Balanced valve assembly for the oil port of a pressure vessel

Claim 1

A CLOSURE ASSEMBLY FOR CONTROLLING THE FLOW OF FLUID FROM A PRESSURE VESSEL, SAID CLOSURE ASSEMBLY HAVING AN INLET COMPRISING A VALVE SEAT AND AN OUTLET, A MAIN FLUID PASSAGEWAY LEADING FROM SAID INLET TO SAID OUTLET, A VALVE STEM SLIDABLY MOUNTED IN SAID CLOSURE ASSEMBLY, A VALVE HEAD AT ONE END OF THE VALVE STEM AND MOVABLE AGAINST SAID SEAT COMPLETELY TO CLOSE THE LATTER, SAID STEM EXTENDING AXIALLY OF SAID VALVE HEAD AND HAVING AN AXIAL BORE THERETHROUGH, RELATIVELY WEAK RESILIENT MEANS NORMALLY URGING SAID VALVE HEAD TO OPEN POSITION, A BALANCING CHAMBER IN SAID CLOSURE ASSEMBLY ASSOCIATED WITH THE INNER END OF SAID VALVE STEM REMOTE FROM THE ROOT END THEREOF, SAID INNER END EXTENDING INTO SAID BALANCING CHAMBER, WHEREBY SAID AXIAL BORE LEADS INTO SAID BALANCING CHAMBER, A SECOND FLUID PASSAGEWAY IN COMMUNICATION AT ONE END WITH SAID AXIAL BORE IN SAID VALVE STEM AND HAVING ITS OTHER END ADJACENT THE ROOT END OF SAID VALVE STEM, LOCATED AT A REGION WHERE THE KINETIC ENERGY WILL BE BEST CARRIED OFF, SAID SECOND FLUID PASSAGEWAY AND SAID AXIAL BORE DEFINING A NORMALLY OPEN CHANNEL LEADING TO SAID BALANCING CHAMBER, WHEREBY WHEN SAID VALVE HEAD IS SPACED FROM SAID VALVE SEAT A PORTION OF THE FLUID FLOWING PAST SAID VALVE HEAD INTO SAID INLET AND THROUGH SAID MAIN FLUID PASSAGEWAY, WILL BE CHANNELED THROUGH SAID OTHER END OF SAID SECOND PASSAGEWAY INTO THE AXIAL BORE AND THROUGH THE LATTER INTO SAID BALANCING CHAMBER TO REACT AGAINST THE INNER END OF SAID STEM IN SAID CHAMBER TO PROVIDE A FORCE OPERATIVELY REACTING AGAINST THE VALVE HEAD TO URGE THE LATTER TO OPEN POSITION.