Patent GB-1219242-A (GB)
Title: Control system for printer
Inventor: JONES C M
IPC: B41J7/36
Filed: 1969-05-23
Abstract: 1,219,242. Selective printing. GENERAL ELECTRIC CO. 23 May, 1969 [4 June, 1968], No. 26377/69. Heading B6F. [Also in Divisions G4-G6] In a printer of the kind having a plurality of types 21, Fig. 2, carried on a belt 20 and moved in succession through all the printing positions along a line to be printed so that a number of types are aligned with printing positions at the same time, the incoming characters to be printed are received in a store 43, Fig. 5, and counted in a counter 54 which assigns a column position to each character, a comparator 42 detects when a desired character type is positioned at the assigned column position by scanning the store 43 and means are provided for energizing individual print hammers under the control of the comparator. The incoming characters, represented by combinational signals on seven leads 61, are entered in turn into a shift register 50 and shifted serially through an erase gate 51 and a seven-character store 52, so that eight characters may be stored at any time. As each character of a line is entered position counter 54 receives a signal, the count representing the column in which the corresponding character is to be printed. The count, represented on seven leads, is serialized by shift register 55 and recirculated through store 56 so that the characters and the corresponding column numbers circulate together in stores 43 and 44. As the belt 20 moves, the lower tips of fingers 21 carrying the types pass a photo-cell 33 giving output pulses on lead 34 which are applied to a finger counter 40. A datum pulse is derived from a wide finger 21A which is detected by photo-cell 33 and photo-cell 33A at the same time. Gate 36 responds to give the datum pulse which resets the counter 40. The counter 40 is reset to count 32 and counts up to 127, indicating at each instant the position of the moving types. The characters circulating in store 43 are also expressed as numbers from 32 to 127 corresponding to the order of the types on the belt. When the first character 32 is in the first position 32, the second character will be in the second position and so on. In this position of the belt the counts in the column store 44 are added in turn to the value 32 in the finger counter in serial adder 41. These numbers are compared with the character numbers circulating in store 43 and upon agreement a signal passes on line 82 to operate erase gate 51 to cancel that character from the store 43. It also allows the column number from store 44 to be entered via shift register 78 into column decoder 46. The corresponding column lead C1-C80 is energized and a bit stored in unit 47. When all eight positions of stores 43 and 44 have been scanned a timing pulse 134 operates all the hammers that have been readied, the types at this time being in the printing positions. There is a hammer for each printing position as shown in Fig. 3 but the types are spaced so as to be in an odd or even position. An auxiliary comparator 85 ensures that an odd number character is printed only when the types are in the odd number position. As the characters in store 43 are erased when they are printed, they leave room for further incoming characters. To detect which spaces are empty the " less than 32 detector " 58 responds when the number stored in any position is less than 32. Since all characters are represented by 32 or more this means that no character is present in that position. The top two digits are sampled by detector 58 and if both are " 0 " the number is less than 32. New characters can then be entered, shift register 50 being enabled by a signal from gate 57.