Patent GB-1225214-A (GB)
IPC: B41J21/17
Filed: 1969-05-23
Abstract: 1,225,214. Electric control of printing machines. GENERAL ELECTRIC CO. 23 May, 1969 [4 June, 1968], No. 26379/69. Heading G4H. A control system for a printer includes a character position column counter for assigning the horizontal positions at which successive characters in a line are to be printed, a tabulation register having a number of bit storage positions equal to the number of positions in a line, circuit means for setting a data bit in the tabulation register to indicate a horizontal position to which a tabulation operation is to be carried out by advancement of the column counter, the tabulation register recirculating and a tabulation counter cycling synchronously with it under the control of rapid clock pulses, a comparator indicating when the counts in the two counters are the same, i.e. when the position of the register corresponds to the count standing in the column counter, and gating means responsive to the indication of the comparator and to a tabulation command to transmit rapid clock pulses to the column counter to advance the column counter in synchronism with the shifting of the tabulation register to a count corresponding to the first set position in the tabulating register. The printer is of the kind having a continuously rotating belt 10 carrying the types on upstanding arms 18. The types are struck at the right moment by hammers 28 operated by solenoids 32 to print the desired characters in the appropriate ones of the eighty columns. A line of characters is entered into a recirculating store, the characters being counted in the column counter and the counts also entered into a reciroulating store, the two stores circulating together so that each character is associated with a number indicating the column in which it is to be printed. The two stores make a complete recirculation during the time a printing type moves from one position to the next. The arms 18 pass a photo-cell 40 which generates a pulse for each. These are counted, the count indicating the position of the belt. A reset pulse is produced once per cycle by photo-cell 36. The position counter indicates that a certain character (say A) is in the first column position. If the number associated with a character to be printed is added to this count, a number is obtained indicating the character at that column position. This number is compared with the character from the recirculating store and when agreement is detected it means that the type arm carrying that character is at the column position where the character is to be printed. The hammer is then operated to print the character. The tabulation register 500, Fig. 3, consists of a chain of 80 bi-stable elements. The clock 600, providing step pulses for the tabulation register 500 and counter 220, operates at a high speed so that a complete recirculation is made in the time the column counter 152 advances one step. A tabulation bit is entered by advancing the counter 152 to a count corresponding to the column required and applying a tab set signal to line 102. This is derived from a decoder receiving character, control and other data, e.g. from a keyboard. At the instant the tabulation counter 220 has the same count as column counter 152, comparator 210 opens gate 230 to allow the set pulse to pass via OR gate and recirculating loop 581 to enter a bit in the register 500 at the appropriate position. More than one tab bit may be entered. During printing the comparator indicates agreement once during each position of column counter 152 as the counter 220 cycles at high speed. If the decoder gives a horizontal tabulation command on line 104 gate circuit 420 causes flip-flop 430 to set, opening gate 440 to permit high-speed clock pulses to pass to counter 152. Counter 152 and tabulation counter 220 therefore advance together. When the tabulation register gives an output on line 583 flip-flop 430 resets leaving the counter 152 in the next tabulating position. The next incoming character is then associated with this number and printed in this position. The lefthand margin is set by setting a tabulation bit as described above. Flip-flop 350 is set if there is a tabulation bit other than in the first line position. This signal is gated with a " start new line " signal to provide an enabling signal for And gate 420. Specification 1,219,242 is referred to.