Control system for timing hammers of impact printers

Abstract

A hammer timing control system for a line printer has a register for storing a digital delay value related to the actual flight time of a controlled print hammer. A delay counter activated by an initiate fire pulse counts timing pulses until the count equals the delay value in the register. A comparator generates a fire signal when the count equals the delay value in the register. The counter continues counting pulses to a second count whereupon the fire signal is terminated. The second count is either decoded or compared with a predetermined quantity in a second register to terminate the fire signal. The counter may also be an up/down counter which counts up to delay and down to terminate the fire signal. Delay values can be stored in an external memory device such as a magnetic disk for transfer to the individual registers for each of the print hammers.