GB2275029A

GB2275029A - Wheelchairs

Info

Publication number: GB2275029A
Application number: GB9302802A
Authority: GB
Inventors: Stephen John Rose; Brian Joseph Lewis
Original assignee: Individual
Current assignee: Individual
Priority date: 1993-02-12
Filing date: 1993-02-12
Publication date: 1994-08-17
Anticipated expiration: 2013-02-12
Also published as: GB9302802D0; GB2275029B

Abstract

An electrically powered front wheel drive wheelchair 10 is provided which is equally suitable for both indoor and outdoor use. The chair includes height adjustment means for a seat 14 in the form of a pivotal linkage 24. A spring and damper suspension device is associated with the height adjustment means. Rear swivelling castors 20 employ mountings 22 attached to a frame of the wheelchair at an angle greater than 90 DEG whereby the respective castors are caused to pivot into alignment with the front wheels 18 of the chair to stabilise the steering thereof. <IMAGE>

Description

Improvements in and Relating to Wheelchairs The present invention concerns improvements to wheelchairs, and in particular relates to an electrically powered wheelchair equally suitable for both indoor and outdoor use.

Electrically powered wheelchairs are presently available in various forms. Such wheelchairs have however in the past often been designed specifically for one particular type of use, for example either indoor or outdoor use, with the design requirements of each type of chair frequently precluding its use in any other situation. Outdoor powered wheelchairs are necessarily relatively large and powerful in order to provide satisfactory range, stability and comfort. These chairs are frequently of a rear wheel drive design, which proves to be a disadvantage if the chair has to be used indoors. Conversely indoor chairs, which tend to be more compact, less robust and sometimes of front wheel drive design, are not really suitable for outdoor use.

The invention seeks to mitigate or obviate these and other difficulties.

According to the invention there is provided a powered wheelchair comprising a frame including a part adapted to mount a seat, means associated with the frame permitting adjustment of the height of said part to raise and lower a seat mounted thereon, and a suspension arrangement operatively connected to the height adjustment means.

Preferably the height adjustment means comprises a pivotal linkage. The latter may comprise a parallel motion linkage, or alternatively, a linkage which so operates as to cause the seat to recline as it is lowered by the height adjustment means, for example a linkage comprising a pair of pivotally mounted, spaced parallel arms which differ in length.

The pivotal linkage preferably extends between the seat mounting part of the frame and a base part of the frame. The height adjustment means may be driven by an electric linear actuator or by a variable length strut.

The actuator may be pivotally mounted at one end on the seat mounting part of the frame and at another end on the suspension arrangement.

The wheelchair may incorporate adjustable leg rests, the height adjustment means being operatively connected to means for adjusting the position of the leg rests.

The suspension arrangement preferably comprises a combined spring and damper device.

The present invention also provides a powered wheelchair comprising a frame for mounting a seat thereon and mounting front wheels, a drive arrangement for the front wheels, and rear swivel castors.

Preferably mountings for the castors are provided on the frame so as to lie at an angle greater than 900 thereto, thereby causing each castor to tend to move into alignment with a respective front wheel to stabilise the steering of the wheelchair.

The invention further provides a powered wheelchair as described in the two preceding paragraphs, and incorporating height adjustment means and a suspension arrangement as described in the previous four preceding paragraphs.

The invention yet further provides a powered wheelchair comprising a frame including a part adapted to mount a seat, and means associated with the frame permitting adjustment of the height of said part to raise and lower a seat mounted thereon, the adjustment means comprising a pivotal linkage as hereinbefore described.

The invention will be further described for the purposes of illustration only with reference to the accompanying drawings in which: Fig. 1 is a diagrammatic side view of a wheelchair according to the invention; and Fig. 2 is an enlarged diagrammatic side view of the height adjustment and suspension arrangement.

Referring to Fig. 1, there is shown an electrically powered, front wheel drive wheelchair 10. The frame of the chair comprises an upper part 12 adapted to receive an interchangeable seat 14 and a lower part 16.

The seat 14 may be of any known kind chosen to suit the particular requirements of the wheelchair and the passenger and may, for example, be a seat of the rotating type whereby the passenger may rotate the seat through 900 to face a work bench whilst the wheels are oriented to travel along the length of the bench. The frame part 16 provides for the mounting of front wheels 18, which are driven by a suitable motor and gearbox arrangement (not shown) to provide propulsion and steering for the wheelchair. The chair is controlled by means of an electronic controller which accepts signals from a joystick manipulated by the passenger.

Such an arrangement is known within the art and is not shown or described in further detail here.

The frame part 16 also provides for the mounting of rear swivelling castors 20. Mountings 22 for the castors 20 are so attached to the frame 16 as to project rearwardly slightly as can be seen from Fig. 1. The mountings 22 thus form an angle greater than 90 with the frame part 16. The angle employed causes the weight of the wheelchair and passenger to be utilised to cause the castor 20 to pivot so that it is brought into alignment with a respective front wheel 18. The dynamics of the arrangement are such that the steering of the wheelchair is stabilised, and favours the straight ahead orientation. This reduces the common problem of front wheel drive wheelchairs whereby difficulty is experienced in negotiating a straight narrow pavement.It is noted that the arrangement achieves this effect without significant reduction in the advantageous high degree of slow speed manoeuvrability of front wheel drive chairs.

The latter feature is of course of primary importance when a chair is used in an indoor environment.

The wheelchair 10 incorporates a seat height adjustment and seat suspension arrangement which is best illustrated in Fig. 2. The frame of the wheelchair incorporates a pivotal linkage 24 consisting of two spaced parallel arms 26, 28 which differ in length and are arranged to form a trapezium with associated mountings 30, 32. Each arm 26, 28 is thereby pivotally connected at one end to the frame part 16 and at the other end to the frame part 12. Each arm is designed to withstand tensile and compressive forces and at least one of the arms is designed to withstand torsional moments. Movement of the linkage 24 is by means of an electric linear actuator 34. In an alternative embodiment (not shown) there is used a variable length strut.A first end 36 of the actuator is pivotally mounted on the frame part 12, whilst a second end 38 of the device is pivotally mounted on a suspension device 40 which will be described in greater detail hereafter.

By moving between extended and retracted positions, the linear actuator alters the geometry of the linkage 24 to cause the frame part 12 and the attached seat 14 to be raised or lowered. The construction of the linkage with the arms 26, 28 of differing length is such that the seat 14 reclines slightly as it is lowered. This is preferred by some passengers in certain situations, and has the advantage of automatically raising any foot or leg rest attached to the seat which may otherwise touch the ground as the seat is lowered. Alternatively, the linkage may comprise a simple parallel motion linkage.In an embodiment not shown, the wheelchair incorporates the adjustable leg rests, and the height adjustment arrangement is operatively connected to means for adjusting the position of leg rests, for example so that the legs may be automatically outstretched by- the passenger when lowering the seat.

Suspension for the seat 14 is provided by the spring suspension device 40 attached to the frame part 16. The device 40 consists of a combined spring and damper unit which depends on the spring characteristics of a square section metal rod supported by rubber cylinders inside an outer square section tube. The arrangement is economical to manufacture, and provides a damped spring support which is simply applied to the height adjustment arrangement. When the downward force on the seat and supporting frame part 12 is changed, the load is transferred to the suspension unit 40 by the linear actuator. The suspension unit 40 yields, permitting the seat to move downwards. Similarly, shock loads transferred upwards from the wheels are also absorbed by the suspension unit 40 with the result that the passenger experiences a particularly smooth ride.

To enhance this effect, batteries for supplying power to the wheelchair are mounted on the upper frame part 12, thus increasing the suspended weight component, which improves the ride.

There is thus provided a wheelchair which is suitable for both indoor and outdoor use, being of a robust but relatively compact design. A compact design is achieved because the height adjustment device is so arranged to provide sufficient space for electric motors and gearboxes to drive the wheelchair. The passenger experiences a particularly smooth and comfortable ride because of the suspension and height adjustment facilities. Steering is improved by means of the castor pivot arrangement.

It will be appreciated that modifications may be made within the scope of the invention. The height adjustment mechanism and the suspension arrangement may be varied within the scope of the Claims. The wheelchair may incorporate any suitable seat, together with any required arm rests, foot rests or other known equipment.

Whilst endeavouring in the foregoing Specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.

Claims

Claims:

1. A powered wheelchair comprising a frame including a part adapted to mount a seat, means associated with the frame permitting adjustment of the height of said part to raise and lower a seat mounted thereon, and a suspension arrangement operatively connected to the height adjustment means.

2. A wheelchair according to Claim 1, wherein the height adjustment means comprises a pivotal linkage.

3. A wheelchair according to Claim 2, wherein the linkage comprises a parallel motion linkage.

4. A wheelchair according to Claim 2, wherein the linkage so operates as to cause the seat to recline as it is lowered by the height adjustment means.

5. A wheelchair according to any of Claims 2 to 4, wherein the linkage extends between the seat mounting part of the frame and a base part of the frame.

6. A wheelchair according to any of the preceding Claims, wherein the height adjustment means is driven by an electric linear actuator.

7. A wheelchair according to any of Claims 1 to 5, wherein the height adjustment means is driven by a variable length strut.

8. A wheelchair according to Claim 6, wherein the actuator is pivotally mounted at one end on the seat mounting part of the frame and at another end on the suspension arrangement.

9. A wheelchair according to any of the preceding Claims and including adjustable leg rests, wherein the height adjustment means is operatively connected to means for adjusting the position of the leg rests.

10. A wheelchair according to any of the preceding Claims, wherein the suspension arrangement comprises a combined spring and damper device.

11. A powered wheelchair comprising a frame for mounting a seat thereon and mounting front wheels, a drive arrangement for the front wheels, and rear swivel castors, mountings for the castors being provided on the frame so as to lie at an angle greater than 90C thereto, thereby causing each castor to tend to move into alignment with a respective front wheel to stabilise the steering of the wheelchair.

12. A powered wheelchair according to Claim 11 and incorporating height adjustment means and a suspension arrangement as defined in any of Claims 1 to 10.

13. A powered wheelchair comprising a frame including a part adapted to mount a seat, and means associated with the frame permitting adjustment of the height of said part to raise and lower a seat mounted thereon, the adjustment means comprising a pivotal linkage as defined in any of Claims 3 to 5.

14. A powered wheelchair substantially as hereinbefore described with reference to the accompanying drawings.

15. Any novel subject matter or combination including novel subject matter disclosed, whether or not within the scope of or relating to the same invention as any of the preceding Claims.