Remote control of fluid valves

Claim 1

IN A REMOTE CONTROL SYSTEM FOR A HYDRAULIC VALVE ACTUATOR, SAID SYSTEM HAVING MEANS FOR CONNECTING IT TO A SOURCE OF HYDRAULIC FLUID UNDER PRESSURE AND A REMOTE CONTROL STATION, MEANS COMPRISING A SERVO VALVE MEMBER MOVABLE IN OPPOSITE DIRECTIONS TO CONTROL THE SUPPLY OF HYDRAULIC FLUID UNDER PRESSURE FROM SAID SOURCE TO OPPOSITE SIDES OF SAID ACTUATOR FOR DETERMINING THE POSITION OF SAID ACTUATOR, MECHANICAL MEANS CONNECTED FOR TENDING TO URGE SAID SERVO VALVE MEMBER IN ONE DIRECTION WITH A FORCE WHICH VARIES IN DIRECT PROPORTION TO THE POSITION OF SAID ACTUATOR, HYDRAULIC FLUID PRESSURE MEANS CONNECTED FOR TENDING TO URGE SAID SERVO VALVE MEMBER IN THE OPPOSITE DIRECTION AT A PRESSURE, THE VALUE OF WHICH IS PRESET AT SAID REMOTE CONTROL STATION IN ACCORDANCE WITH THE DESIRED POSITION OF SAID ACTUATOR, FURTHER MEANS OPERABLE WHEN SAID ACTUATOR HAS EITHER REACHED OR DEPARTED FROM A PARTICULAR POSITION, TO OPEN A CIRCUIT THROUGH WHICH HYDRAULIC FLUID SUPPLIED AT SAID PRE-SET PRESSURE CAN LEAK, AND A DEVICE LOCATED AT SAID CONTROL STATION FOR INDICATING THE PRESENCE OF FLUID FLOW IN SAID CIRCUIT.