US1757049A - Armored electric cable - Google Patents

Description

y 6, 1930. G. A. JOHNSON 1,757,049

ARMORED ELECTRIC CABLE Filed- Sept. 20 1926 INV EN TOR.

Patented May 6, 193D UNITED TAT S PATENT} OFFICE GUSTAVE A. JOHNSON, OI IRVINGTON, NEW JERSEY, ASSIGNOR '10 AMERICAN METAL MOLDING 60., A CORPORATION OF NEW JERSEY aamonnn ELECTRIC (maria Application filed September 20, 1926. Serial No. 188,461.

This invention relates, generally, to an improved constructlon of armored electric cable for use 1n electnc wiring lnstallations.

This invention has for its principal object 5 to provide a novel construction of armored electric cable, the electric conductors of which are provided with an inexpensive but nevertheless highly efiicient arrangement and relation of insulation mediums combined together in a novel form and manner, to the end that each conductor is adequately separated electrically from the other, while being at the same time united in a single cable structure possessing the desired degree of flexibility, especially suitable for enclosure within flexible metallic armor the relation of the combined insulation mediums being such that the cable may be readily flexed or bent without risk of rupture or other injury detrimental to the necessary electrical segregation and separation of the conducting wires encased therein. Other objects of this invention, not at this time more particularly enumerated, will be clearly understood from the following detailed description of the same. The invention is clearly illustrated in the accompanying drawing, in which is. shown an embodiment of this invention in the form of a two wire cable, each wire being insulated from the other and at the same t1me united in cable form by the novel arrangement and relation of combined insulation mediums, and the whole enclosed in flexible metallic armor, all agcording to the principles of this invention; and in said drawing various portions of the combined insulation mediums are shown progressively broken away to disclose the in dividual' elements and the combined relation thereof one to the other.

Referring to said drawing, the reference character 1 indicates one metallic wire or electric conductor and 2 indicates another such-wire or conductor; said wires or conductors are ordinarily made of cop er, one .serving as a delivering line of an e ectric circuit and the other as a return line thereof.

The wires or conductors 1 and 2 are each provided with an inner covering of rubber insulations Each wire or conductor is v stance, such as asphaltum,

provided, over the body of rubber insulation 3, with an inner wrapping of paper 4. This inner aper wrapping 4 is preferably of -flat strip orm spirally wound in one direction, e. g. from left to right, about the entire length of the wire or conductor. It is preferable to provide the surface of the rubber insulation, prior to the application thereto of the inner paper wrapping 4, with a coating 5 of a non-drying and non-hardening tacky substance having adhesive qualities, such as asphaltum, thus assuring a close bond between the wrapping 4 and the rubber coated wire conductor, and eliminating air spaces or pockets therebetween. After the inner paper wrapping4 is thus applied to each rubber coated wire or conductor, or during the operationuof so applying the same, the outer surface of said inner wrapping 4 is coated with a covering layer 6 of a'suitable non-drying and non-hardening tacky subwhereupon a second or outer wrapping of paper 7 of flat strip form isapplied over the inner paper wrapping 4. This outep paper wrapping is also spirally wound, but in an opposite direction, e. g. from right to left,about the entire length of the wire or conductor, and'so that the convolutions'of said outer paper wrapping 7 will run substantially crpsswise of the convolutions of said inner paper wrapping 4.

After the respective wires or conductors 1 and 2 have received the primary insulation elements arranged and combined therewith in the manner above described, the same are laid together in side by side relation, where upon an inner enveloping wrapping of paper 8 is applied in common to the laid together conductors. This inner enveloping paper wrapping 8 is referably of flat strip form spirally wound: 1n one direction, e. g. from left to right, and preferably in such manner that its convolutions cross the convolutions of the outer paper wrappings 7 of the primary insulation of said respective conductors. Before or during the application of said inner enveloping paper wrapping 8, the laid together conductors are provlded with a coating 9 of a non-drying and non-hardening tacky substance having adhesive qualities, such as asphaltum, thus assuring a close bond between the inner enveloping paper wrapping 8 and the said primary insulation of the laid together conductors, while at the same time eliminating air spaces or pockets therebetween. After the inner enveloping wrapping of paper 8 is applied as above described, or during the operation of so applying the same, the exterior surface of said wrapping 8 is coated with a ing coatings of asphaltum, provides a secondary insulation common to both of the conductors 1 and 2.

After the conductors 1 and 2 are thus provided with their individual primary insulation and the secondary insulation common to both, whereby they are united in desired flexible cable form, a suitable metallic armor 12 is applied thereto in the usual manner 'familiar to those skilled in the art. Said metallic armor 12 ma consist of one or more metallic strips hehcally wound with their convolutions suitably interlocked one with the other, so that a desired degree of flexibility is provided for.

The character of the aforesaid novel -combined primary and secondary insulation with which the'conductors are provided is such that a very eflicient electrical segregation and separation of .each conductor or wire as well as a joint insulative shield therefor is assured; the various elements 'of this insulation structure each contributes in association with the others strong dielectric properties,

since the respective materials, viz. rubber,

paper and asphaltum are each characterized by the possession of dielectric qualities. The tacky natureof the asphaltum assures both the'desired bond between the associated paper wrappings, while nevertheless permitting relative movement between the overlying wrappings when the cable is flexed without risk of the occurrence of ruptures orother selparation'under bending or pulling strains. T e assurance against opening of naps, breaks, ruptures, perforations or the li e is further guaranteed by reason of the relative cross wrapping of the convolutions of the several paper wrappings.

It will be'noted that the novel insulation,

' by reason of the arrangement and relation of the several elements thereof, provides a substantially closely bonded and practically homogeneous insulation mass, which avoids all necessity for employing comparatively expensive fabric sheaths, and consequently not only is a very efficient insulation provided, but also one which is comparatively inexpensive both from the standpoint of cost of materials, as well as in labor costs involved in its production. 3

It will be understood that while I have described the primary and secondary insulation layers as including but two spirally wound paper wrappings each, it will be nevertheless within the principles and scope of this invention to employ more than two wrappings if it should be considered desirable.

Having thus described my present ,invention, I claim v 1. As a new article of manufacture, an electric cable having a plurality of wire conductors laid side by side, each conductor having a primary insulation comprising a covering sheath of rubber next thereto, a plurality of paper wrappings spirally wound ver said rubber sheath in such manner that the convolutions of one wrapping lie crosswise relative to the convolutions of an underlying wrapping, said wrappings being bonded together and to said rubber sheath by intermediate layers of a non drying and non-hardening tacky substance; a secondary insulation common to and enveloping the thus primarily insulated conductors, comprising a plurality of enclosing paper wrappings spirally wound thereupon in such manner that the convolutions of one wrapping he crosswise I relative to the convolutions of an underlying wrapping, said enveloping wrappings being also bonded together and to said primary insulation by intermediate layers of a nondrying and non-hardening tacky substance; alrid an exterior metallic armor applied over a 2. As a new article of manufacture, an electric cable having delivering and returning metallic wires, each wire having a rubber sheath covering the same, a primary paper insulation for each rubber sheathed wire comprising paper strips spirall wound thereon so that the'convolutions o the inner striprun in one direction while those of the outer strip run in the opposite direction and thus cross each other, said paper strips being impregnated with and bound together and to the underlyin rubber sheath by a non-drying and non-har ening asphaltum, said wires thus primarily insulated being laid'togethe'r substantially side by side, a secondary paper insulation common to both wires comprising paper strips spirally wound thereover so that the convolutions of the inner strip run in one direction while those of the outer strip run in the opposite direction and thus cross each other, said latter strips being also impregnated with and bound together and the primary insulation by a non-drying and nonhardening asphaltum, said asphaltum in both said primary and secondary insulation permitting relative movement of the paper strips during flexing of the cable without occurrence 5 of gaps or perforations in the insulation, and

spirally about said conductors in the reversedirection to the inner paper strip Wrappings. 20 In testimon that I claim the invention set forth above I ave hereunto set my hand this 26th day of August, 1926.

GUSTAVE A. JOHNSON.

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