GB715030A - Improvements in making ready cylindrical printing plates - Google Patents

Abstract

715,030. Printing-surfaces; printing processes. ELECTROGRAPHIC CORPORATION. April 14, 1951, No. 8346/51. Class 100 (2) Mechanical treatment of plates; make-ready arrangements. - An underlay for making ready a cylindrically curved relief printing plate is prepared by forming a stereotype mat from a printing plate or forme and a flong which shrinks on drying in a direction circumferentially of the cylindrical plate to be underlaid, drying the mat and forming from the mat itself or by means of the mat an underlay having thicker portions corresponding to the solid printing areas of the plate. The mat used in preparing the underlay, Fig. 2, has on its back raised portions 22, 24, corresponding to the full tones and half tones of the printing plate or forme. The required underlay is formed therefrom either (i) by shaving away the front of the mat after shrinking and using the shaved mat itself as an underlay or (ii) by casting from the shrunk mat a stereotype plate, printing with the latter on a sheet of underlay stock and cutting the printed sheet of underlay stock to form an underlay in accordance with the printed impression thereon. The underlays so formed may be used directly as a press underlay or may be used in the bumping of the cylindrically curved press plate which is subsequently used without the underlay. As shown in Fig. 6 a plate 60 is passed, together with the underlay 36 and a reverse overlay 50, between pressure rollers 62, the printing surfaces of the plate being forced to the required height. The underlay 36 may have been made either as in (i) or (ii) above. Specification 701,752 is referred to.