Patent GB-620475-A (GB)
Title: Improvements in ionic discharge devices
IPC: H01T2/02
Filed: 1944-08-31
Abstract: 620,475. Electric discharge devices. WESTERN ELECTRIC CO., Inc. Aug. 31, 1944, No. 16629. Convention date, Sept. 8, 1943. [Class 39 (i)] An ionic discharge device comprises a vessel containing an ionizing gaseous medium, an anode electrode and a cathode electrode, between which are provided one or more electrode structures adapted to act both as cathode and anode electrodes, these electrode structures and the two electrodes defining a plurality of discharge gaps across which the discharge passes in succession, at least one of the said gaps having a corona point element directed theretowards so as to initiate the discharge thereacross. The discharge device shown in Fig. 1 comprises an envelope 20 having pairs of closely-spaced parallel cold electrodes 24 and 25, and 26 and 27, and having corona points 37 and 38 in the form of hook-shaped wires with pointed ends directed towards the gaps between the electrodes 24 and 25 and 26 and 27. Each electrode is formed of a rectangular-shaped bevelled metallic plate, such as molybdenum, provided with a central elongated embossed portion 31, and the electrodes 24 and 26 are provided with a layer or plate of highly refractory metal, such as tungsten, on the embossed central portion, to constitute a cathode surface, the embossed central portions of the electrodes 25 and 27 constituting anode surfaces. The electrodes 25 and 26 are connected by a strap 35. The distance between the surfaces 31 and 32 is not materially greater than 0.1 of an inch, and is preferably 0.075 of an inch. The electrodes are supported by angle-brackets 33 secured to the rear surfaces of the electrodes and welded to spaced conductors or supports 34 projecting from the dished stem 21 of the envelope, the conductors 34 extending to three external terminals 22 supported on a disc base 23. Initiation of conduction between the cold electrodes is facilitated by the presence of one or more spots of radium bromide or radium chloride paint 36 deposited on the side walls of the envelope 20 adjacent the gaps between the electrodes. In a modification the electrodes forming one gap are arranged perpendicular to the electrodes forming another gap. In a further modification a common cathanode, that is, an electrode serving as an anode and as a cathode for different gaps, is located between two electrodes shaped convexly theretowards, the cathanode carrying on one side a cathode rod disposed so that the discharge between the cathode rod and the co-operating anode is concentrated in a definite part of the space between said electrodes. The electrode located on the anode side of the cathanode may be provided with a cathode rod. In a further modification a plurality of adjacent discs serve as cathanodes in which inserts of refractory metal form the cathode surfaces. The corona points for a plurality of gaps may be supported by conductors attached to a common cathanode. An insulating shield member may be provided which has apertures through which pass stub wires connected to the electrodes. The electrode assembly is surrounded by a gas or a mixture of gases such as argon, helium, hydrogen, nitrogen, carbon dioxide and oxygen, a desirable combination being argon and hydrogen or argon and oxygen. The proportions may be argon 80 per cent and oxygen 20 per cent, and the volume of the envelope 20 may be 200 cubic centimetres. The pressure of the gas or mixture of gases may be from 20 cms. of mercury to 5 atmospheres, a desirable pressurerange being from 50 to 76 cms. of mercury and a more limited range being between 60 and 67 cms. of mercury.