GB1372935A - High intensity vapour arc lamp - Google Patents

Abstract

1372935 Metal-vapour lamps GENERAL ELECTRIC CO 23 Feb 1973 [1 March 1972 13 March 1972] 8948/73 Heading H1D A vacuum-jacketed, high-intensity, vapourarc lamp is provided with current leads which, within the vacuum space, are modified to provide an arc gap and, upon occurrence of an arc, to deform and close the gap under the heat of the arc. Arcing may occur upon application of high starting voltages if the vacuum is lost, and the effect of the short-circuit is to prevent damage to fittings, etc. which would occur should the arc not be extinguished. As shown in Fig. 2, leads 6, 7 enter vacuum envelope 2 through press 5 and are attached inside the envelope to conductive supporting members (not shown) extending to either extremity of the discharge tube. Immediately below the press an iron or nickel wire 41 is attached to the lead 7 and extends in a loop 42 around the lead 6 thus defining a point of minimum separation between the leads where arcing is initiated. The loop is spaced from the lead by a sleeve 44 of lead glass. When the arcing occurs, both the loop and the sleeve melt, the loop is fused to the lead 6 and the supply short-circuited before the arc becomes destructive. A further sleeve 45 of glass prevents arcing between the lead 6 and the stem of the loop. In the modification shown in Fig. 4, the same effect is secured with a double loop 47, 48 of nickel or iron wire. A second arcing fuse, provided in the base of the lamp to prevent destructive arcing in this region, is made by looping external lead 6a around external lead 7a and exhaust tube 38. A sleeve 46 of lead glass prevents contact between the conductors and melts upon being touched by the arc. The conductors are made of nickel-plated copper wires stranded about a solid nickel core. A further modification is described (Figs. 5-7, not shown) in which one of the internal leads carries a bimetallic strip whose extremity forms an arc gap with the other lead and carries a small lead of brazing metal. When the strip is heated by an arc, the gap closes and the brazing metal is fused to the adjacent lead.