Wheel chair for operation on ground and stairs selectively

Claim 1

A CHAIR COMPRISING A RIGID MAIN FRAME, SIDE FRAMES CONNECTED THERETO FOR MOVEMENT LATERALLY OF THE MAIN FRAME RELATIVE TO THE MAIN FRAME AND TO EACH OTHER TO EXTENDED AND RETRACTED POSITONS; ROTATABLE SUPPORTING MEANS CONNECTED TO THE SIDE FRAMES, RESPECTIVELY, IN LOAD BEARING RELATION TO THE SIDE FRAMES AND FOR ROTATION ABOUT AXES EXTENDING TRANSVERSELY OF THE FRAMES; MEANS OPERABLE FOR ROTATING THE ROTATABLE SUPPORTING MEANS, RESPECTIVELY; MEANS TO MOVE THE SIDE FRAMES TO SAID POSITIONS SELECTIVELY, SAID LAST MENTIONED MEANS INCLUDING REVERSIBLE TOGGLE MEANS DRIVINGLY CONNECTED TO THE SIDE FRAMES AND OPERABLE TO MOVE THE SIDE FRAMES TOWARD EXTENDED AND RETRACTED POSITIONS WHEN THE TOGGLE MEANS ARE DRIVEN IN OPPOSITE DIRECTIONS, RESPECTIVELY; A DEAD CENTER SPRING DRIVINGLY CONNECTED TO THE TOGGLE MEANS, AND MANUAL MEANS TO SHIFT THE SPRING FROM ONE SIDE OF DEAD CENTER POSITION TO THE OPPOSITE SIDE OF DEAD CENTER POSITION, SELECTIVELY, AND THEREBY TO YEILDABLY DRIVE THE TOGGLE MEANS BY THE SPRING IN SAID OPPOSITE DIRECTIONS, RESPECTIVELY.