GB2191454A

GB2191454A - Wheelchair

Info

Publication number: GB2191454A
Application number: GB08613929A
Authority: GB
Inventors: Kari Helin
Original assignee: TUNTURIPYOERAE Oy; TUNTURIPYORA Oy
Current assignee: TUNTURIPYOERAE Oy; TUNTURIPYORA Oy
Priority date: 1986-06-09
Filing date: 1986-06-09
Publication date: 1987-12-16
Also published as: GB8613929D0; DE3617518A1

Abstract

A wheelchair capable of moving on uneven ground and up and down flights of steps comprises, in addition to conventional driving wheels, crawler belts 2 which are positioned under the seat of the chair at an angle of thirty to forty degrees to the driving surface. Another pair of shorter crawler belts 6 extend from the crawler belts 2 at a wide angle, with their rear ends in a higher position than the forward ends. The drive is transferred from the wheels to the crawler belts by a forward and upward displacement of the wheels 1 by means of a shift device 3, in the form of a screw provided under the seat. This brings a toothed wheel 4 on the axle of each wheel into engagement with a second toothed wheel 5 which drives a respective crawler belt 2 through a chain drive 7. Each wheel 1 thus drives its corresponding crawler belt 2, leading to considerable manoeuvrability, allowing the user to ascend and descend steps without difficulty. <IMAGE>

Description

SPECIFICATION Wheelchair This invention relates to wheelchairs and particularly to wheelchairs which are suitable for driving both on even surfaces and on uneven ground and up and down flights of steps. A disadvantage of conventional wheelchairs is that they are not suited for use on steps and other uneven surfaces.

Attempts have been made to overcome this disadvantage in various ways by replacing conventional wheels by wheel assemblies of three to four wheels which are more suitable for usa on steps; by using crawler type mechanisms together with or in place of conventional wheels; by hydraulic auxiliary feet and so forth. Another group of mechanisms includes different kinds of auxiliary devices provided separately for the steps in question, transporting devices, lifts, mechanisms supported on the rails and so forth.

Several relatively reliable mechanisms have, in fact, been provided for driving up and down a flight of steps; these mechanisms, however, have essentially impaired the usability of the wheelchairs on even surfaces or in normal use. It has been characteristic of almost all these mechanisms that they require another person to help the user of the wheelchair on steps.

According to the present invention a wheelchair intended for driving on uneven ground and up and down flights of steps as well as on even surfaces, comprises, in addition to pairs of large and small wheels, inclined crawler belts which are spaced from the driving surface when the chair is driven on the wheels, a power transmission mechanism for transmitting the rotary movement of the large wheels to the crawler belts and a shift device attached to the frame of the chair and connected to an axle of the driving wheels for displacing the large wheels above the crawler belts.

Such a construction tends to eliminate the above disadvantages, as will be understood from the following summary of the mode of operation.

1. The wheelchair can be driven in two different ways (a) by means of the wheels (normal drive on even surfaces); (b) by means of the crawler belts (steps and other difficult places); 2. Changing the way of driving from the wheels to the crawler belts (or vice versa) is carried out by a displacement of the large driving wheels upwards by means of the shift device, for instance a screw or a hydraulic cylinder positioned under the seat. A screw may, for instance, be attached at both ends to the frame of the chair and connected also to the axle of the driving wheels.

3. The user ascends a flight of steps by means of the wheelchair with his back towards the direction of movement and with his eyes towards the direction of a possible fall (psychological security). The steps are descended with the user facing towards the direction of movement.

4. Two crawler belts provided, and they are preferably operated independently of each other. As a result, it is also possible to turn the wheelchair by means of the crawler belts (turns on the steps).

5. The movement of the crawler belts is connected to the movement of the large driving wheels (by means of toothed wheels and chains/toothed belts). Consequently, it is also possible to drive the wheelchair by means of the large wheels on the steps.

6. As to the appearance and operational properties, the arrangement is similar to a conventional wheelchair in normal drive.

The invention will now be described in more detail, with reference to the accompanying drawings, wherein: Figure 1 shows a wheelchair in accordance with the invention in a normal driving position; Figure 2 shows the wheelchair when crawler belts are in use; and Figure 3 is a view similar to Figure 1 showing an alternative power transmission mechanism.

The wheelchair shown in the drawings includes two crawler belts 2 having a length of 60 cm to 80 cm which are fitted under the seat of the wheelchair, and are positioned at an angle of thirty to forty degrees with respect to the driving surface thereof, i.e. the plane through the driving surfaces of the wheels, (a normal angle of ascent of a flight of steps). The forward ends of the crawler belts are lower than the rear ends. The grip of the crawler belts on the steps can be improved by means of different kinds of teeth.

Large driving wheels 1 are located above the crawler belts 2 and are mounted for displacement forwardly (up to the front edge of the chair seat as seen in Figure 2) by means of a device such as a screw 3, a hydraulic cylinder, or a crank arm which is attached to the frame structure of the chair and connected to the axle of the wheels. The operation of the screw can be improved by means of a crank or an electric motor.

When the large wheels 1 are displaced forwards and upwards, the wheelchair is lowered on to the crawler belts and leans backwards (on an even surface) at an angle of thirty to forty degrees which is the angle of inclination of the crawler belts.

The large driving wheels 1 are connected to the crawler belt mechanism 2 by means of two (or three) toothed wheels 4, 5 and a chain mechanism 7 (alternatively a toothed belt or a wedged belt). One toothed wheel 4 is positioned on the axle of the large driving wheels 1 and the other toothed wheel 5 is positioned in the forward portion of the chair under the seat. When the large driving wheels have been displaced to the front position, the toothed wheels 4 and 5 are engaged with each other. There may be a single pair of toothed wheels 4, 5 but preferably there is one pair for each of the driving wheels 1, thus greatly increasing manoeuvrability.

A further toothed wheel (not seen) is mounted on the shaft of the front toothed wheel 5, by means of which a conventional chain or belt drive 7 is transmitted to the front pair of wheels 9 of the crawler belt 2.

In the mechanism illustrated, the crawler belt rotates in the opposite direction to the driving wheel. If the directions of rotation are to be the same, an intermediate idler wheel needs to be included in the drive.

Another pair bf shorter crawler belts 6 form an extension of the crawler belts 2, the crawler belts 6 forming an angle of forty to fifty degrees with the longer crawler belts 2.

By means of the crawler belts 6 it is pos sible to ascend the first steps after landings and to drive over low obstacles (e.g. street kerbs).

The shorter crawler belts 6 are driven by the movement of the longer crawler belts 2.

The belts can, of course, be part of one and the same belt, in which case an idler wheel has to be provided above the belt wheel 10.

The mechanism can also be applied to wheelchairs in which the large driving wheels are positioned in the front. In this case, however, it is necessary to provide a device or a mechanism which displaces the back wheels above the crawler belts. This displacing movement can be connected to the displacing movement of the foremost driving wheels because these movements always take place simultaneously when the wheels are replaced by the crawler belts.

Furthermore, it is desirable to provide a mechanism to prevent reverse movement and thus allow the driver to take a rest and change his grip on the large driving wheel when ascending a flight of steps. This mechanism can be a ratchet mechanism mounted on the rearmost wheel 11 of the crawler belt system or a separate brake mechanism independent of the crawler belt system.

The power transmission just described, which is based on two toothed wheels 4, 5 can be replaced by an arrangement in which the toothed belt or chain 7 is connected at its upper end directly to the axle of the large driving wheels 1 (Figure 3). A clutch mechanism 12 then has to be provided on the axle of the large driving wheels 1 so that the chain 7, which drives the crawler belts system 2, 6 can be connected and disconnected.

Claims

1. A wheelchair intended for driving on uneven ground and up and down flights of steps as well as on even surfaces, and comprising in addition to pairs of large and small wheels, inclined crawler belts which are spaced from the driving surface when the chair is driven on the wheels, a power transmission mechanism for transmitting the rotary movement of the large wheels to the crawler belts and a shift device attached to the frame of the chair and connected to an axle of the driving wheels for displacing the large wheels above the crawler belts.

2. A wheelchair according to claim 1 in which the power transmission mechanism is formed by a pair of toothed wheels which are engaged with each other when the large driving wheels have been displaced to the raised position above the crawler belts, one wheel being situated on the axle of the large wheels and the other wheel being provided with a chain or belt transmission to a wheel assembly of the crawler belts.

3. A wheelchair according to claim 1, in which the power transmission mechanism is formed by a chain or belt transmission between the large driving wheels and the crawler belts and a clutch mechanism by means of which the transmission mechanism can be connected and disconnected.

4. A wheelchair according to any one of the preceding claims in which each driving wheel has its own power transmission mechanism for the transmission of the movement of the driving wheel to a crawler belt positioned on the same side.

5. A wheelchair according to any one of the preceding claims in which the shift device obtains its driving power from an electric motor.

6. A wheelchair according to any one of the preceding claims in which another pair of shorter crawler belts form an extension of the inclined crawler belts in such a manner that they form a wide angle with the inclined crawler belts.

7. A wheelchair according to any one of the preceding claims in which the crawler belt assembly is provided with a mechanism which prevents movement of the crawler belt assembly in the reverse direction.