Abstract: An apparatus for the essentially uniform feed or conveying of a fluent or flowable medium by means of to-and-fro moving feed or conveying pistons, wherein there are provided at least two single-acting feed pistons. Each of the feed pistons is equipped with a forward drive and a return drive. The return velocity is greater than the forward velocity. The forward drive and return drive are driven with a phase shift such that the terminal or end portion of the feed stroke of the one feed pump overlaps the starting portion of the feed stroke of the other feed pump.

Abstract: An apparatus for the control of a fluid medium incorporating a fluid medium actuated switching element which can be reversed between two switching positions by means of two actuation elements working in the opposite sense. The actuation line or conduit of each actuation element is controlled by a normally closed shutoff valve, each actuation element is connected at its actuation line between the shutoff valve and a throttle location.