Abstract:
A lever propelled wheelchair, the lever having two push levers attached to two front drive sprockets. The two levers propel the two main rear wheels of the wheelchairs through chains connecting the front sprockets to gear clusters mounted on the rear axles. Ratchet mechanisms allow each push lever to transmit power to the drive sprockets in either a forward or reverse direction. Derailers are mounted at each axle and are activated by a shifter mechanism mounted on the push levers. Brakes are mounted on the frame beside each wheel and activated by a hand break lever mounted on the push levers.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a user-propelled vehicle or wheelchair. More particularly, it relates to a wheelchair propelled by push levers connected to drive wheels through bicycle chains and variable ratio rear gear clusters. 
     2. Description of the Prior Art 
     Most wheelchair users have little or no functional use of their lower extremities, but have preserved normal upper body function. Accordingly, the conventional wheelchair requires the user to propel the chair by repetitively pushing on push-rims attached to the main wheels of the chair. The arm and shoulder motions that are required are undesirable because they utilize the small, relatively weak, muscles of the rotator cuff and ultimately lead to stress injury and degenerative arthritis of the shoulder joint. This is also an inefficient means of locomotion; providing only a one-to-one ratio of distance traveled for distanced pushed. It is, however, an ubiquitous and relatively simple machine that can be easily maintained. Several attempts have been made to improve on this standard with very limited success. 
     Several inventions employ the use of levers for the user to propel the chair. This is an improvement because it makes use of the larger and more powerful triceps and pectoral muscles, with reduced shoulder stress. Still, however, all of these devices have fallen short of success. 
     For example, U.S. Pat. No. 4,865,344 provides only one speed having one fixed gear ratio, and thereby forgoes the significant mechanical advantage gained by using a set of multiple gear ratios This machine also requires the user to steer with hand levers attached to the push levers, increasing the complexity of steering and propulsion movements. 
     U.S. Pat. No. 5,322,312 is another attempt to propel a wheelchair with a push lever. It also lacks sufficient mechanical advantage, having only one gear ratio. The use of a detachable skateboard device makes this machine unnecessarily complex, expensive, and difficult to maintain. 
     U.S. Pat. 5,209,506 is cumbersome in requiring the user to steer with handlebars which are simultaneously pushed and pulled to propel the chair. The linkage required to operate this machine is also too complex for easy care, and the position of the steering/push lever obstructs easy entry and exit of the chair. 
     U.S. Pat. No. 4,811,964 also uses push levers for power, but in a rowing motion. This machine would be difficult to steer, having a combined row-steer motion; it also has only one speed, and uses a complex system of pulleys and linkage, all of which serve to make it impractical. 
     U.S. Pat. No. 3,994,509 is another lever-driven machine that makes use of a very complex and expensive system of forward and reverse clutches. It also provides only a single forward speed, and has a very wide profile, to accommodate the wide-set wheels. 
     There are several inventions that use a set of bicycle pedals to turn a crank which, in turn, transfers power via a bicycle chain to either front or rear wheels. All of these hand-crank designs suffer from the fact that the hand cranking motion is extremely fatiguing. Further, they are too big and too heavy. The cranking/steering device obstructs entry and exit. These wheelchairs generally lack multiple gears and are difficult to steer while cranking. U.S. Pat. No. 4,720,117 is a typical example of this type of machine. 
     U.S. Pat. No. 5,362,081 is an attempt to adapt the mechanical advantage of multiple gear ratios to the standard wheelchair format. It does not, however, save the user from the repetitive motion injury and degenerative damage to the shoulder joints; and, in requiring the use of the user&#39;s smaller, weaker rotator cuff muscles, it is more fatiguing than a push lever driven machine. This particular model also requires the user to let go of the steering/drive wheel to shift gears. 
     OBJECTIVE OF THE INVENTION 
     It is the object of this invention to provide for, in a wheelchair of simple construction, an alternative means for manually powering the wheelchair which utilizes the strong shoulder and arm muscles of the wheelchair occupant while providing for a selection of gear options to drive the wheelchair in a forward or reverse motion. 
     SUMMARY OF THE INVENTION 
     Applicant provides for a wheelchair propulsion apparatus that improves a user&#39;s ability to propel a chair with less effort and greater speed over a longer duration. Compared to present wheelchair options, mechanics used in Applicant&#39;s wheelchair decrease the stress on shoulder joints and diminish the degenerative joint disease often accompanying prolonged wheelchair use. 
     Applicant&#39;s wheelchair is propelled through use of two push levers, which the user pushes forward utilizing triceps and pectoralis muscles. Ratchets attached to these levers allow the user to retract the levers to the start position with little resistance. 
     Power is transmitted from the push levers to drive sprockets through bicycle chains to the multi-speed rear wheels. Multiple gear ratios are made possible by shifting the drive chain to different size rear wheel sprockets with a derailer mechanism. 
     Turning is accomplished in the same manner that it is done with a standard wheelchair. One wheel is pushed more than the other, or a braking force is applied to one wheel while the other is pushed. Braking is accomplished effectively by using calliper brakes similar to those used on a typical bicycle. 
     This apparatus provides for a most efficient means of wheelchair propulsion, with significant physiological benefits to the user. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a right side view in elevation of the apparatus of this invention. 
     FIG. 2 is a view of left and right derailers showing them to be mirror images of each other. 
     FIG. 3 is a view of left and right shifters showing them to be mirror images of each other. 
     FIG. 4 is a cross section view of the front axle with its attached sprocket, bearing, hub, ratchet, and push lever. 
     FIG. 5 is a cross section view of the ratchet mechanism showing the ratchet cables attached to the ratchet selector in the neutral position. 
     FIG. 6 is a cross section view of the right-side ratchet mechanism showing the ratchet cables attached to the ratchet selector, with the selector set in the forward position. 
     FIG. 7 is a cross section view of the right-side ratchet mechanism showing the ratchet cables attached to the ratchet selector, with the selector set in the reverse position. 
     FIG. 8 is a cross section view of the rear axle with its attached gear cluster, bearings, hub, frame upright, and wheel. 
     FIG. 9 is a view of the left side of the chair viewed from the center of the chair. 
     FIG. 10 is a cross section view of the upper end of the push lever showing the shifter, hand brake lever, brake lever retaining clip, ratchet cables, and the rotating hand grip. 
     FIG. 11 is a cross section view of the outboard side of the rotating hand grip showing the ratchet cables and the spring-loaded ball set in the neutral detent position of the hand grip. 
     FIG. 12 is a cross section view of the outboard side of the rotating hand grip showing the ratchet cables and the spring-loaded ball set in the forward detent position of the hand grip. 
     FIG. 13 is a cross section view of the outboard side of the rotating hand grip showing the ratchet cables and the spring-loaded ball set in the reverse detent position of the hand grip. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to FIGS. 1-9, it is seen that wheelchair ( 1 ) has two large rear wheels ( 2 ) and two smaller front casters ( 3 ). The large rear wheels are typically mounted outboard of the wheelchair frame on rear axles ( 4 ). These rear axles are typically mounted in the left and right rear axle hubs ( 5 ) which are incorporated in the frame of the chair on the left and right rear frame uprights ( 6 ) below the level of the seat. The axles are supported in the hubs on inner ( 7 ) and outer ( 8 ) axle bearings. The rear wheels typically are attached to the axles such that each wheel and axle turns as a unit on the hub bearing. 
     Inboard of the left and right rear axle hubs, sprocket gear clusters ( 9 ) are affixed to their respective axles and turn with the axle-wheel units. The specific number of sprockets and the number of teeth on each sprocket of the gear cluster can be varied within the limitations of space and axle length. 
     With further reference to FIG. 2, derailers ( 10 ) are seen attached to the frame, usually above and behind each gear cluster to shift the left and right drive chains ( 11 ) between rear sprockets ( 12 ) of each sprocket gear cluster ( 9 ). 
     Each drive chain ( 11 ) is a multi-link, standard bicycle chain that rotates its gear cluster (and axle and wheel) when the corresponding front drive sprocket ( 13 ) is rotated by the user. 
     With further reference to FIG. 4, it is seen that each front drive sprocket ( 13 ) is affixed to a front axle ( 14 ), which is supported in its front axle hub ( 15 ), on inner ( 16 ) and outer ( 17 ) bearings. The left and right front hubs are typically fixed to the frame of the chair below the seat level on struts ( 17 A). 
     Outboard of the chair frame, a ratchet mechanism  918 ) is attached to each front axle. With further reference to FIGS. 5-7 and  10 - 13 , it is seen that each ratchet can be selected to deliver a power stroke to drive the front drive sprocket in either the clockwise or counterclockwise direction by rotating the handgrip ( 28 ) at the upper end of the push-pull lever which, in turn, pulls up one of the two ratchet cables ( 26 ) that are connected through the inner hollow core of the push-pull lever to the ratchet selector ( 19 ), which moves up, thereby setting the ratchet for forward (FIGS.  6  and  12 ), neutral (FIGS.  5  and  11 ), or reverse (FIGS. 7 and 13) drive. 
     The rotating hand grips are kept in place by a spring-loaded ball assembly ( 30 ) incorporated in the push-pull lever adjacent to the hand grip such that the ball is pressed into one of three detents ( 30 A,  30 B, and  30 C) in the hand grip corresponding to the neutral, or forward, or reverse position of the ratchet selector ( 19 ). The ratchets are attached to the removed ends of each of the two push-pull levers ( 20 ) that the user pushes straight forward to propel the chair forward when the ratchet selectors are set for forward motion. The user can move the chair backwards by setting the ratchets for reverse and pulling back on the push-pull levers. 
     Each derailer moves it drive chain between gear sprockets ( 12 ) when the shift cables ( 21 ) are tightened or relaxed. The user does this by pushing or pulling on the push-pull lever mounted shifter levers ( 22 ). These shifters are typically attached to the handles of each push lever so that the user can operate them with thumb pressure. 
     The derailer and shifter on the left side of the chair are typical of those commonly found on a ten-speed bicycle. The derailer and shifter on the right side of the chair are typically exactly backwards (mirror images) of those on the left side. This allows the user to perform analogous movements with each hand simultaneously to activate each derailer equally and to shift both left and right gears equally. 
     Each rear wheel has its own cable activated calliper brake ( 23 ) The callipers are typically mounted on the frame below the level of the ratches, and activated by a brake cable ( 24 ). The proximal end of each brake cable is attached to a left or right brake lever ( 25 ) which is mounted on the corresponding push-pull lever handle. The user squeezes the brake levers to apply a braking force to the rear wheels. Each wheel brake is operated independently, as is each rear drive wheel. Each push-pull lever is fitted with a pivotable retaining clip ( 29 ) to hold the brake lever in the compressed position, thereby maintaining the callipers tightly compressed to the wheel, thus functioning as a parking brake. 
     Sprocket shields ( 27 ) may be mounted above and in front of each front drive sprocket to protect the user&#39;s legs. 
     The rear axles are typically ½ inch in diameter in order to accept most currently produced wheelchair wheels. These wheels are secured to the drive axles in a manner that prevents them from turning independently from the rear axles. 
     Additional details of the ratchet selector ( 19 ) are seen in FIG. 5, which shows pivoting dog ( 30 ) articulating on pin ( 31 ) to rotate with respect to the body of the ratchet mechanism and thereby engage the teeth of ratchet gear ( 32 ) in the manner set forth in FIGS. 6 and 7. That is, rotation of handle ( 28 ) causes a retraction of one of the two cables ( 26 ) connected at a first end to the rotating handle and the second end to the pivoting dog, thus causing the dog to pivot. 
     Terms such as “left,” “right,” “up,” “down,” “bottom,” “top,” “front,” “back,” “in,” “out,” and like are applicable to the embodiments shown and described in con-junction with the drawings. 
     These terms are merely for purposes of description and do not necessarily apply to the position or manner in which the invention may be constructed for use. 
     Although the invention has been described in connection with the preferred embodiment, it is not intended to limit the invention&#39;s particular form set forth, but on the contrary, it is intended to cover such alternatives, modifications, and equivalences that may be included in the spirit and scope of the invention as defined by the appended claims.