| 摘要 |
A fluid pressure control apparatus having a main valve and a pilot valve for moving the main valve to a shutoff position as a function of the fluid pressure in a supply fluid. The pilot valve is connected to receive supply fluid having a fluid pressure Ps through a first passage. A second passage connected to the first passage communicates supply fluid to a control chamber in the main valve. A first restriction in the second passage limits the fluid pressure of the supply fluid communicated to the control chamber to a fluid pressure Pc. The control chamber is connected to a reservoir having a fluid pressure Pr through a third passage having a second restriction therein to control the flow of fluid from the control chamber. A first piston located in the main valve is responsive to a pressure differential between the fluid in the control chamber and supply fluid presented to an outlet chamber to control the flow of supply fluid as a fluid pressure Pc to a system from the main valve. In response to an operational input signal supplied to a solenoid associated with the pilot valve, a second piston moves to initiate communication of supply fluid having a fluid pressure Ps from the first passage directly to the control chamber in the main valve. As the fluid pressure in the control chamber changes from Pc to Ps, the pressure differential is eliminated and the first piston closes as a force differential is reversed to immediately terminate the flow of supply fluid to the system.
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