GB191226195A - Improvements in Rotary Offset Printing Presses. - Google Patents

Abstract

26,195. Linotype & Machinery, Ltd., Pearce, H., and Parker, T. R. G. Nov. 14. Rotary machines; offset machines; tripping- arrangements.- Rotary offset machines of the kind that can be used for either perfecting or multi - colour printing are constructed with two printing or plate cylinders which each co-operate with a separate transfer cylinder arranged in conjunction with one or two impression cylinders. In all cases the machines are arranged so as to allow of easy accessibility to the plates for cleaning purposes. The cylinders are arranged in pyramidal form with the axes of the plate cylinders in an horizontal plane below the horizontal plane containing the axes of the transfer cylinders. As shown, the machine comprises two plate cylinders 1, 2, Fig. 1, above which are fitted two offset cylinders 6, 7 of half the diameter, and above this an impression cylinder 8 of the same size as the offset ones, the arrangement of the cylinders being such that the sections of the axes of the cylinders 1, 2, 8 on the plane of the paper form substantially an equilateral triangle, the oblique sides of which fall just inside of the axes of the cylinders 6, 7. When printing in two colours, the cylinder 8 receives one sheet for each two revolutions, and during one revolution it receives impressions from both cylinders 6, 7, and during the second revolution it is raised out of contact with both cylinders 6, 7. When perfecting is to take place, the cylinder 8 is fitted with an offset blanket, and during its first revolution it is moved into contact with cylinder 7 only so as to receive an impression on this offset blanket. During the second revolution, a sheet is fed to the cylinder 8, which is then moved out of contact with the cylinder 7 and into contact with cylinder 6, the perfecting operation taking place as the cylinders 6, 8 rotate in contact, the sheet being delivered from the grippers of cylinder 8 prior to the cylinders 8, 7 again being brought into operation. The tripping-mechanism for controlling the movements of the cylinder 8 for the two methods of printing described above, and for permitting the cylinder 8 to be tripped entirely in case a sheet is not fed is as follows. The cylinder 8 is mounted in eccentric bearings 12 in boxes 13, which can be raised and lowered by means of links 16, and eccentrics 17 connected by rods 20 to arms 21 on a rocking shaft 22. The boxes 13 are acted on by springs 14, which tend to raise them out of printing position. When multiple printing takes place, the shaft 22 is rocked in such a manner that the cylinder 8 is alternately raised and lowered, the bearings 12 remaining stationary relatively to the boxes 13. When perfecting takes place, the boxes 13 remain in their lowered position and the eccentrics 12 are rocked by lever and eccentric mechanism from a shaft 52. To control which of these trips is operative, a lever arm 66, Fig. 2, is moved so as to throw in operative relation (a) clutch elements 33, 35 which connect a freely-mounted arm 31, Fig. 3, with the shaft 22 when multiple printing is required, or (b) clutch elements 58, 59 which connect the shaft 52 with a freely-mounted gear 53 oscillated by cam-and-sector mechanism from the cylinder 2, and also clutch elements 36, 34 which connect an arm 32 to the shaft 22, thereby causing the shaft 22 to remain in the position in which the boxes 13 are in their lowered position. The arm 31 is fitted with a pawl 29 which engages an abutment 27 on a toothed segment 26, which is freely mounted on shaft 22 and is oscillated by cam-and-sector mechanism from the cylinder 1. A pin 48 on arm 31 is engaged by an abutment 28 on the segment 26, and normally, with the clutches set as shown in Fig. 3, the pawl 29 and pin 48 oscillate the shaft 22 to raise and lower the boxes 13 alternately. When a sheet is not fed to the cylinder 8, a pedal 42 is depressed, and this causes a cam 39, Fig. 4, to trip the pawl 29, and the cylinder 8 is left in its raised position or allowed to return thereto. The pedal 42 also serves to move a pawl 30 on the arm 32 into engagement with abutment 28, and so in the event of the pedal being depressed when perfecting is taking place, the abutment 28 acting on pawls 30 moves the shaft 22 to the position in which the boxes 13 are raised. In a modification, Fig. 10, an additional impression cylinder 88 is employed, the cylinders 1, 2, 6, 7, 8 being arranged substantially the same as shown in Fig. 1. With this machine, when perfecting takes place, the sheet is first printed between the cylinders 8, 6 and then between the cylinders 88, 7. For multi-colour printing, the cylinder 8 is fitted with an offset blanket and the sheet receives its first impression when passed between the cylinders 88, 8, and the second one from the cylindes 8, 6. The damping-mechanisms 71 and inking-mechanisms 72 are so arranged on the plate cylinders as to afford free access to the plates for cleaning purposes.