GB223562A - Improvements relating to electron discharge devices - Google Patents

Abstract

223,562. Metropolitan-Vickers Electrical Co., Ltd., (Assignees of Slepian, J.). Oct. 15, 1923, [Convention date]. Discharge-producing apparatus. - A thermionic device, which mav be used for rectifying alternating currents, comprises electrodes 2, 4 placed less than the tenth of a millimetre apart, the surface of one of the electrodes being made of a material which becomes thermionically active at a lower temperature than the surface of the other, and means are provided for heating the electrodes together to such a temperature that one becomes active while the other remains inactive. The cathode 2 may be made of a mixture of kaolin, carborundum and lampblack, which is moulded into slabs and baked at a high temperature. The anode may be made of similar material, or both electrodes may be made of metal, such as nichel. The active surface 5 of the cathode is coated with oxides, such as those of barium and strontium, which emit electrons at a relatively low temperature, or these oxides may be incorporated in the cathode during the process of manufacture. The electrodes are placed in a chamber 6 having walls 7 of refractory material, the chamber being preferably filled with a gas, such as hydrogen, helium or nitrogen, at approximately atmospheric pressure. Contact-members 9, in intimate contact with the back surfaces of the electrodes, are connected through a transformer 11 to the source of current to be rectified. A heating coil 14, mounted inside the chamber 6, may be connected to the alternating-current source through a switch 15. By means of this coil the electrodes are maintained at a temperature of from 700 to 800‹ C., at which the cathode emits electrons freely and permits the passage of current from the anode. The electrodes may be separated by mica spacers 3, or they may be placed in apparent contact, actual contact only occurring at a few points of the surface, where the high specific resistance of the electrodes prevents the direct passage of current. A number of pairs of electrodes may be assembled in a single casing and connected in parallel to the terminals of the rectifier. Specification 195,691, [Class 39 (i), Electric lamps, Arc &c.], is referred to.