GB630547A - Improvements in and relating to electric discharge lamps - Google Patents

Abstract

630,547. Discharge lamps. GENERAL ELECTRIC CO., Ltd., NELSON, E. H., and POWER, E. B. March 5, 1945, No. 5452. [Class 39 (i)] An electric dicharge lamp, preferably of the high pressure mercury vapour type, comprises a quartz tube 14, Fig. 1, sealed to the quartz envelope 10, and a metal plate 18, preferably of brass, is secured to the open end of the tube 14 by means of a threaded bolt 19 and nut 20 passing through an asbestos sleeve 17 and serving when tightened up to expand the asbestos outwards against the quartz tube 14 ; the metal plate 18 serves as the cap of the device or as part of the capping structure. In Fig. 1, one or more molybdenium strips serving as a lead or leads to electrode 11, are embedded in the quartz tube 14 and their outer ends are soldered to metal plate 18. Alternatively, the external contact may be insulated from plate 18. A brass tube 21 may protect the seal and a metal cap may be placed over the head of bolt 19. The nut 20 is of conical shape as shown, to assist in forcing the asbestos outwards against the quartz tube 14. A similar capping arrangement is provided at the other end of the lamp. In a modification, Figs. 2, 3, the leads to two electrodes are brought out at the same end of the device. In this case the metal plate 18 is elongated as shown and the molybdenum strip leads 15 to the electrodes pass on either side of it. The strips 15 may be soldered to two external contacts on brass cap 22 insulated from one another and from the cap; alternatively, the cap may constitute one contact. In all forms, either the nut or head of the bolt, whichever is inside the quartz tube, may be conical, the asbestos tube may be painted or soaked in concentrated silicate solution to improve its adhesion to the quartz, and rotation of the asbestos tube may be prevented by making the quartz tube of other than circular cross - section, or by providing it with a deformation.