A damping element (20) in the form of a sleeve pump or the roller lever of a diaphragm pump on the periphery of the cam path (16) is engaged by the cam tip (18), or of a cam comprising an oil, water or fuel pump, possibly using two cams allocated to pumps feeding the same or different media. The cam should be axially bored (26) for the shaft (14) and a driver element (22) on the shaft defines the cam angle range and a recess (28) off the bore in the cam surrounding the driver with play contains a damping fluid. The shaft re-sets the cam so the roller (22) returns onto the endstop (36) in the start-out position. This re-set commences whenever the cam tip engages the sleeve segment etc (38) in a mechanical contact followed by resistance on the part of the sleeve medium which re-sets the cam to the start of its defined range or path. In so doing, each cam action propels a portion of medium (40).
