IE950175A1 - A lifting mechanism - Google Patents

Abstract

A forklift mechanism (1) has a frame (2) which is fixed in a position by connection to a plate on a road vehicle at a coupling (3). The forklift mast (4) is tilted by a ram (8) to the different operative tilt positions. Wheels (20) are connected to the frame (2) by an independent suspension (21). Vertical position of the wheels (20) is controlled by hydraulic rams (24) so that they may be urged downwardly to distribute the load of the forklift between the wheels 20 and the wheels of the road vehicle to dynamically provide the correct balance and traction. This is extremely important for control and safety purposes.

Description

The invention relates to a lifting mechanism, and more particularly to such a mechanism for attachment to the front of a road vehicle.

It has long been appreciated that there are considerable 5 benefits to be gained if a lifting mechanism attached to the front of a road vehicle could operate effectively.

For example, a tractive unit which hauls a large load would be able to disconnect from the trailer on arrival at the depot and then the driver could use the lifting mechanism attached to the front of the tractive unit for removal of the goods from the trailer and deposit them into the depot or warehouse. Major practical advantages could be achieved by doing this. For example, very often the load will arrive outside of normal working hours for depot personnel and thus, use of a lifting mechanism attached to the front of the road vehicle would allow the load to be delivered into the warehouse in such situations. Very often, the fact that the goods are unloaded before the start of work the following morning provides a significant time advantage in delivery of the goods .

Attempts have been made at development of such a lifting mechanism. For example, in British Patent Specification No. GB-A-940844 (Page), a forklift mechanism is described which is attached to the front of an articulated lorry tractive unit. This arrangement, however, suffers from the major disadvantage that it is necessary for the tractive unit to incorporate a ballast weight positioned near the back axle of the tractive unit. Further, in the United States Patent Specification No. 4139111 (Fritz), there is shown a forklift mechanism attached to the front of an automotive vehicle. It appears that a ballast-oru.': : < t’\i j·· u si <,nCN 28 AN<' ra,lE 23 JNL No weight at the rear of this vehicle would also be required to prevent instability problems which would arise when a load is lifted. United States Patent Specification No. 4177001 (Blackwood) also describes a forklift attachment for highway vehicles. This mechanism includes a pair of castor wheels attached to a rectangular box frame on the forklift attachment. The frame is movable with respect to the vehicle in a wheeled carriage arrangement so that irregularities in the surface are followed to some extent.

Such forklift mechanisms have not gained widespread usage and it appears that there are several reasons for this. The primary reason would appear to be the fact that the forklift mechanism has been treated as an individual item with little regard for the consequences of it being attached to the front of a road vehicle, the road vehicle not being designed for such use. In particular, it appears that there would be significant control and balance problems, particularly for heavy loads on the forklift tines. Such problems can lead to instability of the road vehicle. Another problem is lack of traction of the drive wheels, and also lack of control for steering. The prior art mechanisms also appear to be quite cumbersome for attachment to the road vehicle and for storage, etc.

The invention is directed towards providing a lifting mechanism having features which allow it to be attached to the front of a road vehicle and to operate in a manner whereby there is excellent stability and control, almost as if the road vehicle were designed for use with the mechanism.

Another object is that the mechanism be easy to handle and store when not in use. A still further object is that the mechanism be reliable in operation.

According to the invention, there is provided a lifting mechanism comprising:a fixed frame having means for securing to a road vehicle at the front thereof; a lifting device and associated drive means connected to the fixed frame; ground-engaging wheels connected to the frame by a suspension which allows relative vertical movement between the wheels and the fixed frame; and balance and traction control means comprising means for causing vertical movement of the wheels to positions whereby a load is distributed for desired vehicle and mechanism balance and traction.

In one embodiment, the wheels are vertically movable independently of the lifting device.

Preferably, each wheel or wheel assembly has an independent suspension.

Ideally, the control means comprises a user operating means for mounting inside a road vehicle.

In another embodiment, the control means comprises an hydraulic drive means .

In a further embodiment, the hydraulic drive means comprises an hydraulic ram connected to each suspension.

Preferably, each hydraulic ram is double acting.

In another embodiment, the mechanism further comprises a gas accumulator connected to an hydraulic circuit to provide independent suspension.

In a further embodiment, each suspension includes a moving parallelogram arrangement.

In one embodiment, the lifting device comprises a forklift mast and tines.

Preferably, the tines are pivotable to a vertical transport position.

According to another aspect, the invention provides a road vehicle trailer comprising a pair of apertures for reception of forklift mechanism tines and a pair of lower skid bars positioned with respect to the apertures for support of a mast of the forklift mechanism.

In this aspect, the trailer preferably further comprises a pair of support bars slidably mounted to project rearwardly and positioned with respect to the apertures for support of the forklift mechanism.

The invention will be more clearly understood from the following description of some embodiments thereof, given by way of example only with reference to the accompanying drawings, in which:Fig. 1 is a perspective view from above of a lifting mechanism, namely, a forklift mechanism of the invention; Fig. 2 is a diagrammatic front view of the mechanism; Fig. 3 is a diagrammatic rear view of part of the mechanism showing a suspension arrangement in more detail; Figs. 4(a), 4(b) and 4(c) are diagrammatic side views 5 showing the mechanism, in use; Fig. 5(a) is a perspective view of a coupling of the mechanism; Figs. 5(b) and 5(c) are diagrammatic, cross-sectional views of part of the coupling showing the manner in which a locking bolt is operated; Fig. 6(a) is a perspective view showing the mechanism coupling connected to a road vehicle plate; Fig. 6(b) is a diagrammatic front view showing the plate in position on the road vehicle; Fig. 6(c) is a perspective view showing the plate in more detail; Figs. 7(a) and 7(b) are diagrammatic front and side views respectively showing the mechanism in operation; Figs. 8(a) and 8(b) are diagrammatic rear and side views respectively showing the manner in which the mechanism is transported; and Fig. 9 is a diagrammatic side view showing operation of the mechanism after removal from the transport position.

Referring to the drawings, there is shown a lifting mechanism of the invention, namely, a forklift mechanism 1. The mechanism 1 comprises a fixed frame 2 having a coupling 3 for attachment to a road vehicle. The coupling 3 and the frame 2 are therefore to be regarded as being fixed in position when considering operation of the mechanism 1. The mechanism 1 further comprises a triplex forklift mast 4 to which a pair of tines 5 are connected via a tine support 6. The tines 5 are pivotally connected to the support 6 at pivot connectors 7 so that they may pivot to a vertical inoperative position. The connectors 7 are mounted behind the tines for additional strength. The mechanism 1 also comprises a tilt hydraulic ram 8 mounted between the frame 2 and the mast 4 for tilting of the mast 4 between the various rearward and forward tilt positions which are required for operation. This tilting motion is about a pivot connector 9 between the mast 4 and the frame 2.

The mechanism 1 also comprises two pairs of wheels 20 which are connected by an independent moving parallelogram suspension 21 to the frame 2. The suspension 21 comprises a front suspension arm 22 and a rear suspension arm 23 which are pivotally connected to a support hub for the wheels 20 to provide the moving parallelogram effect illustrated most clearly in Fig. 3 whereby the wheels 20 always remain vertically aligned, irrespective of their vertical position.

A very important aspect of the mechanism 1 is that it comprises a control means which controls the vertical position of the wheels 20 so that traction and balance of a vehicle/mechanism combination is controlled. In this embodiment, the control means comprises a two-way hydraulic ram 24 for each pair of wheels 20. As shown in Fig. 3, each hydraulic ram 24 is connected to an hydraulic circuit 25 which is illustrated in diagrammatic form only. There is a Nitrogen gas accumulator 26 connected in a downward supply line 27 for each ram 24. There is also an upward supply line 28 connected to the circuit 25. Hydraulic pressure through the downward supply line 27 keeps the wheels 20 at the particular vertical position in use, while at the same time, the gas accumulator 26 provides for independent suspension so that irregularities in the ground do not cause instability.

To help understand the construction, the independent suspension comprises the arms 22 and 23 and the gas accumulator 26. The rams 24 should be regarded as a separate control means which set the wheel positions and therefore pressures, although the gas accumulators do, of course, act via the rams 24.

The coupling 3 is illustrated in Figs. 5(a), 5(b) and 5(c) and comprises a coupling base plate 40 welded to a socket member 41 which has side members which are inclined upwardly and inwardly. There is also a pair of lock pin assemblies 42, each of which comprises a handle 43, a pin 44 and a biassing spring 45. As shown in Figs. 6(a), 6(b) and 6(c), a coupling plate 50 is secured to the front of the vehicle cab and is anchored in position by a support frame 51. The shape of the coupling plate 50 corresponds in shape to that of the socket 41 so that when the mechanism 1 is lowered downwardly, the socket 41 surrounds the plate 50 until the weight of the mechanism 1 holds it in place. The locking assembly 42 is then operated by the handle 43 so that the pin engages, as shown in Fig. 5(b), through apertures in the socket 41, the coupling plate 50 and the base plate 40.

Operation of the mechanism 1 is illustrated in Figs. 4(a), 4(b) and 4(c) whereby the tilt ram 8 causes the mast 4 to tilt to a 4° front tilt for engagement with a pallet 30 back to a 6° rear tilt for transport of the pallet.

In Figs. 7(a) and 7(b), the mechanism 1 is shown attached to the front of the road vehicle, in this embodiment, a tractor unit of an articulated lorry. In Fig. 7(a), the wheels 20 are lifted well clear of the ground and the tines 5 are in an upper inoperative position. The allows the mechanism 1 to be transported for short journeys and around a warehouse when not in use. For use, the wheels 20 are lowered by the rams 24, as shown in Fig. 7(b). These actions are controlled by the driver of the cab by connections, not shown, of the hydraulic circuit 25 into the cab of the tractor unit 52. It is essential that the driver control these actions so that the wheels 24 are urged downwardly under hydraulic pressure so that the distribution of the load is taken to the maximum extent by the mechanism 1, while at the same time ensuring that the traction of the front wheels of the tractor unit 52 is not reduced to the extent where control problems would arise. This pressure is controlled dynamically by the driver so that at all times, the downward pressure on the wheels 20 reflects the load being carried by the mechanism 1 so that there is a correct load distribution and good driving and steering control. This aspect is extremely important as it allows the mechanism and the tractor unit 52 to act in unison, although the tractor unit was not designed for such a use. Indeed, it has been found that loads of up to 2 to 3 tonnes can be carried without causing any instability and in a manner whereby any competent lorry driver is capable of controlling the mechanism adequately with little or no training.

Referring now to Figs. 8 and 9, the manner in which the mechanism 1 may be transported for longer journeys is illustrated. The tractor unit drives to the rear of its trailer 55 and moves the mechanism 1 forward so that the tines 5 engage in apertures 56 in the rear crash bar of the trailer 55. Slidable support arms 57 are pulled out, as indicated by the arrow A, so that they project rearwardly and support the mechanism 1 by engagement underneath the suspensions 21. The mechanism 1 is then secured in place by use of chains, not shown. The arms 57 are not necessarily left in position during transport, however, they may be used for disconnection as they provide a support for raising and lowering the mechanism by operation of the rams 24. Skid bars 58 are secured to the rear of the trailer 55. If the tines are raised, the mast is moved downward in relation to them for engagement onto the skid bars 58.

As shown in Fig. 9, the mechanism 1 may be easily removed by releasing the chains and causing downward movement of the frame 2 and the mast 4 with respect to the tines 5 so that the coupling 3 engages the plate 50 at the front of the tractor unit 52 as shown in Figs. 5 and 6. The mechanism 1 may then be operated, as shown in Fig. 9, to remove pallets from the trailer 55.

It will be appreciated that the invention provides a forklift mechanism which may be very easily secured to the front of a road vehicle such as a tractor unit. The mechanism 1 may then be operated in a manner whereby there is comprehensive load and steering control whereby the mechanism 1 effectively becomes part of the road vehicle. This is extremely important in providing for ease of use and safety. Further, the mechanism 1 may be easily transported for either short-haul or long-haul in a simple and convenient manner. It would, therefore, be very convenient for trucking companies to provide convenience in situations where a load arrives out of working hours, or if a forklift truck is not available for any other reason.

It will further be appreciated that the invention is extremely simple and indeed the comprehensive balance and traction control which is provided is achieved by use of simple parts of an hydraulic circuit. Because relatively simple and conventional parts may be used to achieve these features, it is envisaged that the mechanism 1 will be extremely reliable in use and also simple to manufacture.

The invention is not limited to the embodiments hereinbefore described. For example, independent suspension may be provided by any other suitable manner and it is not essential that gas accumulators be fitted. It is also envisaged that the mechanism need not be a forklift mechanism and may indeed comprise a different type of lifting arrangement such as a loading shovel or bucket, a platform or a crane assembly, depending on the desired application. Further, the fixed frame has been described as an item secured to a plate on the road vehicle, however, it could be implemented as the plate on the vehicle, in which case the lifting device and wheels could move together.

Claims (14)

1. A lifting mechanism comprising :a fixed frame having means for securing to a road vehicle at the front thereof; a lifting device and associated drive means connected to the fixed frame; ground-engaging wheels connected to the frame by a suspension which allows relative vertical movement between the wheels and the fixed frame; and balance and traction control means comprising means for causing vertical movement of the wheels to positions whereby a load is distributed for desired vehicle and mechanism balance and traction.

2. A mechanism as claimed in claim 1, wherein the wheels are vertically movable independently of the lifting device.

3. A mechanism as claimed in claim 2, wherein each wheel or wheel assembly has an independent suspension.

4. A mechanism as claimed in any of claims 1 or 2, wherein the control means comprises a user operating means for mounting inside a road vehicle.

5. A mechanism as claimed in any preceding claim, wherein the control means comprises an hydraulic drive means.

6. A mechanism as claimed in claim 4, wherein the hydraulic drive means comprises an hydraulic ram connected to each suspension.

7. A mechanism as claimed in claim 6, wherein each hydraulic ram is double acting.

8. A mechanism as claimed in any of claims 5 to 7, further comprising a gas accumulator connected to an hydraulic circuit to provide independent suspension.

9. A mechanism as claimed in any preceding claim, wherein each suspension includes a moving parallelogram arrangement.

10. A mechanism as claimed in any preceding claim, wherein the lifting device comprises a forklift mast and tines .

11. A mechanism as claimed in claim 10, wherein the tines are pivotable to a vertical transport position.

12. A mechanism substantially as hereinbefore described, with reference to and as illustrated in the accompanying drawings .

13. A road vehicle trailer comprising a pair of apertures for reception of forklift mechanism tines and a pair of lower skid bars positioned with respect to the apertures for support of a mast of the forklift mechanism.

14. A trailer as claimed in claim 13 further comprising a pair of support bars slidably mounted to project rearwardly and positioned with respect to the apertures for support of the forklift mechanism.