GB728747A - Improvements in or relating to methods of and means for anodizing metal articles - Google Patents

Abstract

728,747. Anodizing. RHONDDA PLATING WORKS, Ltd. Feb. 11, 1953 [Feb. 26, 1952], No. 4960/52. Class 41. A metal article is anodized by immersing it or a part thereof in an anodic bath, anodizing the article, scraping the oxide layer formed on the article from a portion thereof whereby to provide a sufficiently good electric conduction through such portion, and feeding an anodizing electric current through the scraped portion thereof. The invention is described as applied to anodizing electrically interconnected slide fastener elements attached to a carrier tape. As shown, slide fastener elements 3 are attached in groups to tapes 1 of considerable arbitrary length and having thickened edges 2. Each thickened edge 2 comprises a plurality of metal wires 4 by which the elements 3 are electrically interconnected. A plurality of the tapes 1 with their fastener elements interlocked are passed parallel to each other in a zig-zag path around driven guide rollers 12 and rotatable idling rollers 31, the rollers 12 are mounted in brackets of insulating material above the anodic bath 11 and are connected by slip rings 32 to the positive terminal of an electric supply, the negative terminal of which is connected to the metallic tank 10. Electric resistances 34, 35 and 36 are inserted in the leads to the first three rollers. Knurled rollers 20 rotating in the opposite direction to the guide rollers 12 and at a higher speed scrape the adjacent side of the fastener elements 3 between each successive immersion in the anodizing bath. The tapes on leaving the bath for the last time pass through a wringer 25 which removes electrolyte. According to one modification, the knurled rollers are so arranged that they scrape the periphery of the adjacent driven guide rollers and idling counter-rollers, preferably of elastic material, press the tapes against the guide rollers. According to a further modification, rotating wire brushes replace the knurled rollers to scrape the fastener elements and the respective guide rollers. If metallic knurled rollers or wire brushes are used, they may be electrically connected to the terminal to which the guide rollers are connected to provide additional points of electric contact. Alternating current may be used instead of direct current, the resistances 34-36 being replaced by impedances such as choke coils.