| 摘要 |
A liquid dispensing pump includes a one-piece piston capable of not only effecting a pumping operation but also an outlet valve opening and closing function upon limited relative axial movement. In one embodiment, the piston reciprocates and forms a valve seat for a container vent opening extending through a closure cap provided on the pump body, and in another embodiment, the pump cylinder reciprocates and forms a valve seat for opening and closing the container vent opening. The pump chamber defined by the cylinder has a valved inlet which may be formed by a sleeve depending from the piston and an upstanding conduit in the cylinder or may be formed by a ball check valve in the cylinder.
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