Patent GB-849273-A (GB)
Title: Improvements in or relating to rotary sheet-printing machines
IPC: B41F11/00
Filed: 1956-10-22
Abstract: 849,273. Rotary sheet-printing machines. MURRAY, W. E., and DAVIDSON, W. W. Oct. 22, 1956 [Oct. 28, 1955], No. 32048/56, Classes 100(1) and 100(2) A rotary sheet-printing machine has a printing couple in which one cylinder is arranged above the other, the top cylinder having a diameter larger than and wholly divisible by the diameter of the smaller bottom cylinder thereby to provide a number of separate work areas around its periphery with the arcuate spacing distance between the centres of said areas substantially equal to the circumference of the bottom cylinder, and a copy sheet gripper system arranged for movement around an endless path which encircles the bottom cylinder and passes through the bite of the printing couple, and in which the feeding-in of the copy sheets to and the discharge of copy sheets from the machine takes place in a substantially horizontal direction. The press can be adapted to print in one, two, three, or four colours, and for performing lithographic offset and letterpress operations. The operations include printing a sheet by two-colour letterpress or offset on one side, four-colour letterpress or offset on one side, two-colour offset on each side, three-colour letterpress or offset on one side, and two-colour offset on one side and one-colour offset on the other side. Essentially, there is a basic press or couple, to which further units may be added, comprising a small impression cylinder which may also act as an offset cylinder for printing on the reverse side of a sheet, and a larger cylinder which has two or more separate work areas thereon, these areas comprising printing plates, offset or impression surfaces, or a combination of these. The diameter of the larger cylinder is two, three, four or more times the diameter of the smaller (impression) cylinder. Associated with each smaller cylinder is a gripper sheet feeding means having an even number of sheet gripper sets when the periphery of the larger cylinder has an odd number of work areas thereon, and an odd number of sets when there are an even number of work areas. Some of the various modifications of the press are shown diagrammatically in Figs. 31 and 32. Fig. 31(a) shows the basic two-cylinder press wherein the lower cylinder is one-half the diameter of the larger cylinder, the latter bears a printing plate A and an impression area IMP, and there are three grippers x, y, z on endless chains which feed the sheets between the cylinders. The lower cylinder acts as an offset cylinder and the sheet is passed once through the couple and is printed by offset on the lower side only. By arranging two plates on the upper cylinder, the upper side of a sheet is printed in two-colour letterpress, but the sheet passes through the couple twice. By having an upper cylinder which is three or four times the diameter of the lower, and varying the number of plates and impression areas thereon, it is possible to print in two-colour offset on one sheet side or three or four colour letterpress on one side. In Fig. 31 (c) two basic two-cylinder presses are arranged in "tandem" to print fourcolour letterpress on one side of a sheet. The sheet passes alternately through the two couples twice. If instead of the four letterpress plates A, B, C, D, each larger cylinder has one plate and one impression area, a sheet can be printed two-colour offset on the lower side. Fig. 31(e) shows a three-cylinder press with an intermediate larger cylinder having offset areas A<SP>1</SP>, B<SP>1</SP>, for receiving offset impressions from plates A, B on the upper larger cylinder. A sheet can be printed on the upper side by two-colour offset, and passes twice through the printing couple. For two-side offset printing, the upper cylinder has a single plate, and the intermediate cylinder one plate and one offset area. Four-colour offset on one side of a sheet, or two-colour offset on each side, or three-colour offset on one side, or two-colour offset one side and one-colour offset on the other side, can be arranged by a manipulation of the working areas on the two larger cylinders, and by having the smaller cylinder of a diameter one-third of the other cylinders. Another modification, Fig. 32(g), shows two three-cylinder presses arranged in tandem. Each printing couple comprises a smaller blanket cylinder, two offset areas (A<SP>1</SP>, C<SP>1</SP> and D<SP>1</SP>, B<SP>1</SP>) on each intermediate cylinder, and two printing plates (A, C and D, B) on the upper cylinders. A sheet passes through each printing couple twice, and is printed on one side in four-colour offset. By a different arrangement of plates &c. a sheet can be printed in two-colour offset on each side. Fig. 1 shows a three-cylinder press comprising a basic press having a large cylinder 50 with two work areas 51, 52 and a blanket cylinder 53 of smaller diameter, plus a second large cylinder 84. The cylinders are driven from a motor-driven main shaft by a gear train located on one side of the machine. Sheets from a pile 100 are conveyed by belts 105 to a short table 103 where a dropping-roller feed forwards them to one of the sets of grippers 71, 72 or 73 on endless chains 70 which feed them between the bight of the cylinders 50, 53 one or more times. The third cylinder 84 is mounted in removable frames 83 which form an extension of the basic frames 57 of the press. Oldham couplings allow the cylinders 53, 84 to be tripped from the cylinder 50 without the disengagement of the gear train. In a modified three-cylinder press (Fig. 34, not shown) sheets are fed through the printing couple one or more times by grippers on the smaller cylinder and are then released to grippers on delivery chains. The bottom smaller cylinder and the upper cylinder are driven through Oldham couplings and both can be tripped off the intermediate cylinder automatically. The sheet-feeding means is substantially the same as that shown in Fig. 1, but the sheet-sensing finger and tripping mechanism is modified slightly. Fig. 47 shows two three-cylinder presses 535 and 543 of the type just described but arranged in tandem. Sheets are transferred from one printing couple to another by a transfer chain and gripper system 542. In this machine, in the cases where the sheets are to have multiple passage through a printing couple, such operation is completed at the first couple and the sheets are then transferred for a similar operation by the second printing couple. In the three-cylinder press 600, Figs. 48 and 49, sheets are passed through the printing couple by a rigid ring-type of encircling gripper means 626, and the cylinders of the printing couple can be separated when a sheet is absent, or as required for printing purposes, to two positions to suit offsetting between the cylinders, or printing on paper passing between them. As shown, there are two larger cylinders 601, 602 of like diameter, and a smaller blanket cylinder 603, but it may comprise the cylinders 602 and 603 only. The cylinders are geared together and are driven by a motor 612 through a belt 613 and pulleys, a drive shaft 616, and an idler gear meshing with a gear 619 on the cylinder 603. A sheet-feeder 625 advances sheets to the encircling gripper means 626, and the printed sheets are delivered on a pile at 628 by means 627. A four-colour machine comprises a pair of printing couples similar to that shown in Fig. 49, each including two larger cylinders of like diameter and a smaller cylinder disposed beneath such larger cylinders, the two couples being arranged in substantial V-formation. The two couples are serviced by a common encircling gripper system of the ring type. Feeding sheets; conveying sheets in machines; grippers:-Sheets on a table 100, Fig. 1, are fed by known suction means on to a belt conveyer 105 and conveyed up to stops on a short table 103 to lie between a lower driven roller 108 and a dropping roller 107. The roller 108 is driven by an arcuate gear rack which is oscillated by a cam on the shaft 56 of the cylinder 50. The roller 107 is lowered periodically on to the lower roller 108 by a further cam on the shaft 56 so that the sheets are fed to one of the set of grippers 71, 72, 73 on endless chains 70 which carry the sheets one or more times between the bight of the cylinders 50, 53. The roller 107 engages the roller 108 through a variable and yielding means. If a sheet is not present on the short feed table 103, a sensing finger 147, Fig. 8, falls under gravity through a slot in that table. This finger is loosely pivoted to an arm 145 on a shaft 142 which is rocked by the cam on the shaft 50 which lifts the dropping roller 107, and normally rides over the sheets. If the finger falls through the slot in the table 103 it engages and rocksa crank 149 secured to a shaft 150 beneath the table, which initiates means to trip the cylinder 53. Each gripper set 71, 72, 73 on the chains 70 comprises a cross-bar secured to the two chains and having a number of spaced gripper fingers secured on a shaft which is rocked periodically to grip and release a sheet by a stationary cam. Where selective operation of the grippers is necessary to allow a sheet to pass more than once through a printing couple, automatically operated means is provided for displacing the said stationary cam periodically so that the grippers are only opened at the appropriate times. This automatic means comprises a cam rotatable with the cylinder shaft 56 and adapted to operate wedging means to slide the stationary gripper cam axially. Sheet registration is effected by providing pins on the chain sprocket wheels which are adapted to enter V-shaped blocks on the gripper bars. Sheets passing into the grippers first abut a finger or stop which is urged upwardly and radially of the blanket cylinder by a cam thereon. This finger is adapted to pass through a recess in a gripper bar. In the modified sheet feeding and registering ap