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.
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. The invention is fully detailed on my web page.