GB310895A - Improvements in and relating to electric discharge devices - Google Patents

Abstract

310,895. Spanner, H. J., and D÷ring, U. May 2, 1928, [Convention date]. Vacuum tubes; low-pressure metallic-vapour apparatus.-A gas discharge lamp for producing visible or ultra-violet radiation has a central hot cathode surrounded by a large anode which intercepts only a small proportion of the radiation, the lamp radiating in the radial and longitudinal directions. The anode may comprise a net 15b, Fig. 3, of wide mesh or a perforated disc 15, Fig. 1, or a short cylinder which may be connected to a metal ring near and around the cathode. The cathode 12 may be heated directly by current from a transformer as in Fig. 1 or indirectly by a heater arranged near it as in Fig. 3, the heating circuit being in series or parallel with the discharge circuit. When the heater and resistance are connected in parallel to the discharge circuit, an electromagnet in the latter circuit breaks the heater circuit when the discharge starts, the discharge keeping the cathode hot. When the heater is in series with the discharge circuit, the distance between the cathode and anode may be small at one or more points so that the discharge starts with a cold cathode, or the discharge is initially shunted by a resistance 65, Fig. 3, and this shunt is broken by an electromagnetic switch 69 when the discharge starts, the heater acting as ballast resistance to the discharge. The electromagnetic switch and resistance, also a series inductance 67, may be combined with the lamp in a screwcap 63 so that the device can be used in ordinary lamp sockets. The bulb 11 may be of coloured or fluorescent glass or any material transmitting ultra-violet rays and not transmitting visible rays and may be coated with fluorescent material or covered with a legend. The filling may be gas or vapour, for example a mixture of argon and mercury vapour in a lamp for sterilizing and ozonizing. The cathode may. be of the kind described in Specification 310,810. The Specification as open to inspection under Sect. 91 (3) (a) comprises also lamps with fillings of argon or mercury vapour, with a disc anode in front of the cathode, and with a tubular envelope bent into a ring with its ends in a contact plug. This subject-matter does not appear in the Specification as accepted.