GB491073A - Improvements in electric incandescent lamps - Google Patents

Abstract

491,073. Electric incandescent lamps. GENERAL ELECTRIC CO., Ltd. (Patent- Treuhand-Ges. f³r Elektrische Gl³hlampen) Feb. 22, 1937, No. 5226. [Class 39 (ii)] In an electric incandescent lamp of the type wherein a substantial part of the filling consists of krypton or xenon or a mixture thereof, and the part of the bulb surrounding the filament is sc shaped that its volume is as small as possible for a normal commercial life, the bulb has no foot-tube but is closed by a ceramic mem. ber through which pass the leading-in wires. The Figure shows a bulb 1 closed by a ceramic plate 3 provided with a central aperture through which pass a pumping tube 4 and leading-in wires 5, 6, the junction between these members being sealed with enamel 18. Enamel may also be used to seal the ceramic plate 3 to the neck 2 of the bulb. A metal reflecting plate may be supported above the plate 3 by wires fixed in the enamel 18 which seals the central hole. Alternatively the inner surface of the plate may be coated in known manner with an enamel reflecting-surface which may also serve to seal the members together. A metal cap 11 may be sealed to the bulb neck 2 and may enclose a fuse wire 15 in each leading-in wire, surrounded by a glass tube 16. The ceramic plate 3 may be a white non-porous plate made by sintering together a mixture of 50 per cent magnesium oxide and 50 per cent titanium oxide, or of 70 per cent magnesium oxide, 29 per cent beryllium oxide, and 1 per cent titanium oxide. In a modification the ceramic plate comprises the flat bottom of a cylindrical ceramic member to the open outer end of which a metal cap is cemented. Alternatively the cap itself may be of a ceramic material of a composition different from that of the cylindrical member, the end of the cap being formed with screw threads provided with a metal coating to which one leading-in wire is connected, the other leading-in wire being connected to a sprayed-on bottom contact. Two or more filaments may be included in the same lamp, with arrangements of known kind for bringing one into operation when another fails. Specifications 418,867 and 471,268 are referred to.