Abstract: Both the rotating drive and also the back and forth movement of the pump piston (5) occurs through a joint arrangement (29), which consists of a first through (65) on the crank (28), a second trough (67) on the piston (5) and a rolling member (30) which is received in the troughs (65, 67). The troughs are pressed by a springy ring (68) against the rolling member (30). The troughs (65, 67) have a slightly smaller curvature than the rolling member (30), so that the rolling member (30) rolls in the troughs (65, 67). Friction in the joint arrangement (29) is avoided through this, which results in a long life of the joint arrangement (29).

Abstract: A piston pump with a rotating piston is driven by a motor. A crank is provided on the motor shaft and has a first rolling surface on its front side. A further rolling surface engages the first rolling surface, the further rolling surface being provided on an arm which is connected fixedly to the pump piston. In one preferred embodiment, the crank is coupled with the piston in such a manner that a projection on a part connected fixedly with the piston engages a recess in the crank. An arrangement is provided for maintaining the contact between the rolling surfaces during the suction stroke of the pump. The piston controls an inlet opening and an outlet opening to the chamber in which it is movably supported. The transmission of forces during the discharge stroke through surfaces which roll on one another results in a long lifetime of the pump and quiet running.