GB587611A - Improvements in or relating to the sealing of an electrode system into the hard glass bulb of a mercury vapour or other vapour discharge lamp - Google Patents

Abstract

587,611. Discharge lamps. DANIELS, G., and CROMPTON PARKINSON, Ltd. Dec. 1, 1944, No. 24052. [Class 39 (i)] In a mercury or other vapour discharge lamp, the electrode leads 6, 7, 9, 10, Fig. 2, sheathed with glass in the appropriate region, are sealed into tubular end portions of the hard glass bulb 1 by the application of heat, with or without pinching of the tubes, while an inert or weakly reducing gas flows through the bulb, to avoid oxidation of the cathode material. The gas is preferably nitrogen-or nitrogen with an addition of hydrogen. The lengths of the tubular end portions preferably do not exceed or greatly exceed their internal diameters ; e.g. the diameter may be from 0.7 to 1.5 times the length, the optimum relation being 1:1. The electrode system may include a starting electrode, a dummy electrode or both. Fig. 2 shows two working electrodes 4, 5, a starting electrode 8 and, for purposes of symmetry and facilitating the making of the seal, a dummy electrode 10. After the sealing operation, the bulb is preferably annealed at a high temperature in the presence of an inert or weakly reducing gas. A number of bulbs may be sealed with the aid of a multi-head machine.