Patent Publication Number: US-8540266-B2

Title: Wheelchair

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation in part application of U.S. patent application Ser. No. 12/315,548, which claims the benefit of U.S. Provisional Patent Applications Nos. 61/005,439, 61/005,446 and 61/005,447, all filed on Dec. 5, 2007, and all incorporated by reference herein in their entirety. 
    
    
     FIELD AND BACKGROUND OF THE INVENTION 
     This invention relates to a wheelchair. More particularly, the invention relates to a wheelchair having a specific form of locomotion. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the invention, there is provided a wheelchair comprising: a main frame; a seat mounted on the main frame; a pair of front wheels and a pair of rear wheels; and a propulsion mechanism for driving the rear wheels, the propulsion mechanism comprising an arm lever for forward and back movement and a gear train between the arm lever and the rear wheels. 
     Preferably, the gear train comprises an arm gear which turns in response to forward and back movement of the arm lever; a directional gear driven by the arm gear, the directional gear being movable between a first forward position for moving the rear wheels forward and a second reverse position for moving the rear wheels in reverse; a forward drive gear driven by the directional gear when the directional gear is in the first position; and a reverse drive gear driven by the directional gear when the directional gear is in the second position. 
     In one form, a gear shift mechanism is provided for moving the directional gear between the first position and the second position. Further, there may be a neutral position for the directional gear in which it drives neither the forward drive gear or the reverse drive gear. In one aspect, the directional gear is mounted on an outer shaft, the outer shaft being mounted on an inner shaft which is axially movable within the outer shaft, and the directional gear is connected to the inner shaft though a slot in the outer shaft and is moved between the first and second positions by the movement of the inner shaft within the outer shaft. 
     Preferably, a linkage assembly is operatively connected to the directional gear, and a cable system controlled by a user of the wheelchair. The linkage assembly may comprise a linkage case and a link arm lever therein which is pivotable between a forward motion position and a reverse motion position, one end of the link arm lever being connected to the cable system for movement between the forward and reverse motion position, the other end of the link arm lever being connected to the inner shaft to move the inner shaft between the first forward and second reverse positions. 
     Preferably, the arm lever comprises an elongate arm connected at one end to the gear train and extending upwardly therefrom laterally of the seat, the arm lever driving the gear train by the forward and back movement thereof, and may have an inwardly directed handle for grasping by the user. The handle may have a brake lever thereon for operating a braking mechanism and a gear shift for operating the directional gear between the first forward position and the second reverse position. In one form, the arm lever is foldable along its length for facilitating storage and transportation of the wheelchair, and the handle can be rotated relative to the arm lever. 
     In one aspect, the gear train is at least partially contained in a transmission housing. The gear train housing may comprise four substantially vertical plates held together by a housing frame, the housing having two lateral compartments and a central compartment, each lateral compartment accommodating a left and right side gear train respectively. 
     Preferably, the wheelchair further comprising a seat mount assembly for mounting the seat to the main frame, the seat mount assembly comprising a seat mount member, a pair of seat mounting posts which connect to the main frame and the seat mount member, and a lock plate for enabling releasable securement of the seat mount to the seat mounting posts. Also, the wheelchair may further comprise a gear train mount assembly for mounting the gear train to the main frame, the gear train mount assembly comprising a gear train mount member, a pair of gear train mounting posts which connect to the main frame and the gear train mount member, and a lock plate for enabling releasable securement of the gear train mount to the gear train mounting posts. 
     According to another aspect of the invention, there is provided a wheelchair comprising: a main frame having a frame beam with an upper and a lower surface; a seat mounted on the upper surface of the frame beam; a pair of front wheels and a pair of rear wheels; a propulsion mechanism mounted on the lower surface of the main beam for driving the rear wheels; and a mounting system for mounting the seat and the propulsion mechanism on the main beam of the main frame, the mounting system comprising a seat mount member on an upper surface of the frame beam, a transmission mount on a lower surface of the frame beam, and connecting members on the seat mount and the transmission mount which fasten to each other through apertures in the frame beam. 
     According to a further aspect of the invention, there is provided a method of propelling a wheelchair, the method comprising: forming a seat, a pair of front wheels and a pair of rear wheels on a main frame for a wheelchair; and activating a propulsion mechanism on the wheelchair for driving the rear wheels by moving an arm lever back and forth, the arm lever driving a gear train between the arm lever and the rear wheels. 
     In yet another aspect, the invention comprises a wheelchair comprising: a frame and wheels; and a seat assembly mounted on the frame, the seat assembly comprising a seat bottom having a front edge a rear edge and a pair of side edges wherein the rear and side edges are raised, the seat bottom having an at least partial centered rise so as to provide a pair of lateral support recesses for the user for enhanced positioning in the seat bottom. 
     Preferably, the wheelchair further comprises a seat back, the seat back having lateral supports and lumbar support to correctly position the user in the seat assembly. The seat bottom is preferably higher at the front edge thereof than at the rear edge. 
     According to one aspect of the invention, there is provided a wheelchair having an arm lever, preferably two arm levers, for initiating locomotion of the wheelchair. The locomotion, in accordance with the invention, is initiated by the backward and forward movement of arm levers by the user of the wheelchair, the arm levers being connected to the wheels of the wheelchair through a drive train so that the motion of the levers is transferred into a force for rotating the wheels. The drive train may take several different forms, but in one preferred aspect of the invention comprises an arm gear, a directional gear, and forward and reverse gears. The arm lever drives the arm gear, which in turn drives the directional gear. The position of the directional gear may be varied so as to engage either a forward or reverse gear, which in turn transfers motion to the wheel to selectively propel the wheelchair in either the forward or reverse direction. Furthermore, in accordance with the invention, by appropriate selection of the gears in drive trains on different sides of the wheelchair, the wheelchair may be turned, rotated or otherwise directed according to the needs of the user. 
     In one form, brakes are provided for slowing down or stopping the wheelchair. Preferably, the brake comprises a disc brake rotor on a drive axle of the wheelchair, the disc brake rotor being engagable by a caliper which may be activated by the user so as to engage the rotor for the purposes of slowing of stopping the wheelchair. 
     In another aspect, the drive train is contained within a housing comprising plates dividing the housing into various compartments, and support members for holding the plates together, and for use as a support for other drive train components for the wheelchair. 
     In a preferred embodiment, the arm lever may comprise a hand grip which is rotatable, the rotatable hand grip moving cables between first and second positions, so as to move the drive gear to selectively engage either the forward gear or the reverse gear. By appropriate manipulation of the handle, the user therefore has the option of engaging appropriate gear to determine direction of motion. 
     In a preferred embodiment, the arm may be foldable so as to render the wheelchair into a more compact form, so that it may be stored or transported more easily. 
     Preferably, brake levers are provided on the hand grip, and by appropriate cable connection with the brake caliper and rotor, activation of the brake lever by the user will slow down or stop the wheelchair. 
     Preferably, the wheelchair comprises a basic frame member upon which the various components are mounted. The frame may comprise a seat and transmission mount component, and a front wheel component, which may also operate as a foot rest. Preferably, the both the seat and the transmission drive trains are mounted so as to be easily removable for maintenance, repair or cleaning purposes. Preferably, the front wheel has shock absorbers so as to absorb shock from rough surfaces. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings: 
         FIG. 1  is a perspective view of a wheelchair in accordance with the present invention; 
         FIG. 2  is a front view of the wheelchair in accordance with the present invention; 
         FIG. 3  is a frame showing one embodiment of a frame for use in the invention; 
         FIG. 4  is an exploded view showing gears, transmission and brakes for use with a wheelchair in accordance with the invention; 
         FIG. 5  is an exploded view of the various plates and support frame tubes for the transmission of the invention; 
         FIG. 6  is a detailed exploded view showing the mounting of the directional gear for use with the invention; 
         FIG. 7  is an exploded view of the arm gear and associated structures for use with the invention; 
         FIG. 8  is an exploded detailed view showing the forward and reverse gears, braking and other components for use with the present invention; 
         FIG. 9  is a side view of a plate showing a gear shift linkage case; 
         FIG. 10  is a view similar to that shown in  FIG. 9  with the linkage case in exploded view; 
         FIG. 11  is a view showing linkage cases and association thereof with the directional gear; 
         FIG. 12  is a view similar to that in  FIG. 11 , but with the gear in the reverse position; 
         FIG. 13  is an assembled view of the transmission and linkage system, including brake and wheels; 
         FIG. 14  is a side view showing part of the arm lever and the braking system; 
         FIG. 15  is a side view showing the various gears used in accordance with the invention; 
         FIG. 16  is a front view of the transmission system with cover plates thereon; 
         FIG. 17  is a view of the arm when in the extended position; 
         FIG. 18  is a view of the arm when in the folded or partly folded position; 
         FIG. 19  is a rear view of the arm and handle for use with the invention; 
         FIG. 20  is a front view of the arm and handle in accordance with one aspect of the invention; 
         FIG. 21  is a sectional view through a part of the arm and handle showing gear cable connection; 
         FIG. 22  is an exploded view of the component shown in  FIG. 21  of the invention; 
         FIG. 23  is a view of the handle showing locking thereof in the unfolded position; 
         FIG. 24  is a view similar to that in  FIG. 23  with the lock mechanism open; 
         FIG. 25  is a view of the handle when rotated into the folded position; 
         FIG. 26  is an end view of the handle; 
         FIG. 27  is a sectional view through the handle showing the cables in the first drive position; 
         FIG. 28  is a view similar to that in  FIG. 27 , but with the cables moved so as to place the directional gear in the reverse position; 
         FIG. 29  is a view of the hand grip and arm showing the brake lever system in accordance with one aspect of the invention; 
         FIG. 30  is a side view of the hand grip and arm shown in  FIG. 29  of the drawings; 
         FIG. 31  is an exploded view of the frame, seat and transmission, showing the mounting of these components; 
         FIG. 32  is a bottom view of the seat attachment component for securing to the frame; 
         FIG. 33  is a bottom view of a lock plate for securing the seat to the frame; 
         FIG. 34  is a side view of the lock plate, in accordance with one aspect of the invention; 
         FIG. 35  is a front view of the transmission mount in accordance with one aspect of the invention when mounted on support tubes; 
         FIG. 36  is a view of the frame, seat and transmission in the assembled position; 
         FIG. 37  is a side view of the wheel and front suspension; 
         FIG. 38  is a sectional view showing details of the wheel and front suspension; 
         FIG. 39  is a front view showing the wheel, wheel housing and fender; 
         FIG. 40  is a sectional view showing mounting of the wheel, shock absorber and other components to the frame; 
         FIG. 41  is a view of a further embodiment of a main frame of a wheelchair in accordance with the invention; 
         FIG. 42  is a view of a yet further embodiment of a main frame of a wheelchair in accordance with the invention; 
         FIG. 43  is a view of a fender for use on a wheelchair in accordance with the present invention; 
         FIG. 44  is a side view of a wheelchair in accordance with a further embodiment of the invention, the wheelchair shown in the open or usage position; 
         FIG. 45  is a side view of the wheelchair shown in  FIG. 44 , showing the seat folded and locked in storage or transport position; 
         FIG. 46  is a side view of the wheelchair shown in  FIG. 45 , with the seat removed; 
         FIG. 47  is a side view of the wheelchair shown in  FIG. 46  which has been partially folded; 
         FIG. 48  is a side view of the wheelchair shown in  FIG. 47 , fully folded and locked in the storage or transportation position; 
         FIG. 49  is a side view of the wheelchair shown in  FIG. 48 , also showing the seat in the folded position; 
         FIG. 50  is a side view detail of the seat in the open position; 
         FIG. 51  is a back view of the seat showing the locking mechanism, in the locked position; 
         FIG. 52  is a view similar to that in  FIG. 51  but showing the unlocked position; 
         FIG. 53  is a bottom view of the locking mechanism for the frame, shown in the locked position; 
         FIG. 54  is a bottom view as shown in  FIG. 53 , but in the unlocked position; 
         FIG. 55  is a detail of the frame lock mechanism, in the locked in usage position; 
         FIG. 56  is a detail similar to that of  FIG. 55 , but showing the locked in storage position; 
         FIG. 57  is a side view illustrating the seat and its mounting frame; 
         FIG. 58  is a perspective view of the seat mounting frame; 
         FIG. 59  is a bottom view of the seat mounting frame illustrating the lock mechanism; 
         FIGS. 60A ,  60 B and  60 C show details of certain components of the locking mechanism generally illustrated in  FIG. 59 ; and 
         FIG. 61  is a bottom view of the seat, including locking structure components. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to  FIG. 1  of the drawings, there is shown a perspective view of a wheelchair  200  in accordance with the present invention. Generally, the wheelchair  200  comprises a frame  202  in  FIG. 1  (and having reference numeral  74  in  FIG. 31  and other figures related thereto), which supports a seat  204  and a seat back  206 . The seat  204  and seat back  206  are mounted on a central support  208  of the frame  200 . Note that  FIG. 3  shows a single central support. However, in other embodiments, there may be two, or more, supports extending from the front member  210 . 
     The frame further comprises a generally rectangular shaped front member  210 , having an open space  212  and a foot rest  214 . The foot rest  214  comprises the base on the front member  210 , the front member  210  further comprising side arms  216  and  218 . Near the lower end of each of the side arms, there is formed on each side arm  216  and  218  a front wheel support housing  220   a  and  220   b , supporting front wheel assemblies  222   a  and  222   b  respectively. These housings  220   a  and  220   b , the front wheels  222   a  and  222   b  and their attachment structures will be described more fully in due course. Note that the invention is not limited to a frame member  214  which has the rectangular shape as illustrated in the drawings. Other suitable shapes and configurations may be used. 
     The frame  202  also supports the drive mechanism  230 , as will be described in greater detail below. The drive mechanism  230  is generally attached to the lower or bottom side of the central support  208 . The drive mechanism  230  has extending upwardly on either side thereof an arm lever  22 , to be described, and is used by the person sitting in the wheelchair, to move or propel the wheelchair  200 . The drive mechanism  230  drives rear wheels  34 , the rear wheels having a rear tire  34   a.    
     It will be seen that  FIGS. 1 and 2  of the drawings show overall views of the wheelchair  200  of the invention, and  FIG. 3  shows a detail of the frame  202 . In the description below, a detailed description of the general components described above will be provided with particular reference to the drive mechanism  230 , its structure and operation for propelling the wheelchair  200 . 
     Referring again to  FIG. 1  of the drawings, the drive mechanism  230  has a transmission outer cases  12   a  and  12   d  on each side of the drive mechanism  230 , and transmission inner cases  12   b  and  12   c  therebetween.  FIG. 5  of the drawings shows a perspective view of these transmission cases and the tubular supports holding them together most clearly. 
     Gear Train Assembly 
     Continuing the description now with reference to  FIG. 4  of the drawings, there is shown an exploded view which provides a detailed illustration of the workings of one side of the drive transmission  230 , representing the right side (but left side is substantially identical mirror image of right) of the wheelchair when the user is seated therein. Thus, in  FIG. 4 , there is shown the outer transmission case  12   a  and the inner transmission case  12   b . The rear wheel  34  is shown with the rear tire  34   a  mounted on the rear wheel  34 . Furthermore, as has been seen in some of the previous drawings, a part of the arm lever  22  is shown at the point where it connects to the drive mechanism  230 . Generally,  FIG. 4  shows a detailed exploded view of the parts and components in the drive train between the arm lever  22  and the rear wheel  34 , whereby forward and reverse motion of the arm lever  22  drives the rear wheel  34 , either in a forward or reverse direction, as selected by the user. 
     With reference to  FIG. 4 , it will be seen that the transmission inner case  12   b  and the transmission outer case  12   a  define a compartment  240  for many of the drive components between the arm lever  22  and the rear wheel  34 . 
     The main drive components in the compartment  240  comprise an arm gear  8 , a directional gear  13 , a reverse drive gear  14  and a forward drive gear  15 . The directional gear  13  may be selectively operated by the user so as to create a drive train between the arm gear  8  and the forward drive gear  15 , so that operation of the arm lever  22  will drive the wheelchair  200  in a forward direction, and a drive train between the arm gear  8  and the reverse drive gear  14 , such that operation of the arm lever  22  by the user will cause the wheelchair, or at least a particular wheel attached to this drive train, to move in the reverse direction. 
     As will be seen in  FIG. 4 , an arm axle shaft  1  is provided, upon which is mounted both the arm gear  8  inside the compartment  240 , and the arm lever  22  outside of the compartment  240 , adjacent the outer wall of the transmission outer case  12   a . A bearing housing  6  is provided outside the transmission outer case  12   a  and receives the bearing  7 , both of which are mounted to the transmission outer case  12   a  by means of bearing housing mounting bolts  9 . The arm lever  22  is fastened to the arm axle shaft  1  by means of arm lever to arm axle shaft C-clips  19   i  and arm lever to arm axle shaft washers  18   i . Forward and rearward movement of the arm lever  22  causes rotation of the arm axle shaft  1  due to the presence of the arm axle to arm lever lock key  32   a  which locks the arm lever  22  to the arm axle shaft  1 . 
     The arm gear  8  is mounted about the arm axle shaft  1 , and fastened thereto by an arm shaft to arm gear C-clip  19   f , and an arm shaft to arm gear washer  18   f  is provided. Rotation of the arm gear  8  in response to axial rotation of the arm axle shaft  1  is effected due to the presence of the arm axle to arm gear lock keys  32 , as clearly seen in both  FIGS. 4 and 7  of the drawings. The arm axle shaft  1  is secured to the transmission inner case  12 ( c ) by means of a bearing house  6 ′ and bearing  7 ′, attached to the transmission inner case  12   b  by means of mounting bolts  9 ′. 
     With reference to the directional gear  13 , this directional gear  13  is mounted about an outer directional shaft  3 , which is in turn mounted on an inner directional shaft  4 . The one end of the outer directional shaft  4  is received within a sleeve  5  which is fastened to the transmission outer case  12   a . The other end of the inner directional shaft  4  is appropriately attached to the transmission inner case  12   b . The directional gear  13  has a bearing  21  held inside the directional gear  13  by means of retaining c clip  19   e . The bearing  21  is mounted on the sleeve  5  and locked in place by c clip  19   d  and washer  18   d . The sleeve  5  with bearing  21  and gear is mounted over outer directional shaft  3  which is rigidly mounted between the transmission inner case  12   b  and the transmission outer case  12   a . The sleeve  5  is directly bolted to inner shaft  4  via bolts  35  which extend through the outer shaft  3  via slots  3   d.    
     With respect to  FIG. 4  the drive shaft  2  is secured to the wheel using c-clips  19   h  with associated washer  18   h.    
       FIG. 6  of the drawings shows a slightly larger detail of the mountings and components relating to the directional gear  13 , and attention is thus directed to  FIG. 6  of the drawings at this point. 
     The directional gear  13  is moved axially back and forth along the outer directional shaft  3  by the inner directional shaft  4 , the movement being effected by means of a direction shifter operated by the user. This direction shifter will be discussed in further detail below. As will be seen in  FIG. 6 , a hole  4   a  on the inner directional shaft  4  is used to connect the inner directional shaft  4  to the sleeve  5 . The hole  4 B also connects to the sleeve  5 , and connecting bolts  35  pass through the various apertures or slots  3   d  for securing the inner directional shaft  4  to the sleeve  5 . The directional gear bearing  21  is mounted on the sleeve  5  and a C-clip  19   d , and associated washer  18   d , locks the bearing  21  on the sleeve  5 . Furthermore, C-clip  19   e  locks the directional gear  13  to the bearing  21 . 
     The outer directional shaft  3  itself includes the slot  3   d  to connect the inner directional shaft  4  to the directional gear  13 . An inner bore  3   c  is provided in shaft  3  for receiving the inner shaft  4 . Extension legs  3   a  are provided on each side of the outer shaft  3 , so that the shaft  3  can be attached to the inner and outer case  12   b  and  12   a  respectively, at mounting holes  12   a   3  and  12   b   3 . Furthermore, locating pins  33  are provided and are received in pin holes  12 A 4  and  12 B 4  formed in the inner and outer case  12   b  and  12   a  respectively. These ensure that the shafts  3  and  4  will not rotate when appropriately installed. As mentioned above, the directional gear  13  can be selectively moved over the outer directional shaft  3  by the user. The directional gear  13  will at all times be in contact with the arm gear  8 . However, according to its selected position, it will either be in contact with the forward drive gear  15 , or reverse drive gear  14 , so as to move the wheelchair forward or back. In moving from one selected position to the other, the directional gear  13  slides over the outer directional shaft  3 . The directional gear  13  can also be disengaged completely when positioned between the forward and reverse gears  15  and  14  so as the disconnect the arm gear  8  from the forward and reverse gears  15  and  14 . 
     Reference is now made to the mounting structures and function of the forward drive gear  15  and reverse drive gear  14 , shown in greater detail in  FIG. 8  of the drawings. In  FIG. 8  of the drawings, it will be seen that the forward and reverse drive gears  15  and  14  respectively, are mounted about the drive axle shaft  2 . One end of the drive axle shaft  2  attaches to the transmission inner case  12   b  by means of a bearing housing  7 ″, and a bearing housing  6 ″, which attach to the transmission inner case  12   b  by means of mounting bolts  9 ″. This is similar to the connections described above with respect to the arm axle shaft  1 . 
     The opposing end of the drive axle shaft  2  attaches to the wheel  34  through appropriate linkages, as will be described. 
     The forward drive gear  15  is mounted on a forward gear free wheel  17 , having a threaded bore  17   a . The threaded bore  17   a  receives the sleeve  20  with outer thread  20   a , and the forward drive gear  15  is connected by drive gear outer C-clips  19   a  and associated washers  18   a . The forward drive gear  15  has of course a series of gear teeth  15   a  which engage corresponding gear teeth on the directional gear  13 . 
     Further, outer C-clips  19   a  and associated washers  18   a  fasten the forward drive gear  15  onto the drive axle shaft  2 . Rotation of the forward gear  15  in response to axial rotation of the drive axle shaft  2  is effected due to the presence of the drive axle to forward directional gear lock keys  32   d , as clearly seen in  FIG. 4  and  FIG. 8  of the drawings. 
     The reverse drive gear  14  is similarly mounted with substantially identical components onto the drive shaft  2 , including a reverse gear freewheel  16 , as well as washers and c clips. 
     Reference is now made to  FIG. 8  of the drawings, and to particularly those components outside of the transmission outer case  12   a , comprising the braking components, and the mechanism for connecting the drive axle shaft  2  to the wheel  34 . 
     A rear wheel hub  31  is provided as associated with the rear wheel, and attaches to the drive axle  2 . Lock keys  32   b  are provided for locking the rear wheel hub to the wheel  34 . Keyway grooves  31   b  receive the lock keys  32   b . Also on the hub  31  there are formed keyway grooves for securing the hub  31  to the drive axle  2 . 
     A brake system is provided for the user to provide braking force to the wheels in order to slow or stop the wheelchair  200 . The brake system comprises a disc brake rotor  29 . The disc brake rotor  29  is secured to a drive axle mount  27 , which has an internal bore  27   b  through which the drive axle  2  passes to connect with the rear wheel hub  31 . The disc brake rotor  29  is secured to the mount  27  by means of mount bolts  28 . 
     Between the disc brake rotor  29  and the transmission outer case  12   a  there is located a bearing housing  6 ′″, connected to a bearing  7 ′″, a structure similar to other mounts already described above. 
     The disc brake rotor  29  is engaged by a disc brake caliper  24 , which is in turn fastened to a disc brake caliper mount  23 . A bolt  26  mounts the caliper  24  to the caliper mount  23 . Further details of the brakes, cables and application thereof are described below. 
     It will, therefore, be seen that the drive axle shaft  2  mounts both the forward and reverse drive gears  15  and  14 , and also engages the disc brake rotor  29  before engaging the hub  31 . Importantly, it will be observed from the presence of the gear freewheel to drive axle mountings  20  and the threads  20   a  around the outside of mountings  20  that each of the forward and reverse drive gears  15  and  14  respectively are able to spin freely in one rotational direction, while engaging the drive axle shaft  2  in the other rotational direction. It will of course be appreciated that the direction of free wheel rotation is opposite in each of the forward and reverse drive gears  15  and  14  respectively so as to facilitate desired forward and reverse motion of the wheelchair. 
     To summarize the operation of the propulsion mechanism from the arm lever  22  to the rear wheel  34 , it will be appreciated that the arm lever  22  can be moved back and forth by the user so as to rotate the arm gear  8 . The arm gear  8  in turn engages the directional gear  13 , and the directional gear  13  is selectively engaged to either the forward drive gear  15  or the reverse drive gear  14 . Depending upon which of these forward or reverse drive gears  15  or  14  is engaged by the directional gear  13 , the fore and aft motion of the arm lever will either drive the rear wheel  34  to move the wheelchair forwards or backwards. The directional gear  13  itself can be moved over the outer directional outer shaft  3  so as to selectively engage either the forward drive gear  15  or the reverse drive gear  14 . While the chair is engaged in the forward position, moving the arm lever forward ultimately rotates the drive axle in a manner that moves the wheelchair forward, and the freewheel inside the forward directional gear while engaged directionally to move the chair forward free spins with no engagement and thus no forward movement when the arm lever is pulled back towards the user. When the user again pushes the arm lever  22  away, the arm gear  8  through the directional gear  13  to the forward drive gear  15  moves the wheelchair forward. The same process is in effect but in the reverse direction when the reverse directional gear is engaged and the freewheel in the engaged direction rotates the drive axle  2  in a direction that moves the wheelchair backwards and is motivated by the user pulling the arm lever towards him/herself and the freewheel inside the reverse directional gear  14  while engaged directionally to move the chair backwards free spins with no engagement and thus no backward movement when the arm lever is pushed away from the user. When the user again pulls the arm lever  22  towards him/herself, the arm gear  8  through the directional gear  13  to the reverse drive gear  14  moves the chair backwards. 
     Direction Gear Operation and Structure 
     Reference is now made to  FIGS. 9 to 13  of the drawings which show the various mechanisms and operation for moving the directional gear  13 , the position of which in turn determines forward or rearward motion of the wheelchair. 
     As will be appreciated from the previous description, and particularly  FIGS. 4 and 6  of the drawings, the directional gear  13  moves over the outer directional shaft  3 . The movement of the directional gear  13  is in fact determined by adjusting the axial position of the inner directional shaft  4 , which slides axially, bringing the directional gear  13  along with it, to engage the forward drive gear  14  or the reverse drive gear  14 . In  FIG. 9  of the drawings, there is shown a view of the cables, referenced as numeral  60 , which at one end connect to a shift mechanism whereby the operator of the wheelchair can move the cables. At the other end, the cables  60  extend into a linkage case  37 , which has a linkage case lid  38 , and which is secured to the transmission inner case  12   b  (or  12 ( b )) by mounting bolts  37   d.    
     The cables  60  connect to an arm lever  36  which has opposing access slots  36   d . The end of the cables  60  are received within these access slots  36   d . The cables  60 , inside the linkage case  37 , are guided over pulleys  40  and  41  which have grooves  40   a  and  41   a  to receive and guide the cables  60 . The pulleys  40  and  41  are mounted within the linkage case  37  by means of appropriate pivot pins  42  and  43 . Furthermore, the arm lever  36  is mounted on pivot pin  44 , which is received in pin hole  36   c , and the arm lever  36  pivots about the pivot pin  44  in response to motion of the cables  60 , as will be described. 
     It will be seen that the arm lever  36  has one end to which the cables attach, within the linkage case  37 , and an extending arm which projects outside the linkage case  37 , and pivotally attaches to the inner shaft  4  at shaft pin  45 . 
     At this point, reference is best made to  FIGS. 11 and 12  of the drawings, which show detailed views of the linkage case  37  in section, for both sides of the gear transmissions, each of these figures in turn showing the inner shaft  4  in different positions. With reference to  FIG. 11 , it will be seen that when the directional cable  60  is pulled so as to move out of the linkage case  37 , the cable causes the arm lever  36  to pivot about the pivot hole  36   c  such that the access slot  36   d  on the left hand side is pulled up, causing the lever arm  36  to move to the left. This movement of the lever arm  36  causes the inner shaft  4  to slide to the left, or into the space between the transmission inner cases  12   b  and  12   b . This is best illustrated in  FIG. 11 . The inner shaft  4  slides within the outer directional shaft  3 . The bolts  35  thread into sleeve  5  and extend through the outer shaft  3  via slots the  3   d  and engage the inner shaft via openings  4   a . Thus, when inner shaft  4  is actuated by connection to arm lever  36  which is actuated by operator operating the cable  60 , the directional gear  13  engages forward drive gear  15 , as shown in  FIG. 11  of the drawings. The bolts  35  are able to move laterally within the slot  3   d , and, therefore, as the inner shaft  4  moves axially, so it will be able to move the directional gear  13  within the confines provided by the dimensions of the slot  3   d . These dimensions are sufficient to move the inner shaft  4  from the position shown in  FIG. 11  to that shown in  FIG. 12 , when the action on the cables  60  is reversed. As the inner shaft  4  moves within the outer directional shaft  3 , the directional gear  13  is moved correspondingly and changes its engagement from the forward drive gear  15  to the reverse drive gear  14 . In this way, appropriate driving of the wheelchair  200  by fore and aft movement of the arms  22  will result in a change of direction due to this altered gear engagement and configuration from forward to reverse or vice versa. 
       FIG. 13  offers a detailed overview of all of the components on both sides of the drive mechanism  230 , and the setting of the linkage case  37  and arm lever  36  is obviously configured so that the relevant drive gear position is established on both sides of the wheelchair to ensure that forward, reverse or turning movement is established. 
     It should also be appreciated that the position of the arm lever  36  and the two inner shafts  4  (one associated with each of the wheels) can be configured in various formats. In one situation, the drive gear  13  will contact the forward drive gears  15  on both sides. In another configuration, the drive gear  13  will engage the reverse drive gears  14  on both sides. In yet another configuration, the drive gear  13  on one side will engage the forward drive gear  15 , while it will engage the reverse drive gear on the other. The opposite configuration is also true. Yet another configuration would be where the drive gear  13  engages either the forward or reverse drive gear  15  or  14  on one side of the wheelchair  200 , but on the other side, the drive gear  13  may be positioned between the forward drive gear  15  and the reverse drive gear  14  so that there is no engagement at all. 
     Reference is now made to  FIG. 14  of the drawings which shows a detail of a part of the arm lever  22  and disc brake operating mechanism. The arm lever  22  is mounted on the arm axle shaft  1 . The arrow  22   a  shows how the arm lever, to be described in further detail below, can be moved forward and aft to drive the transmission. 
     Also shown in  FIG. 14  is an end on view of the brake system, including the disc brake rotor  29  and the disc brake caliper  24 . The disc brake caliper  24  is mounted with bolts  26 . It can be seen that the disc brake rotor  29  is also mounted on the drive axle shaft  2 , the structure of which is clearly illustrated in the drawings. Axle lock screws  30  on opposite sides of the axle shaft  2  are shown. 
     A cable  61  is provided with a cable operating handle, activated by the user as will be described, while the opposing end of the cable engages the disc brake caliper  24 . Operation of the disc brake caliper  24  causes engagement with the disc brake rotor  29 , which in turn slows down or alternately stops rotation of the drive axle shaft  2 , and hence the wheel  34 . The disc brake caliper  24  and rotor  29  generally operate in an otherwise conventional fashion. 
     In  FIG. 15  of the drawings, a side view of the various gears is shown. On the right side, and activated by the arm lever  22 , is the arm gear  8 , having arm gear teeth  8   a , and an inner bore  8   b . A keyway groove  1   c  facilitates the proper connection between the arm axle shaft  1  and the arm gear  8 . 
     The arm gear  8  drives the directional gear  13 , having directional gear teeth  13   a . The shaft sleeve  5  can be seen, and the gear bearing  21  is located between the directional gear  13  and the shaft sleeve  5 . The shaft sleeve  5  is mounted on the outer directional shaft  3 , which is in turn on the inner directional shaft  4 , the structure and operation therebetween having already been described above. 
     In  FIG. 15  of the drawings, the reverse drive gear  14  is shown with reverse drive gear teeth  14   a . The reverse gear freewheel  16  is shown, upon which the reverse drive gear  14  is mounted, and the freewheel  16  is mounted on the sleeve  20 . The sleeve  20  itself is mounted on the drive axle shaft  2 , and a lock key  32   d  ensures the appropriate connection therebetween. 
       FIG. 16  of the drawings shows a view similar to that in  FIG. 13  of the drawings, but the drive mechanism  230  has the appropriate covers. There is shown a left side transmission cover  66 , a right side transmission cover  67 , and a main frame to transmission frame mounting structure  68 . An alignment groove  68   a  is provided. With the various covers, the gears, shafts, and other operating components are shielded, which not only protects them from dust, dirt and other debris, but also operates as a safety barrier to ensure that the user or extraneous objects do not become ensnared in the drive train mechanism. 
     Arm Lever and Associated Structures 
       FIGS. 17 to 30  of the drawings show further details of the arm lever  22 , and its associated structures. There is provided an upper arm lever  22   a  and a lower arm lever  22   b , connected by hinge plates  101  and  101   a  and held together at hinge pivot pin  101   b . The hinge plates  101  are secured to the arm  22  by means of bolts  102 . On the side opposite that of the hinge plate  101 , there is formed a lock shaft  103  which slides in a series of guides  104 . The lock shaft  103  has a lock shaft tab  103   a , so that the upward movement of the lock shaft  103  within the guides  104  is limited by its engagement with the stop  105 . 
     In order to fold the upper arm  22   a  relative to the lower arm  22   b , the lock shaft  103  is raised until the lower end thereof has passed through all of the guides  104  on the lower arm  22   b . The upper arm portion  22   a  can then be pivoted about the hinge  101   b , as shown in  FIG. 18  of the drawings. In this way, the arms  22   a  and  22   b  can be folded so as to occupy less space, and make it easier for the storage and transport of the wheelchair  200 . 
       FIGS. 19 and 20  show a rear view and a front view of the upper part of the arm  22  with a hand grip  111 . The hand grip  111  has a hand grip gear shift activation sleeve module  112 , by means of which gear shifts may be made by rotation of the hand grip  111 , as will be described. It will be seen in  FIG. 20  that a lock shaft  109  is provided which slides in an upper shaft guide  108  and a lower shaft guide  107 . The limit of movement of the lock shaft  109  is controlled by the provision of a stop  110 . When the guides  108  and  107  are in axial alignment, and the lock shaft  109  passes therethrough, rotation of upper pod  106  and lower pod  123  is prevented. The upper pod  106 , and handle  111  can be rotated by sliding the lock shaft  109  upward out of the guide  107 , and rotating the handle  111 . Once rotated, as is seen in  FIG. 19 , the lock shaft  109  will be able to engage with the guide  107   a  on the opposite side, so that the hand grip  111  can be locked in a folded position when stored or transported. 
     In  FIG. 22  of the drawings, it will be seen that the gear shift activation sleeve  112  is mounted to the upper pod  106 , and a Teflon washer  117  sits between shoulder  112   b  and cover plate  118 . The cover plate  118  holds the activation sleeve  112  in place inside the upper pod  106 , and screws  119  fasten the cover plate  118  to the upper pod  106 . 
     In  FIGS. 23 ,  24  and  25  of the drawings, opposing end views of the arm and handle, as shown in  FIGS. 19 and 20 , can be seen. 
     With reference to  FIGS. 21 and 22 , there is shown a cross-section and exploded view respectively of the arm  22  and hand grip mechanism  111 , and the operation whereby rotation of the hand grip gear shift activation sleeve module  112  has the effect of moving the cables  60 , discussed in previous drawings, so as to effect the change of gear engagement for forward and rearward movement, turns and general direction control of the wheelchair  200 . 
     As previously described, the hand grip  111  attaches to the upper pod  106  and the gear shift activation sleeve attaches to hand grip  111 , as clearly shown in  FIG. 21  of the drawings. A cover plate  114  is provided, and spacer/washers facilitate movement. The hand grip  111  attaches to the upper pod  106  which is hollow, which in turn is attached to the lower pod  123 . In order to enable rotation of the upper pod relative to the lower pod, for folding as described above, a Teflon® washer  120 , including a shoulder  121   a , is provided to eliminate resistance between upper pod  106  and upper to lower hand grip assembly pods bolt  120 . The lower pod  123  in turn attaches to the arm  22 , also hollow, and in which the cables  60  are appropriately directed to the linkage case  37 , as illustrated in  FIG. 9  of the drawings. 
     It will be appreciated that the position of the cables  60  within the pods  106  and  123 , and their connection to the activation sleeve  112 , allows rotation through operation of the upper to lower hand grip assembly pods bolt  120  while at all times keeping the cable axially in the same position, so as to prevent twisting or snarling thereof. 
       FIG. 22  of the drawings shows some of the structure allowing proper positioning of the cable. First, the walls of the arm lever are received within the arm lever mounting recesses  123 ( f ) to ensure appropriate axial alignment. An internal passage  123   c  including a cable passage  123   d  and an internal gear shift cable case mounting area  123   e  allow appropriate cabling. The arm  22  is itself secured to the lower pod by appropriate fastening screws  124 . 
       FIGS. 26 to 28  of the drawings show movement of the hand grip gear shift activation sleeve module  112  activating the cables to change gears.  FIG. 26  is a back view ( FIG. 23  provides a front view and  FIG. 22  shows the back side of the sleeve  112  and its cover  114 ) showing the hand grip  111  and the cover plate  114 . Fastening screws  115  are provided, and the gear shifting cables  116   a  emerge from the hand grip assembly. 
     In  FIGS. 27 and 28 , the same view is shown but with the cover plate  114  removed.  FIG. 27  shows the cable in the first and drive position, while  FIG. 28  shows the hand grip gear shift activation sleeve module  112  position which changes the directional gear which is effected by the cable movement into the reverse position. In  FIGS. 27 and 28 , the cables  116   a  enter the activation sleeve module  112 , and each of the cables has a cable end  116   b  to ensure a secure connection. As will be seen in  FIG. 28 , the hand grip gear shift activation sleeve module  112  has been rotated approximately a one quarter turn, and the cables&#39; positions have been adjusted. As the cables move from their positions, as shown in  FIGS. 27 and 28  respectively, direction gear  13  is moved by the inner shaft  4  as a result of arm lever  36  movement, as has been clearly illustrated and described in  FIGS. 11 and 12  of the drawings. 
       FIGS. 29 and 30  show the arrangement of the brake lever. A brake lever  132  is pivotally connected by a bolt  133  to a lever mounting block  131 . A shoulder  131   a  extends outwardly on one side of the mounting block  131 , and connects to a  90 E cable bend  134 . The cable  61  is shown extending from the cable bend  134 , and passes through the cable guide  135 . By appropriate directing, the cable  61  ultimately reaches the disc brake caliper  24 , as illustrated in  FIG. 14  of the drawings. The operator, by pulling on the brake lever  132 , is able to tension the cable and therefore activate the disc brake caliper  24  which in turn engages the disc brake rotor  29  for the purposes of slowing down or stopping the wheelchair  200 . 
     Seat and Transmission Mounting to Main Frame 
     In accordance with one embodiment of the invention, a mechanism for attaching the seat as well as the transmission mount and the drive mechanism  230  to the central support  208  of the frame  202  is described. 
     With particular reference to  FIG. 31  of the drawings, it will be seen that the main frame  202  has a central support  208 . Within the central support  208 , there are formed two spaced openings  74   a , each of the spaced openings  74   a  having an upper shoulder receptacle  74   b  and a lower shoulder receptacle  74   c . Two seat mounting posts  73  are inserted from above into each of the openings  74   a . Each seat mounting post  73  comprises a shoulder  73   c , a taper  73   a  and a threaded portion  73   b . When the seat mounting post  73  is inserted into the opening  74   a , the shoulder  73   c  will be received and rest in the upper shoulder receptacle  74   b , preventing further downward movement of the post  73  into the opening  74   a.    
     Additionally, a pair of transmission mounting posts  72  are provided, each post  72  having a shoulder  72   c , a taper  72   a , and a threaded bore  72   b . Each mounting post  72  is placed in the opening from the bottom, and the threaded bore  72   b  receives the threaded shaft  73   b  of the seat mounting post  73 . The seat mounting post  73  and transmission mounting post  72  are tightened with respect to each other by conventional rotation, until such time as the shoulder  72   c  of the post  72  is received within the lower shoulder receptacle  74   c  (and shoulder  73   c  is received within shoulder receptacle  74   b .) These are firmly tightened with respect to each other. As will be described below, the seat mounting post  73  extending outwardly above from the central support  208  forms the basis for connecting the seat bottom  77 , while the downwardly extending tapers  72   a  form the basis for fastening the transmission mount  68  and the drive mechanism  230  to the central support  208 . In this way, it will be appreciated that the central support  208  carries both the seat bottom and the transmission. It should be noted that the mechanism for connection illustrated in  FIG. 31  and other drawings is one preferred embodiment of the invention, and many different methods and structures may be utilized for properly securing these components to the main frame. 
     The seat bottom  77  is connected to the seat mounting post  73  via a seat mount  75 . The seat mount  75  includes a pair of receptacles  75   b , each spaced and dimensioned so as to receive and fit with the tapers  73   a  on the mounting post  73 . The seat mount  75  includes a shoulder  75   d  and, at its lower end, an alignment groove  75   a  to facilitate a proper fit with central support  208 . Further, the seat mount  75  comprises a lock plate slot  75   c  for receiving a lock plate  76 , as will be described. The seat mount  75  and the seat bottom will preferably be fastened to each other with a super strong epoxy, although other forms of connection are within the scope of the invention. 
     In use, the seat mount  75  with the seat bottom  77  attached, is placed over the mounting post  73 , and the tapers  73   a  are received within the receptacle  75   b . The lock plate  76  is located in the lock plate slot  75   c .  FIGS. 33 and 34  show a bottom view and side view respectively of the lock plate  76 . It will be seen that the lock plate has a pair of access slots  76   a , and an access slot locking engagement area  76   c . When assembling the seat mount  75  onto the mounting post  73 , the lock plate  76  is positioned such that the larger portion of the access slot  76   a , circular in dimension as seen from  FIG. 33 , is aligned with the receptacle  75   b . In this way, when the tapers  73   a  are placed in the receptacle  75   b , the lock plate  76  will not provide any obstruction thereto. When the seat mount  75  is in the proper position, the lock plate  76  can be moved into the locking position, such that the locking engagement area  76   c  engages with a groove  73   d  in two sides of the mounting posts tapered area  73   a  that are 180° apart from each other, and that accept the locking engagement area  76   c  of the locking plate  76 . Conversely, the seat mounting posts  73  can be released by moving the lock plate  76  in the opposite direction to allow the tapers  73   a  to be withdrawn. 
     In  FIG. 34  of the drawings, it will be seen that a lock/unlock lever  147  is provided on the lock plate  76 . The lever  147  rotates about pivot pin  147   a , and is connected at pivot pin  148   a  to a lock post  148 . A tab  149  is secured to the lock plate  76  by means of a screw  150 , which is received in a screw access hole  149   a . The tab  149  limits movement of the lever  147  so that it is not able to extend above the level of the tab  149 . This is safety feature to ensure that no injury or other adverse effects are sustained. 
     When the lever  147  is rotated about pivot pin  147   a  in a counter-clockwise direction, the lock post  148  is raised above the lower level of the lock plate  76  and the projection of the lock post over the edge, which would otherwise prevent removal of the lock plate  76 , now allows the lock plate  76  to be moved by a sliding motion from the lock plate slot  75   c . A tension spring plate  147   b  operates on the lever  147  so that in the normal position the lock post  148  will extend over the lower surface of the lock plate  76 , and the lever  147  will be in the position shown in  FIG. 34  of the drawings. 
     With particular reference to  FIG. 32  of the drawings, there is shown the seat mount  75  with the lateral shoulder  75   d . The lock plate slot  75   c  is shown, in which the lock plate  76  is received, as described above. The area  75   e  is a finger-accessed clearance recess to facilitate the pulling of the sliding lock plate  76 . The recess  75   f  receives the end of the lock post  148 , as shown in  FIG. 34  of the drawings, to lock the lock plate in position. 
     As will be seen in  FIGS. 31 and 35 , there is provided a transmission mount  68 . The transmission mount  68  has a pair of mounting openings  68   d  which rest on frame support tubes  52  and  53 . Reference may be made to  FIG. 5  of the drawings which shows the various transmission cases and support tubes. With the transmission mount  68  resting on the frame support tubes  52  and  53 , the clamp modules  69  are registered therewith, and have a semi-circular opening which fits below the frame support tubes  52  and  53 . The clamp modules  69  are then bolted, using bolts  70 , the bolts  70  passing through the holes  69   a , and having threaded ends which engage the screw holes  68   e  on the transmission mount. In this way, the transmission  230  is secured to the transmission mount  68 . 
     The transmission mount  68  is secured to the mounting post  72  in substantially the same manner as the seat mount  75  is secured to the mounting post  73 . Thus, the transmission mount has receptacles  68   b , a slide lock groove  68   c  and a lock plate  71  which is received within the lock groove  68   c , engaging the alignment tapers  72   a  in the receptacle  68   b . The lock plate  71  can be axially moved in a sliding fashion so as to selectively release and engage the grooves  72   d  (positioned in much the same manner as the grooves  73   d  in the mounting posts  73 ) in the tapers  72   a  in substantially the same way as described above with respect to the tapers  73   a  and lock groove  76 , and the details will not, therefore, be repeated at this point. 
       FIG. 35  shows a front view of the transmission mount  68 , including the receptacle  68   b , the lock groove  68   c , and also the finger-access area  68   f  to allow access to and sliding of the lock plate  71 . 
     In  FIG. 36  of the drawings, there is shown the seat  77  and the transmission  230  mounted to the frame  208  (also numbered  74  in other figures and/or embodiments) in the assembled position.  FIG. 36  also shows the shift linkage case  37  and the directional arm lever  36 , the operation of which by the cables  60  moves the inner directional shaft  4 , as has already been described above. Note that the different frame configurations shown in  FIGS. 41 and 42  of the drawings may have a similar seat and transmission mounting system, and the components and structure described above may be used on each of the two parts which comprise the central support. 
     Front Wheel Assembly and Mounting 
     Reference is now made to  FIGS. 37 to 40  of the drawings which show the front wheel mounting, the shock assembly and related components. In  FIGS. 37 and 38  of the drawings, the main frame  202  has thereon a housing  74   d  or a “leg” aperture that projects outwardly from the main frame  202  but is not separate from the main frame structure. The assembly is mounted upon the housing  74   d . A front wheel  87  is provided having a tire  86  and a fender  85 , substantially over the wheel. 
     A main shaft  88  is provided, the main shaft  88  having attached thereto an upper shock mount  89  and a pair of swing arms  90 . The swing arms  90  are connected by bolt  82 . The shock mount  89  connects at the other end thereof to a support collar  91 . A shock shaft  96  extends between an upper cup spring holder  95   a  and a lower cup spring holder  95 . About the shock shaft  96  is the shock spring  97  which is received within the cup spring holders  95   a  and  95  respectively. A mounting bolt  93  mounts the upper part of the shock shaft  96  to the shock mount  89 . The upper collar  91  is actually a part of the upper cup spring holder  95   a , and the lower collar  92  is part of lower cup spring holder  95 . A mounting bolt  93  is provided which is not directly over the top end of shock shaft  96 , as shown in drawing. The shaft  96  in this situation can rise up through cup holder  95   a  as the spring is compressed and then falls back down when decompressed but is kept from falling through the cup holder  95   a  by way of a washer and clip  99  and  100 . The bolt  93  may actually connect the collar  91  to shock mount  89 . Note that the same shaft  96  travel does not occur through the lower collar  92 . In  FIG. 38 , a collar  92  is provided at the lower end of the shock shaft  96 , and is securely connected to the swing arms  90 , as well as the wheel  87  by means of the axle shaft  94 . 
     The main shaft  88  is received within the main shaft support  78  located within the housing  74   d . Upper and lower bearings  81  with inner races  81   a  and outer races  81   b  are secured within the housing  74   d , and washers  79  and c-clip recesses  78   b  for the c-clips  62  are provided. The main shaft  88  is received within the bearings  81 , and is capable of rotational movement within the bearings  81 , but not axial (or vertical) movement. Axial movement limitations are controlled by washers  80  resting upon the bearing inner races  81   a  and c clips  63  inserted into main shaft c clip recesses  88   a.    
       FIG. 40  shows more details relating to the mounting of the wheel  87 . Within the fender  85 , bearings  83 , having outer races  83   b  and inner races  83   a  are provided for receiving the axle shaft  94 . A c-clip  98  and washer  84  secures one end of the axle shaft  94 . The other end of the axle shaft is received within the swing arm  90  and collar  92  of the shock. A washer  126  and c-clip  127  are also provided on the other side of the wheel for stabilizing the wheel  87 . 
     Seating Structure 
     In many wheelchairs currently available in the marketplace, the seat bottom is a flat piece of fabric that is attached on the left and right side of the wheelchair frame and stretched across the wheelchair, much like an old school yard swing. There may often be a foam cushion laid upon this seat. The seat back is of the same design. This type of seat design does not offer any correct or corrective skeletal structural support for the user and as many in wheelchairs have no use of their legs, sitting in a non-structured seat such as that described above may often make it very difficult to sit up straight. This can lead to back, neck, and shoulder pain as the body fights for a correct posture from an unsupported base. Furthermore, the poor positioning of the user due to the nature of the seat can actually make it more difficult to operate the wheelchair. 
     The benefits and advantages of a wheelchair seat that offers skeletal structural support in an ergonomic manner is therefore clear. Starting with the seat bottom of the wheelchair of the present invention, when the hip joints and pelvis are held in a correct position the spine is then in a correct position and the posture of the user is more likely to be structurally correct. Even with limited muscular control, the user is positioned and supported in a correct structural posture. It has been found that this type of support reduces neck, back, and shoulder pain as a result of the user not having to constantly try to achieve straight posture from a non supportive base structure. It also places the user in a better position for operating the wheelchair. 
     Therefore, the seat structure of the wheelchair of the present invention is formed so that the seat bottom corrals both outer sides of each leg/hip joint which in turn causes the upper legs to be directed in the correct position thus directing the users glutes (or posterior muscles) and pelvis to be lowered into a recessed area designed for correct pelvic tilt which then offers correct spinal support. The forward center area of the seat bottom raises slightly to direct separation between the legs in-seam area, thus offering further base support. The overall design of the seat bottom is focused on two very specific goals, namely: (1) to give support along the outside of the legs, along the inside of the legs, to cradle the pelvis and hip joints to offer correct spinal posture; and (2) to spread the users weight over the entire surface area of the seat bottom.  FIGS. 1 and 2  of the drawings show a seat bottom which generally incorporates these structures and contours. 
     Many users of current wheelchairs may cite as the major discomfort the pressure from the seat bottom, with no structural support, as the weight of the body is lowered in the center and the sides squeeze in causing pressure. 
     While sizes of users certainly can differ, it is incontrovertible that the skeletal structure of a human is consistent throughout the species, and it is based on this fundamental similarity that the overall design characteristics of the seat bottom of the invention can be reduced in size or increased in size to fit a particular user. 
     The seat back in accordance with the present invention is also designed with correct structural support in mind. As with many automotive seats, this seat back offers supportive lumbar pads which offers additional lower spine support as well as upper spine support while allowing unrestricted movement of the arms. 
     The main reason current wheelchair seats do not offer spinal support is directly related to the position the users body must be in to effectively motivate the wheel chair. Current wheelchair users must lean forward to motivate a current design wheel chair, effected by directly rotating the wheels. If leaning forward is the optimum position for motivating a wheelchair then healthy spinal position does not come into play as a requirement. The present invention allows for and actually encourages correct healthy spinal position to motivate this wheel chair. 
     Further Embodiments 
     Reference is now made to  FIG. 44  and those figures following which show a further embodiment of a wheelchair in accordance with the present invention. In this description of  FIG. 44  and those following, the same reference numerals used in previous figures are utilized to the extent possible for corresponding components and parts. 
       FIG. 44  of the drawings shows a wheelchair  300 , which comprises a pair of rear wheels  34 , a drive mechanism  230  as previously described and illustrated, a front frame arm  333  attached to the drive mechanism  230  at the drive mechanism end case internal frame  331 , and an arm lever  22  for manually propelling the wheelchair  300 . A seat frame  336  is mounted on the drive mechanism  230 , and a seat  204  with seat back  206  is itself mounted on the seat frame  336 . A wheel  87  is mounted at the end of the swing arm  90  connected to a main shaft  88  and the support  78  mounted at the end of the front frame arm  333 , and having the general construction as described in previous embodiments. 
     In this embodiment at least, the reference to drive mechanism should be considered the drive mechanism itself, the housing or part thereof in which the actual drive mechanism may be located, or both of these. 
     The drive mechanism  230  has a transmission outer case  12   a . The arm lever  22 , having a hand grip  111  and a brake lever  132 , is moved forward and backward to drive the rear wheel  34  through the drive mechanism  230 . The operation and construction of the propulsion mechanism has been described in previous figures, and the same or similar mechanisms are used in the embodiments presently under discussion. 
     In this embodiment of the invention, the arm lever  22  may have the desired curvature shown, or may be of any other shape. Further, the arm lever and handle rotation joints are not present in this embodiment, and the arm lever does not, therefore, bend or have a joint, and the handle will not rotate. However, it should be appreciated that these options may be utilized in this embodiment if desired. 
     As will be discussed in further detail below, the seat  204  is releasably attached to the seat frame  336 , and may be removed and replaced thereon. Further, the seat  204  and seat back  206  can be moved between an unfolded and folded position. In addition, the front frame arm  333  is mounted on the drive mechanism end case internal frame  331  so that it can be moved relative thereto, such that the wheelchair  300  can be folded and compacted for storage or transportation as will be described. 
       FIG. 44  shows between the seat  204  and seat back  206  an upper seat hinge  301  and a lower seat hinge  302 . A seat hinge pivot bolt  303  is utilized in relation to these hinges to permit folding of the seat back  206  over the seat  204 , as will be described. 
       FIG. 44  also shows the front frame arm  333  attached to the transmission end case cover  332 , and this structure includes a front frame arm pivot bolt  321 , a front frame arm position plunger  325 , and a plunger access hole  333   a , as will described in further detail below. 
       FIG. 45  of the drawings shows the wheelchair  300  illustrated in  FIG. 44  with the seat back  206  moved into the folded position so as to overlie the seat  204 .  FIG. 46  illustrates the wheelchair as shown in  FIG. 45 , wherein the seat  204  and seat back  206  have been removed from the seat frame  336 . Further description relating to one embodiment for the removal and attachment of the seat  204  to the seat frame  336  is provided hereunder. 
       FIG. 47  illustrates a wheelchair  300  wherein the front frame arm has been partially folded from its extended position as shown in  FIG. 44 .  FIG. 48  illustrates the wheelchair  300  wherein the front frame arm  333  is in the fully folded position. It will be seen that the wheelchair  300  shown in  FIG. 48  is in the fully compacted or folded position, especially appropriate for transportation and storage.  FIG. 49  of the drawings shows the compacted wheelchair  300  as shown in  FIG. 48 , together with the separated seat in the folded position, illustrating the compactness and portability of the wheelchair  300 . 
       FIGS. 50 ,  51  and  52  showed detailed views of the seat of the wheelchair  300 , and the mechanism for its folding and unfolding. The lower seat hinge  302  is connected to the seat  204 , and the upper seat hinge  301  is connected to the seat back  206 . The lower seat hinge  302  includes a number of apertures  304  which allow the seat back  206  to be positioned at various angles relative to the seat  204 . A seat hinge pivot bolt  303  can also be seen in  FIG. 50  of the drawings. 
       FIG. 51  shows a rear view of the seat back  206  when locked relative to the seat  204 , while  FIG. 52  shows the same situation but in the unlocked position. It will be seen that a plunger housing  305  and a spring  307  and retainer  308  within the plunger housing  305  permit axial movement of the plunger  306 . The plunger  306  can engage in one of several apertures  304 , as seen in  FIG. 50  of the drawings, and a different seat back position can be achieved depending upon which aperture is selected. 
     The plunger  306  is attached to a pull cable  309  which is mounted in the hole  319 . The cable  309  passes through a directional plate  311 , which is attached to the seat back by mounting screws  312 . The cable  309  attaches to an aperture  319  in a cable transfer plate  313 . It will be appreciated that the cable  309  from both sides of the seat are received by the transfer plate  313 . An upper pull cable  314  extends from the transfer plate  313  and passes through a housing  315  secured to the seat back by housing mounts  316  which are fastened using screws  317 . The pull cable  314  emerges from the opposite end of the housing  315 , and is attached to an activation handle  318  at aperture  319 . 
     In the rest position, the spring  307  urges the plunger  306  outwardly from the housing  305  and into an aperture  304  in the seat hinge  302 . When the activation handle  318  is pulled upwardly, the cables  314  and  309  pull the plunger  306  against the action of the spring  307 , removing the plunger  306  from the aperture  304 . In this position, the seat back  206  is movable between the fully unfolded position as shown in  FIG. 50 , and a fully folded position as shown in  FIG. 49 . Of course, intermediate positions can also be set.  FIG. 52  shows the plunger  306  in the unlocked position permitting the lower seat hinge  302  to move relative to the upper seat hinge  301 . 
       FIGS. 53 and 54  show a bottom view of the locking mechanism of the front frame arm  333  to the drive mechanism end case internal frame  331 . Two sides of the front frame arms  333  are shown. The frame arms  333  are attached to the drive mechanism end case internal frame  331  by means of pivot bolt  321 , spacer  322  and fastening nut  323 . The front frame arms  333  are thus able to pivot relative to the drive mechanism end case internal frame  331  about the axis of pivot bolt  321 . 
     A plunger  325  is mounted within a plunger housing  324 , and a spring  326  and retainer  327  allow the plunger  325  to move axially. In the rest position, the spring  326  urges the plunger  325  outwardly into a plunger access hole  333   a . When the plunger  325  is extended and received within the access hole  333   a , relative movement between the frame  333  and the drive mechanism end case internal frame  331  is prohibited. The plunger  325  is connected to a cable  328  at one end thereof, the other end of the cable  328  being connected to a handle  329 . The cables  328  from each side are secured in different apertures  329   b  on substantially opposing sides of a pivot mount  329   a , about which the handle  329  can rotate. 
     When the handle  329  is rotated, the respective cables  328  pull the plunger  325  on each side out of the access holes  333   a , against the action of the springs  326 . This unlocked position is illustrated in  FIG. 54 , and permits the frame  333  to pivot about pivot bolt  321 , thus allowing the frame  333  to move between the fully unfolded position shown in  FIG. 44  of the drawings, and the fully folded position shown in  FIG. 49  of the drawings. 
       FIGS. 55 and 56  show a detailed view of the connection between the frame  333  and the drive mechanism end case internal frame cover  332 .  FIG. 55  illustrates the locked in usage position, as shown more broadly in  FIG. 44 , while  FIG. 56  shows the locked in storage position as generally illustrated in  FIG. 49 . The frame ARM  333  pivots about the pivot bolt  321 . In  FIG. 55 , the plunger  325  can be seen in the lower aperture  333   a , while in  FIG. 56 , the plunger  325  can be seen in the upper aperture also referenced  333   a . Of course, the plunger  325  remains in a fixed position, and the aperture in which it engages will depend upon the rotational position or orientation of the frame arm  333 . 
       FIG. 57  shows a view similar to that in  FIG. 44 , but without showing the rear wheels  34  or the arm lever  22 .  FIG. 57  thus clearly shows the mechanism by means of which the seat frame structure  336  is attached to the end case cover  332  at the forward end of the frame structure and to the transmission outer case  12   a  at the rear end of the frame structure, as shown in this figure, and the seat  204  is in turn attached to the seat frame structure  336 . 
       FIG. 58  of the drawings shows a detailed perspective view of the seat frame  336 . The seat frame  336  comprises a pair of more or less U shaped members  336   a  connected in spaced relationship by transverse connectors  336   b . Each U-shaped member  336   a  has a mounting part  335  at each end thereof, each mounting part  335  including a bolt hole  337 . As seen in  FIG. 57 , the seat frame  336  mounts on the drive mechanism  230  by being appropriately bolted thereto in a manner such that the transverse connectors  336   b  are substantially horizontal. Each U-shaped member  336   a  has a pair of bushing mounting holes  341 , each of which receives a lock shaft  343 .  FIG. 59  shows a bottom view of the seat frame  336 , and illustrates a lock system activation lever  344  mounted at pivot pin  346 . The activation lever  344  has mount holes  344   a  each of which receives a system linkage  347 . The system linkage  347  comprises a rigid line. The linkage  347  attaches to a lock shaft lower arm  343   b  through hole  343   c . A further linkage extends between the forward and aft lower arms  343   b.    
     When the activation lever  344  is rotated, the various linkages  347  will cause the lower arms  343   b  to rotate, which will have the effect of disconnecting an upper arm  343   a  on the opposing side of the bushing  342  to enable the fastening and unfastening of the seat  204  from the seat frame  336 . 
     Reference is made to  FIGS. 60A ,  60 B and  60 C which shows in further detail the fastening mechanism between the seat  204  and the frame  336 . As described above, the lock shaft bushing  342  sits in a mounting hole  341  of the frame  336 . The lower arm  343   b  of the lock shaft  343  extends below the bushing  342  and a lock shaft upper arm  343   a  extends above the bushing  342 . The upper arm  343   a  is releasably received in a locking mount cylinder  338  which has an access slot  339  and a securement slot  340  at substantially right angles thereto. The upper arm  343   a  engages in the access slot  339  and then is rotated into the securement slot  340  by appropriate manipulation of the activation handle  344 . When the upper arm  343   a  is in the securement slot  340 , the seat frame  336  will be releasably attached to the seat  204 . The cylinder  338  is bolted to the seat  204  by means of bolts through holes  338   a.    
       FIG. 61  shows a bottom view of the seat  204  with four locking cylinders  338  appropriately position so as to overlie and engage with the four upper arms  343   a  on the seat frame  336 .