| 摘要 |
A pump shutoff device is provided wherein compressed air supplied to the air inlet port of the over speed control device enters an air pressure chamber, and then proceeds to an adjacent air exhaust chamber. From there, the air passes to an outport which is connected,directly to the inlet port of the air motor of an air-operated piston pump spool located inside the body of the device, is shaped such that the valve spool functions to allow passage of air freely from the air pressure chamber to the air exhaust chamber. Compressed air is connected through a series of unrestricted conduits,ports and chambers continuous from the compressed air supply to the air motor of a pump. The air motor is energized by compressed air to provide continuous pumping. Positive pressure existing in the fluid pressure chamber exerts an axial thrust on the spool. Adjacent to the air chambers and opposite the position of the fluid pressure chamber is a coil compression spring. The spool and the spring are shaped so as the spring is compressed it exerts an axial force on the spool in opposition to the axial force on the spool exerted by the fluid pressure chamber
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