US1905789A - Insulated electrical conductor - Google Patents

Description

April 25, 1933. A. A. BENNER El AL INSULATED ELECTRICAL CONDUCTOR Filed July 30, 1927 Patented Apr. 25, 1933 UNITED STATES PATENT OFFICE ANTHONY A. BENNER AND RUDOLPH A. SCHA'IZEL, OF ROME, NEW YORK, ASSIGNOBS 1'0 GENERAL CABLE CORPORATION, OF NEW YORK, N. Y., A CORPORATION OF NEW JERSEY INSULATED ELECTRICAL CONDUCTOR Application filed July 30,

This invention relates to improvements in insulated electrical conductors of the type shown in Letters Patent N 0. 1,520,680, granted December 23, 1924, upon the application of Charles W. Abbott.

It is an object of this invention to improve the construction shown in the aforesaid patent in a manner which will permit the same to be manufactured more rapidly and economically; and also to improve the construction by the inclusion of means to prevent the compounds which are applied to the outer surface of the cable from penetrating to the interior thereof.

Other objects and advantages of the invention will appear hereinafter.

A preferred embodiment of the invention selected for purposes of illustration is shown in the accompanying drawing, in which,

Figure 1 is a plan view of a short section of a two conductor cable having the several sheaths of material progressively removed to show the interior construction.

Figure 2 is a section on the line 22 of Figure 1, and

Figure 3 is a plan View, similar to Figure 1,

I showing a modified form of the invention.

y The structure shown in the drawing is built up upon metallic conductors 1 which are covered with the usual rubber insulating compound 2, applied to the conductors and vulcanized in place by usual known methods. This compound provides substantial electrical protection for the conductors, but inasmuch as the compound without further protection is readily susceptible to mechanical injury and aging effects, it is necessary to further protect and insulate the conductors if they are to be formed into a cable and safely used in the distribution of electrical energy. In the specific construction shown in the above mentioned patent this further mechanical and electrical protection is provided by two sheaths of protective material in strip form applied by a wrapping operation and held in place by overlying braids. According to the present invention the first sheath is held in place by means differing specifically from the first overlying braid shown in the patent and the present construc- 1 insulation.

1927. Serial No. 209,505.

a strip of relatively thin kraft paper repeata edly folded upon itself until a tape of desired thickness is built up. Herein the strip is foded three times to form a tape of four layers.

Crossing the stripsof protective material 3 as they lie upon the insulating compound 2 are a plurality of binding threads of cotton,

identified by the numeral 4 with exponents 1 tr? 4 inclusive. Herein these threads are evenly spaced and with the strips form a one and one braid. In fact, the strips and threads may be conveniently applied by an ordinary high speed braiding machine. Thus the described construction makes it possible to apply an insulating and protecting sheath over the rubber compound and simultaneously bind the same in place with interbraided threads 4.

In applying this protective sheath to the rubber compound the paper is preferably humidified slightly, prior to the braiding operation and the tensions on the paper strips and cotton threads are so adjusted that the sheath will be formed rather tightly upon the rubber The speed of the material through the braiding machine is so related to the speed of the bobbins that the edges of the strips will closelyabut each other. Various.

Width strips may be used, but preferably the width of the strip relative to the diameter of the rubber sheath is such that the strips will lie at an angle of approximately 45 to the length of the conductor, the thread:- crossing the strips at right angles and being spaced from each other by approximately the width of the strips.

The structure just described may be treated with a compound which will render the protective covering moisture resistant or fire resistant or both.- Preferably a compound primarily moisture resistant is applied. As will be later explained, the sheath formed by the strip 3 and threads 4 is the outer or exposed covering of the conductor inside so-called outlet boxes used in electrical installation and the character of the covering is such that it is particularly suited to meet all the conditions found therein.

The mechanical and electrical protection of the conductors may be further increased by a second protective sheath, preferably formed as shown in the drawing, and consistin of a relatively stifi'er, thicker wrapping of fi rous material such as a heavier kraft paper repeatedly folded upon itself to form a strip 7. This strip has five folds and six layers and is of a finished width approximating the diameter of the underlying insulated and protected conductor. This strip may be applied as a single wrap spiraling around the conductor with normal lay that is, with its edges closely abutting in the form of a closed helix. Preferably this strip is also humidified before application so that as it dries out the slight shrinkage will cause it to tightly engage the underlying material. This sheath, being thicker and stiffer than the first sheath affords the greater part of the mechanical protection of the insulated conductor outside outlet boxes.

Two or more conductors thus prepared may be assembled and the assembled conductors may then be covered with a layer of protective material. As illustrated in Figure 1, the said protective layer may comprise a single wrapping 10 of relatively thin and impervious paper applied spirally about the two conductors in such manner that adjacent edges overlap slightly, or, as illustrated in Figure 3, the covering may comprise a sheath 10 of crimped or crepe paper applied longitudinally, said paper being of a width sufficient to permit its edges to be overlapped.

In the form shown in Figure 1 the successive laps of the spiral wrapping slide one upon another when the cable is bent, while in the form shown in Figure 3, the crimping of the paper provides sufiicient give as the cable is bent so that the paper does not break or interfere with the flexibility thereof.

Thereafter, the conductors and the protective covering may be surrounded with a stron outer braid 11, preferably of fabric, and t e completely assembled cable may then be subjected to further treatment with compounds designed to render the whole structure slow burning and substantially moisture proof. Such a compound may comprise approximately 250 parts of hard stearine pitch, 100 parts of soft stearine pitch and 25 parts of parafiin applied at a temperature of approximately 400 F.

It is desirable that such compound pene-' trate thoroughly the interstices of the outer braid in order to perform properly its intended functions, but it is not desirable that it penetrate to the conductors or their wrappings. As will be observed, by interposing a protective layer between the braided jacket and the wrapped conductors, penetration through the jacket is permitted, but the inside wrappings remain substantiall clean. Furthermore, due to the fact that t e compounds are prevented from penetrating to the interior of the cable, the coating and impregnation of the strands of the outer braided jacket is rendered more thorough and uniform.

The advantages gained by the proposed construction are many. Electrical cables of the type described herein are used frequently in building where connections must be made at frequent intervals in what are commonly known as outlet boxes. In such cases, it is general practice to remove the outer braid and the strip 10, and where the inner wrappings are clean, it is a sim 1e matter to unwrap them so that the con uctor may be secured to the terminal.

Furthermore, the flexibility of the cable is increased when constructed in the manner described, for in the old constructions the externally applied compounds penetrate the outer braid and seal the inner wrappings thereto, whereas in the present cable, the individual conductors may move freely within the outer jacket.

It also appears that the fire and moisture resistant qualities of the cable are improved by the present construction.

It will be understood that the invention may be variously modified and embodied within the scope of the subjoined claims.

We claim as our invention:

1. An article of manufacture comprising,

jackets comprising fibrous material assembled and enclosed within a fibrous outer sheath to form a cable, a sticky protective compound incorporated in the outer sheath, and a thin sealing layer enclosing the assembled conductors and separating said outer sheath from the conductors, said layer non-adhesively engaging the insulated conductors to keep the protective jackets clean of said protective compound and facilitate movement of the insulated conductors within the outer sheath.

2. An article of manufacture comprising. in combination, a plurality of insulated conductors having separate overlying protective jackets comprising fibrous material assembled and enclosed within a fibrous outer sheath to form a cable, a sticky protective compound incorporated in the outer sheath, and a. sealing layer comprising a spirally wrapped overlapping thin tape enclosing the assembled conductors, said layer separating said outer sheath from the conductors and non-adhesively engaging the insulated conductors to keep the protective jackets clean of said protective compound and facilitate movement of the insulated conductors within the outer sheath.

3. An article of manufacture comprising, in combination, a plurality of insulated conductors having separate overlying'protectivc jackets comprising fibrous material assembled and enclosed within a fibrous outer sheath to form a-cable, a sticky protective compound incorporated in the outer sheath, and a sealing layer comprising a thin paper tape wrapped about said insulated conductors with an overlap and enclosing the assembled conductors, said layer separating said outer sheath from the conductors and non-adhesively engaging the insulated conductors to keep the protective jackets clean of said protective compound and facilitate movement of the insulated conductors within the outer sheath. v

4. An article of manufacture comprising, in combination, a plurality of insulated conductors having separate overlying protective jackets comprising fibrous material assembled and enclosed within a fibrous outer sheath to form a cable, a stearin-pitch compound incorporated in the outer sheath, and a thin sealing layer enclosing the assembled conductors and separating said outer sheath from the conductors, said layer non-adheductors and separating said outer sheath from the conductors, said layer non-adhe sively engaging the insulated conductors to keep the protective ackets clean of said protective compound.

6. An article of manufacture, comprising, in combination, a conductor having-an insulating covering comprising interwoven fibrous strips and binding threads and a wrapped strip of fibrous material, a longisaid conductor and a jacket having aprotective compound incorporated therein to prevent substantial penetration of the-protective compound inwardly of the jacket.

8. An article of manufacture, comprising,

in combination, a plurality of insulated conductors, an outer jacket surrounding said conductors, a rotective compound applied to said outer acket, and a relatively thin sealing layer enclosing all of the insulatedconductors in said jacket so as to prevent substantial inward penetration of said protective compound, said sealing layer comprising a crimped paper.

9. An article of manufacture, comprising, in combination, a pair of conductors having insulating coverings wherein a braided jacket of paper elements and binding threads is covered with a spiral strip wrapping, a jacket having a protective compound incor porated therein, and sealing means tending to prevent 'a substantial inward penetration of said compound comprising a. longitudinal wrapping of crimped paper, the side edges of which overlap.

10. An article of manufacture comprising in combination, a conductor having an insulating covering, a jacket having a protective compound incorporated therein, and a sealing layersurrounding said insulating covering beneath said j ac et to prevent substantial inward penetration of said compound,

said sealing layer comprisinga wrapping of relatively thin crimped paper applied with its adjacent edges overlapping.

In testimony whereof, we have signed our name to this specification this 27th day of July, 1927.

f ANTHONY A. BENNER.

RUDOLPH A. SGHATZEL.

tudinal wrapping of crepe paper, and a jacket for the whole.

7. An article of manufacture, comprising, in combination, a conductor, a bralded ack'- et for said conductor, a strip wrapping surrounding the braided jacket, and a surrounding covering wherein a relatively thin crepe paper sealing layer is positioned between

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