US2672569A

US2672569A - Metal envelope tube and method of sealing and exhaust

Info

Publication number: US2672569A
Application number: US94380A
Authority: US
Inventors: Mortimer E Weiss
Original assignee: Sylvania Electric Products Inc
Current assignee: GTE Sylvania Inc
Priority date: 1949-05-20
Filing date: 1949-05-20
Publication date: 1954-03-16
Anticipated expiration: 1971-03-16

Description

March 16, 1954 5, 555 2,672,569

METAL ENVELOPE TUBE AND METHOD OF SEALING AND EXHAUST Filed May 20, 1949 INVENT Mari L merE. We 5 Patented Mar. 16, 1954 METAL ENVELOPE TUBE AND METHOD OF SEALING AND EXHAUST Mortimer E. Weiss, Flushing, N. Y., assignor to Sylvania Electric Products Inc., a corporation of Massachusetts Application May 20, 1949, Serial No. 94,380

Claims. 1

The present invention relates generally to the construction of hermetically sealed and evacuated containers and more particularly to envelopes for electron devices and the exhaust and sealing of such envelopes.

An object of the present invention is the provision 01' a new method for sealing and exhausting a metal envelope electron device and especially sub-miniature electron discharge tubes.

Another object of the present invention is the provision of an improved form of metal envelope sub-miniature tube.

Still another object of the present invention is the elimination of separate sealing and tipping processes now necessary in the construction of hermetically sealed envelopes for electrical circuit elements.

A further object of the present invention is to provide a form of tube structure which will resist the stresses of extreme acceleration supplied to the tube.

Still a further object of the present invention is the simplification of electron discharge tube construction.

The foregoing objects and others which may appear from the following detailed description are accomplished, in accordance with one aspect of the present invention, by providing an envelope which may be evacuated and sealed and which comprises two main parts. header, comprises a metal eyelet having a flange at one end and a button of glass sealed in the tubular part of the eyelet. The lead-in wires for connection to the elements within the tube pass through and are sealed into the glass button and the operative structure within the tube is supported primarily by extensions of the lead-in wires within the interior of the tube. The second main part of the tube envelope is a tubular metal can closed at one end and having a flange at the other. The metal closure or can may be an active element of the tube such as the anode in a pentode structure or it may, if desired constitute at least in part, a support for a closespaced anode of a triode structure. The envelope is assembled by replacing the flanged metal can over the header eyelet with the flanges in contact. They are then spot welded together to hold them together as a single unit. The unit is then inserted in a small bell jar connected to an exhaust port of an exhaust machine which may be of conventional form. The bell jar and the tube unit within are then exhausted according to a schedule applicable to such machines. The tube envelope may be heated by induction in several stages of the exhaust schedule. In the final exhaust, a. heating coil may be placed over the bell jar whereby a very concentrated radio frequency field is coupled to the adjacent flanges of the envelope causing them to flash weld. Thereafter the evacuated tube may be removed from the bell jar and a conductive get- One part, the 5 ter ribbon between one of the external leads and the enclosing envelope flashed electrically to complete the activation of the tube.

The present invention will be more fully understood by reference to the following detailed description, which is accompanied by a drawing. in which Figure 1 illustrates in exploded eleva-- tional view an embodiment of the present in-- vention, while Figure 2 illustrates in partial section a bell jar exhaust arrangement for use with the tube structure of Figure 1.

The exploded elevational view shown in Figure 1 includes a metal can l0 hermetically closed at one end by a header l2 and having an outwardly extending flange M at the other end. The envelope is completed by a base header l5 including a metallic eyelet having a tubular portion it and an outwardly extending flange l8. Sealed within the tubular portion Hi of the eyelet is a glass button through which lead-in conductors 24 pass. To the upper end of lead-in conductors 24 are attached the several internal elements of the tube. In the specific example illustrated in Figure 1, there is included a filamentary cathode 26 attached at its lower end to one of the lead-in conductors 24 and at its upper end to a tensioning arrangement 28. The tensioning arrangement 28 is supported on a rod 3i! passing through

spacers

32 and 39. At its lower end, rod is connected to another one of the lead-in conductors 24. A number of

grids

36 and 38 are concentrically arranged about the cathode 2t and are maintained in position by side rods 40 passing through spacers 32 and-39. Appropriate ones of the side rods 40 are also connected to lead-in conductors 24. In the pres- ;ent embodiment the anode of the tube is conthe metal envelope is entirely shielded from the influence of exterior fields, it is contemplated that the evacuated envelope be gettered by the use of a conductive ribbon getter 46 connected between flange I8 and one of the lead-in conductors 24.

The electron discharge device according to the present invention is preferably assembled by telescoping the two sections shown in Figure 1 together and spot-welding flanges l4 and [8 to- I gether in one or more points in order to main tain their relative position. The unit as thus assembled is inserted as shown in Figure 2 on an exhaust port 50 of an exhaust machine. Port 50 is a conductive tube which may if desired be slit for a distance along its length as indicated at 5| in order to insure that it is not excessively heated by the radio frequency field used for bombarding and sealing the tube. The port 50 is conductively connected to the frame structure of the exhaust machine. One of leads 24 which is connected to filament 26 is bent outwardly toward one side far enough so that it contacts the exhaust port 50. The others are grouped together so that they contact a central inner tube 52 which is insulated from the remainder of the structure by heavy rubber tubing 53. By making a connection of a source of power to the frame of the exhaust machine and to the inner tube 52, lighting power for the filament 26 as may be required during the exhaust stages is provided. The discharge tube as a whole is covered with a glass bell jar 55 which fits within a compressible rubber sealing sleeve 55. Sleeve 55 is compressed about the lower end of bell jar 55 by a compression ring 51 threaded over a mount member 58. Vacuum is applied to the tube through, exhaust tube 52 as indicated, by the arrow at the lower end of Figure 2. As the ex.- haust proceeds, the tube unit may be heated by an external bombarding coil such as coil 60 as required. In the final exhaust stage, a very concentrated radio frequency field of, say 580 kilocycles, is applied by means of another coil 50 closely coupled to the flanges i4 and it. This makes a radio-frequency flash weld in a small number of cycles of alternation of the 60 cycle supply voltage for the radio frequency generator, say from 2 to 5 cycles. Thus the interior of. the tube envelope is hermetically sealed in from i,- to $3 of a second. Thereafter, the compression ring 51 is loosened, relieving, the pressure of the rubber sleeve 58 against the lower end, of hell jar 50. Bell jar 55 is removed and the completely exhausted electron discharge tube is removed from the exhaust machine. A suitable source of potential is applied. between the. metal envelope Ii andthev one of lead-in conductors 24 which is connected to the internal ribbon getter 46 thus flashing. the getter.

It will. thus be seen that I have provided an improved type of metal envelope tube. which. may be: made of any convenient size: including the extremely small sub-miniature sizes and which doesv not require separate sealing and tipping processes normally necessary with. glass envelopes. The. construction has been simplified since the metal envelope may constitute an active element oi the tube or itmay be used in a conventional manner to. support a close-spaced. anode for a triode structure. The elimination of a separate. anode structure and the sleeves neces Sm to anchor the supporting micas tothe anode leads: facilitates assembly. It should be noted that the flanges provided on the. stem portinn and. on the canportion serve a double purpose. They provide the necessary stress relief for the glassbase-header from the thermal shock which would occur in welding if the flange were not provided. Because of the comparatively large diameter of flanges I1 and I8, the radio frequency flux used in welding is confined to the outer periphery so that the weld which occurs is restricted to a very narrow zone around the extreme outer edge of flanges I4 and 18. While I have particularly shown and, described an embodiment of the present invention, it should be distinctly understood that my invention is not limited, thereto, but that modifications withinthe scope. of. the invention. may be. made.

What I claim is:

1. An electron device containing circuit elements within a sealed casing, said casing including a flanged metal body part and a header part, said header part including a flanged tubular metal eyelet having a button of insulating material within the tubular part and a number of lead-in conductors passing through said button, said flanges being welded together around their outer peripheral edges.

2. An electron device containing circuit elements within a sealed casing, said casing including a flanged metal body part and a header part, said header part including a flanged tubular metal eyelet having a glass header button within the tubular part and with a plurality of leadin conductors passing through said button, said flanges being hermetically joined together in a.

narrow zone about their outer peripheral edges. 3. An electron discharge device including a.

casing having two parts, one being a flanged metal can and the other a header part including a flanged tubular eyelet having a glass header button within the tubular part, lead-in conductors passing through said button at least a cathode and a number of control electrodes surrounding said cathode mounted within said casing and connected to said conductors, a number of insulating washers secured to said control electrodes and having their edges bearing against the interior of said can and said flanges being hermetically sealed together around their periphery, said can serving as an anode for said device. 7,

4. The method of fabricating, a sealed electron device which in completed form includes a flanged hollow metal body part and a header part including a flanged tubular eyelet and lead-in conductors passing through insulating material 5.. The method of fabricating a sealed electron.- device which in completed: form includes a flanged metal body part and a. header part including a flanged tubular eyelet and lead-in conductors passing throughinsulating material.

inthe tubular portion of said eyelet which, in-

cludes the steps of placing said twoparts together with the: flanges contacting one another, placing said devicein an evacuated container to evacuate the space within said device, heating the outer periphery of said flanges with a high frequency field to cause a complete peripheral weld. and thereafter. removing; said device from within.

said container;

MORTIMER E. WEISS...

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date Re. 21,163 Rose, Jr. July 25, 1939' 2,162,234. Thomas l June 13, 1939 2,181,366 Edwards etral'. Nov- 28, 1939*. 23855939 Green Dec. 26, 1939 2229;436 Beggs 1 Jan. 21, 1941" 2,425,593 Brim Aug. 12', 1 94?