Pump dispenser with bypass back flow

Abstract

A dispensing apparatus is disclosed. The dispensing apparatus has a product container for holding the fluid; a chamber including a dispensing cylinder having an inlet and an outlet; an inlet check valve disposed at the inlet of the chamber, the inlet check valve being openable to permit flow substantially only in a direction through the inlet check valve into the chamber; an outlet check valve disposed at the outlet of the chamber, the outlet check valve being openable to permit flow substantially only in a direction from the chamber out through the outlet check valve; an outlet spout connected with the outlet of the outlet check valve for receiving the fluid from the outlet check valve; a spring-biased piston configured for sliding movement in the dispensing cylinder, the piston being smaller than the dispensing cylinder thus providing a clearance; and a bypass backflow opening disposed in the dispensing cylinder above the spring-biased piston. The clearance is provided between the piston and the dispenser cylinder wall to allow fluid flow to pass therebetween to a region above the piston when the piston is pushed downward and, subsequently, to allow fluid flow to exit the dispenser chamber from the region above the piston through the bypass back flow opening to the product container.