GB1006699A - Control system for high speed printers - Google Patents

Abstract

1,006,699. Electric selective signalling. ANELEX CORPORATION. March 6, 1963 [March 8, 1962], No. 9025/63. Heading G4H. [Also in Division B6] A printer hammer control system comprises a capacitor C7; a first switching device S1 which on receipt of a first and a second signal respectively charges and ceases to charge the capacitor C7; and a second switching device S2 adapted to discharge the capacitor C7 through a coil HC1 to actuate the printer hammer. In Figs. 1, 2 (Fig. 1, not shown) a line of n characters is printed in one revolution of a set of n printing wheels, two wheels with magnetically-detected teeth being provided on the printing wheel shaft to produce on index pulse every rev. and a character clock pulse as each of the sixteen possible characters comes under the printing hammers. The character clock pulses are fed to a binary counter the inverse outputs of the four stages of which provide an indication of the character in printing position in inverted binary code. This indication is compared in n comparators CP1, CP2 ... with binary-coded representations of the required characters which are stored in switches. Each comparator, e.g. CP1, consists of four AND-gates A7 . . . A10 feeding a unit LU1 which acts as a NOR gate on arrival of one of the character clock pulses at an input j. Each comparator CP1 ... thus provides an output pulse to a corresponding hammer driver circuit DR1 ... whenever no pair of compared input bits consists of two 1s. The first of these pulses makes a silicon controlled rectifier S2 conduct to discharge a capacitor C7 through a hammer driver coil, e.g. HC1. At the end of the cycle (rev.), the counter provides a pulse to an input a of a unit 27 thus making a siliconcontrolled rectifier S 1 conduct and produce voltage across a resistor R1. This charges the capacitors C7 in all the hammer driver circuits DR1....When a switch is closed to start the printing of the next line, a pulse arrives at input b of unit 27 and cuts off rectifier S1 thus stopping the charging of the capacitors C7. Since capacitor recharging is thus done at the end of the cycle only the first pulse from each comparator CP1, CP2 ... in a given cycle is effective to print. The code representing the characters in position may be other than inverted binary, a set of coded toothed wheels on the printing wheel shaft providing the signals directly. Fig. 3 (not shown) shows a modification in which the n characters to be printed arrive in four-bit parallel binary-coded form, serially by character, and are read into four n-stage magneticcore shift registers by a sequence of n clock pulses arriving with the data. As before, a counter supplies a four-bit parallel invertedbinary-coded representation of the character in printing position, and each 1 in this representation reads out (and re-writes) as a pulse every 1 stored in a corresponding one of the shift registers. The read-out bits pass to n units of the type LU1 (Fig. 2) which control hammer driver circuits as before. Specification 765,059 is referred to.