GB1311754A - Apparatus for producing incremental movement - Google Patents

Abstract

1311754 Printers MOHAWK DATA SCIENCES CORP 6 May 1970 [24 June 1969] 21936/70 Heading G4H [Also in Division H2] A line printer comprises a rotating drum 1 carrying the type, a hammer module 8 carrying four hammers 8a and movable in steps along a line parallel to the drum, and a feeding mechanism (not shown) for feeding paper between the hammers and the drum. Except when moving from one line to the next, four adjacent characters are printed during every alternate revolution of the drum, the intermediate revolutions allowing time for the hammer module to move laterally to its next position and for new data to be requested. Hammer operating arrangement.-A disc 20 mounted on the shaft la of the drum is interposed between a light source 21 and a bank of photodetectors 22. For each line of type on the drum the disc has a radial row of indicia, the six inner indicia providing at the photodetector output a binary-coded signal representing the corresponding line of type. Data is supplied in batches of four characters at a time (each represnted by a six-bit signal) to comparators 24a-24d, and when an input signal matches that from the photodetector a corresponding hammer driver 28a-28d is operated, subject to the existence of a signal at the output of a control gate 27. The AND gate 27 receives a marking pulse at each angular position of the disc, a print signal from a flip-flop 40 and a control signal (29). Shifting the hammer module.-Flip-flop 30 is switched once per revolution of the drum so that control gate 27 is readied in alternate revolutions only. On the intermediate revolutions pulse generator 32 is fired to trigger a control 37 for shifting the hammer module one position laterally using a linear stepping motor and to request new data (43). When the hammer module reaches the end of the line it mechanically closes a switch 19b to advance the paper (39) and to change the state of flip-flop 40, thus removing the print signal from control gate 27. No printing can now take place until pulse generator 32 has supplied sufficient pulses to step the hammer module back to the beginning of the line, when a switch 19a is closed to switch back the flip-flop 40. Closure of the main switch 38 to activate the printer is also arranged (41) to change the state of flip-flop 40 so that no printing can take place initially until the hammer module has been shifted to the beginning of the line.