SUPPORT STRUT FOR A WHEELCHAIR

Abstract: An adjustable support strut (4), a wheelchair having said adjustable support strut (4) fitted to a back (1, 2, 3) thereof, and a method of supporting the back (1, 2, 3) of a wheelchair with a support strut (4) are provided whereby a support strut (4), telescopically adjustable for length, is located between two upwardly extending cantilever members (1) of the back (1, 2, 3) of the wheelchair separated by a flexible backrest (3) held in tension by the cantilever members (1), and the support strut (4) is then adjusted for length to brace the members (1, 2) with respect to each other and to tension the flexible backrest (3) as desired.

Description: SUPPORT STRUT FOR A WHEELCHAIR The present invention relates to apparatus and a method for tensioning the back of a wheelchair, and more particularly, although not exclusively, a collapsible wheelchair. Collapsible or folding wheelchairs are extremely common in use owing to their ability to be collapsed to a smaller size for storage and/or carriage in a vehicle. A problem which occurs with such collapsible wheelchairs arises because of the nature of construction of the back thereof. A typical construction of collapsible wheelchair has a back comprising two members extending upwardly from the seat area of the wheelchair approximately shoulder width apart, the members being unsupported at their top ends and each being provided with, or formed into, a handle for manoeuvering the wheelchair. Between these upwardly extending members is usually suspended one or more pieces of flexible material to form a backrest against which the occupant of the chair leans when seated. As the two upwardly extending members are cantilevers, suspended at the bottom ends only thereof, the force of a chair occupant leaning against the backrest of the wheelchair causes the flexible material to sag backwards and thus draw top portions of the upwardly extending members towards each other. Furthermore, the upwardly extending members, are often hinged in the region of, or slightly above, the seat of the wheelchair to provide further collapsibility. Such a hinged joint is rarely completely rigid when the wheelchair is in its extended position, and, in manoeuvring by the handles, considerable flexing of the upwardly extending members, and hence movement of the handles, has to date been a disadvantage of this type of wheelchair. This capability of movement of the upwardly extending members has a two-fold effect. Firstly, the sagging of the flexible material allows the torso of the chair occupant to move backwards between the upwardly extending members by up to about 4 cms, however the shoulders of the occupant tend to be prevented from so doing by -those members. Thus the occupant tends to adopt a hunched posture in the chair which can cause considerable discomfort and, more importantly, over a period of time can anatomically deform the occupant into a permanently hunched posture. Secondly, the above mentioned movement of the top ends of the upwardly extending members, and thus the handles, allied with a possible fore and aft movement of each upright member, especially when hinged can cause considerable potential fore and aft, side to side, and rotational movement of each handle relative to the body of the wheelchair, with a consequent loss of control. The rearwardly shifted position of a chair occupant in the chair, owing to the flexible material sagging, can also, in moving the centre of gravity of the chair and occupant, aggravate loss of control of the wheelchair caused by the handles flexing. Furthermore, this rearward shift of the centre of gravity moves the latter towards the rear axle of the wheelchair and thus decreases the stability of the wheelchair from the standpoint of tipping backwards. It is an object of the present invention to provide means to support the back of a wheelchair to prevent undue deflection thereof by an occupant of the wheelchair when seated and thus improve user comfort and improve steering and controlability of the wheelchair when manoeuvred by handles forming part of the back of the wheelchair. According to the present invention there is provided a support strut for the back of a wheelchair comprising telescopic length adjusting means, and locating means provided at each end adapted releasably to engage respective spaced members forming part of the back of a wheelchair to which the strut is applied. According to a second aspect of the present invention there is provided a wheelchair having a back support comprising a pair of spaced cantilever members each extending upwardly from support means at a lower end thereof, flexible material extending between the members to form a flexible backrest to the wheelchair, and a removable support strut comprising telescopic length adjusting means and locating means adapted releasably to engage the respective members, the strut being locatable between the members and between the flexible backrest and free ends of the members whereby to brace the members with respect to each other and adjustably tension the flexible backrest. According to a third aspect of the present invention there is provided a method for supporting the back of a wheelchair having a pair of spaced cantilever members each extending upwardly from support means at a lower end thereof and having flexible material extending between the members to form a flexible backrest to the wheelchair, the method comprising the steps of locating one end of an adjustable strut at or towards the free end of one of the pair of spaced members, locating the other end of the strut at or towards the free end of the other of the pair of spaced members, and adjusting the length of the strut so as to brace the pair of spaced members with respect to each other and tension the backrest as required. It will be appreciated that, with the strut in position between the members as described, telescopically adjusting the length of the strut in either direction will allow any desired tension of the flexible backrest to be achieved for the most comfortable posture of an occuoant of the wheelchair. The wheelchair may be collapsible and may comprise a handle on the free end of each upright member, and the strut may be positioned in use near to, or over, each handle. In this way, not only will the flexible backrest of the wheelchair be tensionable as desired, but a more rigid construction of the back of the wheelchair will result, enhancing to a very significant extent steerability of the wheelchair. In this regard the invention provides a surprising effect in as much as it was conceived only with occupant comfort in mind but has the added and important advantage of improving controllability. Enhanced steerability and more rigid construction of the back of the wheelchair with the strut fitted are a particularly important feature of the present invention on collapsible wheelchairs with hinged upwardly extending members. The handles of the wheelchair are normally approximately horizontal, and hence the upwardly extending members, in meeting the handles, normally describe a curve. In order to allow the most rigid location possible of the handles when using the strut, it will sometimes be desired to locate the strut actually on a grip of the handle, or on or near the curve of the members. Such a grip will usually fit over a tube comprising the upwardly extending member, and hence the grip and the member may be of different diameters. In order to accommodate this, the locating means of the strut may comprise flexible material so that snug and accurate location of the strut results in case of either method of fitting. Preferably the locating means are a press fit into position on the members, although the locating means may be adapted merely to abut the members being braced such that, by extension of the strut between the members into contact therewith, the strut becomes firmly located therebetween. The locating means - 5 - may comprise generally axially outwardly facing, open portions formed so as to partly embrace a member of the wheelchair upon engagement therewith. The preferred form of locating means comprises a circular clip of resilient material having a portion thereof cut away to allow a member of the wheelchair to be pressed into snug engagement within the circular confines of the clip. The member may be a snap fit into the locating means or the cut away may allow free movement of the member therethrough into engagement with the locating means. A light snap fit is preferred. Fitting of the strut to the wheelchair, particularly if the strut is to be engaged with horizontal portions of the upwardly extending members or with the handles, may be facilitated by the cutaway being assymetrically placed in the circle of the locating means with respect to the axis of the strut in order to allow the strut, when held horizontally, to be rested upon the members to be engaged, prior to engagement therewith, in order to assist location of the strut, and thereafter pressed downwardly into full engagement with the member. The strut may comprise means to attach the strut to the wheelchair when not in use, for example when the wheelchair is in a collapsed state during carriage, storage and the like. Said attachment means may comprise an eye or the like through which a piece of cord or wire or the like may be passed for attachment of the strut to the wheelchair. The eye may conveniently be incorporated into either or both locating means and where the locating means is of plastics material or other moulded material, the eye may conveniently comprise part of the moulding. The telescopically adjustable strut may work on a turnbuckle principle, whereby rotation of a rotatable element of the strut in relation to at least one axially movable element causes the length of the strut to be increased or decreased by movement of threaded parts - 6 - thereof in relation to one another and by the consequent axial movement of the at least one axially movable element. The pitch of thread may conveniently be selected to allow a combination of easy turning of a rotatable member of the strut during adjustment of the length of the strut under axial load on the one hand, and to allow relatively speedy adjustment of the length of the strut on the other hand. A preferred design of the strut incorporates an outer rotatable tube having threaded means within the confines of the tube. Preferably, rotation of the rotatable tube will effect rotation of two sets of co-operating threaded components being respectively left-hand and right-hand threaded. In this way, the strut may be extended or contracted twice as quickly for a given rotation of the rotatable member and a given pitch of thread as would be possible with an arrangement using only a single pair of co-operating threaded components. Also the higher frictional losses of a strut with two sets of co-operating threaded components provides a more stable strut which is less likely to twist, and hence extend or contract, when not desired. It is immaterial for purposes of the invention whether male threaded components of the strut are rotatable in co-operation with the outer rotatable tube, or whether female threaded components so rotate. The present invention will now be more particularly described, by way of example, with reference to a preferred embodiment thereof as shown in the accompanying drawings in which:- Figure 1 is a partial rear perspective view of a wheelchair with strut in accordance with the invention fitted thereto. Figure 2 is an exploded side view of -the strut, and Figure 3 is a side view of part of Figure 2. Referring to the drawings. Figure 1 shows the back of a wheelchair comprising two upwardly extending members 1, each terminating at its upper end in a handle 2 and each being in the form of a tube of circular cross section. Extended in tension between the upwardly extending members 1 is a backrest 3 of flexible material. Extending between the upwardly extending members 1, near to the handles 2, is a support strut 4 constructed in accordance with the present invention. The strut 4 comprises moulded resilient locating means 5 which may be of a semi-rigid material such as a rubber-based compound or a plastics material at either end thereof by which the strut is located between the members 1. Each member 1 is closely embraced by a part-circular member engaging portion comprising a resilient clip 6 of each locating means 5. Each member engaging portion 6 comprises a cutaway 7 through which the member 1 is introduced into engagement with the locating means 5. , Extending towards the centre of the strut 4 from locating means 5 are axially movable elements comprising tubes 8 to which are rigidly attached the locating means 5 and having left and right-hand female threaded portions 9 and 18, respectively, at the ends thereof nearest the centre of the strut 4. The threaded portions 9, 18 may be machined from the inner wall of tubes 8, or may be formed in separate inserts (not shown) shrunk or bonded into the tubes 8. The above mentioned components of the strut merely move axially of the strut upon adjustment thereof. The axial adjustment of the strut is effected by rotational movement of an inner rotatable member 10 and an outer rotatable tube 11 rigidly connected thereto. The outer rotatable tube 11 comprises a cover for that portion of the strut between the locating means 5, and hence is of an internal diameter slightly larger than the external diameter of the inner tubes 8 to allow rotational and axial movement therebetween. The outer tube 11 is provided at a central portion 12 thereof with a lightly knurled or ribbed portion for an easy hand grip in adjusting the strut. The inner rotatable member 10 comprises a male left-hand threaded portion 13 at one end and a male right-hand threaded portion 14 at the other end for engagement with co-operating the left-hand and right-hand threaded female portions 9 and 18 respectively. When assembled, the threaded portions 13, 14 of the inner rotatable member 10 will extend past the threaded portions 9, 18 into hollow body portions 15, 16 of the inner tubes 8 upon strut adjustment. A raised central portion 17 of the inner rotatable member 10 is adapted rigidly to engage the inner surface of the central portion 12 of the outer tube 11. This rigid engagement may be accomplished by means of an interference fit, by bonding or by any other suitable fastening method. For ease of manufacturing the inner rotatable member 10 when using light engineering equipment, the threaded portions 13, 14 may be manufactured separately from the raised central portion 17 and later attached thereto by suitable fastening means. Each locating means 5 is formed with an eye 19 to one of which can be attached a cord or the like (not shown) to attach the strut to the wheelchair when not in use either in a collapsed or normal condition. In use, the strut may be fitted and adjusted for the desired backrest tension by pressing one of the moulded locating means 5 into engagement with one of the upwardly-extending members 1 or one of the handles 2 of the wheelchair. The length of cutaway 7 of the tube engaging portion 6 is such that the tube-engaging portion 6 is a light snap fit over the member or handle engaged. The length of the strut may now be adjusted to enable the second locating means 5 to be engaged with the other member 1 or handle 2 on the other side of the wheelchair. Upon the second locating means 5 being fitted to the wheelchair, the tension of the backrest 3 may be adjusted to suit an occupant of the wheelchair by further extending or contracting the strut as appropriate. The length and adjustment of the strut is effected by rotating the outer tube 11, by finger adjustment thereof, with respect to those portions of the strut fixedly attached to the locating means 5. In this way the co-operating threads 9 and 13, 18 and 14 will drive the inner tubes 8 towards or away from each other, thus extending or contracting the strut. It will be appreciated that the cross-sectional shape of the members 1 of the wheelchair is immaterial, the shape of the locating means 5 merely being made complementary thereto. It will also be appreciated that the invention provides a method and apparatus of tensioning the backrest of a wheelchair which is extremely simply attached and removed and yet which measurably improves short-term occupant comfort and long-term occupant posture, as well as improving wheelchair steerability and controllability. The length adjustment of the strut is readily accomplished so that backrest tension is very easily adjusted both initially and during a period of wheelchair occupation. Furthermore, a given strut can be used for all sizes of wheelchair.

Claims: Claims 1. support strut (4) for the back of a wheelchair characterised in that it comprises telescopic length adjusting means (8, 10, 11) and locating means (5) provided at each end adapted releasably to engage respective spaced members (1, 2) forming part of the back of a wheelchair to which the strut is applied. 2. A support strut according to claim 1, characterised in that each locating means (5) is adapted to engage a spaced member (1, 2) of varying size. 3. A support strut according to claim 1 or 2, characterised in that each locating means (5) is of resilient material. 4. A support strut according to claim 1, 2 or 3, characterised in that each locating means (5) comprises a part-circular member-engaging portion (6) having a cutaway (7) therein for engagement of a spaced member (12) therethrough. 5. A support strut according to claim 4, characterised in that the member-engaging portion comprises a resilient clip (6) which is snap fit on the spaced member (1, 2) to be engaged. 6. A support strut according to claim 4 or 5 , characterised in that the cutaway (7) is asymmetrically placed in the member engaging portion (6) with respect to the axis of the strut (4). 7. A support strut according to any of the preceding claims, characterised in that the strut (4) comprises attachment means (19) adapted to allow the strut (4) to be attached to the wheelchair when the strut (4) is not in use . 8. A support strut according to claim 7, characterised in that the attachment means comprises an eye (19) or the like adapted to receive a piece of cord or the like. 9. A support strut according to claim 7 or 8, characterised in that the attachment means (19) comprises - 11 - part of a moulding comprising the locating means (5). 10. A support strut according to any of the preceding claims, charac erised in that the telescopic length adjusting means (9, 10, 11) comprises screw-threaded adjusting means (8, 10). 11. A support strut according to claim 10, characterised in that the screw-threaded adjusting means (8, 10) comprises co-operating left and right-hand threaded members (9 and 13, 8 and 14). 12. A support strut according to any of the preceding claims, characterised in that the telescopic length adjusting means comprises a rotatable member (10) and at least two axially movable members (8) co-operating therewit . 13. A support strut according to claim 12, characterised in that the rotatable member (10) comprises an outer tube (11). 14. A support strut according to claim 12 or 13, characterised in that the rotatable member (11) comprises a left and a right-hand male threaded portion (13, 14), one at either end thereof, threadably engageable with a female left or right-hand threaded portion (9, 18) in each axially movable member (8). 15. A support strut according to any of the preceding claims characterised in being adjustable to fit any size of wheelchair. 16. A wheelchair having a back support comprising a pair of spaced cantilever members (1) each extending upwardly from support means at a lower end thereof, and flexible material extending between the members (1) to form a flexible backrest (3) to the wheelchair, characterised in that the wheelchair further comprises a removable support strut (4) comprising telescopic length adjusting means (8, 10, 11) and locating means (5) adapted releasably to engage the respective members (1, 2), locatable between the members (1, 2) and between the flexible backrest (3) and free ends of the members (1, 2) whereby to brace the members (1, 2) with respect to each other and adjustably tension the flexible backrest (3). 17. A wheelchair according to claim 15 having a removable support strut (4) according to any of claims 1 to 15. 18. A method for supporting the back of a wheelchair having a pair of spaced cantilever members (1) each extending upwardly from support means at a lower end thereof and having flexible material extending between the members to form a flexible backrest (3) to the wheelchair, the method being characterised by comprising the steps of locating one end of an adjustable strut (4) at or towards the free end of one of the pair of spaced members (1, 2), locating the other end of the strut (4) at or towards the free end of the other of the pair of spaced members (1, 2), and adjusting the length of the strut (4) so as to brace the pair of spaced members (1, 2) with respect to each other and to tension the backrest (3) as required. 19. A method according to claim 17, comprising locating an adjustable strut (4) according to any of claims 1 to 15.

Inventors: FLANAGAN JOHN DAVID, MYRAM MAURICE, FLANAGAN, JOHN, DAVID, MYRAM, MAURICE
Applicants: FLANAGAN JOHN DAVID, MYRAM MAURICE, FLANAGAN, JOHN, DAVID, MYRAM, MAURICE
Application year: 1986
Main classification: A61G5
IPC codes: A61G5