Autoclosing flow-control valve

An autoclosing flow-control valve assembly comprising:

• a housing forming an inlet chamber normally filled with a fluid under pressure, an outlet chamber, and a main valve seat between the chambers;
• a piston defining in the housing a control chamber;
• a valve element carried on the piston and engageable with the seat, the piston and valve element being displaceable in the housing between a closed position with the element engaging the seat and blocking flow between the chambers and an open position with the element clear of the seat and permitting flow from the inlet chamber to the outlet chamber;
• a piston spring braced between the piston and the housing and urging the piston and element backward into the closed position, the control chamber being of substantially smaller volume in the closed position than in the open position, the piston being formed with a small bleed passage extending between the control chamber and the outlet chamber;
• means including a control passage extending between the inlet chamber and the control chamber and a pilot valve in the control passage for, in an open position of the pilot valve, pressurizing the control chamber and pushing the piston and element into the open position and, in a closed position of the pilot valve, for blocking flow through the control passage;
• an actuating member axially movable on the housing and actuatable to open the pilot valve;
• an actuating spring braced between the member and the housing and urging the member out of contact with the pilot valve;
• a bypass passage extending between the control chamber and the outlet chamber and of substantially greater flow cross section than the bleed passage;
• and
• a bypass valve in the bypass passage normally blocking flow therethrough and openable by actuation of the actuating member to permit flow through the bypass passage, whereby when the actuating member is actuated with the control chamber full the control chamber can be quickly drained and the valve element and piston moved by the spring into the closed position.