Abstract: A hydraulically driven membrane pump for conveying a fluid, including a pumping chamber, a working chamber and a membrane which separates the pumping chamber and the working chamber in a fluid-tight manner, and means for reciprocating the membrane between a suction stroke position and a pressure stroke position, wherein the pumping chamber comprises at least one suction port through which the fluid to be conveyed is sucked into the pumping chamber in the suction stroke, and at least one discharge port through which the fluid to be conveyed is discharged from the pumping chamber in the pressure stroke, the membrane being connected on the working chamber side to a pull rod which is resiliently biased in the direction of the movement of the suction stroke.

Abstract: A metering diaphragm pump includes a metering chamber, a working chamber and a metering membrane. The metering chamber and the working chamber are separated from one another by the metering membrane. A device for moving the metering membrane back and forth between a first and a second position is provided. The volume of the metering chamber is smaller in a first position than in the second position, and a protective membrane is disposed next to the metering membrane on the working chamber side.