Patent GB-1438534-A (GB)
Title: High speed printer
IPC: G06K15/10
Filed: 1973-03-30
Abstract: 1438534 Control of printers CENTRONICS DATA COMPUTER CORP 30 March 1973 [6 April 1972] 15418/73 Heading G4H A dot-matrix printer comprises a carriage assembly 11, 12 containing N solenoid-operated wires 13b arranged parallel to a line of print, whereby the distance travelled by the assembly in printing one line of dots is 1/Nth the length of a full line of dots. As described each character is a 7 x 5 dot matrix, each of the 7 rows for the whole line being printed in turn. With 8 solenoids 13 and an 80-character line, each solenoid simultaneously prints 10 consecutive character rows, starting with row 1 of characters 1, 11, . . . 71 (columns 1-5 in turn), then characters 2, 22, . . . 72 &c., up to characters 10, . . ., 80 (end of rows); the procedure is then repeated for rows 2, . . ., 7. Synchronism between dot position and print wire actuation is achieved by means of relative motion between a light and photo-cell 372, 373 and a slotted strip 360. Data in octal or USC11 form is fed into a recirculating register 214, every tenth character then being converted in a generator 215 into dot-matrix form. An entire dot column is fed from 215 to a multiplexer 212 which selects the correct bit for the row being printed and transmits it to a buffer 213 (8 flip-flops); the corresponding bit for every 10th word is stored in 213, then all 8 bits are fed to solenoid drivers under the control of a strobe circuit 235. A counter 205 counts recirculating words in register 214 and causes a decoder 207 to actuate register 213 at the appropriate times; a counter 206 determines when dot information is available for all 8 solenoids, after which the printer assembly can be moved one dot column position. A counter 208 determines when all 5 dots in the corresponding row of the 8 characters have been made available for printing, and that an interword space has been supplied: a column decoder 209 is controlled thereby to select the appropriate dot column from generator 215. Counter 210 counts the number of characters in the current row that have been completed, while counter 211 records the number of completed rows to cause multiplexer 214 to select the correct dot in the column transmitted from 215. A detailed description is provided (Figs. 6a-6n, not shown) for the individual items of Fig. 3. The electromechanical system for controlling and synchronizing printer operations (including clutches and gears, Figs. 2-2d, not shown) provides for 1, 5 and 12 "dot feeds" to respectively perform dot row spacing, character line spacing and high speed line feeding. Movement of the assembly back and forth along the print line is achieved by means of a gear-operated "shuttle cam" (114). A line of characters of double width may be printed, each column being printed twice. The paper may be moved continuously, in which case the solenoid carriage assembly is mounted at a slight angle to the horizontal (Figs. 7a-7c, not shown). The carriage assembly may also be formed in two independently operable halves for ledger type entries. The assembly may also be designed for rapid reversal of the print wire positions (when the print wire assembly is turned upside down) to ensure even wearing of the wires during long use. Any size dot matrix up to 9 x 9 is envisaged, e.g. for printing of upper and lower case characters, "below the line" symbols and foreign language characters (such as ideographs).