GB481940A - Improvements in the sealing of electric lead-in wires into glass envelopes - Google Patents

Abstract

481,940. Sealing wires into vitreous material. ROBINSON, E. Y., and METROPOLITAN-VICKERS ELECTRICAL CO., Ltd. Sept. 16, 1936, No. 25264. [Class 36] In sealing three or more leading-in wires into glass envelopes, such as thermionic valves, the wires are held in the correct angular or circular spaced relationship by means such as a jig 7 so that they project into the open end of the glass bulb or tube 5 which is softened by the heat of gas flames 18, the glass then being pressed in between the leading-in wires to form inwardly directed tongues which meet and unite with one another to make a vacuum-tight seal and end closure for the bulb or tube 5. The means for holding the wires in the correct relationship may comprise part of the internal electrode structure, such as an insulating crossframe, whilst the tube into which the wires are sealed may constitute the bulb of the valve. In the example the apparatus comprises two coaxial shafts 1, 2 which are rotated at the same speed in the same direction. The shaft 1 is hollow and carries spring-clips 4 which engage the tube 5 and hold it in position. The tube 5 has a reduced extension 6 which fits into the bore 3 of the shaft 1, preferably with such good contact that air or a neutral gas may be blown from the left-hand end of the shaft 1 into the tube 5, or a rubber washer or gasket may be used to obtain a gas-tight union between the tube 5 and shaft 1. The shaft 2 carries the jig or wire-carrier 7 which, in the example has six holes parallel with the axis of the shaft. A collar 11 fixed upon the shaft 2 forms a mounting for pivots 10 for a series of bell-crank levers or fingers 9 which terminate in wedgelike jaws 8, the levers being actuated by links 13 connected to a slidable collar 15 on the shaft 2. The heating is preferably continued after the formation of the seal, to remove the strain from the glass, while the glass may be blown out slightly by carbon dioxide admitted through the tube 1, assisted by centrifugal action. The sealed leading-in wires may be of such thickness that their externally projecting portions may serve as contact pins, or supports therefor. A leading-in wire or a glass exhausting-tube may be sealed into the centre of the tube 5, collapse of the exhausting-tube being prevented by a reinforcing collar or liner such as a longitudinally split collar which may subsequently be removed. Specification 369,349, [Group XL], is referred to.