| 摘要 |
PURPOSE:To switch the impressing force of a thermal head, pressing and releasing with the same member in a simple structure thereby to improve a printing quality by engaging cams distant from a center with an elastic member, and switching the impressing force of the head, impressing and releasing. CONSTITUTION:A radius (r) from the outer in periphery of a cam 3 to a central shaft 7P is gradually increased from the minimum position 3a to 3b, 3c, and cam position detecting means is composed of a reflection 8 and a reflection type photosensor 9 mounted on the cam 3. The cam 3 is rotated by a step motor 4 to vary the radius (r) to the outer periphery, thereby altering the tension of a coiled spring 2, and energizing means for varying a impressing force of the head 1 to a platen 13 is composed, and a head pressing and releasing mechanism is formed of releasing means of a coiled spring 15. Accordingly, the switching of the impressing force of the head 1, impressing and releasing are performed by the same cam 3 in an extremely simple structure, thereby improving a printing quality. |
