Tank filling and draining system and control valve assembly therefor

Claim 1

A CONTROL VALVE ASSEMBLY FOR ADMITTING LIQUID INTO A TANK AND DRAINING LIQUID THEREFROM COMPRISING A VALVE HOUSING HAVING A PASSAGE THERETHROUGH AND A VALVE SEAT; A MAIN VALVE MEMBER MOVABLE IN SAID HOUSING INTO AND OUT OF ENGAGEMENT WITH SAID SEAT TO RESPECTIVELY PREVENT AND PERMIT FLOW OF LIQUID THROUGH SAID PASSAGE; SPRING MEANS BIASING SAID MAIN VALVE MEMBER TOWARD SAID SEAT; SAID MAIN VALVE MEMBER AND HOUSING DEFINING A CHAMBER ON ONE SIDE OF SAID MAIN VALVE MEMBER WHICH HAS RESTRICTED FLUID COMMUNICATION WITH THE OTHER SIDE OF SAID MAIN VALVE MEMBER; AT LEAST TWO PILOT VALVES IN SAID HOUSING EACH COMPRISING A PILOT VALVE MEMBER MOVABLE TO OPEN AND CLOSE A BLEED PASSAGE IN SAID HOUSING LEADING FROM SAID CHAMBER INTO THE TANK; SAID BLEED PASSAGES, WHEN OPENED BY THE RESPECTIVE PILOT VALVE MEMBERS, HAVING AN AGGREGATE AND INDIVIDUAL FLOW CAPACITY EXCEEDING THAT OF THE AFORESAID RESTRICTED FLUID COMMUNICATION WHEREBY LIQUID PRESSURE IN SAID CHAMBER DECREASES WITH RESPECT TO THE LIQUID PRESSURE ACTING ON SAID OTHER SIDE OF SAID MAIN VALVE MEMBER THUS TO OVERCOME THE BIAS OF SAID SPRING MEANS AND TO MOVE SAID MAIN VALVE MEMBER OUT OF ENGAGEMENT WITH SAID SEAT FOR FLOW OF LIQUID INTO THE TANK; AND AT LEAST TWO LEVEL SENSORS OPERATIVE SUCCESSIVELY TO MOVE ONE PILOT VALVE MEMBER TO CLOSE ITS BLEED PASSAGE UPON THE LEVEL OF THE LIQUID IN THE TANK APPROACHING A PREDETERMINED LEVEL WHEREBY LIQUID PRESSURE IN SAID CHAMBER INCREASES SO THAT SAID SPRING MEANS BIASES SAID MAIN VALVE MEMBER PARTWAY TOWARD SIDE SEAT TO DECREASE THE RATE OF FLOW OF LIQUID INTO THE TANK AND THEN TO MOVE THE OTHER PILOT VALVE MEMBER TO CLOSE ITS BLEED PASSAGE UPON THE LEVEL OF LIQUID IN THE TANK REACHING A PREDETERMINED LEVEL WHEREBY FLUID PRESSURES ACTING ON OPPOSITE SIDES OF SAID MAIN VALVE MEMBER ARE EQUALIZED SO THAT SAID SPRING MEANS BIASES SAID MAIN VALVE MEMBER INTO ENGAGEMENT WITH SAID SEAT TO DISCONTINUE FLOW OF LIQUID INTO THE TANK.