US1688954A - Electric cable - Google Patents

Description

Oct. 23, 1928.

R. W. ATKINSON ELECTRIC CABLE Filed Sept. 28, 1925 FIBJI.

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Patented Oct. 23, 19 28. I

UNITED STATES v r 1,688,954 PATENT OFFICE.-

I RALPH W. ATKINSON, OF PERTH AKBOY, NEW JERSEY, ASSIGNOB, BY IEBNE 45-.

SIGNHE'NTS, TO'GENEBAL CABLE CORPORATION, A CORPORATION 01 NET JERSEY.

ELECTRIC CABLE.

Application fled September My invention relates to the building of electric cables, and has for its object a cable of superior quality, economicall produced.

In the building of electrica 'cables for cer- 6 tain classes of service it is desirable to enclose the insulated conductor or conductors in a closel fitting, closely adhering thin metal enve ope, such an assembly being1 contained within an all-surrounding lead s eath.

In If the cable be a single-conductor cable, the "lead sheath ordinarily will closely overlie the metal envelope of the insulated conductor if the cable be a multiple-conductor cable, the envelope of thin metal may be applied either to the insulated conductors individually or to the belt insulation which surrounds the whole assembly of insulated conductors. The thin metal envelope so employed serves a number of good ends, and one or another of these good ends-may become particularly important in one installation or another. Among these good ends it will suflice to mention two: First, the closely adhering envelope of metal limits voltage stresses to the region between conductor and envelope, and, in case spaces are opened between t e lead sheath and the underlying body of the cable, as may occur in consequence of manipulation during installation, those spaces wil be external of the thin metal envelope upon theinsulated conductor, and therefore innocuous. But if the thin metal envelope were not present, such spaces would be danlger points, and inevitably in many instances armful and destructive.

A second advantage conseqlilient upon the presence within a cable of a t in metal envelope closely surrounding the insulated conductor lies in the distribution of heat generated within the cable when in service. This advantage is particularly important in multiple-conductor cables, when the envelopes surround the insulated conductors individually. It will sufliceto cite Letters Patent of the United States No- 1,199,789, granted October 3, 1916, on the application of Martin Hochstadter. In the specification of that patent will be found minute description of the thin metal envelope and of its value in the art.

For present purposes it will suffice 'to note that a cable so constructed is a valuable thing in this art, and to point out what hitherto has been proposed concerning the envelope itself, in its mlnute structure and in the mode of its application. It has been proposed, in

as, 1925. Serial 1%. 58,886.

order that this envelope shall adhere closely to the surface of the underlying insulation, to use thin foil. .It has been proposed, in order that the envelo ed body of insulation shall accessible or impregnation with liquid nsulating material, to form the foil 1n a strip, and to lay the strip helically upon the insulated conductor, with a s ace between successive turns of the helix. n such par-' tlcular construction the strip employ. (1 ma be a strip of copper. It has been proposed: in order that the envelope shall be permeable, that it be perforate, or, again, formed of fine wire netting. It has been proposed that the desired metallic envelope be achieved by metallizing the surface of the final wraps of paper of which the body of insulation ordinarlly is built up.

Theengineer w1ll perceive that in the employment of one or another of these particular forms for the thin-metal envelope, one compromise or another is made. In one case there is better penetrability for liquid insulation'. but poorer adherence of the envelope upon the enveloped body; in another case more perfect adherence isgot, but on the other hand there is poor conductivity or perhaps high cost of production.

My invention hes in employing for this purposeand introducing into the structure of the cable at this point a material which, in broader aspect, is not new, although new in this particular application, and a material which, in narrower aspect, 1s new in any application.- I have perceived that electrolytically deposited sheet copper may be produced in proper dimensions for this use and that being so produced it possesses some physical properties and may be made to possess additional physical properties, which peculiarly adapt it to this particular use.

Sheet copper is now produced electro-- lyctially in the following manner. One wall of an electrolytic cell is formed by a metallic roller of relatively large diameter. This 100 roller is made the cathode in the electrolytic cell. Upon it therefore in the progress of the operation of electrolysis, metallic copperis deposited in a constantly thickening layer. The roller is caused to rotate, and in coopera- 105 tion with it, above the surface of the electrolyte, means are provided for removing progressively from it the sheet of copper which has so been deposited upon it. The speed of rotation of the roller 1s such as to 110 afford a sheet of desired thickness. The

sheet whenproduced is washed and is then ready for use.

The only use known to me to which sheet copper so produced has hitherto been put, 15 as a coating for shingles formed otherwise of such relatively cheap and perishable material as-paper.

I have perceived, and by investigation have found, that sheet copper so produced, is pcculiarly useful for forming the thin metal envelope within a cable, mentioned above; and that the cable in whose production it is used, has superiority over cables otherwise like it but whose thin envelope is formed of material hitherto used and of the nature described above. The electrolytically deposited sheet is relatively soft and pliant, and capable, therefore, of close conformation to and adherence to the surface of the body of cable insulation; it is relatively pure and is possessed therefore in high degree of the desired quality of conductivity; it may be made thin enough to possess the necessarily great flexibility required 1nd yet sufiicient in tensile strength to meet the conditions of installation and of service; it may be made in narrow strips, or, being initially produced in wider form, may be cut into strips of width suited to my purpose; and it may be produced in strips of indefinite length. I have further perceived that, by modification of the structure of the roller upon which the sheet of copper is deposited, the strip which is produced may be produced as a perforated strip. Perforation may be anessen'tial ch aracteristic of the strip, innate from the strips formation, and present without mutilation. To that end, the surface of the roller is rendered non-conducting over certain limited areas, and from this it will follow that the produced strip will possess interruptions in continuity,holes, that is to say,--corresponding to the non-conducting spots upon the roller. Finally, I have perceived that a strip adequate to produce the desired envelope in cable-building my thus be produced at very considerably less cost than otherwise has been attainable.

' It will be perceived that these are matters, most of them, which are of little or no importance in shingle manufacture, to which hitherto, so far as I am aware, the use of electrolytically deposited sheet metal has been limited.

In the production of a perforate strip, the surface of the roller upon which the strip is formed will, as I have said, be non-conducting over specific areas. This character of roller surface may be effected by forming holes in the roller and then filling the holes with nonconducting material, such as bakelite, for example. Theoretically, such holes, when formed, might be left unoccupied; but practically, there would be electrolytic deposition within the holes, and to that extent the consequent perforations in the produced sheet of copper would be dimini. ed in size; and, furthermore, the sheet would have projections from its surface, undesirable in themselves, and presenting difficulty in removal of the sheet from the roller. Preferably the plugs of non-conducting material inserted in the holes in the roller not only fill the holes, but rise somewhat above the general surface of the roller. The plugs so formed need not interfere with the stripping of the sheet from the roller, and will give better precision to the rim of the perforation.

In the accompanying drawings Fig. I is a view in perspective, showing dia rammatically the somewhat dissected end 0 a cable in the structure of which my invention is present; Fig. II shows in plan and in one specific form the strip of metal in which my invention centers.

Fig. I of the accompanying drawings shows the end of a multiple-conductor cable. ,The conductors are indicated by the numeral 1 the envelopes of insulation which surround the conductors individually are indicated at 2; the lateral fillers at 3; the central filler at 4; 5 is the belt insulation; and 6 the cable sheath. The Wrap of strip material which, formed of electrolytically deposited metal as I have described and applied in this instance upon the insulating envelopes 2 of the individual conduc7tors, constitutes my invention, is indicated at It will be understood from what has gone before that the wrap may be similarly and alternatively applied to the fillers, central or lateral, or to both. That is to say, the invention may be practiced in the building of the cable shown and described in Letters Patent of the United States, No. 1,132,452, granted March 16, 1915, on the application of Charles W. Davis. In that patent the fillers of a multiple-conductor cable are shown to bemetal-wrapped,and the wrapping for these fillers may be the wrapping 7 of Fig. I, having the nature and character described above. Again the wrap ing may be laid upon the belt insulation and beneath the sheath. The application of the invention to a single-conductor cable requires no further and particular illustration.

Fig. II is a view in plan of the strip 7. It is here shown to be perforate, and it will be understood that this perforate condition may be innate in the strip from its formation, and that therefore no separate operation of perforation has been performed upon it, ensuing upon its formation, and that it is free from minute deformations such as may be incident to mutilation of an initially imperforate strip.

I have described my invention as practiced in the use of a copper strip. While it is true that under existing circumstances copper. is the material which will be preferred for the purpose described, the invention, manifestly,

ture, and tenacity which characterize electrolytically deposited copper, and its perforations being smooth-edged as is characteristic of perforations which are innate in the formation of the electrolytically deposited strip, the whole being surrounded by a metal sheath.

In testimony whereof I have hereunto set my hand.

RALPH W. ATKINSON.

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