US1266006A - Cable construction. - Google Patents

Description

H. w; FISHER.

CABLE CONSTRUCTION. APPLICATION FILED lllLY 10. I916.

Patented May 14,1918.

WITNESSES UNITED STATES PATENT OFFICE.

HENRY w. FISHER, or HUGUENO'I. rAnx, NEW YORK, AssIeNon. r0 srANnAnn UNDER- GROUND cABLE' COMPANY, or PITTSBURGH, PENNSYLVANIA, A CORPORATION or PENNSYLVANIA.

CABLE CONSTRUCTION.

Specification of Letters Patent.

Patented May 14:, 1918.

Application flied July 10, 1818. Serial No. 108,376.

' residing at Huguenot Park, Staten Island,

and State of New York, a citizen of the United States, have invented or discovered certain new and useful Improvements in Cable Construction, of which improvements the following is a specification.

My invention relates to improvements in the construction of cables, the conductor or conductors of which are stranded; that is to say, cables whose conductor or whose several conductors are individually composed and made up of a plurality of parts, a bundle of wires, each of which carries a portion of the whole current. I show and shall describe my invention applied in the construction of a multiple-conductor cable, but it will be understood in the sequel that it is of general applicability in cable-0on panying drawings, in which Figure 1 shows in cross-section a multiple-conductor cable with sector-shaped conductors, in the making of which, in the manner hereinafter described, my invention is realized; Fig. 2 is a like view and on lar er scale of one of the conductors of the calfle as it is completed and before insulation is applied to it and before it is assembled with other like insulated conductors to form the cable; and Fig. 3 is a view similar to Fig. 2, but illustrating a modification in structure. Fig. 1 shows a three-conductor cable, such as is used for carrying three-phase alternating currents. The conductors with their envelops 1 of insulation are in the making of the cable twisted together and covered with the belt insulation 3 and the lead sheath 4. Of course the cable here shown in detail is exemplary; the invention is applicable to cables of all sorts in which stranded conduc tors are employed, andin other respects the cable may be such as the builder wishes.

The advantage of a. stranded conductor lies inthe fact that it is more flexible than an integral conductor ofthe same cross sectional area; and, consequently, as between cables including the same number of conductors of equal carrying capacity, the conductors of one being single and the conduc-,

tors of the other stranded, the cable which has stranded conductors is the more flexible and-in that respect better suited to conditions of manufacture, installation, and service. On the other hand, a' stranded conductor cable is of necessity more bulky than a solid-conductor capable of equal carrying capacity, because a bundle of wires of a given total cross-sectional area is more bulky than a single wire whose cross-sectional area is the same as the total of the wires of such bundle. It follows that, other things being equal, a stranded-conductor cable. while more flexible, is also larger than a solid-conductor cable. And it will of course be recognized that'the cable which has larger conductors requires more insulating material and more sheathing material and is therefore in these respects more expensive than the solid-conductor cable. Besides, service conditions are generally such that the smaller the cable the better'so long as current capacity is not diminished.

It is with economy of space in view that sector-shaped conductors are used in multiple-conductor cables; for, with a given minimum permissible thickness of insulation between conductors, approximation to sector shape admits of greater compactness than retention of circular shape for the individual conductors. In dealin with stranded conductors,particularly 1n the case of the sector-shaped stranded conductor-it has heretofore been proposed to compact together the assembled strands, to compress the bundle, to pass the assembled stranded conductor through roll pass or die, or to shape the bundle under a hammer, crowding and compacting the strands together, crushing them to some extent out of their original shape, so as to reduce the over-all thickness of the conductor. There is, however, disadvantage in so compacting the bundle of strands. It is inevitable that, in conse quence of the compressive action of die roll or hammer, sharp or rough points and edges will be developed, and the greater the compressive strains the more pronounced will be this result. Sharp and rough points and edges are undesirable; they tend to damage .in building up the applied insulation and they become points of weakness where (the cable being in service) the insulation may break down, more especially because of the increased electric density at sharp points, where actual discharges may take place.

My invention enables me to enjoy the advantage of compressing the stranded conductor without the disadvantage of producing danger points. It consists essentially the heart or center portion of the conductor and subjecting that portion when so built up to such compressive and consolidating action as has been indicated above, and then in applying to and upon the portion of the conductor so assembled and dealt with a surrounding and enveloping portion which also shall be part of the completed conductor functionally, and which shall be smooth-surfaced (that is to say, free of dangerous points and angles) and so the dangers which have been lndi-cated above and which are defects in such cables as previously made are avoided and overcome.

While this invention may be carried out in various specific ways, I shall describe it carried out in my preferred manner.

The envelop of this preferred form consists, as will presently appear, in a wrappedon layer of smooth wire. The invention in general terms consists in the application of an envelop whose surface is free of such points and angles as would constitute danger points; and manifestly a wrapped-on layer of smooth wire afi'ords an envelop possessing that desired character.

Referring to the drawings, and particularly to Fig. 2, the stranded conductor there shown, consisting of a-bundle of strands, may for present purposes be described to be composed of 5, and an outer surrounding layer of strands 6. The central bundle of strands may be a bundle of straight-away wires or it may be a bundle of wires twisted in familiar manner. If made up of straight-away wires, the component wires may be of special shapes and special grouping in various sizes. The central blmdle 5, however, after it has been made up, is compressed and compacted and reduced in over-all dimensions in any suitable or preferred mannor, as by hammering or rolling or otherwise. When it has been so compressed and two parts; a central bundle diminished, the outer enveloping layer 6 is laid on, this layer being composed of smooth wire,- in a suitable number of strands, wrapped about the consolidated central body. Fig. 3 shows that instead of a single layer a plurality of layers of smooth glire may be wrapped on the central bune. I a It will be understood that it is only in relation to these construction-operations that the central bundle 5 and the enveloping layer 6 can be considered separate parts or separate bodies; for, in the matter of current carrying, the conductor is one stranded conductor.

Manifestly the outer enveloping layer 6- may be made ,of relatively fine wire, and accordingly be in and of itself a layer of small bulk.

From the foregoing description it will be plain that, so far as concerns the central bundle 5, I gain the benefit and advantage of compression; and that, by the presence of the super-added and uncompressed layer 6, I avoid the disadvantage and dangers of a rough and sharp-edged conductor.

It is manifest that, while I have shown my invention in its application to a multiple-conductor cable with sector -shaped stranded conductors, it is applicable genera-lly to stranded-conductor cables.

I claim as my invention:

1. The method herein described of making a stranded cable conductor which consists in gathering a bundle of strands, compressing the bundle when gathered with incidental development of shar edges, and enveloping the compressed an sharp-edged bundle in a superadded layer of a smooth surface conductor.

2. A cable conductor composed of a central bundle of strands brought together and compacted and shaped one upon another by pressure into a bundle having incidentally developed sharp edges, and a layer of smooth surfaced conductor enveloping the compressed and sharp edged bundle.

In testimony whereof I have hereunto set my hand.

I HENRY w. FISHER. Witnesses NORMAN C. Davrs, JOHN KEER PRoEcK.

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