Three valve precision pump apparatus with head pressure flowthrough protection

摘要

A pumping apparatus for moving a pumped fluid from a reservoir to a destination in response to variations in the pressure of a pumping fluid includes a pump housing; a pumping chamber; an input passageway; an exit passageway; and a passageway network between the input passageway and the exit passageway. A diaphragm divides the pumping chamber into first and second volumes for respectively receiving the pumped and the pumping fluids. Apparatus is provided for intermittantly varying the pressure of the pumping fluid. A first diaphragm valve responsive to variations in the pressure of the pumped fluid is positioned between the input passageway and the passageway network. A second valve also responsive to variations in the pressure of the pumped fluid is positioned in the passageway network for being opened when the first valve is closed and visa versa. A third valve is positioned between the exit passageway and the second valve in the passageway network to prevent pumped fluid flowthrough caused by a pressure head at the input or exit ports.