GB249847A - Improved manufacture of electric discharge tubes - Google Patents

Abstract

249,847. Naamlooze Vennootschap Philips' Gloeilampenfabrieken. March 28, 1925, [Convention date]. Vacuum tubes.-An electrode for a tube such as a lamp is formed by coating a leading-in conductor and a part of the wall adjacent thereto with a conductive layer, and volatilizing one or more bodies consisting substantially of magnesium to form a deposit of magnesium on the wall in contact with the leading-in conductor. As shown in Fig. 2 a helix 5 of magnesium is mounted on a rod 4 of iron or other material which can be readily deprived of occluded gas. The rod is mounted on a platinum leading-in wire 3 and carries a mica screen 6. A layer 7 of conductive material, such as an emulsion of graphite in water or a binding agent such as aniline, is applied to the lead and on the wall, and the helix is heated by high frequency current induced from a winding outside the tube so that magnesium 8 is deposited on the layer 7 and on the wall. In order to retain and deposit again any magnesium volatilized during operation of the tube, the enclosure 2 for the electrode is made of spherical shape as shown in Fig. 1, and the tube 1 is bent at the ends. In another method the deposit is formed by heating the helix by passage of current, or by a discharge between magnesium electrodes. The filling may be neon at a pressure of a few millimetres of mercury. Specifications 246,538 and 248,023 are referred to.