Piston diaphragm pump

Claim 1

A diaphragm plunger pump comprising a pump housing having a pumping chamber and a drive chamber adapted to be filled with hydraulic fluid, a diaphragm sealingly mounted in said pump housing and separating said drive chamber from said pumping chamber, a plunger guided in said drive chamber for reciprocating movement causing a pumping deflection of said diaphragm by displacement of hydraulic fluid in said drive chamber, a supply container for hydraulic fluid communicating with said drive chamber via a refill valve opening in flow direction away from the supply container, a displaceable diaphragm support plate disposed in said drive chamber for limiting the deflection of said diaphragm towards said drive chamber, a control member axially movable by said support plate between a blocking position keeping said refill valve closed, and a release position permitting said refill valve to open in response to a pressure difference between said supply container and said drive chamber, said support plate being freely displaceable in said drive chamber for limited axial and tilting movement, said control member comprising a separate push rod independently guided in said pump housing for limited axial movement between a blocking position at which said push rod may abut a radially outer portion of said support plate and a release position at which said push rod rests against said support plate; spring means biasing against said push rod into said blocking position, and said support plate being displaceable by said diaphragm to rest with a radially outer portion thereof against said push rod for displacing said push rod against the bias force of said spring means into its release position.