Abstract: A power wheelchair is capable of operating in either a two-wheel or a four-wheel drive configuration. The wheelchair includes first and second forward drive wheels in contact a supporting surface. First and second wheel support assemblies each include a support member pivotally connected to the wheelchair frame. Each wheel support assembly further includes a rear drive wheel and a rear non-driven wheel connected to the support member. At least one actuator is provided to control movement of the support members to pivot between a first position and a second position. In the first position, the rear non-driven wheel is moved into contact with the supporting surface and the rear drive wheel is moved out of contact with the supporting surface. In the second position the rear drive wheel is moved into contact with the supporting surface.

Abstract: A variable stiffness suspension system is provided for a wheelchair. The wheelchair has a frame and at least one wheel coupled to the frame for generally vertical movement relative to the frame. At least one sensor is provided for sensing an operating condition of the wheelchair. A controller is operatively coupled to the sensor. A controllable damper having a variable stiffness is coupled to the controller, the wheel and to the frame. The controllable damper is responsive to the controller and provides a force capable of being varied in a continuous manner. The force is resistive to movement of the wheel. The controllable damper is preferably a commercially available magneto-rheological damper or a variable orifice fluid damper. The controllable damper may be either a linear damper or a rotary brake.

Abstract: A reclining seat includes a base, a back frame and back support connected to the back frame for translation relative to the back frame. In a first embodiment, a mechanism is provided to couple the back frame to the back support such that rotation of the back frame relative to the base automatically translates the back support relative to the back frame. In a second embodiment, a mechanism is provided to allow a user to control movement of the back support independently of back frame rotation. Preferably, the reclining seat is incorporated into a wheelchair.

Abstract: A bi-directional anti-tip system for a wheelchair includes a pair of anti-tip system subassemblies actively lifting a leading anti-tip wheel when traveling in either forward or reverse directions. The anti-tip system subassemblies operate to couple a leading anti-tip wheel to the drive assembly such that pivot motion thereof effects vertical displacement of the leading anti-tip wheel and to decouple a trailing anti-tip wheel from the drive assembly to null pivot motion inputs therefrom. In one embodiment, rheonetic links actively couple and decouple the anti-tip system subassemblies. The system may also include compliant bearings or extensible links for inward displacement of the anti-tip wheel upon impact with a curb.

Abstract: An adjustable seat support assembly for a wheelchair. The seat support assembly includes a seat bottom frame and a seat back frame. The seat bottom frame has at least two spaced apart beams. Each beam includes at least one channel that extends along at least a portion of the beam. Preferably the channel extends along the entire length of the beam. A seat plate is mounted to and extends between the beams. The seat back frame includes two vertical supports. Each support has an upper end and a lower end. At least one back frame cross-bar is attached to and extends between the vertical supports. A mounting bracket is attached to the lower end of each support and removably attached to a channel in one of the beams. Preferably there are two or more channels formed in each beam, one channel in the bottom and the other in the side.

Abstract: A variable stiffness suspension system is provided for a wheelchair. The wheelchair has a frame and at least one wheel coupled to the frame for generally vertical movement relative to the frame. At least one sensor is provided for sensing an operating condition of the wheelchair. A controller is operatively coupled to the sensor. A controllable damper having a variable stiffness is coupled to the controller, the wheel and to the frame. The controllable damper is responsive to the controller and provides a force capable of being varied in a continuous manner. The force is resistive to movement of the wheel. The controllable damper is preferably a commercially available magneto-rheological damper or a variable orifice fluid damper. The controllable damper may be either a linear damper or a rotary brake.

Abstract: An adjustable seat support assembly for a wheelchair. The seat support assembly includes a seat bottom frame and a seat back frame. The seat bottom frame has at least two spaced apart beams. Each beam includes at least one channel that extends along at least a portion of the beam. Preferably the channel extends along the entire length of the beam. A seat plate is mounted to and extends between the beams. The seat back frame includes two vertical supports. Each support has an upper end and a lower end. At least one back frame cross-bar is attached to and extends between the vertical supports. A mounting bracket is attached to the lower end of each support and removably attached to a channel in one of the beams. Preferably there are two or more channels formed in each beam, one channel in the bottom and the other in the side.