| 摘要 |
A dispenser for periodically discharging a metered quantity of a liquid or other flowable medium from an outlet, e.g. into a series of containers successively formed from a surrounding plastic sheath, includes two valves in tandem in a conduit extending from a reservoir to the outlet. A first branch of the conduit, upstream of the first valve, communicates with a pressure accumulator while a second branch, between the two valves, forms a metering chamber provided with a piston whose discharge stroke is initiated by a timer substantially concurrently with the opening of the normally closed second valve and closure of the first valve which reopens upon the succeeding intake stroke. The second valve, adjacent the outlet, is reclosed by the piston toward the end of its discharge stroke. The storage capacity of the pressure accumulator is less than the pumping capacity of the metering piston to avoid extended residence of any liquid in the accumulator.
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