US3566986A

US3566986A - Self-propelled wheelchair

Info

Publication number: US3566986A
Application number: US824907*A
Authority: US
Inventors: Per Edward Carl Udden
Original assignee: Individual
Current assignee: Individual
Priority date: 1965-04-09
Filing date: 1969-05-15
Publication date: 1971-03-02
Anticipated expiration: 1988-03-02

Abstract

A pair of nonsteerable main wheels are disposed at opposite sides of the frame of the wheelchair. A drive unit is disposed at the rear of the frame and is swingably interconnected therewith. This drive unit includes a drive motor and a pair of driving wheels. A self-braking driving transmission connects the motor with the driving wheels. A steering motor is also incorporated in the unit and a self-braking transmission connects the steering motor with a member fixed to the frame to cause swinging movement of the unit with respect to the frame.

Description

[ 6] References Cited UNITED STATES PATENTS 1,233,846 7/1917 Cochran..... 180/65UX 2,305,578 12/1942 Ulinski 180/791 2,482,203 9/1949 Peterson et al. 180/65 2,978,053 4/1961 Schmidt 180/65X 3,280,931 10/1966 Cahill et 180/23 Primary Examiner-A. Harry Levy Attorney-Fred Philpitt ABSTRACT: A pair of nonsteerable main wheels are disposed at opposite sides of the frame of the wheelchair. A drive unit is disposed at the rear of the frame and is swingably interconnected therewith. This drive unit includes a drive motor and a of driving wheels. A self-braking driving transmission cts the motor with the driving wheels.

Per Edward Carl Udden General Delivery, Timra, Sweden [21] Appl. No. 824,907

May 15,1969

[] Patented Mar. 2, 1971 Apr. 9, 1965 Sweden 4698/ Continuation-impart of application Ser. No. 751,016, June 7, 1968, now abandoned which is a continuation of application Ser. No. 540,652, Apr. 6, 1966, now abandoned 8 Claims, 5 Drawing Figs. [52] US.

United States Patent [72] Inventor [22] Filed [32] Priority [54] SELF-PROPELLED WHEELCHAIR pair conne A steering motor is also incorporated in the unit and a self-braking transmission connects the steering motor with a member fixed to the frame to cause swinging movement of the unit with respect to the frame.

7 180/26, 180/42, ISO/79.1

Int.

B60k 17/30 [50] Field 180/52, 42,

26, 65, 60, 15 (MWC), 791

PATENTED MR 2 [EH SHEET 1 OF 5 SELF-PROPELLED WHEELCHAIR CROSS-REFERENCE TO RELATED APPLICATION The present application is a continuation-in-part of a streamlined continuation application Ser. No. 751,016 filed on Jun. 7, 1968 by Per E. C. Udden for Motor-Powered Wheelchair, which in turn was a continuation of parent application Ser. No. 540,652, filed Apr. 6, 1966 by Per E.C. Udden for Motor-Powered Wheelchair, the latter two cases having since become abandoned.

BACKGROUND OFTHE INVENTION Wheelchairs must enable a patient to move around indoors in a safe and flexible manner. A principal requirement is that the dimensions of the wheelchair must be kept within as narrow limits as possible, and the steerable wheels should be arranged so that the radius of turnnof the chair is as small as, possible. As a result of these requirements, the classic design of a wheelchair has evolved characterized by large main wheels located at opposite sides of the wheelchair and one or two smaller wheels disposed either in front of or be-hind the main wheels and comprising link rollers with vertical pivots.

This type of wheelchair is not practical for use in outdoorapplications unless the supporting ground surface is quite smooth and hard.

Motor-powered or self-propelled wheelchairs have been developed for indoor use or for use onhard ground where there are obstacles such as curbs or the like. Prior art wheelchairs have been provided with an electrical motor and with large front wheels on each side of the wheelchair along with rear steerable wheels controlled by the electric motor and positioned a certain distance behind the seat of the wheelchair in order to provide space for the motor and to enable the driving function to be carried out. This latter type of wheelchair is excessively large compared with a wheelchair of conventional design and accordingly is impractical for use indoors. Additionally, such wheelchairs have a tendency to turn over too easily when taking sharp turns or when turning at high speeds. Other types of wheelchairs have been designed for outdoor use including an electric motor and being capable of climbing over relatively difficult obstacles orslopes. However, such vehicles are not suitable for indoor use on flat surfaces or in hospitals or the like.

SUMMARY OF THE INVENTION associated supporting surface. This drive shaft is in turn connected by a self-braking transmission with the driving wheels of the driving unit so that the driving wheels will be held. in position when driving current to the electric driving motor is interrupted.

The swingable unit includes a steering motor which is interconnected through a self-braking transmission with a member fixed to. the frame of the wheelchair so that the unit can be swung with respect to the wheelchair. The unit will a.ccordingly remain in a fixed relationship withnrespect to the wheelchair when current is. interrupted to the steering motor. The unit is swingable about an axis extending substantially perpendicular to an associated supporting surface.

DESCRIPTION OF THE DRAWINGS.

FIG. 1 is a top rear perspective view illustrating a wheelchair according to the present invention;

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings wherein like reference characters designate corresponding parts through out the several views, the wheelchair of the present invention as seen in FIGS. 1 and. 2 includes. a frame 1 of steel tubing provided with a cushion 2 and a backrest 3. The source of electrical energy for driving the wheelchair comprises electrical batteries 4 located below the seat and disposed between the two relatively large front wheels 5 which are not steerable. This portion of the frame also supports armrests 6 and footrests 7 as well as a control box 8 comprising means for electrically controlling the chair. Control box 8 is swingable around a substantially vertical axis 9 mounted on one of the armrests6. In this manner, the control box can be swung away thus enabling the patient to drive the wheelchair very close to a table or the like.

A generally L-shaped frame portion-l0 is disposed at each side of the'chair:. The upper horizontal part of each L-shaped, frame portion is mounted for swinging movement about a pivot 11 located: adjacent the backrest 3. In this manner, the frame portion 10 andaccordingly theassociated armrest 6 and the footrest 7 can be swung outwardly as seen in FIG. 2 to. make it easier for the patient to move onto or off of the seat of the wheelchair,

A wheel 12 is provided for operating screw means whereby the footrest 7 can be raised or lowered. by altering the angle between the horizontal part of frame 10 and the downwardly extending part which carries the footrest 7.

A driving unit includes an electric traction motor 13 the drive shaft of which extends substantially parallel with the associated supporting surface and which transmits torque to the rear wheels 14 of the drive unit. These rear wheels are supported by a fork, 15. A steering motor 17 isarranged to swing the driving unit through the intermediary of a self-braking steering transmission indicated generally by reference numeral 16 around a substantially vertical shaft 19. The steering motor 17 isdrivingly interconnected with a steering transmission through a belt 18. Shaft 19 is fixed to a casing 20 enclosing various electrical control equipment such as relays, etc., necessary for the driving and steering of the chair. This casing 20 is rigidly connected to the backrest of the chair in any suitable manner and the entire driving unit swings with respect to the frame 1, the casing 20 and the shaft 19 as hereinafter more fully described.

Referring now to FIG. 3. of the drawings, the current to the steering motor 17 is preferably supplied through a resetting servodevice comprising two potentiometers. A master potentiometer 22 and a slave potentiometer 23 are provided and are arranged in, a bridge circuit. The position of the slave contact 26 of the potentiometer 23 corresponds to the position of the swingable unit with respect to the frame. The master potentiometer 22 is preferably mounted on one of the armrests 6 of the'chair and displacing of its contact 27 by means of a knob 21 results in a potential difference across the bridge which is fed to the steering motor through the intermediary of

amplifiers

24 and 25. A displacement of the master potentiometer thus results in a potential difference across the bridge circuit which will cause the steering motorto turn the swingable unit in a direction so as to eliminate the potential difference across the bridge.

If this potential difference is less than a predetermined value, one of two 6-volt circuits will be completed across the steering motor depending on the polarity of the potential dif- 5 ference.

if, however, the potential difference is greater than said predetermined value, one of two l2-volt circuits will be completed across the steering motor thereby changing the position of the slave contact 26 on the potentiometer 23 which results in elimination of the potential difference. At a certain value of this difference, the l2-volt circuit across the steering motor is interrupted and the 6-volt circuit is activated. The steering motor will therefore continue in the same direction but at a lower speed until the potential difference is eliminated.

To cause the steering of the wheelchair to be accurate, the resistance winding of the slave potentiometer is preferably made with a higher resistance per degree of turning movement in its central portion than in its end portions against which the contact 26 rests when the swingable unit is turned in either direction. The master potentiometer on the other hand is of a construction so that a lower resistance per degree of turning movement is provided in a central portion than in the end portions thereof. When the contact 27 engages the central portion of the master potentiometer, this position corresponds to the relationship wherein the swingable unit is positioned for straight forward movement of the wheelchair.

Referring now to FIGS. 4 and of the drawings, the selfbraking driving transmission and steering transmission are more fully described. The electric traction motor 13 includes the driving shaft 30 which is suitably journaled within the surrounding casing portion 31 and which is drivingly connected with a worm screw 32. This worm screw 32 meshes with a worm wheel 34 which in turn is drivingly connected through a differential indicated generally by reference numeral 36 in FIG. 5 which the two

output shafts

38 and 40 to which the driving wheels are operatively connected.

The belt 18 previously described as being operatively connected with the steering motor 17 is also operatively connected with a pulley 50 fixed to the outer end of a shaft 52 suitably journaled in casing 60. This shaft is drivingly connected with a worm screw 54 which meshes with a worm wheel 56 as seen in i6. 4. This worrn wheel 56 is fixed to the vertical shaft 19 previously described which is in turn fixed to casing 20 and the frame of the wheelchair. The upper portion 60 of the casing of the driving unit is connected to the lower portion 31 previously described and is rotatably journaled on shaft 19 by means of suitable bearing 62.

The driving transmission as well as the steering transmission comprises worm gearing having a high transmission ratio which is for example 1:25 or greater. This insures that a selfbraking action is obtained. The term self-braking accordingly means a transmission wherein the components will be held in fixed relationship when no power is applied to the transmission. Accordingly, in effect, the transmission serves as a brake since the components are held against movement when not power driven. It is apparent that actuation of the steering motor will cause the entire driving unit to swing about fixed shaft 19 so as to obtain the desired steering of the wheelchair,

As this invention may be embodiment in several forms without departing from the spirit or essential characteristics thereof, the present embodiment is therefore illustrative and not restrictive, and since the scope of the invention is defined by the appended claims, all changes that fall within the metes and bounds of the claims or that form their functional as well as conjointly cooperative equivalents are therefore intended to be embraced by those claims.

I claim:

1. A self-propelled wheelchair comprising a frame, a pair of nonsteerable main wheels supporting said frame and disposed at opposite sides thereof, a drive unit swingably interconnected with said frame, said drive unit including a drive motor and a pair of driving wheels, said main wheels comprising the front wheels of the wheelchair, said driving wheels comprising the back wheels of the wheelchair, driving transmission drivingly connecting said drive motor and said driving wheels, said driving transmission being self-braking when said driving motor is not operating, said drive unit also including a steerin motor, a steering transmission operatively connecting sai steering motor and said unit for swinging said unit and said drive motor and said steering motor relative to said frame, said steering transmission being self-braking when said steering motor is not operating, said drive motor including a drive shaft extending substantially parallel with an associated supporting surface, said drive unit being swingable about an axis extending substantially perpendicularly to said associated supporting surface.

2. Apparatus as defined in claim 1 wherein said driving transmission includes worm gearing and a differential.

3. Apparatus as defined in claim 1 wherein said steering transmission includes a worm wheel fixed with respect to said frame, and a worm screw engaging said worm wheel, said worm screw being operatively connected with said steering motor.

4. Apparatus as defined in claim 1 wherein said driving transmission includes a worm screw drivingly connected with said driving motor, a worm wheel engageable with said worm screw, said worm wheel being drivingly connected with said driving wheels, said steering transmission including a worm wheel fixed with respect to said frame, a worm screw engageable with said last-mentioned worm wheel, said last-mentioned worm screw being operatively connected with said steering motor.

5. Apparatus as defined in claim 1 including a source of electrical current for said steering motor, means connecting said source of current with said steering motor and including a resetting servodevice comprising two potentiometer including a master potentiometer and a slave potentiometer arranged in a bridge circuit, said slave potentiometer having a slave contact the position of which corresponds to the relative position between said drive unit and the frame, said master potentiometer having a contact for producing a potential difference across the bridge which will cause the resetting servodevice to turn the swingable drive unit in a direction so as to eliminate said potential difference.

6. Apparatus as defined in claim 2 wherein said slave potentiometer has a higher resistance per degree of turning movement in its central portion than its end portions.

7. Apparatus as defined in claim 2 wherein said master potentiometer has a lower resistance per degree of turning movement in its central portion than in its end portions.

8. Apparatus as defined in claim 2 wherein a small electrical current through said bridge circuit results in a low-speed operation of the steering motor, and a large current through the bridge circuit results in high-speed operation of the steeringmotor.

Claims

1. A self-propelled wheelchair comprising a frame, a pair of nonsteerable main wheels supporting said frame and disposed at opposite sides thereof, a drive unit swingably interconnected with said frame, said drive unit including a drive motor and a pair of driving wheels, said main wheels comprising the front wheels of the wheelchair, said driving wheels comprising the back wheels of the wheelchair, driving transmission drivingly connecting said drive motor and said driving wheels, said driving transmission being self-braking when said driving motor is not operating, said drive unit also including a steering motor, a steering transmission operatively connecting said steering motor and said unit for swinging said unit and said drive motor and said steering motor relative to said frame, said steering transmission being self-braking when said steering motor is not operating, said drive motor including a drive shaft extending substantially parallel with an associated supporting surface, said drive unit being swingable about an axis extending substantially perpendicularly to said associated supporting surface.

8. Apparatus as defined in claim 2 wherein a small electrical cUrrent through said bridge circuit results in a low-speed operation of the steering motor, and a large current through the bridge circuit results in high-speed operation of the steering motor.