GB580276A - Improvements in and relating to electric discharge devices - Google Patents

Abstract

580,276. Electric discharge devices. BRITISH THOMSON-HOUSTON CO., Ltd. June 8, 1944, No. 11004. Convention date, June 8, 1943. [Class 39 (ii)] [Also in Groups XXXVI and XL] In electric discharge devices or lamps, lead-in conductors 19 of tungsten or molybdenum are connected to tungsten electrodes 12 by molybdenum ribbons 18 sealed by collapsing the portions 14 of the tubular vitreous casing. To prevent oxidation during fabrication of the device, the leads 19 are enclosed in hermetically sealed chambers 23 the ends of which are finally severed. Fig, 3 shows means for exhausting, degassing, and charging a series of lamps L comprising a suction device S for connexion to the exhaust tubes t of the lamps and an electrically-heated oven 30 adapted to be raised and lowered over the lamps. After baking in the oven, the electrodes 12 may be degassed by the use of capacitative couplings 41 slipped over the tube ends. Starting-gas such as argon is then admitted, the suction pipes t are tipped off, as at 22, and blobs 24 of mercury transferred from bends in the pipes into the discharge chambers 10 of the lamps. Fig. 1 shows a starting and operating circuit for the lamp comprising a step-up transformer A whose secondary is connected across the leads 19 and its primary across a supply-line 50 fitted with a control-switch 56. A choke coil 51 is fitted in one of the leads 19, the other lead including the switch-opening solenoid 53 of a self-closing relay vacuum switch 54 in a shunt circuit 55 connected across the leads 19. On closure of the switch 56, the sudden opening of the relay-switch 54 produces a highvoltage surge to initiate the discharge between the electrodes 12.