Patent GB-448896-A (GB)
Title: Improvements in or relating to rotary printing presses
IPC: B41F27/10
Filed: 1935-01-24
Abstract: 448,896. Printing-surfaces. JACKSON, L. MELLERSH-, 28, Southampton Buildings, Chancery Lane, London.-(Goss Printing Press Co. ; 1535, South Paulina Street, Chicago, U.S.A.) Jan. 24, 1935, No. 2391. [Class 100 (ii)] Apparatus for maintaining a stereotype printing-plate in good printing condition at high operating speeds comprises fixed means for holding the plate securely on a plate cylinder along its leading end, and means at its trailing end for resiliently tensioning the plate around the cylinder so as to take up stretch of the plate resulting from the printing pressure. The apparatus may provide positive tensioning means when first clamping the plate on the cylinder and resilient tensioning means for taking up stretch of the plate during printing. The stereotype plate 7, Fig. 7, is formed with longitudinal lugs 9 ... 11, which are bevelled slightly from their roots inwards and also longitudinally, to facilitate removal of a cast plate from the casting machine. When in position on a printing cylinder, the lugs 9 rest with their appropriately curved inner surfaces on the cylinder surfaces while the lugs 10, 11 are engaged by the holding and tensioning means, being formed with their operative faces disposed at an angle and non-radially of the plate, so as to prevent displacement thereof in any direction. The cylinder 1, Figs. 1 and 5, is formed with an inclined, undercut and longitudinally disposed groove 17 for engaging with the lug 10 which is at the front end of the plate, while the lug 11 on the trailing end is engaged by the tensioning means. This comprises an actuating bar 20 mounted in a slot in the cylinder and adjustable therealong by operating a rod 24 which is held against movement on the cylinder but is in screw-threaded engagement with the bar 20. A bar 29 for engaging the lug 11 of the plate is mounted on pins 34 which move in inclined slots 39 formed in blocks 37 slidably arranged in recesses in the bar 20 and controlled by compression springs 40, and the device is held in the cylinder slot by clips 41 which extend over the actuating bar 20 and engage recesses 42 in the member 29 so as to permit the latter to move circumferentially. A plurality of plates may be arranged round the cylinder and also along its length, and in the latter case a single actuating means for the plate-locking and tensioning means is provided by uniting two actuating bars 20 to permit adjustment of their relative position by a screw rod 49, the opposite ends of which are oppositely threaded to engage lugs 47, 48 on the two bars 20 and which can be adjusted by a turning head 50. To clamp a plate, the screw 24 is turned so that a jaw 30 on the member 29 engages the lug 11 and presses it back towards the lug 10 which is fixed in the slot 17, thereby positively tensioning and clamping the plate, the springs 40 being at the same time compressed until they are substantially solid. As the plate stretches during printing, the springs expand and move the member 29 circumferentially to maintain the tension and provide an equal tension at spaced-apart points along the trailing end of the plate. In a modification, the cylinder 110, Fig. 8, is provided with spaced apart clips 115 formed with projecting undercut parts 116 adapted to engage with the forward edge of an undercut recess 112 at the forward end of the printing plate 111, while the recess 112 at the trailing end of the plate is engaged by spaced movable clips 119 which are keyed to a common shaft 118 and which are resiliently urged to tension the plate by springs 121 compressed between recesses in the cylinder and cups 122 pivotally connected to the clips. The clips may be released simultaneously by rotating the shaft 118. The recesses 121 are preferably narrow and do not extend right across the cylinder but are positioned to engage with the plate securing clips and are uniformly arranged at each end of the plate so that the latter may be reversed on the cylinder, if desired.