Patent ID: 8272539

Claim:
A piston pump assembly having a first pump comprising a piston chamber-forming member having a first chamber disposed about a first central axis and having a cylindrical side wall, an axially outer open end of the first chamber being open downwardly, a piston-forming element received in the first chamber axially slidable inwardly and outwardly therein between an outward extended position and an inward retracted position, the piston-forming element having an axially extending stem, a first disc spanning radially between the stem and the first chamber side wall preventing fluid flow outwardly there past, a passageway through the stem providing communication from inside the first chamber outwardly past the first disc through the outer open end of the first chamber, the passageway opening at an outer opening in the first chamber and at an outlet outwardly of the first disc, the passageway having a central passageway portion and an inlet passageway portion, the central passageway portion extending through the stem along the central axis, the central portion passageway extending inwardly from the outlet along the central axis to an inner end disposed at a height above the outlet, the inlet passageway portion extending through the stem along an inlet axis which extends radially outwardly and axially outwardly relative the central axis, the inlet passageway portion opening into the central passageway portion at an inner opening proximate the inner end, the inlet passageway portion extending from the inner opening downwardly through the stem about the inlet axis to the outer opening the outer opening disposed at a height below the inner opening, and the outer opening disposed at a height above the outlet.