Patent ID: 7267251

Claim:
A pump for dispensing liquids from a reservoir, comprising: a piston-chamber forming member having a cylindrical inner chamber and a cylindrical outer chamber, the inner chamber and outer chamber each having a diameter, a chamber wall, an inner end and an outer end, the inner end of the inner chamber in fluid communication with a reservoir, the diameter of the inner chamber being less than the diameter of the outer chamber, the inner chamber and outer chamber being coaxial with the outer end of the inner chamber opening into the inner end of the outer chamber, a one-way valve between the reservoir and the inner chamber permitting fluid flow through the inner end of said inner chamber only from the reservoir to the inner chamber; a piston forming element received in the piston-chamber forming member axially slidable inwardly and outwardly therein, said piston forming element being generally circular in cross-section with a central axially extending hollow stem having a outlet passageway closed at an inner end and having an outlet proximate an outer end, a circular flexing disc extending radially outwardly from the stem proximate an inner end of the stem, the flexing disc having an elastically deformable edge portion proximate the chamber wall of the inner chamber circumferentially thereabout, a circular sealing disc extending radially outwardly from the stem spaced axially outwardly from the flexing disc, the sealing disc engaging the chamber wall of the outer chamber circumferentially thereabout to form a substantially fluid impermeable seal therewith on sliding of said piston forming element inwardly and outwardly, an inlet located on the stem between the flexing disc and sealing disc in communication with the outlet passageway, the piston forming element slidably received in the piston-chamber forming member for reciprocal axial inward and outward movement therein with the flexing disc in the inner chamber and sealing disc in the outer chamber, the flexing disc substantially preventing fluid flow in the inner chamber past the flexing disc in an inward direction, the flexing disc elastically deforming away from the chamber wall of the inner chamber to permit fluid flow in the inner chamber past the flexing disc outwardly.