A hydraulic diaphragm valve comprising a housing, an inlet, an outlet, a diaphragm valve seating between the inlet and the outlet, a sealing diaphragm mounted in the housing and displaceable about the diaphragm valve seating, so as to close and open a flow path between the inlet and outlet, a valve control chamber and a command valve comprising a first duct communicating a one end thereof with the valve inlet, and at an opposite end thereof with a first command valve seating, a second duct communicating into one end with the valve outlet, and at an opposite end thereof, with a second command valve seating. A third duct communicates at one end with the valve control chamber and at its opposite end it selectively communicates with the first and second command valve seatings. A flexible command diaphragm is selectively biased into sealing engagement with one or other of the command valve seatings to effect communication between the third duct and the command valve seating not in seating engagement with the command diaphragm.
CROSS REFERENCE TO RELATED APPLICATION
This application is a continuation-in-part of U.S. application Ser. No. 08/567,073, filed Dec. 4, 1995, now abandoned for which the most recent Continued Prosecution Application was filed Aug. 12, 1999, which in turn is a continuation-in-part of U.S. application Ser. No. 215,282, filed on Mar. 21, 1994, now abandoned.
In a pilot-operated valve having a valve body, including inlet and outlet portions controllably interconnected via a main piston bore portion; a main piston movable within the main piston bore; an operator portion; an operator assembly including a movable plunger assembly; and an actuating mechanism for actuating the plunger assembly, wherein the improvement comprises a further bore located within the valve body and a manually-operated override assembly retained therein, including a stem having a tool actuating portion; a cam portion extending radially into the operator bore portion and, upon a first predetermined rotation physically actuating the plunger assembly; and an actuating surface extending tangentially into the main piston bore portion which, upon a second rotation physically actuates the main piston. A method of actuating the manual override assembly is also set forth.
