GB1039293A - Improvements relating to glass-to-metal seals - Google Patents

Abstract

<PICT:1039293/C1/1> A glass-to-metal seal comprises a circumferentially continuous fillet of glass sealed to and maintained under compression between overlapping tubular metal parts, in which one of the metal parts only, without the other part, forms a wall supporting at least a portion of the boundary of the fillet while an end of the other part is wholly embedded in and sealed to the fillet. In one example, being the cathode seal of a mercury arc rectifier, a coaxial tubular portion 5 is hermetically sealed at one end by welding on to the steel circular base 4 of the cathode pool, the other end being received by a channel 7 provided upon the adjacent circular rim 8 on the aperture 9. The channel 7 is provided by outwardly flaring the tubular end section 10 of rim 8, the channel being contained between the inner wall of section 10 and the outer wall of a refractory tube 11 (e.g. graphite). By inverting the apparatus, glues can be poured into the channel, or fed in as a ring and then fused, the end of tubular section 5 then being contained within the glass. Preferably the glass easily wets the parts 5 and 8 but not part 11. The glass has a lower expansion then the component part 8. If necessary the parts 5 and 10 may be coated with a vitreous enamel to aid wetting. The glass may be fused by heating the parts 8, 5. To provide a long leakage gap the refractory part 11 may be removed after the seal is formed.