GB692718A - Improvements relating to methods of manufacturing gas-tight vessels - Google Patents

Abstract

692,718. Discharge apparatus. FERRANTI, Ltd. June 18, 1951 [June 16, 1950], No. 15023/50. Class 39(i) The external anode 30 of a thermionic discharge tube has an indented collar 32 against which is located a ceramic ring 34 through which passes a further conductive cylinder 33; the clearance spaces between the ceramic ring and each metallic cylinder are closed by fused glass 47 or other sealing material which is sufficiently viscous in the molten state for it not to be sucked through into the interior of the valve even when the latter is exhausted. Thus during processing, the outgassing temperature may be raised above the fusing temperature of the glass seals; it is stated that as high as 900‹C the molten glass will be too viscous to be sucked completely through a clearance space of .002 in. The inner cylinder 33 supports the grid 33<SP>1</SP>, and has a shoulder 36 bearing against ceramic ring 34. The construction applied to cylinder 30 is also applied to cylinder 33; thus it also has an indented collar 37 against which is located a ceramic plug 43 through which passes the cathode leads 42, 45, the clearance spaces being sealed by fused glass 46 as before. Fig. 1 (not shown) is a simpler tube construction in which the above sealing technique is applied to a cold-cathode gas-filled diode in which the outer metallic envelope forms the cathode.