Patent GB-910627-A (GB)
Title: Printing plates and methods and apparatus for forming them
IPC: B41F27/12
Filed: 1960-10-21
Abstract: 910,627. Printing plates. AMERICAN TYPE FOUNDERS CO. Inc. Oct. 21, 1960 [Nov. 12, 1959], No. 36255/60. Class 100 (2). A lithographic plate 50 for application to a plate cylinder 20 of the type having a longitudinal gap in the cylindrical surface thereof with means located in the gap adapted to grip the tail and leading edges of a flexible plate wrapped around the cylinder is prepared by bending a flange 54 at the tail edge of the plate for engagement by the gripping means in the gap, bending a hook flange 52 at the leading edge of the plate for engagement with a correspondingly angled edge of the gap and impressing on the plate a curvature 55 of a radius less than that of the cylinder throughout a small arcuate extent immediately adjacent the hook flange. A jig for bending the plate comprises base blocks 61, 62, Fig. 5, mounted on runners 63 for adjustment relative to each other in order that the length of the plate may be accurately determined to conform to the circumference of the cylinder. The block 61 is formed at its outer extremity with a ledge 65, Fig. 7, which is rounded at the apex 66 and is curved at 70 in order to form the plate curvature 55. A bending bar 80 having a handle 86 is pivotally mounted, through brackets 81 and pintles 76 carried by brackets 72, at this extremity of the block 61 in association with a clamping bar 90 which has a lower surface 91 conforming to the curved portion 70 of the ledge 65. The bar 90 is clamped through vertical screw members 95, 96, Fig. 12, threadedly mounted in the brackets 72 which are secured to each side of the block 61. The block 62 carries a clamping bar 110, Fig. 11, which is similar to the bar 90 and has a similar clamping arrangement comprising screw members 95<SP>1</SP> and 96<SP>1</SP>. In order to make the double bends 53, 54 in the tail end of the plate a structure comprising a handle 146 and bars 125 and 140 is pivotally mounted on pintles 127 at the outer extremity of the block 62. Surfaces 136 and 142 of the bars 125 and 140 co-operate, in operation of the jig, with inclined surfaces 130 and 132 of the block 62. Prior to the bending operation the plate P, Fig. 12, is properly positioned in the jig by the aid of gauge devices. Bridging the gap between the blocks 61, 62 are fixed plates 150 having inscribed markings 151 projecting beyond the plate margins. Similar markings are incribed on the plate and these are brought into registration with the markings 151 on the plates 150. Four further gauge devices are employed, each comprising optical means in which alignment has to be effected between crosshairs 177 carried in a tube 158 supported on a bracket 160, 161, 162 or 163 and cross-marks 187 on the plate P. The bracket 160, 163 is fixedly mounted through dowels 169 and a bolt 168 on either block 61 or 62 and the accurate positioning of the crosshairs 177 may always be checked by aligning with cross-marks 167 inscribed on a block 166, fixedly let into the surface of the block 61 or 62. In operation, the plate to be bent is accurately positioned prior to securing to the blocks 61, 62 by the clamping bars 90 and 110. The required bends are then made by swinging the bending bars 80 and 125, 140 about their respective pivotal axis.