GB676054A - Improvements in or relating to a method of manufacturing electric discharge tubes - Google Patents

Abstract

676,054. Thermionic valves. PHILIPS ELECTRICAL INDUSTRIES, Ltd. July 13, 1950 [July 16, 1949], No. 17554/50. Class 39 (i). [Also in Group XI] In making a discharge tube comprising a cylindrical glass bulb without flange which centres the tube in its holder and has a locating member 41 on its periphery, the bulb is placed in a cold state on a plane glass base 28 through which contact pins connected to an electrode system are sealed, and of diameter equal to the outer diameter of the bulb, then the adjacent edges softened by heating but not melted and subsequently sealed together by mechanical pressure such that the shape and diameter of the bulb at the sealing area remains unaltered. The base with bulb on top are mounted in a lower holder 30 of a turret, then the holder raised so that the tube parts are secured also in an upper holder 29, both holders rotating at the same speed. After preheating the contacting edges are locally softened in turret positions 8, 9, 10 (none of the turret positions is shown), and pressed together in position 11 by rollers 40, 40<SP>1</SP>, inclined at 45 degrees, then after heated in position 12 and allowed to cool in positions 13-20. The temperature of the edges is kept below 900‹ C. and the sealing takes less than 15 seconds. The upper holder 29 may supply inert gas to the inside of the bulb to prevent flame combustion products acting on the electrode.