Patent GB-1475937-A (GB)
Title: Printing systems
IPC: B41J2/13
Filed: 1974-08-29
Abstract: 1475937 Control of printers LAMSON INDUSTRIES Ltd 29 Aug 1974 [4 Sept 1973] 37748/74 Heading G4H [Also in Division B6] An ink jet printer wherein variable data is printed in alignment with fixed data printed by a master plate cylinder on a moving web at press speeds comprises a control system 33, Fig. 1, for generating character timing signals STR1, STR2, Fig. 14, representing the sequential position of the variable data in a multiple line message format and for automatically adjusting the signals to allow for different web speeds and form depths. Printing is effected by three groups of five nozzles (Fig. 3, not shown) staggered transversely across the web. There are 10 characters per inch and 38 characters per line; there are four possible form depths, and the web speed can vary up to 700 ft./min. A transducer coupled to the web produces clock pulses CP at a (variable) rate of 120 pulses per inch of web movement, for use throughout the control system. Printing (Figs. 1 and 15).-The variable data is read from tapes 30 and fed to 33 by a computer 31 to which is linked a keyboard and CRT display for entering required print parameters and for initial testing of the printer. Data is also received by 33 from transducers and switches 34. The variable data is passed as 7-bit parallel ASC11 words to nozzle electronics 35 wherein a matrix generator 550 converts them to 7 x 5 matrix form using the (suitably adjusted) signals STR1, STR2 which occur once for each character and for each character column respectively. The circuitry and pulses are duplicated for each nozzle. A video generator then converts the signals to pulses Y1-Y7 for each column X1-X5, Fig. 16, for application to a charging tunnel 558. A collector 564 catches uncharged drops; this is used with a sensor 570 to check synchronization of drop formation and charging. Control system 33 (Fig. 12).-This is described in detail with reference to Figs. 5-11 (not shown), and comprises the following components. The "top of form controller" includes a counter (169) which repeatedly counts pulses CP during 12À5 msec. intervals to determine the web speed. For the maximum speed of 700 ft./min., the ink drops must be released <SP>7</SP>/ 12  inch before the printing position is reached; for slower speeds, drop release is delayed by a time which is determined by presetting a counter (197) with the count in (169) and counting pulses CP until a maximum value is reached. The controller also includes counters (98-102) and logic circuitry connected to form depth switches for producing a control pulse which is used to initialize (169). Each group of five nozzles is controlled by "master head" and "head" controllers for nozzle 1 and nozzles 2-5 respectively. The Fig. 7 circuitry produces a PRINT REQUIRED signal (stop test mode, start print mode) 2 inches before the printing position is reached, to allow the correct voltage levels in the subsequent circuitry to be attained. It also produces signals STR1, STR2 for nozzle 1 using a pulse ASTR. Since each nozzle in a group is spaced 2¢ inches (300 pulses) from the preceding one, each Fig. 8 circuit counts to 300 upon receiving the previous ASTR pulse before producing its own pulse (and hence its own STR1, STR2 pulses and PRINT REQUIRED pulse) so that each nozzle can be correctly operated in turn. The Fig. 9 circuitry produces control signals when its nozzle reaches the end of its line, and the Fig. 6 circuitry produces control signals in response to control commands from the computer. The nozzle controllers receive the variable data from the computer, together with a PRINT READY signal; the data is received two words at a time and is transmitted one word at a time over lines L1-L7. Ink supply system 37.-A detailed description is provided with reference to Figs. 17, 18 (not shown, see Division B6).