| 摘要 |
PURPOSE:To enable a printing process to be continued until a a replacement of a dot printing head having a broken pin is completed, by a method wherein; the length of the broken wire pin is detected, and the drive of wire pin is so switched as to be based on a clock having a cycle capable of imparting a sufficient impact to a medium even with the length of the broken wire pin. CONSTITUTION:The condition of a broken pin is detected in such a manner as that; a signal generated when a voltage waveform in a magnet drive part 2 is differentiated in a differentiating circuit 71 and a pulse having a predetermined cycle are ANDed, and a detection signal is sent from an AND 72 to a selection circuit 60 in a shuttle control part 8. The selection circuit 60 selects a clock CLK2 outputted from a clock generation part 50 to send it to constant speed control part 42. In addition, the cycle of the clock CLK2 outputted from the clock generation part 50 is made approximately twice that of a clock CLK1 outputted from a reference clock generation part 10, because a pin is generally apt to break at a point about half of its full length, thereby imparting the exciting cycle corresponding to the stroke length of the broken pin resulting from the breakage. A shuttle unit 6 is driven on the basis of the clock CLK2 outputted from the clock generation part 50. |
