1.  Field of the Invention
This invention relates to wheelchair devices and wheeled walker devices for assisting handicapped individuals to move about and, more particularly, to powered wheelchairs and walkers operable by the user or occupant thereof.  Specifically, the present invention relates to a wheelchair/walker combination which is adapted to permit the occupant to operate and move the device in a fully sitting position and to rise to an upright position without lower body muscular effort on the part of the handicapped occupant and to also operate and move the device from such an upright position. 
2.  Description of the Prior Art
Wheelchairs of various types and designs have been utilized for a considerable period of time for the purpose of transporting physically handicapped individuals having limited or no use of their legs, such as paraplegics and quadriplegics.  Wheelchair designs have become quite sophisticated as a result of efforts intended to enable handicapped individuals to have a degree of control over their own movements.  Thus, powered wheelchairs have incorporated a wide variety of control and safety devices to assist the handicapped operator thereof to achieve relatively independent movement and transportation.  A major disadvantage with wheelchairs in general, however, is that such devices, while assisting handicapped individuals in moving about an area, restrict such individuals to a relatively rigid sitting position within the chair which causes continual pressure contact on the same areas of the body.  This can lead to serious problems including skin and tissue degeneration, gangrene and the like.  In the case of children, lack of weight bearing on the legs can cause growth defects including leg shortness. 
Walker devices were designed to overcome some of the aforementioned problems relating to wheelchairs.  It has been shown that devices which enable a handicapped individual to remain in a standing position for relatively long periods of time (e.g. 2 or more hours), provide substantial advantages and benefits to handicapped individuals.  More specifically, passive standing has been shown to produce beneficial physiological effects which include reduction of bone and calcium loss, reduction of hypercalciuria and urinary calculi, increased muscular tone and maintenance of range of motion, improved orthostatic circulatory regulation, and increased bladder pressure.  In addition, substantial psychological benefits result from permitting physically handicapped individuals to remain in a standing position.  Such standing positions provide increased independence and morale as well as permit the handicapped individual to position himself so as to be able to work at various working stations.  Consequently, walker devices of various types have been developed to permit the handicapped individual to remain in a standing position for periods of at least several hours at a time. 
Walkers present a number of problems which are not encountered in wheelchair designs.  Such problems arise in part from the fact that a user's body extends substantially above the center of gravity of the walker, thereby leading to the possibility of tipping over.  If a walker is designed with a relatively large base area to avoid the tipping problem, maneuverability of the walker is restricted.  Additionally, it becomes more difficult to provide support for the user of the walker.  Also, movement into a walker is generally much more difficult than transferring to a wheelchair since the user must not only transfer to the device, but must also achieve a standing position, and many users of such devices have no leg control or use whatsoever. 
Early walker devices such as illustrated in U.S. Pat.  No.  2,168,424 are useful although they have numerous problems and deficiencies.  Most particularly is the fact that such early devices require the handicapped operator of the device to utilize his own muscular arm power to maneuver the device about a room or a ground surface area.  Thus, the usefulness of the device was dependent entirely on the physical capability and strength of the user. 
Powered walker devices were developed which overcame the aforementioned deficiency.  Such power devices, as illustrated in U.S. Pat.  No.  3,872,945, enable the user to stand within the walker and maneuver and move about an area utilizing a battery power pack or the like carried on the walker itself.  This particular patent discloses such a device which enables the user to be highly maneuverable in an area. 
Many power walker devices have a rear entryway and carry the power pack and other apparatus up front.  These designs limit the distance which the operator of the walker may reach forwardly of the walker and thereby restrict usefulness when working at a table or other work space positioned in front of the walker.  Thus, in such arrangements, an operator must preferably position himself sideways to a work area in order to provide close proximity thereto.  This sideways orientation to a work area presents certain problems in terms of comfort of and flexibility to the user.  The device illustrated in U.S. Pat.  No.  3,872,945 overcomes this problem and enables the user to be stationed within the walker apparatus very close to the front thereof, thereby enabling the user to reach beyond the walker a significant distance. 
A major problem inherent with all of the aforementioned powered walker designs, including that of U.S. Pat.  No.  3,872,945 is that an individual must be assisted into the walker.  Moreover, once an individual is positioned within these walkers, they must remain in a standing position.  If an individual positioned within the walker wishes to be placed in a seated position, the individual must be entirely removed from the walker.  Thus, these designs limit overall usefulness of the walker.  Accordingly, there remains a need for a powered walker apparatus which is easy for a handicapped individual to enter and exit unassisted and which enables an operator to move freely from a sitting to a standing position, again unassisted.  Furthermore, there remains a need for such a device that will preferably also function as a wheelchair thereby permitting the occupant to move about in a seated position as well and thereby obviate the need for transference between walker and wheelchair.