Seat positioning and control system

1. A positioning and control system to selectively position and to monitor and record the position of a seat frame, back rest frame and leg rest supports mounted on a carriage assembly of a powered wheelchair comprising a seat positioning mechanism including a seat tilt positioning assembly and a back rest recline positioning assembly to position the tilt of the seat frame and the recline of the back rest frame respectively, and a leg rest positioning mechanism including leg rest positioning assemblies to position the leg rest supports, and a system control including an operator input control and a microprocessor to control, monitor and record the position of the seat frame, back rest frame and the leg rest supports, said carriage assembly comprises a carriage frame including a pair of side carriage frame members held in fixed spaced relationship relative to each other by a front carriage frame member and rear carriage frame member respectively having a carriage compartment mounted on the carriage frame to operatively receive and support a portion of the system control, a wheelchair drive means and a power source, said carriage assembly is supported on the ground, floor or other support surface by a front carriage support and a rear carriage support coupled to the front and rear portions of the carriage frame respectively, said seat tilt positioning assembly comprises a tilt actuator including an actuator sleeve pivotally coupled to the seat frame and a tilt actuator member reciprocally disposed therein and movable between a retracted position and an extended position by a tilt motor pivotally coupled to the front carriage frame member of the carriage frame, a pair of tilt link or seat frame positioning members pivotally coupled at opposite end portions thereof to the seat frame of the front carriage frame member of the carriage frame and a seat frame slide assembly on opposite sides of the seat frame and the carriage assembly including a guide plate having an elongated slot formed therethrough affixed to opposite side portions of the seat side frame member of the seat frame to receive a corresponding pivot protrusions or pins on the carriage frame, such that the position of the seat relative to the carriage is determined by a position sensor and said seat frame is tilted by said tilt actuator operated to either extend or retract the tilt actuator member relative to the tilt actuator sleeve to either push or pull the seat frame rearward or forward relative to the carriage assembly along the seat frame slide assemblies such that the tilt link or seat frame positioning members either rotate the seat frame down or up relative to the carriage assembly about the pivots, said back rest recline positioning assembly comprises a recline actuator including an actuator sleeve pivotally coupled to the carriage frame and a recline shaft or actuator member reciprocally disposed therein and movable between a retracted and an extended position by a recline motor pivotally coupled to the upper back rest frame member of the back rest frame, a recline link or back rest frame position member pivotally coupled at opposite end portions to the seat frame and to the upper back rest frame member by a coupling member whereby to change the recline position of back rest frame the recline actuator is operated to either extend or retract the recline shaft or actuator member relative to the recline actuator sleeve to either push or pull the recline link or back rest frame position member and coupling member to rotate the back rest frame relative to the seat frame about the pivots to raise or lower the back rest frame such that the position of the back rest relative to the carriage is determined by a position sensor, and each said leg rest positioning assembly comprises a leg rest actuator including an actuator sleeve coupled to the seat frame and a leg rest shaft or actuator member reciprocally disposed therein and movable between a retracted and an extended position by a leg rest motor pivotally to the leg rest member by the leg rest member linkage whereby to raise or lower either leg rest support relative to the seat frame, the corresponding leg rest actuator is operated to either extend or retract the leg rest shaft or actuator member relative to the leg rest sleeve to either push or pull the corresponding leg support to pivot the leg rest member about pivots and to raise or lower the corresponding leg rest support, said positioning and repositioning of the seat tilt positioning assembly, said back rest recline positioning assembly and said leg rest positioning assemblies relative to the carriage assembly and to each other cooperatively act as a pressure relief seating system by selectively shifting the occupant's weight by positioning of the occupant's body and limbs to rest in the powered wheelchair.

2. The positioning and control system of claim 1 wherein said back rest recline positioning assembly further comprises a back rest shear reduction assembly to reduce the shear forces exerted on the occupant of the powered wheelchair during movement of the back rest frame relative to seat frame comprising a slide member affixed to each side back frame member to operatively support in sliding engagement an upper and lower back cushion slide attachment or mount respectively to support a back rest cushion and a shear reduction link or back rest cushion positioning member pivotally coupled at opposite end portions thereof to the upper back rest frame member and the back rest cushion by the coupling member and a back rest attachment respectively such that the recline shaft or actuator member is either extended or retracted the coupling member pivots about pivot pulling or pushing the shear reduction link or back rest cushion positioning member and the back rest attachment moving the upper back cushion slide attachment or mount with the back rest cushion up or down the corresponding slide in mechanical synchronization with the movement of the back rest frame.