US2219438A

US2219438A - Seal

Info

Publication number: US2219438A
Application number: US304352A
Authority: US
Inventors: Beeson Eric John George
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1938-10-31
Filing date: 1939-11-14
Publication date: 1940-10-29
Anticipated expiration: 1957-10-29

Description

Oct. 9 E. J. G. BEESON SEAL - Filed Nov. 14, 1939 Fig. 5.

eorge Beeson,

Fig. 2

- a seal comprising my r the like, may be secured,

Patented ct.'29, 1940 UNITED STATES SEAL Eric John George Bceson, Southwell, England, assignor to General Electric Company, a corporation of New York Application November 14, 1939, Serial Nb. 304,352 In Great Britain October 31, 1938 2 Claims. (01. 176-50) My invention relates to the sealing conductors into vitreous envelopes. More particularly the invention relates to seals for envelopes which have to withstand high temperatures and therefore have to be made of quartz or high melting point glass.

One object of my invention is to provide a preformed seal which can be sealed into an envelope when required.

The invention consists in sealing a conductor in a stem of refractory vitreous material, such as quartz or hard glass, with a lead or conducting member projecting from one end which may form an electrode to which an electrode, filament or and a connecting lead extending through the other end but enclosed in an evacuated chamber formed integral with the stem which prevents the connecting lead from being damaged or oxidized. The invention further consists in so forming the seal that it can be fused into an aperture in an envelope without the heat necessary for the fusion oxidizing or otherwise damaging the conductors projecting from it.

The invention will be better understood by reference to the accompanying drawing in which Fig. 1 is a longitudinal view, partly in section, ,of

invention; Fig. 2 is a detail view of part of the conductor employed in the seal of Fig. l; and Fig. 3 is a view simliar to Fig. 1 of a modified form ofseal comprising my invention.

In carrying the invention into effect as illustrated, the seal consists essentially of a thin strip of suitable metal I, such as molybdenum, to one end of which one or more strips of wire or ribbon 3, which may also be of molybdenum, are elec-. trically, welded. At the other end of strip l is secured one or more short pieces of metal foil 4 (Fig. 2) which project into a slot 5 formed in the end of a lead 6. When the pieces 4 are inserted in the slot 5, they may be spot welded to make a good electrical connection.

The assembled conductor is inserted in a quartz or hard glass tube or sealing member 2 which has previously been compressed so as to form an enlargement I. The said tube is then closed at one end and, preferably that end enclosing the lead 6, connected to a vacuum pump at the other end. When the tube is evacuated and while still connected to the pump, the tube is fused down on to the molybdenum strip I, and to portions of the lead 6 and the strip 3 to form the stem or seal portion, as shown in Fig. 1. The openend of the tube 2 is then sealed and disconnected from the vacuum pump, forming a chamber 9 in which the portion of the ribbon 3 which projects be-- yond the seal is enclosed. This chamber forms a test chamber which can be used at any time to ascertain the condition of the seal. The'portion of electric of the tube surrounding the lead 8 may now be removed by cutting it at the point l0 and the seal is then complete and can be stored until required. When the seal is to be put into use, a spark test coil terminal can be applied to the exposed lead 6. Should the seal be faulty, air will have leaked into the closed chamber and its presence will cause atypical glow when the test coil is energized.

.In order to secure one of these seals into an envelope ll of refractory vitreous material, an aperture 8 is blown in the wall of the envelope of sufiicient diameter to enable the portion carrying the lead-in conductor 6 to be inserted. The seal is then inserted into the aperture 8 until the edges of the aperture rest on the enlargedportion 1 of the seal. The seal can then be joined to the envelop II by applying heat at the point of contact of the envelope and the enlargement 'l and this heating will not be sufilcient to cause any damage either to the ribbon 3 or the leadingin conductor 6. The evacuated chamber 9- protects the connecting lead 3 from oxidation and damage, and when the seal is secured to a vessel and the device is complete, the chamber 9 maybe removed.

In the form shown in Fig. 1, the main portion of the seal is within the envelope, but if desired it may be outside the envelope as shown in Fig. 3, where the enlarged portion 1 is shown at the inner end of the seal.

As it is diificult to make a seal between quartz and a conductor, it is convenient to make up seals as described above, so that they are in stock when a particular piece of apparatus requiring them is urgently needed.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A seal for leading an electric conductor through the wall of a vitreous envelope comprising a stem of refractory vitreous material having a conducting member projecting from one end and a connecting lead extending from the other end and enclosed in an evacuated chamber formed integral with the stem to prevent oxidation of and damage to said lead, said conducting member and connecting lead being electrically connected within the stem and the stem being formed with an enlargement which can be fused into an aperture in said envelope without the heat necessary for fusion deleteriously affecting said electric conductor. r

2. A seal for leading an electric conductor through the wall of a vitreous envelope as claimed in claim 1 in which the conducting member and the connecting lead are secured to oppositeends of a thin metal strip hermetically sealed within the Stem.

' ERIC JOHN GEORGE BEESON.'