Abstract: Membrane piston pump or piston pump, respectively, with a piston guided in a cylinder which acts upon a chamber to which a pump membrane is assigned, which is on its part facing a pump chamber which is connected to an aspirating connection and a pressure connection via valves, a drive equipment for the piston which is connected to the piston via a piston rod, characterised in that the drive equipment has an electric motor, which is in rotating connection with the cage of a planetary roller thread drive, the threaded spindle of which is axially coupled to the piston rod, the cage being rotatably but axially fixedly beared in a housing of the drive equipment and a path transmitter is provided which creates a path signal in accordance with the path travelled by the threaded spindle, which signal is given up to a control equipment for the electric motor for reversing the rotational direction of the electric motor after a predetermined path of the threaded spindle.