GB2252952A

GB2252952A - Vehicle tail-lift

Info

Publication number: GB2252952A
Application number: GB9121502A
Authority: GB
Inventors: Bryan Lupton
Original assignee: Ross and Bonnyman Engineering Ltd
Current assignee: Ross and Bonnyman Engineering Ltd
Priority date: 1990-10-12
Filing date: 1991-10-10
Publication date: 1992-08-26
Also published as: GB9022246D0; GB9121502D0

Abstract

There is disclosed a vehicle tail-lift arrangement comprising hydraulic means elevating and lowering a platform (12) between vehicle deck level and ground level, said hydraulic means comprising a vertically-extending hydraulic jack (13) each side of the vehicle and lateral level means maintaining equal extension of said jacks. The means can be a rack and pinion (16, 15) or hydraulic series connections or hydraulic volume divider or both. The rack is pref. a chain. <IMAGE>

Description

VEHICLE TAIL-LIFT This invention relates to vehicle tail-lift arrangements.

There are numerous types of tail-lift mechanisms commercially available, which can be incorporated during construction of a vehicle or added to an existing vehicle as a retro-fit. Whilst generally speaking each type of tail-lift can be adapted to the different dimensions of different vehicles, this is not always a ;;tra ghtforward matter.

In one widely used arrangeteent, there bs a 'Zlydraulic ram situated across the '.;G of the vehicle body, at the rear thereof and this operates raising and lowering chains attached to the tail-lift and running in vertical tracks at the sides of the vehicle. This involves extensive structure around the back of the vehicle and is on that account costly. Since transversely-acting mechanism is involved, it is not easily adaptable to different vehicle widths.

The present invention provides a relatively inexpensive arrangement which does not require such elevated structure and which can be readily adapted to different vehicle widths.

The invention comprises a vehicle tail-lift arrangement comprising hydraulic means elevating and lowering a platform between vehicle deck level and ground level, said hydraulic means comprising a vertically-extending hydraulic jack each side of the vehicle and lateral level means maintaining equal extension of said jacks.

Said lateral level means may comprise a rack and pinion arrangement, the pinion extending between racks associated one with each jack. The pinion may LN supported in bearings on the tail-lift or the vehicle tail and the racks move up - and downwardly with the platform. The racks may be of chain.

The lateral level means may also comprise a series connection of said hydraulic jacks and/or a volumetric flow divider directing equal quantities of hydraulic fluid to the jacks.

The arrangement may comprise telescopic sleeve surrounds for the jacks.

The platform may be pivotally supported so as to be deployable between an operative position and a raised, stowed position.

Embodiments of vehicle tail-lift arrangements according to the invention will now be described with reference to the accompanying drawings, in which Figure 1 is a part cut-away perspective view of one arrangement; Figure 2 is a vertical section through a hydraulic jack of the arrangement of Figure 1; Figure 3 is a section on the line IIr- II of Figure 2; Figure 4 is a hydraulic fluid circuit diagram of one embodiment; Figure 5 is a side elevation of an alternative platform in its deployed position; and Figure 6 is a side elevation of the platform of Figure 5 in stowed position.

Figures 1 to 4 illustrate vehicle tail-lift arrangements comprising hydraulic means 11 elevating and lowering a platform 12 between vehicle deck level "D" and ground level "G". The hydraulic means 11 comprise a vertically-extending hyraulic jack 13 each side of the vehicle, and lateral level means 14 maintaining equal extension of said jacks 13.

Figures 1 to 3 illustrate lateral level means 14 comprising a rack and pinion arrangement, the pinion 15 extending between racks 16 associated one with each jack 13. The pinion 15 is a cylinder essentially rigid against twisting extending from side to side of the vehicle supported in bearings 17 on the vehicle tail.

The racks 16 move up - and downwardly with the platform and are conveniently of roller chain, for example, the sort of chain that is used as lifting chain in the conventional tall-lift arrangement referred to above.

The racks 16 are fixed to inner square section sleeves 18 attached to the pistons 13a of the jacks 13, the sleeves 18 telescoping into sleeves 19 enclosing the cylinders 13b of the jacks 13. The ends of the pistons 13a have attachment lugs 21 projecting out of the sleeves 18 and the outer sleeves 19 are slotted at their lower ends to permit the lugs 21 to ride up as the jacks 13 are raised.

The lugs 21 are pivot points for the platform 12 which is deployable between an operative position, illustrated, and a raised, stowed position, as indicated by the arcuate arrow. The pinion 15 is enclosed in a casing 22. A torsion bar 25 is provided to assist closing of the platform 12. Alternatively, the platform may be closed by mechanical means as is normal on conventional lifts.

The rack and pinion arrangement maintains the platform 12 level even though the load on it may be distributed unevenly. Hydraulic fluid from a source 23 fed to the two jacks 13 through a simple T-connector 24 would tend to flow preferentially to the jack that was easiest to extend and thus allow the platform 12 to tilt undesirably.

Fitting a volumetric flow divider in place of the T-connector 24, which ensures an equally metred flow to both jacks, can assist or even replace the rack and pinion arrangement as lateral level means, as can the series connection of the jacks illustrated in Figure 4.

Here, hydraulic fluid displaced from jack 13to) as its piston rises as hydraulic fluid is pumped in below the piston is fed to below the piston of jack 13(2). It must, of course, be arranged that the cross-sectional area of the cylinder of jack 13(1) is equal to the area of the annulus below the piston of jack 13(2).

It will be appreciated that the tail-lift arrangement according to the invention is readily adaptable to different widths of vehicle since, aside from the pinion, which can easily be fabricated to different widths, there is no transversely-acting mechanism.

Figures 5 and 6 illustrate a differentlystowable platform 51 comprising a sliding arrangement 52 of the kind found for example in filing cabinets which holds the platform 51 at the lower end of each jack 13.

The platform 51 is hinged mid-way so that a rearward portion 53 of it can be deployed as a step and can stow as show-l in Figure 6.

Claims

1. A vehicle tail-lift arrangement comprising hydraulic means elevating and lowering a platform between vehicle deck level and ground level, said hydraulic means comprising a vertically-extending hydraulic jack each side of the vehicle and lateral level means maintaining equal extension of said jacks.

2. A vehicle tail-lift arrangement according to claim 1, wherein said lateral level means comprise a rack and pinion arrangement, the pinion extending between racks associated one with each jack.

3. A vehicle tail-lift arrangement according to claim 2, wherein the pinion is supported in bearings on the tail-lift or the vehicle tail and the racks move up - and downwardly with the platform.

4. A vehicle tail-lift arrangement according to claim 2 or claim 3, wherein the racks are of chain.

5. A vehicle tail-lift arrangement according to claim 1, wherein the lateral level means comprise a series connection of said hydraulic jacks and/or a volumetric flow divider directing equal quantities of hydraulic fluid to the jacks.

6. A vehicle tail-lift arrangement according to any one of claims 2-4, wherein the lateral level means additionally comprises a series connection of said hydraulic jacks and/or a volumetric flow divider directing equal quantities of hydraulic fluid to the jacks.

7. A vehicle tail-lift arrangement according to any preceding claim, wherein the arrangement includes telescopic sleeve surrounds for the jacks.

8. x vehicle tail-lift arrangement according t., any preceding claim, wherein the platform is pivotally supported so as to be deployable between an operative position and a raised, stowed position.