Diaphragm pumps

A fluid-pressure operated pump comprising a pumping chamber having inlet and outlet openings for a fluid to be pumped and a fluid pressure driving chamber, a flexible diaphragm between the pumping and driving chambers being displaceable by the fluid pressure in said driving chamber to pump fluid through the pumping chamber, said driving chamber having an inlet for a supply of pressure fluid thereto and an outlet valve comprising a valve member biased to close said valve, means connecting the outlet valve member to the diaphragm and permitting a limiting deflection of the diaphragm by the pressure of the fluid in the driving chamber without displacement of the valve member from said closed position, diaphragm displacement by the pressure fluid beyond said limited deflection acting through said connecting means to displace said valve member to open the outlet valve and reduce the driving chamber pressure, thereby reversing the direction of displacement of the diaphragm to permit the valve member to return to the valve-closing position and allow the pressure in the driving chamber to increase again, said means connecting the outlet valve member to the diaphragm comprising a connector member that is flexibly deformable for permitting relative displacement between the valve member and the diaphragm without opening the outlet valve, said connection member comprising a unitary, one-piece unit with at least one of said diaphragm and said outlet valve.