Tank loading and unloading system for tank vehicles

Claim 1

IN APPARATUS FOR CONTROLLING THE FILLING AND DRAINING OF LIQUID IN A TANK THROUGH NORMALLY CLOSED EXTERNAL SUPPLY AND DRAIN CONDUITS, THE COMBINATION COMPRISING MEANS HAVING AN INLET-OUTLET PASSAGE THROUGH WHICH LIQUID IS SUPPLIED TO AND DRAINED FROM SAID TANK, A HOLLOW VALVE BODY OVERLYING SAID PASSAGE, AN ASSEMBLY INCLUDING A MAIN VALVE NORMALLY CLOSING SAID INLET-OUTLET PASSAGE, AND A PISTON IN SAID BODY MOVABLE WITH SAID MAIN VALVE AND DEFINING WITH SAID BODY A CHAMBER OVER SAID PISTON, MEANS BIASING SAID MAIN VALVE AND YIELDABLY HOLDING THE SAME IN CLOSED POSITION, SAID MAIN VALVE BEING MOVABLE FOR OPENING SAID INLET-OUTLET PASSAGE AND SAID PISTON BEING MOVABLE IN SAID BODY, AGAINST THE INFLUENCE OF SAID BIAS, BY SUPPLY LIQUID ENTERING THE TANK THROUGH SAID INLET-OUTLET PASSAGE, MEANS PROVIDING AN INLET PASSAGE LEADING TO SAID CHAMBER FROM THE INLET-OUTLET PASSAGE OF SAID MAIN VALVE, MEANS PROVIDING AN OUTLET PASSAGE LEADING FROM SAID CHAMBER TO THE INTERIOR OF THE TANK, A LIQUID CONTROLLED VALVE IN SAID OUTLET PASSAGE OPEN TO PERMIT MAXIMUM FLOW THROUGH SAID OUTLET PASSAGE, SAID LIQUID CONTROLLED VALVE BEING RESPONSIVE TO LIQUID LEVEL IN THE TANK FOR CLOSING, THEREBY TO SHUT OFF FLOW THROUGH SAID OUTLET PAS-