GB262529A - Improvements in and relating to the manufacture of printing plates - Google Patents

Abstract

262,529. Marks, E. C. R., [Wood Newspaper Machinery Corporation). Sept. 14, 1925. Stereotype, casting. Stereotype printing- plates are separated from the riser or a supply of metal while the metal is in a liquid or plastic state by gradually displacing the metal above the mould cavity in such a way that some of the displaced metal flows towards the mould cavity to compensate for r shrinkage in the plate during cooling. This is effected by introducing an object into the mould cavity, so as to restrict gradually the mould entrance and to displace the metal lying between the source of supply and the edge of the matrix. The mould consists of a back 22 against which the matrix M is clamped by bars 23 and clips 24, and a rotatably-mounted core 25 provided with two opposite casting-surfaces. Metal enters the mould by gravity at a point adjacent to one of the clamping-devices through a spout 19 from a hopper 6 mounted above the mould. The hopper is fed with metal from a melting-pot 1 by a pump 7, and the hopper and spout are provided with means for keeping the metal in a molten condition. When the cast plate has begun to solidify, a shutter 29 adapted to slide circumferentially on the core 25 and operated from a cam 33 on the driving-shaft 34 commences to move gradually into the mould aperture. The part of the shutter 29 which enters the mould is of wedge shape and its operative face 45 is arranged to move transversely relatively to the mould entrance. The core is provided with means, such as a hole 36 in the wall, or a thickened wall, near to the spout 19 in order to insulate this part from the effects of the cooling- water in the core. As the shutter 29 moves it pushes metal before it into the mould to compensate for shrinkage due to cooling, and forces any excess metal back into the hopper 6 through the space between itself and the matrix-clip 24. The faces of the clip 24 and shutter 29 are substantially vertical and are shaped to cut off the supply of metal entirely, and the edges are formed so that the shape of the edge of the cast plate is of the correct shape to enable it to be clamped on the cylinder of the press. Grooves 39 are formed on the core for the purpose of forming ridges on the plate, and, in order to pre. vent the molten metal from running upwards into the grooves on the other part of the core, a lip 40 is formed on the lower end of the shutter. When the plate has solidified, the back 22 of the mould is lowered to strip the matrix from the plate, and the core is rotated, the cast plate P being carried round by reason of a projection thereon cast in a recess in the core. The free end of the plate is lifted by a part 42 of the shutfer 29 to facilitate removal.