Patent ID: 7500582

Claim:
A dispenser pump having a pump body and a plunger reciprocable relative to the pump body by hand in a pumping stroke, thereby altering the volume of a pump chamber defined between the pump body and plunger, the pump chamber having a base, an inlet at said base to admit flowable material from a container to which the pump is secured and an outlet at said base to a fixed discharge passage, the discharge passage leading up beside the pump chamber to a fixed discharge nozzle having an external opening, wherein the discharge nozzle opening has a closure valve comprising a wall of resiliently flexible material whose periphery is constrained at the adjacent discharge nozzle structure, which wall is outwardly concave in its rest condition and which has plural radiating slits constituting said discharge opening, which slits are closed in said outwardly concave rest condition of the wall but open when the wall bulges outwardly under pressure of flowable material discharged from the pump chamber through the discharge passage; wherein a pump outlet valve is provided between the pump chamber and the discharge nozzle opening, the pump outlet valve being a flap valve and the discharge flow area at the pump outlet valve being greater than the discharge flow area at the discharge nozzle immediately upstream of said closure valve, whereby at the end of a discharge of said flowable material in said pumping stroke, on resilient retraction of said closure valve wall to its rest condition there is a reverse flow of the flowable material back along the discharge passage, and return movement of said flap valve to a closed condition thereof accommodates said reverse flow; the pump outlet valve flap being an annular flap leading from the pump chamber into an annular outlet chamber which is a first part of the discharge passage; wherein the annular outlet valve flap surrounds the pump chamber inlet; wherein an inlet valve for the pump chamber inlet is a duckbill valve, the duckbill valve having a tip with a slit that faces the pump chamber; and wherein the duckbill inlet valve is formed in one piece with the outlet valve flap.