Abstract:
An improved wheelchair and power booster is disclosed. It employs a drive/brake system incorporated in each main wheel connected to lever arms for propelling the wheelchair by engaging the brake and moving the lever arms either forward or rearward to move the associated main wheel forward or backward. Releasing the brakes allows free wheeling. A parking brake lock loop which is located on the lever on the arm locks the brakes. A single front wheel is utilized when pivoted from a leg foot rest. The front wheel may caster freely or may be controlled directly by a manual steering handle. The main wheels are removable for transport and storage and the frame folds to a compact generally rectangular shape for easy carrying along with the wheels in a passenger vehicle. The frame also is designed with a U shaped frame member open at the rear and the seat moves out of place to allow the wheelchair to be backed over a residential or commercial toilet to allow the wheelchair occupant to use such facilities without leaving the wheelchair. A booster assembly including a replacement main wheel with an internal brake and a lever arm rotatably secured to the wheel hub through the brake is provided as a replacement for conventional wheelchair main wheels. The booster assembly includes a brake actuating control and a parking lock located at the hand grip end of the lever arm.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    Through the years, many have attempted to modify wheelchairs by improving the wheelchair&#39;s mobility and by improving user safety. Recently, the advent of new high-strength materials and the increased desire of disabled persons to compete have fostered the development of racing wheelchairs. It still remains true, however, that propulsion typically occurs either as a result of an assistant pushing the wheelchair from behind or the wheelchair user rotating the main wheels by hand using wheel-mounted rings. The alternative to these traditional modes of locomotion seems to be an electric battery-powered wheelchair or vehicle.  
           [0002]    Examples of alternate forms of wheelchair propulsion may be found in the following United States patents:  
                                                           5,577,748   Dombrowski et al.   November 26, 1996           5,509,673   Wu et al.   April 23, 1996           5,322,312   M. A. Cammack   June 21, 1994           5,263,729   Watwood et al.   November 23, 1993           5,241,876   T. Mathis   September 7, 1993           5,232,236   E. Korpi   August 3, 1993           5,020,815   Harris et al.   June 4, 1991           5,007,655   M. Hanna   April 16, 1991           4,811,964   S. J. Horn   March 14, 1989           4,762,332   Main T. Seol   August 9, 1988           4,682,784   J. E. Anderson   July 28, 1987                      
 
           [0003]    These patents illustrate the recognized need for improved wheelchair propulsion systems.  
           [0004]    It is also recognized that there is a need for such wheelchairs to be compact and foldable so that the wheelchair can easily accompany the user in, for example, an automobile. In the past this has normally been accomplished by folding the two sides of the wheelchair with their wheels attached inward, with the seat and back areas collapsing so as to bring the overall width of the folded wheelchair to about twelve inches. The folded wheelchair can then be placed behind the front seat area or the trunk of a vehicle. This type of folding wheelchair may be satisfactory when the wheelchair occupant has an attendant to assist in the folding and placement of the wheelchair in the vehicle. This type of folding design, however, would be difficult for almost all wheelchair users whose impairment precludes them from folding the wheelchair and/or placing it behind the seat or into the trunk. I recognized that wheelchair users often times have a high degree of mobility in their arms and with that factor in mind I developed a wheelchair which is easily foldable by most wheelchair occupants.  
         BRIEF DESCRIPTION OF THE INVENTION  
         [0005]    Faced with the foregoing state-of-the-art, I realized that a significant advance in the state-of-the-art could be accomplished in occupant-propelled wheelchairs where the occupant employs his/her upper body strength in a more efficient manner than merely driving the wheels directly by moving the wheel rings or by the various other types of drive systems. It appears to me that the occupant would be more comfortable and have more efficient driving and braking of the wheelchair if a simple lever drive system were utilized.  
           [0006]    It also appears to me that the incorporation of a brake into each wheel with a lever arm and a brake engagement handle for each wheel should be used. The lever arm, which I term the “mobility booster”, has a length greater than the main wheel&#39;s radius and consequently will have a greater momentum arm for driving its associated wheel. Additionally, the lever is operated from the occupant&#39;s lower chest region and involves a more natural movement of simply extending the user&#39;s arms forward from a position above the user&#39;s waist and then returning the arms beside the chest, generally in the armpit region.  
           [0007]    I also determined that an efficient brake built into each wheel can act not only to stop the wheel but also act as the drive member for moving the wheelchair main wheels either forward or rearward. Each lever arm includes a finger-operated brake handle. When the brake handle is depressed, the brake engages for either forward or rearward movement or holds the wheel immobile. When the brake handle is released, the wheel is free to turn or free wheel.  
           [0008]    The action of propelling the wheelchair in accordance with this invention is somewhat similar to the act of rowing a boat in which the oar handles are moved forward out of the water in a feathered position, then twisted and dropped into the water to engage the water as the rower pulls the oars back to drive the rowboat forward (toward the rower&#39;s back).  
           [0009]    In the case of my invention, for forward propulsion, the occupant of the wheelchair with his hands on the lever which is near his chest, depresses the brake handles of both main wheels to engage the brakes to their respective wheel and straightens his arms forward and then releases the brake handles. The wheels are driven forward and then released for free rolling. The occupant then withdraws his arms towards his chest returning the levers to their near-vertical position with the brake handles released. At the rearmost position that is comfortable for the occupant, he depresses the brake handles to engage the wheel again and straightens his arms forward to drive the main wheels forward again, then releasing the brake handles and allowing the main wheels and the wheelchair to free roll or coast. Thus, the same natural movements, as in rowing, are used. The levers or power boosters, being longer than the diameter of the main wheels, give not only a mechanical advantage to the forces applied by the wheelchair occupant as compared to operating the conventional hand ring of typical wheelchairs, but allows more precise control in starting, stopping and turning.  
           [0010]    In order to reverse the wheelchair, the occupant grasps the levers, and with the brake handles released, straightens his arms forward, then depresses the brake handles and draws his arms back towards his chest and releases the brake lever to allow the wheelchair to coast to the rear. Repeating this cycle propels the wheelchair backwards.  
           [0011]    Another aspect of this invention provides for improved steering. The presence of a single front wheel and a short tiller bar and handle facilitates steering with one or both hands. Allowing the operator to steer with one hand frees the wheelchair operator to drive the wheelchair with the other hand by manipulating a single mobility booster. The ability to steer the inventive wheelchair with only one hand is also beneficial to those occupants whose strength is primarily located in one arm.  
           [0012]    Another feature of this invention is that the camber angle of the wheels may be easily adjusted to provide, among other things, greater stability, similar to that usually found only in racing wheelchairs. This ability to change the camber angle can also be used to adjust the positions of the power boosters for user comfort.  
           [0013]    This invention also affords a degree of unassisted lifestyle heretofore unavailable to most wheelchair occupants. The inventive wheelchair also has a greater degree of clearance side to side and floor to the underside of the seat when viewed from the rear as compared to other wheelchairs. The wheelchair also has an open back, and with the other previously described features, allows the user to back the wheelchair over a conventional toilet. Further, the wheelchair provides for the seat to move such that the occupant may utilize a conventional toilet without actually leaving the wheelchair.  
           [0014]    After removing the main wheels, the wheelchair of my invention is foldable into a compact package with the dimensions of approximately 16-inches wide by 19 inches in depth by 8 inches in height. Thus, the inventive wheelchair is easily stored or transported in, for example, an automobile. The main wheels are easily removed, and in the occasion of an automobile, may be stored behind the front seat for simple reassembly and use at the end of a trip.  
           [0015]    One other feature of the invention is that the wheel and lever assembly are not only removable for storage and ease of transport, but also have separate utility as replacement wheels for the main wheels of a conventional wheelchair. This affords the advantages of retrofitting convention wheelchairs with the mobility booster of this invention without incurring the expense of purchasing a new wheelchair.  
           [0016]    Conventional wheelchairs are generally capable of accepting the inventive wheel with center hub and brake. After conversion, a conventional wheelchair is able to utilize the leverage principle of my booster arm, controlled by a leveraged handgrip and utilizes the brake shoes within the hub of the main wheels for both driving and braking the wheelchair. The brake shoes are engaged through a metal control cable or rod, which extends from the center wheel housing parallel to the booster lever arm. Releasing the booster arm permits a freewheeling of the wheel. By reversing the process, backward mobility is accomplished.  
           [0017]    The occupant operating my improved wheelchair or a modified conventional wheelchair having my mobility booster lever arm wheels and brake assembly is able to propel the wheelchair forward and backward as fast as safety will allow and with much less effort than is required to mobilize a conventional wheelchair having a traditional “hand rim” wheel. Because movement requires far less dexterity when my mobility booster wheel assembly is used, steep inclines, handicap ramps, and curb ramps are negotiated with much greater ease. Smooth, safe, downhill movement and stopping are also facilitated. The use of the mobility booster wheel assembly encourages self-reliance, offers newfound freedom, helps to overcome physical limitations and provides faster, low-effort mobility.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0018]    This invention may be more clearly understood from the following detailed description and by reference to the drawing in which:  
         [0019]    [0019]FIG. 1 is an exploded view of the first embodiment of this invention with the actual padded seat and backrest portions removed to aid in the understanding of the invention and its operation;  
         [0020]    [0020]FIG. 2 is a side elevational view, partly broken away, showing the invention and its mode of propulsion;  
         [0021]    [0021]FIG. 2A is a fragmentary side elevational view of the mobility booster arm handgrip area showing its preferred parking brake lock;  
         [0022]    [0022]FIG. 2B is a fragmentary front elevational view of the handgrip area and parking brake lock of FIG. 2A;  
         [0023]    [0023]FIG. 3 is a fragmentary side elevational view of the frame of this invention showing an arrangement for folding the frame;  
         [0024]    [0024]FIG. 4 is a fragmentary sectional view taken along lines  4 - 4  of FIG. 2 showing the propulsion and drive braking assembly of this invention;  
         [0025]    [0025]FIG. 5 is a fragmentary enlarged side elevational view of the drive braking and propulsion system of FIGS. 2 and 4 with portions broken away to facilitate the understanding of this portion of the invention;  
         [0026]    [0026]FIG. 6 is a vertical sectional view taken along lines  6 - 6  of FIG. 1 showing the camber adjustment of the wheels of this invention;  
         [0027]    [0027]FIG. 7 is a fragmentary vertical sectional view, similar to FIG. 6, with the wheel shown in the maximum camber adjusted position;  
         [0028]    [0028]FIG. 8 is a perspective view of a third wheel and steering arrangement of this invention with an alternate form of swiveling caster third wheel, which may be used in place of the wheel shown already attached to the steering assembly;  
         [0029]    [0029]FIG. 9 is a side elevational view of the frame, seat, and backrest, as well as footrest combination of the process of being folded for transport with the main wheels removed;  
         [0030]    [0030]FIG. 10 is a side elevational view, similar to FIG. 9, with the frame assembly fully folded;  
         [0031]    [0031]FIG. 11 is a side elevational view of an occupant in the wheelchair of this invention in the process of traveling down an inclined surface;  
         [0032]    [0032]FIG. 12 is a side elevational view of the wheelchair of this invention positioned over a normal household commode with the seat cushion of the wheelchair seat folded and retracted to allow virtually unassisted use of the conventional commode by a wheelchair confined patient;  
         [0033]    [0033]FIG. 13 is a front elevational view of the wheelchair in the position shown in FIG. 12;  
         [0034]    [0034]FIG. 14 is a top plan view of this invention shown with the occupant steering and propelling the wheelchair using a single hand;  
         [0035]    [0035]FIG. 15 is a top plan view, similar to FIG. 14, with the occupant steering in the opposite direction from FIG. 14 while using a single hand;  
         [0036]    [0036]FIG. 16 is a side elevational view of an alternate form of folding frame of this invention with the user and main wheel shown in dashed lines;  
         [0037]    [0037]FIG. 17 is a front elevational view of the alternate form of the frame of FIG. 16 with the user and main wheels shown in dashed lines;  
         [0038]    [0038]FIG. 18 is a top plan view of the frame of FIG. 16 in its open or unfolded condition;  
         [0039]    [0039]FIG. 19 is a side elevational view of the alternate form of the frame of FIG. 16 folded;  
         [0040]    [0040]FIG. 20 is a top plan view of the frame of FIG. 16 folded with the folded backrest partially broken away;  
         [0041]    [0041]FIG. 21 is a side elevational view of a conventional wheelchair and ready for substitution of mobility booster wheels of this invention;  
         [0042]    [0042]FIG. 22 is a side elevational view of a mobility booster wheel of this invention ready to be substituted for the standard wheels of the wheelchair of FIG. 21 for lever-operated drive and steering;  
         [0043]    [0043]FIG. 23 is a side elevational view of the wheelchair of FIG. 21 with the mobility booster wheels of FIG. 22 replacing the conventional main wheels of the wheelchair of FIG. 21;  
         [0044]    [0044]FIG. 24 is a side elevational view of the removed conventional wheel of FIG. 21; and  
         [0045]    [0045]FIG. 25 is a side elevational view of a passenger vehicle, partly broken away, showing a wheelchair user in the front right-hand seat with the wheelchair frame folded below his feet and the main wheels stored behind the front seats of the vehicle.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0046]    General Assembly  
         [0047]    The basic parts of a wheelchair of this invention, generally designated  10 , may be seen in exploded view of FIG. 1. The seating and backrest have been removed in order to show the details of the frame assembly  11 , the mobility booster wheel assemblies  12  and  13 , and the steering controlled front wheel  14 . The frame assembly  11  includes a base section  15  with an upper U-shaped seat support  16 , and main wheel support brackets  20  and  21  on the wheelchair user&#39;s left and right side, respectively. A footrest  24 , which also acts as the front wheel-mounting bracket, is pivotally secured to the main wheel support brackets  20  and  21 . A footrest stop bar  23 , with locking mechanism  25 , secure the footrest  24  when in use and release it for folding of the frame assembly  11 .  
         [0048]    The single front wheel  14  is mounted on a vertical shaft  26  and journaled in bracket  30  for steering by small steering arm  31  at the top of shaft  26 . The shaft  26  and steering arm  31  are removable at any time when front wheel hand steering is not desired or for entrance or exiting the wheelchair  10 . The steering arm arrangement of FIG. 1 is a feature which allows precise steering movement since the wheel  14  is journaled directly under the shaft  26 . With this arrangement, for every 1 degree of rotation of the steering arm  31 , there is 1 degree of pivoting of the axle of the front wheel  14 . Small wheel steering does not require any forward or rearward movement of the wheelchair as in the case of trailing free steering front wheels that are common in wheelchairs.  
         [0049]    The front ends of the U-shaped seat support  16  are supported by downward extending brackets  22 , which are latched to footrest stop bar  23  by locking mechanisms  25  to add rigidity to the front of the frame assembly  11 . A pair of stops  34  and  35  are located at each side of the frame  11  which serve as front stops and rests for the manually operated mobility booster lever arms  36  and  37 , and which are attached, respectively, to the wheel assemblies  12  and  13  and are described in more detail below. Each mobility booster lever arm  36  and  37  has a handgrip and a nearby parking brake operating handles  40  and  41 , respectively.  
         [0050]    The wheel assemblies  12  and  13 , in addition to having rims  12 R and  13 R and tires  12 T and  13 T, each have a hub  12 H and  13 H, a shaft  12 S and  13 S, and an internal brake  12 B and  13 B, better seen in FIGS. 2, 4, and  5 . The brake  12 B and  13 B are each operated individually by the wheelchair occupant squeezing the brake-operating handles  40  and  41  and moving them toward their respective mobility booster lever arm  36  or  37  in a conventional handgrip brake operation, which is familiar and natural for most people. The mobility booster lever arms  36  and  37  are directly connected to the hub of their respective wheels.  
         [0051]    The brakes  12 B and  13 B are contained within the hubs  12 H and  13 H are of the drum and shoe type. These drum and shoe-type brakes provide excellent braking which is important not only for stopping and parking the wheelchair but is used also as the driving connection between the mobility booster lever arms  36  and  37  and wheels  13 W and  12 W, respectively. These brakes do not add significantly to the width of the wheelchair, as they are located within each respective main wheel.  
         [0052]    The base sections  15  of the frame  11  also includes a pair of wheel support plates  38  and  39  for the assembly of the wheels  12 W and  13 W to the frame  11 . These plates  38  and  39  may be permanently secured to the frame  11  or as described below adjustable in camber angle as illustrated and described in connection with FIGS. 6 and 7.  
         [0053]    Now referring specifically to FIG. 2 in connection with FIGS. 2A, 2B, and  3 - 5 , the wheelchair  10  may be seen in FIG. 2 in its fully assembled condition with the seat  10 S and backrest  10 B in place as well as the wheel assemblies  12  and  13 , only wheel assembly  13  being visible in FIG. 2. The mobility booster lever arm  36  is shown secured directly to the brake housing closing plate  42  and a brake operating rod or cable  43  is connected at its upper end to the brake-operating handle  40  and its lower end to a brake lever arm  44 .  
         [0054]    To engage the brake, one must squeeze the brake-operating handle  40  and/or  41  toward the mobility booster lever arm  36  or  37 , which in turn moves the brake lever arm  44  or its counterpart on wheel  12 W, counterclockwise in the drawing FIGS. 2 and 4, expanding an internal brake shoe  45  of FIG. 4 into contact with the main brake housing  46 . This holds the mobility booster lever arm  36  in direct engagement with the wheel assembly  13  for rotation as long as the brake-operating handle  40  and/or  41  is held in this manner. When the mobility booster lever arm  36  is moved forward from the position shown in FIG. 2 to the dashed position of FIG. 2, approximately 15 degrees, the wheel assembly  13  rotates counterclockwise (forward) for the same amount, e.g., 15 degrees. If the brake-operating handle  40  is then released, the wheel  13 W of the wheel assembly  13  is free to continue rolling, i.e., free wheeling until the brake-operating handle  40  or  41  is again operated to stop its associated wheel  12 W or  13 W from further rotation separate from the brake-operating handle  40  or  41 .  
         [0055]    While the wheel assemblies  12  and  13  are in free wheeling condition and the wheelchair is moving ahead, the mobility booster lever arms  36  and  37  may be freely drawn back to prepare for a second stroke, when the brake handles  40  and  41  are again engaged and a second drive boost is applied to wheels  12 W and  13 W. Such action is similar to the movement of the oarsman in a boat, only the direction of drive is direct rather than reverse as in the case of the oarsman. The wheelchair user may hold, for example, one wheel  13 W locked by squeezing and maintaining brake-operating handle  40  and holding the mobility booster lever arm  36  immobile while pumping the other mobility booster lever arm  37  with its brake engaged such that it allows the user in this example to pivot the wheelchair to the left about locked wheel  13 W. The front wheel  14  will turn 90 degrees and track the rotation of the wheelchair  10 .  
         [0056]    To hold the wheelchair in a fully braked condition at any time or any place without the need to continually hold the brake handle  40  or  41 , the wheelchair user may engage the brake locking ring  47  or  48  shown in FIGS. 2A and 2B into the locked position as shown in FIG. 2B as compared to the normally released position of FIG. 2A.  
         [0057]    The details of the footrest stop bar  23  for the footrest  24  and locking mechanisms  25  may be seen in FIG. 3, while the detail of the brake system, which is integral to the wheels, appears in FIGS. 4 and 5.  
         [0058]    Camber Adjustment  
         [0059]    Referring now to FIGS. 6 and 7 for a view of the camber-adjustment feature of this invention. As indicated above, most conventional wheelchairs have fixed zero degrees of camber. Wheelchair racers have long recognized that adding camber to the main wheels adds stability to the wheelchair and thus reduces the likelihood of overturning the wheelchair. Adding camber also allows the racer to utilize a more comfortable, slightly outward arm position for gripping the mobility booster lever arms  36  and  37  for greater speed and endurance.  
         [0060]    The wheel support plate  38  is angularly adjustable from the vertical in its connection to the base section  15  and the U-shaped seat support  16  of the frame assembly  11 . The camber adjustment employs a plurality of openings in the upper end  38 V of the wheel support plate  38  and a retractable pin  50 , which can fit into any of a series of adjustment holes  51 , two of which appear in FIG. 6. The main attachment of the wheel support plate  38  to the frame assembly  11  is at the base section  15 . There, a clamp assembly  52  encircles the tubular base section  15 , and with its locking bolts  52 B holds the camber angle selected.  
         [0061]    In FIGS. 6 and 7, only two camber angles CA are shown, 0 degrees in FIG. 6 and in FIG. 7 an outward or positive camber is illustrated with the pin  50  located in the adjustment holes  51  and an approximate 7 degrees of camber. Said camber angles CA are limited in large part only by the number of adjustment holes  51  and their location for camber adjustment. Suffice it to say that camber adjustment of the wheel assemblies  12  and  13  by any adjustment means provides angular adjustment of the mobility booster lever arms  36  and  37  for the convenience and possibly improved endurance of the wheelchair user.  
         [0062]    Third Wheel Steering Refinement  
         [0063]    One form of the front wheel  14  and steering assembly is illustrated in FIG. 8 in which the wheel  14  is located directly below on the axis of rotation A of shaft  26  and coupled thereto by an interlocking pin  26 P and slot  14 ST combination. The wheel  14  is journaled on its L-shaped support bracket  14 B, which in turn is mounted by bearing assembly  14 BA and secured to the footrest tube  24  by clamp assembly  14 CA. An alternate form of wheel caster, known as a trailing-type caster wheel  14 WC also appears in FIG. 8. However, the preferred form of wheel  14  is as shown in place in FIG. 8 in which the axis of rotation A of the shaft  14 S passes through the axis of rotation  14 AR of the wheel  14  providing ease of operation as described above.  
         [0064]    Frame Folding Features  
         [0065]    One additional feature of this invention is illustrated in FIGS. 9 and 10, as well as FIGS.  18 - 20 . As is well recognized, the folding of a wheelchair for carriage in an automobile is a necessity for many wheelchair users. Typically, after the user exits the wheelchair, folding is accomplished by collapsing the sides together with the wheels attached. For many wheelchair users, that form of folding is acceptable and usually requires that the wheelchair be carried upright behind a front seat of an automobile or in the automobile trunk. For most wheelchair users, removal requires the assistance of another person who will open the back door or trunk, remove the wheelchair, and spread the wheelchair out into position. Although many wheelchairs are light in weight, many are too cumbersome for the user to remove and open while sitting in the front seat of an automobile without assistance.  
         [0066]    My wheelchair is folded, stored and carried in an automobile in a different manner from the prior art. The frame is foldable after removal of both wheel assemblies  12  and  13  including mobility booster lever arms  36  and  37  as two separate units. In the embodiments of FIGS. 9 and 10, and FIGS.  18 - 20 , the backrest  10 B folds forward against the seat  10 S and the U-shaped seat support  16 . After release of the footrest stop bar  23 , the footrest  24  and front wheel  14  may be folded upward parallel the U-shaped seat support  16  bringing the frame assembly  11  into a generally rectangular package, which may rest in the front seat foot well below the legs of the front right seat occupant who, in all probability, is the wheelchair user. The back of the backrest may act as a foot support for the front right seat occupant and provide comfort while riding in the automobile.  
         [0067]    The wheel support plates  38  and  39  allow the folded frame to sit at a comfortable angle for the front right seat occupant. The wheels may each be placed behind the front seat by the user while sitting in the front right seat of the automobile simply by pulling the wheels into the automobile and placing them behind the seat. The stored position of the alternate frame embodiment is shown in FIG. 25. However, the same storage is found with the frame embodiment of FIGS.  1 - 3  and  8 - 10  as illustrated in FIG. 25 with a user shown as a passenger in an automobile.  
         [0068]    By dividing the wheelchair into three manageable parts, the user is capable of handling the placement of the wheelchair in a vehicle by himself. If the wheelchair user is also the driver and does not have a helper, this feature is of significant benefit. It is recognized that the wheels must be removed and reassembled with the frame; however, quick-action fasteners, for removing and replacing bicycle wheels on their front forks, are well known and may be used in place of the conventional nuts illustrated in FIGS. 2, 4 and  5 .  
         [0069]    Normal Uses  
         [0070]    The use of the wheelchair of this invention in traveling down an incline is illustrated in FIG. 11. The user grasps both mobility booster lever arms  36  and  37 , only one of which appears in FIG. 11, while concurrently squeezing the brake handles (not shown) sufficiently to control the speed of descent. In order to stop on an incline or on level ground without having to continuously squeeze the brake handles, the wheelchair user has only to engage the brake locking rings  47  or  48 , best seen in FIGS. 2A and 2B. Engagement of both brake locking rings  47  and  48  is recommended whenever the user desires no movement.  
         [0071]    In those instances where the wheelchair user has limited strength or mobility in one arm but better capability in the other arm and still wants to be fully mobile, the wheelchair user may operate the removable steering arm  31  with one hand, which requires very little force to operate and propel the wheelchair  10  using only one wheel assembly  12  or  13 .  
         [0072]    The frame assembly  11 , illustrated in FIGS. 2, 3,  9 , and  10 , provides another feature which is illustrated in FIGS. 12 and 13. The frame assembly  11  has no cross bar at the rear, and the seat  10 S is foldable against the backrest  10 B. This leaves the seat area open. The U-shaped seat support member  16  is located at a height of at least 16 inches from the floor, which means that the wheelchair of this invention may be backed over most residential and commercial toilets such that the user may sit on the regular toilet seat after having raised the wheelchair seat  10 S out of the way. After using the toilet, the wheelchair user slips the wheelchair seat back in place and propels himself forward using the mobility booster lever arms  36  and  37 , as described above and away from the toilet without assistance. This feature is intended to provide the user with additional degrees of freedom.  
         [0073]    The freedom to self propel this wheelchair and make abrupt changes of direction is illustrated in FIGS. 14 and 15. By engaging one brake in one wheel and concurrently operating the other wheel via the mobility booster arm, the wheelchair will pivot about the locked wheel, as for example to the left in FIG. 15. By holding the brake of wheel  13 W locked and concurrently operating the other wheel, the wheelchair will pivot about the locked wheel and turn to the right as shown in FIG. 14. It is also possible to operate both main wheels  12 W and  13 W in opposite directions by opposite driving of the mobility booster lever arms and turn the wheelchair without any movement either forward or backward, e.g., “turning on a dime”. This adds a significant degree of mobility heretofore not available to most wheelchair users.  
         [0074]    Alternate Frame Design  
         [0075]    FIGS.  16 - 20  illustrate an alternate and preferred form of frame  110  having an upper seat frame  111  and a lower seat frame  112 , and a U-shaped leg rest frame  113 . The upper frame member  111  pivotally supports the backrest  114  from its upper position resting against pads  115  on the upturned end  116  of the lower seat frame  112 . The upturned end  116  may receive optional handles shown in dashed lines for use by assistants, if desired.  
         [0076]    The leg rest frame  113  includes a bottom U-shaped footrest  113 F and a pair of cross braces  120  and  121 . Brace  120  supports the single front wheel  122  journaled in bearing assembly  119 . The leg rest frame  113  is pivoted about joint  123  when not in use for rearward folding and storage. The seat  117  is shown in its occupant-supporting position in FIGS. 16 and 17. For perspective, the user and the main wheels  12 W and  13 W are shown in dashed lines, as are the mobility booster lever arms  36  and  37 .  
         [0077]    Storage in a Passenger Vehicle  
         [0078]    FIGS.  18 - 20  show the frame  110  of FIGS. 16 and 17 in folded condition and ready for storage. Note that when folded, the frame, with its seat  117 , backrest  114 , leg rest  113 , and front wheel  122  form a generally rectangular package in the order of 19 inches wide by 20 inches long by 10 inches high, a size which conveniently rests in the foot well of a passenger vehicle. Such placement is illustrated in FIG. 25.  
         [0079]    In FIG. 25, a typical small sedan is shown, partly in section, with a passenger seated in the front right hand seat. His legs on the folded frame  110  and the two main wheel assemblies  12  and  13  are within easy reach of the passenger for placement and removal. Upon entering the vehicle with the side door open, the wheelchair user slips into the vehicle seat, removes the near main wheel assembly  12  and stores it behind the front seat. He next folds the frame  110  to its packed form and removes the main wheel assembly  13  and also stores it behind the front seat. The frame may be lifted into the vehicle and placed under the passenger&#39;s leg acting as a leg rest during the vehicle travel. It is believed that this can all be performed by most wheelchair users without the need for assistance. Additionally, the mobility booster lever arms  36  and  37  act as handles for wheel assemblies  12  and  13  as does the upturned end  116  of the frame, all of which makes vehicle storage easier to complete.  
         [0080]    Reassembly of the wheelchair is basically a reversal of these steps.  
         [0081]    The Mobility Booster Lever Arms Applied to Existing Wheelchairs  
         [0082]    While experimenting with this invention, it appeared to me that certain of the features of this invention can be easily adapted to conventional wheelchairs to add to their capability. In particular, the main wheel assemblies, including the mobility booster lever arms and brake system, may be substituted for a conventional pair of wheels and all of the features of the mobility boosters described above become available to the user of an otherwise conventional wheelchair. This is illustrated in FIGS.  21 - 24 .  
         [0083]    [0083]FIG. 21 shows a conventional folding wheelchair  200  with its frame  201 , main wheels  202 , small front wheels  203 , and footrest  204 . The main wheels include hand rims  205 , which are used by the wheelchair user to self propel the wheelchair  200 . An assistant uses handles  206  to push the wheelchair  200  and its occupant conventionally.  
         [0084]    The conventional main wheels  202 , FIG. 24, are removable and a pair of mobility booster wheel assemblies  210  of FIG. 22 may be substituted for the conventional main wheels  202  to achieve all of the advantages of these mobility boosters described above, FIG. 23. Thus, there is no need to replace the present wheelchair. The mobility booster wheel assemblies  210  includes a spoke wheel, as illustrated in FIG. 22, but alternatively may include a rigid spoke configuration or any other similar type configuration. The replacement mobility wheel assembly  210  includes the lever arm  236  with its brake handle  240 , rod or cable  243 , and brake arm  244  connected to the internal brake hub and brake lock  248 .  
         [0085]    After conversion, the wheelchair  200  has the appearance as shown in FIG. 23. In addition to the mobility booster wheel assembly  210  of FIG. 22, the only other addition required for the wheelchair  200  is a stop  250 , which is merely an add-on plate or rod extending outward on each side of the wheelchair frame  201  to limit the forward rotation of the levers  236  on each side of the wheelchair  200 .  
         [0086]    The above-described embodiments of the present invention are merely descriptive of its principles and are not to be considered limiting. The scope of the present invention instead shall be determined from the scope of the following claims, including their equivalents.