GB608894A - Improvements in and relating to filament joints for electric lamps or similar devices - Google Patents

Abstract

608,894. Electric welding; joints. BRITISH THOMSON-HOUSTON CO., Ltd. Feb. 25, 1946, No. 5819. Convention date, March 1, 1945. [Class 83 (iv)] [Also in Group XI] To reduce the effect of the unavoidable embrittlement produced in a filament-supporting rod when a filament is welded thereto the embrittlement is localised by providing the supporting rod 7, Fig. 1, with an intermediate portion 20 which is deformed into an angle section to form a flange 22, Fig. 4, in a plane of transverse stress and a flange 21 extending cross-wise of the flange 22, the filament being welded to the side of the cross-wise flange which is remote from the flange 22. As shown, the supporting-rod 7 is of circular cross-section with an intermediate portion 20 of its length deformed into a T-shaped cross-section. across which the coiled end of a filament 18 is welded. The end of the filament is reinforced by a short metal rod or spud 19 which is gripped tightly by the convolutions of the coil. Welding is effected by a pair of electrodes 23, 24 of which the lower electrode 23 is slotted to receive the T-shaped portion of the filament supporting wire and provide a clearance around the flange 22 so that the heat is localised substantially across the top flanges 21 in contact with the filament 18. The upper electrode 24 has a transverse semi-circular depression to receive and engage the adjacent end coil of the filament. Each electrode is preferably of the material which is in contact with it during welding, e.g. molybdenum for the electrode 23 engaging the filament supporting rod 7 and tungsten for the filament-engaging electrode 24. During welding, the end portion of the filament is welded to the support 19 at a point remote from where they separate, thereby ensuring that the part of-the filament adjacent the latter point is free from embrittlement.