WO1994007452A1

WO1994007452A1 - Stair transcending conveyance

Info

Publication number: WO1994007452A1
Application number: PCT/AU1993/000512
Authority: WO
Inventors: Frederick Harry Davis; Warren James Hancock
Original assignee: Australian Transcenders International Limited
Priority date: 1992-10-07
Filing date: 1993-10-01
Publication date: 1994-04-14
Also published as: AU5144793A; AU702926B2

Abstract

The invention provides a conveyance that is particularly suited for traversing support surfaces such as steps and stairs. The conveyance includes a chassis (2), a load carried mounted (3) with the chassis (2) and at least one front wheel (6) and at least one rear wheel (4) also mounted with the chassis (2). A selectively operable drive track (10) is also provided that is again connected with the chassis (2), the drive track defining a surface engageable drive portion (12). Each of the front and rear wheels (6 and 4) are independently and selectively moveable toward a retracted position in which the drive portion engages the surface and a second position in which the wheels extend to displace the drive portion (12) from the surface. The conveyance also includes means to selectively drive at least one of the wheels and/or the drive track (10).

Description

Title: "STAIR TRANSCENDING CONVEYANCE"

FIELD OF THE INVENTION

The present invention relates to conveyances, and in particular to conveyances adapted to negotiate steps and stairs.

BACKGROUND OF THE INVENTION

The invention has been developed primarily as a wheelchair conveyance for disabled persons and will be described hereinafter with reference to this application. However, it will be appreciated that the invention is not limited to this particular field of us and may be employed, for example, as a trolley base for robot devices and the like or as a simple general transport device.

In the field of wheelchair design, there have been a great many proposed solutions to the problem of negotiating stairs. However, most of these systems have been relatively complicated and correspondingly expensive. Furthermore, they are generally slow and difficult to operate, particularly when descending a flight of stairs.

It is an object of the present invention to provide a conveyance that overcomes or at least ameliorates one or more of the above discussed disadvantages of the prior art.

DISCLOSURE OF THE INVENTION

According to the invention there is provided a conveyance adapted to traverse a support surface, said conveyance comprising: a chassis; a load carrier mounted with said chassis; at least one front wheel and at least one rear wheel each mounted with said chassis; a selectively operable drive track connected with said chassis and defining a drive portion; each of said front and rear wheels being independently and selectively movable between a retracted position in which said drive portion engages said surface and a second position in which said wheels extend to displace said drive portion from said surface; and means to selectively drive at least one of said wheels and/or said drive track. Preferably, each of the wheels can be positioned at locations intermediate the retracted and extended positions.

In a preferred form the front and rear wheels are respectively mounted on front and rear swing arm assemblies for rotation between the retracted and extended positions.

Desirably, the swing arms are each mounted for rotation about substantially horizontal axes that extend substantially transverse to the longitudinal extent of the drive portion.

It is further preferred that the front and rear swing arm assemblies each rotate in substantially opposing directions whereby height adjustment of the conveyance is effected.

Desirably, two rear driven wheels are provided together with one or two front wheels, the front swing arms preferably being additionally mounted for rotation about a substantially vertical axis. In the preferred form the combined horizontal and vertical rotation is achieved by the use of castors.

Preferably, the load carrier is mounted for selective fore and aft movement relative to the chassis for maintaining the centre of gravity of the conveyance in a stable location during tilting of the chassis.

Desirably, the load carrier is pivotably mounted with the chassis to maintain the carrier in a substantially horizontal orientation during inclination of the chassis.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:

Figure 1 is a schematic side view of a conveyance in the form of a wheelchair according to the invention, illustrated in the approach position for ascending a flight of stairs.

Figure 2 is a schematic side view of the wheelchair shown in Figure 1 engaging the stairs.

Figure 3 is a schematic side view of the wheelchair shown in the previous Figures ascending a flight of stairs.

Figure 4 is a schematic side view of the wheelchair at the top of a flight of stairs.

Figure 5 is a schematic side view of the wheelchair illustrated in the fully raised position.

PREFERRED EMBODIMENT OF THE INVENTION

Referring to the drawings, the conveyance in the form of a wheelchair 1, includes a chassis indicated generally at 2 to which is mounted a load carrier in the form of a chair 3.

Also mounted with the chassis are two driven rear wheels 4 connected via rear swing arms 5 and two front castors or wheels 6 connected on front swing arms 8. Actuators (not shown) are attached to each of the swing arms to effect selective positioning of each wheel or pairs of wheels.

Two fixed drive tracks 10 having toothed projections 11 are mounted on either side of the chassi 2, each track defining a drive portion 12, a front nose portion 13 and rear climbing portion 14.

A motor/gearbox/clutch and brake assembly shown generally at 15 is mounted to the chassis and connects via a first toothed belt drive 16 to at least one of th rear wheels 4 and a second chain drive 17 to at least one of the tracks 10.

Connected intermediate the chair 3 and chassis 2 i a chair tilt mechanism including a support post 18 pivotably mounted to the chassis at one end and rigidly connected to the base of the chair 3 at the other end. A telescopically operable strut 19 is also provided which is pivotably mounted at one end with the chassis at a location spaced from the mounting point of post 18, the other end being pivotably connected with the post a a location intermediate the post ends.

In use, the mode of operation is extremely simple. The swing arm actuators (not shown) and strut 19 can comprise any suitable drive means such as, for example hydraulic rams, each of the drive means preferably bein operable via controls mounted on the chair arm as shown. In general terms the tracks are fixed to the exterior of the chassis, drive being transferred between the wheels and the tracks by selectively retracting the front and rear wheels 6 and 4 on the respective swing arm assemblies 8 and 5.

More specifically, stair climbing, for example, is achieved as follows.

First the wheelchair 1 is reversed towards the stairs with the rear climbing portion 14 of the tracks 10 being raised above the first step height (as shown in Figure 1) . The tracks 10 are raised in this manner by simply rotating the rear swing arm 5 towards the front wheels 6 which shortens the wheel base, simultaneously raising up the rear of the chassis and tracks.

The rear wheels 4 are then slowly retracted by pivoting the rear swing arms 5 until the rear end of the tracks 10 come into contact with the first stair nose 20 as shown in the drawings. The rear wheels are then rapidly retracted to a position between the tracks 10 as shown in Figure 2.

The front castors 7 are then retracted on front swing arms 8 by rotation toward the front of the conveyance, bringing the front nose portion 13 of the tracks 10 into contact with the ground 21.

The second stair step 22 is climbed by the projections 11 on the rear climbing portion 14 of the tracks 10 engaging on the second stair nose 23. When climbing steps which have deep treads, the rear wheels 4 may be lowered in preferred embodiments in a controlled jacking motion to smooth the climbing operation.

During all motions, the chair 3 is tilted by action of the telescopic strut 19 on the pivotable seat post 18 to maintain the operator in a vertical seated attitude. This operator attitude remains constant during climbing as shown in Figure 3.

When almost at the top of the flight of stairs and the track rear overhangs the top landing 24, the rear wheels 4 are swung down on rear swing arms 5 into contact with the landing. The wheels are de-clutched to allow them to roll freely and the tracks continue to drive the wheelchair upwards as shown in Figure 4.

As the wheelbase between the rear wheels 4 and the point of contact between the tracks and the top stair nose lengthens, the wheelchair chassis angle gradually swings towards the horizontal (see Figure 4) .

Once the tracks are clear of the top stair nose 25 the front castors 6 are swung down on swing arms 8 lifting the tracks clear of the floor. The wheelchair 1 is now ready for wheel driven rolling motion as shown in Figures 1 and 5.

A considerable advantage of the present invention is the operator assurance that comes from the progressive lowering operation when descending a flight of stairs. In many prior art systems it was necessary for the operator to approach the top of the stairs, tilt back the chair to rearwardly displace the centre of gravity and then edge forward over the top of the stairs in a cantilevered fashion.

The chair would then stop in this precarious position and an "easy down" cushioning device would be extended downwards to engage the stairs. The whole chair would then tilt until the tracks or other stair engaging drive means aligns with the trajectory of the stairs. The rearward inclination of the operator combined with the cantilevered positioning would make this a very disconcerting manoeuvre for the operator.

In the present invention however, when descending a flight of stairs, the front wheel is retracted before the top of the stairs as shown in Figure 4. As the nose of the track passes over the top stair nose 25 and the rear wheels 4 approach the stairs, the chassis and track are gradually inclined to the trajectory of the stairs, the chair inclination being adjusted to maintain the operator in a substantially vertical attitude throughout the exercise. This is clearly faster and less precarious than the prior art solutions.

From the description of operation above, it can be seen that the design and mode of use of the conveyance are very simple. Furthermore, the use of a fixed track makes the design less expensive and lighter than prior art solutions incorporating movable, flexible or multi-segment tracks.

Another advantage of the invention is that the same mechanism used to engage and displace the tracks, provides a powered height adjustment facility.

Adjustment of the operators height, in the preferred embodiment, is achieved by a combination of two mechanisms as will be discussed with reference to Figure 5.

The main contribution to height variation comes, as discussed above, from varying the amount of rear to front wheel extension, achieved by adjusting the angle of the rear wheel swing arms 5 (compare with Figure 1) .

A secondary contribution to height adjustment is achieved by using the seat tilt mechanism comprising the strut 19 that acts on the seat post 18 to simultaneously adjust the chair fore to aft position and raise the chair relative to the chassis. Accordingly, a separate actuator for height adjustment is not reguired, again saving cost and weight over the prior art options.

A further advantage of this design is that the shortened wheelbase corresponding to a fully raised seat reduces the wheelchair turning circle thereby increasing manoeuvrability.

Whilst the invention has been described with reference to specific examples, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms.

Claims

1. A conveyance adapted to traverse a support surface, said conveyance comprising: a chassis; a load carrier mounted with said chassis; at least one front wheel and at least one rear wheel each mounted with said chassis; a selectively operable drive track connected with said chassis and defining a drive portion; each of said front and rear wheels being independently and selectively movable between a retracted position in which said drive portion engages said surface and a second position in which said wheels extend to displace said drive portion from said surface; and means to selectively drive at least one of said wheels and/or said drive track.

2. A conveyance according to claim 1 wherein the wheels can be positioned at locations intermediate the retracted and extended position.

3. A conveyance according to claim 1 or claim 2 wherein the load carrier is mounted for selective fore and aft movement relative to the chassis for maintaining the centre of gravity of the conveyance in a stable location during tilting of the chassis.

4. A conveyance according to any one of the preceding claims wherein the load carrier is pivotably mounted with the chassis to maintain the carrier in a substantially horizontal orientation during inclination of the chassis.

5. A conveyance according to claim 3 or claim 4 wherein the inclination of the load carrier relative to the chassis is achieved by linearly acting drive means disposed to position a load support post pivotably mounted with the chassis.

6. A conveyance according to any one of the preceding claims wherein the front and/or rear wheels are respectively mounted on front and rear swing arm assemblies for rotation between the retracted and extending positions.

7. A conveyance according to claim 6 wherein the swing arms are each mounted for rotation about substantially horizontal axes that extend substantially transverse to the longitudinal extent of the drive portion.

8. A conveyance according to claim 6 or claim 7 wherein the front and rear swing arm assemblies each rotate in substantially opposing directions whereby height adjustment of the conveyance is effected.

9. A conveyance according to any one of claims 6 to 8 wherein the positioning of the swing arms is effected by means of actuators connected with each swing arm or pairs of swing arm assemblies.

10. A conveyance according to any one of claims 6 to 9 wherein the front swing arm is additionally mounted for rotation about a substantially vertical axis.

11. A conveyance according to claim 10 wherein the combined horizontal and vertical rotation of the front swings arms is achieved by the use of castors.

12. A conveyance according to any one of the preceding claims wherein the rear wheel or wheels may be lowered in a controlled jacking motion to smooth the stair climbing operation.

13. A conveyance according to any one of the preceding claims wherein two rear driven wheels are provided together with one or two front wheels.

14. A conveyance according to any one of the preceding claims wherein the drive track comprises a toothed drive belt.

15. A conveyance according to any one of the preceding claims wherein the drive track includes a rear stepped surface engaging climbing portion that extends in a direction generally away from the drive portion.

16. A conveyance according to claim 14 wherein the climbing portion is adapted to engage and climb a stepped surface until the drive portion is in engagement therewith.

17. A conveyance according to any one of the preceding claims including suitable motor, gearbox, clutch and brake assemblies.