PURPOSE: To protect parts of a printer against overload that is possibly caused in switching the power transmitting means, by employing an arrangement in which, at the time of printing, only a pot roller is rotated in normal direction, and at the time of cleaning, a blade roller is set into rotation and also the pot roller is rotated reversely, thus accomplishing automatic cleaning of printer with ease.

CONSTITUTION: In printing operation, transfer roller 4 is swung in synchronism with the main body of printer and pot roller 2 is rotated in the direction of arrow a shown in the drawing, so that ink 3 in an ink pot is supplied to printing drum 10 via ink feed rollers 4W9. In the above while, blade roller 1 is kept at rest. In cleaning operation, on the other hand, driving motor 13 is rotated reversely, so that pot roller 2 is rotated in the direction of arrow b. Resultantly, ink 3 in the ink pot is carried on the surfaces of rollers 1, 2, so that the amount of ink 3 in the ink pot is reduced. Subsequently, when cleaning-liquid supply valve 52 is opened by an electric signal, cleaning liquid is supplied on blade roller 1, pot roller 2 and kneading roller 5, and ink attached on these rollers is scraped off into pan 19.