Patent 7446790 was granted and assigned to Fujitsu on November, 2008 by the United States Patent and Trademark Office.
A thermal printer including a thermal head; a platen cooperating with the thermal head to nip a printing sheet between the platen and the thermal head; an elastic member applying a biasing force to the thermal head in a direction to make contact with the platen; a frame supporting the thermal head in a shiftable manner and the platen in a detachable manner; and a biasing-force control mechanism controlling the biasing force of the elastic member. The biasing-force control mechanism operates to ensure, when the platen is mounted to the frame, a required contact pressure between the thermal head and the platen under the biasing force, and to prevent, when the platen is removed from the frame, the thermal head from being deformed due to the biasing force.