GB747679A - Improvements in electric lamps - Google Patents

Abstract

747,679. Electric incandescent lamps with cut-outs. METROPOLITAN-VICKERS ELECTRICAL CO., Ltd. June 14, 1954 [July 3, 1953] No. 18550/53. Class 39(2).. In an electric incandescent lamp of the kind intended for series connection, e.g. for decorative purposes, and having a semi-conducting member or cutout carried between the filament supporting wires, the semiconducting member comprises a mixture of powdered cuprous oxide and powdered glass fused into a bead-like body 5 which serves to locate the supporting wires 2 with respect to one another. Alternatively the body 5 may be additional to the glass bead which normally locates the filament supporting wires, in which case the latter bead is the nearer to the filament. The mixture of powdered cuprous oxide and powdered glass may be formed as a small collar which is slipped over the supporting wires and heated and fused around them, or a mixture of the powders or a pellet of the same materials may be packed into a glass collar previously positioned over the supporting wires and heated to fuse the glass collar and powdered mass. In the latter instance the fusion of the powdered mixture is preferably effected, or assisted, by the passage of an electric current therethrough while the glass is hot. After the bead has been formed, a small amount of carbon powder is preferably applied to its lower surface, either by spraying a film of carbon in a cooling jet of nitrogen, or applying a very weak suspension of colloidal graphite, the object being to facilitate the breakdown of the semiconducting head when the filament fails.