GB2043554A - Motorised wheelchairs - Google Patents

Abstract

A wheelchair for use by an invalid includes a pair of laterally spaced large diameter wheels (24) the wheels being hubless and being provided with angularly spaced support elements (38, 39) which may be rotatable about their respective axes and on which a rim element (30) is supported for rotation. The large diameter hubless wheels enhance step or kerb climbing ability of the wheelchair while overcoming the weight problem associated with centrally supported large diameter wheels. The large diameter wheels are preferably located adjacent the front of the wheelchair and are driven by frictional engagement through a drive member (33) or through engagement of a pinion with an inner gear secured to the wheel (24). <IMAGE>

Description

SPECIFICATION Improvements in or relating to wheelchairs Description of the invention The present invention relates to a motorised wheelchair for use by an invalid, such a wheelchair being of the type comprising a supporting structure, including a seat for the invalid, a plurality of wheels on which the supporting structure is mounted, including at least a pair of laterally spaced wheels and at least one other wheel, and motor means for driving the wheelchair.

One of the desirable characteristics which a wheelchair of the kind specified is often required to have is the ability to climb steps such as those presented between a roadway and a pavement e.g. a kerb and which typically have a height of 3" to 6".

Motorised wheelchairs are well known and the driven wheels thereof may be either of small or large diameter.

Some wheelchairs are particularly adapted to be easily portable and have a supporting structure in the form of framework which enables folding of the wheelchair and with such wheelchairs it is necessary to keep the weight of the wheelchair to a minimum, the wheels therefore have a relatively small diameter. Problems are encountered with such wheelchairs when it is required for them to mount a step of a height which has previously been mentioned.

Other known wheelchairs, usually not portable, have larger diameter driven wheels and tend to be of considerably heavier construction.

Even though larger diameter wheels are provided, difficulties are still encountered as the weight of the wheelchair itself, plus the weight of the occupant, greatly increases the power necessary for the wheelchair to successfully surmount a step of the height mentioned above. In particular, if for example the wheelchair is driven towards a step if the spokes or other supporting means between the hub and the rim of the wheel were of sufficient strength to withstand the impact shock of the wheelchair being driven at a step at anything above an absolute minimal speed, the wheelchair would become impractically heavy.

Thus the design of a wheelchair which is suitable for everyday use and also has the ability to surmount such steps present serious problems since (a) It is desirable to approach the step relatively slowly to avoid shock to the invalid and to the wheelchair itself (such a shock may adversely effect the stability of the wheelchair) so the energy required to raise the wheelchair up the step cannot be derived principally from the kinetic energy arising from the movement of the wheelchair, therefore the wheelchair must not be of undue weight;; (b) the driving force or torque necessary to raise the wheelchair will be dependent upon the steepness of lift i.e. the horizontal distance travelled by the wheelchair to a given rise at its ends surrounding the step, and to climb a step the transmission of the torque required between hub and rim necessitates the provision of a strong and therefore heavy wheel; (c) it is necessary to avoid complexity of the arrangement provided to enable step climbing in order to avoid increase in cost and deterioration of reliability whilst maintaining a wheelchair that is practicable in all other respects.

It is an object of the present invention to provide a wheelchair for use by an invalid in which the ability to surmount steps or kerbs is enhanced without adding ecessive weight to the wheelchair or rendering it impracticable for normal use.

According to the present invention we provide a wheelchair, for use by an invalid, the wheelchair comprising a supporting structure, a seat for the invalid on said supporting structure, a plurality of wheels on which said supporting structure is mounted and motor means for driving at least one of said wheels, wherein (a) said wheels comprise at least one pair which are spaced apart laterally and are of a large diameter; (b) each wheel of said laterally spaced pair comprises a rim element;; (c) for supporting said rim element there is provided supporting means comprising a plurality of supporting elements mounted on said supporting structure at positions spaced apart angularly about the axis of said rim element and engaging said rim element through contact surfaces respectively on said rim element and on said supporting elements providing for rotation of said rim element about said axis thereof.

The contact surface on each of said rim elements is presented radially inwardly towards said axis and the contact surfaces on the supporting elements have parts engaging said contact surface on said rim element and which collectively are presented radially outwards and mounting means may be provided for each of said supporting elements for mounting these for rotation about respective axes extending through an aperture defined by said rim element.

One of the supporting elements may be operatively connected with the motor means to provide a driving means which may be operatively connected with the rim element by means of frictionally engaging surfaces one on the supporting element, and one on the rim element.

Alternatively, the rim element may be provided with tooth-like formations and the driving means may be in the form of a pinion connected to the motor means, the pinion being adapted to engage with the tooth-like formations on the rim element to cause rotation thereof.

Said pair of laterally spaced apart wheels of large diameter are preferably provided near the front of the wheelchair and at least one but preferably two further wheels are provided at the rear of the wheelchair. The wheels at the rear of the wheelchair may be of smaller diameter and may for example be castor wheels.

The diameter of the laterally spaced apart large diameter wheels can be of any size between about 1 2 inches to 40 inches and conveniently are in the region of 20 inches.

The diameter of the rear wheel or wheels may be smaller than that of the large diameter front wheels, but should not be too small, so as to assist the kerb climbing ability of the wheelchair.

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 of the present invention; Figure 2 is a side elevation of part of the wheelchair shown in Fig. 1; Figure 3 illustrates one of the support elements; Figure 4 is a cross-sectional view of one embodiment of rotary driving element; Figure 5 illustrates another embodiment of rotary driving element; and Figure 6 illustrates the supporting element shown in Fig. 3 and method of biasing it into engagement with the rim element.

Referring firstly to Fig. 1, the wheelchair illustrated comprises a supporting structure in the form of a frame, including a pair of side members 10 and 11, each side member 10 and 11 including a back upright member 1 2 of tubular form,a front upright member 1 3 also of tubular form and a pair of tubular members 14 and 1 5 interconnecting the back upright member 1 2 and the front upright member 13.

The embodiment of wheelchair illustrated is a folding wheelchair and in order to allow the two side members 10 and 11 to be folded into juxtaposition with one another, three links 1 6 interconnect the side frame members 10 and 11. The links 1 6 include a pair of pivotally connected linked elements which can be moved from a folded position (not shown) through the centre or aligned position to an overcentre position as shown in Figure 1 stretching and then fractionally relaxing the seat and back portions 22 and 21 and serving to maintain the side frame members 10 and 11 spaced apart.

Arm rests 1 9 with pads 20 are attached to respective side frame members 10 and 11.

The back panel 21 is formed as a sheet of flexible material secured between the back upright members 1 2 of the side frame to form a backrest. The seat for the invalid comprises a seat panel 22 also formed from a sheet of flexible material and which is secured between the tubular members 15 to provide the seat portion of the chair.

An additional panel 23 also in the form of a sheet of flexible material is secured between the lower tubular members 14 to provide a parcel shelf. Foot placements may be con nected either directly or indirectly to the front upright members 13.

The rear wheels of the wheelchair as illustrated comprise a pair of castor wheels 29, pivotally connected at the lower ends of the tubular back upright members 1 2 to swivel about upstanding axes. The front wheels of the wheelchair 24 each comprise a rim ele ment 30 having either a balloon or solid tyre 31.

Each wheel 24 is provided with motor means in the form of an electric motor 34 which motor 34 may be of the permanent magnet type i.e. having a stator including permanent magnets providing a magnetic field and a rotor having a comutator con nected to motor windings. Alternatively the motor may be provided with a stator having field windings for energisation by a battery to provide a magnetic field.

Each electric motor is secured to the wheelchair and is provided with a gear box, the gear box has a output shaft on which is carried a rotary driving element 33. Each rotary driving element may be connected to the output shaft of the motor gear box in the manner described and claimed in British Patent Specification No.

The rotary driving element 33 is provided with a metallic rim 30 carrying a rubber tyre 35.

Each of the motors 34 is mounted on the wheelchair via a three arm support member 37 which is itself secured by any suitable fastening means to respective side frame 10 or 11 of the chair. The support member is arranged in a "free space" situated internally of the rim element.

At or near the ends of two of the arms of the support member 37 supporting elements are provided in the form of wheels 38 and 39 each being mounted for rotation at the end of a respective arm of the support member 37 which wheels have a channel shape circumference provided with a contact surface adapted to contact the inwardly directed contact surface of the rim 30 to support the rim 30 of the wheel 34. Fig. 3 shows in detail the section of the guide wheel.

The rubber tyre 35 of the rotary driving 'element is also provided with a channel shape circumference and is arranged to frictionally engage with the rim 30 of the wheel 34. In the embodiment shown in the drawings, frictional engagement will be caused by a compo nent of the force, due to the weight of the wheelchair and occupant being transmitted through the contact area between the rotary driving element 33 and the wheel 24. Since the rotary driving element engages the wheel 24 substantially directly above the point of contact of the wheel 24 with the ground, the component of the force transmitted through the contact between the rotary driving element and the wheel 24 will be substantially the total force due to the weight of the wheelchair and the occupant borne by the front wheels of the wheelchair.

As an alternative arrangement for transmitting power to the wheels, the arrangement shown in Fig. 5 may be used. Fig. 5 illustrates an internal gear 40 which may be either formed on the internal surface of the wheels 24 or may be formed as a separate part and subsequently fastened to the internal surface thereof. The internal gear 40 may be made from a plurality of segments and secured to the inner surface of the wheel 24 by any suitable fastening means such as bolts.

The output shaft of the motor driven gearbox is connected to a pinion 41, the motor and gearbox being so positioned such that the pinion 41 engages with the teeth of the internal gear 40.

Such a drive arrangement ensures positive drive at all times and is of particular benefit in a wheelchair which is likely to be used in rough terrain.

Referring now to Fig. 6, one method of resiliently biasing the supporting elements into contact with the rim element is illustrated.

An end of one of the arms of a "spiderlike" support member, part of which is shown at 1 37 is provided with a sleeve-like member 45, the dimensions of which are such that limited movement between the sleeve-like member 45 and the support member 1 37 along the axis 46 is possible.

The sleeve-like member 45 has an extension 47, the extension 47 having a through bore 48 in which is located an axle 49 which carries the supporting element 1 38. A helical spring 50 is located between the end face 51 of the sleeve-like member 45 and the outer end 52 of the support member 37. The supporting element 38 is therefore resiliently biased away from the central axis of the rim element 31.

In practice, each of the supporting elements 38 may be biased in a similar manner.

Each of the motors 34 is supplied with electrical power from a battery which is conveniently supported on the shelf 23. The manner in which the power from the battery is supplied to each of the motors 34 may be as described in British Patent Specification No.

1,198,905 in which a joy stick 42 controls the operation of micro switches in a control box 43.

Alternatively the micro switches may be replaced by an electronic circuit in which the joy stick 42 controls the resistance of a pair of variable resistors, which in turn operates a mark space ratio chopper circuit to vary, in the continuously variable manner, the current supplied to the motors 34. In this way very accurate control of the steering and speed of the wheelchair can be attained. Such a circuit is described and illustrated in the Specification and Drawings of British Patent Application No. 735,176.

The described embodiment is only provided with a single rotary driving element in contact with each of the front wheels. It is envisaged however that one rotary driving element per wheel may be provided and, furthermore, resilient means may be provided to bias the or each rotary driving element into contact with the driven wheels 24. It is further envisaged in particular when resilient means are provided for urging the rotary elements into contact with the wheels 24 that the rotary driving element may alternatively engage the side of the rim or tyre of the wheel 24.In the case where frictional engagement means between the rotary driving element and the wheel 24 is replaced by the internal gear 40 and pinion 41, the co-operating gears, one on the wheel 24 and one on the output shaft of the gear box, may comprise bevel gears or any suitable co-operating gear faces whereby power can be transmitted from the output shaft to the gear box to the wheel 24.

The described embodiment has motor means in the form of a pair of electric motors 34 however it is also envisaged that a single motor may suffice in which case alternative steering means will be provided preferably on the rear wheel or wheels.

A significant advantage is obtained in using a large diameter wheel 24 as the large diameter greatly eases the problem of mounting steps and kerbs. Furthermore by applying the driving force through rotary driving elements spaced from the centre of the wheel 24, the problem of providing the wheel with sufficient strength to cope with torque transmision from a hub to the rim is eliminated thus allowing the construction of a wheel considerably lighter than would be the case if the wheel was mounted for rotation and driven at its centre.

Claims (18)

1. A wheelchair, for use by an invalid, the wheelchair comprising a supporting structure, a seat for the invalid on said supporting structure, a plurality of wheels on which said supporting structure is mounted, and motor means for driving at least one of said wheels, wherein (a) said wheels comprise at least a pair which are spaced apart laterally and are of large diameter; (b) each wheel of said laterally spaced pair comprises a rim element; (c) for supporting said rim element there is provided supporting means comprising a plurality of supporting elements mounted on said supporting structure at positions spaced apart angularly about the axis of said rim element and engaging said rim element through contact surfaces respectively on said rim element and on said supporting elements providing for rotation of said rim element about said axis thereof.

2. A wheelchair according to Claim 1 wherein (a) said contact surface of said rim element is presented radially inwardly towards said axis; (b) said contact surfaces on said supporting elements have parts engaging said contact surface on said rim element and which collectively are presented radially outwards; (c) mounting means is provided for each of said supporting elements for mounting these for rotation about respective axes extending through an aperture defined by said rim element.

3. A wheelchair according to Claim 2 wherein at least one of said supporting elements is operatively connected with said motor means, the contact surface of said one supporting element being adapted to frictionally engage the contact surface of said rim element.

4. A wheelchair according to Claim 1 wherein said supporting elements are angularly spaced from each other at equal angular intervals around the contact surface of the rim element.

5. A wheelchair according to Claim 2 wherein one of the supporting elements is situated adjacent the bottom of the rim element and wherein said supporting element situated at the bottom of the rim element is connected to the motor means.

6. A wheelchair according to Claim 1 or Claim 2 wherein the rim element is provided with tooth formations and the motor means is provided with a pinion meshing with said tooth formations.

7. A wheelchair according to Claim 6 wherein said pinion also forms one of said supporting elements.

8. A wheelchair according to any one of the preceding claims wherein the diameter of said laterally spaced pair of wheels is between 12 inches and 40 inches.

9. A wheelchair according to Claim 8 wherein the diameter of said pair of laterally spaced wheels is about 20 inches.

10. A wheelchair according to any one of the preceding claims wherein biasing means are provided, said biasing means being arranged to urge at least one of said supporting elements into contact with said rim element.

11. A wheelchair according to Claim 10 wherein each of said supporting elements is provided with biasing means adapted to bias the respective supporting element into contact with the rim element.

12. A wheelchair according to any one of the preceding claims wherein said rim element defines a radially inwardly situated free space and wherein said supporting member and said supporting elements are situated in said free space.

1 3. A wheelchair according to any one of the preceding claims wherein each of said laterally spaced pair of wheels is operatively connected to respective motor means.

14. A wheelchair according to Claim 1 3 wherein means are provided for steering the wheelchair, said means comprising manually operable means, operable to apply different powers to said motors.

1 5. A wheelchair substantially as hereinbefore described with reference to and as illustrated in Figs. 1, 2, 3 and 4 of the accompanying drawings.

16. A wheelchair substantially as hereinbefore described with reference to and as illustrated in Figs. 1 and 2 of the accompanying drawings but modified in that the drive means includes a pinion and inner gear as hereinbefore described and illustrated in Fig.

5 of the accompanying drawings.

1 7. A wheelchair substantially as hereinbefore described with reference to and as illustrated in Figures 1 and 2 of the accompanying drawings including biasing means as illustrated in Fig. 6.

18. A wheelchair including any novel feature or combination of features as described and/or illutrated herein.