| 摘要 |
The invention is concerned with an improvement in a gas pressure driven pump which comprises a vessel, means for introducing a liquid into the vessel, means for preventing reverse flow of the liquid into the liquid introducing means, means for introducing a pressurized gas to the vessel, and means responsive to a gas pressure increase in the vessel for flowing the liquid out of the vessel. The invention is an improved system for controlling the flow of pressurized gas into the vessel responsive to the liquid level therein, which system is substantially independent of the density of the liquid. More specifically the improved system comprises a valve having a first, a second and a third port, the valve providing a first mode in which the first port is in communication with the second port and a second mode in which the first port is in communication with the third port. The second port communicates in both modes with the surrounding outside atmosphere. A first conduit communicates a bottom portion of the vessel at a first position therein and the first port. A second conduit communicates with a top portion of the vessel at a second position therein. Shift means operate responsive to a gas pressure differential between a pair of chambers on opposite sides of a diaphragm or sliding piston shift the valve from the first mode which corresponds to a substantially zero gas pressure differential to the second mode which corresponds to a non-zero gas pressure differential. A respective one of the chambers is in gas flow communication with the first conduit and a respective other of the chambers is in gas flow communication with the second conduit. A third conduit is provided communicating with a third position within the vessel above the first position and generally intermediate the first and second positions and providing a pressure escape path from the vessel to the valve via the first and second ports when the liquid level in the vessel is below the third position, the escape path closing when the liquid level is above the third position. Further, the improved system includes means which prevent gas flow, when the non-zero gas pressure differential exists and the valve is in the second mode, from a pressurized gas source to the lower pressured side of the diaphragm.
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