DETECTION OF LETTER MISSING IN IMPACT TYPE PRINTER

摘要

PURPOSE:To automatically detect the disorder of a hammer mechanism in an impact type printer by a method in which output signals from a piezo-electric element to sense the impaction of hammer strike are counted, and the sum of the counter number is compared with the number of the hammer mechanism. CONSTITUTION:A time series drive routine 23 is actuated and hammer mechanisms 1a-1n are operated orderly one by one over all digits by being synchronized with the movement of a type belt 13 for printing. In this case, the vibration of a platen 14 caused by the impaction of the hammers is detected by piezo- electric elements 21a-21n and the detection signal 31 is sent out to a counter 22. The counter 22 is reset by start signal 33 sent out at the time when the time series drive routine 23 is actuated, and the detected signal is counted up until end signal 34 representing the completion of the printing of all digits is sent out. When the final value differs from digit number (n), a signal to show the presence of fault in the hammer mechanisms 1a-1n is sent out, warning is generated by a print control circuit 3, and the printing operation is stopped.