| 摘要 |
An engine driven impeller type pump for draining water from a plurality of well points is primed by an engine driven oil filled vacuum pump which is connected to the top of a vacuum chamber mounted on the impeller pump housing. A normally open solenoid valve located between the vacuum chamber and vacuum pump is controlled by an electrical control system to prevent water overflow from the vacuum chamber into the vacuum pump. The electrical control system includes low level and high level probes which are located near the lower and upper ends, respectively, of the vacuum chamber, and which are connected in first and second oscillator circuits, respectively. The oscillator circuits are connected to a logic circuit and the latter is connected to a drive circuit which operates the solenoid valve. When the water level in the vacuum chamber rises to the high level probe, the normally open solenoid valve closes and remains closed until the water level recedes below the low level probe.
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