GB251702A - Improvements relating to mechanism for offset proofing - Google Patents

Abstract

251,702. Evans, A. B. Feb. 9, 1925. Cylinder and like offset machines ; impression surfaces.-In an offset proofing-press of the kind in which a carriage supporting the printing-block and a superposed rubber offset blanket is reciprocated beneath a scraper, the blanket is stretched tightly against the underside of a supporting-plate so as to prevent stretching and buckling of the blanket by the action of the scraper and the usual leather or zinc tympan. In one form, Fig. 2, the blanket f is clamped at one end by a bar g to the underside of a thick metal or other plate a and at the other end is clamped by a bar h to a tensioning-bar d adjustable by nuts e on screwed extensions of members b secured to the sides of the ptate a. The plate is connected by hinges j to a block n fixed to a cross-bar o on the carriage p supporting the printing-block, and the hinges are adjustable vertically by nuts r and springs s to bring the blanket f into the plane of the printing-surface. The portions l of the hinges engage the block n to prevent rearward movement of the plate a during its passage beneath the scraper. Lateral movement of the plate is prevented by a projection t on the bar d engaging in a groove in a cross-bar v. In another form. Fig. 4, a thin plate a is employed and clamped at one end to the front cross-bar w of a frame and at the other end to a bar x adjustable on the screwed extremities of the side bars b of the frame. The blanket f is secured at the front end to the underside of the plate a by a bar w<2> and at the other side is connected to the tensioning- bar d also mounted on the side bars b.