A printing apparatus is disclosed, in which a printed document is separated from a continuous strip of paper by a blade driven by a reversible motor that has a forward rotation direction, in normal operation, and a backward rotation direction, for blade unlocking in the event of jamming of the blade, in which the backward rotation first has a free initial portion without transmitting force to theblade, then a tooth carried by the motor shaft knocks against another tooth carried by a hub of a gear that transmits force to the blade, unlocking the jam thereof.