Fluid flow control valves

Claim 1

A FLUID FLOW CONTROL VALVE INCLUDING A CONDUIT, AN INLET VALVE IN THE CONDUIT, RESILIENT MEANS URGING THE VALVE TO A NORMALLY CLOSED POSITION, A SECOND VALVE IN THE CONDUIT RESILIENTLY LOADED TO A NORMALLY CLOSED POSITION, THE SECOND VALVE BEING POSITIONED DOWNSTREAM OF THE INLET VALVE, AN AUXILIARY CHAMBER FOR PRESSURE FLUID, A MOVABLE MEMBER IN SAID CHAMBER DIVIDING THE CHAMBER INTO FIRST AND SECOND SUB-CHAMBERS, THE MOVABLE MEMBER BEING OPERATIVELY CONNECTED WITH THE SECOND VALVE SO THAT PRESSURE FLUID IN THE FIRST SUB-CHAMBER TENDS TO CLOSE THE VALVE WHILE PRESSURE IN THE SECOND SUB-CHAMBER TENDS TO OPEN THE VALVE, A FIRST DUCT CONNECTING THE FIRST SUB-CHAMBER TO SAID CONDUIT AT A POINT DOWNSTREAM OF THE OUTLET VALVE, A SECOND DUCT CONNECTING THE SECOND SUB-CHAMBER TO SAID CONDUIT AT A POINT BETWEEN THE INLET AND SECOND VALVE, MEANS MAINTAINING A REFERENCE PRESSURE IN THE FIRST SUBCHAMBER, AND A CONTROL VALVE RESPONSIVE TO THE PRESSURE DOWNSTREAM OF THE SECOND VALVE FOR EQUALISING FLUID PRESSURE UPSTREAM AND DOWNSTREAM OF THE INLET VALVE, SAID CONTROL VALVE BEING ACTUATED TO EQUALISE SAID PRESSURES WHEN THE FLUID PRESSURE DOWNSTREAM OF THE SECOND VALVE ATTAINS A PREDETERMINED VALUE.