Patent GB-217261-A (GB)
Title: Improved method of and apparatus for curving, or changing the curvature of printing plates
IPC: B41D5/00
Filed: 1923-01-11
Abstract: 217,261. Claybourn, L. W. Jan. 11, 1923. Printers' apparatus.-A method of curving or changing the curvature of printing plates consists in heating the plate to render its backing pliable and then bending the plate to the required curvature between a pair of resilient bands. The apparatus for carrying out the method comprises an internally heated segmental mould round which the bands and interposed plate are strained while the plate is being heated, and a second segmental mould, internally cooled, of a curvature substantially the same as that to which the plate is to be bent, to which the bands and heated plate are transferred and round which they are strained to effect the bending and cooling of the plate. Plates which have become hard in use are annealed while being treated. The invention is particularly applicable to printing plates comprising an electrotype shell strengthened by a backing material consisting of an alloy of 90 parts by weight of lead and 5 parts by weight each of tin and antimony. Fig. 5 is a front elevation and Figs. 8 and 10 are sectional views of an apparatus for increasing the diameter of the printing plates. The moulds 44, 191 have curvatures substantially equal to the initial and final curvatures of the plate and are removably secured to a carriage 211 slidable on the frame of the apparatus to bring the moulds alternately beneath a pair of spring steel bands 61, 62 between which the plate 31 to be treated is held. The rear end of the outer band 62 and the front end of the inner band 61 are fixed to bars 91, 63 respectively to which are secured brackets 101, 67 connected by rods 102, 69 to collars 107, 80 freely mounted on a shaft 79 which is movable vertically to tension and release the bands by screw and bevel gearing operated by a handwheel 159. Rollers on the ends of the bars 91, 63 engage inclined guides 140, 216 to cause the ends of the bands to approach one another when they are tightened about the moulds. The rear end of the band 61 is connected by springs 87 to collars loose on the shaft 79, and can be yieldingly clamped to the bar 91 by eccentrics 98 on a shaft 95 provided with a handle 97. The front end of the band 62 is fixed to a bar 111 which can be secured to the bar 63 by hooked brackets 115 fixed to the bar 111 and' provided with operating handles 118. Bolts 121, 122, Fig. 5, slidable on the bar 111 and adapted by turning a handle 131, to be projected into sockets 127 on the bar 63 are also provided to further lock the bars 63, 111 together. The ends of the plate 31 are engaged by adjustable positioning bars 166, 167, Fig. 10, clamped at their ends to resilient strips 171, Fig. 5, secured to the inner band 61. Heat is applied to the internal surface of the mould 44 by burners 45 arranged beneath a copper plate 52, and holes 265 are provided in the ends of the mould to receive pyrometer tubes. A conical spacing member 193 is arranged between the moulds 44, 19, and is preferably spaced apart from both to prevent transference of heat to the mould 191 and' is also provided with slots 251 for the escape of hot air. Cooling water from pipes 204 circulates through passages in the mould 191. In operation, the carriage 211 is moved by the rack 213, pinion 214 and hand-wheel 217 to bring the mould 44 beneath the bands 61, 62. The bar 111 is disconnected from the bar 63 and the band 62 turned up to rest against a support 268. After placing an oiled paper sheet 270 and the plate 31 upon the band 61 and adjusting the bars 166, 167 to engage the edges of the plate, the band 62 is turned down and the bars 111, 63 locked together. The shaft 79 is lowered to bring the band 61 into contact with the mould and, after the eccentrics 98 are operated to release the rear end of the band 61, the shaft is further lowered to strain the bands and plate about the mould. The eccentrics 98 are then operated to clamp the band 61 to the, bar 91, and, when the plate is sufficiently heated, the shaft 79 is raised to lift the bands sufficiently to allow the mould 191 to be brought beneath them. Upon again lowering the shaft 79, the bands are strained round the mould 191, bending the plate to the required curvature. When the plate is cold the band 62 is released and raised and the plate removed.