JPS57129758A - Impact printer - Google Patents

Abstract

PURPOSE:To realize printing operation with prescribed printing pressure constantly even when the thickness of a printed substance differs and thereby to conduct printing of uniform density, by controlling the impact operation of a printing head based on an output information obtained through comparison of detected printing pressure with prescribed printing pressure. CONSTITUTION:When the printing head 2 moves in the main scanning direction and a following head driving signal SN is delivered, a transistor 21 is turned ON to electrify a solenoid 6 and thereby to make the head 2 conduct impact operation. At this time, althrough a piezoelectric element 3 is absent from a platen 1 and thus no printing pressure is detected, a counter 14 counts a clock signal afresh simultaneously with the impact operation of the head 2 and the content of the counting is delivered to a comparator 10. And, the previous pre- scribed time of electrification held in a latch 15 and a counting time from the counter 14 are compared with each other in the comparator 10, and when they coincide with each other, a coincidence signal is delivered to a NAND gate 16 to turn the transistor 21 OFF. The electrification of the solenoid 6 is thereby stopped and thus the impact operation of the head 2 is finished.