Two-piece foam piston pump

A pump for dispensing liquid from a reservoir comprising:

• a piston chamber-forming member having a cylindrical inner chamber, a cylindrical intermediate chamber and a cylindrical outer chamber, the inner chamber, intermediate chamber and outer chamber each having a diameter, a chamber wall, an inner end and an outer end,
• the diameter of the inner chamber being different than the diameter of the intermediate chamber, the diameter of the intermediate chamber being equal to or different than the diameter of the outer chamber,
• the inner chamber and the intermediate chamber being coaxial with the outer end of the inner chamber opening into the intermediate chamber, the intermediate chamber and the outer chamber being coaxial with the outer end of the intermediate chamber opening into the outer chamber,
• the inner end of the inner chamber in fluid communication with the reservoir,
• a piston-forming element received in the piston chamber-forming member axially slidable inwardly and outwardly therein,
• said piston-forming element being generally cylindrical in cross-section with a central axially extending stem having an inner end and an outer end,
• a fluid passageway axially through the stem from a fluid outlet at the outer end of the stem to a fluid inlet duct axially inwardly from the fluid outlet,
• an inner flexing disc extending radially outwardly from the stem between the inner end and the outer end of the piston-forming element,
• the inner flexing disc having an elastically deformable edge portion proximate the chamber wall of the inner chamber circumferentially thereabout,
• an outer flexing disc extending radially outwardly from the stem spaced axially outwardly from the inner flexing disc,
• the outer flexing disc having an elastically deformable edge portion proximate the chamber wall of the intermediate chamber circumferentially thereabout,
• a sealing disc extending radially outwardly from the stem spaced axially outwardly from the outer flexing disc,
• the sealing disc engaging the chamber wall of the outer chamber circumferentially thereabout to prevent fluid flow in the outer chamber past the sealing disc in an outward direction therewith on sliding of said piston-forming element inwardly and outwardly,
• the fluid inlet duct is located on the stem between the outer flexing disc and the sealing disc,
• the piston-forming element slidably received in the piston chamber-forming member for reciprocal axial inward and outward movement therein with the inner flexing disc in the inner chamber, the outer flexing disc in the intermediate chamber and the sealing disc in the outer chamber,
• the inner flexing disc substantially preventing fluid flow in the inner chamber past the inner flexing disc in an inward direction,
• the outer flexing disc substantially preventing fluid flow in the intermediate chamber past the outer flexing disc the inward direction,
• the deformable edge portion of the inner flexing disc elastically deforming away from the chamber wall of the inner chamber to permit fluid flow in the inner chamber past the inner flexing disc in the outward direction,
• the deformable edge portion of the outer flexing disc elastically deforming away from the chamber wall of the intermediate chamber to permit fluid flow in the intermediate chamber past the outer flexing disc in the outward direction,
• wherein with reciprocal sliding of the piston-forming element within the piston chamber-forming member fluid from the reservoir is drawn from the reservoir past the inner flexing disc to between the inner flexing disc and the outer flexing disc, and is discharged from between the inner flexing disc and the outer flexing disc past the outer flexing disc to between the outer flexing disc and the sealing disc and via the fluid inlet duct into the fluid passageway and out the fluid outlet, characterized by:
• an air passageway through the piston-forming element from an air vent outlet on the piston-forming element in communication with the reservoir axially inwardly of the inner flexing disc,
• the air passageway including passage portions extending through the piston-forming element within the stem of the piston-forming member axially past the inner flexing disc and the outer flexing disc and axially past the sealing disc to an air inlet port on the stem of the piston-forming element axially outwardly of the sealing disc, the air inlet port in communication with atmospheric air of the atmosphere,
• a one-way air vent valve preventing air and fluid flow through the air passageway from the reservoir to the atmosphere, and permitting fluid flow through the air passageway from the atmosphere to the reservoir when atmospheric pressure of the atmosphere is greater than a pressure in the reservoir by a pressure differential greater than a threshold pressure.