GB339803A - Improvements relating to the manufacture of filaments for electric lamps - Google Patents

Abstract

339,803. Westinghouse Lamp Co., (Assignees of Wadsten, S., and Hunt, C. W.). Dec. 29, 1928, [Convention date]. Filaments.-A coiled filament for an incandescent lamp is made by coiling a wire in a machine such as is described in Specification 292,743, [Class 83 (iv), Metals, Working], or otherwise to a closer pitch than that finally required, cutting off a portion containing the required amount of wire, stretching it to the required overall length, and finally cleaning it. For this purpose the wire is fed by rolls 12, 13 to a die shaped so as to coil the wire to the desired pitch. The die 10 may be formed with a lip to space the coils, or when a very tight-wound coil is to be formed the lip may be dispensed with. When a predetermined length of wire has passed through the machine the wire is cut and the cut-off portion gripped between jaws 22, 23, Fig. 3. These jaws are then moved apart so as to space the coils to the desired extent, e.g. a coil with 390 turns per inch may be stretched so as to have 370 per inch. The jaws with the coil are then moved into a chamber containing neutral or reducing gas, where the coil is heated by a current passed through it by means of the jaws to destroy grease &c. on it and to give it a permanent set.. The coil may be heated in air before passing to the chamber containing the gas. It is stated that the end portions held by the jaws 22, 23 are heated less strongly than the remainder, and are therefore more pliable, which is of advantage in fixing the coil in the lamp.