GB456642A - Improvements in or relating to high-pressure mercury vapour discharge tubes - Google Patents

Abstract

456,642. Uniting metal to vitreous material by heat. NAAMLOOZE VENNOOTSCHAP PHILIPS' GLOEILAMPENFABRIEKEN, Emmasingel, Eindhoven, Holland. June 5, 1936, No. 15800. Convention date, Aug. 31, 1935. [Class 39 (ii)] In a seal for the leading-in wires of a highpressure mercury vapour discharge tube of quartz, wherein the leading-in wires are led through the quartz wall with the interposition of one or more transition glasses, at least a portion of the transition glass is so arranged inside the quartz tube that at its end adjacent to the interior of the tube it bears on the quartz with a gradually decreasing thickness. In one method of forming the seal, a quantity of the transition glass is introduced, preferably by suction, into one end of the quartz tube 1, after which the end of the tube is heated to fuse it to the plug of glass drawn therein. The length of the plug within the quartz tube should be at least 1À5 times, preferably three or four times, the thickness of the quartz wall. The hot plug next has blown into it a current of gas, for example air, to form a longitudinal aperture 3, Fig. 2, in such manner that the inner side of the plug 2 has formed on it the edge 4 which is very thin at the top and becomes gradually thicker downwardly. The tungsten wire 5, Fig. 4, coated with a layer 6 of transition glass is next inserted into the aperture 3 and so held that, when the glass layer 6 and plug 2 are sealed together, the transition glass around the wire projects in the form of a rounded hillock 7. The glass used as the transition glass may have the composition described in Specification 431,923.