Patent GB-1107395-A (GB)
Title: Printing method and rotary duplicator for use therein
IPC: B41L11/00
Filed: 1965-06-01
Abstract: 1,107,395. Printing. AGFA A.G. 1 June, 1965 [5 June, 1964], No. 23309/65. Headings B6C and B6H. In a method of printing wherein an ink containing magnetizable particles is employed, and ink is transferred from a printing element to a sheet to be printed or ink is applied to the printing element by electromagnetic forces, the means for producing the electromagnetic forces can be controlled so that printing of the whole or selected parts of the printing element can be effected. In one construction, Fig. 1, the sheets are fed over a fixed table 30 and beneath an offset cylinder 10 by a reciprocated one-way rotary roller 25 and by feed rollers 27-29, geared to the cylinder 10. Beneath the table 30 and arranged transversely to the direction of sheet feed are a series of electromagnets 33a, &c., and a similar series of electromagnets 36a, &c., are fixed inside the cylinder opposite to the first series so that energization of the magnets causes a magnetic field to be created which effects transfer of the ink from the cylinder 10 to the sheet. Thus, if one or more of the pairs of opposed magnets are energized for a limited period, a part of a line or a whole line of matter is printed on the sheet whereas if one pair of opposed electromagnets is energized a column or part of a column may be printed depending on the length of time of energization. To select the parts to be printed, each pair of opposed electromagnets 33a, 36a, is connected by a line 18 to a shaft 40 driven from the offset cylinder 10. Rotating with the shaft 40 are fingers 16a-16d, one finger for each pair of opposed electromagnets. Each finger 16a, &c., moves over a series of contacts 17a-17c &c., each series being associated with a series of Keys T1-T3 &c., which if depressed operate switches 20a-20c to connect the respective contacts 17a-17c to mains 21, 22. Thus, depression of a single Key T1 causes energization of the corresponding pair of electromagnets 33a, 36a and the printing of part of a line or column, depression of a line of Keys T1 or T2, &c., causes a complete line to be printed and depression of a series of Keys T1-T3 causes a column to be printed. Other variations of the matter printed can be obtained by depression of the Keys corresponding to such matter. In a second embodiment, Fig. 3, an offset cylinder 10 is again employed, but the electromagnets 47a, &c., are carried by a rotary cylinder 47 over which the sheets pass. The selection of the electromagnets to be energized is effected by Keys T 1 -T 3 , &c. as in the first construction. The cylinder 47, however, only rotates a distance corresponding to a line or number of lines selected by the Keys T1-T3 and for this purpose is driven by a belt 53 from a roller 54 carried by a lever 57 and normally resting on a brake pad 63. If, for example, a Key T1 is depressed, then when a finger 16a- 16d &c., reaches a contact 17a, an electromagnet 59 is energized and actuates the lever 57 so as to move the roller 54 into engagement with a constantly rotating roller 52 to cause the cylinder to rotate a distance corresponding to one line. The sheet to be printed moves with the cylinder 47 and for this purpose is fed to a gripper 46 on the cylinder from which it passes beneath a delivery roller 51 in contact with a stripper plate 50. The offset cylinder 10 is driven continuously for one revolution when an operator-actuated lever 68 is depressed, the lever 68 releasing a catch 66 to allow a roller 56 driving the cylinder 10 through a belt 55 to be moved by a spring 62 into contact with the driving roller 52. When a revolution of cylinder 10 is completed, a finger 16a-16d engages contacts 79, 80 causing an electromagnet 60 to be energized to move roller 56 into engagement with a brake block 64, the rotation of cylinder 10 thus being stopped. At the same time, the electromagnet 59 is energized to move roller 54 into engagement with roller 52 so as to rotate the cylinder 47 and complete delivery of the sheet. When the cylinder 47 has completed one revolution, cams thereon open contacts 83, 84 and release the electromagnet 59. In a third embodiment, (Fig. 7, not shown) which is somewhat similar to that shown in Fig. 1, the offset cylinder 10 is driven by a belt (55) from a pulley concentric with a driving roller (56) mounted on a lever (58). The driving roller (56) engages a driven roller (52) to drive the offset cylinder 10, but during printing of a line or part thereof caused by actuation of e.g. keys T1, &c., an electromagnet (115) is energized and by means of latch and lever mechanism (109, 110, 112) moves the driving roller (56) downwardly into engagement with a brake block (116) to stop the cylinder rotation temporarily whilst printing is being effected. According to a modification, each pair of magnets such as 33a, 36a, Fig. 1, may be replaced by a single horse-shoe type of magnet, mounted in the sheet-supporting table. In another construction, Fig. 4, a lithographic plate cylinder 92 with a forme 91 having a magnetized image thereon is inked by a roller 93 to the surface of which ink is applied. The cylinder 92 is damped by a roller 8 so that ink adheres only to the magnetized image on the cylinder. The inking roller 93 has electromagnets 93a mounted therein which can be selectively energized by means of Keys T 1 -T 3 , &c., as already described. Energized electromagnets 93a nullify the magnetism of the forme so that parts of the magnetic image selected by the Keys receive no ink. The transfer of the ink from the forme 91 to the paper sheet may be effected under additional electromagnetic control means. According to a further embodiment, (Fig: 6, not shown) magnets (35, 104) are selectively energized as already described to control the passage of ink from the plate cylinder 1 to the offset cylinder 10, printing of the sheet taking place in the normal way between the cylinder 10 and an impression cylinder (106). After each revolution of the offset cylinder 10, a magnetic cleaning device removes the ink from the cylinder so that a different combination can be set up for printing during the next revolution. In this construction the printing plate (107) is of magnetizable material with a resilient backing (108), and is pulled by the magnetic forces towards the cylinder 10 at the printing point to reduce the air gap.