Wheelchair

A wheelchair is described herein, including wheels, a support frame that engages with the wheels, a seat base fitted to the support frame, and suspension between the frame and the seat base, wherein the seat base is adapted to move with respect to the support frame when a human occupant is seated on the seat base such that the suspension dampens body weight force between the seat base and the support frame.

FIELD

The present teaching relates to a wheelchair incorporating suspension.

BACKGROUND

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.

OBJECT

It is an object of aspects of the present teaching to go some way towards addressing the above problem. While this applies to certain aspects, it should be understood that the object of the present teaching per se is simply to provide the public with a useful choice. Therefore, any objects, advantages or benefits applicable to present teaching should not be taken as a limitation on any claim expressed more broadly.

SUMMARY

A wheelchair comprisingwheels;a support frame that engages with wheels;a seat base fitted to the frame; andsuspension between the frame and base;

characterised in that the base is adapted to move with respect to the frame when a human occupant is seated on the base such that the suspension dampens body weight force between the base and 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 a backrest is secured to the frame by way of a set of lever arms at each side, each set comprising one lever arm secured to the back rest (directly or indirectly) and another lever arm secured to the frame (directly or indirectly), for each set at least one of the lever arms is adapted to pivot with respect to the other to enable adjustment of incline of the backrest when an occupant of the seat presses their back against the backrest.

Optionally for each set one of the lever arms is fastened to the backrest by way of a bracket and the other is fastened to the support frame by way of a clamp.

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

DETAILED DESCRIPTION

Referring toFIG.1, the wheel chair1has a pair of large rear wheels2, a pair of smaller swivelling front wheels3, a support frame comprising a backrest frame4and a seat frame5. These frames4,5may or may not be integral. The wheels engage the support frame; they connect to it directly. As shown, the backrest frame4has a pair of spaced uprights6that turn over at their upper end to provide handles7. The uprights6support a plate like backrest8.

Each upright6is fitted with an upper clamp9and a lower clamp10, and each side of the backrest8is fitted with upper and lower L-brackets11,12. Each upper clamp9is rigidly but adjustably connected to the frame4, and each upper bracket11is rigidly but adjustably connected to the backrest8. Both are connected to a damper13. Further, each lower clamp10is rigidly but adjustably connected to the frame4, and each lower L-bracket12is rigidly but adjustably connected to the backrest8. As shown, each lower clamp10is connected to a corresponding one of the lower L-brackets12by way of a lever set14.

Referring toFIG.2, each lever set14comprises an inside lever arm15and an outside lever arm16. The top of each inside lever arm15is rigidly but adjustably fixed to a respective lower L-bracket12by bolts19. The top of each outside bracket is fixed to a respective lower clamp10(the clamps10are shown inFIG.1) by one or more pins, the position of which is indicated at labels20and21. The lever arms15,16are connected to one another at their lower end by pivot pin17. The arrangement is such that at least one or other of the levers15,16can pivot about the pin17with respect to the other.

Still withFIG.2, each damper's housing18is rigidly but adjustably fixed to the corresponding upper L-bracket11by bolts22. In each case the damper13also has a piston24, an end of which extends from the housing18to attach to a corresponding upper clamp9(the clamps9are shown inFIG.1).

FIG.3illustrates detail of the internal parts of the damper13. When the damper is at rest, most of the piston24resides within the housing18. However, when in use the housing18can be forced by backwards movement of the backrest to move along the piston (to the left in the drawing) to expose more of the piston24. As this happens a spring25within 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 housing18to its original resting disposition when the force acting against the spring is relaxed.

With further reference toFIG.3, the damper13has an internal stopper26at 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 support27arranged near the opposite end of the housing18. The support27helps keep the piston24and spring25in position within the housing. The support27moves with the housing to compress the spring between the support and the stopper26. As also shown, the piston incorporates a pin28and it is this that serves to attach the damper to the upper clamp9(again, the clamps9are shown inFIG.1).

When in use the housing18around the piston24moves forwards and backwards in response to bodyweight or muscle driven force from the wheelchair user against the backrest8. The spring25compresses as the piston24becomes 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 housing18moves forwards and backwards, the pin28is able to move up and down slightly in the associated upper clamp9, which helps reduce stress on the backrest frame4.

Referring again toFIG.2, when the back rest reclines in use, the inner lever arm15in each case pivots with respect to the outer lever arm16. The lever arms15,16are placed at or near the bottom of the backrest support4so 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 arms15,16may have a spring acting between them to help reduce stress on at least the backrest frame4.

In one aspect of the present teaching, both sides of the back rest8are connected to the backrest frame4in the same way. The lever arms16,17working in association with the dampers13enable 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 backrest8moves, automatically, in sympathy with this to a limited extent.

FIG.4gives more detail of the relationship between the damper13and the backrest8. In each case the bolts22are secured within slots23of the L-brackets11. The piston24sits partially within the housing18with the pin28outside the housing. The spring25is shown at rest with the stopper26spaced from the support27.

Referring toFIG.5, the wheel chair's seat frame5has a horizontal bar29at each side, and these support a plate like seat base30. More specifically, the base30engages the frame5by way of a front saddle31at each side, a connector tab32at each side, a rear saddle33at each side and a clamp34at each side. Each tab32engages a corresponding one of the clamps34.

FIG.6provides further detail of the way the seat base30fits to the frame5. The clamps34are releasably attached to the horizontal bars29and the front and rear saddles31,33sit on those bars29. To facilitate a snug fit, the saddles31,33have a curved recess complimentary to, and that engages, the bars29. The front saddles31can be made of a hard non-metallic synthetic material, for example Nylon, while the rear saddles33can be made of a softer more cushioning material such as rubber. The front saddles31resist movement of the seat base30, and the rear saddles33are able to resiliently compress under downward force to provide a dampening or cushioning effect with respect to the frame5when someone sits on the base30. Put another way, the rear saddles33provide for suspension between the seat base30and the seat frame5.

Still withFIG.6, each connector tab32has an inwardly extending pin35that slides into a vertical slot36forming part of corresponding seat clamp34(the inward extension of the pin35is not visible for the tab32in the foreground of the drawing). As the pin35moves to the bottom of the slot36it pushes against a pivoting locking lever37, displacing it as it passes. The locking lever37is weighted to then pivot-return under gravity to its original position blocking the slot37. This serves to retain the pin35in the slot36, and therefore the seat base30with respect to the frame5. To release the pin35from the slot36, the lever37can be pivoted out of the way of the pin35by hand, and the pin35then raised up out of the slot36. In each case, when sitting at the bottom of the slot36, the pin35has a little up and down and side to side give, to accommodate compression movement at the rear saddles33.

FIG.7illustrates further detail for the seat base30and related parts prior to installation on the seat frame5.

FIG.8illustrates the way the upper clamps9engage the backrest frame4in more detail. In this regard each clamp9has resilient jaws38that wrap around one of the uprights6and can be tightened by bolts between the jaws (not shown). The clamp9incorporates a short-track rail39with a slot40that receives and retains the pin28of the piston (seeFIGS.2and3for the pin28). While retained in the rail39, the piston pin28can slide up and down a little to provide a little give and reduce occupant body-movement generated strain on the frame4.

FIG.9illustrates detail of how the lower clamps10engage with the backrest frame4. Each clamp10has resilient jaws41that clip onto a frame upright6and may be tightened by a bolt (not shown) between the jaws. The clamp10incorporates a short-track rail42with an upright slot43, and a locking lever44. The arrangement is such that in each case the pin20of the outside lever arm16(seeFIG.2) slides down into the slot43. As it does this it pushes against the locking lever44causing it to pivot out the way. When the pin is below the lever44the lever pivots back under gravity to block the slot43and lock in the pin20. The lever44can be subsequently moved out of the way by hand to enable the pin20to be released from the clamp10. If the outer lever arm16has two of the pins20,21(seeFIG.2) then they may both be below the locking lever when it closes the slot43.

In some aspects of the present teaching the dampers13may be replaced by spring cushioning lever sets the same or similar to those described above.

In terms of disclosure, this document hereby envisages each item, feature or step mentioned herein, in combination with one or more of any same or other item, feature or step disclosed herein, in each case regardless of whether the combination is claimed.