US1547394A - Leading-in wire for electrical incandescent lamps and similar devices - Google Patents

Description

July 28, 1925.

S. L. HOYT LEADING-IN WIRE FOR ELECTRICAL INCANDESCENT LAMPS AND SIMILAR DEVICES Filed Aug. 2. 1921 ,il liti* Patented July 28, 1925.

UNITED STATES 1,547,394 PATENT OFFICE.

SAJlIUEI.. L. HOYT, OF EAST CLEVELAND, OHIO, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

LEADING-IN WIRE FOR ELECTRICAL IN CANDESCENT LAMPS AND SIMILAR DEVICES.

Application led August 2, 1921.

To-aZZ whom. it may concern:

Be it known that I, SAMUEL L. I-IoY'r, a citizen of the United States, residing at East Cleveland, county of Cuyahoga, State of Ohio, have invented certain new and useful Improvements in Leading-in `Wires for Electrical Incandescent Lamps and Similar Devices, of which the following is a speciication.

My invention relates to leading-in wires for incandescent lamps, vacuum tubes and other electrical devices comprising sealed glac'ss containers and more particularly to composite leading-in wires, that is, leadingin wires made up of two or more different metals.

In the accompanying drawing, Fig. 1 is I a diagram of apparatus employed in carrying out the process forming part of my invention; F ig. 2 is a drawing made from a microphotograph of a section cut lengthwise along the line 2 2 of Fig. 5 of a composite wire embodying my invention; Fig. 3 is a drawing made from a similar microphotograph of a composite wire of the type now in general use; Fig. 4 is an enlarged diagrammatieal cross section of a composite wire embodying my invention, and Fig. 5 is an elevation of a piece of wire embodying my invention.

In the manufacture of the usual composite leading-inwire, a nickel-iron core at't-er proper cleaning is wound with a brass ribbon and a copper sleeve is then slipped thcreover. The composite bar so prepared is subjected to a suiiiciently high temperat-ure to cause the fusion ot the brass ribbon which fills and overflows out of the space between the core and the sleeve. The copper' sleeve is bonded to the metal core by the brass. However, the brass does not always bond the copperto the nickel-iron core at all peints but sometimes leaves a space between ihesleeve and the core. This space may not be eliminated by the rolling` swaging or :die-drawing of the composite bar. lVhen the wire containing such a space is sealed in the glass of an evacuated envelope, the space becomes a pathway for the leakage of air. In many cases, the leakage is a slow process and may not be readily detected. In fact, evacuated incandescent lamps with such imperfect leading-in wires 'may go for many days without giving evidence of poor vacuum` Serial No. 489,388.

By means of my invention, I so unite the sleeve material to the core material that the possibility of an air passage existing between the sleeve and the core is practically eliminated. By means of my invention the sleeve material is united to the core material by a material which unites, probably in solid solution, with both the sleeve and the core materials to form an allo bond. The sleeve is so rmly united to the core that, when an attempt is made to separate the two by means of a cold chisel, the core adheres to the sleeve and is cut ofi' with it without a line of cleavage appearing between the two.

More specifically, according to my invention, a copper sleeve is bonded to a core composed of iron and nickel or similar ymetal by a material which readily alloys with both copper and nickel-iron or similar alloy core to form an alloy bond. For the practice of my invention I have provided a `continuous process which produces composite wire ready to be die-drawn to any desired size preferably after a preliminary heat-treating. In carrying out this process the nickel-iron core is selected of a 7 comparatively small size so that it may be used in the form of a wire. The core is cleaned and a suitable layer of bonding material placed thereon preferably by electroplating. A suitable copper sleeve or layer of copper is then placed over the layer of bonding material preferably by electroplating. The composite wire is then reeled up and preferably stored for a short time after which it is given a preliminary heat-treatment preparatory to die-drawing it to a size suitable for use. 'My experiments seein to indicate that a better bond is obtained between the core and the sleeve when the composite wire is allowed to stand for several days before die-drawing, and I prefer to follow this practice although it is not essential and the explanation of the action is not clear. -What probably results is a partial diffusion of the bonding material into the nickel-iron core and into the copper sleeve. The preliminary heat-treatment properly anneals the composite wire for working as well as perfecting the bond between the bonding material, the .core and the sleeve.

The composite wire embodying my invention has a core composed of an alloy of iron or similar metal and a cover of copper, the percentage of nickel or similar metal in the core being greater near the copper cover than at the center of the core. While the nickel layermay be found in the composite Wire alloyed with thc copper cover and the nickel-iron core, it may be made so thin in the process that it completely alloys with the copper cover and the nickeliron core and loses its identity.

Referring to the drawing, the nickel-iron core wire 10 is contained on a reel 11 from which it is gradually fed to a cleaning means 12 in which it is passed between pads 13 which are saturated with a' cleaning agent, such as carbon tetrachloride, contained in the reservoir 14. It is then fed through the usual electric annealing furnace 15 in which it is electrically heated in an atmosphere of hydrogen entering the furnace through the pipe 16. In addition to annealing the Wire 107 the treatment in the furnace reduces any oxides which may be present, From the furnace 15, the wire 10 is fed to a plating tank 17 in which a layer of nickel is electrolytically deposited thereon. The plating bath 18 contained in the tank 17 consists of a nickel-ammonium sulphate solution although any suitable nickel-plating solution may be used. A source of direct-current electrical energy such as the generator 19' has the positive terminal thereof connected to a pure nickel anode 20 which is suitably supported in the plating bath 18. The negative terminal of the generator 19 is connected to a brush 21 which contacts with the moving wire 10. A rheostat 22 or other proper regulating means is inserted in the electrical circuit to control the rate of plating which also depends upon the rate of feed of the wire 10, upon the strength of the plating bath 18 l and upon the amount of wire 10 exposed to the plating bath 18. An ammeter 23 is inserted in the circuit to indicate the value of the current used.

From the tank 17 the wire 10 passes over the drum .24 where a spray of-water from the jet 25 washes off any solution carried off from the bath 18. It is then fed over a drum 25 in plating tank 26 in which a layer of copper is electrolytically deposited on the layer of nickel. A copper cyanide solution is preferably used as the plating bath 27 although any suitable copper-plating solution may be used. The positive terminal of a source of direct current energy such as the generator 28 is connected to a series of pure copper anodes 29^which are suitably supported in the plating bath 27. The negative terminal of the generator 28 is connected to a brush'30 which contacts with the metal drum 31 which engages the wire 10. A proper regulating means such as a rheostat 32 is inserted in the electrical circuit so as to control the rate of plating which also depends upon the rate of feed of tl1e\wire 10 and upon the strength of the plating bath 27 as well as upon the amount of wire 10 exposed to the plating bath. An ammeter 33 is inserted in the circuit to indicate the value of the current used.

From the plating bath 27 the wire 10 is wound upon a reel 34. It now consists of a nickel-iron core 35 which carriesa layer of nickel 36 and a layer of copper 37 (see Fig. 4). Each reel of wire is preferably stored for from one to two weeks. It is my belief that when the wire is allowed to stand a diffusion occurs of the nickel layer 36 into the nickel-iron core 35 and the copper layer 37 and I have found that a better bond seems to exist between the copper layer 37 and the nickel-iron core 35 after standing than before. The composite wire is then preferably heated and subjected to the usual die-drawing operations.

A specific example of my invention is as follows: The nickel-iron wire 10, is selected of about 70 mils diameter and passes through the cleaning pads 13. The cleaned wire then passes to the plating bath 18, which consists of a 7 per cent (grams per cubic centimeter) solution of nickel ammonium sulphate, at the rate of 5.5 inches a minute approximately 6 feet of the wire 10 being exposed to the plating bath 18. The current flowing in the electrical circuit supplied by the generator 19 is about 0.35 ampere at a pressure of 2 volts between the cathode and anode. The layer of nickel deposited is approximately one-fifth mil in thickness making the diameter of the Wire -10 about 70% mils. The plating bath 27 consists of a 6.75 per centsolution of copper cyanide and has exposed therein about 200 feet of the nickel-plated wire 10 which is fed through the bath at the rate of 5.5 inches a minute. The generator 28 supplies a current of about 25 amperes at a pressure of 2.5 volts between cathode and anode. The layer 37 of copper which is deposited upon the nickel-plated wire 10 is approximately 5 mils in thickness making the total diameter of the composite wire 10 equal about 80 mils. After storing, preferably for about ten days, the composite wire is subjected to a preliminary heat-treating.

The preliminary heat-treating consists first of a low temperature anneal and in my specific process I preferably subject the wire to a temperature of about 350 for ten minutes. Then I subject the wire which is approximately 80 mils in diameter to a cold drawing operation and, in two passes through suitable dies, the diameter is reduced to about 70 mils. The wire is now preferably heated to about 800 C. and subjected to a hot swaging operation which reduces the diameter from about 70 mils to about 50 mils in four passes through a suitable swaging machine. This heat-treating relieves the strains which may exist in the composite Wire, toughens the copper and assists in alloying the layer of nickel with the nickel-iron core and the copper coating. The composite wire is now ready to be subjected to the usualV die-drawing process until the dia-meter is that 'desired for use.

Some of the properties of one lot of composite wire embodying my invention are as follows:

Resistance of 100 centimeters of 8 mil Wire at 0 C. is between 2.60 and 3.75 ohms;

The temperature co-,eiicient of resistance is between 0.00278 and 0.00374;

The linear co-eicient of expansion is between 7.0 X 10e and 8.7 X 10-8;

The specic gravity is between 8.11 and 8.32;

The tensile strength is between 72,000 and 80,600 pounds per square inch.

Figs. 2 and 3 are taken from micro-photographs, the circular shapes thereof being delined by the borders of the microscopic field. The sections from which these microphotographs were made were taken longitudinally of the wires, Fig. 2 being taken from a wire made according to the present invention, and Fig. 3 from a wire of the type which is now in general use. It will be observed that in Fig. 2 there is practically no line of demarcation between the light colored zone at the left and the dark colored zone at the right, while in Fig. 3 the demarcation is quite distinct. As stated above, this difference arises from the fact that an alloy bond is actually formed in the case of the present invention.

As stated above, I have utilized nickel as the bonding metal but it is to be understood that metals other than nickel which are known in the arts to have similar properties are to be considered as coming within the scope of my invention. While I have used the term nickel in the claims as referring to the bonding material it is t0 be understood that this is to be interpreted to include these metals having similar properties to nickel as Well as nickel.

lNhat I claim as new and desire to secure by Letters Patent of the United States, is,-

1. A composite low expansion leading-in `wire comprising a core composed of an alloy of iron and nickel, and a cover of, copper, the percentage of nickel in said core being greater near the copper cover than at the center of the core.

2. A composite low expansion leading-in wire comprising a. core of nickel-iron and a cover of copper, the percentage of nickel in said nickel-iron core being greater near the copper cover than at the center of the core.

3. A composite 10W expansion leading-in wire comprising a center zone having a high percentage of iron, an intermediate zone iaving a high percentage of nickel and an outer zone having a high percentage of copper. i

4. A composite low expansion leading-in wire comprising a core or' nickel-iron and a cover of copper united thereto by a nickel alloy bond.

5. A composite low expansion leading-in Wire comprising a core composed of an; alloy of iron and nickel, an intermediate zone high in nickel and a cover of copper.

6. A composite low expansion leading-in wire comprising a core of nickel-iron, an

intermediate zone high in nickel and a cover or' copper.

7. The process of producing a composite low expansion leading-in wire which consist-s in electrolytically depositing a layer of nickel upon a core of nickel-iron` then electrolytically depositing a layer of copper upon the nickel-plated nickel-iron core and then causing at least a part of said nickel to alloy with said nickel-iron core and said copper cover.

8. The process of producing a composite low expansion leading-in Wire which consists in feeding a nickel-iron core Wire to a nickel-plating bath, electroplating a layer of nickel upon said core wire while in said nickel-plating bath, passing said nickelplated nickel-iron Wire to a copper plating bath, electroplating a layer of copper upon said layer of nickel while in said copperplating bath, annealing the composite wire so formed and then Working it mechanically to cause at least a part of. said nickel layer to allo with said nickel-iron core and said la er o copper.

9. Tie process of producing a composite low expansion leading-in wire which consists in assembling an intermediate layer of nickel between a core metal ot nickel-iron and a cover metal of copper and thon causing at least a part of said intermediate layer of nickel to alloy with said nickel-iron core and said copper cover.

In witness whereof I have hereunto set my hand this 28th day of July, 1921.

SAMUEL L. HOYT.

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