Pressure differential safety interlock system

Claim 1

APPARATUS FOR PNEUMATIC EQUAL PRESSURE CHANGE-OVER PROTECTION ON A MULTIPLE POSITION COCK OF THE TYPE UTILIZED TO CONTROL AN ADJUSTING DEVICE, SAID APARATUS INCLUDING A PLURALITY OF CONTROL VALVES, A MULTIPLE POSITION COCK HAVING A ROTARY MEMBER SELECTIVELY POSITIONABLE TO SUPPLY FLUID UNDER PRESSURE TO AN ADJUSTING DEVICE, MEANS FOR PREVENTING ROTATION OF SAID ROTARY MEMBER INCLUDING LOCKING CYLINDER MEANS HAVING A PISTON SLIDABLY MOUNTED THEREIN, PISTON STEM MEANS EXTENDING FROM SAID PISTON TO SAID ROTARY MEMBER OF SAID MULTIPLE POSITION COCK, SAID PISTON FORMING WITHIN SAID CYLINDER A PRESSURE CHAMBER ADAPTED TO BE SELECTIVELY SUPPLIED WITH FLUID UNDER PRESSURE OR VENTED TO ATMOSPHERE, SAID PISTON STEM BEING OPERABLY POSITIONED IN ROTATION PREVENTING ENGAGEMENT WITH SAID ROTARY MEMBER OF SAID MULTIPLE POSITION COCK WHEN SAID PRESSURE CHAMBER OF SAID LOCKING CYLINDER MEANS IS VENTED TO ATMOSPHERE AND OPERABLY POSITIONED OUT OF ENGAGEMENT WITH SAID ROTARY MEMBER OF SAID MULTIPLE POSITION COCK WHEN SAID PRESSURE CHAMBER OF SAID LOCKING CYLINDER MEANS IS SUPPLIED WITH FLUID UNDER PRESSURE, AND A PRESSURE DIFFERENTIAL OPERATED VALVE MEANS HAVING A DIAPHRAGM MEANS SUBJECT ON ONE SIDE THEREOF TO A FLUID PRESSURE SUPPLIED BY ONE OF SAID CONTROL VALVES AND SUBJECT ON THE OTHER SIDE THEREOF TO A FLUID PRESSURE SUPPLIED BY ANOTHER OF SAID CONTROL VALVES, SAID PRESSURE DIFFERENTIAL OPERATED VALVE MEANS OPERABLY RESPONSIVE TO SIMULTANEOUS SUPPLY OF FLUID UNDER EQUAL PRESSURES FROM EACH OF SAID CONTROL VALVES TO SUPPLY FLUID UNDER PRESSURE TO SAID PRESSURE CHAMBER OF SAID LOCKING CYLINDER MEANS, AND OPERABLY RESPONSIVE TO SIMULTANEOUS SUPPLY OF FLUID UNDER UNEQUAL PRESSURES FROM EACH OF SAID CONTROL VALVES TO EFFECT VENTING OF SAID PRESSURE CHAMBER OF SAID LOCKING CYLINDER MEANS.