| 摘要 |
A liquid dispensing vessel having an air space above the liquid near the top of the vessel has a fluid pump with a suction inlet and a pressure outlet. The pump is operable in a first mode to pump liquid and in a second mode to pump air. There is a first conduit coupling the suction inlet and liquid near the bottom of the vessel, a second conduit coupling the suction inlet and the air space above the liquid near the top of the vessel, a third conduit coupling the pressure outlet to a dispensing device, and a fourth conduit coupling the pressure outlet to liquid near the bottom of the vessel. A valving arrangement is effective to block both the second and fourth conduits for operating the pump in the first mode, and to open the second and fourth conduits for operating the pump in the second mode. The valving arrangement is preferably formed by valves in the second and fourth conduits and an arrangement which is common to the two valves for contemporaneous opening and closing both valves.
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