GB1575354A

GB1575354A - Chassis for wheelchairs

Info

Publication number: GB1575354A
Application number: GB27162/77A
Authority: GB
Original assignee: Spastics Society
Current assignee: Spastics Society
Priority date: 1978-05-19
Filing date: 1978-05-19
Publication date: 1980-09-17

Description

(54) IMPROVEMENTS IN CHASSIS FOR WHEELCHAIRS (71) We, THE SPASTICS SOCIETY, a British Company of 12 Park Crescent, London W1N 4EQ., do hereby declare the invention, for which we pray that a Patent may be granted to us, and the method by which it is to be performed to be particularly described in and by the following statement: This invention relates to wheelchairs and in particular to an improved chassis for wheelchairs.

According to the present invention we provide a chassis for a wheelchair comprising a pair of laterally spaced side components connected to each other by a cross member, each side component comprises a respective elongate first element one end of which is connected to a respective castor and a respective elongate second element hingedly connected to said first element intermediate the ends of said first element, a respective coil spring acting between the other end of said first element and said second element and a respective fixed axle wheel is mounted adjacent to one end of said coil spring.

In one preferred construction the castor and fixed axle wheel of each side component are sprung so that a smoother ride is obtained. Preferably each castor is pivotally connected to the associated first element and each second element comprises a generally Z-shaped frame member one end of which is pivotally connected to the associated castor, the other end of which mounts the associated fixed axle wheel and an intermediate portion of which is hingedly connected to the associated first element.

As a result the castor and fixed axle wheel of each side component are sprung by the single coil spring acting between the first and second elements.

In an alternative construction only the fixed axle wheel of each side component is sprung, the associated castor being fixed.

Conveniently each second element then comprises a generally L-shaped frame member which depends beneath the associated first element with one end hingedly connected to the first element and the other end mounting the associated fixed axle wheel.

Each side component also has a respective third element one end of which is fixed to the associated castor and the other end of which is fixed to the associated first element so that the castor is fixed relative to the side component. Preferably each third element comprises a generally L-shaped frame member which overlies the associated first element and is connected thereto adjacent to the hinge connection between the first element and the associated second element.

Conveniently each first element comprises es a respective limb of a U-shaped frame member and the castors are connected to the free ends of the limbs.

Preferably the chassis includes a manually operable brake system engageable with the fixed axle wheels to lock the wheels against rotation. Conveniently the brake system comprises a pair of levers pivotally mounted on the chassis and control means for controlling movement of the levers to bring the levers into and out of engagement with the wheels. Preferably the control means comprises a toggle linkage. Advantageously the levers are resiliently biassed to a position in which they are out of engagement. The levers may be adjustably mounted so that they can be moved to allow for wear or the levers may include respective brake pads adjustably mounted to allow for wear.

The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings wherein: Figure 1 is a perspective view of a wheelchair including the chassis according to the invention; Figure 2 is a perspective view of the chassis shown in Figure 1; Figure 3 is an enlarged perspective view of the connection to the chassis of one of the castors shown in Figure 2 in which the castor is sprung relative to the chassis; Figure 4 is an enlarged perspective view of the brake system shown in Figure 2; and Figure 5 is a perspective view of one side component of a modified chassis.

Referring to the drawings, Figure 1 shows a wheelchair comprising a chassis 1 according to the invention and a seat 2 mounted on the chassis.

The chassis 1 comprises a sprung frame 3 mounting a pair of rear wheels 4 and a pair of front swivel castors 5. The chassis further includes manually operable locking means 6 for securing the seat 2 to the chassis and a manually operable brake system 7 for locking the rear wheels 4 against rotation.

The sprung frame 3 shown in Figure 2 comprises two laterally spaced side components 8. Each side component is similar and comprises first and second elements 9 and 10 respectively hingedly connected to each other about a point 11 intermediate their ends. Each first element 9 comprises a respective generally Z-shaped tubular frame member 12 and each second element 10 comprises a respective limb 13a of a Ushaped tubular frame member 13. The free end of each limb 13a is pivotally connected to a respective one of the castors 5. One end portion 12a of each frame member 12 overlies the associated limb 13a of the second member 13 and is pivotally connected to the associated castor by a respective pair of swivel links 14.The other end portion 12b of each frame member 12 depends beneath the associated limb 13a of the second member 13 and a respective coil spring 15 acts between each end portion 12b and the adjacent end of the associated limb 13a of the member 13.

A fixed axle 16 extends between the end portion 12b of the members 12 adjacent to the respective connections to the coil springs 15. One rear wheel 4 is releasably secured to one end of the fixed axle by a spring loaded detent (not shown) engaging an annular groove (not shown) formed in the axle and the other rear wheel is similarly secured to the other end of the fixed axle. The limbs 13a of the member 13 extend generally parallel to one another and are held apart by a connector bar 17 extending therebetween.

The bar 17 carries the abovementioned locking means 6 which comprises a pair of relatively spaced clamps 18 in which a cross bar 19 on the seat 2 is received. Each clamp comprises a spring loaded jaw 20 and a movable jaw 21 operable through a respective toggle linkage 22. The toggle linkages 22 are connected to a common operator handle 23.

The brake system shown in more detail in Figure 4 comprises a pair of levers 24 and a manually operable toggle linkage 25 comprising a connector link 26 and an operator link 27 for controlling movement of the levers. Each lever 24 is pivotally connected to a respective sleeve 28 mounted on the end portion 12b of a respective frame member 12. Each sleeve 28 is axially adjustable on the end portion 12b. Respective one ends of the levers 24 are pivotally connected to each other and are connected by a generally U-shaped member 29 to the connector link 26. The operator link 27 is pivotally connected at an intermediate point in its length on the fixed axle 16 and the free end of the operator link forms a handle 30.

A coil spring 31 extends between the fixed axle 16 and the U-shaped member 29 and resiliently biasses the levers 24 to the released or brake-off position shown in broken lines in Figure 4. To move the levers 24 to the engaged or brake-on position the operator handle 30 is depressed to the position shown in full lines in Figure 4. The over centre action of the toggle linkage 25 retains the levers 24 in the engaged position against the resilient biassing of the spring 31.

The seat 2 comprises a seat frame 32 on which seat, back and side members 33, 34 and 35 respectively are detachably secured.

The cross bar 19 depends beneath a base portion 32a of the seat frame and extends transversely of the seat frame. The seat 2 is pivotal relative to the chassis 1 about the locking means 6 which acts as a fulcrum for pivotal movement. A manually operable tilt adjuster 36 comprising two telescopic members 36a, 36b extends between a back portion 32b of the seat frame and the portion 13b of the frame member 13 connecting the limbs 13a. The seat also has a footrest 37 which is pivotal relative to the seat frame 32 and can be set at any desired angular position by locking means 38. The back portion 32b of the frame has hinged connections 39 such that the upper portion, which forms a handle 40, can be folded to a position in which it over-lies the seat member 33.

Normally the seat 2 is mounted on the chassis 1 with the cross bar 19 engaging the locking means 6 and two lateral projections 32c at the lower front end of the seat resting on the respective end portions 12a of the members 12. The tilt adjuster 36 is locked to prevent undesirable pivoting of the seat 2 for example by sudden movement of an occupant or in response to shock loads applied to the wheels as will now be described.

In use, when one of the castors 5 rides over a bump the associated limb 13a of the member 13 hinges relative to the associated member 12 about the hinge connection 11 to compress the coil spring 15 acting between the members. Similarly when a rear wheel rides over a bump the associated member 12 hinges relative to the associated limb 13a of the member 13 about the hinge connection 11 to compress the coil spring 15 acting between the members.

Relative hinging movement about the connection 11 between the members when a castor or a rear wheel is subjected to a shock load is allowed for by the swivel links 14 connecting the end portion 12a of each member 12 to the associated castor.

It will be appreciated from the foregoing that the respective castor 5 and fixed axle wheel 4 on each side of the chassis are sprung by a single coil spring 15 acting between the members on that side of the chassis and any shock loads to the castor or fixed axle wheel are mainly absorbed by compression of the associated coil spring so that a smoother and more comfortable ride is obtained. It will be understood that the spring characteristic of the castors and fixed axle wheels is determined by the strength of the associated coil spring and that this can be selected so that a wide range of shock loads are accomodated.

In a modification to the above-described chassis 1 the fixed axle wheels 4 only are sprung, and the castors 5 are fixed relative to the chassis. One of the side components of the modified chassis is shown in Figure 5, the other side component is similar. Where appropriate like reference numerals have been used for parts corresponding to those shown in Figures 1 to 4. The Z-shaped frame member 12 is replaced by a generally L-shaped frame member 41 one end of which is hingedly connected to a lug 42 secured to the limb 13a of the member 13 at a point 43 intermediate the ends of the limb 13a. The member 41 depends beneath the limb 13a and the other end mounts the fixed axle wheel 4 adjacent to the coil spring 15.

As before shock loads applied to the fixed axle wheel 4 are absorbed by the relative hinging movement between the L-shaped member 41 and the limb 13a of the member 13 to compress the coil spring 15. Additionally an L-shaped frame member 44 is provided which overlies the limb 13a of the member 13. One end of the member 44 is fixed to the castor 5 and the other end is fixed to the limb 13a adjacent to the point 43. In this way each castor is fixed relative to the chassis i.e. unsprung. It will be appreciated that the member 44 may be connected to the limb 13a at any point along the length of the limb 13a.

The above-described chassis may be modified in a number of ways, for example the second elements 10 may comprise separate elongate members with a cross bar extending between to correctly space the side components and also provide a mounting for one end of the seat tilt adjuster 36.

The fixed axle wheels 4 may be detachably secured to the axle 16 by any suitable means known to those skilled in the art or they may be fixed to the axle. The wheels 4 may have solid rubber tyres or pneumatic tyres.

Each Z-shaped frame member 12 may be connected to the associated castor by one swivel link only although two are preferred.

It will be understood that the abovedescribed chassis is not restricted to a wheelchair having the above-described seat 2 and locking means 6. Thus the chassis may be used with any other suitable seat for example a seat comprising a unitary body moulded from plastics material with a cross bar 19 depending beneath to engage the locking means 6. Alternatively the locking means 6 may be on the seat and the cross bar 19 on the chassis. Furthermore the seat may be detachably secured to the chassis by any other suitable means known to those skilled in the art or the seat may be fixed to the chassis.

Finally it will be appreciated that the invention is applicable to electrically driven as well as manually propelled wheelchairs.

Thus in an electrically driven wheelchair each fixed axle wheel is normally driven by a respective electric motor and suitable controls are provided on the seat for controlling the drive to the wheels. The drive transmission may be of any appropriate type and preferably includes means for disengaging the drive so that, in the event of the motors failing, the drive can be disengaged to allow the wheelchair to be manually propelled.

WHAT WE CLAIM IS: 1. A chassis for a wheelchair comprising a pair of laterally spaced side components connected to each other by a cross member, each side component comprises a respective elongate first element one end of which is connected to a respective castor and a respective elongate second element hingedly connected to said first element intermediate the ends of said first element, a respective coil spring acting between the other end of said first element and said second element and a respective fixed axle wheel mounted adjacent to one end of said coil spring.

2. A chassis according to Claim 1 wherein each second element is hingedly connected intermediate its ends to the associated first element.

3. A chassis ateording to Claim 2 wherein the castor of each side component is also connected to one end of the associated second element and the fixed axle wheel of each side component is connected to the other end of the associated second element.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. member 12 about the hinge connection 11 to compress the coil spring 15 acting between the members. Similarly when a rear wheel rides over a bump the associated member 12 hinges relative to the associated limb 13a of the member 13 about the hinge connection 11 to compress the coil spring 15 acting between the members. Relative hinging movement about the connection 11 between the members when a castor or a rear wheel is subjected to a shock load is allowed for by the swivel links 14 connecting the end portion 12a of each member 12 to the associated castor. It will be appreciated from the foregoing that the respective castor 5 and fixed axle wheel 4 on each side of the chassis are sprung by a single coil spring 15 acting between the members on that side of the chassis and any shock loads to the castor or fixed axle wheel are mainly absorbed by compression of the associated coil spring so that a smoother and more comfortable ride is obtained. It will be understood that the spring characteristic of the castors and fixed axle wheels is determined by the strength of the associated coil spring and that this can be selected so that a wide range of shock loads are accomodated. In a modification to the above-described chassis 1 the fixed axle wheels 4 only are sprung, and the castors 5 are fixed relative to the chassis. One of the side components of the modified chassis is shown in Figure 5, the other side component is similar. Where appropriate like reference numerals have been used for parts corresponding to those shown in Figures 1 to 4. The Z-shaped frame member 12 is replaced by a generally L-shaped frame member 41 one end of which is hingedly connected to a lug 42 secured to the limb 13a of the member 13 at a point 43 intermediate the ends of the limb 13a. The member 41 depends beneath the limb 13a and the other end mounts the fixed axle wheel 4 adjacent to the coil spring 15. As before shock loads applied to the fixed axle wheel 4 are absorbed by the relative hinging movement between the L-shaped member 41 and the limb 13a of the member 13 to compress the coil spring 15. Additionally an L-shaped frame member 44 is provided which overlies the limb 13a of the member 13. One end of the member 44 is fixed to the castor 5 and the other end is fixed to the limb 13a adjacent to the point 43. In this way each castor is fixed relative to the chassis i.e. unsprung. It will be appreciated that the member 44 may be connected to the limb 13a at any point along the length of the limb 13a. The above-described chassis may be modified in a number of ways, for example the second elements 10 may comprise separate elongate members with a cross bar extending between to correctly space the side components and also provide a mounting for one end of the seat tilt adjuster 36. The fixed axle wheels 4 may be detachably secured to the axle 16 by any suitable means known to those skilled in the art or they may be fixed to the axle. The wheels 4 may have solid rubber tyres or pneumatic tyres. Each Z-shaped frame member 12 may be connected to the associated castor by one swivel link only although two are preferred. It will be understood that the abovedescribed chassis is not restricted to a wheelchair having the above-described seat 2 and locking means 6. Thus the chassis may be used with any other suitable seat for example a seat comprising a unitary body moulded from plastics material with a cross bar 19 depending beneath to engage the locking means 6. Alternatively the locking means 6 may be on the seat and the cross bar 19 on the chassis. Furthermore the seat may be detachably secured to the chassis by any other suitable means known to those skilled in the art or the seat may be fixed to the chassis. Finally it will be appreciated that the invention is applicable to electrically driven as well as manually propelled wheelchairs. Thus in an electrically driven wheelchair each fixed axle wheel is normally driven by a respective electric motor and suitable controls are provided on the seat for controlling the drive to the wheels. The drive transmission may be of any appropriate type and preferably includes means for disengaging the drive so that, in the event of the motors failing, the drive can be disengaged to allow the wheelchair to be manually propelled. WHAT WE CLAIM IS:

1. A chassis for a wheelchair comprising a pair of laterally spaced side components connected to each other by a cross member, each side component comprises a respective elongate first element one end of which is connected to a respective castor and a respective elongate second element hingedly connected to said first element intermediate the ends of said first element, a respective coil spring acting between the other end of said first element and said second element and a respective fixed axle wheel mounted adjacent to one end of said coil spring.

4. A chassis according to Claim 3 where

in each second element is generally Zshaped and said one end overlies the associated first element and said other end depends beneath the associated first element.

5. A chassis according to Claim 3 or Claim 4 wherein said one end of each second element is connected by a swivel link to the associated castor.

6. A chassis according to Claim 1 wherein each second element is hingedly connected at one end to the associated first element.

7. A chassis according to Claim 6 wherein the fixed axle wheel of each side component is connected to the other end of the second element.

8. A chassis according to Claim 6 or Claim 7 wherein each side component further comprises a third elongate element one end of which is fixed to the associated castor and the other end of which is fixed to the first element.

9. A chassis according to Claim 8 wherein the second and third elements of each side component comprise generally Lshaped members and the second element depends beneath and the third element overlies the associated first element.

10. A chassis according to Claim 8 or Claim 9 wherein said one end of each third element is connected to the associated first element adjacent to the hinge connection between the first element and the associated second element.

11. A chassis according to any one of the preceding claims wherein each first element comprises a respective limb of a U-shaped frame member and the associated castor is connected to the free end.

12. A chassis according to any one of the preceding claims wherein the first elements are adapted to mount a seat.

13. A chassis according to Claim 12 including a connector bar extending between the first elements and mounting locking means engageable with the seat.

14. A chassis according to Claim 13 wherein the locking means comprises a clamp engageable with a cross bar depending beneath the seat.

15. A chassis according to Claim 14 wherein the clamp has a fixed jaw and a movable jaw operable through a toggle linkage.

16. A chassis according to any one of the preceding claims including a brake system engageable with the fixed axle wheels to lock the wheels against rotation.

17. A chassis according to Claim 16 wherein the brake system comprises a pair of levers pivotally mounted on the chassis and control means for controlling movement of the levers.

18. A chassis according to Claim 17 wherein the control means comprises a toggle linkage.

19. A chassis according to Claim 18 wherein the toggle linkage is arranged to operate in a vertical plane.

20. A chassis according to any one of the preceding claims wherein the fixed axle wheels are at the rear and the castors are at the front of the chassis.

21. A chassis for a wheelchair substantially as herein described with reference to Figures 1 to 4 of the accompanying draw ings.

22. A chassis for a wheelchair substantially as herein described with reference to Figures 1 to 4 of the accompanying drawings as modified by Figure 5.

23. A wheelchair comprising the chassis according to any one of the preceding claims and a seat mounted on the chassis.