GB2243289A

GB2243289A - A foldable seat

Info

Publication number: GB2243289A
Application number: GB9009595A
Authority: GB
Inventors: Stephen Griffiths; Sian Eleri Griffiths
Original assignee: MODSWITCH Ltd
Current assignee: MODSWITCH Ltd
Priority date: 1990-04-28
Filing date: 1990-04-28
Publication date: 1991-10-30
Anticipated expiration: 2010-04-28
Also published as: GB9009595D0; GB2243289B

Abstract

A foldable seat comprises a plurality of pairs of hinged plates (8) which are coupled together on a hinge axis (3), the plates (8) being pivotable about the hinge axis (3) between two extreme positions, in a first Fig 3, folded one of which the plates (8) lie substantially upright and the hinge axis (3) lies above the normal seat level, and in a second of which the hinged plates are all horizontal, the disposition of the hinge axis (3) relative to the plates (8) and the dimensions of the plates being such that the plates can not subtend between them an opening angle which is greater than 180 DEG , whereby the plane of the seat is prevented from dipping below the horizontal. Fig 8 illustrates a standard collapsible wheelchair fitted with the foldable seat. <IMAGE>

Description

DESCRIPTION A FOLDABLE SEAT The present invention relates to a foldable seat.

The majority of wheelchair seats which are currently available are made of canvas or a similar non-rigid material which is suspended from the wheelchair frame to form the seating position for the user of the wheelchair. A recognised failing of this type of seating is that it cannot be made rigid so as to offer the ideally required level of support.

The seat material is necessarily non-rigid because the seat needs to be capable of being folded as part of the wheelchair in its day-to-day use. The canvas or non-rigid seat also has a limited life span and requires renewing regularly. This type of seat is also difficult to keep hygienic for certain users.

Cushions are often used by wheelchair users for the purpose of pressure relief. Such cushions would be more effective if used on a solid level seat rather than on a canvas seat. On the other hand, wheelchairs fitted with solid seats are only foldable upon removal of the seat. The latter process will often require time-consuming removal of fixing screws with an appropriate tool, and thus increase the demands made of the wheelchair user or his/her helper, and reduce the desire to use a solid seat. The standard canvas seat has a number of drawbacks. Its useful life is limited because it is prone to wear and stretching. As it is easily contaminated it is unhygienic for the use of certain patients.When weight is applied to the canvas seat, a phenomenon known as "hammocking" tends to occur, where the seat dishes down to the point of greatest pressure, thus increasing the pressure on the buttocks and limbs of the user at this point. A cushion placed on such a surface will follow the hammocked contour which means that its pressure relief characteristics will be reduced. Hammocking may also be associated with contractures in amputees where the hips and thighs are held in flexion. There can also be an imbalance of sitting posture where the hammocking allows for leaning onto one side. This can cause discomfort to the user. A canvas seat also prevents movement of the lower limbs when they are weak or paralysed as they slide into the dished portion of the seat. This will often increase pressure at the knees or thighs.

It is an object of the present invention to provide a solid level foldable seat.

In accordance with a first aspect of the present invention, there is provided a solid level seat which is foldable on a collapsible seat frame, comprising two arrays of substantially rigid plates which are adjacently connected along a hinged folding axis adapted to permit the seat to be folded in one direction to a collapsed state and to be unfolded in the opposite direction to form a horizontal seating surface.

In accordance with a second aspect of the present invention, there is provided a foldable seat, comprising two hinged plates which are coupled together on a hinge axis, the plates being pivotable about the hinge axis between two extreme positions, in a first, folded one of which the plates lie substantially upright and the hinge axis lies above the normal seat level, and in a second of which the two hinged plates are both horizontal, the disposition of the hinge axis relative to the plates and the dimensions of the plates being such that the plates can not subtend between them an opening angle which is greatern than l8O, whereby the plane of the seat is prevented from dipping below the horizonta.

Advantageously, the plates are foldable by means of hinge fittings which are integral with the plates, each hinge fitting being interengageable with that of another plate.

The plates have upper and lower surfaces, with the upper surface forming the seating, the lower surface preferably being provided with ribbed protrusions which are disposed along axes parallel to that of the hinge axis.

Preferably, metal rods are threaded through said protrusions on the lower surfaces of the plates, for connecting the plates together, where necessary.

Advantageously, the foldable seat has means for attachment to the seat frame.

Preferably, the outer edges of the plates are connected to the seat frame via further hinges.

Advantageously, said further hinges are formed integrally with the plates.

Advantageously, a protrusion extends perpendicularly from the lower surface of each plate, near the end opposite that of the folding axis, so that in the folded position, the protrusions of opposing pairs of plates abut.

Advantageously, a foldable back rest of similar construction to the seat, which is also attachable to the foldable seat frame, is provided in addition to the seat.

By way of example only, a specific embodiment of the present invention will now be described with reference to the accompanying drawings, in which: Fig.l is a perspective view of a plate of a foldable seat in accordance with the present invention; Fig.2 is a perspective view from the rear of the plate in Fig.l; Fig.3 is a partial perspective view of a seat in a folded position; Fig.4 is an exploded perspective view of a seat in an unfolded position; Figs. 5a and 5b are cross-sections of a partially folded and a fully unfolded seat mounted on a wheelchair frame; and Fig.6 is a perspective view of a wheelchair incorporating a seat of the present invention.

Referring first to Fig.6 of the accompanying drawings, a seat 1 which is foldable along an axis 3 is attached to the horizontal side bars 19 of a conventional wheelchair seat frame 7.

The seat 1 comprises a plurality of generally rectangular plates 8 made of a relatively rigid plastics material, each of which has a hinge fitting 9 on one side, the fitting 9 extending below the lower surface 10 of the plate 8 (as viewed in Figs. 1 and 2). A plurality of the plates 8 are arranged adjacently to form a first array of plates 11, the length of which is determined by the required depth of the seat 1. The seat 1 further comprises a second, similar such plurality of the plates 8 forming a second array 12, the hinge fittings 14 of which are arranged to rotatably interengage with the hinge fittings 9 of the opposing array 11 along the axis.

Each hinge fitting 9,14 is provided with an axial bore through which a metal rod 15 is passed to define the hinge axis, the rod being common to the hinge fittings of both of the arrays 11 and 12. Further rods 16, disposed parallel to the metal rod 15, and hence to the hinge axis, pass through ribbed protrusions 17 in the lower surfaces of the plates 8 for adding strength to the plates 8.

The outer ends 5a,5b of the plates 8, remote from the hinge axis 3, are connected flexibly to the side bars 19a,19b or the wheelchair frame (see Fig.5).

This can be achieved by forming relatively thin regions 21 adjacent these outer ends of the plates, which permit flexing of the plates 8 about further hinge lines extending parallel to the main hinge axis 3. Outboard of these thin regions 21, the outer ends 5a,5b of the plates 8 are fixed rigidly to the side bars 19. This can be achieved by means of screws passing through the plates 8 and side bars 19. Metal plates (not shown) can be disposed above the outer ends 5a,5b of the plates 8 if desired, in order to strengthen the connection with the frame.

The arrangement is such that, with the folding action of the seat frame, that is, by bringing the left and right-hand sides 19a,19b of the seat frame towards each other, the seat 1 will also fold (see Fig.5a). As it does, it forms an inverted V-shape and narrows the angle subtended between the hinged arrays of plates 8.

The disposition of the hinge arrangements defining the hinge axis 3 and the thickness of the plates 8 are such that, when the plates are in their fully unfolded state, the end faces 23 of opposing hinged plates 8 are in mutual abutment such that the plates will not subtend an opening angle greater than 18O. Thus, the plates 8 remain coplanar when the seat is occupied, although they may be arranged to "tent" slightly (i.e. < 1800) when the seat is vacant. The surface, however, never dips below the horizontal.

Protrusions 18 extend perpendicularly from the lower surfaces of the plates 8 adjacent their outer ends but inboard of the flexible narrowed portions 21. Opposing pairs of protrusions 18a,18b on either side of the hinge axis 3 abut each other when the plates are in their fully folded position (see Fig.3).

A back portion 25 of the wheelchair, of similar construction to the abovedescribed seat 1, may also be provided if desired. In most cases, this will be unnecessary as the major part of the user's weight is taken by the seat itself.

Thus, by providing a firm level seat as a base it is possible in many cases to improve sitting balance, make sitting more comfortable, reduce the risk of some permanent deformities and assist in transfers of users. The conventional canvas seat of the wheelchair can be replaced with a free-folding, self-supporting solid seat of the present invention. The plastic construction of the seat using plastics materials should provide a seat for the life of the wheelchair.

The design provides a solid seat base for a cushion or other comfort, whilst allowing the seat to fold in line with the normal folding action of the wheelchair. The seat is detachable if required, and easily cleaned and disinfected.

Nearly all wheelchairs in the U.K. and abroad are of a basic standard size and specification, and the seat can be manufactured to fit nearly all existing wheelchairs and new wheelchairs without modification to the wheelchair. The seat can be designed to be fitted directly in place of the existing canvas type.

This design significantly improves the quality of sitting posture for wheelchair users by reducing the factors associated with hammocking and previous poor design.

Claims

1. A solid level seat which is foldable on a collapsible seat frame, comprising two arrays of substantially rigid plates which are adjacently connected along a hinged folding axis adapted to permit the seat to be folded in one direction to a collapsed state and to be unfolded in the opposite direction to form a horizontal seating surface.

2. A foldable seat comprising two hinged plates which are coupled together on a hinge axis, the plates being pivotable about the hinge axis between two extreme positions, in a first, folded one of which the plates lie substantially upright and the hinge axis lies above the normal seat level, and in a second of which the two hinged plates are both horizontal, the disposition of the hinge axis relative to the plates and the dimensions of the plates being such that the plates can not subtend between them an opening angle which is greater than 1809, whereby the plane of the seat is prevented from dipping below the horizontal.

3. A foldable seat as claimed in claim 2, wherein the plates are foldable by means of hinge fittings which are integral with the plates, each hinge fitting being interengageable with that of another plate.

4. A foldable seat as claimed in claim 3, wherein each plate carries a plurality of said hinge fittings along one side edge of that plate, each hinge fitting containing a respective through-bore, and wherein a rod extends through the through-bores of all of the hinge fittings to define said hinge axis, the through-bores of the hinge fittings of both plates being disposed in a plane parallel to but laterally spaced from the plane of that plate and substantially in the plane of said one side edge of that plate, whereby in the second, unfolded position of the seat, said side edge of one plate abuts said one side edge of the other plate in mutual parallel engagement.

5. A foldable seat as claimed in claim 2 or 3, wherein the plates have upper and lower surfaces, with the upper surface forming the seating, the lowr surface being provided with ribbed protrusions which are disposed along axes parallel to that of the hinge axis.

6. A foldable seat as claimed in claim 5, wherein further rods are threaded through said protrustions on the lower surfaces of the plates, for connecting the plates together, where necessary.

7. A foldable seat as claimed in any of claims 1 to 6, wherein the seat includes means for attachment to a seat frame.

8. A foldable seat as claimed in claim 6, wherein the outer edges of the plates are connected to the seat frame via further hinges.

9. A foldable seat as claimed in claim 7, wherein said further hinges are formed integrally with the plates.

10. A foldable seat as claimed in any of claims 1 to 9, wherein a protrusion extends perpendicularly from the lower surface of each plate, near the end opposite that of the folding axis, so that in the folded position, the protrusions of opposing pairs of plates abut.

11. A foldable seat as claimed in any of claims 1 to 10, wherein a foldable back rest of similar construction to the seat, which is also attachable to the foldable seat frame, is provided in addition to the seat.

12. A foldable seat, substantially as hereinbefore described, with reference to and as illustrated in the accompanying drawings.