GB513175A - Improvements in and relating to the photomechanical engraving of printing surfaces - Google Patents

Abstract

513,175. Photomechanical printing cylinders. PHOTO-CYLINDER CORPORATION. April 2, 1938, No. 10135. Convention date, April 3, 1937. [Class 98 (ii)] In a method of engraving a printing cylinder with a design having' irregular borders, a flexible film carries an image of the design which has at each part of its width a length equal to half the circumference of the cylinder, and is brought successively into contact with adjacent areas of the photo-sensitized cylinder and the cylinder exposed, developed and etched, so that the irregular borders of the design are interfitted at adjacent circumferential reproductions to form a continuous design around the cylinder. As shown, the cylinder 20 is carried on a mandrel 23 rotatable in vertically adjustable bearings 25, 26, the bearing 26 being movable along the frame 29 to accommodate cylinders of different lengths. The film 22 is passed over the cylinder, and its ends are clamped between a bar 36 and a plate 37, Fig. 5, vertically slidable in a carriage 47 movable on rails 53, 54 on the frames 29, 30 beneath the cylinder, the plate 37 being urged upwards by springs 55. To hold the film against the cylinder, a resilient strap 57 is connected to the plate 37 and to a bar 61 rotatable by a ratchet to draw the plate 37 downwards. The illumination is supplied by two arc lamp assemblies 108 on a carriage 92 slidable on rails 93, each assembly including a reflector 119 and a light tunnel 120. A hood 123 is vertically movable on rails, and when in position is contiguous with the tunnels 120, Fig. 5. A frame 89, Fig. 8, carries dark sleeves 87, 88 enclosing the cylinder except at the position of the film. After an exposure, the film is disengaged from the cylinder and the carriage 47 moved laterally until the right hand end of the film registers with the position previously occupied by its left hand end, and the exposure repeated, an adjustable stop 136 ensuring correct registration.' When a length of the cylinder has been exposed, it is rotated to expose the other side, the mandrel 23 carrying a disc bearing held to permit accurate location of the cylinder.