GB1340551A - High pressure sodium vapour discharge lamp - Google Patents

Abstract

1340551 Metal vapour lamps PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd 19 April 1971 [17 March 1970] 23911/71 Heading H1D A high pressure Na vapour discharge lamp with an elongated envelope has two main electrodes 16, 17, an auxiliary electrode 15 (e.g. 0À24 mm. W wire) external to and spaced from the tube (e.g. by 0À25 mm.) which electrode includes a part embracing at least one quarter of the circumference of a cross-section of the tube and is connected to one of the main electrodes through a non-resistive connection wherein the entire auxiliary electrode comprising ring 15 and link 18 lies within a region between 1 and 3 cms. from the nearest point of the other main electrode and wherein the auxiliary electrode is permanently connected by a non-resistive connection to a lead-in conductor. The electrode may be a stub of 1 to 1¢ cms. parallel to the tube axis and the dimension in a direction parallel to the longitudinal axis direction may be <1 cm. and less than 0À05 times the distance between the main electrodes. The area of the radial projection of the auxiliary electrode on to the outer wall of the tube may be <0À05 times the surface area of that portion of the outer wall of the tube between the main electrodes and may comprise a few turns around the tube. Ignition gas may comprise Xe or Ne and Ar, Na with Hg and Ne plus 0À3% Ar also being disclosed. The spacing of the auxiliary electrode from the tube inhibits quick evaporation and high temperature attack. Starting voltages are instanced with a 0À12 Henry inductance lamp length may be 27¢ cms. and the lamp also includes stranded wire connector 9, non-resistive wire parts 10, 11 with convolution 12 about a tube indent, outer envelope 1 of 4À6 cms. diameter, inner tube 3 of 0À95 cm. diameter and length 11À5 cms., electrodes 16, 17 being 5, 8, or 13À5 cms. apart, shortest distance between electrodes 15, 16 being 23 mms. for example.