GB2073709A

GB2073709A - Vehicle skip lifting device

Info

Publication number: GB2073709A
Application number: GB8110731A
Authority: GB
Original assignee: Webb R A
Current assignee: Webb R A
Priority date: 1980-04-10
Filing date: 1981-04-06
Publication date: 1981-10-21
Also published as: GB2073709B

Abstract

A safe skip loader which employs only one pair of hydraulic actuators has a base frame 10, a pair of loading arms 12 pivotally connected to the base frame and a pair of supporting legs 18 pivotally connected to the base frame by parallel links 19 and 20. A double acting hydraulic ram 23 links each loding arm 12 and its associated leg assembly. With the leg held extended (Fig. 1) by a detent pin 22 operation of the actuators lifts a skip 26 on and off the vehicle. With the pin 22 holding the leg 18 retracted (Fig. 2) operation of the actuators 23 to move the arm to an outboard position is not possible. <IMAGE>

Description

SPECIFICATION Lifting device This invention relates to a device for lifting an object on and off a vehicle, especially a wheeled vehicle, and more particularly, but not exclusively, concerns a device for lifting a skip on and off a flat, load-carrying surface of a commercial, wheeled, road vehicle.

It is known to provide lorries with a pair of lifting arms mounted for pivotal movement about an axis at the rear of the vehicle for lifting a skip between a lower position in which the skip rests on the ground immediately behind the vehicle and an upper position in which it rests on a loadcarrying surface of the vehicle, the movement of each arm being effected by a double-acting, oil hydraulic, piston and cylinder actuator. The weight of a laden skip suspended behind the rear of the vehicle can impose a severe load on the structural members of the vehicle so a pair of ground contacting supporting legs mounted on the vehicle and moved by additional actuators is provided. A safety device is necessary to ensure that, during lifting of a skip, the legs are in their extended positions for ground contact.The cost of providing the additional actuators and safety devices is substantial. The known lorries are heavy and are purpose built. The are correspondingly expensive and inflexible.

According to the present invention there is provided a device for lifting an object between a transport position on a transport surface on a vehicle and a loading position in which the object rests on a loading surface off the vehicle, the device comprising: (a) a base frame, (b) a lifting arm connected at one end thereof to the base frame for pivotal movement of the arm relative to the base frame through an arc between inboard and outboard positions relative to the vehicle for lifting said object between said loading position and said transport position by suspension of the object from the free end of the arm, (c) a supporting leg assembly mounted to the base frame for movement of a leg of the leg assembly between an extended position in which it contacts said loading surface at least during lifting of said object onto and off said loading surface and a retracted position in which it does not interfere with useful movement of the vehicle, (d) detent means to hold the leg assembly against movement from the extended position towards the retracted position, and (e) an actuator so pivotally connected at one end thereof to the arm and at the other end thereof to the leg assembly that it is operable, with the arm in said inboard position, to move the leg assembly between said retracted position and said extended position and is further operable, with said leg assembly held by the detent in its extended position, to move the arm through the arc between the inboard and outboard positions to lift the object on and off the vehicle as required.

The invention has particular application to lightweight vehicles, especially those for which an HGV licence is not required for driving, which it is not economic to build exclusively for one special purpose.

The base frame may be demountable from the vehicle, a part of the vehicle, or may comprise some parts which are demountable and some part of the vehicle. Use of a demountable base frame allows the lifting device to be used with ordinary, multi-purpose goods vehicles such as lightweight commercial vehicles, because no special mountings on the vehicle for the legs are necessary. Undue stress on the vehicle may be avoided by ensuring that, with the leg assembly held in its retracted position, the lifting arm cannot be moved through its arc into the outboard position.

The actuator will normally be an oil hydraulic, piston and cylinder device. However, it is contemplated that the necessary movement could be provided by devices employing a rack and pinion or screw threaded components.

Usually the device will comprise a demountable base assembly having one or more lateral structural members connecting a pair of base frames, in order to provide a pair of lifting arms, one at each rear corner of the vehicle.

For a better understanding of the invention.and to show how the same may be carried into effect, reference will now be made to the accompanying drawings, in which: Fig. 1 is a side elevation showing the device mounted on a vehicle and disposed for lifting a skip from a lower position into an upper position on the load-carrying surface of the vehicle; and Fig. 2 is a side elevation of the vehicle and lifting device in the position it has attained after lifting the skip into its upper position.

The skip loading device shown in the drawings comprises a pair of lifting devices (of which only the offside device is visible in the drawings) each of which has a base frame 10 constructed of steel plate and hollow section steel member and mounted rigidly to a vehicle 11. The frame includes "L"shaped portions which abut the rear edge of the load bed 1 7 of the vehicle. A lifting arm 12 is pivotally mounted at a fixed end 13 thereof to the base frame 1 0 for movement through an arc between an outboard position as shown in Fig. 1 and an inboard position as shown in Fig. 2. At the free end 14 of the lifting arm 12 is pivotally mounted a lifting trunnion 1 5 from which depend a pair of lifting chains 1 6. The base frame 10 extends forwardly to the front of the load bed 1 7 of the vehicle.Not shown in the drawing is a spacer bar connecting the front ends of the base frames 10 and a further spacer bar connecting the lifting arms 1 2 adjacent their pivotal connection with the base frames 10. This much of the device will be familiar to those skilled in the art.

A supporting leg 1 8 is connected to each base frame 10 by an upper link 1 9 and a lower link 20 of a parallel linkage which permits the leg 1 8 to move between an extended position as shown in Fig. 1 and a retracted position as shown in Fig. 2.

The upper and lower links 19 and 20 move within a pair of side plates of the leg assembly 10 of which only the outer member 21 of the off side pair of plates is visible in the drawings. A detent pin 22 for the leg 1 8 is carried in aligned holes in the pair of plates 21, so the pin extends across the locus of pivotal movement of the upper link 1 9.

With the leg 1 8 in its extended position in the pin 22 projects through a further aligned hole (not visible) provided in the upper link 19. With the leg 1 8 in its retracted position, the pin 22 extends behind the link 1 9 to prevent movement of the leg 1 8 to the extended position.

Two double-acting, oil hydraulic, piston and cylinder actuators 23 are provided, one for each lifting arm 12, each pivotally connected at one end thereof to the lifting arm, 12 and at its other end to a point on the upper link 1 9 intermediate the pivotal connections at each end of the link. In other embodiments, the actuator 23 is connected to the leg 1 8 or the pivotal connection at the top of the leg 1 8 but this provides no lever ratio increase in the amount of movement of the leg 1 8 compared with that of the actuator 23.

Twin flexible oil hydraulic hoses 24 and 25 provide paths for flow of hydraulic oil to and from the actuator 23.

Not shown in the drawings but familiar to skilled readers are the means for providing a flow of hydraulic oil and the valve by which flow of oil to and from the actuators 23 is controlled. For a light vehicle such as that shown in the photographs, it will generally be convenient to provide a known power pack comprising a pump for hydraulic oil driven by an electric motor which draws electrical power from the engine of the vehicle only when a flow of oil to the actuators 23 is required. Alternatively, the pump can be driven from the engine by a known shaft power take-off.

The actuators 23 can be connected in parallel with one another in the oil circuit, and a conventional pressure relief valve to protect the components in the hydraulic circuit against excessive oil pressures provided.

In use of the device, the lifting arms 12 initially occupy their inboard rest position, and the supporting legs 18 occupy their retracted position, as shown in Fig. 2. For picking up a skip 26, the vehicle 1 1 is driven into a position relative to that of the skip such as is shown in Fig. 1 , the detent pins 22 are removed and the actuators 23 are operated to extend their length and, the lifting arms 1 2 being at the forward end of their pivotal arc of movement, the supporting legs 18 pivot on their parallel linkages into their extended positions as shown in Fig. 1. The pins 22 are then replaced in the holes in the plate 21, passing through the links 1 9 to retain the legs 1 8 in their extended positions and the actuators 23 are actuated to reduce their lengths.This causes the lifting arms 12 to move through their arc of movement to attain the position shown in Fig. 1. It will be apparent that the position of the lifting arms 12 shown in Fig. 1 is very close to an extreme outboard position, since the length of the actuators 23 is almost at a minimum. It will also be apparent that, if the legs were to remain in their retracted positions, the arms could not be moved all the way to the outboard position of Fig. 1 because the actuators 23 would reach their minimum length soon after actuation and initial movement of the arms out of their inboard position.

The free ends of the chain 1 6 are attached to the skip 26 in a manner known perse. Operation of the actuators 23 (to increase their length) causes the arms 1 2 to execute their arc of movement and lift the skip 26 from its loading position (Fig. 1) to its transport position on the load-carrying surface of the vehicle shown in Fig.

2. It will be appreciated that the supporting legs 18 bear at least part of the weight of the skip 26 during this lifting operation and thereby relieve stresses to which the vehicle would otherwise be subject.

With the weight of the skip 26 borne by the load-carrying surface 1 7 of the vehicle 11, and off the arms 12, the pins 22 are removed and the actuators 23 once more operated to bring the legs 1 8 into their retracted positions, the pins 22 being then re-inserted to prevent unintended dropping of the legs 18.

From the above description, it will be apparent to skilled readers how the skip may be lifted by the device from its transport position to its unload position for unloading from the vehicle.

The actuators 23 are of conventional construction, in which decreases of lengths are brought about by pressure of hydraulic oil on an annular shoulder of the piston, while increases of lengths are brought about by oil pressure on an entire end face of the piston. Thus the actuators 23 are able to exert greater forces when they are in compressive stress than when they are in tension. Lifting devices according to the invention can be constructed so as to complement this feature by providing that the angle between the longitudinal axis of each lifting arm 12 and that of its associated actuator 23 is greater when the skips are being lifted out of the transport position (when the actuators are on tension) than when the skips are being lifted out of their loading positions on the ground behind the vehicle (when the actuators are under compression).

It may be convenient to arrange that, with the vehicle not loaded, the supporting legs 1 8 terminate just above the ground surface when in their extended position. This enables the vehicle to be manoeuvered while the lifting arms 12 are in their outboard position, permitting the vehicle to be accurately positioned relative to the skip to be loaded. The legs 1 8 are constituted by telescopic leg members slidable on one another, so that a suitable leg length can be defined to suit any particular one of a range of vehicles.

The skip 26 may be provided with lugs and the loading device with chains engageable with the lugs to restrain movement of the adjacent edge of the skip (in the drawing the rear, bottom edge of the skip) away from a position between the two base frames 10 of the device, for tipping the skip, in a manner known per se, by movement of the lifting arms towards the outboard position with the chains 1 6 in tension. See for example, Fig. 3 of the photographs accompanying Patent Application No. 8011843.

While the lifting device has been illustrated and particularly described for use with a skip and light goods vehicles, it will be apparent that other applications are possible. In particular, a lifting device having a single arm, leg and actuator, and provided with a lifting frame attached to the free end of the arm for lifting a specific object which co-operates with the frame on and off a vehicle may be useful in a particular application such as lifting a wheelchair on and off a light vehicle.

It will be apparent that lifting over the side of a vehicle (or even the front) is feasible. In particular, given a sufficiently heavy goods vehicle and a sufficiently light skip, it will be possible to lift skips on to a goods vehicle from one side thereof. This is of particular importance where there is limited space for the vehicle to manoeuvre, for example, in an urban environment or congested building site. With special regard to this last application, it is contemplated that a heavy goods vehicle may be provided with two or more of the lifting devices of the invention arranged along one side thereof.

With a demountable skip-loading device according to the invention, as shown in the drawings, removal of the device from a vehicle, storage of the device and fitting to a vehicle may be readily accomplished as follows. With the device and a skip in the positions shown in Fig. 1 the means securing the frame 10 to the vehicle are released and the hydraulic oil supply to the rams 23 actuated to cause the chains 16 to tighten and the frame 10 to pivot around the foot of the leg 1 8, lifting the part of the frame at the front of the load bed 17 clear of the bed 17. The vehicle may then be driven forwardly to clear the lifting device which balances on its two legs 18, prevented from tilting forward by the weight of the skip 26. This sequence of steps is reversed for attachment of a "parked" device to a vehicle.

Claims

1. A device for lifting an object between a transport position on a transport surface on a vehicle and a loading position in which the object rests on a loading surface of the vehicle, the device comprising: (a) a base frame, (b) a lifting arm connected at one end thereof to the base frame for pivotal movement of the arm relative to the base frame through an arc between inboard and outboard positions relative to the vehicle for lifting said object between said loading position and said transport position by suspension of the object from the free end of the arm, (c) a supporting leg assembly mounted to the base frame for movement of a leg of the leg assembly between an extended position in which it contacts said loading surface at least during lifting of said object onto and off said loading surface and a retracted position in which it does not interfere with useful movement of the vehicle, (d) detent means to hold the leg assembly against movement from the extended position towards the retracted position, and (e) an actuator so pivotally connected at one end thereof to the arm and at the other end thereof to the leg assembly that it is operable, with the arm in said inboard position, to move the leg assembly between said retracted position and said extended position and is further operable, with said leg assembly held by the detent in its extended position, to move the arm through the arc between the inboard and outboard positions to lift the object on and off the vehicle as required.

2. A device as claimed in claim 1 wherein the base frame is demountable from the vehicle.

3. A device as claimed in claim 1 or 2 wherein the actuator is incapable of operation to move the arm through said arc to the outboard position while the leg remains in said retracted position.

4. A device as claimed in claim 1,2 or 3 wherein said actuator is a double-acting, piston and cylinder, fluid actuator.

5. A device as claimed in claim 4 wherein said actuator is an oil hydraulic device.

6. A device as claimed in any one of the preceding claims including means to control a supply of power to said actuator.

7. A device as claimed in claim 6 including a source of power for said actuator.

8. A device as claimed in any one of the preceding claims wherein the leg of the leg assembly is connected to the base frame by a pair of parallel links comprising an upper link and a lower link both connected pivotally to the leg and the base frame and spaced from one another vertically along the leg and base frame in use of the device.

9. A device as claimed in any one of the preceding claims wherein the actuator is connected to the leg of the leg assembly.

10. A device as claimed in claim 8 wherein the actuator is connected to the leg assembly at the pivotal connection between the leg and the upper link.

11. A device as claimed in claim 8 wherein the actuator is connected to the upper link of the leg assembly at a point intermediate the pivotal connections at the ends of the upper link.

12. A device as claimed in any one of the preceding claims wherein the leg is arranged so as to be vertical or substantially vertical in use.

13. A device as claimed in any one of the preceding claims wherein the leg has at least first and second leg members which are movable relative to one another and can be secured in any one of a plurality of relative positions thereby to provide a plurality of different leg lengths.

14. A device as claimed in claim 13 wherein said first and second leg members are slidably engageable with one another.

15. A device as claimed in claim 14 wherein said leg members are telescopic.

16. A device as claimed in any one of the preceding claims wherein the detent means comprises a pin which engages with at least one hole in the base frame and an aligned hole in the leg assembly when the leg is in the extended position.

17. A device as claimed in claim 1 6 as dependent upon claim

1 8 wherein the hole in the leg assembly is in the upper link thereof.

1 8. A device as claimed in claim 17 wherein the base frame comprises a pair of surfaces between which the upper link is received with the leg in the extended position, each surface of said pair defining a said hole for the pin.

19. A device as claimed in any one of the preceding claims wherein the detent means can be employed to retain the leg in its retracted position.

20. A device as claimed in claim 19 as dependent upon claim 1 6 wherein engagement of said pin with said base frame holes, with the leg in its retracted position, prevents movement of the leg towards its extended position.

21. A skip-loading device for a commercial vehicle, comprising a pair of devices as claimed in any one of the preceding claims.

22. A device as claimed in claim 21 comprising a demountable base assembly constituted by the base frames of said pair and at least one lateral structural member connecting said base frames, the device further comprising a lateral stay connecting the free ends of the lifting arms of the pair.

23. A device as claimed in claim 21 or 22 wherein the base frames of the pair have an "L"shaped portion adapted to abut an edge of a load bed of the vehicle.

24. A device as claimed in claim 21,22 or 23 further comprising at least one retaining member to restrain movement of an adjacent edge of a skip away from a position between the pair of base frames, whereby movement of the arms from the inboard to the outboard position causes the skip to rotate about said skip edge and tend to tip the contents of the skip out of the skip and off the vehicle.

25. A device as claimed in claim 24 wherein said at least one retaining member is a pair of chains having, at their free ends, connectors to engage with corresponding connection points on said skip edge, and are secured at their other ends to a stay member connecting either the base frames of the pair of lifting devices or the lifting arms adjacent to their pivotal connections with the base frames.

26. A lorry provided with two or more devices as claimed in any one of claims 21 to 25, arranged to lift skips over a side of the lorry.

27. A commercial vehicle provided with a single device as claimed in any one of claims 21 to 25.

28. A vehicle as claimed in claim 27, being sufficiently light in weight that it may legally be driven by a person who is unqualified to drive a heavy goods vehicle, the device being arranged to load skips over the rear end of the vehicle.

29. A lifting device substantially as hereinbefore described with reference to, and as shown in the accompanying drawings.