GB549373A - Improvements relating to hermetic seals between refractory metal and vitreous material - Google Patents

Abstract

549,373. Sealing metal to vitreous material. SIEMENS ELECTRIC LAMPS & SUPPLIES, Ltd., and MEADOWCROFT, A. J. May 23, 1941, No. 6653. [Class 36] In a seal comprising metal foil sealed into vitreous material and a conductor thicker than the foil, extending from the latter and in line therewith through the vitreous material to the exterior of the seal, a close helical wrapping of refractory metal is provided on that portion of the conductor on to which the vitreous material is collapsed, the the thickness of the wrapping being such that the strains set up on cooling of the seal are not sufficient to cause fracture of the vitreous material. Thin strips 1, 2 of Mo, with the thickness of their edges reduced as in Specification 512,941, have thick strips 4, 5 of Mo welded thereto at one end while the other ends are welded, as by Ni. on opposite sides of a rod 6 of W, the end of which may be ground away so that the surfaces of the rod and strips are continuous. A ribbon 7, of Mo, W, &c., with a thickness about .05 mm. and a width of 1 mm. is wound in a closed helix about the rod 6 and the end of the strips 1, 2, the extreme ends of the ribbon being preferably welded to the strips and rod, and the turns of the ribbon may also be welded together. The assembly is then sealed into a quartz tube 3, preferably by the process of Specification 541,208. The ribbon 7 may be replaced by fine wire of a diameter about .05 mms. The quartz tube may be integral with the envelope 8 of the container of an electric discharge lamp, or the tube, or a flange thereon, may be sealed into an aperture in the envelope.