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).