| 摘要 |
465,119. Coiling helices. HYGRADE SYLVANIA CORPORATION. Oct. 30, 1935, No. 29984. Convention date, Nov. 8, 1934. [Class 83 (iv)] [Also in Group XI] Cores.-In the manufacture of coiled coil tungsten filaments of lamps, discharge tubes, &c., the filament wire 1 is helically wound on a mandrel 2 of refractory metal such as molybdenum having a lower setting temperature than. the filament and the mandrel 2 is then wound on a second mandrel 3 of non-refractory material such as steel as shown in the Figure. The assembly is then heated to a temperature, e.g. 1100‹ C. at which the mandrel 2 is set without setting the tungsten filament. The mandrel 3 is then removed and the coiled mandrel 2 and filament heated to a temperature, e.g. 1650‹ C. at which the filament is set. The mandrel 2 is removed by dissolving with a mixture of nitric and sulphuric acid. |
