Abstract:
The present invention relates to a mobile vehicle or wheelchair having the ability to provide stabilized transport to at least one individual on a variety of surfaces, slopes and/or terrains. The mobile unit or wheelchair of the invention may travel across smooth and very rough surfaces, slopes of varying or different angles and various outdoor terrains (including grassy, rocky, sandy, muddy and/or hilly terrains). In one aspect of the invention, the height of any part of the unit or the overall height of the device may be adjusted preferably to raise or lower the center of gravity. For example, the height of the device may be lowered to provide more stable transportation. In another aspect, the device may be adjusted to increase or decrease the size of the footprint (or any part of the footprint) of the device. For example, the footprint of the device may be enlarged to provide more stable transportation. Preferably, both the height of the device (or any part of the device) and the size of the footprint (or any part of the footprint) may be adjusted preferably to provide more stability.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 60/836,293, filed Aug. 8, 2006, the disclosure of which is incorporated by reference herein. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention is directed to a mobile vehicle or wheelchair having the ability to provide stabilized transport to at least one individual on a variety of surfaces, slopes and/or terrains. 
         [0004]    2. Background Art 
         [0005]    Wheelchairs have proven to be the most practical solution to mobility for individuals that have problems walking, due to age, sickness, and/or disabilities. While both conventional and motorized wheelchairs provide improved mobility to such individuals, current designs fail to adequately address the need of the individual to have broad access to various locations. In particular, current designs pose hazards to the occupant when operated on sloped and/or uneven surfaces. Current designs also fail to address various medical issues for certain individuals including poor circulation. Moreover, little has been done to provide an affordable design allowing broader availability. 
         [0006]    The present invention addresses these and other needs. 
       BRIEF SUMMARY OF THE INVENTION 
       [0007]    The present invention relates in general to a mobile unit, a vehicle, a mobile device and/or wheelchair which provides stabilized transportation for one or more passengers. In one aspect of the invention, the height of any part of the unit or the overall height of the device may be adjusted preferably to raise or lower the center of gravity, and in a preferred aspect, the height of the device is lowered to provide more stable transportation for the user of the invention. In another aspect, the device may be adjusted to lengthen or shorten the base of the device, and in a preferred aspect, the base of the device is lengthened to provide more stable transportation for the user of the invention. Preferably, both the height of the device (or any part of the device) and the length of the base (or any part of the footprint) may be adjusted to provide more stability. 
         [0008]    In one embodiment, the wheelbase of the wheelchair extends or retracts to vary the size of the footprint, while the height of the seat member of the wheelchair increases or decreases, which varies the location of the center of gravity. 
         [0009]    In another embodiment, the base of the wheelchair extends or retracts to vary the size of the footprint, while the height of the seat member of the wheelchair increases or decreases, which varies the location of the center of gravity. The location of the center of gravity as well as the size of the footprint may contribute to the stability of the wheelchair, and through their adjustment the stability can be increased or decreased. In one aspect, while the height of the seat member pivots to a decreased height, leg rests pivot and extend from the main frame to support a user&#39;s legs throughout transition. 
         [0010]    In another embodiment, the base of the wheelchair extends or retracts to vary the size of the footprint, while the height of the seat member of the wheelchair increases or decreases, which varies the location of the center of gravity. In one aspect, the seat member is adjustable between an upright and a lowered position, while the base is adjustable between a compacted and an extended position. In one aspect, when the seat member in an upright position, and the base is in a compacted position, the wheelchair is suited to support a user sitting upright, legs bent at the knee. This position is conducive to indoor use, as the smaller footprint of the device and higher seat member in this configuration makes it easy to maneuver in an indoor environment, among other benefits. When the seat member is in a lowered position, and the base is in an extended position, the wheelchair is suited to support a user sitting in a reclined straight-leg (or substantially straight-leg) seated position. This position is conducive to outdoor use, as the lengthened wheelbase, larger footprint and lowered seat member in this configuration provide for greater stability in traveling over potentially uneven terrain, among other benefits. 
         [0011]    In one embodiment, the relative movement of the base (or one or more wheels as part of the base configuration) and the lowering of the seat allows the center of gravity of the user/unit combination to be lowered and thus provides more stability for the operation of the unit by the user. The combination of lowering the seat and increasing the size of the footprint allows the user to sit in a relatively flat position. Preferably the operation of the invention allows the legs of the user to be extended (preferably the legs being flat or substantially flat). This feature of the invention allows the user&#39;s legs to extend in such a manner as to provide comfort to the user and/or increase blood circulation in the user&#39;s legs. 
         [0012]    The invention is particularly suited for use by handicapped individuals or any user who desires aid in moving from place to place. In a preferred aspect, the device of the invention comprises a base or platform (which may be prepared of any material such as metal, plastic, wood and the like or combinations thereof, and can be designed in various configurations such as a frame, a solid platform and the like or combinations thereof). In another aspect, the base or platform (or any part of the base or platform) may be adjusted to increase or decrease the size of the footprint of the base or platform. In a preferred embodiment, the footprint is increased in size to provide more stability to the unit. Preferably, the size of the footprint may be increased by extending one or more portions of the base or platform. Such one or more portions may be extended or retracted, for example, by utilizing extension/retraction tracks and/or extension/retraction rods and/or extenders that allow two or more parts of the base or platform to separate and move away from or toward each other in such a manner to allow the overall footprint size of the base to increase or decrease. 
         [0013]    In yet another aspect, the base or platform comprises a plurality of wheels, wherein the wheels may be designed (including various shapes, sizes and/or tread configurations) to accommodate any terrain. Preferably, the invention utilizes any number of wheels including at least two, at least three, at least four, at least five, at least six, at least seven, at least eight or more wheels depending on the need. In another aspect, the size of the footprint of the base may be increased or decreased by extending or retracting one or more wheels which may be included as part of the base or platform configuration. For example, one or more wheels may be extended or retracted, for example, by utilizing one or more extension/retraction tracks and/or extension/retraction rods and/or extenders that allow at least one wheel to separate and move away from or toward the base or platform in such a manner to allow the overall footprint size of the base or platform to increase or decrease. 
         [0014]    In another aspect, the invention may be powered or moved manually by an individual or user or may be motorized (such as by one or more electric and/or combustion motors or combinations thereof). In yet another aspect, any one or a number of the wheels of the device may be powered by such one or more motors and preferably the unit of the invention is a multi-wheel drive unit, wherein a number or all of the wheels of the unit are driven by one or more drive motors. Preferably, the device of the invention comprises four (4) wheels and preferably at least two of such wheels (and preferably all four) are capable of being driven by one or more motors. In another embodiment, one or more motors of the invention are utilized to raise and/or lower all or any part of the unit. In another aspect, one or more motors are utilized to increase and/or decrease the size of the footprint of the unit (or any part of the unit). In another embodiment, the same or different motors may be used to operate all or any number of the functions of the unit, and in a preferred aspect one motor is utilized to move the device, to increase and/or decrease the size of the footprint (or any part of the footprint) and to raise and/or lower all or any part of the unit. In utilizing the unit of the invention, the different functions of the device may be operated separately or simultaneously depending on the need of the user. When one or more motors provide operation of any or all of the features of the unit, the unit may also comprise one or more control devices allowing the user to control and operate the different features of the invention. For example, one or more control panels may be used to move the unit, adjust the size of the footprint and/or adjust the center of gravity. 
         [0015]    The device of the invention preferably comprises at least one seat or chair unit, and in a preferred aspect, the seat or chair may be adjusted to provide more comfort and/or stability for the user. In a preferred aspect, the at least one chair or seat may be adjusted up or down relative to the base or platform. Preferably, the chair or seat is lowered to provide more stability. Lowering the chair or seat according to the invention also provides better access to ground level activities, while increasing the height of the chair or seat provides better access to off the ground activities, such as easy access to table tops and counters. In a preferred aspect of the invention, the chair or seat is lowered by moving it generally forward relative to the front of the unit or the front of the chair, preferably by pivoting the seat such that it is lowered as it moves forward. In a different aspect, the chair or seat is lowered by moving it generally back away from the front of the unit or relative to the front of the chair, preferably by pivoting the seat such that it is lowered as it moves back. In another aspect, the seat or chair is lowered by moving it down with little or no general movement forward or backward relative to the base of the unit. 
         [0016]    In a preferred embodiment of the invention, both the chair/seat adjustment and the footprint size adjustment may be operated simultaneously or separately. Preferably, the chair/seat is lowered and the size of the footprint is increased and this operation provides the unit with more stability during operation. In one aspect, the seat/chair is lowered by moving it forward relative to the base or relative to the front of the chair, and the front of the base (or one or more wheels of the base configuration) is extended. In another aspect, the seat/chair is lowered by moving it back relative to the base or relative to the front of the chair, and the back of the base (or one or more wheels of the base configuration) is extended. In a different aspect, the chair may be lowered backwards while the front of the base (or one or more wheels of the base configuration) is extended. In a related aspect, the chair may be lowered by moving it forward while the back of the base (or one or more wheels of the base configuration) is extended. As will be apparent, one or multiple parts of the base (or one or more wheels of the base) may be extended as the chair/seat is adjusted. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES 
         [0017]    The advantages and features of the present invention will become better understood with reference to the following more detailed description and claims taken in conjunction with the accompanying drawings, in which like elements are identified with like symbols, and in which: 
           [0018]      FIG. 1  is a pictorial view of one embodiment of the wheelchair or device of the invention in which the wheelchair is in the uppermost position, with the leg protection cover on the footrest member and the component cover on the main frame, both of which are removed on all other drawings to better show operation. 
           [0019]      FIG. 2  is another pictorial view of one embodiment of the wheelchair or device of the invention in which the wheelchair is in the uppermost position. 
           [0020]      FIG. 3  is a pictorial view of one embodiment of the wheelchair or device of the invention in which the wheelchair is in the lowest position. 
           [0021]      FIG. 4  is a schematic representation of one embodiment of the wheelchair or device of the invention showing the operating mechanisms with the wheelchair in the uppermost position. 
           [0022]      FIG. 5  is a schematic representation of one embodiment of the wheelchair or device of the invention showing the operating mechanisms with the wheelchair in the lowest position. 
           [0023]      FIG. 6  is a pictorial view of one embodiment of the wheelchair or device of the invention showing the telescopic device operably secured to the main frame. 
           [0024]      FIG. 7  is a pictorial view of one embodiment of the wheelchair or device of the invention showing the front portion of the base. 
           [0025]      FIG. 8  is a partial section and view of a telescopic device of the device or wheelchair of the invention which when operated allows the footprint of the device or wheelchair to be increased (when extended) or decreased (when retracted). 
           [0026]      FIG. 9  is a partial section and rearward view of the telescopic device and the motor connected by a drive belt or chain for operation of the telescopic device. 
           [0027]      FIG. 10  is a pictorial view of the seat member or seat support which when operated pivots forward or backward to allow it to move up or down. 
           [0028]      FIG. 11  is a partial section and view of the forward connection of the seat member or seat support showing various pivot points allowing movement of the support up or down. 
           [0029]      FIG. 12  is a partial section and view of the rearward connection of the seat member or seat support showing one pivot point allowing movement of the support up or down. 
           [0030]      FIG. 13  is a pictorial view of one embodiment of the operating mechanism showing the motor, the extender(s) (or telescopic device), the seat support and the base adjuster. 
           [0031]      FIG. 14  is a partial section and rearward view of an optional lifting assist device connected to the main frame (or platform) and a seat member or seat support. 
           [0032]      FIG. 15  is a partial section and view of the extension structure and footrest and leg rest pivotally connected by a swing arm support. 
           [0033]      FIG. 16  is a partial section and view of the footrest/leg rest member connected to a seat member or seat support by a slide mount enabling the footrest/leg rest to be adjusted. 
           [0034]      FIG. 17  is a pictorial view of the tray embodiment to contain various components for the unit or wheelchair of the invention, including one or more batteries and/or one or more circuit boards. 
           [0035]      FIG. 18  is a pictorial view of another embodiment of the wheelchair in an upright position, in this embodiment a linear actuator is used to extend or retract the device. 
           [0036]      FIG. 19  is a side view of another embodiment of the wheelchair in an upright position, in this embodiment a linear actuator is used to extend or retract the device. 
           [0037]      FIG. 20  is a pictorial view of another embodiment of the wheelchair in a lowered position, in this embodiment a linear actuator is used to extend or retract the device. 
           [0038]      FIG. 21  is a side view of another embodiment of the wheelchair in a lowered position, in this embodiment a linear actuator is used to extend or retract the device. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0039]    The present invention relates in general to a wheelchair, a mobile unit, a vehicle, or another similar mobile device which provides stabilized transportation for one or more passengers. In one aspect of the invention, the height of the seat member may be adjusted preferably to raise or lower the user&#39;s position, and in a preferred aspect, the height of the seat member is lowered to provide more stable transportation for the user of the invention by lowering the center of gravity closer to the operating surface. In another aspect, the wheelchair, mobile unit, vehicle, or mobile device may be adjusted to increase or decrease the size of its footprint (or any part of the footprint), and in a preferred aspect, the footprint is enlarged to provide more stable transportation for the user of the invention. Both the height of the seat member and the size of the footprint (or any part of the footprint) may be adjusted to provide more stability. 
         [0040]    Preferred embodiments of the present invention are now described. While specific configurations and arrangements are discussed, it should be understood that this is done for illustrative purposes only. A person skilled in the relevant art will recognize that other configurations and arrangements can be used without departing from the spirit and scope of the invention. It will also be apparent to a person skilled in the relevant art that this invention can be employed in a variety of other devices and applications. While specific examples described may refer to a wheelchair, the invention may equally apply to any mobile unit, vehicle, or any other mobile device. 
         [0041]    As depicted in  FIGS. 1-5 , wheelchair  2  of the present invention is basically comprised of base assembly  15  (further comprising extension structure  8  and main frame  4 ), seat assembly  13 , and leg support assembly  17 . 
         [0042]    Base assembly  15  provides the base structural support for wheelchair  2 . Base assembly  15  is comprised of extension structure  8  and main frame  4 . In operation, a user can control extension structure  8  to extend away from or move toward main frame  4 , increasing or decreasing the size of the footprint of wheelchair  2 . As the footprint increases, the stability of wheelchair  2  increases, as the footprint decreases, the maneuverability of wheelchair  2  increases. By varying the footprint, a user can achieve the optimum balance of maneuverability and stability for a given situation. The components of base assembly  15  may be prepared of any material such as metal, plastic, wood and the like or combinations thereof, and can be designed in various configurations such as a frame, a solid platform and the like or combinations thereof. Preferably, base assembly  15  is made of aluminum, or other suitable durable, lightweight metal, such as chrome molly. 
         [0043]    Extension structure  8  may be extended or retracted by utilizing telescopic devices  12 , depicted in  FIG. 6 . Telescopic devices  12  allow part of the frame to extend or retract to increase or decrease the size of the footprint of the wheelchair or unit. Telescopic devices  12  may be extension/retraction tracks and/or extension/retraction rods and/or extenders that allow extension structure  8  to move away from or toward main frame  4  in such a manner to allow the overall footprint size of the base to increase or decrease. Extension structure  8  is secured operable to the main frame  4  by telescopic devices  12 . Preferably extension structure  8  is made of the same or similar material as main frame  4 .  FIG. 7  shows the front portion of the base (which may comprise one or more wheels) and this portion of the base may be extended or retracted based on adjustment of the extension device or telescopic device. Adjusting the front portion of the wheelchair allows the footprint of the base to be increased when extended or decrease when retracted. Main frame  4  and extension structure  8  are supported by two rear wheel assemblies  9  and two front wheel assemblies  11 , respectively. The substantially rectangular shape formed between the four wheel assemblies provides for a much more stable structure than would a triangular shape formed between three wheel assemblies. In yet another aspect, the base or platform comprises a plurality of wheel assemblies  9 ,  11  wherein wheel assemblies  9 ,  11  may be designed (including various shapes, sizes and/or tread configurations) to accommodate any terrain. In the embodiment shown in the figures, front wheel assemblies  11  and rear wheel assemblies  9  are utilized, but the invention may utilize any number of wheel assemblies, including at least two, at least three, at least four, at least five, at least six, at least seven, at least eight or more wheel assemblies, depending or the need. In another aspect, the size of the footprint of the base may be increased or decreased by extending or retracting one or more wheel assemblies  9 ,  11  which may be included as part of the base or platform configuration. For example, one or more wheel assemblies  9 ,  11  may be extended or retracted, for example, by utilizing one or more telescopic devices  12  that allow at least one wheel assembly  9 ,  11  to separate and move away from or toward the base or platform in such a manner to allow the overall footprint size of the base or platform to increase or decrease. 
         [0044]    Outer guide housings  14  of telescopic devices  12  are secured to main frame  8 , and slide sections  16  of telescopic devices  12  are secured to extension structure  8 . In addition to, or in place of telescopic devices  12 , any other extending/retracting device or devices that are mechanical, electrical, pneumatic or hydraulic could be used, for example a screw cylinder, linear actuator, or total hydraulic system can be used to drive the extending/retracting device or devices. In one embodiment, depicted in  FIGS. 6 and 8 , slide section  16  moves through bearing(s)  18 . Suitable bearings include a flanged or sleeve type journal bearing, a brushing, a fluid bearing, Rulon, Orlite, Frelon or other type linear bearings that give adequate support while substantially reducing sliding friction. Threaded shaft  20 , similar to a jackscrew, is secured operable to outer guide housing  14  as by angular contact bearings  22  or other type thrust bearings. Female threaded member  24 , which can be, for example, a nut, is secured to slide section  16  and adapted to move along threaded shaft  20  as that member rotates. A lubricant, such as grease, may be used on the threaded shaft to reduce friction. As shown in  FIG. 9 , motor  26 , secured to main frame  4 , transmits torque to gears  28  on threaded shafts  20  of telescopic devices  12  through gear  30  on motor shaft  32 , via a belt, gear train, or chain  34 . As threaded shaft  20  rotates, female threaded member  24  and slide section  16  move extension structure  8  away from or draw extension structure  8  to main frame  4 . Adjustable motor brackets  35  achieve chain tension. 
         [0045]    In another embodiment (not shown), motor  26  drives a worm gear, which in turn meshes with and drives the rotational motion of a pinion gear. The pinion gear in turn meshes with and drives the translational motion of a rack, as in a typical rack and pinion mechanism. The rack is secured to extension structure  8 , and the translational motion of the rack moves extension structure  8  away from or draws extension structure  8  to main frame  4 . Other mechanisms may also be used to translate power from motor  26  to telescopic devices  12 . 
         [0046]    In another embodiment, as discussed below with respect to  FIGS. 18-21 , the motion of extension structure  8  is controlled by a mechanism in which slide tubes controlled by a linear actuator replace the threaded shaft and female threaded member above. The slide tubes are connected at one end to main frame  4 , and at the other end to extension structure  8 . Activation of the linear actuator causes slide tubes to extend or retract, which moves extension structure  8  away from or toward main frame  4 , respectively. 
         [0047]    At least one seat may be attached to the seat member or seat support in such a manner that when operated, the seat is raised or lowered based on movement of the seat member or support. Components of seat assembly  13  connect to both extension structure  8  and main frame  4 . Seat assembly  13  comprises at least one seat member  6 , and in a preferred aspect, seat member  6  may be adjusted to provide more comfort and/or stability for the user. In a preferred aspect, seat member  6  may be adjusted up or down relative to the base or platform. Preferably, seat member  6  is lowered to provide more stability. Lowering seat member  6  according to the invention also provides better access to ground level activities and is more stable, which is useful for outdoor use, where the terrain may be more uneven and unpredictable, while increasing the height of seat member  6  provides better access to off the ground activities, such as easy access to table tops and counters and is more maneuverable, which is useful for indoor use, where turning tight corners and fitting through narrow doorways is a concern. In this manner, the single wheelchair can be used for a variety of activities, providing the user with a greater range of motion, and can operate both indoors and outdoors. In a preferred aspect of the invention, seat member  6  is lowered by moving it in the direction of the front of the unit or generally forward relative to the base or platform, preferably by pivoting seat member  6  such that it is lowered as it moves forward. In a different aspect, seat member  6  is lowered by moving it generally back relative to base or platform, preferably by pivoting seat member  6  such that it is lowered as it moves back. In another aspect, seat member  6  is lowered by moving it down with little or no general movement forward or backward relative to the base or platform. 
         [0048]    Seat assembly  13 , depicted in  FIG. 10 , which in operation lowers or raises seat member  6  as described above, is a rigid, yet operable framework. Much of this framework is made up of preferably aluminum tube stock or other suitable durable, lightweight metal such as chrome molly, but can also be steel, fiber, wood, plastic, metal, any other material with suitable functional qualities, or any combination thereof. Seat member sides  36  are secured to and conjoined by axle rods  38  and  40 , as shown in  FIGS. 11 and 12 . At least one seat member  6  may be attached to seat member sides  36 . Seat member links  42  and  44  are pivotally secured to axle rod  38  and maintained in a uniform manner by spacers  46  and  48 , depicted in  FIG. 11 . Seat member links  50  are pivotally secured to axle rod  40  and maintained in a uniform manner by spacer  52 , depicted in  FIG. 12 . Seat member  6  is coupled to telescopic devices  12  and extension structure  8  by seat member links  42 ,  44  and  50 , depicted in  FIG. 13 . Seat member links  44  and  50  are pivotally secured to outer housing guides  14  of telescopic devices  12  by four connecting pins  56 , which can be pins, bolts, rivets, radial bearings, or any other suitable connection mechanism, best depicted in  FIG. 6 . Seat member links  42  are pivotally secured to a pin block  54  on extension structure  8 , depicted in  FIG. 7 . Connecting pins  56  on outer housing guides  14  of telescopic devices  12  and pin block  54  on extension structure  8  are anodized to prevent wear. Pivotal connections  58  of seat member links  42 ,  44  and  50  contain brass bushings  60 , or other type bushings or bearings, and bushings  62 , made of an engineering plastic, such as that available from DuPont under the tradename DELRIN, or other type bushings or bearings are placed at the sides of pivotal connections  58  to prevent binding and galling when the seat is raised or lowered. 
         [0049]    Due in part to the formation of seat assembly  13  and the pivotal connections of seat assembly  13  to extension structure  8  and main frame  4  (through the pivotal connections on telescopic devices  12 ), as base assembly  15  operates to move extension structure  8  away from or toward main frame  4 , this motion drives a transition in seat assembly  13  which causes seat member  6  to move forward and down or backward and up, while maintaining a horizontal surface. In this manner, the footprint size may increase or decrease simultaneously, or otherwise in synchronization, as seat member  6  raises and lowers. As shown in  FIG. 13 , by operation of the motor, the extenders may be extended or retracted and such extenders are operably linked to the seat support and the front of the base (the wheel configuration of the base). As the extenders are extended or lengthened, the seat support pivots in such a manner as to allow the seat support to move forward so that the support is lowered. The lengthening of the extenders also allows the base front (the wheel configuration of the base) to be extended thus increasing the footprint of the base. This operation will be explained in greater detail below. 
         [0050]    Due to an occupant&#39;s bodyweight, when seat member  6  is in a lower position, a large amount of torque is needed from motor  26 , and deflection problems of seat member links  42 ,  44  and  50  may occur when lifting seat member  6 . In  FIG. 14 , a gas spring cylinder  64  or cylinders is used to assist lifting. Gas spring cylinder  64  may also be a torsion spring. Gas spring cylinders  64  could also be a spring mechanism, a hydraulic mechanism, or any other suitable lifting mechanism. Gas spring cylinder  64  provides additional force to assist seat member links  50  (occupied or not occupied by a user) to move up, thus raising seat member  6 . One or more gas spring cylinders  64  may be used according to the invention depending on the need. Gas spring cylinders  64  are pivotally secured to main frame  4  and to swing arms  66  pivotally secured to seat member links  50 . 
         [0051]    Depicted in  FIG. 15 , leg support assembly  17  is comprised of leg rest member  10 , swing arms  68 , spacers  70 , and protection cover  82 . Alternatively, leg rest member  10  can be a bent-tube type leg rest. Leg rest member  10  is pivotally secured to extension structure  8  by swing arms  68  and pins  74  connected to slide blocks  76 . A spacer  70 , made of an engineering plastic, such as that available from DuPont under the tradename DELRIN, is used on the sides of pivotal connections  72  of swing arms  68  to prevent seizing and galling. Pins  74 , best depicted in  FIG. 16 , are securely attached to slide blocks  76  on seat member links  42  and travel through parallel slots  78  on leg rest member  10 . Washers  80 , made of an engineering plastic, such as that available from DuPont under the tradename DELRIN, are used on the front and rear of parallel slots  78  of footrest member  10  to prevent binding and galling. Protection cover  82  is secured to footrest member, depicted in  FIG. 1 , over parallel slots  78  and pins  74  on slide block  76 , to prevent injury to the occupant&#39;s legs. As the front portion of the unit extends, the footrest/leg rest pivots preferably in a flat or horizontal position or substantially flat or substantially horizontal position. In addition to, or in place of swing arms  68  and slide blocks  76 , any other extending/retracting device or devices that are mechanical, electrical, pneumatic or hydraulic could be used, for example a screw cylinder, linear actuator, or hydraulic system can be used to drive the extending/retracting and pivoting motions of leg rest member  10 . In operation, which is discussed in greater detail below, leg support assembly  17  protects and guides a user&#39;s legs throughout motion of wheelchair  2 , in such a way as to maintain comfort and facilitate independent operation by the user, without assistance from others. 
         [0052]    In another embodiment, the position of leg rest member  10  is controlled by a linear actuator between seat  6  and leg rest member  10 . A linear bearing and rod are attached to each of seat member links  42 . In this embodiment, due to the force of the linear bearing and rod throughout the transition, leg rest member  10  extends and pivots to allow a user&#39;s legs to lay flat as seat  6  changes from an upper position to a lower position, and leg rest member retracts and pivots to allow a user&#39;s legs to bend at the knee as seat  6  changes from a lower position to an upper position. As shown in  FIGS. 18-21 , extension structure  8  extends from main frame  4  driven by linear actuator  19 . Linear actuator  19  is pivotally connected at one end to seat member link  42 , and pivotally connected at the opposite end to main frame  4 . In this embodiment seat member link  42  is forced away from or toward main frame  4  by the linear motion of linear actuator  19 . As seat member link  42  moves, it pivots at the point of connection with linear actuator  19 , and in a fully extended state, seat member link  42  lays over linear actuator  19  to provide additional stability. Actuator support member  21  is attached to main frame  4 , and is shaped to accommodate linear actuator  19  axially. When linear actuator  19  extends it pivots at the point of connection with main frame  4  and lays itself into the recess in actuator support member  21 , providing additional support and stability for wheelchair  2 . Extension support members  23  are attached to extension structure  8  at one end, and main frame  4  at the opposite end. During the extension/retraction of linear actuator  19 , extension support members  23  extend or retract accordingly, in order to provide support on each side of wheelchair  2 . 
         [0053]    In one embodiment, the relative movement of the base (or one or more wheel assemblies  9 ,  11  as part of the base configuration) and the lowering of seat member  6  allows the center of gravity of the user/unit combination to be lowered and thus provides more stability for the operation of wheelchair  2  by the user. In one aspect, the combination of lowering the seat and increasing the size of the footprint allows the user to sit in a relatively flat position. Preferably the operation of the invention allows the legs of the user to be extended (preferably the legs being flat or substantially flat). Leg rest member  10  supports the legs and feet of the user throughout the transitions of wheelchair  2 . Leg rest member  10  is shaped in such a way so as to retain and guide the legs of the user through the transitions, which is a key feature especially for an individual without internal control of his or her legs, such as a paralyzed individual. This feature of the invention allows the user&#39;s legs to extend in such a manner as to provide comfort to the user and/or increase blood circulation in the user&#39;s legs. It assists in transitioning the position of the user&#39;s body without requiring him or her to leave wheelchair  2 . 
         [0054]    Since electrical components are used in the present application, battery or batteries tray  84  and circuit board tray  86 , depicted in  FIG. 17  are secured to main frame  4 . Batteries tray  84  and circuit board tray  86  may be removable for service and repair, and may be replaceable. In  FIG. 1 , cover  88  is secured to main frame  4  to protect the occupant from pinch points when seat is being raised or lowered and the electrical components from the environment. 
         [0055]    In preferred embodiments of the invention, both the seat adjustment and the footprint size adjustment may be operated simultaneously or separately. Preferably, seat member  6  is lowered as the size of the footprint is increased and this operation provides the unit with more stability during operation. In one aspect, seat member  6  is lowered by moving it forward relative to the base, and the front of the base, extension structure  8 , is extended. In another aspect (not shown), seat member  6  is lowered by moving it back relative to the base, and the back of the base (or one or more wheel assemblies  9  of the base configuration) is extended. In a different aspect (not shown), the chair may be lowered backwards while the front of the base, extension structure  8 , (or one or more wheel assemblies  11  of the base configuration) is extended. In a related aspect (not shown), seat member  6  may be lowered by moving it forward while the back of the base (or one or more wheel assemblies  9  of the base configuration) is extended. As will be apparent, one or multiple parts of the base (or one or more wheel assemblies  9 ,  11  of the base) may be extended as seat member  6  is adjusted. 
         [0056]    Operationally, wheelchair  2  components are able to move relative to one another in order to change the size and shape of the footprint of wheelchair  2 , as well as change the height of seat member  6  relative to a surface on which wheelchair  2  is operating. In combination these functions allow an operator to use wheelchair  2  while sitting upright, or while reclining, and to change between these positions. 
         [0057]    For explanatory purposes, the fully upright formation of wheelchair  2  (depicted in  FIGS. 1 ,  2 , and  4 ) is referred to as Position A, while the fully reclined formation of wheelchair  2  (depicted in  FIGS. 3 and 5 ) is referred to as Position B. Also for explanatory purposes it is assumed that wheelchair  2  begins in Position A. 
         [0058]    In Position A, seat member links  42  are substantially vertical, while seat member links  44  form an acute angle with seat member links  44 . Seat member links  50  remain substantially parallel with seat member links  44 , forming a four-bar mechanism with seat member sides  36  as the connecting link. A user in wheelchair  2  while it was in Position A would be sitting upright, legs resting within leg rest member  10 , bent at the knees, for example, at an angle approximating 90 degrees, such as at an angle within 20 degrees of 90 degrees (e.g. 70, 80, 90, 100 or 110 degrees). 
         [0059]    Upon activation of motor  26 , motor  26  drives rotation of threaded shaft  20 . As threaded shaft  20  rotates, female threaded member  24  is forced along threaded shaft  20 , in an axial direction moving away from motor  26 . The axial motion of female threaded member  24  drives slide section  16  and extension structure  8  away from main frame  4 , increasing the footprint of wheelchair  2  as it does so. Wheel assemblies  11  move with and support extension structure  8  during this transition. Seat member links  42  are pivotally attached a pin block  54  on extension structure  8 . 
         [0060]    As extension structure  8  moves away from main frame  4 , the angle between seat member links  42  and seat member links  44  increases, as does the distance between pin block  8  and main frame  4 . This motion draws seat member links  44  and  50  to rotate forward, about fixed pivot points at connecting pins  56 . This rotation forces seat member sides  36  forward and down, while remaining substantially horizontal, ensuring that the operator, who is seated on seat member  6  which bridges seat member links  36 , will remain safely and comfortably in place while seat member  6  is lowered. 
         [0061]    While seat  6  transitions in this manner, leg support assembly  17  extends away from seat member  6  and pivots along with the user&#39;s legs at the knee, as the user&#39;s legs extend, increasing the angle between the lower leg and upper leg, as that angle approaches 180 degrees. Throughout the transition, swing arm  68 , pins  74  and slide blocks  76  maintain support for and control of the user&#39;s legs, ensuring that the transition occurs ergonomically, comfortably and safely for the user. 
         [0062]    Once extension structure  8  is fully extended, wheelchair  2  is in Position B, as depicted in  FIG. 3 . In this position, the front of the device (including the front wheels) is moved forward and the seat is lowered (preferably the seat pivots forward as it is lowered). In a preferred aspect, the distance between the footrest and the seat in the down position is such that the legs of a user will lay flat to provide for better blood circulation. In position B, because leg rest member  10  travels away from main frame  4  with extension structure  8 , a user&#39;s legs are fully extended, for example, the angle between the upper and lower legs in this position may be substantially 180 degrees, such as within 20 degrees of 170 degrees (e.g. 150, 160, 170 or 180 degrees), and the user is in a seated-reclined position. In position B seat member  6  is at its lowest, and the footprint is at its largest. The two wheel assemblies  11  are fully extended at their farthest distance from the two wheel assemblies  9 , resulting in maximum stability. In a preferred aspect, the distance between the footrest and the seat in the down position is such that the legs of a user will lay flat to provide for better blood circulation. In Position B, seat member links  42 ,  44 , and  50  are nearly horizontal, however they retain a sufficient angle from horizontal so as to facilitate the transition from Position B to Position A by way of the driving horizontal force of extension structure  8 , to help prevent deflection or binding of the structure. Additionally, gas spring cylinders  64  assist in returning seat member links  42 ,  44 , and  50  to Position A, by introducing a force along the body of seat member links  50 . In so doing, gas spring cylinders  64  also decrease the amount of torque that must be supplied by motor  26  in order to initially draw extension structure  8  toward itself. 
         [0063]    While in Position B wheelchair  2  of the preferred embodiment is in its most stable position. By rotating seat assembly  13  forward and down, and at the same time extending extension structure  8  forward, the result is to place the center of gravity centrally between wheel assemblies  9  and  11 , as well as to lower the center of gravity toward the operating surface or ground. 
         [0064]    When it is desired to transition from Position B to Position A, wheelchair  2  is operated such that threaded shaft  20  rotates in the opposite direction as when transitioning from Position A to Position B. This causes female threaded member  24  to travel back along threaded shaft  20  axially toward motor  26 , which draws extension structure  8  toward main frame  4 , and drives a reversal of the above-described motions of seat member links  42 ,  44 , and  50 , so that the angle between seat member links  42  and  44  decreases, and seat member links  44  and  50  rotate backward about connecting pins  56 , until all components have returned to the initial state of Position A. 
         [0065]    Throughout this cycle, seat member sides  36  remain substantially horizontal, allowing a user to transition from Position A to Position B and back again while remaining seated on seat member  6 . Additionally, either transition (from Position A to Position B or from Position B to Position A) can be interrupted at an intermediate position and either reversed or held at that position if the user desires to use wheelchair  2  in such a formation. 
         [0066]    Also throughout this cycle, the user is retained within the confines of wheelchair  2  in part by armrests  5  and leg rest member  10 . This is particularly important for a user who may have diminished control of his or her body. He or she may desire to change positions for any reason, including comfort, functionality, or for medical reasons, as discussed above. Armrests  5  will help to retain the torso and upper body of the user in place, while leg rest member  10  will help to retain the legs and lower body of the user in place. The particularized guidance that leg rest member  10  provides for the user&#39;s legs throughout this cycle is of pivotal importance, as it plays a significant part in the autonomy of the device, and allows the user to control the position of his or her legs through external means by activating the mechanisms of wheelchair  2 , when that user may not be able to control the position of his or her legs on his or her own. Because of the potential for injury while moving, leg rest member  10  is shaped such that it will protect the legs, and additionally provides for protection cover  82  to further prevent injury. 
         [0067]    Also throughout the cycle, battery or batteries tray  84  and circuit board tray  86  remain in a fixed position relative to main frame  4 . This results in increased stability and operative simplicity as opposed to a system where battery or batteries tray  84  and/or circuit board tray  86  would be required to change position in order to accommodate the motion of the mechanisms during a transition. 
         [0068]    At Position A or Position B, or any point while fixed or in transition in therebetween, the wheelchair  2  may be operated to travel in either a substantially forward or reverse direction by way of the drive wheels, which are preferably rear wheel assemblies  9 . Rear wheel drive provides greater stability and control. Wheelchair  2  may be powered or moved manually by an individual or user or may be motorized by one or more driving motors (not shown). Such motors may be electric and/or combustion motors or combinations thereof. In yet another aspect, any one or a number of wheel assemblies  9 ,  11  of the device may be powered by such one or more driving motors and preferably the unit of the invention is a multi-wheel drive unit, wherein a number or all of wheel assemblies  9 ,  11  of the unit are driven by one or more driving motors. Preferably, the device of the invention comprises four (4) wheel assemblies  9 ,  11  and preferably at least two of such wheel assemblies  9 ,  11  (and preferably all four) are capable of being driven by one or more driving motors. In another embodiment, one or more motors  26  of the invention are utilized to raise and/or lower all or any part of the unit. In another aspect, one or more motors  26  are utilized to increase and/or decrease the size of the footprint of the unit (or any part of the unit). In another embodiment, the same or different motors may be used to operate all or any number of the functions of the unit, and in a preferred aspect one motor  26  is utilized to move the device, to increase and/or decrease the size of the footprint (or any part of the footprint) and to raise and/or lower all or any part of the unit. 
         [0069]    In utilizing wheelchair  2 , the different functions of the device may be operated separately or simultaneously depending on the need of the user. When one or more motors provide operation of any or all of the features of the unit, the unit may also comprise one or more control devices  7  allowing the user to control and operate the different features of the invention. For example, one or more control devices  7  may be used to move wheelchair  2 , adjust the size of the footprint, and/or adjust the height of the unit and/or adjust the center of gravity. 
         [0070]    The present invention provides a number of advantages. In one aspect, the invention prevents the unit from tipping over during use on different types of terrain and in general the invention allows the user to perform a wider range of activities and provides a means by which a user can access a variety of places, some of which may have been previously difficult to reach. The invention also provides more comfort to the user and importantly may address medical concerns for certain individuals by for example allowing better circulation in lower extremities and preventing stiffness. The device decreases the amount of assistance from others that the user will need by allowing the user to autonomously change positions and thus prevent stiffness, and improve circulation, as well as improve the quality of life of the user by allowing him or her to operate more independently. 
         [0071]    It is to be appreciated that the Detailed Description section, and not the Summary and Abstract sections, is intended to be used to interpret the claims. The Summary and Abstract sections may set forth one or more but not all exemplary embodiments of the present invention as contemplated by the inventor(s), and thus, are not intended to limit the present invention and the appended claims in any way. 
         [0072]    The present invention has been described above with the aid of functional building blocks illustrating the implementation of specified functions and relationships thereof. The boundaries of these functional building blocks have been arbitrarily defined herein for the convenience of the description. Alternate boundaries can be defined so long as the specified functions and relationships thereof are appropriately performed. 
         [0073]    The foregoing description of the specific embodiments will so fully reveal the general nature of the invention that others can, by applying knowledge within the skill of the art, readily modify and/or adapt for various applications such specific embodiments, without undue experimentation, without departing from the general concept of the present invention. Therefore, such adaptations and modifications are intended to be within the meaning and range of equivalents of the disclosed embodiments, based on the teaching and guidance presented herein. It is to be understood that the phraseology or terminology herein is for the purpose of description and not of limitation, such that the terminology or phraseology of the present specification is to be interpreted by the skilled artisan in light of the teachings and guidance. 
         [0074]    The breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.