GB579686A - Improvements relating to electric discharge lamps - Google Patents

Abstract

579,686. Discharge lamps. SIEMENS ELECTRIC LAMPS & SUPPLIES, Ltd., and ALDINGTON, J. N. April 27, 1944, No. 7887. [Class 39 (i)] A high pressure mercury vapour lamp with at least one of the running electrodes heated independently of the discharge has a filling of an inert gas at a pressure not less than one hundred millimetres of mercury. In the form shown a lamp L for signalling or photography has a filling of argon, neon, helium, krypton or xenon or a mixture thereof at a pressure, preferably 500-760 mm., and if of quartz may have a coating of luminous material which may alternatively be on the inner surface of the outer jacket J containing air, nitrogen or argon. . The cathode C and, if desired, the anode A may comprise a tungsten filament enclosing barium and strontium silicates with or without thorium oxide and are connected to batteries CB, AB or auxiliary windings CS, AS on the transformer P provided for charging a condenser K which, on discharge, applies a voltage of the order of 4000 volts to the electrodes. If this is above the striking voltage the lamp will strike but the discharge will terminate as the condenser discharges and recommence on its recharge. If such repeated discharges are not required, the condenser voltage must be slightly below the striking voltage and the discharge started by bringing up a high frequency field (Tesla ,coil TC) or by auxiliary electrodes. The electrode spacing may be 40 mm. in a tube 38 mm. diameter and the seals must be suitable for heavy currents.