Patent Description:
It is known for some wheelchair users to have muscular spasms when travelling over bumps or an uneven surface generally. These are a reflex response to vibrations running up through the chair to the occupant. As a result the occupant may thrash their body, putting strain on the chair and therefore cause premature wear and tear. Further, some wheelchair users are known to forcefully bang their heads against the wheelchair's backrest, or push their feet against the wheelchair's foot rests and drive their back into the backrest. These movements also cause undue strain on the wheelchair and premature wear and tear.

Document <CIT> discloses a wheelchair formed of a frame, two pairs of support wheels for the frame, and a seat portion rockably connected to the frame and normally maintained in a generally horizontal alignment when the chair is unoccupied by bias springs that permit the seat to rock about its rockable connection while the frame and wheels of the chair are completely stationary.

Document <CIT> describes a wheelchair comprising an upper frame and a lower frame, both frames being attached to each other by hinges in the front and springs in the back. This configuration allows for the two frame parts to be securely attached to each other, while the upper frame can move in a rocking manner, pivoting on the front hinges and dampened by the shock-absorbing effect of the rear springs. This allows for a smoother ride for the user over rough terrain or high speeds.

Document <CIT> discloses a wheelchair having a framework with side rails forming handles at their upper ends and curved forward at their lower ends to receive the front legs. The seat or back or both are pivoted so that the occupant may retain an upright position when the chair frame is tilted, e.g. in wheeling up or down stairs. A seat with interconnected back and leg-rests is described, and a segmental bar y and set screw w may be embodied to retain the chair in any adjusted position.

It is an object of preferred embodiments of the invention to go some way towards addressing the above problem. While this applies to preferred embodiments, it should be understood that the object of the invention per se is simply to provide the public with a useful choice. Therefore, any objects, advantages or benefits applicable to preferred embodiments should not be taken as a limitation, the invention being defined by the appended claims.

wherein the suspension is configured such that, when a human occupant seats on the seat base, the suspension allows a movement of the seat base with respect to the support frame, so that the suspension dampens a body weight force between the seat base and the support frame;.

Optionally the seat base is detachably fitted to the support frame.

Optionally a plurality of clamps are fitted to the support frame, at least some of which have locking levers that pivot to lock the base on the frame.

Optionally wherein the seat base includes at least one rear saddle, at least two connector tabs and at least one front saddle, all engaged with the support frame.

Optionally each connector tab has a pin that engages a slot of corresponding clamp that is in turn secured to the frame.

Optionally the front saddle is substantially rigid to limit the movement of the seat base.

Optionally the rear saddle is resilient such that at least the rear of the seat base can move up and down on the rear saddle with respect to the support frame.

Optionally the backrest is also secured to the support frame (directly or indirectly) by a damper at each side, each damper comprising a piston that retards recline of the backrest to absorb bodyweight or muscle generated wear and tear force on the frame as the backrest moves to a recline position.

Optionally in each case the damper comprises a spring that tensions when the backrest moves to the recline position to retard the recline.

Optionally in each case the damper comprises a housing around the piston, the housing being adapted to move back and forward with respect to the piston when the backrest reclines and subsequently moves to a non-reclined position.

Optionally in each case the piston comprises a pin outside the housing, arranged such that the pin engages a clamp that in turn secures the damper to the support frame.

Optionally each case the piston's pin has been slid into an upwardly opening track.

Some preferred embodiments of the invention will now be described by way of example and with reference to accompanying drawings, of which:.

Referring to <FIG>, the wheel chair <NUM> has a pair of large rear wheels <NUM>, a pair of smaller swivelling front wheels <NUM>, a support frame comprising a backrest frame <NUM> and a seat frame <NUM>. These frames <NUM>,<NUM> may or may not be integral. The wheels engage the support frame; they connect to it directly. As shown, the backrest frame <NUM> has a pair of spaced uprights <NUM> that turn over at their upper end to provide handles <NUM>. The uprights <NUM> support a plate like backrest <NUM>.

Each upright <NUM> is fitted with an upper clamp <NUM> and a lower clamp <NUM>, and each side of the backrest <NUM> is fitted with upper and lower L-brackets <NUM>, <NUM>. Each upper clamp <NUM> is rigidly but adjustably connected to the frame <NUM>, and each upper bracket <NUM> is rigidly but adjustably connected to the backrest <NUM>. Both are connected to a damper <NUM>. Further, each lower clamp <NUM> is rigidly but adjustably connected to the frame <NUM>, and each lower L-bracket <NUM> is rigidly but adjustably connected to the backrest <NUM>. As shown, each lower clamp <NUM> is connected to a corresponding one of the lower L-brackets <NUM> by way of a lever set <NUM>.

Referring to <FIG>, each lever set <NUM> comprises an inside lever arm <NUM> and an outside lever arm <NUM>. The top of each inside lever arm <NUM> is rigidly but adjustably fixed to a respective lower L- bracket <NUM> by bolts <NUM>. The top of each outside bracket is fixed to a respective lower clamp <NUM> (the clamps <NUM> are shown in <FIG>) by one or more pins, the position of which is indicated at labels <NUM> and <NUM>. The lever arms <NUM>, <NUM> are connected to one another at their lower end by pivot pin <NUM>. The arrangement is such that at least one or other of the levers <NUM>, <NUM> can pivot about the pin <NUM> with respect to the other.

Still with <FIG>, each damper's housing <NUM> is rigidly but adjustably fixed to the corresponding upper L-bracket <NUM> by bolts <NUM>. In each case the damper <NUM> also has a piston <NUM>, an end of which extends from the housing <NUM> to attach to a corresponding upper clamp <NUM> (the clamps <NUM> are shown in <FIG>).

<FIG> illustrates detail of the internal parts of the damper <NUM>. When the damper is at rest, most of the piston <NUM> resides within the housing <NUM>. However, when in use the housing <NUM> can be forced by backwards movement of the backrest to move along the piston (to the left in the drawing) to expose more of the piston <NUM>. As this happens a spring <NUM> within the housing, i.e. acting between the housing and piston, is put under tension to retard or cushion backwards movement of the backrest. This tension serves to return the damper housing <NUM> to its original resting disposition when the force acting against the spring is relaxed.

With further reference to <FIG>, the damper <NUM> has an internal stopper <NUM> at one end of the housing. The arrangement is such that the spring bears against the stopper, but more so when put under tension. The other end of the spring bears against an internal support <NUM> arranged near the opposite end of the housing <NUM>. The support <NUM> helps keep the piston <NUM> and spring <NUM> in position within the housing. The support <NUM> moves with the housing to compress the spring between the support and the stopper <NUM>. As also shown, the piston incorporates a pin <NUM> and it is this that serves to attach the damper to the upper clamp <NUM> (again, the clamps <NUM> are shown in <FIG>).

When in use the housing <NUM> around the piston <NUM> moves forwards and backwards in response to bodyweight or muscle driven force from the wheelchair user against the backrest <NUM>. The spring <NUM> compresses as the piston <NUM> becomes more exposed, but returns into its original disposition once the force is relaxed. This reduces the stress impact caused by forceful body movements by the seat user. As the housing <NUM> moves forwards and backwards, the pin <NUM> is able to move up and down slightly in the associated upper clamp <NUM>, which helps reduce stress on the backrest frame <NUM>.

Referring again to <FIG>, when the back rest reclines in use, the inner lever arm <NUM> in each case pivots with respect to the outer lever arm <NUM>. The lever arms <NUM>, <NUM> are placed at or near the bottom of the backrest support <NUM> so that at the bottom of the backrest, movement is primarily only a recline motion, i.e. as opposed to the more significant swinging motion at the top of the backrest. This limited movement near the seat base prevents or reduces movement of the occupant's pelvis. This assists in keeping the occupant safely within the seat. In some embodiments the lever arms <NUM>, <NUM> may have a spring acting between them to help reduce stress on at least the backrest frame <NUM>.

Preferably both sides of the back rest <NUM> are connected to the backrest frame <NUM> in the same way. The lever arms <NUM>, <NUM> working in association with the dampers <NUM> enable the occupant to have a smoother ride and to reduce wear and tear on the wheelchair. Further, when the wheelchair is in use and the weight of the person is shifting forwards and backwards, the backrest <NUM> moves, automatically, in sympathy with this to a limited extent.

<FIG> gives more detail of the relationship between the damper <NUM> and the backrest <NUM>. In each case the bolts <NUM> are secured within slots <NUM> of the L- brackets <NUM>. The piston <NUM> sits partially within the housing <NUM> with the pin <NUM> outside the housing. The spring <NUM> is shown at rest with the stopper <NUM> spaced from the support <NUM>.

Referring to <FIG>, the wheel chair's seat frame <NUM> has a horizontal bar <NUM> at each side, and these support a plate like seat base <NUM>. More specifically, the base <NUM> engages the frame <NUM> by way of a front saddle <NUM> at each side, a connector tab <NUM> at each side, a rear saddle <NUM> at each side and a clamp <NUM> at each side. Each tab <NUM> engages a corresponding one of the clamps <NUM>.

<FIG> provides further detail of the way the seat base <NUM> fits to the frame <NUM>. The clamps <NUM> are releasably attached to the horizontal bars <NUM> and the front and rear saddles <NUM>, <NUM> sit on those bars <NUM>. To facilitate a snug fit, the saddles <NUM>, <NUM> have a curved recess complimentary to, and that engages, the bars <NUM>. The front saddles <NUM> are preferably made of a hard non-metallic synthetic material, for example Nylon, while the rear saddles <NUM> are preferably made of a softer more cushioning material such as rubber. The front saddles <NUM> resist movement of the seat base <NUM>, and the rear saddles <NUM> are able to resiliently compress under downward force to provide a dampening or cushioning effect with respect to the frame <NUM> when someone sits on the base <NUM>. Put another way, the rear saddles <NUM> provide for suspension between the seat base <NUM> and the seat frame <NUM>.

Still with <FIG>, Each connector tab <NUM> has an inwardly extending pin <NUM> that slides into a vertical slot <NUM> forming part of corresponding seat clamp <NUM> (the inward extension of the pin <NUM> is not visible for the tab in the foreground of the drawing). As the pin <NUM> moves to the bottom of the slot it pushes against a pivoting locking lever <NUM>, displacing it as it passes. The locking lever <NUM> is weighted to then pivot-return under gravity to its original position blocking the slot <NUM>. This serves to retain the pin <NUM> in the slot, and therefore the seat base <NUM> with respect to the frame <NUM>. To release the pin <NUM> from the slot <NUM>, the lever <NUM> can be pivoted out of the way of the pin <NUM> by hand, and the pin <NUM> then raised up out of the slot. In each case, when sitting at the bottom of the slot <NUM>, the pin <NUM> has a little up and down and side to side give, to accommodate compression movement at the rear saddles <NUM>.

<FIG> illustrates further detail for the seat base <NUM> and related parts prior to installation on the seat frame <NUM>.

<FIG> illustrates the way the upper clamps <NUM> engage the backrest frame <NUM> in more detail. In this regard each clamp <NUM> has resilient jaws <NUM> that wrap around one of the uprights <NUM> and can be tightened by bolts between the jaws (not shown). The clamp <NUM> incorporates a short-track rail <NUM> with a slot <NUM> that receives and retains the pin <NUM> of the piston (see <FIG> and <FIG> for the pin <NUM>). While retained in the rail <NUM>, the piston pin <NUM> can slide up and down a little to provide a little give and reduce occupant body-movement generated strain on the frame <NUM>.

<FIG> illustrates detail of how the lower clamps <NUM> engage with the backrest frame <NUM>. Each clamp <NUM> has resilient jaws <NUM> that clip onto a frame upright <NUM> and may be tightened by a bolt (not shown) between the jaws. The clamp <NUM> incorporates a short-track rail <NUM> with an upright slot <NUM>, and a locking lever <NUM>. The arrangement is such that in each case the pin <NUM> of the outside lever arm <NUM> (see <FIG>) slides down into the slot <NUM>. As it does this it pushes against the locking lever <NUM> causing it to pivot out the way. When the pin is below the lever <NUM> the lever pivots back under gravity to block the slot <NUM> and lock in the pin <NUM>. The lever <NUM> can be subsequently moved out of the way by hand to enable the pin <NUM> to be released from the clamp <NUM>. If the outer lever arm <NUM> has two of the pins <NUM>, <NUM> (see <FIG>) then they may both be below the locking lever when it closes the slot <NUM>.

In some embodiments of the invention the dampers <NUM> may be replaced by spring cushioning lever sets the same or similar to those described above, although the dampers are the preferred option.

Claim 1:
A wheelchair (<NUM>) comprising
• wheels (<NUM>, <NUM>);
• a support frame (<NUM>, <NUM>) that engages with the wheels;
• a seat base (<NUM>) fitted to the frame (<NUM>, <NUM>); and
• a suspension between the support frame (<NUM>, <NUM>) and the seat base (<NUM>);
wherein the suspension is configured such that, when a human occupant seats on the seat base (<NUM>), the suspension allows a movement of the seat base (<NUM>) with respect to the support frame (<NUM>,<NUM>), so that the suspension dampens a body weight force between the seat base (<NUM>) and the support frame (<NUM>, <NUM>);
• a backrest (<NUM>) that is secured to the frame by way of a set (<NUM>) of lever arms (<NUM>, <NUM>) at each side, each set (<NUM>) comprising one lever arm (<NUM>) secured to the backrest (<NUM>) and another lever arm (<NUM>) secured to the support frame (<NUM>, <NUM>), for each set (<NUM>) at least one of the lever arms (<NUM>, <NUM>) is configured to pivot with respect to the other (<NUM>, <NUM>) to enable adjustment of incline of the backrest (<NUM>) when an occupant of the seat presses their back against the backrest (<NUM>);
wherein for each set (<NUM>) one of the lever arms (<NUM>) is secured to the backrest (<NUM>) by way of a bracket (<NUM>) and the other (<NUM>) is secured to the support frame (<NUM>, <NUM>) by way of a clamp (<NUM>).