GB1287558A - Improvements in or relating to printers - Google Patents

Abstract

1287558 Line printer NORTEC COMPUTER DEVISES Inc 1 Sept 1970 [14 Nov 1969] 41740/70 Heading G4H [Also in Division B6] In an impact line printer the characters 302 (Fig. 3a) are carried on a band 300 which also carries marks 304 which may be counter to identify the characters. There are 132 print positions each with its own hammer 100 (Fig. 4). The hammers are biased towards the print position by springs 130 and retained in a cocked position by magnets 110. The hammers are released by activating coils 120 to oppose the magnetic field. When the coil is activated the hammer swings forward and forces the paper against an inked tape and the character. The hammers are divided into five sets of twentyseven each, each set being activated in turn. Data to be printed is fed into recirculating shift register 400 (Fig. 5). The character code at each printer position in turn is registered in counter 610. The marks on the counter band are picked up by sensor 800 and fed to the counter 610. Shift register 400 is advanced five stages at a time so that every fifth character is compared. At the same time counter 610 is advanced by clock 1010. Thus the characters on the type band corresponding to a given print position and the character required for printing are compared by comparator 500. The result being stored on shift register 750. When all the comparisons for a given set have been made, the contents of the shift register are used to activate the hammer release coils for which agreement was obtained. The process is then repeated for the remaining four sets of the print positions. To complete a line of type, the whole process has to be performed sixty-four times so that in a complete cycle every one of the sixty-four characters has at some time been adjacent to every print position.