Clamshell device for printers

A clamshell device for printers, comprising:

• a main body including two side walls, a paper roll seat opening used for installing a paper roll therein, with a guide surface formed at an upper edge of each sidewall defining the paper roll seat opening, said guide surface being inclined at an angle of inclination;
• a roller frame hinged to the main body and closing the paper roll seat opening, said roller frame having a holding roller coming into compression contact with a rubber roller of the main body so as to give compression force to paper passing through the nip of the rubber and holding rollers;
• a locking post movably set within two longitudinal slits of the roller frame at its side wall, said locking post being movable along the guide surfaces of the main body while being changed in its position within the longitudinal slits during rotation in either direction of the roller frame relative to the main body;
• and a spring held on said roller frame at one end thereof and on the main body at the other end thereof, and normally applying elastic force to the roller frame.