Improvements in or relating to a method of retaining part of the core-wire material within a filament helix wound around the core

摘要

823,695. Making electric lamp filaments. PHILIPS ELECTRICAL INDUSTRIES Ltd. Nov. 10, 1955 [Nov. 13, 1954], No. 32195/55. Class 39(2) [Also in Group XVI] In order that the process of removing by etching the unwanted parts of a core upon which a wire filament is helically wound shall result in substantially flat end surfaces 8, 9 upon a retained core piece 7 of the required overall length, at least the parts E-C and D-F of the filament and core immediately adjacent to the core piece 7 are, before the application of a wax layer upon the part 7 and the portion of the filament wound upon it, treated with a substance capable of increasing the surface tension of the wax. The parts E-C and D-F may be painted with a brush moistened by partly hydrolised ethyl silicate, or the complete filament with the core may be immersed in a bath of that substance, after which a wax layer is applied to the part C-D and the unwanted core material etched away and the wax layer subsequently removed.