US448604A - William a - Google Patents

Description

(No Model.)

W. A. CONNER.

ELECTRIC CABLE.

No. 448,604. Patented Mar. 17,1891.

Unirse Sterns Pitre-Nr Strien.

VILLAM A. CONNER, OF PITHSDURG, PlCNNSYl-XNLX, ASSlGNOl T() lllE STANDARD VNDERGROUD CABLE COMPANY, OF SAME ELECTRiC CABLE,

SPECIFCATION forming part of Letters Patent No. 448,604, dated March 17, 1891. Application filed November 8, 1890. Serial No. 371,005. (No model.)

To aZZ who/1t it may con/cern:

Be it known that l, WILLrAn A. CoNNnn, a citizen of the United States, residing at Pittsburg, Allegheny county, Pennsylvania, have invented certain new and useful Improvements in Electric Cables, of which the following is a specification.

My invention relates to electric cables, and more particularly to that class which are generally termed lead-covered cables.7

In cables of this class, especially when desired for telephoneservice, it is extremely important to obtain the lowest possible speciiic inductive capacity, and several conductors composing an electric cable are generally separated from each other by dielectries of various kinds, usually a composite of fiber or paper wrapped or braided thereon and saturated with some ii'isulating compound, such as ozite, parafine, resin-oil, dsc. rihese covered conductors before saturation are bunched together in any desired number or arrangement, and bound closely together by a fibrous mesh or wrapping to form the cable core. The core thus constructed may or may not be placed in a hot-air chamber for the purpose of expelling any moisture that may be present, and it is then placed in a penetrating` bath of hot insulating compounds, such as above named. This has the effect of sealing the fiber against the subsequent absorption of moisture. Finally, the cable-core thus prepared is usually given a protecting-coating which shall beimpervious to water.

It is well known that dry air is very much lower in specific inductive capacity than any of the known insulatingcompounds or fibers, and it is therefore preferable to omit the insulating compounds whenever possible. Several attempts to utilize this fact have heretofore been made. Electric cables have been constructed and used consisting of dry cotton insulated cores placed in a sheath of lead pipe without any insulating compound whatever, and this results in considerably lowering the inductive Arpacity between the various conductors of the cable; but such cables have been found nnserviceable and unreliable, generally from the fact that any defect or opening in the protectiiig-sheath, even of a very minute character, renders a considerablc length of the core liable to the intrusion of moisture and the consequent loss of insulation. Cables have also been made in which plugs or lengths of sealing material have been introduced at intervals in thelead pipe for the purpose of eonfiningany damage from access of water or moisture within the limits of sections oi' the cable between two adjacent plugs of sealing material.

rlhe object of my present invention is to overcome the disadvantages above set forth and to produce a cable which shall have the lowest possible specific inductive capacity, and at thesame time be simple, cheap, and effective; and my invention consists in a eable constructed and arranged substantially as hereinafter pointed out.

ln the accompanying drawings, Figure l is a perspective view showing a cable embodying my invention, and Fig. 2 is a side view showing a modified construction. Fig. El isa longitudinal cross-section of Fig. l, and Fig. et is an enlarged detail view showing a single conductor covered with insulating material, forming interstices or open-work spaces for the air.

As before stated,the essential object of my invention is to provide a cable having all the advantages of the dry-liber core, and consequently low specific inductive capacity, and yet have the conductors of the core fully protected against access of moisture; and my iuvention may be stated, perhaps, more concisely as consisting in a number ot` electric conductors covered with an insulating mcdium of any character-such as cotton, jute, paper, gutta-percha, dce-preferably applied so as to form an open mesh or structure, leaving` numerous interstitial air-spaces around the conductors. The individual conductors so insulated may then be laid up into acore to form what is known as a straight-away cable, or they may be twisted in pairs, threes, fours, or otherwise, and then these combinations laid up in a core, depending, of course, upon the particular purpose for which the cable is to be used, The core so prepared is preferably placed in a hot-air chamber for the purpose of expelling all the moisture which may be present in the brous material.. Over IOO or molten condition is formed or compressed around the core, as is usual, I provide an additional coverin g to the water-proof covering, consisting of fibrous tape or braid which has preferably been previously saturated with some insulating substance, such as some form of hydrocarbon, for instance, which melts only at a high temperature, and which will thoroughlyproteet the water-proof covering of the core and prevent the latter from becoming conductors.

burned, scorched, or injured in any way in the application of the lead covering.

Thus referring to the drawings, l 2 3, the., represent single conductors, each of which is covered with an insulating medium preferably in the form of fibrous material or equivalents, wrapped or covered so as to leave interstices or air-spaces through the covering and between it and the conductor.

3 4 represent two insulating-eonductors twisted to form a pair, while 5, G, and 7 represent three insulating conductors twisted together so as to leave interstices or open spaces on the covering surrounding the conductors. These covered conductors are then hunched in any desired form to form a core A, the conductors being loosely grouped together, so that there will be other interstices or airspaces between the covered insulated Wires or This core having been dried to expel the moisture is then wrapped or otherwise covered with a coating B of some thoroughl y water-proof compound or material, and I have shown it as consisting of a tape spirally wound around the core, the tape preferably being `saturated to render it Waterproof, or a rubber tube B', Fig. 2, may be used in place of a coating B. The core as thus formed is rendered practically impervious to moisture, and the dry air in the interstices'of the core acts to elfeetively reduce the electrostatic capacity, and it will be understood that the ends of the core may be sealed for transportion or storage with the samewinding material or with any sealing or insulating compound to prevent the entrance of moisture. This core as thus wrapped and protected is then covered with a sheathing C of some material capable of withstanding a comparatively high degree of heat, and I have shown it consisting of a fibrous tape spirally wound,

sheathing C between the protective covering B and the core prevents any injury to the core which would admit or permit the entrance of moisture, and I am therefore enabled to produce acable in which there is the lowest possible specific inductive capacity at a comparatively small cost, and one which has been found to be exceedingly durable and capable of withstanding the action of the elements without danger. l

l/Vhat I claim is- Y l. An electric cable consisting of a number of conduetors,eaeh covered with afibrous insulating material, the conductors being grouped together to form a core, the corebeing provided with water-proof covering and a sheathing ot' material capable of withstanding a comparativelyhigh degree of heat, and an exterior protectivecoating of lead, substantially as described.

2. A11 electric cable consisting of a number of conductors covered with fibrous insulating material, the conductors being grouped together to form a core, and having interstices or air-spaces between the conductors, as set forth, a covering consisting of a tape or tube of Water-proof material surrounding the conductors, a sheathing of ibrous material saturated With hydrocarbon having a comparatively high melting-point surrounding the Water-proof covering, and a protective covering of lead, substantially as described.

In testimony whereof I have signed my name to this specification in the presence of tWo subscribing witnesses.

' VILLIAM A. CONNER.

Witnesses:

ARTHUR A. ANDERSON, HORACE G. WoRMsLnY.

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