Abstract: The drum of the drum unit has a plurality of jacket walls. One jacket wall is designed as a freely pivotable lid. A cam disk is located in the drum. In certain positions the lid rests at its free end on the cam disk such that it is controlled by same. When the drum rotates in one direction, the cam disk blocks the lid in its open position such that an automatic discharging of the drum takes place. At a rotating in the opposite direction the lid remains closed due to its force of gravity, so that neither a manual manipulation nor operating apparatuses for a moving of the lid are needed.