Patent GB-421705-A (GB)
Title: Improvements in or relating to luminous electric discharge tubes
IPC: B42F13/28
Filed: 1934-03-26
Abstract: 421,705. Discharge lamps. WESTING- HOUSE LAMP CO., Bloomfield, New Jersey, U.S.A.-(Assignees of Marden, J. W. ; 19, Laurel Avenue, East Orange, New Jersey, U.S.A.) March 26, 1934, No. 9477. Convention date, April 29, 1933. [Class 39 (i)] A gas- or vapourfilled discharge lamp comprises a thermionic cathode and two anodes, each of which is subdivided into two or more parts, the parts of each anode being so arranged that the discharge with each half-cycle of alternating current is divided into two or more paths. A lamp 1, Fig. 1, is surrounded by a double walled envelope 18, the space between the walls of which is exhausted, and comprises a cathode 8 and two pairs of concentric anode parts 13-16. The anode parts 13, 14 and the parts 15, 16 respectively are connected together by, and mounted on, rods 11, 12 which are connected to the leading-in wires through rods 9, 10. The connecting wires are covered with sleeves of alundum, magnesia or glass. Starting electrodes may be formed by bared parts of the wire or by the rods 9, 10. An insulating member 17 joins the wires 11, 12 together, and the air space between the lamp and the envelope is sealed by the packing 19. The lamp is connected up as shown, the cathode .being energized through a winding 24 and connected to the centre tapping of the winding 27 through a choke 30 or an auto transformer. A nickel sleeve 31 reduces the thermal radiation to the press. The filling consists of a vapour, e.g. sodium, potassium, caesium, or rubidium and a rare gas such as argon or neon at a pressure of 1-4 mms. The cathode may consist of a six mil nickel wire wound on a sixteen mil tungsten wire, which is coiled into a helix having an internal diameter of 3 mms., and the ends of which form connecting terminals. It may be sprayed with a mixture of carbonates in a binder of nitrocellulose amyl acetate. Alternatively, it may consist of a tube provided with an internal heater. In a modification, anode parts 17, 18, Fig. 4, and 19, 20, are mounted respectively on leads 21, 25. Condensation of vapour in the cool portion 11 is prevented by a metal partition 29 which is sealed therein by a cement of sodium silicate and Kaolin, and is provided with a tube 31 to enable both portions of the lamp to be evacuated simultaneously through the exhaust tube 13. The lamp is connected up as shown, a smoothing choke being connected between the centre tappings of the winding 41 and of the heater winding 35. The anode parts may be constructed of bands or rods, which may be corrugated, and may have any of the forms shown in Figs. 5-7. To improve the distribution of the discharge, the electrodes 18, 20, may be connected respectively to the wires 25, 21, by means of rods and insulations. In a further modification, a spherical bulb 55, Fig. 12, comprises a number of spherical anode parts mounted through rods 63 on the head 58 of a pedestal 57. The cathode consists of a helix 59 encircling the head. Dimensions determining the size and the position of the electrodes are given in the Specification. The lamp is baked and evacuated, the carbonates or azides on the cathode being converted into oxides. The filling may be introduced through the glass container by means of electrolysis or by enclosing within the lamp a bottle containing the vapour source. After sealing, the lamp is seasoned by operating it at a current value which is greater than its rating.