A MULTI-METALLIC FOIL TECHNOLOGY FOR MINTING MEDALS AND COINS WITH TWO OR THREE COLORS

摘要

The invention deals with a technology for minting coins and medals. The technology is based on the utilization of metal blanks with similar diameters, one being very thin (hereafter named as the foil), joined together by mechanical means during the impartion of the surface details by the minting dies. The technology requires the design and manufacture of a special geometry in the edge of the thicker disk in order to make possible assembly of the metal blanks. The proposed technology is based on a multi-stage manufacturing process consisting of three cold metal forming operations (preforming, rimming and coining) and one intermediate annealing treatment. The first metal forming operation ensures the preforming of the thicker disk blank, hereafter named as the disk. The second metal forming stage is the rimming operation in which the preformed disk is bent along its diameter in order to generate a suitable profile for subsequent assembly with the foil. The third metal forming stage is a coining operation in which the metal blanks (disk and foil) are assembled together, by locking the foil into the rimmed edge of the disk, during the imprint of the surface details. The annealing treatment is to be performed before the coining operation. The goal is to restore the initial ductility of the disk prior to the final coining stage.