US1452275A - Method of making leading-in conductors - Google Patents

Description

Apr. 17, 1923.

W. G. HOUSKEEPER METHOD OF MAKING LEADING-IN CONDUCTORS Filed Feb. 27, 1920 W A e 8 L r fl 0 v MG m/Mfi m 54 Patented Apr. 17, 1923.

UNITED STATES WILLIAM G. 301733, 01 NEW YORK, N. Y., ASSIGNOB TO V 1,452,275 PATENT OFFICE.

COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

KETHOD OF MAKING LEADING-IN CONDUCTOBS.

Continuation of application Serial ll'o. 158,574, filed March 80, 1917. This application filed Iebruary 87,

. 1920. Serial No. 881,706.

To all whom it may concern:

Be it known that I, WILLIAM G. Hous- KEEPER, a citizen of the United States, residing at New York, in the county of New 6 York and State of New York, have invented certain new and useful Im rovements in Methods of Making Leadingn Conductors, of which the following is a full, clear, concise, and exact description.

This invention is a continuation of application, Serial No. 158,574 filed March 30, 1917 and relates to leading-in conductors for incandescent lamps, mercury arc rectifiers, vacuum tubes, and the like, and more 16 particularly to those which are made from one or more of the base metals.

Extreme care has heretofore been considered necessary in scaling in base leadingin conductors, to secure a seal which, under 20 the conditions of operation, will prove satisfactory. A seal constructed without attention being paid to the difierence in coeflicients of expansion of the materials used is incapable of preventing air from passing into an evacuated bulb or a sealed inert gas from escaping out into the atmosphere. It is common knowledge that the difiiculty thus experienced has been obviated by the use of socalled fluxing material. \Vhen the latter is used there appears to be an absorption of any oxide which may have formed on the surface of the conductor, or in some cases actual welding of the flux to the surface of the conductor. Such flux is usually chosen so that a perfect union may be had with the glass or other vitreous material of the evacuated bulb.

As the use of a flux, however, is undesirable, inasmuch as it adds to the expense involved by requiring an additional operation, attempts have been made to make a satisfactory seal without using a fluxing material. In practically every case, however, it has been found that great care must be exercised in preventing the formation of oxide on the surface of the conductor. Attenuated and looped parts have been scaled into vitreous materials which appear, on experimentation, to withstand the heating and cooling of the seal without exhibiting any leaks. The manufacture on a commercial scale of such seals, however, .is prohibitive on account of the failure of a large proportion due to traces of oxide on the surface of the conductor. Moreover, a leadmg-in conductor made in this way is extremely weak mechanically, and has proven to be too fragile for commercial use.

An object of this invention is to provide a method by which base leading-1n conductors may be sealed in las or other vitreous material without t e use of a flux or w1thout the exercise of care to prevent oxidation on the surface of said conductor.

Another object is to so shape that portion of the leading-in conductor which isretamed 1n the vitreous material that the above may be accomplished without necessitating a reduction in cross section of said conductor.

It has been found that a very satisfactory seal may be made if due consideration is given to the strains and stresses which are present 1n the composite structure formed y imbedding a metallic conductor in glass or other vitreous material. While the inventlon herein may be readily carried out when copper, silver, brass, iron, nickel, or any other conducting material having a different coefiicient of expansion from that of the glass or other vitreous material into whlch it is to be sealed, is used, the use of copper 1n this connection will be more particularly referred to herein.

When a copper conductor is sealed into glass, there is a tendency on cooling, for the'copper to shrink faster than the glass wall. This is due to the difierentcoefiicients of expansion possessed by these two materials. When this shrinking takes place the copper and glass may become wholly separated or the glass may become disrupted, or both. When this occurs, a direct communication between the inside of the receptacle and the outer atmosphere is established. If the conductor is made in a rib- .bon form the cracks will tend to form on the edges of the ribbon. The thicker the ribbon in comparison with its width, and the thicker the glass wall surrounding the ribbon at the seal, the easier it will berfor the cracking to take place. When a flux medium is used in sealing-in operations, rupture of the seal is prevented, because the stresses in the structure are less, probably due to the lower temperature at which the flux medium solidifies. Without the flux, however, it is apparent from experiments yield slightly when the cooling of the seal takes place and the engagement of their surfaces is not broken. When the width of the ribbon is made large in comparison with its thickness, the glass wall yields slightly and follows the shrinking. in the thickness of the ribbon; and when the edges of the b ribbon are sharpened, the glass wall is enabled to grip the ribbon with a sufiicient firmness to resist the tendency of the latter to shrink away from the glass wall at the ed s of the ribbon.

bus 3, seal may readily be made without the addition of a flux, or without exercising special care to prevent oxidation on the surface of the conductor.

In the drawings, Fig. 1 is an elevation of a portion of a container having a ribbon of contacting material sealed into the wall thereof; Fig. 2 is a view of the same structure taken at a right angle to the view of Fig. 1; andFi 3 is a cross-sectional view on a larger sca e taken on the line 3, 3 of eferring to the drawings, a conductor of copper in the form of a ribbon 4 is shown sealed at 5 into the wall of the container which is shown in the form of a tube 6 of glass. t the point where the ribbon 4 is sealed into the glass, the edges of said ribbon are sharpened as shown. This sharpening may be done in any suitable manner, as, for example, by filing ofi diagonally opposite corners on the e ges of the ribbon. lhis filing should be so done that no pronounced corner is left; that is, so that the filed surface and the original surface of the ribbon run smoothly into one another. The sharpened edges of the ribbon should be not more than .0015 of an inch thick and thinner if they can conveniently be so made.

-l*urthermore the angle at whichthe surfaces meet should be small; for example, not more than 8. It is also desirable that the ratio of the width of the ribbon to its thickness should be comparatively large; for example, ten or more.

Y If metals other than copper be used, the edge angles alone will have to be varied. Thus, for example, if iron be employed, the ed e angles should be not greater than n producing a seal according to the preferred method, the conductor is held in a la ss-workers fire having an oxidizing flame. %lie conductor is moved about in the fire until each portion of the part to be sealed in has heated to a good, red heat. This 0pil 5 ll;

rename eration will require on an overage from four to six seconds when an eight-burner fire is' used. The heat covers the copper with a thin hard coating of oxide and prevents the subsequent escape of occluded gases from the copper during thesealing-in process. The copper ribbon is then introduced into the glass and both are heated to a good, yellow heat when the glass is pressed firmly against the copper with glass-workers pliers.

-While the above has been found to be the best method of scaling in the conductor free from flux and in the are other ways in which the operation could e carried out. For example, it is not neces sary that the ribbon be completely covered with the oxide of copper before it is sealed into the glass. As a matter of fact the seal could be made satisfactorily if care were taken to prevent all oxidation. Although the present invention is herein described as particularly useful in connection with the socalled leading-in conductors, it will be understood that it is not confined to that particular use but may be employed in connection with so-called anchor wires or other structures which it is necessary to imbed in'vitreous material such as glass.

'at is claimed is:

1. The method of making a seal between a metallic conductor and a vitreous material which consists in shaping the conductor into a ribbon form, having a width-at least ten times its thickness, edge angles of not more than 8 degrees, and imbedding said ribbon in the glass without the addition of a flux thereto.

'2. The method of making a seal between glass and copper which consists-in shaping the copper into a ribbon form, havin a width at least ten times its thickness, e ge angles of not more than eight degrees, and imbedding said ribbon in the glass without the addition of a fiux thereto.

3. The method of making a seal between copper and glass, which consists in shaping the copper into a ribbon form having a width at least ten times its thicknessand edge angles of not more than eight degrees, oxidizing said ribbon and imbedding it in said glass without the addition of a flux thereto.

4 The method of making a seal between a metallic conductor and a vitreous material which consists in shaping the conductor into a ribbon form having a width at least ten times its thickness, heating the conductor un a metallic conductor and a vitreous material which consists in shaping the conductor into a ribbon form having a width at least ten times its thiclmess and edge angles of not more than eight heetin the conducribbon form, taperi it to narrow angles at tor until its surface is eove with oxide, each edge and em ding in vitreous mateand then embedding it in such vitreous murial without the addition of a flux thereto. 10 terial without the addition of a flux thereto. In witness whereof, I hereunto subscribe 5 6. The method of making a seal between a myname this 25th day of February, A. D.

metallic conductor and a vitreous material 1920. which consists in shaping the conductor into WILLIAM G. HOUSK-EEPER.

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