| 摘要 |
1,198,541. Etching. VACCO INDUSTRIES. 11 Jan., 1968, No. 1611/68. Heading B6J. [Also in Divisions B1-B2 and B3] Annular metal discs, intended to form elements of an edge filter, having raised projections 169 on one side only, are formed by etching, which simultaneously removes metal from one side to leave the projections and from both sides to sever the discs from a metal sheet. Figs. 15, 16 show how the two sides of the sheet are covered, by silk screen printing or photographic methods, with etch-resisting material where shaded. The sheet may be stainless steel 0.002 inch thick, and the projections rise 0.001 inch from the etched surface of the finished disc. The etched surface is rough to assist filtration.
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