US2172760A - Electric cable - Google Patents

Description

s. J. RoscH ELECTRIC CABLE Sept. l2, 1939.

INVENTOR. SAMUEL JLDOJCH.

ATTORNEYS Patented sept. 12, 1939 UNITED STATES ELECTRIC CABLE Samuel J. Rasch, Yonkers, N. Y., assignor to Anaconda Wire & Cable Company, New York, N. Y., a corporation of Delaware Application March 12, 1936, Serial No. 68,427

6 Claims.

' This invention relates to electric cables and more particularly to velectric cables of the portable multi-conductor type. One of the objects of the invention is to provide an improved multiconductor portable cable. Another object is to provide an improved drain conductor for such cables. Still another object is to provide a multiconductor cable with a plurality of drain conductors which are adapted to impart to the cable the desired protection against failure in cablel insulation without deleteriously affecting cable flexibility. Other objects and advantages will be apparent as the invention is more fully disclosed.

Before further disclosure reference should be made to the accompanying drawing illustrating the present invention, wherein Fig. 1 is a crosssectional' view of one speiflc embodiment of the present invention and Fig. 2 is a cross-sectional view of a second specific embodiment.

Referring to the drawing, a multi-conductor portable cable usually comprises a plurality of flexible stranded conductors I, each covered with a layer of insulating material 2, preferably comprised of rubber, and with a layer of shielding tape 3 comprised of electrically conducting material. The plurality of insulated conductors I are laid longitudinally together and the interstices therebetween are packed with insulating material 4 such as fibrous insulation, and the entire assembly is enclosed within an insulating and water impervious sheath 5 comprised preferably of rubber. Drain conductors 6 are embedded ln insulating material 4 and disposed in such posltiongelative to said conductors I as to carry the current load of the said conductors in the event of failure or breakdown of the insulation material therebetween. Drain conductors 6 are electrically grounded in any convenient manner.

In accordance with the present invention drain conductors 6 are hollow and flexible and are formed of a multiplicity of wires or strands of electrically conducting material wound about a core 1 of?l non-conducting material which, as indicated, may be fibrous material commonly employed for filling the void spaces or interstices between the multiple conductors of the cable, such as jute, sisal, hemp, twisted paper or al- 0 ternatively core 1 may be comprised of a dielectric flexible plastic such as rubber. In winding the multiplicity of strands about the core 1, the several strands are arranged relative to each other in such manner as to provide electrical connection therebetween, thereby obtaining the desired extent of electrically conducting cross-sectional area with maximum flexibility. This crosssectional area preferably should be annular but may be any other desired shape.

The drain conductor 1 may be annular as illustrated in Fig. 1 or it may be shaped to more closely conform to the space which it has to fill, such as hollow triangular as shown in Fig. 2 wherein two of the side Walls are concaved to a degree permitting the conductor t0 be placed in closer spaced relation to the current carrying conductors I. If desired the shielding tape 3 may be omitted yand the insulating coating 2 of the several conductors I may be in direct contact with the segmental drain conductors 1 if desired, without departing from the present invention. Other forms of hollow drain conductor may be made by rolling or pressing the conductor of the annular form in an appropriate die, or the same result may be secured by preforming the core and winding the several strands thereon to conform with the exterior surface thereof. Additional filling material 9 is incorporated to give a circular crosssection and the jacket 5' may be a fluid impervious woven fabric covering substantially as indicated. l

By the above described invention, I am able to produce a portable cable having a relatively high flexibility in which the current carrying capacity of the drain conductors is relatively higher than 30 heretofore obtained. Thus added protection to persons handling the cable in service is obtained. The present invention is equally applicable to multi-conductor cables containing two or four conductors, and the three conductor cables illustrated are purely by way of example only. y

Having broadly and specifically described the present invention and given two specific embodiments thereof it is apparent that many modifications and adaptations may be made therein without departing from the nature and scope thereof as may be covered in the following claims.

What I claim is:

1. An electric cable havingv a plurality of elements of circular cross-section, each element comprising a flexible stranded conductor and an enclosing sheath of insulating material, said elements being symmetrically arranged in a cable to form valleys on the exterior of the cable between the elements, fibrous insulating material filling said valleys and leak conductors one in each said valley, said leak conductors comprising a flexible core of insulating material and anA enclosure therefor of helical wires.

2. An electric cable having a plurality of elements of circular cross-section, each element comprising a fiexible stranded conductor and an enclosing sheath of insulating material, said elements 'being symmetrically arranged in a cable to form valleys on the exterior of the cable between the elements, fibrous insulating material' filling said valleys' and leak conductors of circular cross-section one in each said valley, said leak conductors comprising a flexible core of insulat-4 ing material and an enclosure therefor of helical wires. l

3. An electric cable having a plurality of elements of circularl cross-section, each element comprising a flexible stranded conductor and an enclosing sheath of insulating material, said elements being symmetrically arranged in a cable to form valleys on the exterior of the cable between the elements, fibrous insulating material filling said valleys and leak conductors of segmental section one in each said valley, said leak conductors comprising a flexible core of insulating material and an enclosure therefor of helical wires.

4. A cable having a plurality of elements of `circular cross-section, each element comprising a flexible stranded conductor, an enclosing sheath of insulating material and a static shield about said sheath of insulating material, said elements being symmetrically arranged in a cable to form valleys on the exterior of the cable between the Y arranco elements, fibrous insulating material filling said valleys and leak conductors one in each said valley, said leak conductors comprising a flexible core of insulating material and an enclosure therefor of helical wires.

5. A cable comprising a plurality of conductor elements, each element comprising a flexible stranded conductor and an enclosing sheath of insulating material, said elements being symmetrically arranged in a cable and forming valleys at the exterior of said cable between said elements, fibrous insulating material filling said valleys and leak conductors one in each said valley, said leak conductors comprising a hollow structure of helioally bent wires laid side' by side to form a complete enclosure.

6. A cable comprising a plurality of conductor elements, each element comprising a flexible stranded conductor and an enclosing sheath of insulating material, said elements being symmetrically arranged in a cable and forming valleys at the exterior of said cable between said elements, fibrous insulating material filling said valleys and leak conductors one in each said valley, said leak conductors comprising a hollow structure of helically bent wires laid side by side to form a complete enclosure and a flexible sheath enclosing said cable.

SAMUEL J. ROSCH.

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