Vent valve device

Claim 1

A VENT VALVE DEVICE COMPRISING: (A) A CASING HAVING A CONTROL CHAMBER COMMUNICABLE WITH A PRESSURE CONTROLLED CONDUIT VIA WHICH FLUID UNDER PRESSURE MAY BE APPLIED THERETO TO CHARGE SAID CONTROL CHAMBER AND VIA WHICH FLUID PRESSURE MAY BE RELEASED TO REDUCE THE PRESSURE IN SAID CONTROL CHAMBER, (B) SAID CASING HAVING A BALANCING CHAMBER, (C) THROTTLING MEANS CONNECTING SAID CHAMBERS FOR CHARGING SAID BALANCING CHAMBER WITH PRESSURIZED FLUID FROM SAID CONTROL CHAMBER, (D) MOVABLE ABUTMENT MEANS SUBJECT TO OPPOSING PRESSURE FROM SAID CONTROL CHAMBER AND SAID BALANCING CHAMBER FOR MOVEMENT IN EITHER OF OPPOSITE DIRECTIONS, (E) A NORMALLY SEATED VALVE OPERATIVELY CONNECTED TO SAID MOVABLE ABUTMENT MEANS AND UNSEATED IN RESPONSE TO MOVEMENT OF SAID MOVABLE ABUTMENT MEANS UPON THE OCCURRENCE OF A REDUCTION IN PRESSURE IN SAID CONTROL CHAMBER AT A RATE ABOVE A CERTAIN RATE TO EFFECT RAPID VENTING TO ATMOSPHERE OF FLUID UNDER PRESSURE FROM SAID CONTROL CHAMBER AND SUCH PRESSURE CONTROLLED CONDUIT, AND (F) VALVE MEANS COMPRISING COOPERATING MEMBERS ON SAID MOVABLE ABUTMENT MEANS AND SAID CASING FOR OPENING A RESTRICTED PASSAGEWAY BETWEEN SAID BALANCING CHAMBER AND SAID CONTROL CHAMBER UPON MOVEMENT OF SAID MOVABLE ABUTMENT MEANS IN RESPONSE TO THE DIFFERENTIAL OF OPPOSING PRESSURES THEREON RESULTING FROM THE OCCURRENCE OF A REDUCTION IN PRESSURE IN SAID CONTROL CHAMBER AT A SUFFICIENT RATE IN RELATION TO THE SIZE OF THE THROTTLING MEANS AND TO CLOSE AND RESTRICTED PASSAGEWAY UPON MOVEMENT OF SAID MOVABLE ABUTMENT MEANS IN A DIRECTION OPPOSITE TO SAID LAST-MENTIONED MOVEMENT IN RESPONSE TO A PREDOMINATING PRESSURE IN SAID CONTROL CHAMBER OVER PRESSURE IN SAID BALANCING CHAMBER, (G) SAID CERTAIN RATE OF PRESSURE REDUCTION IN THE CONTROL CHAMBER BEING AT LEAST A RATE, IN RELATION TO THE COMBINED FLOW CAPACITY OF BOTH THE THROTTLING MEANS AND THE RESTRICTED PASSAGEWAY, AS TO DEVELOP SUFFICIENT DIFFERENTIAL PRESSURES ON SAID MOVABLE ABUTMENT MEANS TO EFFECT UNSEATING OF SAID NORMALLY SEATED VALVE.