Patent GB-759472-A (GB)
Title: Methods of and apparatus for embossing pliable materials under pressure
IPC: D21H27/32
Filed: 1950-08-25
Abstract: 759,472. Embossing. MACCLURE, V. Nov. 23, 1951 [Aug. 25, 1950], No. 21128/50. Class 100 (2). [Also in Group VIII] Embossed articles are made from laminated mouldable material consisting of layers of paper, with or without layers of pulp board, and with an internal reinforcement, by making the material somewhat pliable by damping and then submitting it to pressure and heat between dies or moulds made from metal of low melting point, e.g. type metal. A female cast is made and secured in a rim A, and a male mould formed by trowelling or pouring heat-resistant material thereover, the rim A being then secured between the trays 4, 4a of a mould trolley by bolts 8 which secure the cast in the rim and are passed through L-slots 7 in the trays. The trays are hinged together at 3 and locked together by latches L. The sides of the trolley may be heated by electric elements. The male cast is arranged in the trolley and heated to remove moisture, and the remaining space filled with molten metal to form a metal female die, sheet steel to enclose the metal being attached to the rim A or to the mould. The male cast is then removed, the female die coated, e.g. with whitewash, to a thickness less than that of the material to be embossed, the mould closed, moisture removed by heating, and the remaining space filled with molten metal to form the male die. These dies may be used in a flat press comprising two pivoted trays which may be closed together with the aid of a sliding counterweight and extra pressure applied by means of a hand lever or locking screws. The material used may consist of layers of moistened paper and pulp board reinforced by and pasted to an internal layer of fabric. A fine finish may be obtained by pasting an additional layer of tissue paper and adding china clay to the moistening fluid, and fireproofing by adding to the moistening fluid a mixture of alum in ammonia or of borax in boric acid with casein used as stiffening agent. Material for use with deep or intricate dies is formed by pouring a mixture of pulp with china clay and water, casein alum ammonia, or casein borax boric acid on to a fabric stretched on wire gauze, and allowing to drain, thin paper soaked in the moistening solution being then applied to both sides, and excess moisture removed by rollers. Dies for a rotary press may be formed by making two impressions on damp paper laminations pasted together and fortified with china clay from the lower die in a heated hand press, fitting the first impression, with backing if necessary, in the interior of a two-part cylinder 25, 26, which may be heated and surrounds a heated roller 27, and pouring metal between the impression and the roller to form a cylindrical female die. A male die is similarly made by using the reverse face of the second impression. The finished rollers 27 are incorporated in the apparatus shown in Fig. 13 wherein the material to be embossed comprises outer layers run off from tanks 32, 32b containing wetting and fireproofing liquid, and a centre layer from tank 32a containing adhesive. The layers are passed through rollers 32c to remove liquid, rollers 33 to unite the layers, and embossing rollers 27, and may be additionally heated in chamber 34. The layers may comprise a backing of thin paper layers, a fabric centre, and a relatively thick pulp board top layer. A further material comprises outer layers of Kraft paper, and centre layer of fabric loaded with an adhesive emulsion of plastic material. If desired the embossed material may be filled in at the back with pastes. Small quantities of material without great embossing accuracy can be obtained by coating the male roller with a quick-setting metal moulding material and then rolling this under the female die to obtain the male impression.