Wheelchair-attachable powered unit

Abstract

A powered unit is selectively attachable to a wheelchair to convert the wheelchair into a three-wheeled vehicle of considerable stability and capable of operating at relatively high speeds. The powered unit includes a frame structure coupled to a cylindrical member for pivotably receiving a fork assembly including a wheel and steering means in the form of a handle bar assembly. A gasoline powered engine is mounted on the frame structure so as to frictionally engage and drive the wheel. A pair of support legs of adjustable length extended downwardly from the frame structure so as to function together with the wheel to support the powered unit in an upright position when the powered unit is not attached to a wheelchair. Coupling of the powered unit to a wheelchair is accomplished by inserting and locking tubular members of the frame structure within mating tubular members fastened to the frame of the wheelchair, raising the front end of the wheelchair so as to elevate the front wheels thereof above the ground, and pinning the tubular members to hold the wheelchair in the raised position. With the support legs shortened so as to clear the ground, the resulting three-wheeled vehicle can be driven under the power of gasoline engine and steered by the handlebar, with one-handed control of the vehicle being made possible by a pair of handlebar mounted controls which respectively control engine speed and braking of the front wheel.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to powered vehicles for physically handicapped persons, and more particularly to a powered unit which may be joined to a conventional wheelchair to provide a powered vehicle of considerable stability for the paraplegic or other wheelchair user.

2. History of the Prior Art

One of the most serious problems of the paraplegic or other nonambulatory person confined to a wheelchair is that of mobility. Wheelchairs provide a limited mobility which is determined by the ability of the person to propel and control the wheelchair by hand. Powered wheelchairs which are extremely expensive as well as being heavy and cumbersome units provide a greater degree of mobility, but are still limited in terms of their stability, and particularly in terms of the speed at which they are capable of travelling. Such units, moreover, are relatively complex, requiring substantial maintenance, and are relatively uneconomical in terms of the cost and range of operation. Furthermore, there are many occasions in which powered wheelchairs are disadvantageous as compared with nonpowered chairs. For example, a paraplegic who is capable of driving a car may be required to fold his own wheelchair and place it inside the car when he enters the car and to follow a reverse procedure when he leaves the car. A powered wheelchair has proven to be too large and heavy in such situations.

Accordingly, it would be advantageous to provide a unit which may be coupled to a conventional nonpowered wheelchair to convert the wheelchair into a powered vehicle and which may be uncoupled from the wheelchair to permit normal use of the wheelchair when desired. Such powered unit should desirably be relatively small, inexpensive and of simple and lightweight construction. The powered unit should be such that conventional wheelchairs can be adapted for use therewith with a minimum of modification. Addition of the powered unit to the wheelchair should desirably result in a vehicle of considerable stability which is easily controlled, even by a person with limited arm use, and yet capable of being driven at relatively high speeds.

BRIEF SUMMARY OF THE INVENTION

This present invention provides a powered unit which includes a frame structure and a pivotable or steerable wheel. The wheel is rotatably mounted on a fork assembly which is in turn pivotably mounted within a cylindrical member forming a part of the frame structure. Steering means in the form of handlebars are coupled to the fork assembly within the cylindrical member. Engine means mounted on a frame assembly is coupled to drive the wheel.

The frame assembly which includes means for supporting the powered unit in an upright position when detached from a wheelchair is readily couplable by the user to the frame of a conventional wheelchair which has been appropriately modified, to form a powered, three-wheeled vehicle. The wheelchair is attached to the frame structure of the powered unit, and then with the wheelchair tilted back to elevate the front wheels thereof above the ground, the adapted portion of the wheelchair frame is pinned so as to hold the chair in the elevated position with the front wheels thereof raised above and out of the way of the ground and the large rear wheels thereof forming the rear wheels of the three-wheeled vehicle. The support means for the powered unit are thereafter raised out of the way of the ground.

The resulting portable unit is relatively simple, inexpensive, small and lightweight. It is easily attached to a conventional wheelchair which has been appropriately modified, to provide a simple and economical vehicle which is easily controlled and yet which is capable of relatively high speeds so as to greatly enhance the mobility of the paraplegic or other nonambulatory person.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of a preferred embodiment of the invention, as illustrated in the accompanying drawings, in which:

FIG. 1 is a perspective view of a powered unit in accordance with the invention together with a conventional wheelchair which has been adapted for use with the powered unit;

FIG. 2 is a side view of the powered unit and wheelchair of FIG. 1 upon being joined together;

FIG. 3 is a top view of the powered unit of FIG. 1 together with the mating members added to the wheelchair to adapt the wheelchair;

FIG. 4 is a perspective view of the frame structure of the powered unit of FIG. 1; and

FIG. 5 is a sectional view of a portion of the arrangement of FIG. 3 taken along the line 5--5 thereof.

DETAILED DESCRIPTION

The various figures of drawing illustrate a powered unit 10 according to the invention and a conventional wheelchair 12 which has been adapted for use with the powered unit 10. The wheelchair 12 includes a pair of relatively large rear wheels 14 and 16 which are of the type having set-apart outer rims for manipulation by hand by the paraplegic user to propel the wheelchair 12. The wheels 14 and 16 are mounted on a frame structure 18 for the wheelchair 12 together with a pair of relatively small castor wheels 20 and 22. The wheelchair 12 has first coupling means in the form of a pair of hollow, elongated, generally tubular members 24 and 26 pivotably mounted on the opposite sides of the frame member 18 by volts 28 and 30. The tubular members 24 and 26 may be pivoted relative to the wheelchair 12 to permit the wheelchair 12 to be raised and locked in the raised position upon being coupled to the powered unit 10, as described hereafter. The tubular members 24 and 26 comprise the only elements which need be attached to the wheelchair 12 in order to adapt the wheelchair 12 for use with the powered unit 10. The powered unit 10 has a U-shaped frame 34, a front driving wheel 36 pivotably mounted on the frame 34 at the midpoint of the curve of the U-shaped frame 34, and a handlebar assembly 38 coupled to the wheel 36 through the frame 34 to permit pivoting movement of the wheel 36 by hand relative to the frame 34, as is described more fully hereinafter.

The frame 34 includes a hollow, generally cylindrical member 40 of the type used in bicycles for receiving a bicycle fork assembly 42 in which the front wheel 36, also of conventional bicycle design, is rotatably mounted. The handlebar assembly 38 extends through the top end of the cylindrical member 40 where it is coupled to the fork assembly 42. The frame structure 34 includes a second clamping means detachably cooperatively connectible to the first coupling means for connecting the frame structure 34 to the wheelchair. This second coupling means includes a pair of elongated, tubular members 44 and 46 which comprise part of the frame structure 34 extending rearwardly from the cylindrical member 40 in parallel directions away from the front wheel 36. A pair of support legs 48 and 50 are coupled to the tubular members 44 and 46 respectively so as to extend downwardly therefrom. When the powered unit 10 is detached from the wheelchair 12 the lower ends of the support legs 48 and 50 rest on the ground so as to support the powered unit 10 in an upright position together with the front wheel 36. A front wheel frictional drive motor assembly 52 is mounted just in front of the cylindrical member 40 and over the front wheel 36 to selectively engage and drive the front wheel 36.

As best seen in FIG. 4 as well as FIG. 3 the tubular members 44 and 46 of the frame structure 34 of the powered unit 10 have forward ends attached to the cylindrical member 40 such as by welding and short forward portions which extend rearwardly from the member 40 in parallel relation to each other. The members 44 and 46 then curve outwardly so as to extend in directions away from each other before again bending so as to extend in parallel directions toward the rear of the powered unit 10 and away from the cylindrical member 40. The tubular members 44 and 46 terminate in tubular elements 56 and 58 respectively. The tubular members 44 and 46 are hollow and of approximately the same size as the tubular members 24 and 26 mounted on the wheelchair 12. The elements 56 and 58 have outer diameters just slightly smaller than the inner diameters of the tubular members 44 and 46 so as to be receivable within the ends of the members 44 and 46 where they are held in place by wing nuts 60 and 62 respectively. At the point where the tubular members 44 and 46 curve outwardly so as to extend in directions away from each other, they are joined by a spacer bar 64. The tubular members 44 and 46, the spacer bar 64 and the tubular elements 56 and 58 lie in a common plane which is generally horizontal with respect to the ground when the powered unit 10 is supported by the legs 48 and 50.

The wheelchair 12 which has been altered only by the addition of the members 24 and 26 may be used in the conventional fashion without interference by the members 24 and 26. When the user desires to convert the wheelchair 12 into a three-wheeled, powered vehicle, he moves the wheelchair 12 toward the powered unit 10. With the tubular members 24 and 26 held in a raised position so as to be generally horizontal and generally coaxial with respect to the members 44 and 46, he inserts the elements 56 and 58 into the members 24 and 26. The tubular members 24 and 26 are of similar size to the members 44 and 46 so as to have inner diameters just slightly larger than the outer diameters of the elements 56 and 58. The tubular elements 56 and 58 are locked in place within the members 24 and 26 by spring-loaded locking pins 65 and 66 which snap into place within apertures 67 and 68 in the tubular members 24 and 26.

The user suspends the front wheels 20 and 22 of the wheelchair 12 above the ground for clearance (typically 21/2 -3 inches) by pushing down on the handlebar assembly 38 or the wheels 14 and 16 so as to raise the front end of the wheelchair. In some instances this process can be facilitated by use of a ramp 70 placed just in front of the front wheels 20 and 22 of the wheelchair 12. The wheelchair 12 and coupled powered unit 10 are pushed forward, rolling the castor wheels 20 and 22 up onto the ramp 70 to elevate the front of the wheelchair 12.

As the front end of the wheelchair 12 is raised, the tubular members 24 and 26 which have been coupled to the tubular elements 56 and 58 pivot about the bolts 28 and 30 and relative to the wheelchair 12 so as to assume different positions relative to the wheelchair 12. When the wheelchair 12 is in the tilted position, the tubular members 24 and 26 are pinned to the frame structure 18 of the wheelchair 12 to lock the wheelchair 12 in the tilted position. Locking is accomplished by inserting pins 72 and 74 suspended by chains 76 and 78 from the tubular elements 44 and 46 through apertures 80 and 82 in the tubular members 24 and 26 and into apertures 84 and 86 in the frame structure 18 of the wheelchair 12. The locking of the tubular member 24 to the frame structure 18 is shown in detail in FIG. 5. The tubular member 26 is locked to the other side of the frame structure 18 in the same fashion.

The leg 48 is comprised of a first tubular element 88 fastened to the tubular element 56 and extending into a larger tubular element 90. Similarly the other leg 50 is comprised of telescoping tubular elements 92 and 94. The element 88 has a spring-loaded pin 96 therein which engages either of a pair of apertures 98 and 100 within the element 90. Similarly the element 92 has a spring-loaded pin 102 which engages either of a pair of apertures in the element 94. When the pin 96 resides within the aperture 98, the leg 48 is held in a long-length condition in which it rests on the ground to support the powered unit 10 as seen in FIG. 1. With the pin 96 in the aperture 100, the leg 48 is held in a short-length condition in which the lower end thereof clears the ground by several inches as seen in FIG. 2. The pin 102 within the other leg 50 functions in the same fashion to hold the leg 50 in long-length or short-length conditions.

When the wheelchair 12 is coupled to the powered unit 10, the legs 48 and 50 are not needed to support the powered unit 10. Accordingly the occupant of the wheelchair 12 reaches down and depresses the pin 96 to start the tubular element 90 sliding upwardly along the tubular element 88. When the aperture 100 reaches the pin 96, the pin 96 springs out through the aperture 98 to lock the leg 48 in the short-length condition. At the same time the other leg 50 is raised in similar fashion, so that both legs are positioned above and away from the ground. With the wheelchair 12 uncoupled from the powered unit 10, the legs 48 and 50 are needed for support. Accordingly, prior to uncoupling the wheelchair 12 from the powered unit 10, the occupant of the wheelchair 12 reaches down and depresses the pin 96 to remove it from the aperture 100 and permit commencement of a sliding motion of the element 90 downwardly along the element 88. When the pin 96 reaches the aperture 98 it snaps into the aperture 98 to lock the leg 48 in the long-length condition. The other leg 50 is extended in similar fashion prior to uncoupling the wheelchair 12 from the powered unit 10.

With the wheelchair 12 joined to the powered unit 10, the respective frame structure 18 and 34 effectively become a single frame structure for a powered, three-wheeled vehicle. The rear wheels 14 and 16 of the wheelchair 12 serve as the rear wheels for the vehicle. The wheel 36 of the powered unit 10 serves as the front wheel for the vehicle. The castor wheels 20 and 22 of the wheelchair 12 are held in a raised position out of the way of the ground. Similarly, with the legs 48 and 50 assuming the short-length condition, the lower ends thereof are held in elevated positions above the ground. Where the ramp 70 is used in the process of joining the wheelchair 12 to the powered unit 10, it is a simple matter for the person occupying the wheelchair 12 to reach down, pick up the ramp 70 and store it in a convenient location.

The front wheel frictional drive motor assembly 52 may be of any appropriate size and configuration, but preferably is of the type sold under the trademark "SOLEX" by Solex Company of Paris, France. The Solex unit is ideally suited for this type of application since it utilizes a relatively small gasoline engine which is easy to start and which is economical to operate. Because of engine's economy, only a small gas tank is required. The Solex unit also includes a small generator which may be used to power lights and other accessories for the vehicle. The power produced by the Solex unit is relatively low compared to that of other vehicles, and yet is adequate for vehicles in accordance with the invention.

The Solex unit engages the front wheel 36 through a frictional drive arrangement which may be disengaged by a clutch control 104 when desired. Normally, however, it is not necessary to disengage the clutch via the control 104 where the engine is to be started by accelerating the vehicle to a low speed. In such instances a compression control lever 106 mounted on the handlebar assembly 38 is manually actuated by the occupant of the wheelchair 12 so as to reduce the compression within the engine and thereby allow the vehicle to be accelerated by hand to a nominal speed on the order of several miles an hour. When the nominal speed is reached the lever 106 is hand actuated to restore the compression and thereby start the engine.

When it is desired to start the engine by means other than forward acceleration of the vehicle by hand, other appropriate arrangements can be used. One such arrangement utilizes a rope starter of the type commonly used in connection with lawn mower engines. The rope starter is mounted on the side of the Solex unit. The occupant of the wheelchair 12 reaches forward and pulls the rope starter to start the engine. In a still different arrangement a wind-up starter can be used. Still other arrangements including electric starters can be used where desired or appropriate.

The handlebar assembly 38 comprises a closed, generally oval-shaped loop. It has been found that this particular configuration is easier to handle than the more conventional bicycle handlebar configuration. In particular, the closed loop handlebar configuration allows the occupant of the wheelchair 12 to exercise complete control over the vehicle with one hand while sitting comfortably in the wheelchair 12. This is made possible, in part, by the location of a speed control 108 and a handbrake control 110 within close proximity of one another on the handlebar assembly 38. With this particular arrangement the gas unit 52 may be set to normally propel the vehicle forward at an optimum speed. In such instances the speed control 108 which is coupled by a cable 112 to the motor assembly 52 is operative to decelerate the motor assembly 52 when manipulated. Alternating the speed control 108 can be coupled to accelerate the motor assembly 52 when manipulated. The control 110 is coupled by a cable 114 to a conventional bicycle caliper brake 116 mounted on the fork assembly 42.

The controls 108 and 110 are located close to one another so as to be simultaneously operable by the occupant of the wheelchair 12 using one hand. At the same time the occupant's hand rests on the handlebar assembly 38 to effect more than adequate steering control under all but the most demanding of situations. When the speed control 108 is coupled to operate as a deceleration rather than an acceleration and the controlss 108 and 110 are completely released, the operator need only steer the vehicle as the vehicle propels itself forward at the optimum speed. Where the situations require some deceleration, the control 108 is actuated in varying degrees to achieve the desired amount of deceleration. If more rapid deceleration is desired or required, the hand brake control 110 can be actuated together with or in lieu of the speed control 108. Where the speed control 108 is coupled as an acceleration, it is a simple matter either manipulate the control 108 to achieve a desired speed or manipulate the control 110 where braking action is desired, all using the same hand which is used to steer the vehicle.

When it is desired to uncouple the wheelchair 12 from the powered unit 10, ramp 70 is positioned under the castor wheels 20 and 22, the legs 48 and 50 are restored to the long-length condition in the manner previously described, and the pins 72 and 74 are removed from the apertures 80, 82, 84 and 86. The wheelchair 12 is then rolled off of the ramp 70, following which the tubular elements 56 and 58 are uncoupled from the members 24 and 26 by first depressing the pins 65 and 66 and then slowly backing the wheelchair 12 away from the powered unit 10 so as to slide the tubular elements 56 and 58 out of the tubular members 24 and 26. Again, the ramp 70 may not be necessary during the uncoupling operation, as where the occupant of the wheelchair is able to steady the wheelchair 12 while pulling the pins 72 and 74 and then lower the front of the wheelchair 12 to the ground.

It will be appreciated that because of the relatively simple and lightweight construction of the powered unit 10, it is not only easily coupled to and uncoupled from the wheelchair 12, but in particular is easily handled upon uncoupling by the occupant of the wheelchair 12. Typical powered units 10 according to the invention weigh on the order of 40-45 lbs. Accordingly it is a relatively simple matter for the occupant of the wheelchair 12, upon uncoupling from the powered unit 10, to lift the unit 10 by hand and place it in a desired location such as in the trunk of a car. The vehicle itself which is formed by joining the powered unit 10 to the wheelchair 12 is of remarkably stable construction with the weight being substantially equally distributed among the three wheels 14, 16 and 36. Such vehicles have been found capable of operating safely at speeds on the order of 20-25 miles an hour.

Various accessories and modifications can be used as appropriate. For night time operation a headlight 118 is mounted to the top left of the motor assembly 52 and is powered by the small generator contained within the unit 52. A tail light (not shown) can be mounted on the rear of the wheelchair 12 and electrically coupled to the generator within the motor assembly 52 via wires running along the tubular members 24, 26, 44 and 46 and including coupling plugs to permit uncoupling of the wheelchair 12 from the powered unit 10.

While the invention has been particularly shown and described with reference to a preferred embodiment thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.

Claims

What is claimed is:

1. A power attachment for use with a wheelchair of the type having a pair of hand operable drive wheels rotatably mounted on a frame having at least one castor wheel fixed against translation with respect to the frame, the power attachment comprising:

a powered unit frame,

at least one front wheel pivotally mounted on said powered unit frame, motor means mounted on said powered unit frame and selectively couplable to drive said front wheel,

steering means coupled to said front wheel and being hand operable to pivot said front wheel relative to said powered unit frame,

first coupling means connectable to the wheelchair,

second coupling means connected to said powered unit frame for detachable connection to said first coupling means,

first locking means for detachably locking said first and second coupling means together when said first coupling means is connected to the wheelchair and the wheelchair is supported on the drive wheels and castor wheel, and

second locking means for locking said detachably locked first and second coupling means relative to the wheelchair frame when the wheelchair is tilted about the axis of the drive wheels and for maintaining the lowest portion of the caster wheel above the plane defined by the lowest portion of the drive wheels and the lowest portion of the front wheel.

2. The power attachment of claim 1 wherein

said first coupling means includes at least a first elongated element,

said second coupling means includes at least a second elongated element,

said elongated elements telescopically movable with respect to one another, and

said first locking means includes means for locking said first and second elongated elements together when in telescoped relationship with one another.

3. The power attachment of claim 1 wherein said second locking means includes a pin securing said detachably locked first and second coupling means to the wheelchair frame.

4. The power attachment of claim 1, further including a pair of support legs mounted on said powered unit frame structure, said legs being adjustable between a long length position in which the legs rest on the ground to support the powered unit frame together with said front wheel when said powered unit frame is unconnected to the wheelchair and a short length position in which the legs are raised above the ground when said powered unit frame is connected to the wheelchair by said first and second coupling means and said first and second locking means.

5. The power attachment of claim 1 wherein said steering means includes a handlebar forming a closed loop and including control means mounted on said handlebar, said control means including means for selectively varying the speed of said motor means and means for braking said front wheel.

6. A power attachment for use with a wheelchair of the type having a pair of hand operable driving wheels and at least one castor wheel, the power attachment comprising:

a frame structure adapted to be selectively coupled to a wheelchair and when coupled to the wheelchair to hold the wheelchair in a tilted position so as to elevate the castor wheel,

a front wheel pivotably mounted on the frame structure,

steering means coupled to the wheel and being hand operable to pivot the wheel relative to the frame structure,

motor means mounted on the frame structure and selectively couplable to drive the wheel, and wherein the frame structure includes at least two pairs of tubular members, each pair of tubular members comprising a first tubular member telescopically engageable with a second tubular member to join the two members, the first member of each pair being coupled to a portion of the frame structure opposite said front wheel and the second member of each pair being adapted to be pivotably mounted on the wheelchair and means for detachably locking the second member in a fixed position on the wheelchair with the wheelchair tilted to elevate the castor wheels.

7. A combination vehicle for transporting nonambulatory persons comprising:

a wheelchair having a frame structure and first and second wheels of the type normally rotated by hand by a person using the wheelchair, the first and second wheels forming a pair of rear wheels for the combination vehicle, a pair of fourth and fifth wheels mounted forwardly of the first and second wheels on the wheelchair, the frame structure of the wheelchair including at least one elongated, first element;

a second frame structure detachably coupled to the frame structure of the wheelchair, the second frame structure including an elongated second element, the first and second elongated elements being telescopically engageable to join the second frame structure to the frame structure of the wheelchair and selectively disengageable to separate the second frame structure from the frame structure of the wheelchair and wherein said elongated first element is pivotably mounted on the frame structure of the wheelchair and is lockable to the frame structure of the wheelchair to hold the fourth and fifth wheels in an elevated position after the elongated second element is engaged with the elongated first element;

a third wheel pivotably mounted on the second frame structure and forming a front wheel for the combination vehicle;

steering means coupled to the third wheel and being hand operable from the wheelchair to pivot the third wheel relative to the second frame structure and thereby steer the combination vehicle; and

self-contained motor means mounted entirely on the second frame structure and selectively couplable to drive the third wheel and thereby power the combination vehicle.

8. The invention defined in claim 7 wherein the second frame structure includes means extendable into a support position so as to function with the third wheel to hold the second frame structure in an upright position when the frame structure of the wheelchair is uncoupled from the second frame structure.

9. The invention defined in claim 7, wherein the second frame structure is operative to hold the wheelchair at an angle such that the fourth and fifth wheels of the wheelchair are elevated relative to the first and second wheels of the wheelchair after the second frame structure is coupled to the frame structure of the wheelchair.

10. A detachable power unit for use with a wheelchair of the type having a frame, a pair of normally hand operated wheels mounted on the frame, and a pair of castor wheels pivotably mounted on the frame, the power unit comprising

a substantially horizontal, open ended, U-shaped frame;

a rotatable driving wheel pivotably mounted on the U-shaped frame,

hand operable means for pivotally steering the driving wheel,

self-contained motor means mounted on the U-shaped frame,

motor engaging means for selectively, frictionally engaging the self-contained motor means with the driving wheel to cause the driving wheel to rotate, and

connecting means mounted on the wheelchair frame for removably engaging the U-shaped frame with the wheelchair frame and for thereafter holding the wheelchair in a tilted position to elevate the castor wheels while the wheelchair frame and the U-shaped frame are engaged with each other.

11. A detachable power unit for a wheelchair as recited in claim 10, wherein the connecting means include means mounted on the wheelchair frame for pivotably engaging the U-shaped frame with the wheelchair while the wheelchair is resting on all of its wheels, and means for locking the U-shaped frame to the wheelchair frame after the user places the wheelchair in a tilted position to hold the wheelchair castor wheels off of the ground.

12. A detachable power unit for a wheelchair as recited in claim 10, wherein the U-shaped frame includes a pair of integrally mounted, parallel first elongated members which together lie in a plane which is substantially horizontal, and the connecting means include a pair of elongated second members pivotably mounted on the wheelchair frame, at least one of the first and second pair of elongated members being hollow and the first and second pairs of elongated members being telescopically engageable with each other to connect the power unit to the wheelchair, and means for locking the second elongated members to the wheelchair frame after the user places it in a tilted position to hold the wheelchair castor wheels off of the ground when the wheelchair is connected to the power unit.

13. A detachable power unit for a wheelchair as recited in claim 12, wherein the wheelchair frame includes a seat portion and a pair of second elongated members are pivoted to the wheelchair frame above the seat portion.

14. A detachable power unit for a wheelchair as recited in claim 10, wherein the self-contained motor means include a drive shaft and is mounted to the U-shaped frame over the driving wheel and the motor engaging means include means for selectively, frictionally engaging the drive shaft with the driving wheel.

15. A detachable power unit for a wheelchair as recited in claim 10, wherein the power unit further comprises a pair of downwardly extending, telescoping legs attached to the U-shaped frame for helping to support the power unit when it is unconnected to the wheelchair.

16. A detachable power unit for a wheelchair as recited in claim 10, wherein the power unit further comprises control means mounted on the hand operable steering means, the control means including means for selectively varying the speed of the motor means and means for braking the driving wheel.