GB718069A - Improvements in or relating to microscopic printing - Google Patents

Abstract

718,069. Printing. READEX MICROPRINT CORPORATION. May 13, 1952 [May 15, 1951], No. 12149/52. Class 100 (2). High fidelity planographic printing of a fine image (e.g. a microscopic reproduction of type matter) is carried out by repeated inking (e.g. 3-5 times) of the printing plate with thin layers of ink before each impression, the impression then being made against a thin resilient blanket member (of the order of 0.078 in. thick) under a heavy pressure equal to that required to compress the blanket member by at least 0.018 in., and preferably 0.025- 0.036 in. The total thickness of ink possible without smudging or spreading may be divided equally between the repeated inkings; the paper stock is preferably of the coated kind, and the printing plate of a very fine grain. It is stated that an image 5 Î 7# in., representing 25 pages of a newspaper in 6-point type, printed in this way can be read easily with a X 17¢ diam. magnifier. The method may be practised on a duplicating machine as described in Specification 550,523, set for direct printing, the cams for releasing the gripper at the feeding station being made movable for projection into operative position only for printing. Alternatively, the apparatus shown may be used, wherein the printing plate 3 on the fixed-bearing cylinder 1 is damped from a liquid reservoir 15 and inked from an ink fountain 14 having an adjustable doctor blade 17; during the repeated revolutions of the cylinder 1 for inking, the impression cylinder 4 is spaced therefrom; for printing, the impression cylinder bearings 5 are moved by levers such as 8 to give the required pressure, and are then locked by nuts 10, 10a; the cylinder 4 carries a resilient blanket of the standard " hard " kind, and has a paper gripper 11 liftable about its hinged leading edge 11a against a spring 12.