CA1241901A

CA1241901A - Wheelchair

Info

Publication number: CA1241901A
Application number: CA000475195A
Authority: CA
Inventors: Hugh W. Barclay
Original assignee: Hugh W. Barclay; Advanced Mobility Systems Corporation
Current assignee: Advanced Mobility Systems Corp
Priority date: 1985-02-26
Filing date: 1985-02-26
Publication date: 1988-09-13

Abstract

ABSTRACT OF THE DISCLOSURE

A lightweight, relatively simple wheelchair is described in which the length of the wheelbase may be adjusted as required to suit individual users, by moving the rear wheels on the side frame members of the chair relative to the front wheels. The seat is mounted on a central post which is in turn mounted on a transverse member which is movable in a fore and aft direction between the front and rear wheels, to facilitate relative weight distribution between the front and rear wheels regardless of the length of wheelbase. The transverse member may be a rigid member or foldable.

Description

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BACKGROUND _ INVENTION
This invention relates to a wheelchair for the transportation of disabled persons. More particularly this invention relates to a lightweight wheelchair the balance of which can be adjusted to suit a particular individual. In a preferred embodiment the wheelchair is also collapsible.
Wheelchairs are, of course, well known in the art and numerous modifications and improvements therefor have been described over the years. It is known that the balance of a wheelchair with the disabled person seated therein is a critical factor to the ease of moving and manoevering the ¢hair, and many ways of adjusting the fore-and-aft spacing between the oonventionally small front wheels of the chair and the large rear wheels have been suggested. Cenerally such adjustment is provided by making elther the front or rear wheels movable relative to the 8ide frame members of the chair itself or making the seat movable fore and aft relative to the side frame members and front and rear wheels which are in fixed relation to each other. While this approach i8 satisfactory in certain instances and within certain 11m1ts, it will be appreciated that merely shortening or lengthening the wheelbase is not always sufficient or suitable for the various uses to which the chair may be put. One of the most serious disadvantages of adjusting the wheelbase is that the oooupant's weight may not be dlstributed in the most efficient way between the front and rear wheels. When the wheelbase is shortened, the critical tipping angle is reduced, and the safety .

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ol the user is put at risk. Shortening the wheelbase reduces the turning moment which exists between the contact surface of the rear wheel, which is essentially the fulcrum, and the contact surface of the opposite caster wheel. Shortening the wheelbase also places a higher proportion of the weight over the large rear wheels and lets over the small front wheels which is a significant factor in reducing turning and rolling inertia. When only the seat is moved fore and aft, the weight distribution is affected. If too much weight is located on the front wheels the chalr is difficult to manoevre and if too much weight is located on the rear wheels the chair is unstable. It is, therefore, desirable that it be possible to adjust both the length of the wheelbase and also the relationship of the centre of gravity of the occupant relative to the front and/or rear wheels. It is alto deslrable that the wheelchair be collapsible to facilitate transport by car or van from one location to another. Heretofore it has not been possible to achieve all these desirable characterlstics in a single chair design.
OBJECTS _ INVENTION.
It i9 therefore an object of the present invention to overcome the disadvantages of the prior art and provide a wheelchair construction which permits variation of the length of the wheelbase and variation of the centre of gravity of the occupant relative to the wheelbase.
It is another object of the invention to provide a wheelchair which is collapsible for transportation.
BRIEF DESCRIPTION OF INVENTION.
In satisfaction of the above objects, there is provided, by , ....

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one aspect of this invention a wheelchair assembly comprising:
a pair of parallel transversely spaced, longitudinally extending, frame members;
a first wheel pivotally mounted about a vertical axis at one end of each of said frame members, for rotation about a horizontal axis;
a second wheel adjustably mounted for rotation about a horizontal axis it a selected position remote from said first wheel on each of said frame members;
transverse seat support means adjustably mounted between said pair of parallel frame members at a selected position between said first and second wheels on each said frame member; and seat msans mounted on said transverse seat support means intermediate the ends thereof.
By another aspect of this invention there is provided a wheelchair as described above but which is also collapsible.
BRIEF DESCRIPTION OF DRAWINGS.
Flg. 1 is a side view of a preferred folding embodiment of the invention without a seat;
Fig. 2 is a plan view of the embodiment of Fig.1;
Fig. 3 is a front view of the embodiment of Fig.1 taken through line 111-111 in Fig. 2.
Fig. 3a is an isometric view of the folding members of Fig. 3.
Fig.4 is a side view of the embodiment of Fig.1 with a seat installed;
Fig.5 is a front view of an alternative non-folding wheelchair according to the invention; and . .

~2~g~1 Fig.6 is a side view of yet another alternative embodiment showing an alternative footrest arrangement.
DETAILED DESCRIPTION OF INVENTION.
In the embodiment shown in Figs. 1-4, there are provided a pair of parallel spaced side frame members 1,2 generally, but not essentially, of rectangular tubular cross-section. The forward end of frame members 1,2 terminate with a sleeve bushing 3,4 each adapted to rotatably receive a vertically oriented front wheel post 5 which, in turn, i8 provided with a substantially vertical U-shaped member 6 having a horizontal axle 7 between the arms thereof, arranged to carry a freely rotatable front wheel 8, in conventional manner. Rear wheel bosses 9,10 are mounted on frame members 2,1 respectively and clamped in a selected position therealong by means of a clamping plate 11 and screws 12. It will of oour~e be appreciated that the position of bosses 9,10 can be moved to, and clamped at, any selected position along members 1,2 thereby adjusting the length of the wheelbase of the wheelchair.
Each of bosses 9,10 is adapted to receive a horizontal stub axle 13,14 in transverse axial alignment with each other on which a conventional, relatively large, rear wheel 15,16 may be mounted for rotation in conventional manner.
Intermediate the front and rear wheels a seat cross member 17 i9 clampingly transversely secured, at any selected position, between parallel slde frame members 1,2. In the embodiment shown in Flgs. 2,3 cross member 17 is a folding cross member comprising members 18,19,20 and 21 pivoted at each end thereof, about a horizontal axis, to a respective inner frame clamping plate 22,23 and to the central seat boss 24. Clamping plates 22,23 are ~4~9~

clampingly secured, at any selected position, to respective side frame members 1,2 by means ox outer clamping plates 25,26 and bolts 27.
Seat boqs 24 is provided with a central bore 28 having a vertical axis arranged to receive a vertical seat post 29 (as shown in Fig.4). Bore 28 and post 29 may be threaded in complementary manner so that the height of seat 30 centrally mounted on post 29 may be adjusted in the same manner as a conventional office chair, if desired. Boss 24 is retained in a plane above that of clamps 22,23 when the chair is in the open or extended position by means of tops located at the ends of the parallel links 18, 19, 20,21. In the folded position, side frame members l are moved into close juxtaposition as boss 24 is raised to the maximum extent.
It will, of course, be appreciated that the present invention is capable of numerous embodiments without departing from the scope of the invention. For example, the seat 30 may be provided with a back 32 and arm rests 33. Foot rests 34 may be mounted from side frames 1,2 as shown in Fig.4 or foot rests 35 may be mounted from seat 30 as shown in Fig.6. Seat 30 may be provided with a fore-and-aft tilting mechanism to keep the seat substantially horizontal regardless of the terrain beneath the ohair, which may be manually operated and spring assisted as in a conventional office chair or which may be power operated by eleotrlc or hydraulic motor or even by means of a gas strut.
Wheels 15,16 may be provided with manipulating rims 36 in conventional manner, and similarly a push handle 37 may be f ~.~4~901.
lacked to either chair back 32 (as shown in Fig.4) or via frame members 1,2 (as shown in Fig.6).
In the embodiment shown in Fig.5, a fixed cross member 38 is provided in place of pivoting members 18,19,20 and 21 so that the chair is not folding but is rather more rigid in construction.
Cross member 38 is provided with a central vertical bore 28 to receive the seat post 29 as in the previous embodiment.
It will also be appreciated that wheelbos~es 9,10 may be located either above the side frame members as shown in Fig.1 or below the side frame members as shown in Fig.4. The side frame members may, of course, be used either way up so as to accomodate differently sized wheels as desired and as illustrated in Figs 4 and 6. Other modifications without departing from the scope of this invention will readily suggest themselves to those skilled in the art.

Claims

I CLAIM.

1. A wheelchair assembly comprising:
a pair of parallel transversely spaced, longitudinally extending, frame members;
a first wheel pivotally mounted about a vertical axis at one end of each of said frame members, for rotation about a horizontal axis;
a second wheel adjustably mounted for rotation about a horizontal axis at a selected position remote from said first wheel on each of said frame members;
transversely extending seat support means adjustably mounted at each end thereof on a respective one of said pair of parallel frame members for movement therealong between selected operating positions between said first and second wheels on the respective frame members; and seat means mounted on said transverse seat support means intermediate the ends thereof.

2. A wheelchair assembly as claimed in claim 1 wherein said transverse seat support means comprises a rigid transverse member extending between said pair of frame members.

3. A wheelchair assembly as claimed in claim 1 wherein said transverse seat support means comprises a plurality of pivotally inter-connected members pivotally connected at a respective end thereof to a said frame member; means in a central said inter-connected member to receive said seat means; and means to retain said central interconnected member in a plane above that of said respective ends.

4. A wheelchair assembly as claimed in claim 3 wherein said retaining means comprises stop means at the ends of said inter-connected members.

5. A wheelchair assembly as claimed in claim 1 wherein said seat means is rotatably mounted on said support means.

6. A wheelchair assembly as claimed in claim 5 including means to tilt said seat means relative to said frame members.

7. A wheelchair assembly as claimed in claim 1 including foot rest means.

8. A wheelchair assembly as claimed in claim 1 wherein said foot rest means are secured to said seat means.

9. A wheelchair assembly as claimed in claim 1 wherein said foot rest means are secured to said frame members.

10. A wheelchair assembly as claimed in claim 1 including push handle means.

11. A wheelchair assembly as claimed in claim 10 wherein said push handle means are secured to said seat means.

12. A wheelchair assembly as claimed in claim 10 wherein said push handle means are secured to said frame members.