GB649060A - Printing apparatus and process - Google Patents

Abstract

<PICT:0649060/III/1> <PICT:0649060/III/2> <PICT:0649060/III/3> <PICT:0649060/III/4> <PICT:0649060/III/5> For printing by the method in which ink passes to the web under the action of electric lines of force a printing-cylinder is employed in which ink is fed to the space 23 between a metal cylinder 24 and a concentric cylinder 21 which is formed with perforations 22 through which ink can pass to a porous outer covering formed of laminated layers of materials which are spirally wound around the cylinder 21 and are non-frangible. The first layer consists of a coiled spring 32, Fig. 6, of rectangular cross-section and formed with a serrated upper surface, and wound under tension with the coils spaced apart a slight distance. Over the spring 32 is wound with opposite thread a strip 34 of fine mesh perforate material such as bronze screen or fibre glass, and a further similar layer 35 which is wound in opposite direction to the strip 34. The surface of the cylinder 21 is also serrated at 21a. An impermeable layer 36 to form a design is applied to the outer surface 35 by known means, and an ink supply is connected to the space 23 from a pipe 26 and conduits which pass through a disc 20 in which the cylinders 21, 24 are mounted. The ink is retained in the outer layers 34, 35 by capillary action but is expelled when a source of potential is connected from conduits 51, 45 to plates 41, 48 fitted with repulsion and attraction blades 42, 49 which are arranged radially of the cylinder 24, and extend substantially half-way round the cylinder. The web 52 extends around half of the cylinder and is subjected to electric action over a large area for a comparatively long period so that low voltages can be used. In a modification the feed of the web is assisted by means of a pair of rollers acting at each edge of the cylinder on a narrow width of web, the rollers being provided with helical feed surfaces which maintain the web taut laterally. In a further modification, Fig. 10, a pair of plain feed rollers 60 are used extending across the cylinder, and gaps are provided in the electrical attraction and repulsion elements, which are fitted with pins 56, 58 staggered in a direction axially of the cylinder, so that a substantially continuous electric field is formed over a wide area and extending the complete width of the web. The apparatus may be used to apply a continuous coating instead of a design. Specification 636,907, [Group XVI], is referred to.