Patent GB-1084027-A (GB)
Title: Printer apparatus
IPC: G06K15/08
Filed: 1965-11-29
Abstract: 1,084,027. Printers. INTERNATIONAL BUSINESS MACHINES CORPORATION. Nov. 29, 1965 [Dec. 2, 1964], No. 50562/65. Heading G4H. In printer apparatus, stored characters to be printed have associated stored tag marks, a mark being altered on printing of the associated character, and a signal being produced when all the marks have been altered. In an " on-the-fly " line printer incorporating subscan operation, the signal causes beginning of printing of the next line. A 3D core matrix has seven planes 23 to store 7-bit characters to be printed, and four further planes 50-53, each having a bit position for each character. All the planes are addressed in common by rings 30, 31 which also control a matrix 40 to select print hammers 17. The characters are read out in turn, rewritten and compared 48 with a character counter 43 indicating the position of a type-belt 10 relative to a row of print hammers 17. Equality causes actuation of the hammer currently selected by the matrix 40 and alteration of the currently addressed positions of the further planes 50-53 as follows: (a) an " equal check " plane 53 has a 1 changed to 0, (b) a " print cycle control" plane 51 previously set with a 1 at every position corresponding to a character to be printed has a 1 changed to 0, (c) a " hammer fire " plane 52 receives a 1. Alteration (c) is performed by a signal from the output side of the hammer drivers, the others (a) and (b) from the comparator 48. The bits in the " equal check " and " hammer fire " planes 53, 52 are compared 85 and if equal cause the corresponding core in an " error check " plane 50 to be set to indicate error. The spacing between type elements 11 is slightly less than 1À5 times the spacing between hammers 17, so that during operation hammers 1, 4, 7... become aligned with type elements in turn (one subscan) then hammers 2, 5, 8... (a second subscan), then hammers 3, 6, 9 ... (a third subscan). Three subscans constitute one scan, and in general a plurality of scans will be necessary for printing a line. During readout and rewriting of characters from the memory 23, the corresponding positions of the " print cycle control " plane 51 are read out and rewritten via an inhibit latch 91. The output of this latch is inverted (118) to provide a " print line complete inhibit " signal. If this signal does not appear during a scan, a trigger (120) remains reset to enable one input of an AND gate (124). Another input to the AND gate (124) is provided only if a predetermined number of scans have already taken place as indicated by the stages of a binary scan counter 110 fed by the third stage of a three-stage ring 111 which receives one pulse per subscan. If the AND gate (124) is fully enabled, a trigger (103) is set to produce a " line full " signal which, when and if the third subscan of the current scan has been reached and the memory addressing rings 30, 31 are at the last address, will reset a trigger (132) to produce a " print scans complete " signal which will call for the next line of characters to be supplied from a computer to the memory 23 and printing of them to take place. The " print scans complete " signal also resets the scan counter 110. If the latter ever reaches capacity, a " line full " signal is produced anyway. The " line full " signal also samples the output of the " print cycle control " plane inhibit latch 91 to set the currently addressed position of the " error check " plane 50 in the case of error. A slotted magnetic drum 47 driven with the type-chain 10 produces subscan pulses which synchronize a clock 32 controlling operations. An error indication is also given if a " home " signal produced by the magnetic drum 47 does not coincide in time with particular positions of the character counter 43 and a subscan counter 44 (the function of which is to preset the character counter at the beginning of each subscan).