Adaptive print hammer timing system

摘要

In a printer in which an elongated shuttle is driven in reciprocating fashion across a print paper with hammers mounted along the length of the shuttle being selectively fired to print dots on the paper, a timing system provides hammer fire pulses denoting the positions of the shuttle at which hammer firing should be initiated to print in the proper dot positions. Proper timing is maintained so as to allow for printing during acceleration and deceleration as well as during constant velocity movement of the shuttle by determining the average shuttle velocity between each successive pair of fence post pulses generated by a shuttle-coupled encoder. The average velocities are represented by the time lapses between occurrence of the pairs of fence post pulses which are measured and stored during each startup of the printer as well as each time the nominal operating shuttle velocity is changed as part of a change in printer operation. Dot positions are represented by a percentage of the distance between a pair of fence post pulses, such that the time of occurrence of each dot position following the immediately prior fence post pulse can be determined by applying the percentage to the stored time lapse between the pair of pulses. The time position of each dot position as so determined is stepped back by the fixed hammer flight time to arrive at the hammer fire pulse times which are referenced to the immediately prior fence post pulse and which are used during each stroke of the shuttle.