GB737513A - Improvements in and relating to sheet-fed offset lithographic printing machines - Google Patents

Abstract

737,513. Printing-machines. ROTAPRINT, Ltd., [formerly KAYES ROTAPRINT AGENCY, Ltd.]. May 28, 1954 [June 10, 1953], No. 16046/53. Class 100 (2). Tripping-arrangements.-In an offset lithographic machine means is provided whereby when the offset cylinder is tripped relatively to the impression and printing cylinders the sheetfeeding means can be rendered operative by the actuation of a hand-lever or foot-pedal so that sheets can be fed through the machine for test &c. purposes without the necessity of removing and remounting the printing-plates. As shown, the shaft on which the offset cylinder 2 is rotatably mounted has eccentric ends 4 mounted in the machine frame, one of which has secured thereto a support 5 having two links 6, 7 pivoted thereto. The links are connected by a crosslink 8, and an arm 9, secured to the link 6, carries a roller 10 which co-operates with a fixed plate 12 having arcuate abutment surfaces 13, 14. A lever 15, pivoted intermediate its ends to the arm 9, has a hook-nose 16 adapted to engage a shoulder 19 on a cam projection 18 on the cylinder 2, and a tail 17 provided with a stud 17a adapted to be engaged by a lever 22 which is rigid with a link 21 pivoted to a pushrod 20. Before printing, and the rotating cylinder 2 not in contact with the rotating forme and impression cylinders 1, 3, respectively, the push-rod 20 is depressed to the position shown so that the lever 22 forces the nose 16 of the lever 15 to engage the shoulder 19 on the cam 18. As the cylinder 2 rotates, the lever 15, attached links, and eccentric shaft end 4 are carried round with the cylinder to a position where the roller 10 engages the first arcuate surface 13, and the tail 17 of the lever 15 strikes a stop 24 to cause the nose 16 to leave the shoulder 19. A tension spring 23 now pulls on the links to cause the roller 10 to enter the second arcuate surface 14; in this position the cylinder 2 now contacts the cylinders 1, 2 for printing. The sheet-feeding means is driven by a gear 24, loosely mounted on the shaft 3a of the impression cylinder 3, adapted to be driven with the cylinder 3 when a lug 27 on a pawl 25 pivoted on the gear engages a notch 28a in a member 28 secured to the shaft 3a. Normally, with the cylinder 2 tripped-off, a slidable bar 29 prevents such engagement, the bar being slotted at 30 to engage over a pin 31 on the member 5; but when the push-rod 20 is depressed, the member 5 rotates to withdraw the bar 29 to allow the sheets to be fed. To allow the sheets to be fed with the cylinder 2 trippedoff, one arm 32a of a bell-crank lever pivoted at 32 is pivoted at 33 to the bar 29, so that hand or foot pressure exerted on the other arm 32b slides the bar to allow the lug 27 to engage the notch 28a; the slot 30 ensures that the member 5 is not moved by this operation. Specifications 728,737 and 729,548 are referred to.