down to the drain when the chassis 10 is substantially horizontaL Beneath the drain, there may be attached to the floor a releasable container for liquid which drains from the floor.

There may be further provided in the trailer an attitude-sensing means which is mechanically associated with the chassis 10 and which is electrically associated with controls for the hydraulic circuit so that components of the hydraulic circuit cannot be operated unless the chassis is substantially level.

Additionally or alternatively, the electrical circuit may be arranged for controlling operation of the stabilisers in such a manner that the attitude of the chassis is corrected automatically, if it is not substantially horizontal, before the carrier 13 is raised relative to the chassis.

The trailer may further comprise a cover for covering a vehicle on the carrier, when the carrier is in the lowered position. The cover may be or may include a roller shutter. Guides for the roller shutter may be attached to or incorporated in the columns 14 and 15.

The trailer is useful with a vehicle which has broken down or is otherwise in need of repair or other attention. If the vehicle is loaded onto the carrier 13, it can be raised to allow convenient access to the underside of the vehicle. The trailer may incorporate a winch to facilitate drawing of an unpowered vehicle onto the carrier. If the vehicle cannot conveniently be repaired, then it can be transported on the trailer with the carrier in the lowered position.

The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims (12)

1. A trailer for trailing behind a motor road vehicle and comprising a wheeled chassis, a carrier suitable for carrying a motor road vehicle on the trailer, lifting means for raising the carrier relative to the chassis and a plurality of retractable stabilisers carried on the chassis and being adapted to be extended to the ground.

2. A trailer according to Claim 1 wherein the carrier has four corners arranged in a rectangle and the lifting means comprises four pillars arranged on the chassis adjacent to respective corners of the carrier.

3. A trailer according to Claim 2 wherein there are four of said retractable stabilisers, each being mounted on the chassis adjacent to a respective one of said pillars.

4. A trailer according to any preceding claim having driving means for extending the stabilisers to respective different distances from the chassis and control means responsive to resistance to continued extension of all of the stabilisers, the control means being adapted to prevent operation of the lifting means to raise the carrier relative to the chassis unless a predetermined resistance to continued extension of the stabilisers has been established.

5. A trailer according to any preceding claim comprising control means for controlling operation of the lifting means and wherein the control means includes attitude-sensing means associated with the chassis for preventing operation of the lifting means to raise the carrier relative to the chassis unless the attitude of the chassis is substantially horizontal.

6. A trailer according to any preceding claim wherein the lifting means is arranged to maintain a parallel relation between the carrier and the chassis.

7. A trailer according to any preceding claim wherein either the chassis or the carrier has a floor and a drain in or at a margin of the floor and wherein the floor is arranged to slope down to the drain when the chassis is substantially horizontal.

8. A trailer according to any preceding claim wherein the chassis includes an open work platform.

9. A trailer according to any preceding claim wherein the lifting means is manually operable.

10. A trailer according to any preceding claim including a power source for operating the lifting means.

11. A trailer substantially as hereindescribed with reference to the accompanying drawing.

12. Any novel feature or novel combination of features disclosed herein or in the accompanying drawing.