Patent GB-633516-A (GB)
Title: Improvements in or relating to the method of, and press for, rotary offset printing
IPC: B41F7/06
Filed: 1947-08-13
Abstract: 633,516. Printing-machines. HARRIS-SEYBOLD CO. Aug. 13, 1947, No. 22508. Convention date, Aug. 28, 1946. [Class 100 (ii)] In a multi-colour rotary offset printing- machine, lack of register between successive impressions due to lengthening of the paper by the printing operation is obviated by so driving the printing-couples that the printed impression is lengthened slightly at each successive impression. In one form, Figs. 1, 2, and 6, in which the impression cylinders 22 are connected by sheet transfer cylinders of double the diameter of the cylinders 22; each cylinder 22 is driven by gearing 23<SP>1</SP>, 28, and the offset and plate cylinders 21, 20 are driven from the impression cylinders by gears 33 engaging gears 32 on the offset cylinders which engage gears 31 on the plate cylinders. The gears 33 are connected to the cylinders 22 by means which varies their speed relatively to the cylinders, so that the speeds of the offset cylinders differs slightly from that of the impression cylinders in such a way that the impression received is slightly longer than would be obtained if the gears 33 were fixed to the cylinders 22. Each gear 33 is connected to its driven cylinder by yieldable connections 69, 70, 72, 73, and by means of an adjustable crank-pin 55, Fig. 6, engaging a slide 56 arranged in a slot 57 in the cylinder 22. The pin 55 is actuated by a fixed cam 38, Fig. 2, surrounding the shaft 27 of the cylinder 22. The cam 38 oscillates a lever 40 carried by a rack-shaft 46 which is mounted in a hollow boss 47 integral with wheel 33. The position of pin 55 is adjustable by means of an eccentric pin 51 carried by an adjustable shaft 48 which can be adjustably secured to rock-shaft 46 by rotation of a graduated disc 58 after loosening a screw 49 which can be operated by a tool inserted in a slot 50. If the pin 55 is set concentric to the shaft 48 the gear 33 and cylinder 22 rotate in unison, but normally the pin is set so as to cause the gear 33 to be retarded gradually during the greater part of the rotation of the cylinder so that the offset cylinder moves slightly slower than the impression cylinder with consequent lengthening of the printed impression. As the cam roller 39 mounts to the high part of cam 38, which occurs as the gaps in the cylinders 21, 22 register, the lever 40 is reversed and the cylinder 22 and gear 33 return to starting position, the gear 33 being accelerated instead of retarded. In a modification, Fig. 10, the impression cylinder 80 is positively driven and is geared to the offset cylinder 84. Motion is transferred to the plate cylinder 82 from cylinder 84 by means of a gearwheel which during rotation is adjustable relatively to the cylinder 84 by the rocking of a lever 106 by a fixed cam in a manner similar to the adjustment of the gear 33, Fig. 1, so that in this case the plate cylinder 82 is driven at a, different speed from the offset cylinder 84 during the transfer of the impression to the offset cylinder, and a longer impression is produced than would be produced if the cylinders were connected by fixed gears.