Patent ID: 8152029

Claim:
A dispensing apparatus, comprising: a product container for holding a 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 said outlet of said outlet check valve for receiving the fluid from said outlet check valve; a spring-biased piston configured for sliding movement in said dispensing cylinder, said piston being smaller than said dispensing cylinder thus providing a clearance; and a bypass backflow opening disposed in said dispensing cylinder above said spring-biased piston, the clearance being small enough such that fluid within the dispensing cylinder is pushed out of the dispensing cylinder through the outlet check valve during a downward stroke of the piston and is at least one of selected based on the viscosity of the fluid or larger than a largest particulate contained in the fluid, said clearance being provided between said piston and said dispenser cylinder wall to allow fluid flow to pass therebetween from below the piston to a region above the piston at all positions of the piston within the dispensing cylinder during an entire downward stroke of the piston 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 during an upward stroke of the piston, wherein when the piston is disposed at the top of the piston's stroke within the dispensing cylinder a cavity is formed within the dispensing cylinder and above the piston, and the piston having a top surface that slopes downward toward the bypass backflow opening to direct any of the fluid resident in the cavity towards the bypass backflow opening.