Abstract: A fluid driven reciprocating pump comprises a pair of heads each containing a displaceable member defining a drive chamber and a pump chamber on opposite sides of the diaphragm in one head, and a drive chamber and an inactive chamber on opposite sides of the diaphragm in the other head. A mechanical coupling connects the two displaceable members for reciprocation together; and a control valve assembly connects the drive chambers of both heads to a source of pressurized fluid for driving them through forward strokes, a spring driving the heads through return strokes.

Abstract: A fluid-driven reciprocating pump comprises a pair of pumping heads each containing a displaceable member defining a driving chamber and a pumping chamber, a mechanical connection coupling the two displaceable members for reciprocation together, and means for connecting the driving chamber of one pumping head to a source of pressurized fluid and the pumping chamber of that pumping head to a source of material to be pumped. The pump further includes means for connecting the driving chamber of the other pumping head to a source of pressurized fluid and for selectively connecting the pumping chamber of the other pumping head either to a source of material to be pumped to produce a double-action pumping operation wherein the material is pumped during both reciprocations of the displaceable members, or to the source of pressurized fluid to produce a single-action pumping operation wherein the material is pumped during only one of the two reciprocations of the displaceable members.