Fluid pump dispenser having product retraction feature

Abstract

A fluid pump dispenser of the loss motion piston type provides for maintaining the discharge open a slight interval at the commencement of each plunger upstroke while the pump chamber expands to retract product from the discharge passage into the chamber to thereby avoid the formation of product droplets at the exit end of the discharge. Such is effected in accordance with one embodiment by reducing the friction force acting between the piston and the pump cylinder relative to the friction force acting between the piston and the stem. In another embodiment an inlet valve assembly has a portion lying in the path of the piston which portion is connected by spring legs to a valve portion such that the restoring force of the spring legs shifts the piston together with the stem at the commencement of the plunger upstroke which maintains the discharge passage in open communication with the chamber.

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