US 2234675 A
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March 11, 1941. G. A. JOHNSON ARMORED ELECTRIC CABLE Filed July 26, 1939 INVENTOR R EAvronlzvs Patented Mar. 1l, 1941 UNITED STATES PATENT OFFICE 3 Claims.
This invention is directed in general to improvements in electric conductors in the form of armored cable. l
More specifically my invention provides a novel 5 construction in armored cable whereby great Savings are effected in cost of materials, freight, storage space and labor, etc.,\ all as will be brought out more fully hereinafter.
Still more specifically my invention provides a novel arrangement of the insulated conductors of the cable with respect to each other and a novel arrangement of the fibrous covering for the same, whereby a great reduction is effected in the size of the armor necessary to envelop the insulated and 4bound together conductors. makes for a saving in materials as well as in storage space and freight charges.
My novel construction also promotes natural circulation of air through the armor about the 20 insulated and bound together conductors, for purposes of air cooling the same, which, as will be appreciated by those skilled in this art,` is of great advantage as compared with existing structures. 'f
Prior to my invention armored electric cables of the general type to which my invention relates usually have been made up of two or more individually insulated conductors, twisted together and enclosed in a jacket of paper, cotton or other fibrous material applied in various ways, this assembly being armored by forming an outer iiexible galvanized metallic armor about the same. In some constructions the individually insulated conductors are additionally wrapped in 35 paper before being twisted together.
As compared with such cables I have provided a very much simpler construction, and by the same token a much less expensive one. In accordance with my invention, broadly speaking,
g I propose to dispose the insulated conductors side by side in untwisted parallel relation. 'I'he insulated conductors Aso disposed are enclosed and bound together in a iibrous covering, such, for example, as a paper tape wound helically about the straight parallel conductors, the adjacent turns of the tape being overlapped. The outer flexible metallic armor, which takes the form of a round tube, is formed -about this assembly.
Inasmuch as the individually insulated conductors are straight and laid side by side in parallel relation, it will be appreciated that a considerable saving is effected in the amount of Imaterial required for a given length of cable so far as conductor and insulation for the conductor are concerned. It will be appreciated, also, that by not twisting the conductors together additional savings are effected in the elimination of the labor, machinery, etc. necessary for the twisting operation, and in the decrease in the amount of fibrous material necessary to enclose the conductors as above set out.
It will be appreciated, also, that the overall dimensions of this assembly, as compared with the prior constructions above referred to for the same duty, have been very materially reduced, so that the overall dimensions of the armor is correspondingly reduced with a great saving in armor material. As a more concrete example of the advantages of my invention from an economical point of view, my invention eiects a saving of aroun-d 18% per thousand feet, which in a two conductor cable employing No. 14 Wire is about $3.50 per thousand feet. This is a tremendous saving when it is borne in mind that hundreds of millions of feet of these cables are produced annually.
Further savings are effected by my improved construction, in that by materially reducing the cable in its overall dimensions the same is much easier to handle, thereby effecting a saving in installation labor.
An embodiment of my inventonhas been illustrated in the accompanying drawing, in which:
Fig. 1 is a fragmentary m'de view in part section of a two wire armored cable constructed in accordance with my invention; and
Fig. 2 is a section taken through Fig. 1 on the line 2 2.
Before proceeding to a detailed description of the drawing, I might say that the same has been made on a very much enlarged scale, for purposes of clarity.
Referring to the drawing in detail: 2 and 4 designate the two conductors of my improved cable. I have shown a two conductor cable merely for illustrative purposes, it being understood that the number of conductors actually employed may exceed two. These conductors may be insulated with any suitable insulating material. I have elected to show them individually insulated with a rubber compound 6, in which event the conductors are usually tinned before application of the insulating material.
The individually insulated conductors 2 and l instead of being twisted together, as in prior practice, are disposed side by side in parallel relation. This is clearly seen from the drawing.
By the side of the insulated conductors I provide an identification cord 8. It is the universal practice in cables of the type to which this invention relates, to identify the cable by imprints in thearmor covering. This has serious disadvantages, inasmuch as the imprint cuts through the galvanizing coating of the armor, with the result that the eiectiveness of the galvanizing is destroyed, and the armor corrodes, the corrosion spreading and eating away the armor until the same is punctured to bare the enclosed cable. By providing an identification cord, as I have done, itis evident that this trouble is eliminated.
With the conductors and identification cordA disposed as outlined, a brous covering i@ is applied to the same. This covering advantageously may be paper tape, in which event I suggest saturating the same with liquid asphaltum to render conductor insulation, with a wide overlap, so that throughout the length of the cable I have van insulating wall of brous material, three layers thick, as seen at I2. the turns of this material being bonded to each other and to the conductor insulation.
The structure thus provided is substantially oval in cross section, as seen in Fig. 2. About the same I form a tube of ilexible galvanized metallic armor i4, which may be of usual construction and which is round in cross section. As above pointed out, the conductors 2 and o are not twisted together, but are so disposed that they extend at all points throughout the cable in the same direction as the longitudinal axis of the armor tube.
In using the armored cable it is usually necessary to cut the armor oil for some distance from the ends of the cable, and in order that the cable insulation and conductors may be protected against the abrading action of the rough sharp edge oi' the ends of the armor when the cable is exed I insert shields it, of insulating material such as compressed ber, into the ends of the armor between the armor and the brous covering it. Each shield interlocks with the armor as seen at iii, and is conveniently made in two semi-cylindrical sections. When using sectional shields they are so inserted into the armor that the edges of the shield sections abut in the air channels 2@ and 22 provided by enclosing the conductor assembly, which as above mentioned is oval. in cross section, in a metallic armor which is round in cross section.
It will be quite apparent from all oi the foregoing that my invention provides an armored cable construction possessing many advantages over existing. constructions.
By binding the individually insulated conductors together in straight. untwisted, parallel relation a substantial saving is eiected in the amount of material required for av given footage. Likewise it will be apparent that the overall dimensions of the cable have been reduced and that therefore less material is required for armoring. Inasmuch as the amount of material per given length has been reduced an additional saving is effected in storage space and shipping charges, all of which, as above pointed out, may amount to as much as 18% per thousand feet of cable, about $3.50 per thousand feet in a two conductor cable employing No. 14 wire.
My construction has the further advantage in that inasmuch as the bound together conductors are oval in cross section while the cross section of the armor is circular, straight air spaces, as seen at 2@ and 22, are provided extending uninterruptedly throughout the length of the cable forofreer circulation of air through the armor along the exterior of the conductor assembly when rise in temperature occurs.
It is to be understood that changes may be made in the details of construction and arrangement of parts hereinabove described Without departing from the spirit and scope of my invention.
What I claim is:
l. An electric cable comprising a pair of individually insulated electric conductors, a brous covering about the same binding the conductors together to provide an assembly which is substantially oval in cross section, and an outer exible metallic armor tube of substantially circular cross section about the brous covering, whereby continuous uninterrupted channels are provided between the conductor assembly and the walls of the armor and extending parallel to the longitudinal axis of the armor.
2. An electric, cable ,comprising a plurality of individually insulated electric conductors, a fibrous covering about the same binding the conductors together and providing an assembly having opposed substantially flat sides, and an outer metallic armor about the fibrous covering, said armor being in the form of a tube which is substantially circular in cross section, whereby continuous channels are provided between the substantially at sides of the conductor assembly and the curved wall of the armor, these channels being continuous and unobstructed and extending substantially parallel to the longitudinal axis of the surrounding armor tube.
3. An electric cable comprising a pair of individually insulated and elongated electric conductors laid side by side in substantially parallel relation to each other, a binding 'cover about said pair of conductors binding said pair of cony ductors together to provide an assembly which is substantially oval in crc'ss section, and an elongated outer lexible metallic armor tube of substantially circular cross section about said assembly whereby substantially continuous and uninterrupted elongated channels are provided on opposite sides of said assembly and dened by the major faces of said oval assembly and the opposed inner face of said tube.
GUSTAVE A. JOHNSON.