Adaptive print hammer timing system

A printer comprising the combination of:

• an elongated shuttle mounted adjacent a print station, the shuttle having a plurality of dot printing hammers mounted along the length thereof;
• means for driving the shuttle in reciprocating fashion relative to the print station such that the shuttle undergoes a succession of strokes of opposite direction relative to the print station, the shuttle accelerating from rest to a nominal operating velocity and then decelerating to rest during each stroke;
• an encoder coupled to the shuttle for providing a succession of shuttle position pulses during each stroke of the shuttle, the shuttle position pulses representing essentially equal increments of movement of the shuttle and being generated while the shuttle is accelerating and decelerating as well as moving at the nominal operating velocity upon the arrival of the shuttle at each of a plurality of locations along a path of movement of the shuttle;
• means for separately storing time values representing the time lapse between the occurrence of each pair of the shuttle position pulses during a stroke of the shuttle;
• means for determining portions of the stored time values representing the occurrence of dot printing positions between the pairs of shuttle position pulses;
• means for combining a fixed hammer flight time with each of the determined portions of the stored time to determine a hammer fire time with reference to a preceding one of the shuttle position pulses for each of a plurality of the dot printing positions;
• and
• means responsive to the hammer fire times and to the occurrence of the shuttle position pulses for providing hammer fire signals during each stroke of the shuttle.

A method of timing the firing of a plurality of hammers on a shuttle as the shuttle undergoes reciprocating movement in successive strokes of opposite direction, the shuttle velocity during each stroke being characterized by acceleration from rest to a nominal operating velocity followed by deceleration to rest, comprising the steps of:

• generating from the sensed travel of the shuttle a succession of fence post pulses as the shuttle undergoes each stroke, the fence post pulses corresponding to the sensing of the actual positioning of the shuttle at each of a succession of generally equally spaced locations along the stroke;
• separately determining the time of travel of the shuttle between each pair of fence post pulses;
• defining the locations of a plurality of dot positions along the stroke relative to the pairs of the fence post pulses in terms of portions of the times of travel of the shuttle between each pair of fence post pulses at which the dot positions occur;
• and
• determining hammer firing points along the stroke by determining the time of occurrence of each dot position in accordance with a portion of the separately determined time of travel of the shuttle between the adjacent pair of fence post pulses in which the dot position is located and then preceding the time of occurrence of each dot position by a fixed hammer flight time.