GB432607A - Improvements in or relating to incandescent electric lamps - Google Patents

Abstract

432,607. Making multiple filament electric lamps. ISMAY & SONS, Ltd., J., Roden Street Works, and ISMAY, J., 10, Warwick Gardens, both in Ilford, Essex. May 31, 1934, No. 16298. [Class 39 (ii)] In an electric incandescent lamp of the double filament type having one leading-in wire 7, Fig. 1, connected in common to each of the two filaments 11, 12, a pinch formed at the end of a foot 2 is provided with three lateral protuberances, each of which encloses one of the leading-in wires 7-9, Fig. 4, two of the protuberances extending in directions approximately diametrically opposite to one another and the third in a direction substantially perpendicular to them, an exhausting-tube 5 being attached to a substantially flat side of the pinch opposite to the third protuberance. A central glass stem comprising a rod 3 originally separate from the lamp foot is welded within the end of the stem. In making the stem the three leading-in wires 7-9 and the stem 3 are located in holes in a jig and inserted within an open-ended glass foot 2 in the requisite position relatively to the exhausting tube 5, also mounted within the foot. The operation is performed in a capstan machine, wherein the parts are heated progressively to soften them before the pinch is formed by jaws of corresponding form. A jet of flame is subsequently directed on the foot opposite to the end of the exhausting tube 5, and air is blown through the latter to form an aperture 6 through the pinch. One leading-in wire 8 may be enclosed within a glass tube 14, as described in Specification 432,354, to prevent ionization between the leading-in wires, and the bulb may be provided with a cap 4 of the form described in Specification 431,894. Specifications 222,964 and 317,833, [both in Class 39 (ii)], also are referred to.