Two-piece foam piston pump

A piston pump for dispensing from a discharge outlet a liquid from a reservoir, comprising:

• a piston chamber-forming member disposed about an axis,
• the piston chamber-forming member defining a pump chamber and an inner air chamber, the pump chamber in communication with the reservoir via the inner air chamber, each of the pump chamber and the inner air chamber are coaxial about the axis,
• the inner air chamber extending from an inner end of the pump chamber to an open inner end of the inner air chamber open into the reservoir,
• the inner air chamber defined within an axially extending circumferential inner air chamber wall,
• a piston-forming element,
• the piston-forming element having a hollow axially extending stem,
• the stem having a central passageway through the stem from an axial inner end to the discharge outlet at an axial outer end of the stem, the central passageway open at its axial inner end and at the discharge outlet,
• the stem comprising an outer pump portion for reciprocal coaxial sliding in the pump chamber and an inner portion comprising an air vent tube for reciprocal coaxial sliding in the inner air chamber,
• an inner flexing disc extending radially outwardly from the air vent tube,
• the inner flexing disc having an elastically deformable edge portion proximate the inner air chamber wall circumferentially thereabout,
• the inner flexing disc substantially preventing fluid flow in the inner air chamber past the inner flexing disc in an outward direction,
• the inner flexing disc elastically deforming away from the inner air chamber wall to permit fluid flow in the inner air chamber past the inner flexing disc in an inward direction,
• a sealing disc extending radially outwardly from the air vent tube spaced axially outwardly from the inner flexing disc,
• the sealing disc engaging the inner air chamber wall circumferentially thereabout to prevent fluid flow in the inner air chamber past the sealing disc inwardly and outwardly,
• the stem of the piston-forming element coaxially slidably received in the piston chamber-forming member with the air vent tube in the air inlet chamber and the outer pump portion in the pump chamber of the piston chamber-forming member wherein with reciprocal axial inward and outward movement the outer pump portion cooperates with the pump chamber in a cycle of operation to discharge the liquid from the pump chamber, and to draw the liquid into the pump chamber from the reservoir through the inner air chamber via the central passageway through the inner air chamber,
• an air vent channel extending through the piston chamber-forming member providing communication between the inner air chamber and atmosphere,
• the air vent channel open into the inner air chamber at a location on the inner air chamber wall axially between the inner flexing disc and the sealing disc.