GB828982A - Improvements in evacuated and gas-filled devices and methods of manufacturing - Google Patents

Abstract

828,982. Thermionic valves. GENERAL ELECTRIC CO. Dec. 20, 1957 [Dec. 28, 1956], No. 39644 /57. Class 39 (1). In the manufacture of a discharge device the various parts comprising it are stacked in the pre-heat zone 2, Fig. 1, of a furnace 1 to commence bake out of occluded gases. Additional means may be provided, such as contacts 53 for cathode heater 44, to activate cathode 43, for example by reducing it from barium carbonate to barium oxide. Any gases evolved may be removed by providing a continuously renewed atmosphere of dry hydrogen by means of inlets 12 and outlets 13. The envelope 16 of the device may be of ceramic material and comprise several sections 23, 32, 40 to which electrode supports 20, 25, 34 may be brazed by means of the upturned flanges such as 28, rings 31 and solder washers 24, 33. In order to provide free communication between the furnace atmosphere and the interior of the envelope washers 33 may be corrugated, Fig. 2. In the next stage of manufacture the device is moved into heating section 3 where the temperature is raised, further degassing occurs, and any hydrogen previously absorbed by the disc 50 of a getter material such as titanium or zirconium is released. At a predetermined temperature washers 24, 33 melt thereby sealing the envelope, and on further raising the temperature the getter material combines with any remaining active gases other than hydrogen. In the final stage, the device is moved into the cool-down section 4 where the solder solidifies, completing the construction of the device, and the getter absorbs all of, or a predetermined amount of the hydrogen entrapped in the envelope. A separate heater 60 may be provided below the disc 50, Fig. 4 (not shown), so that the pressure in the device may be altered during operation. Alternatively the furnace atmosphere may be carbon dioxide in which case the getter may be barium oxide, or the manufacture may be performed in the normal atmosphere by suitable choice of sealing temperature, getter material &c. The method may be used to provide fillings of inert gases by including a predetermined quantity of the required filling in the furnace atmosphere.