GB2219559A

GB2219559A - Stabilizer wheels on a three-wheeled wheelchair

Info

Publication number: GB2219559A
Application number: GB8819168A
Authority: GB
Inventors: John Franklin Morse
Original assignee: Individual
Current assignee: Individual
Priority date: 1988-06-08
Filing date: 1988-08-12
Publication date: 1989-12-13
Also published as: GB8819168D0; CA1283593C

Abstract

A stabilizer system for a three-wheel powered wheelchair having a single front steering wheel (13) mounted in the front end of the frame (11) carrying two rear wheels (12) and a seat (10) at the frame rear end, said stabilizer system comprising stabilizer idler wheels (22) mounted at the sides of the front end of the frame (11) immediately behind the steering wheel (13) and normally slightly above ground level. The tendency to overturn on cornering is thus prevented. <IMAGE>

Description

STABILIZER FOR THREE-WHEEL POWERED WHEELCHAIR TECHNICAL FIELD The invention relates generally to powered wheelchairs, and more particularly to three-wheel chairs having a single front load bearing wheel used for steering and driven by electric power.

BACKGROUND OF THE INVENTION Three-wheel powered wheelchairs have become very popular with handicapped persons because of their easy maneuverability, sharp turning radius, lightweight, small size and portability. They usually can be quickly disassembled and stored in the trunk of an automobile. Because of their small size they can be easily driven around in the house, work place or out of doors. Four-wheel powered chairs are also in use, but they are normally much larger and heavier, not as portable, have a larger turning radius, and are more expensive.

A three-wheel electric powered chair in public use in the United States is manufactured by Fortress Scientific of Hayes Road, Southall, Middlesex, England UB2 5LZ. This wheelchair has a bottom frame rollably supported by two rear wheels and a front steering wheel having one upwardly projecting steering post with steering and power controls at the top. A seat is mounted on the rear portion of the frame with batteries below the seat furnishing the electric power.

An inherent hazard of this vehicle, and all other three-wheeled vehicles of which I am aware, is that they are basically unstable if driven too fast or on irregular or sloping surfaces, tending to tip over laterally, especially when turning sharply, resulting in injury to the occupant. Thus the advantages of a sharp turning radius can become a distinct hazard.

DISCLOSURE OF THE INVENTION The present invention provides stabilizing devices for preventing tipping over of a three-wheeled wheelchair when driven at substantially top speed over irregular ground or sloping surfaces or when turning at short radii.

It is an object of the present invention to provide a novel and improved auxiliary stabilizing system for a powered three-wheel chair acting under adverse conditions to prevent the chair from tipping over laterally.

Another object is to provide idle stabilizer wheels at the sides of the front portion of a powered three-wheel chair, said wheels normally out of contact with the chair-supporting surface, but spaced only slightly thereabove so as to immediately contact said surface by one wheel or the other at the start of a tipping action by the chair.

These and other objects are accomplished by the improvements comprising the present invention, a preferred embodiment of which is disclosed herein as illustrating the best known mode of carrying out the invention. Various changes in details of construction and modifications thereof are comprehended within the scope of the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front perspective view of a three-wheeled electric powered chair embodying the invention; FIG. 2 is an enlarged elevational view of the front lower end of the wheelchair, as on line 2-2 of FIG. 1; FIG. 3 is a fragmentary plan elevation on line 3-3 of FIG. 2; FIG. 4 is a further enlarged fragmentary sectional view on line 4-4 of FIG. 2; FIG. 5 is a front elevational view similar to FIG. 2, showing one of the stabilizers engaging the ground or floor when the wheelchair is forced into a tipping motion when making a sharp turn; and FIG. 6 is a view similar to FIG. 5 showing the front wheel lifted above the ground as the chair continues to tilt.

PREFERRED MODE FOR CARRYING OUT THE INVENTION The electric powered wheelchair shown in FIG. 1 includes a seat 10 mounted on the rear portion of a frame having a floor board 11 supported on three load bearing wheels, namely, a pair of rear wheels 12 and a front steering wheel 13. The steering wheel is journaled in a yoke 14 on the lower end of a steering column 15, and the column is journaled in the upper end of a cowling 16 over the wheel 13 secured to the front end of the floor board 11.

A U-shaped bumper bar 17 mounted in the front end of the floor board 11 surrounds the steering wheel 13. The steering column 15 has a handle bar 19 at its upper end and an electric control switch box 20 is mounted on the handle bar. Storage batteries 21 carried on the rear portion of the frame furnish the electric power to drive the rear wheels 12.

The parts thus far described are embodied in the prior art wheelchair manufactured by Fortress Scientific previously referred to herein.

A pair of idler stabilizer wheels 22 is mounted one at each side of the front end portion of the floor board 11 immediately behind the steering wheel 13.

As shown in Fig. 2 the wheels 22 are mounted to normally be spaced above the ground or supporting surface, preferably about 3/4 to 1 inch. Preferably, the wheels 22 are journaled on the ends of a transverse horizontal shaft 23 extending under the front end of the floor board 11 and secured thereto by U-bolts 25 secured to the floor board and engirdling the shaft. As shown, the shaft 23 terminates a short distance beyond the sides of the floor board 11 so that the wheels 22 are mounted contiguous to the floor board. However, this is not critical as the shaft may be somewhat elongated to mount the wheel farther out from the floor board, while still accomplishing similar non-tipping results.

As shown in FIG. 4 the shaft 23 may be tubular and the wheels 22 journaled thereon by roller bearings 26 held on the shaft ends by retainer rings 27 and retainer pins 28 received in the ends of the shaft and secured therein by set screws 29 which engage the U-bolts 25 supporting the shaft. The wheels 22 are preferably durable solid plastic material.

The top speed of the wheelchair is five miles per hour and the steering wheel makes a full turn on a 40 inch radius so that the momentum of the chair and occupant when making a full turn at top speed causes a sudden and very substantial lateral or sideways tipping force on the vehicle. In actual practice the prior art wheelchair without the improved stabilizer system has been known to tip over and injure the occupant not only when driven at top speed but also at lesser speeds on irregular or sloping ground.

As shown in FIG. 5, when the wheelchair embodying the present stabilizer system starts to tip sideways for any reason, the wheel 22 on the lower side immediately roll ably contacts the ground and resists further tipping. FIG. S depicts the position when the steering wheel is making a full turn to the right as the wheelchair is proceeding forwardly at substantial speed, causing the wheelchair to tilt downwardly toward the left because of the forward momentum of the vehicle and its occupant.

As the wheelchair continues to tilt to the left, the left stabilizing wheel 22 causes the steering wheel 13 to lift off the ground as shown in FIG. 6 and the left stabilizing wheel, which is in fixed straight ahead rolling position, causes the chair to swing back toward straight ahead travel. On ground surfaces, as pressure builds up on the left stabilizing wheel and ground pressure reduces on the steering wheel in a sharp turn, the turning drive of the steering wheel reduces and the straight ahead guidance of the stabilizing wheel increases so that while the chair may continue to turn it will turn at a safe and lesser rate suitable to speed, slope and/or surface roughness.

Obviously, if the steering wheel 13 is turned to the left under the same conditions the wheelchair will start to tilt to the right. In either case further tilting is arrested by rolling contact with the ground by one of the stabilizer wheels which are proceeding in a straight forwardly direction, so that forward speed is not substantially reduced.

Due to the instability of a three-wheeled vehicle, there is always present the tendency to tip sideways due to a variety of ground conditions even though the steering wheel is not turned sharply. Such conditions include rough, stony, irregular and side-sloping terrain.

The present improved wheelchair has been tested in actual practice under all of the foregoing conditions and found to accomplish the stated objects of the invention.

Claims

1. In a powered three-wheel chair having a longitudinal frame, a seat supported on the rear portion of said frame, a pair of laterally spaced load bearing wheels rollably mounted in said frame rear portion, a load bearing steerable wheel mounted in the center front portion of said frame, a steering column operatively connected to said steerable wheel and extending upwardly therefrom, hand operable control means mounted on top of said column, the improvement comprising a pair of idler stabilizer wheels journaled in the front portion of said frame at the sides thereof.

2. In a powered three-wheel chair as in claim 1, wherein said stabilizer wheels are normally spaced slightly above the surface on which the three chair wheels are supported.

3. In a powered three-wheel chair as in claim 2, wherein a transverse horizontal shaft is mounted in the frame behind and closely adjacent to said steerable wheel, and said stabilizer wheels are journaled on the ends of said shaft.

4. In a powered three-wheel chair as in claim 3, wherein said stabilizer wheels are normally spaced about 3/4 inch to 1 inch above the surface on which the three chair wheels are supported.

5. In a powered three-wheel chair as in claim 4, wherein said stabilizer wheels are laterally contiguous to said frame.

6. In a powered three-wheel chair as in claim 2, wherein said stabilizer wheels are normally spaced about 3/4 inch to 1 inch above the surface on which the three chair wheels are supported.

7. In a powered three-wheel chair as in claim 6, wherein said stabilizer wheels are laterally contiguous to said frame.

8. In a powered three-wheel chair as in claim 2, wherein each of said stabilizer wheels is adapted to contact the ground when the chair is tilted sideways toward said stabilizer wheel due to a sharp turn by the steering wheel, and to cause the chair to swing back toward straight ahead travel as the steering wheel lifts off the ground.

9. A powered three-wheel chair substantially as herein described with reference to the accompanying drawings.