| 摘要 |
A thermal print head control mechanism for use with a thermal typewriter or thermal printer supported on a carrier housing which moves along a platen and the mechanism includes a bidirectional motor and pinion gear for selectively rotating a sector gear about a center point. A bellcrank having a pair of arms is supported on the carrier housing for pivotal rotation about a point between the arms. An end of one of the arms carries a vertically directed print head proximate the platen and an end of the other arm is connected to an anchor near one side edge of the sector gear by a coil spring. The anchor point is positioned so that as the sector gear is rotated from one position to another, the longitudinal axis of the coil spring will cross over the sector gear center of rotation. During rotation of the sector gear, the axial length of the coil spring is such that it will be tensioned when its longitudinal axis is on each side of the sector gear center of rotation. In this manner the print head will bias against the platen and biased away therefrom as the gear is rotated. Additionally the mechanism is provided with abutments to limit the rotation of the sector gear and electrical controls for programmed gear rotation and for control of thermal print head printing.
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