ParaMedical Technologies



This Wheelchair Drive-Assistance device is designed to eliminate the complex arm motions at awkward wrist angles required to propel a manual wheelchair by its occupant, motion that can greatly contributes to rotator cuff tears and median nerve damage, which can possibly lead to carpal tunnel syndrome, affecting roughly one-half of manual wheelchair users. Unlike other such devices the Wheelchair Drive-Assistance device does not utilize cranks, gears or ratchets in its operations. Moreover the Wheelchair Drive-Assistance device behaves as an integral brake when slowing or stopping are required.



There are three basic classes of conventional wheelchairs for the mobility-disabled: the ordinary manual wheelchair, the fully-powered electric wheelchair, and the power-assisted manual wheelchair.   Propulsion of ordinary manual wheelchairs is provided by the occupant by means of grip-rings secured to the rim of each main wheel.   

The fully-powered electric wheelchair has generally four to six equally sized wheels, with two or more wheels electrically powered and is controlled by a joy stick, thereby allowing controlled power to reach any of the powered wheels.  The power-assisted ordinary wheelchair is an conventional wheelchair powered by either a detachable electric motor drive through fraction wheels that contact the main tires or by powered hubs, both using electric batteries as a power source.

Compared to the ordinary manual wheelchair the fully-powered wheelchairs are significantly heavier.   The powered wheelchair is a formidable vehicle and is far too heavy to be lifted and indeed requires ramps for access.    In this regard the powered wheelchair provides less mobility than the manual wheelchair. These fully-powered wheelchairs are for the mobility-disabled who are unable to operate an ordinary wheelchair for any sustained distance because of various disabilities or illnesses.

The compromise or power-assisted ordinary wheelchair is sufficiently heavier with its motors and battery compared to the manual wheelchair that is difficult to collapse and store.    It is generally recommended for those who become overly fatigued by operation of ordinary wheelchairs.


For ordinary manual wheelchairs, the mobility-disabled grasp the grip-rings and force the rotation of the main wheels, thereby propelling the wheelchair.   Differential application of force is applied to change the lateral direction of the wheelchair.   To grasp the grip-ring requires that the forearm be twisted and that the force be applied to the grip by a small portion of the palm between the thumb and the fingers.   These requirements can be fatiguing, specifically over extended distances inasmuch as appreciable force must be applied to a small gripping area.   It is particularly fatiguing when arresting the motion of the wheelchair or when ascending or descending a slope.

When sitting in a normal upright position with hands resting on one's lap, the most comfortable position of the hands is knuckles upwards with the angular rotation of the forearm positioning the hands between flat on the lap at 0° to twisted outwards at 45°, with a 30° twist probably closest to the most comfortable for most people.   Hence when gripping two oars during rowing the hands are in close to the most comfortable position for exerting maximum bodily force on the oars with the load applied across the full width of the palms.   In contrast, to propel a wheelchair the forearms are twisted roughly 90° outwards with the load is applied across only a small portion of the palms. This motion is not only fatiguing but what little grip is available is lost when the grip-ring is wet, often necessitating special gripping gloves.  

Worse such repetitive motion exerted by the occupant on the grip-ring to prevent slippage can cause considerable local stress, contributing to repetitive strain injuries. The occupant must simultaneously grip the two rings while rotating the wrists and simultaneously exert a torque on the drive wheels.   It is this required double motion at an awkward angle that greatly contributes to instances of rotator cuff tears and median nerve damage that can lead to carpal tunnel syndrome, which affects roughly one-half of the manual wheelchair users. It is a particularly severe problem among disabled war veterans. To cite a few studies:

  • Effect of Wheelchair Handrim on Carpal Tunnel Syndrome; K. Dieruf, L. Ewer, D. Boninger, M. Dixon; U. New Mexico, USA
  • Wrist motion in handrim wheelchair propulsion; D. Veeger, L. Meershoek; L. van der Woude, J. Langenhoff; Vrije Universiteit Amsterdam, The Netherlands
  • Wrist kinematic characterization of wheelchair propulsion in various seating positions: implication to wrist pain; S. Wei, S. Huang, C. Jiang, J. Chiu; National Yang Ming University, Taiwan
  • Wheelchair pushrim kinetics: body weight and median nerve function; M. Boninger, R. Cooper, M. Baldwin, S. Shimada, A. Koontz; Department of Rehabilitation Science and Technology, University of Pittsburgh, USA.

    In response to this uncomfortable application of force to propel wheelchairs this proprietary Wheelchair Drive-Assistance (WCDA) device has been developed for use with ordinary wheelchairs and is described herein. The WCDA device does not utilize gears, cranks or ratchets in its operation, which distinguishes it from other drive devices. The WCDA device is designed to attain many of the objectives of the power-assisted ordinary wheelchair but without the weight of motors and batteries.   Rather a torque enhancing device alleviates much of the forces required to control and drive ordinary wheelchairs without denying the mobility-disabled of upper-torso exercise.   In this regard the tilted handles of WCDA device eliminates the angle problem and moreover provides nearly a 3:1 grip advantage compared to the bare or gloved hand on the grip-ring. Moreover the WCDA provides integral brakes for control while negotiating downhill slopes.

    A WCDA device is installed without tools on each side of an ordinary wheelchair. When inconvenient they can be readily removed by the occupant without tools. The only modification the WCDA device requires is a change in the wheel retainer bolt which in no way affects the ordinary construction or operation of any applicable wheelchair.

    Installation of WCDA

    The wheelchair occupant actuates the levers on the lateral handles of the WCDA devices, thereby bringing friction pads in contact with the grip-rings. The occupant then pivots the WCDA devices about the main wheel hubs by applying a circumferential force to the handles as shown. Because the tires are not gripped any debris on the tires does not affect the operation of the WCDA device.

    When not required the WCDA devices can be simply snapped off of the wheelchair by the occupant. The WCDA device uses a simple inexpensive linkage mechanism for actuation.

    The WCDA device has many advantages relevant to wheelchair users:

    With well over a million wheelchair users in the United States a substantial majority would be expected to appreciate the convenience of the WCDA device.   Unlike the commercially-available Wijit, the WCDA device does not require twisting the wrist to actuate and has an integral brake for negotiating inclines. Competitive wheelchair users would find the WCDA device advantageous at sports events.


    The operation of the WCDA device is quite simple. Unlike other devices, the WCDA device operates without gears, cranks or ratchets. Depressing the lever moves the friction pads into contact with conventional wheelchair grip rings, clamping the grip rings. Moving the WCDA device fore or aft rotates the grip ring as in normal practice, and thereby the main drive wheels. Releasing the lever allows the retraction springs to release the friction pads. Maneuvering is done in the usual manner for manual wheelchairs. The WCDA handle is angled to conform to natural wrist motion. The WCDA lever is positioned within the handle for the most efficient application of force by the occupant. Moreover, the friction pads act as brakes to effectively slow the wheelchair when required, and hold it in place.

    The following figure illustrates the right and left WCDA devices secured to an ordinary manual wheelchair. The WCDA devices can be readily secured to the wheelchair and as easily removed.


    Schematic of WCDA


    The following figures illustrate the devices secured to an ordinary manual wheelchair at the main wheel hub.

    Detail of Proof-of-Concept WCDA Model


    There are no conveniently-operated removable WCDA devices available today for the mobility disable. That no concerted efforts has been expended to develop a WCDA device is all the more surprising because the number of wheelchairs users in America has increased over the past decade significantly, as is evident below. As seen below, the market potential for the WCDA is growing quite rapidly, with wheelchair usage growing from almost 500,000 units in 1980 to 1,500,000 units in 2005.

    Assuming conservatively that 1/3 of the wheelchair users would not be interested in the WCDA for reasons such as requiring a care-giver for mobility or access concerns, the remaining 1,000,000 users offer a substantial market for the WCDA.


      For Medicare eligibility the device would require a Certificate of Medical Necessity, which is quite specific.

    For example the last requirement would be met by persons who might be susceptible to carpal tunnel syndrome or may be arthritic or with similar ailments.


    Potential customers who have viewed the webpage [] and have contacted us are quite insistent concerning the commercial availability of the WCDA device for mobility-disabled persons. Several are displayed below.

    Is your device available for sale?  If not, would it be possible to licence
    the patent to fabricate one example for an individual?  My friend is a T12
    paraplegic in a wheelchair for the last 15 months.
    Lisa Lefkowitz
    Saw your publication about the drive-Assistance Device for Wheelchair and 
    I was really impressed by the idea. 
    I used to work with handicaps soldiers and I find that this can help some 
    of them to ease their mobility in some cases. 
    The question is have you made this device already? Do you have a Prototype?   
    What is the cost of a unit and what will it take to get one for experiment? 
    I am going to send this info to Israel. 
    As you know, unfortunately, there are many soldiers that suffers consequences
    of the middle east conflict
    so that there will be many candidates for use this kind of device. 
    Amos Nachum
    Are you selling the drive-assstance device for manual wheelchair.
    price? delivery time?
    US representative in USA?
    I am interested in buying one.
    hugo tapia
    Have you created the wheelchair propulsion device? Is such a thing available for purchase?
    Carol Anne

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    For market projection information concerning the


    please contact

    Moishe Garfinkle

    ParaMedical Technologies

    (215) 235-5042

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