Patent ID: 7038703

Claim:
A label printer for printing on labels spaced longitudinally along a carrier web with each label having a predetermined thickness and a leading edge and a trailing edge, the printer comprising: a driving mechanism for advancing the carrier web along a media path; a frame; a thermal print head assembly supported by the frame, wherein the thermal print head assembly is mounted to the frame for movement toward and away from the carrier web and includes a line of heater elements aligned transverse to the direction of travel of the carrier web; a bias mechanism urging the print head toward the web so that the heater elements are pressed against the web; a motion sensor for sensing a displacement of the thermal print head assembly as edges of the labels pass beneath the heater elements; and a controller responsive to the motion sensor for synchronizing printing with the edges of each label, wherein the motion sensor is rigidly coupled to the frame at a first end, wherein the thermal print head is rigidly coupled to a pivot which extends through the frame, wherein the motion sensor is responsive to angular displacement of the pivot, wherein the motion sensor is an arrangement including a light emitter and a detector, and wherein the light emitter and the detector are separated by a variable area mask coupled to the pivot.