High speed impact line printer - has alignment bar inserted into notches in each printing wheel to verify setting

摘要

The line printer has two or more print wheels (10, 20, 30) on a common shaft, each with a set of characters around its periphery. Each wheel is driven by a stepping motor (15, 25, 35) through a setting wheel (11, 21, 31). Each setting wheel has two holes (16), concentric with its axis, which provides a coded indication of the angular position of the wheel. An encoder (17) detects the presence or absence of holes in a number of positions to determine the absolute readout position. An aligner bar is inserted in notches in the wheels, prior to printing, to verify alignment. The stepping motors are bi-directional and take the shortest path between successive print positions.