Pressure balanced valve

Claim 1

A VALVE CONSTRUCTION COMPRISING A BODY HAVING INLET AND OUTLET PASSAGES CONNECTED TO A CENTRAL CAVITY, A BORE CONNECTING SAID CAVITY TO THE EXTERIOR OF SAID BODY, MEANS PROVIDING A VALVE SEAT BETWEEN SAID INLET AND SAID OUTLET FLOW PASSAGES AND A FLOW PORT BETWEEN SAID VALVE SEAT AND SAID OUTLET PASSAGE, SAID FLOW PORT BEING SUBSTANTIALLY SMALLER THAN SAID VALVE SEAT AND THERE BEING A FLOW CHAMBER BETWEEN SAID VALVE SEAT AND SAID FLOW PORT OF SUBSTANTIALLY LARGER CROSS-SECTION THAN THE CROSS-SECTION OF SAID FLOW PORT, A VALVE CLOSURE MEMBER MOUNTED FOR MOVEMENT BETWEEN OPEN AND CLOSED POSITIONS WITHIN SAID VALVE BODY AND HAVING A SEATING SURFACE ADAPTED TO SEALINGLY ENGAGE SAID VALVE SEAT WHEN SAID VALVE IS CLOSED, A THROTTLE MEMBER RIGID WITH SAID VALVE CLOSURE MEMBER AND EXTENDING FROM ONE END OF SAID CLOSURE MEMBER INTO SAID FLOW PORT AND SPACED FROM AND IN CLOSE CLEARANCE RELATION WITH SAID FLOW PORT WHEN SAID VALVE IS CLOSED AND BEING DISPLACED OUT OF SAID FLOW PORT WHEN SAID VALVE IS OPEN, A POWER ACTUATOR CONNECTED TO MOVE SAID VALVE CLOSURE MEMBER BETWEEN OPEN AND CLOSED POSITIONS, FLUID SEALS FORMING A SEALED PRESSURE CHAMBER AT THE END OF SAID VALVE CLOSURE MEMBER REMOTE FROM SAID THROTTLE MEMBER, PASSAGE MEANS EXTENDING THROUGH SAID VALVE CLOSURE MEMBER, SAID PASSAGE MEANS HAVING AN OPENING AT ONE END IN SAID PRESSURE CHAMBER AND HAVING AN OPENING AT ITS OPPOSITE END IN THE REGION OF SAID CLOSURE MEMBER BETWEEN SAID SEATING SURFACE AND SAID THROTTLE MEMBER THEREBY CONNECTING SAID PRESSURE CHAMBER TO SAID FLOW CHAMBER BETWEEN SAID VALVE SEAT AND SAID FLOW PORT IN THE VALVE CLOSED POSITION, THE AREA OF SAID VALVE SEAT AND THE AREA ENCLOSED BY SAID FLUID SEALS BEING SUCH THAT WHEN SAID VALVE IS CLOSED SAID VALVE CLOSURE MEMBERR IS ESSENTIALLY BALANCED AGAINST MOVEMENT TOWARD AND AWAY FROM SAID CLOSED POSITION WHEREBY SAID CLOSURE MEMBER MAY BE MOVED BY SAID ACTUATOR TOWARD AND AWAY FROM SAID CLOSED POSITION RAPIDLY, FLUID PASSING THROUGH SAID PASSAGE MEANS INTO AND OUT OF SAID PRESSURE CHAMBER TO ACCELERATE INITIAL OPENING MOVEMENT AND FINAL CLOSING MOVEMENT OF SAID VALVE CLOSURE MEMBER.