WHEELCHAIRS

Abstract: A wheelchair for handicapped or elederly persons consists of a seat supported by a generally rigid chassis or frame (242,243,244,248), the chassis or frame being sup­ ported on a pair of rear wheels (90) and front castor wheels (26). Each wheel is movable relative to the frame between an extended operative position and a retracted inoperative position. Each rear wheel (90) is rotatable about an axle (92) carried at the end of a respective swing arm (140) which rotates about a fixed stub axle (93) extending outwardly from a respective side (94, 95) of the sheet metal box structure (244). Each stub axle (93) is skewed rearwardly so that rotation of the swing arm (140) about the skew axis from a position in which the wheel axle 92 is horizontal not only skews the respective wheel (90) to the vertical to reduce the track width of the chair but also produces a rearward convergence or toeing-out, of the wheels. The chair is thus able to fit between the transmission tunnel and the door sill of a small, family sized motor vehicle, and the occupant of the chair is less hemmed-in by the tops of the wheels when these are in their raised, retracted positions.

Description: TITLE: WHEELCHAIRS In my copending UK application 80 04920 (2 069 969), I describe and claim a wheelchair for elderly or handicapped persons in which each wheel is transferable from an extended operative position to a retracted inoperative position. Accordingly, when the chair is lifted off the ground by a hoist mechanism fixed in a motor vehicle, the wheels can be retracted before the chair is swung through the door opening of the motor vehicle. The chair is then pivoted into its front facing position and lowered into a seated position. However, because the rear wheels and the associated retraction mechanism add significantly to the width of the chair, I have found that the distance between the transmission tunnel and the door sill in many small, family-sized, motor vehicles is not sufficient to accommodate the wheelchair described in the aforesaid application unless the seat is made uncomfortably narrow. An object of the present invention is to overcome this disadvantage. In accordance with the present invention I provide a wheelchair for handicapped or elderly persons comprising a seat supported by a generally rigid chassis or frame, the chassis or frame being supported on a pair of rear wheels and at least one front wheel, each wheel being movable relative to the frame between an extended operative position and a retracted inoperative position, and characterised by means responsive to the retraction of the two rear wheels into their inoperative positions for skewing the two wheels with respect to the vertical to reduce the track width of the chair. In a preferred arrangement each rear wheel is rotatable about an axle carried at the end of a respective swing arm which rotates about a fixed skew axis extending outwardly and rearwardly from a respective side of the frame. Accordingly rotation of the swing arm about the skew axis from a position in which the wheel axle is horizontal not only skews the respective wheel to the vertical to reduce the track width but produces a rearward convergence, or toeing-out, of the wheels. This has the advantage that the occupant of the wheelchair is less hemmed-in by the tops of the wheels when the wheels are in their raised, retracted positions. By way of example only, an embodiment of the invention will now be described with reference to the accompanying drawings in which: Fig. 1 is a side view of a wheelchair chassis showing the main components of a rear wheel retraction mechanism with the rear wheels in their lowered or extended position, Fig. 2 is a side view similar to that of Fig. 1 showing the rear wheels raised or retracted, Fig. 3 is a front elevation on line A-A of Fig. 1 showing one wheel lowered and the other raised, and, Fig. 4 is a plan view on line B-B of Fig. 1 showing the left hand set of wheels raised or retracted and the right hand wheels lowered or extended (as viewed by the wheelchair occupant). For the sake of clarity, the wheelchair seat has been omitted from the drawings but in general it will have the form shown in my aforesaid pending UK application 80 04920. The wheelchair has a generally rectangular rigid chassis or "box-like" frame formed of sheet metal but including an upright tubular rear frame 242,248, and a tubular front axle housing 243 welded to the sheet metal structure 244. When the rear wheels 90 and front castor wheels 26 are in their lowered or extended position as shown in Fig. 1, the weight of the chair is transmitted to the wheels from a pair of brackets 245 secured at the top of respective upright members 248 of the rear frame, the weight being transmitted via respective rubber suspension springs 210 carried by vertical rods 246. The top of each rod 246 is permitted to move up and down through a hole in the respective bracket 245, and the movement of the rod 246 is controlled at the bottom by a wishbone link 220 via a pivot pin 241, the wishbone links 220 having their fulcrum at respective bearings 247 welded to the rear of the upright frame members 248 of the rear tubular frame. This arrangement improves the operation of the suspension system by reducing the angular movement of the wishbone 220. The load is transferred from the pivot pins 241 to respective linkages each consisting of two links 180 and 190 held in an overcentre position by a spring 97 connected between the centre point of the two links and a respective rear wheel axle 92. The bottom end of link 180 is pivoted on a plate 181 welded to a swing arm 140 which carries the respective rear wheel axle 92. The rear wheels 90 normally rotate about a substantially horizontal axis 91, each wheel being mounted for rotation about the respective axle 92 at one end of the swing link arm 140. The other end of each arm 140 has a hub 141 which receives a respective stub axle 93 extending outwardly from the respective sides 94, 95 of the sheet metal box structure 244 at an angle e to the central longitudinal axis 96 in the plan view of Fig. 4. Each stub axle 93 is thus non-perpendicular, or skewed rearwardly, with respect to the side of the frame, but lies in a horizontal plane. Solidly fixed to each link 190 is a respective lever 250 which operates the retraction mechanism for the rear wheels. Downward rotation of each lever 250 from its position shown in Fig. I to its position shown in Fig. 2 rotates the respective link 190 about pivot axis 241 so that the links 190, 180 and 140 are moved against the bias of spring 97 from their extended over-centre configuration of Fig 1 to their folded or retracted Fig. 2 configuration. Due to the rearward skew of the stub axles 93, the angle of each wheel axle 92 with respect to the frame changes in both plan and elevation when the wheels are retracted. The change in elevation means that the wheel axles are no longer horizontal when the wheels are retracted, as can be seen by comparing the left and right hand sides of Fig. 3. In the retracted position the wheels will converge downwardly toward one another as shown on the right hand side of Fig. 3. The change in plan is illustrated by comparing the left and right hand sides of Fig. 4. As shown, the wheels 90 are toed-out at an angle OC to the longitudinal axis 96 when the wheels are retracted. This downward convergence and toeing-out of the retracted rear wheels allows the chair to fit more easily between the door sill and the central transmission tunnel of a motor vehicle without reducing the width of the seat, and without the top of each wheel impeding the thighs of an occupant seated in the chair. Each rear wheel 90 is independently retractable by operating a respective lever 250, each wheel having its own set of links 140, 180 and 190. Each lever 250 is bolted to its respective link 190 as shown most clearly on the left hand side of Fig. 3. Alternatively, links 190 may be interconnected and operated by a single lever 250. The front wheels 26 are each mounted for rotation between the arms of a fork 260, the fork being rotatable about the axis of a castor spindle 270 which can be released for rotation about the axis 271 of the tubular front axle housing 243 to permit retraction of the front castor wheel from its extended position shown in Fig. 1 to its retracted position shown in Fig. 2.

Claims: CLAIMS 1. A wheelchair for handicapped or elderly persons comprising a seat supported by a generally rigid chassis or frame, the chassis or frame being supported on a pair of rear wheels and at least one front wheel, each wheel being movable relative to the frame between an extended operative position and a retracted inoperative position, and characterised by means responsive to the retraction of the two rear wheels into their inoperative positions for skewing the two wheels with respect to the vertical to reduce the track width of the chair. 2. A wheelchair according to claim 1 further characterised in that the skewing means includes a pair of swing arms, one end of each swing arm carrying a respective rear wheel axle, and the other end of each swing arm being rotatable about a fixed skew axis extending outwardly from a respective side of the frame. 3. A wheelchair according to claim 2 in which each skew axis extends outwardly and rearwardly from a central portion of the respective side of the frame, the respective rear wheel axles being horizontal when the swing arm is in its extended operative position whereby rotation of the arm about the skew axis not only skews the respective wheels inwardly toward one another but also produces a rearward convergence, or toeing-out, of the wheels. 4. A wheelchair according to claim 2 or claim 3 in which each swing arm is held in its extended operative position by a respective spring-biased overcentre linkage mechanism. 5. A wheelchair according to claim 4 in which the chassis includes a tubular generally rectangular rear frame welded to an open box-like sheet metal structure, and in which each rear wheel includes an independent suspension mechanism, the suspension mechanism including a wishbone link having its fulcrum located at a fixed point rearwardly of respective upright members of the rear frame and a pivot axis disposed forwardly of the rear frame, one end of the said linkage mechanism being pivotable about the pivot axis and the other end of the linkage mechanism being connected to the swing arm. 6. A wheelchair substantially as herein described with reference to the accompanying drawings.

Inventors: WAITE, BRIAN
Applicants: WAITE, BRIAN
Application year: 1982
Main classification: A61G5
IPC codes: A61G5, A61G3