WO2001008624A1

WO2001008624A1 - A vehicle

Info

Publication number: WO2001008624A1
Application number: PCT/GB2000/002921
Authority: WO
Inventors: Clifford Alan Thurston; Craig Leo Camidge
Original assignee: Clifford Alan Thurston; Craig Leo Camidge
Priority date: 1999-07-30
Filing date: 2000-07-28
Publication date: 2001-02-08
Also published as: GB2358160A; GB9917925D0; AU6174300A; GB0110276D0

Abstract

A vehicle comprises a framework (3) for carrying a load and a tracked unit (7) connected to the framework (3) for engaging steps to allow the vehicle to climb and descend the steps, the tracked unit (7) comprising a continuous flexible belt (11) that runs over a pair of pulleys (13, 15) so as to engage the nose of a step and be deflected and tensioned by said load. One of the pulleys (15) is moveable relative to the framework (3) and the other pulley (13) so as to change the attitude of the belt (11) as it moves over the nose of the step. A lower one of the two pulleys (13) serves as a rear wheel of the vehicle so that it engages the tread of a step and presents the inclined belt (11) to the nose of the step. Both pulleys (13, 15) are mounted on an arrangement of swing links (17, 25) connected to the framework (3). The upper (15) of the two pulleys moves on an arcuate path whilst the lower pulley is constrained to move to a lesser extent. One pulley (15) is connected to the end of one link (17) and the other pulley (13) connected to an intermediate link (21) connected between the two swing links (17, 25). A wheelchair comprises two tracked units mounted one on each side and connected by a cross-axle.

Description

A VEHICLE

Technical Field

This invention relates to a vehicle for carrying a load, such as a wheelchair.

A common problem with wheelchairs is the difficulty in climbing and descending stairs safely, especially when the occupant may be a heavy adult. This can be a particular problem with chairs used by emergency services to carry patients to and from an ambulance vehicle when the route may unavoidably include steps or stairs. The invention aims to provide an improved wheelchair which reduces these difficulties.

Disclosure of the Invention

A vehicle according to the invention comprises a framework for carrying a load and a tracked unit connected to the framework for engaging steps to allow the vehicle to climb and descend stairs, the tracked unit comprising a continuous flexible belt that runs over a pair of pulleys so as to engage the nose of a step and be deflected and tensioned by said load. Preferably, at least one of the pulleys is moveable relative to the framework and the other pulley so as to change the attitude of the belt as it moves over the nose of the step.

Preferably, a lower one of the two pulleys serves as a rear wheel of the vehicle so that it engages the tread of a step and presents the inclined track to the nose of the step. The load is then transferred to the belt as the lower wheel is lifted off the ground by a person pulling the vehicle up the step, and the load then serves to tension the belt to match the applied load and causes the attitude of the belt to change as it moves over the nose of the step so that the framework follows a gentle undulating path as it ascends the steps. The vehicle therefore remains balanced relative to the load as it ascends the steps, and the load is transported more safely. The action of the tracked unit is similar when operating in reverse to descend steps.

Preferably, both pulleys are mounted on an arrangement of pivoted links connected to the framework. The upper of the two pulleys is allowed to move on an arcuate path whilst the lower pulley is constrained to move to a lesser extent. The relative movements of the two pulleys is preferably controlled by a pair of swing links with one pulley connected to the end of one and the other pulley connected to an intermediate link connected between the two swing links.

Preferably, a wheelchair according to the invention consists of two tracked units mounted one on each side of the chair, with the two upper pulleys connected by a cross axle.

Description of the Drawings

The invention will now be described by way of example with reference to the accompanying drawings.

Figure 1 is a side elevation of an ambulance chair;

Figure 2 is an enlargement of the lower portion of Figure 1;

Figure 3 shows the track portion of the ambulance chair of Figure 1 in engagement with the nose of a step;

Figure 4 shows the track portion of the ambulance chair of Figure 1 in engagement with the tread of a step; and

Figures 5 shows the track portion of the ambulance chair of Figure 1 as it begins to descent over the nose of a step.

Embodiment of the Invention

As shown in Figure 1, the ambulance chair 1 comprises a frame 3 for supporting a load, such as an injured person, on the chair. Typically, a fabric web (not shown) is attached to the frame 3 for this purpose. The frame 3 is provided with two wheels 5 at the front of the chair, one on each side of the frame 3, and two track units 7, one on each side of the frame 3 and to the rear of the wheels 5. Each track unit 7 comprises an endless belt 11 extending around and between its front wheel 13 and its rear wheel 15. The track units 7 are connected to the frame 3 such that they can pivot relative thereto. The track units 7 are linked and share the same pivotal motion by virtue of an axle 30 extending laterally between the front wheels 13 of the track units 7 and an axle 31 extending laterally between the rear wheels 15 of the track units 7. When the chair 1 is being moved along level ground, it moves o the front wheels 13 of the track units 7 and the wheels 5 provided at the front of the frame 3. When the chair 1 is being raised or lowered on stairs, it moves on the track units 7. Since the track units 7 are pivotally mounted on the frame 3, the chair 1 can be manoeuvred over a flight of stairs along a sinuous path. This provides a smooth and comfortable ride for the occupant of the chair, in contrast to a traditional chair which would negotiate the stairs in a discontinuous and jarring manner.

Figure 2 illustrates the arrangement permitting the pivotal motion of the near side track unit. It will be appreciated that a corresponding arrangement is provided for the track unit 7 on the far side of the chair. The rear wheel 15 of the track unit 7 is attached to the frame 3 by link 17 which can rotate about pin 19. Link 17 pivots on the axle 31. Link 21 extends from the front wheel 13 of the track unit 7 to the link 17 and is pivotally connected to the axle 30 at one end and to the link 17 by a pin 23 at the other end. Link 21 is also connected directly to the frame 3 by means of link 25, which is pivotally attached to frame 3 by pin 27 at one end, and is pivotally attached to link 21 by pin 29 at its other end. Link 17 is longer than link 25.

The geometry of the pivotal links 17,21 and 25 provides the wheels 13 and 15 of the track unit 7 with a variable separation. When the chair 1 is on level ground, its load is borne by wheels 13 and 5. Part of the load is transmitted through the frame 3 directly to the axle 32 of wheel 5. Another portion of the load is transferred to wheel 13 through the arrangement of links 17,21 and 25. Since pivot pins 19 and 29 are located behind the axle 30 of wheel 13, the frame 3 tries to move downwardly in a direction which reduces the acute angle shown between link 25 and link 21 and also the acute angle shown between link 17 and link 21. In this condition, wheel 13 tends to move rearward, increasing the horizontal separation between its axle 30 and pin 27. In other words, the axle 30 of wheel 13 tends to move in an anticlockwise path relative to pin 27. Due to the load being transmitted through the links 17,21 and 25, the axle 31 of wheel 15 tends to move in a path clockwise relative to pin 19. Thus, it will be appreciated that the axles 30,31 of wheels 13 and 15 move such that their separation is increased. However, the wheels 13 and 15 are constrained by endless belt 11. The track unit 7 therefore reaches equilibrium when the tension in the endless belt 11 balances the forces which are attempting to increase the separation of the axles of wheels 13 and 15.

Figure 3 illustrates the disposition of a track unit 7 when the chair is being transferred over the nose of a step. In this condition, it is the track units 7 on the side of the frame 3 which bear the load of the chair 1. As described with reference to Figure 2, the load is transferred through the links 17,21 and 25 in a manner which tends to increase the separation of the axles 30,31 of wheels 13 and 15. As the chair negotiates the nose of a step, the endless belt 11 is deformed inwardly, increasing the tension therein. This causes the links 17, 21 and 25 to move the wheels 13 and 15 such that the separation of their axles is reduced, thereby reducing the length of, and tension in, the belt 11 until equilibrium is restored.

Figure 4 illustrates the disposition of a track unit 7 when wheel 13 is in contact with the ground. This position would be assumed, if, for example, the chair was being lowered from the position shown in Figure 3.

Figure 5 illustrates the disposition of the track unit 7 as it starts to descend over the nose of a step. The sinuous, smooth motion of the chair provided by the track units 7 and the links 17,21 and 25 is apparent from these figures 3 to 5. The regulation of the tension in the endless belt 11 by the links 17,21 and 25 during the various stages of deformation of the belt 11 will also be appreciated.

Claims

1. A vehicle comprising a framework (3) for carrying a load and a tracked unit (7) connected to the framework for engaging steps to allow the vehicle to climb and descend steps, the tracked unit (7) comprising a continuous flexible belt (11) that runs over a pair of pulleys (13,15) so as to engage the nose of a step and be deflected and tensioned by said load.

2. A vehicle as claimed in claim 1 in which at least one of the pulleys (15) is moveable relative to the framework (3) and the other pulley (13) so as to change the attitude of the belt as it moves over the nose of the step.

3. A vehicle as claimed in claim 1 or 2 in which a lower one (13) of the two pulleys serves as a rear wheel of the vehicle so that it engages the tread of a step and presents the inclined belt (11) to the nose of the step.

4. A vehicle as claim in any one of claims 1 to 3 in which both pulleys (13,15) are mounted on an arrangement of pivoted links (17,21,25) connected to the framework (3).

5. A vehicle as claimed in any one of claims 1 to 4 in which the upper (15) of the two pulleys is allowed to move on an arcuate path whilst the lower pulley (13) is constrained to move to a lesser extent.

6. A vehicle as claimed in any one of the preceding claims 1 to 5 in which the relative movements of the two pulleys (13,15) are preferably controlled by a pair of swing links (17,25) with one pulley (15) connected to the end of one (17) and the other pulley (13) connected to an intermediate link (21) connected between the two swing links (17,25).

7. A vehicle as claimed in any one of the preceding claims in which a front wheel (5) is provided in front of the tracked unit (7).

8. A wheelchair comprising two tracked units (7) mounted one on each side of a chair, each tracked unit (7) being as claimed in any one of claims 1 to 6 with a cross-axle (30,31) connecting an upper one of the two pulleys of each tracked unit.

9. A vehicle substantially as herein described with reference to the accompanying drawings.