Turntable mechanism

Claim 1

APPARATUS FOR ROTATABLY SUPPORTING A LOAD ON A PLATFORM, COMPRISING: A TRACK FORMED IN SAID PLATFORM, A CARRIAGE ON SAID TRACK; AN AIR MOUNT HAVING A CHAMBER EXPANSIBLE UPON APPLICATION OF FLUID THERETO SUPPORTED BY SAID CARRIAGE; TURNABLE MOUNTED ON SAID AIR MOUNT IN A POSITION WHEREIN THE TOP SURFACE OF SAID TURNTABLE LIES SUBSTANTIALLY IN THE PLANE OF SAID PLATFORM, SAID TURNTABLE BEING ELEVATED ABOVE THE PLATFORM UPON EXPANSION OF SAID CHAMBER; A DOUBLE ACTING FLUID ACTUATOR INTERCONNECTING SAID PLATFORM AND SAID CARRIAGE, SAID FLUID ACTUATOR BEING ADAPTED TO MOVE SAID CARRIAGE ALONG SAID TRACK; FLUID SUPPLY MEANS CONNECTED TO SAID EXPANSIBLE CHAMBER AND TO SAID FLUID ACTUATOR AND ADAPTED TO BE CONNECTED TO A SOURCE OF FLUID UNDER PRESSURE, SAID SUPPLY MEANS INCLUDING FIRST VALVE MEANS SELECTIVELY OPERABLE TO DIRECT FLUID UNDER PRESSURE TO SAID EXPANSIBLE CHAMBER AND TO ONE END OF SAID ACTUATOR, FIRST BIASING MEANS BIASING SAID FIRST VALVE MEANS IN A POSITION WHEREIN FLUID IS DIRECTED TO SAID CHAMBER, SECOND VALVE MEANS PLACED IN PARALLEL RELATIONSHIP WITH SAID EXPANSIBLE CHAMBER, SECOND BIASING MEANS BIASING SAID SECOND VALVE MEANS INTO A POSITION WHEREIN PASSAGE OF FLUID THERETHROUGH IS BLOCKED, FIRST VALVE POSITIONING MEANS CONNECTED TO SAID FIRST, VALVE MEANS ADAPTED TO OVERCOME SAID FIRST BIASING MEANS, SECOND VALVE POSITIONING MEANS CONNECTED TO SAID SECOND VALVE MEANS ADAPTED TO OVERCOME SAID SECOND BIASING MEANS, SAID SECOND VALVE POSITIONING MEANS BEING RESPONSIVE TO EXPANSION OF SAID CHAMBER TO OVERCOME SAID SECOND BIASING MEANS WHEREBY SAID SECOND VALVE MEANS IS POSITIONED TO DIRECT FLUID UNDER PRESSURE TO SAID FIRST VALVE POSITIONING MEANS AFTER SAID CHAMBER HAS EXPANDED, SAID FIRST POSITIONING MEANS THEREUPON POSITIONING SAID FIRST VALVE MEANS TO DIRECT FLUID UNDER PRESSURE TO ONE OF SAID ACTUATOR AND SIMULTANEOUSLY TO BLOCK PASSAGE OF FLUID TO OR FROM SAID CHAMBER WHEREBY SAID ACTUATOR MOVES SAID CARRIAGE ALONG SAID TRACK AFTER EXPANSION OF SAID CHAMBER, CONTROL VALVE MEANS INCLUDING MEANS TO REVERSE THE SUPPLY OF FLUID UNDER PRESSURE AND THE EXHAUST FOR EXHAUSTING FLUID FROM SAID ONE END OF SAID ACTUATOR AND SIMULTANEOUSLY CONNECTING THE OTHER END OF SAID ACTUATOR TO FLUID UNDER PRESSEURE WHEREBY SAID ACTUATOR RETURNS SAID CARRIAGE ALONG SAID TRACK TO ITS INITIAL POSITION, SAID SECOND VALVE MEANS INCLUDING MEANS TO HOLD SAID FIRST VALVE MEANS IN A POSITION WHEREIN PASSAGE OF FLUID TO AND FROM SAID EXPANSIBLE CHAMBER IS BLOCKED WHILE SAID CARRIAGE IS BEING RETURNED TO ITS INITIAL POSITION, AND SAID CONTROL VALVE MEANS INCLUDING MEANS TO EXHAUST FLUID FROM ALL PORTIONS OF SAID SUPPLY MEANS WHEREUPON SAID FIRST VALVE MEANS IS BIASED BY SAID FIRST BIASING MEANS INTO A POSITION WHEREIN SAID EXPANSIBLE CHAMBER IS CONNECTED TO AN EXHAUST LINE TO PERMIT LOWERING OF THE TURNTABLE AFTER RETURN OF THE CARRIAGE.