GB502551A - Improvements in and relating to methods of sealing metal to glass - Google Patents

Abstract

502,551. Sealing metal to glass by heat. BRITISH THOMSON-HOUSTON CO., Ltd. June 15, 1937, No. 16624. Void. Convention date, June 16, 1936. [Class 36] [Also in Group II] A method of uniting a metal member and a glass member having different coefficients of expansion comprises sealing the metal member directly to the glass member, heating the structure so formed to the annealing point of the glass, and then cooling the member having the higher coefficient of expansion more rapidly than the other member. If the coefficient of expansion of the metal is not too much higher than that of the glass, the cooling may be effected by merely allowing the sealed objects to cool in the open air at ordinary temperatures; alternatively, a portion of the metal may be immersed in a liquid. The example shows a base assembly for electric lamps and the like, of the kind described in Specification 4,71,301 comprising a comparatively thick dish-shaped body 10, preferably of a borosilicate glass, into which prongs 15 are sealed by means of cup-shaped thimbles or flares 16 attached thereto. The flares 16 may be made of an alloy such as that known as "Fernico " and may be formed with tapering edges. Sealing is effected by flames of reducing gas, such as hydrogen, accompanied by pressure , upon the upper ends of the prongs, after which the assembly may be placed in a furnace such as that shown for the subsequent re-heating and cooling. This furnace comprises a container 22 with a refractory lining 23 and containing an electric heating-coil 24. A well 25 attached to the bottom of the container has inlet and outlet pipes 27, 28 respectively for a cooling-liquid, preferably water. Heating is effected with the sealed assembly arranged at right-angles to the position shown, so that the bottoms of the prongs 15 rest on the bottom 26 of the furnace, the temperature attained being about 600 to 650‹ C. The assembly is then turned and the prongs 15 inserted through the tubes 29 into the circulating water 31. The metal is thus cooled rapidly, while the glass 10 is preferably cooled down slowly through the strain point. Specification 368,934, [Group XI], also is referred to.