PURPOSE: To print patterns having different repeating length on a web without changing the diameter of a plate cylinder and to obtain printed matter having proper density by supplying a necessary amount of ink, by changing the peripheral speed of the plate cylinder having a printing plate mounted thereon and that of an offset roll in a predetermined ratio and allowing the peripheral speed of the plate cylinder to be inversely proportional to the change ratio of said speed to the running speed of the web to control the quantity of the ink on the printing plate.
CONSTITUTION: When a printing plate 244 and an offset roll 243 slip and the speed of a running web 210 is higher than the peripheral speed of a plate cylinder, a pattern P printed appears in a state extended in the peripheral direction at the time of printing as compared with the pattern P2 formed to the printing plate 244 by photoengraving and, in the opposite case, said pattern P appears in a contracted state. Therefore, even when the pattern P2 of the printing plate 244 is slightly magnified or contracted, the pattern P printed has no blur. When the dimension R of the pattern P printed in the peripheral direction is larger than the dimension R2 of the pattern P2 on the printing plate 244 in the peripheral direction, that is, a change rate is smaller than 1, the coating quantity of the ink on the printing plate 244 is increased slightly and, in the opposite case, the coating quantity of the offset roll is decreased slightly and the pattern P printed having hue with proper density of obtained.
YOSHIMATSU TATSUHIKO
TSUCHIMOTO HIDEYUKI
HIWATARI KATSUMI
Next Patent: B-B TYPE PRINTING UNIT WITH SPOT COLOR DECK