US2051423A - Insulated conductor - Google Patents

Description

Aug. 18, 1936. A E, SCHACHT 2,051,423

-INSULATED CONDUCTOR Filed May 5, 1932 M455 alf-Ens r/c Fier/CLES #N0 P75255 N455 oFfmsr/c Patented Aug. i8, 1936 parent austin FFEQE INSULATED CONDUCTOR Elmer C. Schacht, Troy, N. Y., assigner to Behr- Manning Corporation, Troy, N. Y., a corporation of Massachusetts Application May 5, 1932, Serial No. 609,526

6 Claims.

The present invention is an`insu1ated conductor.- Broadly considered, the invention is an article of manufacture comprising an electric conducting core having a composition consisting of 5Y particles of a resilient or elastic nature interlaced with bres applied thereto.

An object of the invention is to provide an insulated conductor which will have greatly improved electrical and 'other favorable qualities and the insulated coating of which will possess, to the optimum degree, the qualities of flexibility and low apparent density.

vI'am aware that insulated conductors formed of wire, cable, or other electrical conducting materials wrapped or coated with various types of ber compositions are well known. However, none of these prior art conductors are formed in such a manner as to provide small air spaces or voids within the body of the insulating preparation with which the electrical conductor is coated or wrapped. My 'invention contemplates the provision of such air spaces or voids, and the electrical qualities of my conductor over the prior art conductors will be greatly increased by-reas'on of the existence of these air spaces or voids.

The term conducting core as used in the present specification and claims refers to a solid or hollow core of any configuration or to a core of numerous strands twisted together and having any desired exterior configuration.

The terms coated or coating, as used in the specification and claims include Wrapping or any other manner of applying the materials used in my invention to a conducting core.

In the drawing:

Figure 1 is an elevation of an insulatedconductor made in accordance with my invention;

Figure 2 is a diagrammatic View, partly in cross-section, showing the insulated conductor of Figure 1; 4'

Figure 3 is an elevational showing of a modified form of my invention;

Figure 4 is an enlarged cross-section of a multi-cable conductor formed in accordance with my present invention;

Figure 5 is a greatly enlarged fragmentary cross-sectional showing of the conductor shown in Figure 4; and

Figure 6 is a diagrammatic view, partly in cross-section, showing another modification of my invention. f

Referring to Figures 1 and 2 of the drawing, the numeral I0 designates an electrical conducting core such as a copper cable or strip provided with a coating II formed of bres I2 and particles I3 of cork or other suitable resilient or elastic material. In manufacturing this embodiment of my invention, fibres I2 and particles I3 are preferably mixed into a pulp, which can be done by means of an ordinary paper making 5 beater, and the pulp mixture, suiciently suspended in or diluted with Water, is coated directly around the conductor and is afterwards formed and dried into a cover or sheathl consisting of intermixed cork particles and fibre 10 without being rst formed into an ordinary sheet or web of paper.

In the formof my invention shown in Figure 3, the conducting core I0 is coated with strips I4 of sheet material also formed of bres I2 and l5 particles I3 of a nature similar to those described in connection ywith Figures 1 and 2. The material with which the conducting core I0 is coated in this instance is originally formed from the bre and cork pulp'mixture into a continu- 20 ous sheet on a cylinder or Fourdrinier type of paper making machine and the completed web or sheet is then slit into narrow rolls or strips which are wound or wrapped upon the core I0 according to the methods now followed in insu- 25 lating conductors with paper.

As will be apparent from the followingv specication, air spaces or voids will exist within the insulating materials II and I4 and these air spaces are designated by the numeral I5 ap- 30 plied to the enlarged view shown in Figure 2.

'Ihe bres I2 may be of various materials, among which are jute, rope, hemp, sisal, kraft pulp bres, cotton, linen, long wood pulp or alpha-cellulose wood pulp. The particles I3 are 35 preferably cork particles of various sizes -or granulated cork, but it will be understood that shredded or ground particles of resilient or elastic materials other than cork may be used, for example, dried and screened sugar cane pith, 40 chopped coarse sugar cane fibres, or ground and screened chipped fragments of wood. Wood particles such as result from turpentine extraction may also be used. However, the use of cork particles in the coating materials used with my insulated conductor gives by far the most satisfactory results because of the high insulating value of cork and its light weight and resiliency. Another attribute of cork which makes it particularly desirable for present purposes is the v fact that it cannot be impregnated. If the materials II and I4 are saturated with oil or the like in the manner hereinafter described, the saturant cannot work into the particles of cork to change their internal structure, but will merely coat them. rlhe resultis that after the saturating treatment, the particles of cork will still retain their inherent and highly valuable qualities of light weight, resiliency and high insulating value. Cork is therefore preferable to materials which absorb a saturant.

I nd that a very satisfactory insulated conductor may be'formed from a mixture comprising 20% of the particles I3 and 80% iibre by weight. I-Ioweve, the materials II and Il may be varied through different ranges at least up to of .the particles to 30% of the fibre, by weight. The particles I 3 used in the materials may range in. size from 30 to 150 mesh, or liner, or the range used in a particular batch of the materials may be limited to some range such as between 30 and 80 mesh.

Generally speaking, the materials II and Ill are strengthened by having a larger proportion of the fibres present, but the electrical characteristics and exibility are enhanced by increasing the proportion of the particles I3. The particles I3 act as separators or spacers for the fibres within the sheet II, thereby producing the'air cells or voids I5. I find that the size and number of the air spaces I5 varies in accordance with the size and number of the particles I3, because of the fact that air spaces or voids I5 apparently form adjacent the particles I3 or because the intermixture or interlacing of the particles I3 at various angles necessarily produces voids within the material and exteriorly of the particles and bres. The natural result is that larger particles I3 cause the presence of larger air spaces or voids. On the other hand, if particles within the smaller size ranges indicated are used, smaller air spaces or voids will occur, but the number of the latter may, of course, be increased by an increase in the number of particles I3. With thisA in mind, the material II may be formed with the particles of the size and in the proportion with respect to the fibres which is best suited to the particular electrical purpose for which the conductor is to f be used. However, the particles I3 should have a diameter' at least equal to the cross-section of the bres I2, but should be of somewhat less diameter than the thickness of the coating II` or I4 applied to the conducting core It, although if the coating is to have a rough 'exterior finish, larger particles I3 may be used.

In the formation of the materials II and I, the fibres I2 become so thoroughly interlaced with each other and with the particles I3 that the materials are extremely fiexible. This flexbility is apparently due to the fact that the fibres hinge or pivot upon the particles I3 as well as because the existence of the4 airspaces or voids I5 permits the fibres to distribute themselves under iiexure. without breaking up the general structure or surface of the material. The flexibility of the material naturally increases the exibility of my insulated conductor, and I am thereby enabled to produce an insulated conductor which may be, sharply "bent Without danger of cracks occurring in the insulation. It may. be noted too that the probability of cracks or tears developing in the coating I4 during the wrapping operation is reduced to a minimum because oi its iiexibility and resiliency.

When the insulated conductor of this invern-- aosrgiaa tors wound together into a larger cable as shown in Figure 4 and an additional coating 2l (Figure 4) may then be applied to the Wound conductors.

The coating 2l will usually consist of a number of wrapped layers of heavier and coarser insulating material composed of cork and fibre. The most satisfactory way of saturating such a high voltage transmission cable is to place the cable in a vacuum tank where it is subjected to a high enough temperature to remove moisture and wherel it is further subjected to a fairly high vacuum to remove moisture, vapor and air contained in the insulated coating. The hot insulating compound heated to a high degree of fluidity is run into the vacuum tank so as to completely cover the evacuated and heated cable. The entire system is then allowed to cool so as to further increase the absorption of insulating material into the insulation. A protective cover or sheath 22 usually of lead may be applied directly over the saturated coatings. The vacuum treatment of the cable will remove any air which might be present in the spaces I5 and will thereby effect a more thorough impregnation. The presencerof the voids I5 in the material will cause the saturant to almost completely penetrate the material with the result that my conductor will be much more thoroughly impregnated than are the usual conductors of such types. The highly dielectric oil in combination with the fibre greatly improves the dielectric properties of the material.

Due either to the peculiar physical characteristics of the materials II and I4 or to the improved saturation which is obtained by the use of these materials, or from both causes combined, the finished-conductor has very desirable electrical characteristics, such as low power factor loss, resistance to high voltage breakdown and resistance to current leakage under high tension. 'I'he improvement in these electrical qualities minimizes the possibility of damage to the conductor through electrical failure and also .adds to the commercial eiciency of the coneiect. Ipreferably use the form of conductor illustrated in Figure 3 for communication purposes, applying a single wrapping I4 to each of -the conducting cores I0.

y A large number of these "conductors are then twisted together and the whole structure finally covered by an outside protecting layer similar to layer 2l of Figure '4. This outer layer may be formed of a spirally Wrapped strip of somewhat heavier-and thicker material than the coating about the individual cables. The usual lead sheathing may be applied to the outer wrapping. The electrical charac- 75 teristics of the individual conductors of this.

l ductors l results in small air spaces 23 between the contacting wrapped surfaces of the individual conductors Ill shown in Figure 5 and these further increase the electrical qualities of the conductors. For some purposes, it may be prac- .tical to deposit the outer coating 2l of cork and fibres in the manner described in`connection with Figure 1.

In some instances it may be desirable to construct insulated conductors of my invention for use in communication .purposes according to the method described in connection with Figure 1. If the individual conductors constructed in this manner are to be used in a cable, they would be twisted and formed into a multi-cable structure generally similar to that illustrated in Figures 4 and 5.

Figure 6 shows an electric conducting core Il) which is coated With a sheet of paper comprising two or more plies, one or more adjacent plies being formed of a mixture I6 of cork and fiber, While a ply I1 on one surface of the material is formed of fibre alone. .As is shown in Figure 6, this material is applied to the conducting core I0 in such a manner that the cork and fibre mixture ply or plies I6 will be in contact with the conducting core I0, positioning the fibre ply l1 on the exterior of the insulated conductor structure. This arrangement is very effective when the insulated conductor is to be used in situations' where the high coefficient of friction of the cork might be a disadvantage. It may be desirable for some purposes to position the fibre ply or plies I1 adjacent the conducting core I0 and to have the cork and fibre ply I6 form the exterior surface of the insulated conductor structure. tageous to use a coating sheet which is formed with fibre plies on both its surfaces, a ply or plies.

of the cork and bre mixture being formed centrally of the coating, so that the fibre will be in contact with the conducting core l 0 and will also form the outer surface of the insulated conductor structure.

It is obvious that the materials used in coating my insulated conductor are extremely light in Weight, and I am thereby enabled to produce a conductor which has le'ss Weight than any insulated conductor of a corresponding eiciency now in use.

ItY may be pointed out that the function of the resilient or elastic particles used in my invention is entirely different from the particles of clay, talc and other exceedingly fine particles which are generally added to various types of papers. These latter particles are generally added to increase the density of the nished product or close the surface and, of course, decrease the air For still other purposes, it may be advanspaces. In my product, as stated above, the particles coact with the fibres to provide air spaces or increase the saturation.

-I claim:

1. An varticle of manufacture comprising a multi-strand insulated cable for low voltage, the individual strands bein'g coated with a mass of resilient and elastic particles and bres, the particles and fibres being interlaced to form a cellular structure and to provide a rough exterior finish on the individual strands, so that the assembly of the individual strands forms air `cells between the individual strands Within the multi-strand cable.

2. An article of manufacture comprising a multi-strand insulated cable for low voltage, the individual strands being coated with a mass of resilent and elastic particles and libres, the particles and fibres being interlaced to form a cellular structure and to provide a rough exterior finish'on the individual strands, so that the assembly of the individual strands forms air cells between the individual strands Within the multi-strand cable, and `the assembled strands being coated with a mass of, interlaced particles and fibres.

3. An article of manufacture comprising a low voltage insulated conductor consisting of a conductor core having directly applied thereto a coating formed of an intermingled mass of fibres and cellular particles, the cellular particles being supported in such a manner in the mass as to provide air cells within the mass and exteriorly of the particles and bres so that electrical capacity'effects will be reduced.

4. An article of manufacture comprising a low voltage insulated conductor consisting of a coriductor core having directly applied thereto a coating formed of an intermingled mass of bres and cork particles, the cork particles being supported in such a manner in the mass as toprovide air cells within the mass and exteriorly of the particles and fibres so that electrical capacity effects will be reduced.

5. An article of manufacture comprising a low voltage insulated conductor consisting of a conductor core having directly tpplied thereto a coating consisting of bres and a mass of cellu- 'lar particlesin interlaced relation, said particles having av diameter atleast as great as the diameter of said bres to form air cells within the! of said particles to form air cells Within the mass ELMER C. sCHAcH'r;`

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