NZ203412A - Wheelchair attachment for climbing steps:extra wheel overlaps front wheels - Google Patents

Description

Priority Date(s): Complete Specification Filed: '.?3 Class: a 6 .'SO?, ft/- ■ 2034 1 2 Publication Date: P.O. Journal, No: 111 JUL 1986 /P&S Patents Form No.5.

Patents Act 1953 COMPLETE SPECIFICATION "Wheelchair Attachment" WE, BETSTONE INDUSTRIES LIMITED, of 75 Montreal Street, Christchurch, New Zealand, a company organised and existing under the laws of New Zealand, 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 283412 - 1CX- WHEELCHAIR This invention relates to a wheelchair.

It is conventional practice to provide wheelchairs with motor driven rear wheels, and front wheels which are free to rotate and which are castor mounted so that the front wheels are able automatically to move to the required setting during the use of the chair.

In use it has been found that an inherent difficulty arising in the use of the known wheelchairs is that the wheelchairs are not able readily to mount or climb an abrupt step such as a kerb defining the transition between a roadway and a pedestrian footpath.

According to the present invention there is provided a wheelchair having a pair of castor mounted front wheels, the castor axes of the front wheels lying in a common plane; and an auxiliary rotatable member mounted centrally between the front wheels for rotation about an axis lying in or substantially in said common plane, the auxiliary member being positioned to overlap the front wheels when viewed in a direction transverse to the direction of forward movement of the wheelchair and having an arcuate working surface which, as the wheelchair approaches a kerb, engages the kerb before the front wheels, the auxiliary member then being effective to lift the front of the wheelchair as the wheelchair advances to assist the wheelchair to negotiate the kerb. 203412 A wheelchair according to the ivention is able readily to mount a kerb due to the particular mounting arrangement of auxiliary member.

Accordingly in one aspect the invention consists in a wheelchair having a pair of castor mounted ?fron-t wheels, the castor axes of the front wheels lying in^a common plane; and an auxiliary rotatable member mounted centrally between the front wheels for rotation about an axils lying in or substantially in said common plane, the auxiliary member being positioned to overlap the front wheels when viewed in a direction transverse to the direction of forward movement of the wheelchair and having an arcuate working surface which, as the wheelchair approaches a kerb, engages the kerb before the front wheels, the auxiliary member then being effective to lift the front of the wheelchair as the wheelchair advances to assist the wheelchair to negotiate the kerb.

As used herein the term "the auxiliary rotatable member" is a wheel or roller.

Preferably the rotatable member has a radius of curvature greater than that of the front wheel.

The invention will be better understood from the following description of a preferred embodiment thereof, given by way of example only, reference being had to the accompanying drawings, wherein: Figure 1 is a highly schematic representation of a side view of a wheelchair incorporating electrically driven rear wheels; Figure 2 is a schematic front view of the wheelchair of Figure 1; Figure 3 is a view of a wheelchair of a construction similar to that of Figures 1 and 2, but in accordance with the present invention; Figure 4 is a front view of the wheelchair of Figure 3; 203412 Figure 5 is a fragmentary perspective view of the wheelchair of Figures 3 and 4; and Figures 6 to 9 are diagrammatic representations of various stages of mounting a kerb.

Referring now to the drawings and more particularly to Figures 1 and 2, the wheelchair 1 shown therein includes side frames 2 having front and rear transverse ra£ls. These side frames 2 are connected to each other by frame members 3, 4 which are pivotally connected at 5 and are connected to the frames 2 by pivot connections 5A. An arm rest forming frame unit 6 is mounted on each side frame by way of socket type connection means 7- Each unit 6 includes a side panel 7A. The rear uprights 8 of the units 6 provide support for a flexible back rest sheet 10 formed of plastics, fabric or the like. The uprights also provide at their upper ends handles 9 for enabling the chair to be manually controlled. -s- 203412 Each of "the side frames includes an upper rail 11, these rails being used as the means of mounting the end regions 12 of a flexible seat forming sheet 13- The side frames also include intermediate transverse rails 5 15, with each of the latter including a generally- rectilinear section 16, and a generally L-shaped section 17 that extends in prolongation of the section 16 but at ■N a higher level to connect with the front upright 18 of the associated side frame 2.

A main motor driven wheel 19 is mounted on each frame 2 by way of a combined electric motor and transmission arrangement 20.

The wheelchair 1 also includes braking arrangements but these are not shown in the Figures. 15 The lower end regions of the frame front rails 18 are utilised to mount castorable front wheels 21.

Each of these front wheels 21 is rotatably mounted by a suitably shaped fork 22 which is rotatable about a vertical castor axis 22A whereby the front wheel is able to undergo the castoring action required during steering.

A footrest 23 is carried from a support arm 24 extending from each upright l8._ Each footrest 23 is movable between a position of use and a retracted position when not required for use.

Control arrangements (now shown) are provided for enabling the user of the chair selectively to drive the wheelchair 1 backwards or forwards as desired, and also to steer the chair by means of a differential drive-of the main wheels 19. In practice, a battery 30 carriage (now shown) is provided at the rear of the wheelchair 1.

Referring now to Figures 3 and 4 of the drawings, athese Figures are generally similar to Figures 1 and 2, % ^except that Figures 3 and 4 illustrate the wheelchair of 5 Figures 1 and 2 fitted with a step or kerb climbing unit . 6 203412 As will be seen the unit 25 comprises a wheel 26 located adjacent the front of the wheelchair and centrally between the front wheels 21. The wheel 26 is so carried by a support bracket 27 that it is normally out of contact with any surface upon which the wheelchair is resting or travelling and such that the leading part of the wheel 26 is slightly in advance of the leading pterts of the castored wheels 21. The relative positioning of the wheels 21 and 26 will be considered in detail hereinafter.

The support bracket 27 comprises two similarly shaped arms 28 connected at one end with the axle 29 of the wheel 26 and at the other ends with a transverse main arm 30 which is itself connected to the forward end regions of the bottom transverse rail sections 16 of the side frames 2. The transverse arm 30 includes pins 30A which are able firmly to engage with the forward facing ends of the sections 16, and are held in position by bolts and wingnuts (not shown).

If the side frames 2 are not of the specific form shown in the Figures 3 and 4 the transverse support or main arm 30 may be connected to the side frames 2 by means of brackets (not shown) which allow ready mounting to and ready removal of the unit 25 from the wheelchair 1. It will be understood that whatever form of mounting is used for the unit 25 it is necessary that the unit 25 be removable if the wheelchair is to be folded.

In practice, the relative positioning and diameters of the wheel 26 and the wheels 21 is of great importance. In the first place the axis of rotation of the wheel 26 needs to be located in or substantially in the plane containing the vertical castor axes of the wheels 21. In addition, the relative diameters of the two wheels need to be such that, looking from the side \o -X- 203412 of the wheelchair the cusp or spinode formed by the overlapping or meeting region of the curved working surfaces of the wheels 21 and 26 (shown at 26A of Figure 3 and Figures 6 to 9) needs to be as shallow 5 as possible.

In a practical situation, bearing in mind that an average kerb height of 3 to 4 inches (75 to 100 mm) and front wheels of a conventional diameter of 8 inches (203 mni) the diameter of the auxiliary wheel preferably 10 lies in the range of 10.5 inches (267 mm) to 12.5 inches (318 mm) with a preferred diameter range of 11 to 12 inches (280 to 3^5 mm).

A convenient practical range of settings for the height of the axis of the auxiliary wheel 26 above 15 ground level is within a range 6 to 7 inches (152-178 mm) with a particularly preferred range of 6.5 to 6-75 inches (165 to 171 mm).

With the arrangement as discusse'd it has been found that an average kerb can be readily mounted 20 without it being necessary for the user of the wheelchair to have to accelerate as is the case with kerb mounting arrangements in which the mounting wheel is located well in advance of the wheelchair front wheels. Also it has been established as a result of wide testing that the 25 positioning of the auxiliary wheel as described above the front wheels 21 are most unlikely to move into a bridging angle relative to the kerb during a kerb mounting operation as a consequence of the wheelchair user not approaching the kerb in a direction exactly 30 at right angles to the run of the kerb.

With the above discussed arrangements it will be found that the auxiliary wheel 26 is able to contact and co-operate with a step i.e. kerb, in advance of the contact of the front wheels 21 with the same kerb, and also such that by the time the auxiliary wheel 26 has 203412 ■V been advanced by the forward motion of the wheelchair into co-operation with the upper surface of the kerb the front wheels 21 will have been rolled into a position in which they are in contact with the front surface of the kerb and are possibly in the process of negotiating the edge of the kerb. The particular instant at which this occurs will be related to the diameters of the wheels 21,26/ the height of the kerb and the resiliency or compressibility of the material forming the tyres of the wheelchair. Also in the event of inflatable tyres the inflation pressure will become a relevant factor.

Referring now to Figure 5 there is shown to a larger scale the construction and fitting of the unit 25 to the framework of the wheelchair. As will be seen the axle 29 of the auxiliary wheel 26 is carried from support arms 28 which are in turn mounted from the transversely directed main arm 30. This arm 30 is supported by the rail sections 16 of the two side frames 2.

Referring now to Figures 6 to 9, Figure 6 is intended to depict the situation when the auxiliary wheel 26 has just contacted the leading or facing edge of the kerb 31• It will be noted that the front wheels 21 of the wheelchair are still in contact with the road 32. As the wheelchair 1 moves forward the auxiliary wheel 26 rolls progressively onto the kerb 31• At the position shown in Figure 7 the wheel 26 is just moving onto the kerb upper surface 33 and the front wheels 21 are by that time in contact with the kerb edge of the kerb 31- Whether or not the wheels 21 actually lift from the road 32 will depend upon the various factors above discussed such as the relative diameters of the wheels 21 and 26 and the relative positioning of their axes of rotation. Other factors such as the extent of relative tyre crushing will have a bearing upon the actual 0 APR 1986^ 4> -X- 203412. situation.

Further forward movement of the wheelchair towards the kerb 31 causes the wheel 26 to move up onto the upper surface 33 of the kerb 31- This action will cause the front wheels 21 to lift up towards the upper surface 33 whilst rolling' against vertical surface of the kerb. This is schematically shown in Figure 8.

* During further forward movement of the chair the lift of the front wheels 21 towards the upper surface of the kerb 31 will lift the auxiliary wheel 26 away from contact with the surface 33- This is shown in Figure 9- It will be understood that the above mentioned relative positioning of the wheels in relation to the diameters thereof is intended to ensure that at all times a positive support is provided for the front regions of the wheelchair, whereby a smooth transition is obtained during the movement or lifting from road level to kerb level. This is achieved by the progressive transfer of the load from the auxiliary wheel 26 to the "front wheels as the latter mount the kerb 31- Thus, the front end of the wheelchair is not allowed to fall freely from a raised position.

In other words, the user of the wheelchair is not subjected to a sudden bump during the negotiation of a kerb which bumping could well be a very troublesome and dangerous occurance to some users of wheelchairs. In particular such users could well be those who rely on control systems which do not involve movements of hands and arms, that is the very seriously handicapped.

It will be appreciated that whilst a single auxiliary wheel 26 has been discussed a double wheeled construction could be used in which construction the ' auxiliary wheels would be co-axial, both wheels being located centrally between the front wheels 21. 203412 1 -j( - It will be noted that the auxiliary wheel 26 does not extend forwardly of the footrests of the wheelchair. Amongst other things this ensures that the wheelchair user1s legs and clothing can be kept 5 away from possible engagement or entanglement with the climber unit wheel 26. 203412 i o -X-

Claims (10)

WHAT WE CLAIM IS: |

1. A wheelchair having a pair of castor mounted front wheels, the castor axes of the front wheels lying in a common plane; and an auxiliary rotatable member as hereinbefore defined mounted centrally between the front wheels for rotation about an axis lying in or substantially in said common plane, the auxiliary member being positioned to overlap the front wheels when viewed in a direction transverse to the direction of forward movement of the wheelchair and having an arcuate working surface which, as the wheelchair approaches a kerb, engages the kerb before the front wheels, the auxiliary member then being effective to lift the front of the wheelchair as the wheelchair advances to assist the wheelchair to negotiate the kerb.

2. A wheelchair according to claim 1 wherein radial distance from the axis of rotation of the auxiliary member to the working surface thereof is greater than the radius of the front wheels, and wherein the axis of rotation of the auxiliary member is positioned such that when the wheelchair is standing on a planar surface, the auxiliary member is located out of contact with the surface.

3. A wheelchair according to claim 1 or claim 2 wherein the auxiliary member is readily removable from the remainder of the wheelchair. 203412 - j-e' -

4. A wheelchair according to any preceding claim wherein the auxiliary member is a wheel which overlaps the majority \of the front wheels, when viewed in a direction transverse to the direction of forward movement of the wheelchair.

5. A wheelchair according to any preceding claim wherein, when viewed in a direction transverse to the direction of forward movement, a shallow cusp is formed 10 by the overlapping working surfaces of the front wheels and of the auxiliary member.

6. A wheelchair according to any preceding claim wherein the axis \upon which the auxiliary member is 15 mounted is supported by a pair of support arms which are in turn supported by.the respective side frames of the wheelchair.

7° A wheelchair according to claim 6 wherein the 20 support arms are carried by a transverse main arm which is releasably connected to the side frames. 25

8. A wheelchair according to claim 7 wherein the transverse main arm is provided with two mounting and locating pins each adapted for engagement with a location opening provided in the adjacent one of side frames. 30

9. A wheelchair according to any preceding claim wherein the wheelchair includes footrests, and the auxiliary member does not project forwardly of the leading edge of the footrests. APR 1986

10. A wheelchair substantially as hereinbefore described with reference to the accompanying drawing. dated this&O^DAY oFpr^x A A. J. PARK & SON PER ; AGENTS FOR THE APPLICANTS 1*%