GB845788A - Improvements in or relating to printing machines - Google Patents

Abstract

845,788. Feeding webs. GEORGE & MILLER Ltd. Dec. 24, 1958 [Jan. 7, 1958], No. 647/58. Class 100(1) In a rotary printing machine for printing on paper web having rows of holes at their edges and including a continuously rotatable printing cylinder 11, a continuously rotatable impression roller 15 and a pin wheel drive 22 for drawing away the paper web from between the rollers 11, 15, the impression roller 15 and the pin wheel drive are arranged to rotate respectively with the transmitter and slave units 36, 37 of a magslip device, the impression roller and printing cylinder being arranged to release the web at least once during each revolution of the printing roller and the magslip transmitter unit 36 being arranged to transmit rotation to 'the slave unit 37 only during a predetermined part of each revolution of the printing roller so that the drawing away of the paper web by the pin wheel drive takes place only during that part of each revolution of the printing roller, the arrangement being such that during that part of each revolution the printing takes place. The paper web is fed into the nip of the printing cylinder and impression rollers over supports 18 and between guides 19 and at the delivery end of the machine passes over supports 23, the pin-wheels 22 engaging the marginal holes in the web which is held in engagement with the wheels by guides 24. The pin-wheels 22 are keyed to a shaft 40, the keys slidably engaging slots 54 in the shaft. The hubs of the wheels are rotatably mounted in one end of arms 56 which at their other ends carry nuts, the nuts engaging left- and right-hand threaded portions respectively of a rod 55. The guides 19 are carried by nuts mounted on another right- and left-hand threaded rod 58 coupled to the rod 55 by a sprocket chain 59 so that when the rod 55 is rotated by means of a knob 63 the sprocket wheels and guides 19 move transversely of the machine towards or away from each other to accommodate varying sizes of web. The shaft 40 is driven by the slave unit 37 of the magslip device. The transmitter 36 of the magslip device is driven through gearing from the impression roller 15 which is itself driven by an electric motor. The printing cylinder 11 is driven through gearing from the impression roller. A printing plate 12 mounted on the periphery of the cylinder 11 does not completely surround the cylinder and the paper is gripped between the printing cylinder and impression roller only when the plate 12 is adjacent to the impression roller. Current is fed to the transmitter of the magslip device through one of a number of circuits each of which includes a two-way microswitch 43 actuated by a cam 45 carried by the printing cylinder shaft. The ends of the raised portion of each cam 45 subtend the same angle at the axis of the printing cylinder as do the ends of the several sizes of printing plate which may be used and the microswitches 43 are adjustable circumferentially about the cams 45. A microswitch circuit is chosen whose controlling cam corresponds to the plate 12 mounted on the cylinder 11. As the paper web is printed by the plate 12 the microswitch 43 is held closed in one position to energize the magslip device by the cam 45 so that the rotation of the impression roller is transmitted to the shaft 40 of the pin wheel drive by the magslip device. As the end of the plate leaves the web after making an impression the microswitch 43 is moved to its other position in which the circuit to the magslip device is opened and that to an electro-magnetic brake 44 operating on the shaft 40 is closed. The pin-wheel drive to the web is thus immobilised until the leading end of the printing plate reaches printing position again. In this way successive impressions are correspondingly positioned with respect to the holes in the web, and the machine may be used for overprinting additional matter on previously printed paper. In a modification two or more printing plates are secured to the cylinder 11 and the cams 45 have two or more corresponding raised portions.