GB379475A - An improved method of and means for applying water or other ink-rejecting agent to planographic printing plates - Google Patents

Abstract

379,475. Lithographic printing. TRIST, A. R., 56, Victoria Street, London. July 23, 1931, No. 21098. Convention date, July 25, 1930. [Class 100 (ii).] In a lithographic printing-machine, an inkrejecting agent is applied to the printing plate by a rotary brush in light contact with the plate and moving at a higher surface speed than that of the plate. The Figure shows a brush for applying a mixture of mercury and water vapour to a plate having non-printing areas of mercury amalgam. The brush comprises a perforated tube 5 covered with a napped fabric 9 and provided with two concentric tubes 16, 17 of fine wire gauze between which is packed a mixture of chalk and finely divided mercury. Centrally of the brush is arranged a fixed tube 11 connected to a supply nozzle 13 for water under pressure and provided with a straight row of perforations 12. Surrounding the tube 11 is a tube 14 provided with a helical row of perforations and rotatable by a handle 16 to bring any one of its perforations into register with one of the perforations 12. The brush is mounted in bearings 7 and rotated at high speed by a pulley S, the nap of the fabric contacting with the printing surface so lightly as not to injure the inked image. The water passing through the tubes 16, 17 carries sufficient mercury with it to maintain the printing plate in proper condition. The brush also acts to prevent tarnishing of the amalgamated surface of the plate. For applying water only for ordinary lithography, the tubes 16, 17 are omitted, and the tubes 11, 14 may also be omitted, the water being applied to the brush in any suitable manner.