Air vent check valve

Claim 1

In a hand pump adapted for pumping a liquid from a flexible container, said pump including an elongated, axially reciprocal plunger, a head mounted on the outermost end of said plunger having a normally depending skirt extending along the length of said plunger, a stationary collar including a normally upwardly extending enclosed wall portion, said wall portion being configured to telescopically receive said skirt upon depression of said plunger, with a vent opening remaining for passage of air between the skirt and wall portion, said vent opening forming a part of the air intake passageway for the pump, and means responsive to depression of said plunger for withdrawing a charge of said liquid from said container, the improvement which comprises: flexible check valve means operatively disposed proximal to said vent opening for preventing outward flow of said liquid through said air intake passageway as a consequence of depression of said plunger and incident deformation of said flexible container, and for allowing flow of air through said vent opening as needed, said check valve means comprising an annular washer disposed about said plunger for abutting the underside of said skirt and slidably engaging the inner surface of said wall portion.