Pump with internal pressure relief

Abstract

A fluid pump having a rotary power source, a rotary to reciprocating motion converter in the form of a cam and cam follower, a rotary speed reducing gear train coupling the rotary power source to the rotary to reciprocating motion converter, and no pressure relief bypass is disclosed. The pressure relief function of limiting the fluid pressure within the pumping chambers to predetermined maximum pressures is provided by a pair of springs coupling a pair of opposed diaphragms of a pair of pumping chambers. The springs function as a spring-loaded lost motion coupling which absorbs energy while limiting the pressure in a pumping chamber and releases that stored energy to help power the pump while expelling fluid from the other chamber. The diaphragms are fixed relative to their respective pumping chambers about their outer peripheries and centrally coupled to their respective springs. The diaphragms are normally driven to move in unison, but cease to move in unison when one of the springs yields. The pump is especially adapted to pumping relatively viscous fluids. Each chamber has one-way inlet check valves and one-way outlet check valves. There is a common pump outlet for merging the viscous liquids emanating from the chamber outlet check valves and a common pump inlet for supplying the viscous fluid to the chamber inlet valves.