Dot printing apparatus

A printing apparatus for printing marks on a printing web comprising:

• a printer body frame;
• a single rotational drive motor for producing drive rotational force;
• rotational force transmission means for transmitting the rotational force;
• a drive wheel having a shaft which is rotatably supported to said printer body frame;
• spring-biased link means rotatable around said shaft supported by the printer body frame;
• printing web feeding means;
• a printing drum having a helical one turn member having printing projections thereon, disposed so as to face the printing web, and supplied with the rotational force through said drive wheel at all times, said drum being rotatably mounted on said link means;
• and interlock means including a ratchet gear engageable with a ratchet pawl movable in response to solenoid means, said ratchet gear being rotated by the rotational force derived from said drive wheel,
• whereby when the ratchet gear is engaged with the ratchet pawl operatively moved by said solenoid means, by the rotational force derived from said motor, the ratchet gear is rotated and is slid on said ratchet pawl against the spring force of said link means, and said printing drum is rotated around said shaft of said drive wheel and contacts with the printing web backed-up by said printing means.