GB751253A - Improvements in or relating to the preparation of printing plates - Google Patents

Abstract

751,253. Printing surfaces. BECH, J. March 18, 1954, No. 7905/54. Class 100 (2). [Also in Group XXIII] A method of preparing stereotype or other printing plates by placing the printing plate with its printing face on a porous underlayer arranged over grooves in a table connected to a vacuum generator and working the rear side of the printing plate with a milling or grinding tool, is characterized by masking-off portions of the grooves outside the printing plate. The table 1 has a suction pipe 2 communicating with a number of grooves 3 intersecting each other throughout the entire table top and all ending a short distance within the edges of the table. The underlayer 4 consists of porous material, e.g. paper. The area of the underlayer and of the portions of the grooves 3 lying outside the printing plate 5 is covered by a mask 7 made of a relatively dense material having such strength that it can resist the vacuum effect, e.g. the mask may be of strong stout paper, rubber or the like. It is provided with an aperture slightly smaller in area than the printing plate so that the edges 8 of the aperture will be bent upwardly along the edges of the printing plate. A device may be provided for shutting-off portions of the table top grooves from the remainder thereof, comprising a rectangular frame having such a wall thickness and wall height that it can be inserted within a predetermined number of grooves 3 with its upper edge level with the table top, thus isolating an area such as 10. The areas may be connected to the vacuum generator by separate pipe connections. The table top may be curved or plane. The underlayer may have a porous portion corresponding in size exactly to the area of the printing plate, the remainder of the underlayer being made of dense material and serving as a mask, the separate mask being dispensed with.