Wheel Chair

Abstract

 A wheelchair comprising at least two driven wheels, at least one castor, a supporting frame, a seat assembly and a back assembly, said wheelchair furthermore comprising a rotating element to prevent the wheelchair from tipping over in the direction of movement thereof during use, a special feature being the fact that the rotating element is connected to the supporting frame and can be moved to and fro between an inward position and an outward position in a direction that includes an angle of 0-30° with the direction of movement of the wheelchair.

Description

[0001] The invention relates to a wheelchair comprising at least two driven wheels, at least one castor, a supporting frame, a seat assembly, to be referred to below as "seat", and a back assembly, to be referred to below as "back", said wheelchair furthermore comprising a rotating element to prevent the wheelchair from tipping over in the direction of movement thereof during use. The invention further relates to a method for manufacturing the wheelchair.

[0002] A wheelchair described in US patent No. 4,500,102 (Haury et al) functions as follows. When the wheelchair tends to tip over, for example as a result of a large force being exerted thereon in a direction opposed to the direction of movement, the rotating element engages the ground, thus inhibiting the chair from tipping forward. Said rotating element is embodied as an elongated roller mounted for rotation about a horizontal axis or as an elongated sleeve of tough polymeric material.

[0003] The object of the invention is to provide a wheelchair which offers a user optimum protection against tipping over and which at the same time makes it possible to ride comfortably over an uneven surface.

[0004] It is noted that the invention can provide protection against tipping over in the direction of movement of the wheel chair, i.e. both forward and backward. In order not to make the text unnecessarily complicated, only tipping over in forward direction will be discussed hereinafter; this must not be construed as being limitative, however.

[0005] In order to accomplish the above object, a wheelchair of the kind referred to in the introduction is according to the invention characterized in that the rotating element is connected to the supporting frame and can be moved to and fro between an inward position and an outward position in a direction that includes an angle of 0-30° with the direction of movement of the wheelchair. This achieves that the forwardly extending rotating element will move inward upon encountering unevennesses on a supporting surface, for example when the present wheelchair bumps against an elevation such as a kerbstone, so that the wheelchair can continue on its way at least substantially without any jolts. When the present wheelchair rides off the kerb in such a case, the rotating element will be in the outward position and thus prevent the wheelchair from tipping forward. The aforesaid angular range has been selected such that on the one hand the rotating element will move inward as a result of encountering a barrier in the direction of movement, whilst on the other hand said rotating element will be locked in the outward position when the wheelchair is in danger of tipping forward. Extensive experiments have shown in this connection that an angular range of 0-20°, in particular 0-10°, relative to the direction of moment of the wheelchair is preferred with a view to utilising the "self-braking effect" yet to be described hereinafter. The invention employs a purely mechanical anti-tipping system, therefore, without motors and/or sensors being used.

[0006] In the case of rear-wheel driven wheel chairs, the rotating element is usually mounted on the rear side of the wheelchair, whilst it is usually mounted on the front side of the wheelchair in the case of front-wheel driven wheel chairs. In either case, however, the purpose of the rotating element is to increase the distance between the centre of gravity of the whole and the contact area of the wheels with the ground as soon as there is a danger of the wheelchair tipping over. Said danger is imminent, for example, in the case of brusque acceleration or deceleration, or - as already said before - when moving up/down slopes.

[0007] In one preferred embodiment of a wheelchair according to the invention, the rotating element automatically returns from the inward position to the outward position. The wheelchair is thus automatically protected against tipping in forward direction whatever the circumstances. In particular, the rotating element automatically returns to the outward position under the influence of spring force.

[0008] In a further preferred embodiment of a wheelchair according to the invention, the rotating element is connected to the supporting frame by means of at least one telescopic arm. Preferably, the rotating element comprises at least two wheels, each wheel being connected to the supporting frame by means of a telescopic arm.

[0009] The operation of said rotating element is in particular based on the following. As soon as a force (load) is exerted at least substantially in the direction of the central axis of the telescopic arm(s), for example when the present wheelchair bumps into a threshold (kerbstone), the rotating element with its telescopic arm will move so far inwards that the front wheels of the wheelchair come into contact with the threshold and can subsequently ride up said threshold without any effort. In the case of the wheelchair tipping forward, however, the force (load) is exerted in a direction at least substantially perpendicular to the central axis of the telescopic arm, so that the latter cannot move inward, thus preventing the wheelchair from tipping in forward direction. In other words, as soon as a force (load) is exerted in a direction sufficiently deviating from the aforesaid central axis, a "self-braking effect" occurs.

[0010] In another preferred embodiment of a wheelchair according to the invention, the telescopic arms are each provided near one end with a wheel carrier having a U-shaped longitudinal section, with a pin extending between the legs of the U-shape, on which pin a respective wheel is mounted in bearings. In this way an optimum mounting of the wheels is ensured, which prevents sudden locking of the wheels upon engaging a supporting surface. This danger of locking is much greater with the poorly journalled roller of the wheelchair as known from the aforesaid US patent.

[0011] The invention also relates to a method for manufacturing a wheelchair according to the invention, wherein the wheelchair is fitted with at least two driven wheels and at least one castor, a supporting frame, a seat and a back, and wherein said wheelchair is furthermore fitted with a rotating element to prevent the wheelchair from tipping over during use, characterized in that the rotating element is connected to the supporting frame in such a manner that the rotating element can be moved to and fro between an inward position and an outward position in a direction that includes an angle of 0-30° with the direction of movement of the wheelchair.

[0012] The invention will now be explained in more detail with reference to figures illustrated in a drawing of a preferred variant of the invention, in which:

• Fig. 1 is a schematic side elevation of an electric front-wheel driven wheelchair according to the invention;
• Figs. 2 and 3 are schematic side elevations of the wheelchair of Fig. 1, in which the rotating element, being embodied as two wheels, is in an inward position as a result of the wheelchair having bumped into a kerbstone; and
• Fig. 4 is a schematic, perspective view of the rotating element of Figs. 2 and 3.

[0013] Fig. 1 shows a wheelchair 1 according to the invention, comprising two electrically driven front wheels 2, which are interconnected by means of a rigid front axle, two small or rear wheels 3, a supporting frame 4, as well as a seat assembly 5 and a back assembly 6. In order not to make the figure unnecessarily complicated, the two assemblies are shown without a seat cushion and a back cushion, respectively, for the sake of simplicity. Furthermore, a leg support may be provided, to the bottom side of which a footrest is mounted (not shown). The leg support may be fixed to the supporting frame 4 by means of a rod.

[0014] As Figs. 1 and 4 show, two brackets 7 of U-shaped cross-section are mounted to the supporting frame 4, to each of which brackets 7A telescopic arm 8 is welded. Each telescopic arm 8 is provided near its end with a wheel support 9 having a U-shaped longitudinal section, whilst a pin 11 is mounted between the legs of the U-shape, on which a wheel 12 is mounted in bearings. The telescopic arms 8 can moved to and fro between an inward position and an outward position in a direction that includes an angle of approximately 7° with the direction of movement of the wheelchair 1.

[0015] Fig. 2 shows in detail how the telescopic arms 8 with the wheels 12 are pushed to their inward position by a barrier present in the direction of movement of the wheelchair, for example when the wheelchair 1 bumps into a kerbstone 13. The wheels 12 are pushed rearwards by the kerbstone 13 until the front wheels 2 of the wheelchair 1 touch the kerbstone and the wheelchair can easily ride up the kerbstone 13 without any further impediment (Fig. 3). After the wheelchair 1 has ridden up the pavement and the telescopic arms 8 with the wheels 12 no longer experience any counterpressure from the kerbstone 13, therefore, the arms are released again, in the sense that they automatically return from the inward position to their starting position (i.e. the outward position).

[0016] Fig. 1 relates to a situation in which the wheelchair 1 is in danger of tipping forward as a result of sudden braking. The wheels 12 come into contract with the ground so as to prevent the wheelchair 1 from tipping forward. As already said before, the telescopic arms 8 with the wheels 12 are locked in the outward position, since the aforesaid angle of inclination of approximately 7° ensures that the force being exerted in the longitudinal direction of the telescopic arms 8 is too small to cause said arms to telescope.

[0017] From the above it will be apparent that the anti-tipping system according to the invention "stands by at all times", in the sense that the outward position of the rotating element is the starting position thereof.

[0018] It is noted that the invention is not limited to the preferred variant as described herein, but that it also extends to other embodiments that fall within the scope of the appended claims. Thus it will be understood by those skilled in the art that the telescopic arms 8 with the wheels 12 may be exchanged for a roller which can be moved to and fro, whether or not by means of telescopic arms.

Claims

1. A wheelchair comprising at least two driven wheels, at least one castor, a supporting frame, a seat assembly and a back assembly, said wheelchair furthermore comprising a rotating element to prevent the wheelchair from tipping over in the direction of movement thereof during use, characterized in that the rotating element is connected to the supporting frame and can be moved to and fro between an inward position and an outward position in a direction that includes an angle of 0-30° with the direction of movement of the wheelchair.

2. A wheelchair according to claim 1, wherein the rotating element can be moved to and fro between an inward position and an outward position in a direction that includes an angle of 0-10° with the direction of movement of the wheelchair.

3. A wheelchair according to claim 1 or 2, wherein the rotating element automatically returns from the inward position to the outward position.

4. A wheelchair according to claim 2, wherein the rotating element automatically returns to the outward position under the influence of spring force.

5. A wheelchair according to any one of the preceding claims 1 - 4, wherein the rotating element is connected to the supporting frame by means of at least one telescopic arm.

6. A wheelchair according to claim 5, wherein the rotating element comprises at least two wheels, each wheel being connected to the supporting frame by means of a telescopic arm.

7. A wheelchair according to claim 6, wherein the telescopic arms are each provided near one end with a wheel carrier having a U-shaped longitudinal section, with a pin extending between the legs of the U-shape, on which pin a respective wheel is mounted in bearings.

8. A method for manufacturing a wheelchair according to any one of the preceding claims 1 - 7, wherein the wheelchair is fitted with at least two driven wheels and at least one castor, a supporting frame, a seat and a back, and wherein said wheelchair is furthermore fitted with a rotating element to prevent the wheelchair from tipping over during use, characterized in that the rotating element is connected to the supporting frame in such a manner that the rotating element can be moved to and fro between an inward position and an outward position in a direction that includes an angle of 0-30° with the direction of movement of the wheelchair.

Drawing