Field of the Invention

The present invention relates to wheelchairs arid, in particular, to a wheelchair

mechanism for converting a four-wheeled wheelchair into a three-wheeled wheelchair and vice-versa, and a wheelchair with the mechanism.

The invention has been developed, primarily for use in converting a wheelchair

between an indoor use configuration and an outdoor use configuration and will be described hereinafter with reference to this application. However, it will be .

appreciated thai the invention is not limited to this particular field of use and the wheelchair ma be converted from one type- of indoor wheelchair to another type of indoor wheelchair, or from an outdoor wheelchair to another type of outdoor

wheelchair.

Background of the Invention

It is well known that wheelchairs to be propelled by a seated user come in two basic types. The first and most established type of wheelchair provides a seat with a seat back and armrests. The seat sits on a frame, to which a pair of large diameter rear wheels are attached so as to support the scat. A pair of front swivel or castor wheels is mounted to a front of the frame to support a front of the seat and it is noted that sometimes the seat armrests are integrally formed with ihe wheelchair frame.

The front swi el wheels provide significant mobility for the wheelchair in tight

environments and provide relatively fine control of the location and direction of the .

chair. Tlu's is particularly desirable when in relati ely tight spaces such as retail outlets or parts of the home environment. Whilst this first type of wheelchair provides satisfactory control for a user in au indoor environment, s\ich a wheelchair is

practically unsuitable for use on rough and uneven surfaces. Unfortunately, much desired outdoor wheelchair use is over such rough or uneven surfaces, severely

limiting the usefulness of the wheelchairs.

In order to overcome the disadvantages of using the first type of wheelchair on

outdoor or other rough and uneven surfaces, a three-wheeled wheelchair has been developed. The three- wheeled wheelchairs are similar to the wheelchair of the first type above but instead of providing a pair of front swivel or castor wheels a single castor wheel extends from the front: of the chair a predetermined distance to provide a substantially increased wheelbase. The three-wheeled wheelchair has been designed to provide sturdiriess and practicality over fine chair control and are used almost exclusively for sporting activities, particularly racing. Typically, the three-wheeled wheelchairs are designed to maximise the "pushing" efficiency of the user and have seating surfaces and frames configured to achieve this. In some three-wheeled wheelchairs ibr elite athletic use, the front castor wheel includes a steering mechanism akin to bicycle handle bars so that the user can steer the wheelchair with differential force applied to the rear wheels or by leaning forward and applying force to the steering wheel. Such configurations are not practical for non-sporting users.

Further, the diameter of the front wheel is larger than that of a conventional castor or swivel wheel. The increase in wheelbase length allows significantly better tracking and stability for use of the wheelchairs on uneven terrain and the large front wheel allows greater undulations to be climbed such as curbing and guttering. In combination, the increased wheelbase length and use of a laTger diameter wheel also allows a user to expend less energy to cover greater distances than is the case with the first type of conventional wheelchair above. .

Use of the three-wheeled types of wheelchairs allows users to have access and freedom to outdoor and other areas not previously or practically accessible in four- wheeled wheelchairs. However, use of the three-wheeled wheelchairs requires the user to swap from the first type of conventional wheelchair to the three-wheeled type of wheelchair when going from inside to outside and vice- versa when going from outside to inside. The most significant disadvantage associated with this is that many wheelchair users cannot easily transfer bet ween wheelchairs withoul the aid of lifting equipment, assistance from a carer or the application of significant effort from the . user of the chair. This limits the usefulness of providing the two types of wheelchairs.

It is also noted that if a user is travelling from home to, say, the local library in their wheelchair then the user will swap from the indoor wheelchair to the three- wheeled outdoor wheelchair when they are leaving their home. They will ride the outdoor wheelchair to the library but it is most likely there will not be an indoor wheelchair at the library for the user to swap into from the three-wheeled outdoor wheelchair on arrival. This type of situation presents -the user with the problem that if the library (or other venue) is not sufficiently spacious, the fine position control of a conventional wheelchair cannot be achieved with the three-wheeled wheelchairs.

Genesis of the Invention

The genesis of the present invention is a desire to provide a wheelchair mechanism which can be used on a wheelchair to allow it to be converted from use as an indoor four-wheeled wheelchair to an outdoor three-wheeled wheelchair, or to provide a useful alternative.

Summary of the Invention

Accordin to a first aspect of the invention there is provided a wheelchair mechanism extending between a seat support end and a trolley wheel support end, the wheelchair mechanism configured to support a front of a wheelchair seat at the seat support end and a trolley wheel at the wheel support end, the wheelchair mechanism configured for movement between a first position wherein the trolley wheel extends a predetermined distance from the front of the chair and supports the from of the wheelchair seat and a second position wherein the trolley wheel is disposed higher than a pair of wheelchair castor wheels which support the front of the seat.

According to a second aspect of the invention there is provided a swivel wheel restraint mechanism for controlling the swivel of a front swivel wheel of a three- wheeled wheelchair, the mechanism comprising a swivel restraint configured for movement between a first position being contiguous with the swivel to limit swivelliug thereof and a second position being spaced apart from the swivel.

According to third aspect of the invention there is provided a swivel wheel tracking mechanism comprising a tracking plate mounted intermediate a swivel wheel support and a swive wheel, the tracking plate configured to be rotated between a left hand position wherein the swivel wheel is rotated a predetermined angle in a left hand direction and a right hand position wherein the swivel wheel is rotated a

predetermined angle in a right hand direction According to another aspect of the invention there is provided a wheelchair comprising the mechanism according to the first aspect of the invention and/or the swivel wheel restraint mechanism according to the second aspect of the invention and/or the swivel wheel tracking mechanism according to the third aspect of the invention.

It can therefore be seen that there is advantageously provided a wheelchair _.

mechanism that allows a conventional four-wheeled wheelchair having a pair of from castor wheels to be converted into a three-wheeled outdoor wheelchair (and vice versa) without the user needing to change chairs or alight from the chair. It can also be seen that there is advantageously provided a swivel wheel tracking mechanism for a three- wheeled wheelchair which can adjust the direction of swivel of the swivel wheel and a swivel wheel lock to lock the swivel wheel into a particular direction to thereby provide better control tor the user of the wheelchair when in the three- wheeled configuration such as on sloped surfaces.

Brief Description of (lie Drawings

Preferred embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which;

Fig. 1 is an ele vated perspective v iew of a wheelchair havi ng a wheelchair mechanism in a first configuration according to the preferred embodiment;

Fig. 2 Ls an elevated perspective view of the wheelchair of Fig. 1 with the wheelchair mechanism disengaged from the first configuration:

Fig. 3 is a perspective view of the wheelchair of Fig. 1 with the wheelchair mechanism in a second configuration;

Fig. 4 is a perspective view of the wheelchair of Fig. 1 with the wheelchair mechanism moved from the configuration of Fig. 2 towards the second configuration;

Fig. 5 is a perspective of the wheelchair of Fig. I with the wheelchair mechanism moved from the configuration of Fig. 4 towards the second configuration;

Fig. 6 is a perspective view of a swivel trolley wheel locking mechanism with the wheel rotated in a left hand position of the wheelchair of Fig. 1 ; Fig. 7 is an underside perspective view of the swivel trolley wheel locking mechanism with the wheel in a centred position of the wheelchair of Fig. t where the wheel has been removed;

Fig. 8 is an underside perspective view of the swivel, trolley wheel locking mechanism with the wheel rotated in a right hand position of the wheelchair of Fig. I ;

Fig. 9 is an elevated perspective view of the swivel trolley wheel locking mechanism with the wheel in an un-centred position of the wheelchair of Fig. 1 ;

Fig. 10 is a side view of a swivel trolley tracking mechanism of the wheelchair Of Fig. I ;

Fig. Π is a top view of the swivel trolley tracking mechanism of Fig. 10 in a straight tracking configuration:

Fig. 12 is a top view of the swivel trolley tracking mechanism of Fig. 10 in a left hand tracking configuration;

Fig. 13 is a top view of the swivel trolley tracking mechanism of Fig. 10 in a right hand tracking configuration; and

Fig. 14 is a side view of the trolley wheel end of a wheelchair according to another preferred embodiment.

Detailed Description

Referring to the drawings generally, it will be appreciated that like reference numerals have beer, used to denote like components. A wheelchair 1 includes a chair member 2 having a seat portion 3 and a back rest 4,

The chair member 2 is supported at a rear end .5 by a pair of spaced apart rear wheels 6. The rear wheels 6 are mounted to the chair member rear 5 on an axle mechanism 7 which is mounted to the chair member rear 5 at a lower end of rear frame supports 8 integrally formed with Che chair member 2. A chair member front 9 is supported by a pair of spaced apart front castor or swivel wheels 10 mounted to a lower end of front frame supports 1 1 that are integrally formed with the chair member 2. Adjacent each castor wheel 10 is a foot support 12 configured to receive and support a foot of a person seated in tire chair member 2.

The wheelchair 1 further includes a wheelchair mechanism 15 extending between a seat support end 16 and a trolley wheel support end 17, The wheelchair mechanism 15 is mounted at the seat support end 16 to an underside of the chair member 2 at the chair member front 9. The trolley wheel support end 17 includes a trolley wheel 1 8 configured lo support the mechanism 15 and the chair member front 9. The trolley wheel 18 is mounted to the trolley wheel support end 17 on a swivel 19. As described below, a trolley wheel tracking plate 20 is disposed intermediate the swivel 19 and the trolley wheel support end 17.

The wheelchair mechanism 15 is hingedly mounted to the chair member front 9. The wheelchair mechanism 15 has a front portion 25 and rear portion 24 hingedly interconnected by hinge 22. The rear portion 24 includes a rear portion lower section 26 hingedly mounted by hinges 23 to the chair member front end 9 at one end and hingedly mounted by hinge 23 to the wheelchair mechanism front portion 25 at the other end. The rear portion 24 also includes a pair of upper sections 27 and 28. The rear portion upper sections 27 and 28 are hingedly connected at one end with each other and one end of rear portion upper section 27 is hingedly interconnected to the chair member front end 9 at or near where rear portion lower section 26 is hingedly mounted to the chair member front 9. The other end of rear portion upper section 28 is hingedly connected to the wheelchair mechanism front portion 25.

In Fig. 1 , the wheelchair mechanism- 15 is shown fully extended with wheelchair mechanism rear and front portions 24 & 25 being substantially parallel and locked in an over centred locking engagement where the rear portion upper sections 27 and 28 and rear portion lower section 26. A locking latch 30 is mounted to the rear portion upper section 28 by means of a hinge 31. Movement of the latch 30 in a clockwise direction (shown rotated in the perspective of Fig. 1 ) locks the wheelchair mechanism rear and front portions 24 & 25 into over centred locking engagement. T hat is, rear portion upper sections 27 and 28 are retained in over centred locking engagement by the latch 30.

Counter clockwise rotation of the latch 30 allows disengagement of the over centred locking engagement of the rear port ion upper sections 27 and 28. This allows movement from over centred engagement and allows the rear and front portions 24 & 25 to hingedly move about wheelchair mechanism hinges 22 and 23 to move from the three- wheeled wheelchair configurations of Fig. 1 into a four-wheeled wheelchair configurations of Fig. 3. Once the locking latch 30 has been rotated counter clock wise out of the Socked position as best shown in Fig. 2, the front portion 25 and rear portions 26 to 28 are free to rotate about hinges 22 & 23 which allows the mechanism 15 to be folded so that the trolley wheel 18 is raised higher above the front castor wheels 10 where wheelchair 1 is supported by the front castor wheels 10 and the rear wheels 6. This is best shown in Figs 3 to 5.

In the embodiment of Fig. 1 , the wheelchair mechanism 15 is fully extended and wheelchair rear and front portions 24 & 25 are engaged in over-centred locking engagement so that the trolley wheel 18 bears the load of the cliair member front 9 and the running surface of trolley wheel 1.8 is at substantially the same level as the running surfaces of the rear wheels 6. The front castor wheels 10 are raised clear of the ground by a predetermined height to allow the wheelchair 1 to ride on rear wheel 6 and the trolley wheel 18 thereby providing a three-wheeled wheelchair. Fig. 2 is an elevated perspective view of the wheelchair 1 with the locking latch 30 rotated counter clockwise with the rear portion upper sections being able to be moved from overcentred locking engagement. As best showing in Fig. 4, an elastic cord 34 is connected to the rear portion lower section 26 near where it is hingedly mounted to the wheelchair mechanism front portion 25. The elastic cord 34 extends through the . rear portion second upper section 28 adjacent the hinged connection with the rear portion first upper section 27. The elastic cord 34 then extends between the second upper section 28 and the locking latch 30 and engages in cleat 35 (or other cord restraining device as desired), disposed at or adjacent the end of the rear portion second upper section 28.

In use, the user moves the wheelchair mechanism 1 5 from a stowed position under the chair member 2 (best seen in Fig. 3) into an extended position (best shown in Fig. 4). Although not clearly illustrated, the wheelchair mechanism 15 is biased toward the extended position. Once the wheelchair mechanism 15 is moved to the position shown T U2011/000709

in Fig. 4, the user pulls on the cord 34 and tensions it. The cord 34 is held in tension by the cleat 35 and this has the effect of biasing the rear portion lower section 26 toward the rear portion second upper section 28.

The user then commences to initiate, or completes, a wheel-stand, where the front swivel wheels 10 are raised off the ground and the wheelchair mechanism

components are moved into over centred locking engagement. As noted above, the over centred locking engiigement is maintained by the locking latch 30. it is noted that latch 30 when rotated engages with apertures or slots 29 in the rear portion lower section 26 so as to retain the wheelchair mechanism 15 in over centred locking

engagement, it will be appreciated by a person skilled in the an that cord 34 can be substituted by some other means such as an embedded- spring loaded mechanism if desired, however, this may add to the cost and complexity of production of a

wheelchair 1 ,

The process of moving the wheelchair mechanism 15 from the configuration shown in Fig. 2 back toward the stowed configurations shown in figure 3, the latch 30 is rotated counter-clockwise and the cord 34 is disengaged from the cleat 35 and pulled

upwards. This can also be achieved by directly raising the rear portion second upper section 28, The wheelchair mechanism 15 is moved into the configuration shown in

Fig. 3.

The perspective view of the wheelchair 1 in Fig. 3 shows the over-centring of the mechanism 15 disengaged and being fully folded about hinges 22 & 23. The

mechanism 15 is disposed substantially under the seat 3 of the chair member 2. In this way, it can be seen that a user can actuate the release latch 30 whilst seated on the seat 3 of the wheelchair 1 and disengage the over centred locking engagement of the rear portion upper sections 27 & 28 and subsequently wheelchair rear and front

portions 24 & 25 to allow the wheelchair mechanism 15 to be nested under the seal 3 and travel on the castor wheels 10 to provide a conventional four-wheeled wheelchair.

That is, the movement of the wheelchair mechanism 15 between a three-wheeled wheelchair configuration where the trolley wheel 18 bears the load of the chair

member front 9 and a conventional four-wheeled wheelchair where the mechanism 15 is disengaged and the wheelchair 1 is supported at a front end 9 by castor wheels 10 can be relatively easily effected by a user seated in the chair member 2. The wheelchair mechanism 15 is moved under or substantially under the seat 3 to allow relatively unimpeded use of a conventional four-wheeled wheetcbair.

In the embodiment of Fig. 1 , once the mechanism 15 is moved from the second configuration shown in Fig. 3 into the configuration shown in Fig. 2, a wheel-stand is performed by the User. That is, a user causes the front end of the wheelchair to bear Jess load than the rear wheels of the chair which causes the mechanism 15 shown in Fig. 2 to move into the configuration of Fig, 1 once the elastic cable 34 is tensioned. The latch 30 is then rotated clockwise to retain the rear and front portions 24 & 25 in overcentred locking engagement.

So far as a large number of chair users are able to relatively easily perform a wheel- stand to lift the front wheel(s), it of no extra difficulty for the user to use the elastic cable 34 and a wheel-stand to engage the over centred locking engagement of mechanism 15. This engages the trolley wheel. 18 and disengages the castor wheels 10, so that the wheelchair is now relatively easily re-configured as an outdoor usable three wheele d wheelchair.

It will be appreciated that the wheelchair chair member 2 is fabricated as a

monocoque chassis having the seat 3, back rest 4, rear frame supports 8, and front frame supports 1 1 integrally formed. However, any conventional wheelchair design such as a frame to support the chair front 9 and rear wheels 6 can be employed. The monocoque chair member 2 shown in the preferred embodiment of the drawings has been employed to reduce the total weight of the wheelchair 1 so far as possible and preferably to significantly below 10kg. Of course, the types of material used to form the components of the wheelchair 1 can be chosen to suit predetermined performance criteria or can be made to economic expedience, as desired.

It will also be appreciated that the trolley wheel 18 can also be stowed under, substantially undeT, partly under or not at all under the seat 3 as desired. It is preferred that the trolley wheel 18 and wheelchair mechanism 15 are stowed under or substantially under the seat 3 and do not project significantly forward of the chair member front 9 when stowed so as not to hinder movement of a user seated of the chair member 2 o f the wheelchair 1 . Yet further, it will be appreciated that the wheelchair mechanism 15 can be formed from any number of components in addition to the rear and front portions 24 & 25, rear portion first and second upper sections 27 & 28 arid rear portion lower section 26 and can include any preferred number of hinged folding points to support the over centred locking engagement of the wheelchair mechanism 15 as desired.

Referring particularly to Figs 10 to 13, there is shown various views of a trolley wheel 18 tracking mechanism 40. The tracking mechanism 40 includes a tracking plate 20 disposed intermediate the trolley wheel 18 and the trolley wheel support end 17 of the mechanism 1 5. The tracking plate 40 is configured to be rotated between a left orientation (Fig, 12) or right orientation (Fig. 13) by a predetermined angle. Fig. 1 1 shows the tracking mechanism 40 in an unrotated or straight configuration.

The tracking plate 20 is rotatably mounted at an end of the trolley wheel 18, The rotation of the plate 20 is controlled by a tracking actuator 42 mounted to the plate 20 at an end distal from the trolley wheel 18. The actuator 42 includes a worm screw (not clearly illustrated) configured for engagement with the plate 20 so that rotation thereof causes the tracking plate 20 and hence trolley wheel 18 to be correspondingly rotated. The worm screw is connected via a cable 43 to a handle 44 mounted lo the mechanism 15. in use, the handle 44 is rotated by a user and the tracking plate 20 rotates accordingly. When the plate 20 is rotated, the trolley wheel .18 rotates correspondingly. In the embodiment illustrated, the trolley wheel 18 can be rotated by the tracking mechanism 40 left or right by up to 8°. It will be appreciated that this can be any desired any angle depending on the slopes to be traversed.

Use of the tracking mechanism 40 advantageously allows a user to travel across a sloped or cambered surface and maintain a straight line of travel. Typically, the trolley wheel 18 on a sloped surface would be caused to move down the slope as it is travelled across, The tracking mechanism 40 advantageously counters this and reduces the energy use of the user by not requiring a differential force to be applied by the user to the rear wheels to stay straight on a slope. ll will be appreciated by those skilled in the art that the worm screw arrangement can be replaced by any expedient mechanism that allows the trolley wheel 18 to be rotated from centre. For example, a pitman arm or rocker arm mechanism. An embodiment of the wheelchair 1 using a pitman arm is shown in Fig. 14. This is a side vi ew the trolley wheel support end 17 of the wheelchair 1 . In this embodiment, a user actuated handle 1 is connected to a pitman arm 62 by a rod 63. Rotation of handle 61 causes rotation of pitman arm 62 to rotate which in turn causes the tracking plate 20 to rotate.

Referring now to Figs 6 to 9, there is shown various views of a trolley wheel locking mechanism 50. The mechanism 50 includes a trolley wheel latch 51 moveable between a first position for engagement with a centrally located seat 52 on trolley wheel swivel 1 . When in the first position, the latch 51 is biased into engagement with the seat 52 on the swivel 19 and tlie swivel 19 and trolley wheel 18 are held by the latch 51 under bias to prevent swivel of the trolley wheel 18. That is, when the latch 1 is engaged with seat 52 the trolley wheel is locked against bias in a straight position. This prevents the trolley wheel 18 from 'wobbling', particularly when at speed.

The latch 51 can be disengaged from the seat 52 of the swivel 19 by applying a rotational force to the swi vel 19 that is greater than the bias of the latch 51 towards the first position. The latch 51 is most easily disengaged by the wheelchair user turning relatively sharply left or right. Once the latch 51 is disengaged by turning, the trolley wheel 18 is free to rotate until the seat 52 aligns with latch 1 and engagement occurs therebetween.

The latch 51 can b disengaged and moved into a second position remote from the seat 52. The latch 51 is connected to a locking mechanism lever 54 by means of a cable 55. The user pulls the lever 54 which causes the cable 55 to move the latch 51 out of engagement with the seat 52 to allow the trolley wheel 18 to swivel or rotate freely.

It will be appreciated that any preferred mechanisms can be used to provide the trolley ^' wheel tracking mechanism 40 and trolley wheel locking mechanism 50 as desired. For example, a rack and pinion mechanism can be used with the trolley wheel hacking mechanism.

In addition to a user of the wheelchair 1 being able to advantageously convert a conventional four-wheeled wheelchair into a three- wheeled outdoor wheelchair and vice versa without needing to alight from the chair, the trolley wheel tracking mechanism 40 allows a user to adjust the tracking of the trolley wheel 18 whilst seated in the chair member 2 and using the wheelchair 1 to traverse sloped surfaces or the like. The user seated on The chair member 2 can also advantageously lock the swivel of the trolley wheel 18 in a forward direction which can be unlocked or released to swivel by locking mechanism leveT 54, or by the user turning left or right relatively hard which causes disengagement of the trolley wheel lock until the trolley wheel 1 8 is swiveled into the straight position. Although not clearly illustrated, the wheelchair mechanism 15 is latched when moved into the second position and slowed under the seat 3. The mecttanism is resiliency biased away from the stowed configuration so that when the latch is actuated the wheelchair mechanism 15 moves some amount sufficient to allow a seated user to handle it. The bias in the preferred embodiment is provided by a spring embedded in one or both hinges 22 connecting the wheelchair mechanism seat support end 16 to the underside of the seat 3.

In alternative embodiment, not illustrated, the wheelchair mechanism 15 includes a longitudinally extendible fork arm extending between a trolley wheel support end and a seat support end. In use, the fork arm is telescopicaJly extendible between a first position where the trolley wheel is disengaged from the ground and adjacent to or under the chair member front, and a second position where the trolley wheel is engaged with a ground surface and the castor wheels are disengaged or lifted clear off the ground surface.

It will be appreciated that the wheelchair mechanism 15 can be retrofitted to conventional four-wheeled wheelchairs. Further, the wheelchair mechanism 15 may be integrated into prams, pushers, strollers and the like which also suffer instability outdoors when having four wheels and three-wheeled prams are disadvantageous for no being manoeuvrable in relatively small spaces such as shopping aisles.

The foregoing describes only one embodiment of the present invention and modifications, obvious to those skilled in the ait, can be made thereto without departing from the scope of the present invention.

The term "comprising" (and its grammatical variations) as used herein is used in the inclusive sense of "including" or "having" and not in die exclusive sense of "consisting only of.