GB876838A - Improvements in or relating to lithographic printing machines - Google Patents

Abstract

876,838. Printing machines. RITZERFELD, W., and RITZERFELD, G. Nov. 11, 1959 [Nov. 26, 1958], No. 38182/59. Classes 100(1) and 100(2) In a lithographic offset printing machine the offset cylinder is moved into contact and away from the forme cylinder during a first rotation of the latter, the timing of these movements being determined by setting means to correspond with selected lines or text portions on the printing plate, and during a further rotation of the forme cylinder the offset cylinder and an impression cylinder co-operate to effect printing on a sheet in a closed up manner of the selected lines or text portions. As shown, the power-driven shaft 1 of the forme cylinder 2 carrying a printing master sheet 23 is coupled by gears directly to the impression cylinder 7, and indirectly through a magnetic clutch 13 to the offset cylinder 14. Associated with the cylinder 2 there is an electric contact for each line on the master sheet 23 and settable from a keyboard, and a contact arm rotates with the cylinder to engage those contacts which are set up and thus cause an electromagnet 17 to act through a linkage 18, 19 to draw the offset cylinder 14 into contact with the sheet 23. In the engaged positions of the cylinders 2, 14, gears 22, 21 thereon are in mesh. After each line is transferred to the cylinder 14 the latter is spring-urged away from the cylinder 2 so that the gear 21 is engaged by a spring-loaded rack 43 which arrests the cylinder 14. When the forme cylinder 2 has completed one rotation, a contact is operated to cause an electromagnet 45 and link 46 to draw the rack 43 away from the offset cylinder, and a further electromagnet 148 is de-energized. A spring-urged arm 50 can now urge the offset cylinder 14 against the impression cylinder 7, and the magnetic clutch 13 is, operated to cause the cylinder 14 to be power-driven to print on a copy sheet on the cylinder 7. The printing master sheet 23 is inked by apparatus 78-82, and damped by apparatus 73-77. Feeding sheets:-Sheets 24 are fed from a pile by a sucker 25 and an oscillating sucker arm 31 on each third rotation of the forme cylinder 2, the arm 31 being connected by a resilient link 57. to a rotating crank plate 16. The sheets are taken by grippers 52 on the cylinder 7, and delivered to a rotating sucker arm 10 which drops them on to a pile at 55. If a sheet is not accurately registered against a sheet holder 29, operable by an electromagnet 59, two photo-cells 32 cause suction to be cut off from the arm 31, and also start a motor 33 to drive a cam disc 36 for one revolution only, which through a link and roller 37, retracts the cylinder 7 from the offset cylinder 14. Set-off, preventing.-After each printing rotation of the cylinder 14, the electromagnets 17, 45 and magnetic clutch 13 are controlled to allow a free running of the cylinder 14 for cleaning. This cleaning is effected by a cam controlled roller supplied with a liquid from a bath.