Fluid pump dispenser having product retraction feature.

摘要

A fluid pump dispenser of the loss motion piston type provides for maintaini ng 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 e nd of the discharge. Such is effected in accordance with one embodiment by reducing th e friction force acting between the piston and the pump cylinder relative to t he 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.