GB2392425A

GB2392425A - Peripheral contact tandem drive system

Info

Publication number: GB2392425A
Application number: GB0318007A
Authority: GB
Inventors: Roger William Dee
Original assignee: Individual
Current assignee: Individual
Priority date: 2002-07-31
Filing date: 2003-07-31
Publication date: 2004-03-03
Also published as: GB0217672D0; GB0318007D0

Abstract

In a drive system, one side of a machine comprises two ground engaging wheels 1,2 and a third wheel 3 having a periphery 4 which frictionally contacts the periphery 5 of the front wheel 1 and the periphery 6 of the rear wheel 2. One of the wheels 1,2,3 is driven by a motor. The system is suitable for providing four wheel drive for a civil engineering or mechanical handling machine, such as a dumper truck or powered barrow. The third wheel 3 is mounted to a chassis 7 by a bracket 8 and may be an idler wheel which is selectively engaged by inflation of a tyre. The opposite side of the machine has two ground engaging wheels and preferably a similar third wheel arrangement, steering being achieved by disengaging the drive and by braking on one side of the machine.

Description

POWER DRIVE

This invention relates to a multi-wheel drive mechanism and, in the preferred embodiment, provides a simple and robust multi-wheel drive mechanism suitable for use on relatively low cost vehicles, for example small civil engineering and mechanical handling machines.

Traditionally, small civil engineering and mechanical handling machines (for example powered barrows) have been mounted on four wheels, with two ofthe wheels at the same end of the machine driven by an engine via a belt or chain drive. Such arrangements are simple to implement, low cost, and robust. Whilst it is well recognised that advantages could be derived from driving all four wheels, it has generally been felt that the additional complexity, and cost, of utilising four wheel drive is not justified in this type of machine.

Accordingly, the need exists for a simple, robust and low cost system for implementation of four wheel drive for small civil engineering and load handling machines. In accordance with the present invention a load handling machine comprises: a first pair of ground engaging wheels located adjacent one end of the machine; a second pair of ground engaging wheels located adjacent the other end ofthe machine; at least one third wheel the periphery of which is in frictional driving engagement with the periphery of one ofthe first pair of wheels and one ofthe second pair wheels; and a motor for rotating one of the three wheels which are in frictional driving engagement with each other whereby the remaining wheels are driven by way of the frictional driving engagement.

In a particularly preferred embodiment of the invention two third wheels are provided, each in frictional driving engagement with a respective one of the first

wheels and a respective one of the second wheels.

In a particularly simple embodiment of the invention the first wheels are secured to a common axle for rotation therewith and the motor drives the axle in order to rotate the first wheels. The third wheels are rotated by virtue of the frictional driving engagement between the third wheels and the first wheel and the second wheels are driven by virtue of the frictional driving engagement between the second wheels and the third wheels. Accordingly, all four ground engaging wheels are driven.

In an alternative arrangement the drive means may drive the third wheels which in turn drive the first wheels and the second wheels by virtue of the frictional driving engagement. The arrangement may be such that the third wheel is optionally engaged or disengaged in its driving contact with one or both of the first and second wheels whereby engagement ofthe four wheel drive feature is selectable by an operator ofthe machine. In the preferred embodiment, however, the third wheel is fixed in an operative position in which it is in driving engagement with both the first and second wheels. The invention will be better understood from the following description of a

preferred embodiment, given by way of example only, reference being had to the accompanying drawings wherein: Figure 1 illustrates schematically the wheels of a conventional small civil engineering or load carrying machine, Figure 2 is a view corresponding to Figure 1 but showing implementation of a preferred embodiment of the present invention.

Referring firstly to Figure 1, it is common to provide small civil engineering machines (for example small dumper trucks or powered barrows) with a pair of ground engaging driving wheels 1 and a pair of ground engaging non-driving wheels 2. The driving wheels 1 may be driven by any suitable means, for example by belt or chain drive from a small internal combustion engine or by an electric motor or respective electric motors driving the first wheels on opposite sides of the chassis.

Although it is well recognised that it would in many cases be desirable to drive both the first wheels 1 and the second wheels 2, the cost of implementing a four wheel drive arrangement has previously been considered to be unacceptable for the type of machine in question.

I have now devised the arrangement shown in Figure 2 in which four wheel drive is provided by means of an additional third wheel 3 the periphery 4 of which is in frictional driving engagement with the periphery 5 of the first wheel 1 and the periphery 6 of the second wheel 2. Preferably two third wheels 3 are provided - one on each side of the chassis so that a driving connection is provided between the first wheel 1 and the second wheel 2 on both sides of the vehicle.

In the preferred arrangement the third wheel 3 is mounted to the chassis 7 of the vehicle by a bracket 8 and is in permanent driving engagement with the wheels 1 and 2. It is to be understood, however, that an alternative arrangement exists within the scope of the invention whereby the wheel 3 is movably mounted and is brought into its use configuration only when required. In general, however, for the most simple construction the wheel 3 will be rigidly mounted to the chassis 7 by the bracket 8.

In order to provide the necessary frictional driving engagement between the respective wheels at least one of the wheels 1, 2 and 3 is provided with an inflatable tyre. Typically, wheels 1 and 2 may be provided with inflatable tyres and wheel 3 will be provided with a suitable peripheral coating of rubber like material, and may be inflatable or non-inflatable. Preferably, the third wheel will have an inflatable tyre. In order to assemble the invention the or each inflatable tyre is first deflated, the third wheel is then positioned and the bracket 8 secured to the chassis 7. The inflatable tyre or tyres are then reinflated to provide a positive grip between the respective lyres.

It has been found that the arrangement described above provides an effective four wheel drive system for simple civil engineering and mechanical handling machine. The existing drive arrangements whereby the wheels at the front or rear of the machine are driven can be maintained, and drive transmitted to the other ground engaging wheels by means ofthe third wheels 3. It is to be noted, however, that within

the scope ofthe present invention drive may be applied to the third wheel 3 which will then provide the necessary frictional drive to the first wheel I and the second wheel 2.

Also, although the invention has been described in the context of a four wheeled machine, it should be appreciated that it may be applicable to machines having more than four wheels. in the case of six wheel machine, for example, a central driven wheel may be provided on each side ofthe chassis and a pair ofthird wheels provided to transmit drive from that central driven wheel to front and rear wheels ofthe chassis.

All such arrangements are within the scope of the present invention.

In use, the operator can steer the machine by raising two ofthe wheels clear of the ground and rotating the body on the remaining ground contacting wheels.

Preferably, the wheels which are not directly driven will be raised from the ground and a differential will be provided to assist turning of the body on the wheels which are driven. However, in an alternative embodiment of the invention a skid-steer arrangement may be provided whereby steering is effected by disconnecting drive from one side of the machine and, if necessary, braking the ground engaging wheels on that side of the machine. With a skid-steer arrangement the wheels on the side of the machine opposite to those which have been braked will continue to be driven resulting in rotation of the machine towards the braked side. Such a wheel skid-steer arrangement provides an extremely economical alternative to the chain drive or hydraulic drive systems conventionally used on four wheel drive skid-steer machines.

Claims

s CLAIMS

1. A civil engineering or mechanical handling machine comprises: a first pair of ground engaging wheels located adjacent one end of the machine; a second pair of ground engaging wheels located adjacent the other end of the machine; at least one third wheel the periphery of which is in frictional driving engagement with the periphery of one of the first pair of wheels and one of the second pair wheels; and a motor for rotating one ofthe three wheels which are in frictional driving engagement with each other whereby the remaining wheels are rotatably driven by way of the frictional driving engagement.

2. A machine according to claim 1 wherein two third wheels are provided, each in frictional driving engagement with a respective one of the first wheels and a respective one of the second wheels.

3. A machine according to claim 1 or claim 2 wherein the first wheels are secured to a common axle for rotation therewith and the motor drives the axle in order to rotate the first wheels.

4. A machine according to claim 1 or claim 2 wherein the motor drives the third wheels which in turn drive the first wheels and the second wheels by virtue of the frictional driving engagement.

5. A machine according to any preceding claim wherein the third wheel is optionally engaged or disengaged in its driving contact with one or both of the first and second wheels whereby engagement ofthe four wheel drive feature is selectable by an operator of the machine.

6. A machine according to any of claims 1 to 4 the third wheel is fixed in an operative position in which it is in driving engagement with both the first and second

wheels.

7. A machine according to claim 6 wherein the driving engagement is provided by inflating an inflatable tyre provided on one or more of the wheels.

8. A machine according to any preceding claim wherein the machine is a dumper truck or a powered barrow.

9. A machine according to any preceding claim including means for disengaging drive from the wheels located on one side ofthe machine whilst maintaining drive to the wheels on the other side of the machine to effect steering of the machine.

10. A machine according to claim 9 including means for braking the wheels on one side of the machine whilst the wheels on the other side of the machine continue to be driven.

11. A civil engineering or mechanical handling machine substantially as hereinbefore described with reference to the accompanying drawing.