A diaphragm pump is described comprising a reciprocated diaphragm for expanding and contracting a chamber communicating with a passageway connecting the housing inlet and outlet for pumping a fluid therethrough, and a pair of check valves in the passageway permitting the fluid to flow only from the inlet...http://www.google.com/patents/US4375346?utm_source=gb-gplus-sharePatent US4375346 - Diaphragm pump
