Multiple position thermal printer head mechanism which is disturbance insensitive

In a thermal printer which has a roller platen, a dye receiver medium held against the roller platen and a print head which presses a dye donor medium against the receiver and roller platen in a sandwich for dye transfer, the improvement comprising:

• a) a cover mechanism rotatably mounted about a first axis, including latching means secured to the cover mechanism for holding the cover mechanism in a closed position during operation and permitting the cover mechanism to be opened at other times;
• b) a head positioning arm rotatably mounted about a second axis such that the head positioning arm is movable between a printing position, a loading position and an ejecting position, and said head positioning arm further having a first cam follower and a pin receiving recess which permits movement along an arc;
• c) a print head assembly which is responsive to said head positioning arm for movement of said print head assembly to corresponding loading, printing and ejecting positions, and said print head assembly further including a first pin for engaging said pin receiving recess, guide means which aligns said print head assembly to said roller platen, and a second cam follower;
• d) a first cam which can bear against said first cam follower such that said head positioning arm moves to a corresponding printing, loading or ejecting positions as said first cam rotates;
• e) a member fixedly secured to said cover mechanism which defines a second cam surface, and resilient means urging said print head assembly against said roller platen or said second cam surface;
• and
• (f) the first and second axes being substantially coaxial to thereby reduce undesirable movement of the print head.