Patent GB-245875-A (GB)
Title: Improvements in set-off web feeding devices in flat-bed web printing machines
IPC: B41F23/06
Filed: 1924-10-29
Abstract: 245,875. Cossar, T. Oct. 29, 1924. Fe e d i ng, winding, and registering webs. - Means for feeding a set-off web in flat-bed printing-machines, of the kind described in Specification 28998/10, comprise con. stantly driven friction rollers, adapted to draw off the web from a roll, and continuously driven winding-rollers, rotating at a slightly higher speed than the draw rollers, differential gearing controlled by a floating tension roller being provided to govern the speed of the winding-rollers. Alternately operating looping-rollers serve to take up the slack web during the printing periods. The set-off web S is drawn from a roll 1, carried in vertically adjustable bearings 2, by constantly driven draw-off rollers 7, 8, the web passing round the rollers 7, 8 and a horizontally moving looping-roller 46 carried in pivoted arms 47. From the roller 46, the set-off web S passes over a guide roller, mounted in vertical slotted bearings, between the printed web and the impression roller, under a second guide roller situated at the further end of the bed, round a second, vertically moving looping-roller, under and over third and fourth guide rollers, under a tension roller 43, and finally over a constantly driven winding-rotter 12 to the winding-roll 13. The roller 12 co-operates with a similar roller 11, both being driven at a slightly greater speed than the rollers 7, 8. The tension roller 43 is carried by arms 41 pivoted at 42, one of the arms being connected by an extension 40 to a sliding rod 39 provided with cam faces adapted to operate a belt fork serving to move a continuously driven belt from a loose to a fast pulley, or vice versa, on a shatt 27 connected by bevel and worm gearing to a differential mechanism controlling the speed of the winding-rollers 11, 12. The arrangement is such that, when the roller 43 is above a certain position, the belt is moved on to the fast pulley and the differential mechanism is operated to slow down the winding-rollers 11, 12 below the speed of the draw-off rollers 7, 8, and when below a certain position the belt is moved on to the loose pulley, the winding-rollers then being driven at their normal speed. Over-running of the shaft 27 carrying the pulleys is prevented by brake shoes 45 co-operating with a drum 44 on the shaft; a hand wheel is also provided on the shaft 27 to allow manual operation of the differential gear. The looping-rollers are operated by link and cam mechanism driven in synchronism with the impression rollers so that, during the printing period, the slack in the web S is taken up from the feed rollers by the looping-roller 46, the second loopiug-roller being so moved as to allow the web in this loop to be taken up by the winding-rollers. During the inactive period of the impression cylinders, the reverse movements of the looping- rollers cause the set-off web S to be fed forward to bring a clean portion over the printing bed. When feeding in a new printing web or the end of a broken web, the guide roller carried in the slotted bearings is raised to the top thereof to lift the set-off web S, the draw-off rollers 7, 8 being disconnected by moving a sliding pinion out of gear in the driving train and rotated by a hand-wheel provided for this purpose. Similar disconnecting gear is provided on the main drive and the drive for the winding-rollers. which are provided with a hand-wheel for manual operation. When the main driving-gear has been disconnected, the set-off mechanism can be driven independently of the printing-mechanism by belt gearing or by an electric motor. To exchange a full rewound roll 13 for an exhausted roll 1, the web is severed from both rolls, the roll 13 is rolled over a platform 15, situated between the two sets of rollers 7, 8: 11, 12, to the lowered bearings 2, and the ends of the remaining web attached to the respective rolls.