US2324556A - Manufacture of sealed articles - Google Patents

Description

y 1943- 1.1,1'. LBROWN MANUFACTURE OF SEALED ARTICLES Filed June 4, 1942' TO PUMP 70 SOURCE OF CONTROLLED GAS IN I/EN YIUR 7'.L.BROWN PRESSURE ATTORNEY Patented July 20,

or 15 STATE MANUFACTURE st PATENT OFFlCE John T. L. lirown, Short Hills, N. J.-, alsignorto i v Bell Telephone Laboratories Incorporated,

New York, a corporation, New York Application June 4,1942, Serial N... 445,757

I 11 Claims.

The present invention relates to methods and apparatus for the sealing of gas-tight envelopes,

- particularly those adapted to contam electricalw apparatus which it is necessary to maintain in an evacuatedor gas-filled atmosphere.

The present invention isparticularly adapted" to the evacuation; gas filling and sealing of glass- "enclosed magnetic reed switches which are provided with one terminal in theform-of a metal r tube through which the switches areevacuated and filledwith gas. Prior to the present invention, switches of this typewere evacuated and filledwith gas by individually coupling the metal tube ports of each switch to thepumping station and gas source. They weref'then sealed by;

open at both ends, thus forming port thrcugh which the interior of the envelope communicates with the outside atmosphere. In-order to. pro- I vide a convenient terminal for soldering, a bent piece of tinned copper wire or other suitable. metal wire maybe inserted inthe'metal tube leaving a substantial portionof the wire'protrudsqueezing the ends of the tubes flat and welding I the flat sections together.

This process was similar to that ordinarilyused iv in the manufacture of vacuum tubesand lamps.

This method of individualhandling could becarried out at low cost in the manufacture of vacuum tubes and lamps, but this low cost was an rived at to a large extent by providing compli-,

cated machinery to perform a sequence of individual operations on identical parts being fed continuously to it. Wher it is not desired to produce glass-enclosed apparatusof astandardtured into The apparatus shown in Fig. 2 consistsofa 1 cylindrical glass evacuation chamber 8 having a removable cover 9 fitted to the body of the evacuation chamber by means of a ground joint 10. A

ized design in extremely large quantities, the cost or such individual handling may be excessive.

According to the present invention a method and apparatus are provided whereby such articles may be evacuated, filled with gas and sealed in 7 ing. This wir is subsequentl sealed in the metal tube by solder at the time the glass envelope is sealed oil. The portion of the tube 2 and the lead 3 within the envelope are flattened and. have welded to their flattened portions two reeds 5' and it formed of magnetic material. The

flattened endof the tube 2 has an opening 1 in its sideyfurnishing means through which theinterior of the envelope communicates with the outside atmosphere as stated above. The construction and operation ofthis type or switch are more particularly described and claimed in the copending application of W. B. Ellwood, Serial No. 198,629, filed March 29, 1938 which has ma- "port ll in the cover furnishes a means whereby the chambercan be evacuated andfilled with gas.

batches, thus avoiding thenecessity for indiated, filled with gasand sealed by th method and apparatus of the present invention; and" Fig. 2 is a front sectional elevation-of a form of the apparatus of the present invention} The switch shown in Fig; 1 is madeup ofa glass envelope I having a metal tube 2'sealed in one end and a solid wire lead 3 sealed in the opposite end. The metal tube 2 and the lead 3 are made of a metal having a coefficient of expansion approximating that of glass, such as an alloy of Sl pe: cent nickel and 48 per cent iron. The metal tube is preferably copper plated to facilitate subsequent sealing with solder. tube is The structure and Within the chamber 8 a cylindrical holder 12 is suspended from the cover 9 by any suitable means l3. The bottom H of the cylindrical holder I2 is providedwith perforations, whichare slightly larger in diameter than the metal tubes .2 of the switches l5. 'I'hese perforations are uniformly a spaced so that-when the tubular metal ports are inserted therethrough, the switches l5 are regularly and snugly positioned within the cylindrical 1 holder. The tubular metal ports protrude freely I through the bottom of the holder.

The lower portion of the evacuation chamber 1 is connected by means of a tube It to an auxiliary container H which contains a supply of molten solder ill. The auxiliary container I1 is c0nnected by means of an outlet I! to a suitable source of gas pressure. The entire apparatus. with the exception of the holder I 2 and the sup- 1 port I3, is preferably made of glass, although obviously any suitable material maybeQused. i,

In the operation of the method of the present invention; a plurality of switches, similar to that] shown in Fig. 1, are placed within the cylindrical holder I2 so that their hollow metal tube ports are downwardly disposed and protrude from the bottom of the holder through the perforations,

Patent No. 2,289,830 issued] July 14,

the metal tube openings forming substantially a horizontal plane. The cover 9 is then lowered into place on the top of the evacuation chamber together with the support It and the holder l2, and a tight seal is established at the ground joint Ill. The solder I8 is maintained in a molten state throughout the entire procedure by any suitablesource of heat (not shown). During the insertion of the holder into the evacuation chamber 8 and during the subsequent evacuation of this chamber, the solder is maintained within the chamber H by a portion of the solder in the tube it which has been allowed to solidify so asto close the tube.

After the switches have been inserted in the evacuation chamber, the chamber is evacuated through the outlet II to an absolute pressure or about millimeters of mercury. The portion of the evacuation chamber containing the switches, and the switches therein, are heated to about 100 C. to aid in the elimination of adsorbed gas. The chamber is then flushed with a mixture of hydrogen and helium, re-evacuated and filled with a mixture of hydrogen and helium, the hydrogen pressure being about 130 millimeters of mercury and the helium pressure being about 630 millimeters of mercury. Obviously any other desired inert gas may be employed.

In order to seal the switches after they have been filled with gas, heat is applied to the tube l 6 by any suitable means, such as by an open gas flame, in order to melt the solder contained therein. Suflicient pressure is then applied to the solder in the auxiliary chamber I! by the introduction of gas to force the solder to such a level in the evacuation chamber that the metal tubes of the switches are immersed to a depth of about one-eighth inch.

The heat of the solder causes expansion ofthe gas within the switches, which results in bubbling of the gas from the bottom of the tubes. After the bubbling has stopped, the helium pressure within the evacuation chamber is increased by about 30 millimeters of mercury and the gas pressure within the auxiliary chamber i1 is increased correspondingly to maintain the proper level of solder in the evacuation chamber. The added pressure forces the solder a considerable distance up inside the metal tubes, where it immediately cools and commences to harden.

The pressure within the chamber I1 is then reduced to withdraw the solder from the evacuation chamber and the solder within the tube 16 is then allowed to solidify by cooling. The cover may then be removed from the evacuation chamber and the finished switches can be taken from the holder. The solder within the chamber i! may be maintained in a molten state during all operations.

A eutectic solder made up of 63 per cent tin and 37 per cent lead is suitable for this process because of its low melting point and because of the fact that it changes completely from a liquid to a solid within a small temperature range. Another suitable solder, which, however, has a higher melting point, i made up of 96 per cent lead, 2 per cent tin and 2 per cent silver.

The invention has beendescribed in terms of its specific embodiments, but certain modifications and equivalents will be apparent to those skilled in the art. Such modification and equivalents are intended to be included within the scope of the present invention which is to be limited only by the fair and reasonable scope of the appended claims.

What is claimed is:

1. In the manufacture of electrical devices on closed in gas-filled sealed glass, tube which are adapted tobe sealed oil by closing tubular metal ports sealed therein, the steps which comprise suspending a plurality of said glass-enclosed devices, while yet unsealed, in an enclosed chamber in such manner that their open metal tube ports are downwardly disposed and have. their chamber with the desired gas under the desired pressure, introducing a molten solder into the lower portion of saidchamber until the level of the solder is slightly above the open ends of said metal tube ports, increasing the gas pressure within the chamber to force the solder part way up in said metal tubes, wherein it solidiila, and withdrawing said solder Irom the chamber.

2. In the manufacture of electrical devices enclosed in gas-filled sealed glass tubes which are adapted to be. sealed off by closing metal tube ports sealed therein, the steps which comprise suspending at least one ofsaid glass enclosed devices, while yet unsealed. in an enclosed chamber in such manner that its metal tube port is downwardly disposed, alterin the atmosphere within said chamber to correspond with that desired within the glass enclosed device and sealing said metal tube ports by introducing molten solder into the lower portion of said chamber until the level of the solder is slightly above the open end of said metal tube ports.

. 3. In the manufacture of glass envelopes which are adapted to be sealed off by closing protruding tubular ports, the stem which comprise s'us-' pending at least one of said envelopes, while yet I unsealed, in an enclosed chamber in such manner that its tubular portis downwardly disposed, altering the atmosphere within said chamber to correspondwith that desired within said envelope and sealing oil said tubular port by introducing a solidiflable liquid sealing material into the lower portion of said chamber until the liquid level is slightly above the open end of said tubular port. 7

4. In the treatment of glass envelopes having hollow metal tubes sealed in the walls of said envelopes, the steps comprising placing at least one of said envelopes, having its metal tube unsealed, within a chamber, alteringthe atmosphere within said chamber to correspond with that desired within the envelope and'estabiishing contact between the open end of saidgmetal tube and a pool of molten solder within; said chamber whereby the envelope is sealed.

5. In the manufacture of enclosed gas-tight envelopes, the steps comprising placing within a chamber at least one of said envelopes having an unsealed opening, altering the atmosphere within said chamber to correspond with that desired within the envelope and sealing said'opening, by introducing a liquid solidii'lable sealing material into the lower portion of said chamber until the liquid level is above the area of said envelope surrounding said opening.

6. In the manufacture of enclosed gas-tight envelopes, the steps comprising placing within a velopes and establishing contact between the areas of said envelopes surrounding said openings anda pool of molten sealing material within said chamber, whereby the openings in said envelopes are sealed. l

7. In the manufacture of enclosed gas-tight envelopes, the steps comprising placingwithin a chamber at least one of said envelopes having an unsealed opening, altering the atmosphere within said chamber to correspond with that desired within said envelope and establishing contact between the area of said envelope surrounding said opening and a pool of liquid solidiflable sealing material within said chamber whereby the opening in said envelope is sealed.

8. A device for altering the atmosphere within and sealing glass vessels which are adapted to be sealed oil by closing protruding tubular ports, which device comprises an enclosed sealing chamber, means within said sealing chamber adapted to support a plurality of said glass vessels with their tubular ports in a downwardly disposed direction and with their tubular ports defining substantially a horizontal plane, means said duct into said sealing tight ground glass joint, said opening being sumciently large to permit the insertion of a holder for said glass vessels, a holder forsaid glass vessels within said chamber adapted'to support said glass vessels with their tubular ports in a downwardly disposed direction,means for withdrawing and introducing gas into the space defined by said glass chamber and cover, and means for introducing liquid sealing material into the lower portion of said chamber.

10. A device for altering the atmosphere within and sealing gas-tight vessels having scalable protruding tubular ports, which device comprises f an'enclosed chamber, means for introducing and. v withdrawing gas from said chamber, supporting l means within said chamber adapted to support a plurality of said vessels with their tubular ports disposed in a downward direction and with the openings of said tubular ports disposed substantially in a horizontal plane and means whereby molten material may be introduced into the lower portion of said chamber until its surface within the chamber is sufilciently high tocontact said scalable ports. l

11. A device for altering the atmosphere within and sealing gas-tight vessels havingsealable ports which comprises an .enclosed chamber adapted to be evacuated, supporting meansw'lthin said chamber for supporting at least one of said vessels and means for establishing contact within said chamber between the surface of a pool'of molten sealing material and the scalable port of at least one of said vessels so supported.

JOHN T. L. BROWN. 1

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