GB2262721A - Wheel assembly - Google Patents

Abstract

A wheel assembly 11-21 for a vehicle 1 comprises a plurality of mountings 57, 59, each comprising at least two wheels 23-29 mounted on a rocker arm 31. Yokes 63 are provided for supporting the rocker arms to allow independent rocking movement of each mounting. <IMAGE>

Description

WHEEL ASSEMBLY The present invention relates to wheel assemblies for vehicles, especially but not exclusively suited to use in large trailers, wagons and the like.

Large wagons or trailers are often used for conveying cargo from docks or in large warehouse installations.

Previously, it was quite common for such cargo to be loaded onto rail wagons but nowadays, these are much less cost effective in this application. The economics of the operation mean that space is at a premium and there is a necessity for a quick turn-round time.

Therefore, the modern tendency is to use large wagons or trailers which are self propelled or towed as part of articulated vehicles to convey the cargo by road.

Typically, such wagons weigh in the order of 120 tons to 360 tons and may have a large number of individual wheels, for example from 24 to 72. Such wheels often have to bear an individual load of about 5 tons each.

This causes difficulty in designing suitable suspension steering systems and those used hitherto have a number of drawbacks in their reliability and performance.

We have now devised a new form of wheel assembly which is superior to those previously used in such applications. Thus, according to the present invention we provide a wheel assembly for a vehicle, the assembly comprising a plurality of mountings each comprising at least two wheels mounted on a rocker arm, the assembly further comprising respective yokes supporting the rocker arms and so allowing independent rocking movement of each mounting.

Preferably, each yoke is provided with a roller or ball thrust-bearing. This permits it to swivel within an arc of up to about 72".

It is also preferred that each yoke, and hence each mounting is provided with its own hydraulic-suspension jack. Advantageously, this hydraulic system operates at relatively low pressure for enhanced durability.

Preferably also, the mountings are organised into groups, for example 4 or 8 groups. The mountings in each group are then operable together to raise or lower the vehicle, for example to compensate for uneven ground, wind gusts etc.

It is also preferred that each group is operable under computer control (i.e. using a programmable logic controller (PLC) ) which controls solenoid hydraulic valves maintained from hydraulic fluid reservoirs by means of pumps.

Such a system may be constructed so that displacement of hydraulic fluid from one cylinder causes the fluid to be transferred to the other cylinders in the group. This has the advantage that when one mounting encounters a depression or bump in the road surface, rocking of the vehicle is reduced and individual wheel loadings are kept as close to one another as possible.

The computer controlled solenoid valves may be provided with pressure release valves to keep carriage warping forces in check. Preferably also, a small fluid reservoir is provided in each group to minimise hydraulic-knock forces.

Height sensors and inclinometers may be provided on the wagon to detect changes in height and angle of inclinations. The signals emitted by these sensors are then provided to the PLC which thereby updates the relevant control parameters.

The computer may be programmed to check whether relevant data should be displayed to the driver and/or, appropriate control action to be undertaken. In that case, relevant instructions are automatically provided to the PLC to control the relevant hydraulic solenoid valves, hydraulic pumps etc.

Advantageously, each mounting group is independently steered by means of a power screw through a novel sliding-rotating link arm having an inner tube and an outer tube machined to close tolerances. This link arm may be connected via a ball joint to a crab which is driven by the power screw. The power screw in turn is then driven by a geared servo motor, coupled to the computer by means of relays or any other suitable means which will be apparent to those skilled in the art.

Another preferred feature is provided by a signal generator attached to the screw. This may consist of a disk, for example of plastics material, provided with small magnets and an associated detector. Thus, each turn of the screw will give rise to an electrical pulse from the detector. The pulse signal is provided to the PLC which counts the pulses and when these reach a predetermined number, the motor is deactivated.

The computer may be programmed to calculate the horizontal angle of each mounting, storing the last value of each as the assembly turns through its arc of movement. It is possible to calculate this to within an accuracy of better than 1/10 .

The PLC may also be programmed to correlate the number of pulses from the signal generator with a desired angle of turn. Thus, rotational movement of each mounting can be executed until the number of pulses indicates that the required angle of turn has been executed. This can be done to an accuracy of within 1/308.

Such a control system when used with wheel assemblies according to the present invention minimises friction between the tyres and road surface, so reducing wear.

This is especially important for use on the reinforced concrete slabs which are commonly used in wharfs.

Wheel assemblies in accordance with the present invention may be used on a wide variety of vehicles, for example both on towed wagons (of articulated trucks) and on wagons with their own integral drive. The hydraulic control system may be coupled to all or some of the mountings, according to the particular requirements of the vehicle in question.

It is also convenient to provide suitable displays to aid the driver. For example, a desired angle of turn (+ or -) may be pre-set by means of a dial on the control panel. Pressing a button will then allow the computer to take over and execute the desired angular movement.

It is also possible to provide sufficient dials to enable sequential execution of the series of angular movements, for example two or more.

When the wheel assembly of the present invention is to be used in a wagon which is self-propelled (ie contains its own drive unit as opposed to being pulled as an articulated unit by a separately powered trailer cab unit), then it is preferred that the drive power should be transmitted by separate single drive wheels.

These single drive wheels preferably have hydraulic suspension controlled by the PLC. Preferably, they also have a high precision steering system using a motorised steering worm and telescopic lever arm/steering arm, again controlled by the PLC.

The single drive wheels preferably also have hydraulic drive motors for compactness with forward-backward valves that are controlled by the PLC. Alternatively, gear electric motors, 2-3 motors per wheel, can be fitted if considered desirable.

Such drive wheels can be fitted with direction sensitive (clockwise and counter-clockwise) rotation sensors that will continuously update the PLC with angular revolution of each wheel allowing calculation of the distance of movement for each wheel (on an X-Y plane).

Preferably, single drive wheels are fitted closer to the centre of the wagon for the major drive wheels. Thus, for arc-steering, the angles of turning will be less than the four corner wheel-pairs, resulting in less flexing of the high pressure hydraulic hoses.

However, some single drive wheels may also be fitted to the front and rear ends of the wagon to give better wagon turning characteristics. The power pack for propelling (not for steering or swivelling) the single drive wheels may be on-wagon, or else off-wagon, mounted on a trailer unit for serving more than one wagon if desired.

It is also desirable to provide a dedicated computer screen to display the rotation, revolution and movement of each drive wheel. It is further desirable to have for every ten wagons, wheels to provide two drive wheels so that traction will be adequate without excessive pressure on the drive wheels e.g. for a wagon having 24 pair wheels, it is desirable to have eight single drive wheels. Within reasonable bounds of costs and complexity, it is also desirable to have as many wheels (pairs and singles) as possible to reduce damage to roads, other structures, wharfs etc.

It is also advantageous to design the wagon to be able to withstand a wide range of loads and moments, e. g.

caused by mounting a heavy harbour crane. These loads and moments are taken by the load bearing twin wheels units. This will allow the design of the suspension system of the drive wheels to have a greater spring effect by fitting larger heavy duty valved accumulators that can be also controlled by the PLC.

The present invention will now be described in more detail as illustrated by a preferred embodiment and with reference to the accompanying drawings in which: Figure 1 shows in side elevation, a wagon incorporating wheel assemblies according to the present invention; Figure 2 shows the wagon illustrated in Figure 1, in plan view; Figure 3 shows a mounting being a section along the line III - III shown in Figure 2, seen in the direction of the arrows; Figure 4 is a detailed enlarged plan view of the mounting depicted in Figure 3, showing the steerable angle; Figure 5 is a front view of the mounting depicted in Figure 4, showing the steering screw; Figure 6 is a front elevation of the mounting depicted in Figures 4 and 5, showing the wheel assembly steering mechanism;; Figure 7 is a part-sectioned, part-side view of the wheel assembly depicted in Figures 4-6, showing detail of the steering linkage; Figure 8 is a front view of the steering linkage shown in Figure 7; and Figure 9 is a side view of steering linkage shown in Figure 8.

Referring to Figures 1 and 2 together, a wagon 1 comprises a chassis 3. The chassis comprises a central portion 5 and two end portions 7, 9 supported on wheel assemblies 11, 13, 15 and 17, 19, 21 etc.

Each assembly comprises respective pairs of wheels 23, 25 and 27, 29 etc, each pair being mounted on a respective rocker arm 31.

The chassis comprises four wheel beams 33, 35, 37, 39 and a turret support structure 41 on which can be mounted a turret 43. Four outriggers 45, 47 etc terminate in ground pads 49, 51 etc for anchoring and stabilising the wagon during stationery loading.

Respective tow points 53, 55 are provided at either end of the wagon.

The wheel pairs and their respective beams together each form a mounting 57, 59 etc. Each wheel is provided with a cushion tyre 60 etc. The mountings are themselves joined in pairs by respective beams 61 etc.

Referring now also to Figures 3-6, the rocker arm of each mounting is supported on a respective yoke 63 etc.

Each yoke is connected to a respective hydraulic suspension cylinder 65, supported by the underside 67 of the chassis.

Wheel pairs in each mounting are steerable together via the shaft 69 connecting the yoke to the respective hydraulic cylinders. This is effected by means of screw crab 71 connecting each respective shaft to a screw 73 in a housing 75.

Each screw also interconnects the paired mountings associated with the respective beams 61. Referring now to Figures 7-9, each screw 73 is operable by means of a linkage 79. This linkage comprises an outer tube arm 81 and an inner tube 83 slidable within the outer arm. The inner tube 83 is provided with an abutment 85 and is connected to a ball joint 87. This ball joint is connected to a further screw crab 89., supported on a support beam 91. The ball joint is coupled to a further screw 93 in a housing 95. The screw is connected via a thrust block 97, a shaft thrust bearing 99 and a front bearing 101, to a toothed wheel 103.

A chain or belt drive 105 operatively connects the toothed wheel 103 to a further toothed wheel 107. The latter is connected via a bearing 109 to an AC motor 111 operable under the direction of a PLC. A signal generator 113 is associated with the motor and steering transmission mechanisms. The construction and operation of the signal generator is substantially as hereinbefore described. Pulses emitted from the motor correlate the amount of turning of the motor shaft and therefore, the angle through which the wheels are steered.

Claims (30)

1. A wheel assembly for a vehicle, the assembly comprising a plurality of mountings each comprising at least two wheels mounted on a rocker arm, the assembly further comprising respective yokes supporting the rocker arms and so allowing independent rocking movement of each mounting.

2. An assembly according to claim 1, wherein each yoke is provided with a thrust-bearing.

3. An assembly according to either preceding claim, wherein each yoke is provided with its own respective hydraulic-suspension jack.

4. An assembly according to any preceding claim, wherein the mountings are organised into groups.

5. An assembly according to claim 4, wherein the mountings are organised into 4 or 8 groups.

6. An assembly according to claim 4 or claim 5, wherein the mountings in each group are operable together to raise or lower the vehicle.

7. An assembly according to any of claims 4 to 6, wherein each group is operable by a computer control unit which functions to control solenoid hydraulic valves maintained from hydraulic fluid reservoirs by means of pumps.

8. An assembly according to claim 7, wherein displacement of hydraulic fluid from a first cylinder causes the fluid to be transferred to other cylinders in the group.

9. An assembly according to claim 7 or claim 8, wherein solenoid hydraulic valves are provided with pressure release valves to keep carriage warping forces in check.

10. An assembly according to any of claims 7-9, wherein a fluid reservoir is provided in each group to minimise hydraulic-knock forces.

11. An assembly according to any of claims 7-10, wherein height sensors and inclinometers are provided for detecting changes in height and angle of inclinations and for communicating the data to the computer control unit.

12. An assembly according to any of claims 4-11, wherein each group is independently steerable by means of a power screw through a sliding-rotating link arm having an inner tube and an outer tube.

13. An assembly according to claim 12, wherein the link arm is connected via a ball joint to a crab which is arranged to be driven by the power screw.

14. An assembly according to claim 13, wherein the power screw is arranged to be driven by a geared servo motor, coupled to the computer control unit.

15. An assembly according to claim 13 or claim 14, wherein a signal generator is attached to the power screw.

16. An assembly according to claim 15, wherein the signal generator comprises a disk provided with magnets, and an associated detector.

17. An assembly according to claim 15 or claim 16, wherein an output of the signal generator is connected to the computer control unit for counting pulses from the signal generator so that when the pulses reach a predetermined number, the motor is deactivated.

18. An assembly according to claim 17, wherein the computer control unit is programmed to correlate the number of pulses from the signal generator with a desired angle of turn, so that rotational movement of each mounting can be executed until the number of pulses indicates that the required angle of turn has been executed.

19. An assembly according to any of claims 7 to 17, wherein the computer control unit is programmed to calculate the horizontal angle of each mounting, storing the last value of each as the assembly turns through its arc of movement.

20. A wagon without integral drive, the wagon comprising an assembly according to any preceding claim.

21. A wagon with its own integral drive the wagon comprising an assembly according to any of claim 1-19.

22. A wagon according to claim 21, wherein drive power is arranged to be transmitted by separate single drive wheels.

23. A wagon according to claim 22, wherein the drive wheels have hydraulic suspension arranged controlled by the computer control unit.

24. A wagon according to claim 22 or claim 23, wherein the drive wheels have a steering system using a motorised steering worm and telescopic lever arm/steering arm, controllable by the computer control unit.

25. A wagon according to any of claims 22-24, wherein the drive wheels have hydraulic drive motors with forward-backward valves that are controlled by the computer control unit.

26. A wagon according to any of claims 22-25, wherein the drive wheels are fitted with direction sensitive rotation sensors for continuously updating the computer control unit with angular revolution of each wheel, for calculating the distance of movement for each wheel.

27. A wagon according to any of claims 22-26, wherein the drive wheels are fitted closer to the centre of the wagon for the major drive wheels so that for arc-steering, the angles of turning will be less than the four corner wheel-pairs.

28. A wagon according to any of claims 22-27, wherein single drive wheels are also fitted to the front and rear ends of the wagon.

29. A wheel assembly for a vehicle, the wheel assembly being substantially as hereinbefore defined with reference to the accompanying drawings.

30. A wagon substantially as hereinbefore described with reference to the accompanying drawings.