PURPOSE: To prevent the damage of a tractor, by a method wherein a bent part bent in a closing direction is mounted to the end part of the door of the tractor and pushed by the guide provided to a cover when the cover of a printer is closed in a state opened to the max. degree to receive torque.

CONSTITUTION: A tractor door 2 rotates around the shaft provided to the main body of a tractor 1 to open and close. In such a state that the tractor door 2 is closed by the tensile spring mounted between the main body of the tractor 1 and the tractor door 2, the torque in a door closing direction is given to the tractor door 2. A guide 4 is mounted to the inner surface of a cover 3 and a bent part 5 is provided to the end part of the rear side of the tractor door 2 and, when the cover 3 is closed in such a state that the tractor door 2 is opened, the tractor door 2 is closed because the bent part 5 is pushed by the guide 4 and, by closing the cover 3, the tractor 1 is not damaged.