GB737440A - Method of making embossing rolls and embossing rolls made by such method - Google Patents

Abstract

737,440. Making embossing rollers. SUNDERHAUF, F. A., and O'HEAR, J. C. Dec. 3, 1953, No. 33653/53. Class 83 (2). [Also in Group XVI] A pair of mated engraved steel rollers for embossing sheet material are made by engraving an upper relatively soft roller 1, e.g. by forcing a hardened master roll against it, so as to produce projections thereon, hardening this roller, fixing a gear-wheel 3 on the shaft 2 thereof, coating a lower roller 5 having a similar gear 7 with an acid-resisting wax 11, Fig. 9, pressing the upper roller against the lower roller to produce waxed and unwaxed areas on the lower roller as shown in Fig. 9, lowering the lower roller into an acid bath 12, Fig. 10, to eat away metal from the exposed areas, and washing off excess acid. The process of coating the lower roller with wax, pressing the upper roller against it to impress its pattern on the wax and treating in the acid bath 12, is repeated several times using successively greater pressures until the lower roller is mated with the upper. The lower roller is then given a further acid treatment to produce a predetermined clearance between the projections of the upper roller and their mated recesses on the lower roller, as shown in Fig. 11, to avoid cutting or damaging material 14 being embossed. The acid may be nitric or acetic acid. Each successive rolling operation to impress the pattern of the upper roller upon the wax coating of the lower roller is carried out with increasing pressure so that the rollers bend slightly and cause the markings in the wax coating to be deeper at the ends of the rollers. By this means a slight bulging of the lower roller is obtained, the diameter of the central portion being a little greater than that at the ends. This compensates for bending of the rollers during use and equalizes the embossing pressure along the length of the rollers.