Stair-climbing wheel chair

Claim 1

AN OCCUPANT-DRIVEN FOLDABLE STAIR-CLIMBING WHEEL CHAIR ADAPTED TO SAFELY CLIMB STAIRS AND TURN ON THE STAIR LANDINGS COMPRISING: (A) A FOLDABLE CENTRAL CHAIR MEANS FOR SEATING AN OCCUPANT; (B) AN ATTITUDE CONTROL MEANS FOR REGULATING THE ANGLE OF SAID CHAIR MEANS WITH RESPECT TO THE SURFACE SUPPORTING SAID WHEEL CHAIR; (C) A DRIVE WHEEL MOUNTED ON EACH SIDE OF SAID CHAIR MEANS ON A DRIVE WHEEL HUB FOR SUPPORTING THE REAR END OF SAID WHEEL CHAIR, SAID DRIVE WHEEL HUB BEING ROTATABLY MOUNTED ON AN AXLE ATTACHED TO SAID CHAIR MEANS; (D) RETRACTABLE STAIR TRACTION MEANS ROTATABLY MOUNTED ON EACH SIDE OF SAID HAIR MEANS FOR ENGAGING THE STEPS OF THE STAIRS; (E) GRAB MEANS MOUNTED ON EACH SIDE OF SAID CHAIR MEANS FOR GRIPPING BY THE WHEEL CHAIR OCCUPANT AND FOR ROTATING SAID DRIVE WHEELS AND STAIR TRACTION MEANS; (F) A DIFFERENTIAL GEAR MEANS OPERATIVELY CONNECTING THE DRIVE WHEEL, STAIR TRACTION MEANS AND GRAB MEANS ON EACH SIDE OF SAID CHAIR MEANS, SAID DIFFERENTIAL GEAR MEANS ADAPTED TO ROTATE THE DRIVE WHEEL AND STAIR TRACTION MEANS BY ROTATION OF SAID GRAB MEANS TO PERMIT THE STAIR TRACTION MEANS TO OVERRUN THE DRIVE WHEEL AND TO PREVENT THE DRIVE WHEEL FROM OVERRUNNING THE GEAR TRACTION MEANS; (G) A TRANSMISSION GEAR MEANS OPERATIVELY CONNECTING THE GRAB MEANS AND DIFFERENTIAL GEAR MEANS ON EACH SIDE OF SAID CHAIR MEANS, SAID TRANSMISSION GEAR MEANS BEING ADAPTED TO TRANSMIT THE TORQUE EXERTED ON SAID GAB MEANS FOR PERMITTING ROTATION OF SAID AND TO MULTIPLY SAID TORQUE; (H) A CONTROL MEANS OPERATIVELY CONNECTED TO EACH OF SAID GAB MEANS FOR PERMITTING ROTATION OF SAID GAB MEANS TO CAUSE BACKWARD MOTION OF SAID WHEEL CHAIR WHILE PREVENTING ROTATION OF SAID GAB WHEEL TO CAUSE FORWARD MOTION OF SAID SHEEL CHAIR; (I) A FIRST SHIFT MEANS OPERATIVELY CONNECTED TO SAID CONTROL MEANS FOR SELECTIVELY DISENGAGING SAID CONTROL MEANS FOR SAID GRAB MEANS; AND (J) A SECOND SHIFT MEANS OPERATIVELY CONNECTED TO EACH OF SAID TRANSMISSION AND DIFFERENTIAL GEAR MEANS, SAID SHIFT MEANS BEING ADAPTED TO DISENGAGE SELECTIVELY SAID TRANSMISSION GEAR MEANS AND TO LOCK SELECTIVELY EACH OF SAID GRAB MEANS DIRECTLY TO ITS CORRESPONDING DRIVE WHEEL AND STAIR TRACTION MEANS.