Patent ID: 8827119

Claim:
A refill unit for a liquid dispenser comprising: a container for holding a liquid; and a post seal pump; the post seal pump comprising a housing; the housing secured to the container; a post secured to the housing; a post seal on the post; the housing having a pump chamber; a base at one end of the pump chamber; an aperture through the base; a shaft seal secured to the housing and located proximate the aperture in the base; a hollow piston shaft having a first end that fits over the post and engages the post seal and a second end that reciprocates within the aperture; a fluid outlet located proximate the second end of the hollow piston shaft; a piston located at an intermediary position on the shaft; one or more apertures through the piston shaft located between the piston and the fluid outlet; wherein when the piston shaft is in a first position, fluid flows into the pump chamber and the one or more apertures through the piston shaft are sealed off by the post seal; and wherein when the piston shaft is in a second position, the piston engages a wall of the pump chamber and the one or more apertures provide a fluid path from the pump chamber to the interior of the hollow piston shaft.