GB2274265A

GB2274265A - Power drive assembly for attachment to a wheelchair.

Info

Publication number: GB2274265A
Application number: GB9400516A
Authority: GB
Inventors: Richard Craddock Hayes
Original assignee: Individual
Current assignee: Individual
Priority date: 1993-01-13
Filing date: 1994-01-12
Publication date: 1994-07-20
Also published as: GB9400516D0

Abstract

The power drive assembly (13) can be attached to a horizontal or vertical framework member of a folding wheelchair having large or small diameter rear wheels (10). The assembly is fitted between the wheels (10) so as to incline forwardly and upwardly from its point of contact with the ground to its free pivotal attachment to the wheelchair. The power drive assembly (13) includes a wide pneumatically tyred small diameter drive wheel (12) driven from an electric motor (15) through a gearbox (16), control being effected by a switch (17) incorporating a variable potentiometer (18) to control speed. The drive wheel (12) contacts the ground between, and substantially in line with, the point of contact (11) of the wheels (10) to enable the wheelchair to be turned and steered in the normal way. For control by the wheelchair occupant, brakes may be added to the wheelchair and the controls (17, 18) placed within the reach of the wheelchair user. <IMAGE>

Description

POWER DRIVE ASSEMBLY FOR WHEELCHAIR This invention relates to a power drive assembly for a wheelchair.

Most wheelchairs are manually propelled by the occupant or by an attendant. Where the occupant is not severely disabled, large diameter rear wheels are provided on the wheelchair and they have slightly smaller diameter circular hand-wheels keyed for rotation, so as to enable the occupant to propel the chair. Additionally, handles are provided for use by an attendant.

A severely disabled person requires an attendant to propel the wheelchair, and may use a transit chair having small diameter rear wheels. Where possible, however, integral power assistance and steering are provided for the disabled person to operate the wheelchair independently.

Pushing a wheelchair, particularly with an adult occupant can be heavy work and there is a need for an inexpensive and reliable power drive means which can be attached to a standard wheelchair of the large or small wheeled type, to enable it to be propelled more easily by an attendant.

It is an object of the invention to provide a new or improved power drive assembly for attachment to a wheelchair for this purpose.

According to the invention a power drive assembly for a wheelchair comprises power storage means, drive means powered by said power storage means, a ground-engageable drive element, and transmission means operatively connecting the drive element to the drive means, the power drive assembly further comprising mounting means for attachment to the wheelchair, and the arrangement being such that the power drive assembly forms a trailing linkage pivotally mounted on the mounting means with the ground engageable drive element positioned in contact with the ground between, and substantially in line with the points of contact of a rear pair of wheels of the wheelchair and pivotally mounted on the trailing linkage.

Preferably, the trailing linkage forms an angle of approximately 5 degrees with the horizontal, sloping forwardly and upwardly.

The power storage means may comprise a battery.

The drive means may comprise an electric motor.

The transmission means may comprise a gearbox.

The ground-engageable element may comprise a wheel, which is preferably a pneumatically tyred wheel and may be of substantial width compared with the width of the tyres of the wheel chair.

Switch means may be provided on a hand control disposed remotely from the power drive assembly for example on a hand grip of the wheelchair.

The switch means may include velocity control means adapted to change the drive speed of the ground-engageable element. The velocity control means may comprise a variable potentiometer.

The switch means may be positioned so as to be operable by the wheelchair occupant. Alternatively they may be positioned so as to be operable by an attendant.

The mounting means may comprise a telescopic mounting bar adapted to be secured to and demounted from the framework of the wheelchair. It may be adapted to be secured to a pair of upright members at opposed sides of the wheelchair or to a pair of horizontal side members.

The power drive assembly may further comprise brake means selectively operable to brake either or both of the right or left wheels of the rear pair of the wheels of the wheelchair.

The brake means may be operable by the occupant of the wheelchair or alternatively may be operable by an attendant.

The brake means may comprise a pair of brake shoes acting on peripheral regions of the respective rear wheels or may comprise drum brakes mounted centrally of each of the rear wheels.

The invention also provides a wheelchair having a power drive assembly as set out above.

The wheelchair may be a folding wheelchair.

An embodiment of the invention will now be described in more detail by way of example only with reference to the accompanying drawing, which diagrammatically illustrates a wheelchair in side view, having the power drive means of the invention attached.

Referring to the drawing, a wheelchair has a pair of large diameter, slender rear wheels 10 which make contact with the ground at 11. A drive wheel 12 of a power drive assembly generally indicated at 13 is disposed between the rear wheels 10 and makes ground contact in line with them at 11. The drive wheel 12 is of smaller diameter and much greater width than the rear wheels and has a pneumatic tyre.

The power drive assembly also includes a battery 14, which may be of any suitable type, preferably rechargeable. This supplies power to an electric motor 15, which drives the drive wheel 12 via a gearbox 16. The motor has a switch 17 and its controls also incorporate a variable potentiometer 18, enabling the assistant propelling the wheelchair to adjust its speed. The controls may be mounted on the hand grip of the wheelchair. They may include a lever to provide the on-off switch function and a twist control to vary the speed, or both may operate from the lever switch 17 which senses variation in gripping pressure.

The motor and gearbox assembly forms a linkage 19 which is pivotally mounted at its forward end 20 to a frame including a telescopic strut 21 such as a screw-jack, which can be attached to suitable members of most conventional types of wheelchair.

The wheelchair can be provided with brakes for example brake shoes acting on peripheral regions of the respective rear wheels or drum brakes provided on respective brake drums mounted centrally of the rear wheels. In either case the brakes can be manually or power operated and can be connected to a hand control means. This may be a lever or linkage attached to manual brakes or a control button or buttons for power operated brakes.

Where brakes are provided on the wheelchair, it is feasible for the wheelchair occupant to operate both the drive and the brakes. Where no brakes are provided, it would generally speaking not be safe for the occupant to control the power drive assembly.

Because the brakes operate individually on the respective large diameter rear wheels, they may also be used, in conjunction with the power drive assembly, to steer the wheelchair.

It will be appreciated that manually propelled wheelchairs do not normally have separate brakes and therefore a further degree of adaptation of the wheelchair is needed to add these.

However this may be desirable where the wheelchair is primarily intended to be manually propelled by the occupant since this will enable the occupant to use the power drive assembly.

The linkage 19 extends rearwardly and downwardly at an angle of about 5 degrees to the horizontal, to provide a rotational mount 22 for the drive wheel 12.

The drive wheel 12 is therefore freely pivoted on the fore and aft linkage 19 and is not coupled to the wheels 10. Rotation of the drive wheel 12 by the motor tends to produce a reaction force on the linkage 19 because the wheel pivot 22 is positioned below the linkage forward pivot 20 on the telescopic strut 21. The reaction force is such as to tend to lift the weight of the wheelchair. In other words, the geometry of the linkage 19 is such that driving the wheel 12 tends to force itself into engagement with the ground at 11, giving very excellent traction properties.

It will be appreciated that the drive wheel 12 is positioned on the fore and aft centre line of the wheelchair so as to give a forward drive. Means are provided to centralise the thrust line when the telescopic strut 21 is adjusted over its complete range so as to accommodate narrow or wide wheelchairs. If it is desired to turn a corner, the usual manual pressure is exerted on the hand grips 23 to turn the wheelchair to one side. However since the drive wheel is disposed centrally, and has a point of contact in line with the points of contact 11 of the large wheels 10, no scrubbing of the drive wheel tyre tends to occur.

It has been found that, by the use of a telescopic strut 21 to secure the power drive means 13, it can be fitted to virtually all standard types of wheelchair. The potentiometer housing 18 is fitted to the hand grip 23 so that the lever switch 17 is accessible to the attendant to control the movement of the chair.

Claims

1. A power drive assembly for a wheelchair comprising power storage means, drive means powered by said power storage means, a ground engageable drive element, transmission means operatively connecting the drive element to the drive means, and mounting means for attachment to the wheelchair, the arrangement being such that the power drive assembly forms a trailing linkage pivotally mounted on the mounting means with the ground engageable drive element positioned in contact with the ground between, and substantially in line with, the points of contact of a rear pair of wheels of the wheelchair and pivotally mounted on the trailing linkage.

2. An assembly according to claim 1 wherein the trailing linkage forms an angle of approximately 5 degrees with the horizontal sloping forwardly and upwardly.

3. An assembly according to claim 1 or claim 2 wherein the power storage means comprise an electrical battery.

4. An assembly according to any preceding claim wherein the drive means comprise an electric motor.

5. An assembly according to any preceding claim wherein the transmission means comprise a gearbox.

6. An assembly according to any preceding claim wherein the ground engageable element comprises a pneumatically tyred wheel of substantial width compared with the width of the tyres of the wheelchair.

7. An assembly according to any preceding claim wherein the switch means are provided on a hand controlled disposed remotely from the power drive assembly for example on a handgrip of the wheelchair.

8. An assembly according to claim 7 wherein the switch means include velocity control means adapted to change the drive speed of the ground engageable element.

9. An assembly according to claim 8 wherein the velocity control means comprise a variable potentiometer.

10. An assembly according to any one of claims 7-9 wherein the switch means are adapted to be operable by the wheelchair occupant.

11. An assembly according to any one of claims 7-9 wherein the control means are adapted to be operated by an attendant.

12. An assembly according to any preceding claim wherein the mounting means comprise a telescopic mounting bar adapted to be secured to and de-mounted from the framework of the wheelchair.

13. An assembly according to claim 12 wherein the mounting means is adapted to be secured to a pair of upright members and opposed sides of the wheelchair.

14. An assembly according to claim 12 wherein the mounting means is adapted to be secured to a pair of horizontal side members.

15. An assembly according to any preceding claim and additionally comprising brake means selectively operable to brake either or both of the right and left wheels of said rear pair of wheels of the wheelchair.

16. An assembly according to claim 15 wherein the brake means are adapted to be operated by the wheelchair occupant.

17. An assembly according to claim 15 wherein the brake means are adapted to be operated by an attendant.

18. An assembly according to any one of claims 15-17 wherein the brake means comprise brake shoes acting on respective peripheral regions of the rear wheels.

19. An assembly according to any one of claims 15-17 wherein the brake means comprise a brake drum mounted centrally of each of the rear wheels.

20. A wheelchair when fitted with a power drive assembly according to any one of claims 1-19.

21. A wheelchair according to claim 20 comprising a folding wheelchair.

22. A power drive assembly substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

23. A wheelchair substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.