US1756314A - Conductor - Google Patents

Description

April 29, 1930. w. B. TEN EYCK CONDUCTOR Filed March 25, 1925 loading Tape.

Inf/enfer:

Patented Apr. 29, 1930 UNITED STATES PATENT OFFICE WILLIAM-BETTEN EYCK, DECEASED, LATE F IVIONTCLAIR, NEW JERSEY, BY CHRISTINE Z. TEN EYCK, ADMINISTRATRIX,

OF 4MONTCLAIRy NEW JERSEY, ASSIGNOR, BY

MESNE ASSIGNMENTS, TO WESTERN ELECTRIC COMPANY, INCORPORATED, Al COR- PORATION 0F NEW YORK.

CONDUCTOR Application led March 25, 1925. Serial No. 18,334.

This invention relates to conductors for the transmission of electrical energy and more particularly to signaling conductors having an external layer of a material of high permeability for the purpose of increasing the inductance of the conductor. l l

011e manner ofincreasing the inductance of the conductoremployed for the transmission of alternating current is to wrap the conv has been considered to be the only material ductor spirally with a in the art as continuous inductive loading as distinguished from lump loading by means of inductance coils distributed at intervals along the conductor. Until recently iron suitable for continuous loading but it has now been discovered that a more suitable material may be procured in the form of an alloy of nickel and iron. When these two metals ,are combined in the proper proportions and the resulting alloy is given a proper heat treatment, a material having a very high permeability at low magnetizing forces is obtained.

One form of this material which has been used in a submarine cable comprises 7812% nickel and 2l1/2% iron. Alloys of nickel and iron having similar characteristics .especially high permeability at low madnetizing forces have been styled permalloy. Other properties possessed by these alloys which increase their value as a loading material are a hysteresis loss lower than that of iron and a high resistivity, both properties being conducive to ering the effective resistance of the conductor.

' When it was attempted to employ this material in the form of a tape for continuous loading, difficult-ies were encountered. It was found that if the permalloy tape was rst heated and then cooled before applying to the conductor7 internal stresses were set up upon bending of the tape, causing the permeability to be very. materially lowered. This difficulty was overcome by applying the tape to the conductor before giving the tape the heat treatment and then subjecting the taped conductor to the heating and cooling necessary to produce high permeability in the loading material.

layer of wire or tape of magnetic material. This method is known( t meability.

Further difficulty, however, was experienced in that the permeability of the loading material was lowered by what apeared to be adhesion between the copper conductor and the loading tape. It is believed that this adhesion occurs when the taped conductor is subjectedto the -high temperatures necessary for the proper heat treatment and that upon subsequent cooling the tape is subjected to stresses which cause a lowering of its per- 'In the construction of a loaded conductor it vwas the practice to wrap a layer or magnetic material comprising a nickel-iron alloy `closely around the conductor consisting of a central copper wire surrounded by six flat copper strands, the whole making a compact structure with very little space not occupied by metal. To give the loading material the desired magnetic characteristics, this conductor was heated to approximately 850 C. and then cooled at a preferred rate. A On heating,

vboth metals expand but the copper, because of its higher temperature coefficient, expands more than the loading material with the result that it presses tightly against the loading material whenthc conductor is at the high temperature and if the structure is a fairly tight one, the magnetic tape is stretched,y an elongation of 1% having been observed. This stretching has apparently no direct effect on the magnetic properties since it occurs at a temperature above the magnetic transformation point but it does show effects of high ressure between the metals. At the temperature of 850 C. both metals are relatively soft and since they are forced together by thermal expansion there is a/ tendency for the loading material to weld to the copper, the extent to which the metals are welded de pending on severalfactors such as the tightness of the copper structure and the character of the metal surfaces. In this connection it has been noted that although the loading material welds to the copper, welding of the copper strands to the central wire has been very rarely observed and no welding has been magnetic tape is at points `pulled down with the copper and parts of it are bent, stretched or compressed depending upon the part-icular accidental conditions of adherence.

small, the stresses at points in the tape may be of considerable magnitude giving strain sufiicient to reduce the permeability at spots to a very small fraction of that which the tape would'have had if not subjected to such strain. The resultant conductor, therefore, isL one which although it may have fairly uniform inductance as measured from footfto foot is loaded with a material which varies in permeability over a wide range in points separated by a fraction of an inch. The copper strands upon being stranded about the central conductor do not present a true cylindrical surface since the edges of the strands do not lie in close contact with the central conductor but present spiralled edges. As the cooling proceeds, therefore, a sticking or welding of the material may occur at'yarious points along these edges and the subsequent contraction of the copper set up stresses in the alloy tape.

During the cooling portion of the heat: treatment the alloy tape may cool more rapida' 1y at first than does the copper conductor duev to its intimate contact with the cooling medium so that the alloy tape quickly comes into intimatecontact with the copper strands.

' Whatever may be the true explanation forl the difficulty experienced, it has largely been' overcome by providing a small air space between the layer of loading material and the signaling conductor when the loading material is applied. This method of obtaining high permeability is described at length in patent to G. W. Elmen No. 1,586,887, granted on June 1, 1926. i

- Instead of providing an air space between the conductor and the tape, as the latter` is wound in position, the desired result may be obtained by placing'a layer of paper upon the conductor before the loading material is wound thereon. This layer of paper is burned out during the subsequent heat treatment thus giving the desired spacing between. the loading material and the conductor. This method is described in-detail in patent to W. B. Ten Eyck No. 1,586,862, granted on June 1, 1926.

During the heat treatment the loaded conductor is passed through a. heatedl tubel for the purpose of securing the desired permeability of the loading ta e. It has been foundthat if any grease, o1 or carbonaceous material Even. through the forces involved may be very.`

is, by accident or otherwise, attached to the heating chamber or the conductor as it passes through the heating. chamber reducinggases such as hydrogen or carbon monoxide are released. All copper wire of high conductivity 70 which it is possible to obtain on the open market contains a certain amount of'copper oxide, and when the copper conductor is heated in the presence of a reducing atmosf phere, the copper oxide is dissolved, thereby Y rendering the` conductor brittle. Various means have been proposed for preventing this embrittling action, such for example, as the method disclosed in patent to J. W. Harris,

No. 1,586,897, granted on June 1, 1926. In

.this method, which has been the preferredf' methed used commercially heretofore, a stream of nitrogen isforced through the heatf ing tube in a direction opposite to the direction of movement of the conductor, thereby sweeping out the reducing gases as soon as they are released and thus protecting the con ductor: This process, however,is expensive, and moreover, is objectionable because of the fact that there is always an element of risk linvolved since failure of the flow of nitrogen might be of serious consequence.

An obj ect of the present invention is t9 provide for the practical loading of a signaling lconductor with magnetic material which recontemplates an electrical conductor upon 11owhichis applied a loading material capable of possessing high permeability, and the method of ap lying this material to the con-y ductor in suc a way as to avoid obtaining low or variable values of permeability. This invention is in the nature of an alternative to those disclosed in the above mentioned patents to G. W. Elmen and W. B. Ten Eyck and-also the copending application of O. E. Buckley, Serial No. 758,984, filed December azz; 31, 1924. Each of these inventionshas certain advantages over the others as will be apparent froma consideration of the several patents. v j v y The invention may be more clearly under- 12; stood by reference to the accompanying drawing inwhich: Y y y Fig. 1 is a view of a loaded conductor, certain portions being shown cut away to more clearly disclose the structure; and 'v .130

vpreciably Fig. 2 is a view showing a simplified type of apparatus which may be used for applying the heat treatment to the conductor. l

Referring to the drawing, the y electrical conductor preferably" consists of a 'central core member 10 of conductive material about which a plurality of conducting strands 11, 11 are wrapped with a spiral lay in such manner as to provide a smooth exterior surface. About this composite conductor is wrapped the tape 12 which preferably consistsof an alloy containing 7 81/2% nickel and 2112% iron. The inner surface 13 of the tape 12 is pro-4 vided with a layer of metallic oxide 13 which serves as a spacer between the copper strands 11, 11 and the magnetic tape 12. This layer Of metallic oxide is so thin as not to alter aptape and may be formed by heating the tape to a temperature slightly below the annealing temperature. In practice this has been accomplished by heating pads of tape to a temperature of 500 to 600o C., maintaining them at this temperature for a period of approximately ten minutes and then permitting the tape t0 cool to room temperature while exposed to the atmosphere.

After the stranded conductor is formed of the composite copper conductor about which is wrapped the oxidized metallic tape, the resulting conductor is treated by passing it through a heated tubular furnace of the general type disclosed in Fig. 2. This furnace, which is of the muiiie type, comprises heating elements 30 which are located Vbef a heat treatment to develop high permability -in-'its loading comprising a conducting core,

tween the re clay muifle 31 and the fire brick 32. The iron tube 33 has a copper lining 34 of such small inside diameter as to prevent rapid circulation of air which might cause an objectionable degree 0f oxidation of the nickel-iron alloy tapeI when subjected to the high temperature required'during the heat treatment of the material.

For the sake of clearness, this apparatus has been shown schematically but'reference is also made to an application of F. S. Kochendorfer, Serial No. 601,021,1filed November 15, 1922, which has issued as Patent No. 1,624,668, on April 12, 1927 and which discloses the preferred type of apparatus to be used.

Vhen a structure constructed as described, dangerof embrittling the conductor during the heat treatment is eliminated, even though oil, grease or other carbonaceous material is attached to the conductor as it enters the furnace and even though this foreign matter produces reducing gases, since these gases will first 'attack the metallic oxide on the surface of the tape and if this oxide .is sufficient in amount, very little action will take place tending to embrittle the conductor.

The coating of metallic oxide on the surface of the magnetic tape furthermore prevents the copper conductor from welding to the lmagnetic tape when the taped conductor the cross section of the magnetic;

is subjected to the high temperature required for the heat treatment. Therefore, adhesion between the conductor and tape during thev plied to a solid conductor. In the case of a loaded stranded conductor there is a certain amount of looseness in the structure which prevents adhesion and which is not present when the loading tape is wound upon a solid conductor. Therefore, in the latter case there is an even greater necessity for providing some means for preventing adhesion.

What is claimed is: 1.- A loaded signaling conductor requiring a heat treatment to high temperatures comrising a conducting core, a magneticloadlng material wrapped closely about the core, and a coating of reducible material on said loading material separating the loading material from the conducting core. 2. A loaded signaling conductor requiring a heat treatment to develop a magnetic property thereof comprising aconducting core, a magnetic loading material wrapped closely about the core, and a coatin of metallic oxide on 'said loading4 materia separating the loading material from the conducting core.l 3. A loaded signaling conductor requiring a magnetic loading material wrapped closely about the core, the permeability of which is sensitive to strain, and a coating of nickel oxide and iron oxide on said loading material separating .the loading material from the conducting core.

4. A loaded signaling conductor comprising a conducting core, a layer of oxidized loading material Wrapped closely about the core, said loading material comprising a nickel-iron alloy in which the nickel component predominates, said loaded conductor requiring a heat treatment to develop one of its characteristics.

5. A loaded signaling conductor requiring a heat treatment to develop high permeability in its loading comprising a conductin core, a layer of oxidized loading materia wrapped closely about the core, said loading material comprising a nickel-iron alloy which consists of approximately 7 81/2% nickel and 211/2% iron.

6. The method of constructing a continuously loaded signaling conductor which comprises forming a layer of metallic oxide on a magnetic tape, wrapping said magnetic tape about a conducting core, and heat treating the loaded conductor.

is of particular lmportance 1n preventing adhesion when ap- `7. The method of constructing a continuously loaded signaling conductor which comprises oxidizing a nickel-iron alloy tape, wrapping said tape about a conducting core,

and heat treating the wrapped core to develo hi ermeabilit 8.pTheg1nshod of coiistructing a continuously loaded copper conductor which comprises subjecting the loading material to a temperature' of from 500 to 600o C. for 4a period of approximately ten minutes, allowing the material to cool slowly while exposed to the atmosphere, windin the tape about a y copper conductor, and subjecting the loaded conductor to heat treatment which develops high permeability.

In witness whereof, the said Christine Z. Ten Eyck, administratrix, hereunto subscribes her name this 16th day of March, A. D. 1925.

CHRISTINE Z. TEN EYCK, Admi//zfistmtm of the Estate of B.

Teva Eyck, Deceased.

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