US2251262A - Nonmetallic sheathed conductor - Google Patents

Description

Aug. 5, 1941. c. w. ABBOTT NONMETALLIC SHEATHED CONDUCTOR 2 Sheets-Sheet l Filed Aug. 3, 1940 lv'ENToR CMAQ/ Es W A515077' BY www Aug. 5, 1941. c. w. ABBoTT NONMETALLIC SHEATHED `CONDUCTOR Filed Aug. 3, 1940 2 Sheets-Sheet 2 @gw mm L31.

lll. lllw 1 l U mi l NW. mail MV Q. Am, SEQ

R V.. m .m EA lo Wmm i Q MEW Patented Aug. 5, 1941 AUNITI-:D STATES PATENT OFFICE.

This invention relates to electrical conductor construction and particularly to insulated electrical conductors intended primarily for installation in buildings to form the circuit or circuits usually for lighting, power, and like uses.

One of the objects of this invention is to provide an insulated conductor or so-called cab1e" construction that will be inexpensive to manufacture, of'compact construction, and eicient, safe and reliable action and well adapted to meet the widely varying conditions or requirements met with in the building Wiring eld, illustratively in frame and like residence structures, farm buildings, and the like. Another object is to provide an insulated conductor or cable construction utilizing rubber or rubber compounds `and other insulating materials in such a way as toA make it possible to employ smaller quantities of rubber or rubber compound while maintaining adequate and electrically safe insulation appropriate to the various conditions under which the conductor must in practice stand up. Another object is to provide a conductor construction of the above-mentioned nature in whichv insulating Walls of rubber or rubber compound, or the like, may be employed but in a thickness or thicknesses materially less than has heretofore been possible and to provide for such insulating walls of lesser thickness dependable and lasting me# chanicai protection against injury or deformation in the manufacture, handling, or use, of the insulated conductor construction.

Another 'object is to provide improved mechanical protection that will be easy to manufacture, inexpensive in construction, and eiiicient in action, for the rubber or like insulating wall or sheath of an electrical conductor. Another object is to provide mechanical protection of the the cable construction is subjected in actual use tection of the above-mentioned character for the rubber or like insulating wall. or layer takes part, with the rubber wall or layer, in achieving eiiiciently and inexpensively the desired overall dielectric strength or insulation desired for the conductor or conductors of the construction or cable.

Another object is to provide a cable or insulated conductor construction that will have improved operating characteristics with respect to various conditions met with in installations of conductors of this type. For example, where moisture conditions are present, it has happened,

in prior constructions, that elements employed in building up the sheath for the conductor or conductors act as wicks and thus wick the moisture back into the cable structure from the open ends of the latter as in outlets, causing rotting and often giving rise to fungus growths which in turn take part in both so-called dry" and Wet" rot. Sometimes acidic conditions are met with, frequentlxly in farm installations, as in cow barns, and acid fumes or acid-.carrying moisture have been known destructively to attack non-metallic sheathed cable constructions as heretofore employed; for example, a wicking action like that just mentioned in connection with moisture carries the acidity into the internal cable structure with impairment of insulation e characteristics and of mechanical protection. Also, various saturants employed on both internal and external sheathing elements have been known to be attacked or dissolved or their usefulness greatly impaired by such conditions of acidity. Another object is to provide a cable construction that will v dependably and in an inexpensive way overcome after installation, material or harmful injuryI insulated conductor construction in which pro# Another object is to provide an insulated conductor structure or cable ci the above-mentioned character that will dependably function in installations of the character mentioned above without requiring metallic sheathing, or the like, and to provide a non-metallic sheathed cable or insu-lated conductor construction that will be inexpensive, strong, ccmpact, electrically safe and reliable and mechanically and physically resistant in an efficient and lasting manner to the varions and varying hazards to which such conductor, in such instaliations, might be subjected.

Another object is to provide an insulated com ductor construction of the above-mentioned character that has dependable resistance to stretch and thereby to protect the individual wires or conductors against elongation with accompanying diminution in cross-section, when the cable construction is subjected to stress. Another object is to provide a cable construction that will be simple, easy and quick for the electrician to prepare, at its end or ends, for electrical connection, and more particularly to provide for ease and speed of removal of the sheathing or sheathing elements to expose the individual wires or conductors. Another object is to provide for long lasting and dependable distinguishing or identification of polarities of the several conductors where the cable is made up as a plural conductor cable. Another object is in general and in detail toprovide an improved insulated conductor or cable construction of the above-mentioned general kind.

Another object is to provide a dependable and eicient method of manufacturing insulated conductor constructions of the above-mentioned character and one that will lend itself to economic, speedy and efficient carrying out in practice and capable of high rates of production. Another object is to provide a simple and practical method of applying a sheathing element in plastic form to a conductor structure. Another object is in general and in detail to provide an improved method of sheathing a conductor or conductors.

Other objects will be in part obvious or in part pointed out hereinafter.

The invention accordingly consists in the features of construction, combinations of elements, arrangements of parts, and in the several steps and relation and order of each of the same to one or more of the others, all as will be illustratively described herein, and the scope of the application of which will be indicated in the following claims.

In the accompanying drawings in which are shown by way of illustration several of the various possible embodiments of the mechanical features of my invention,

Figure l is a diagrammatic representation of a sequence of apparatus illustrative of several of the earlier steps employed inmy method;

Figure 2 is a similar diagrammatic representation of a sequence of apparatus for carrying out certain subsequent steps of my method;

Figure 3 is a central longitudinal vertical sectional view on an enlarged scale of part of the apparatus of Figure 2 showing its relation to the conductor being operated upon;

Figure 4 is a diagrammatical plan View of an applicator means as seen along the line 4 4 of Figure 2;

Figure 5 is a plan View of an insulated conductor or cable construction with parts progressively removed or broken away or shown in section to show the various elements and their structural interrelationships, and with other parts removed or broken away to show a possible or preferred action of stripping certain of the sheathing elements;

Figure 6 is a similar view showing another form of construction, and v Figure 7 is a View like that of Figure l iilustrating another form of conductor construction.

Similar reference characters refer to similar parts throughout the several views of the draw ings.

In order to make for a readier understanding of the various features of my invention, let it be assumed that the cable or insulated conductor construction is to be installed as part of a building or household wiring system, usually of volts, for lighting and analogous or related purposes; while my invention may be embodied in single-conductor form, it may be and preferably is embodied in plural-conductor form and in Figures 5 6 and '7 of the drawings the several forms there shown, embody, by way of illustration, two conductors I0.and II which may be assumed, when installed, to represent or to be part of the lighting or power circuit, and hence being usually subjected t0 a normal operating potential difference or Voltage of 110. These conductors are usually solid or single strand. To the extent that non-metallic sheathed conductor or cable has heretofore been employed in practice, the conductor or conductors thereof have embodied, usually as an initial layer of insulation, a layer of rubber or like'compound, vulcanized in the form of a jacket surrounding the conductor, but it has long been considered unsafe, in such prior practices, to employ a wall thickness for the rubber jacket less than a certain limiting value, due to various and numerous factors involving elements of construction, manufacture, installation, conditions of use, and the like. In the preferred form or forms of my invention, and in so far as certain features thereof are concerned, I preferably employ a rubber jacket, preferably extruded onto the conductor and then vulcanized in any usual or suitable way, as by the known process or apparatus of continuous extrusion and vulcanization, but I am enabled very materially and with safety to reduce the thickness of the wall of such a rubber jacket and thus also to reduce the amount of rubber needed.

Thus, referring to Figure 5, and since certain -of the elements applied to the two conductors I0 and I I are preferably the same and applied in the same manner, it Will suffice to describe these aspects of my invention only with respect to conductor I0 onto which is extruded a rubber jacket I2 and vulcanized; jacket I2 is preferably of lesser wall thickness than has heretofore been possible, for example, a reduction in Wall thickness on the order of 40%.

A Among the reasons why, in the processing or manufacture of cable or conductor of this general type according to prior constructions and methods, reduction of rubber Wall thickness was not carried out, is in the fact that the insulating materials superimposed upon the rubber, usually immediately afterivulcanizatlon, have been of a nature and have been applied'under such conditions of pressure or tension that harmful deformation of the rubber, usually still in a somewhat soft condition, would result. Also, as is usually the case, the conductor is of solid metal so that any bending or flexing thereof during various stages of processing would tend also to effect deformation or distortion of the rubber Jacket, and in various ways, such as in a di rection outwardly through the rubber or like compound of the jacket, due to the direct internal action thereon by the conductor itself.

Having applied the jacket I2 of rubber, or like compound, for example in the manner above ndicated, as above noted also, I apply thereto a coating, indicated at I3, of a suitable material or compound, preferably capable of being applied in liquid or semi-liquid form, but which, upon bcoming set, is dry, exible, and preferably also somewhat elastic, and has preferably also good or suitable adhesion to the rubber jacket I2. The material, compound, or composition, employed to form the coating or layer I3, may vary widely and preferably and illustratively' I employ a lacquer whose ingredients are suited vor selected, in a manner known in the art, according to the manner or "method of application thereof to the element l2 and to the ultimate characteristics, such as those above-mentioned, desired. Thus, in the numerous compositions of various ingredients are y,available for this purpose; such compositions are referred to, in certain of the claims hereof as being of the lacquer class. I preferably and illustratively employ a lacquer having for its base a. cellulose derivative, preferably cellulose nitrate, and having included therein a suitable solvent or solvents and a suitable plasticizer or plasticizers. The application of the coating material may be carried on in any suitable or known way and when the solvent or other volatile constituents (in the case of lacquers) are evaporated or driven off, the material becomes set with the desired degree of hardness and thickness of coating as well as sufficient flexibility and elasticity thereof to be somewhat yieldable and stretchable, thus to avoid cracking, chipping or cra-zing. The resultant coating I3, which may be of a thickness on the order of several thousandths of an inch, is also, in preferred form, quite smooth and slippery, its exposed surface being of low coeiiicient of friction in coaction with other material which I may use superimposed vupon or about the layer Y or coating I3.

Preferably, the material of the coating I3 is of the type, such as the above-mentioned lacquer,

that sets in response to the application thereto 10 iielcis of lacquers and liquefiable synthetics alone of Aheat or Whose rate of setting is increased in response to the application of heat; in such way, I prefer to apply the coating material to the rubber-jacketed conductor while the latter with its jacket retains or has a heat content derived from the step of vulcanization.

Thus, as diagrammatically shown in Figure l, I prefer to use a continuous vulcanizer I4 through which the rubber-jacketed conductor III-I2 is drawn at a suitable speed, a speed which may be on the order oi several hundred feet per minute; the vulcanizer I4 comprises a pipe-like chamber of suitable length charged or supplied with steam at suitable pressure and temperature so that the conductor emerges therefrom with its rubber jacket I2 practically or completely vulcanized;

any suitable form of continuous vulcanizer may be employed and, as is usual in practice, it is preferably associated directly with an extrusion head or machine which extrudes the rubber jacket onto the Wire.

Emerging from thevulcanizer I4, the still hot jacketed conductor, the temperature or heat content of which may at this stage be altered,if desired, by a suitable heat exchanger (not shown) passes through an applicator I5 in the form oi a suitable device or chamber containing the coating material, such as lacquer, supplied thereto as from a tank IE and provided with suitable means, such as a rubber element or elements, at its righthand or outlet end to regulate or nx the thickness of the coating with which the rubber-jacketed conductor emerges therefrom. The heat content of the jacket I2 or oi the wire I0 or of both heattreats or sets the thus applied coating I3, insuring also a good bond between it and the rubber to which, it will be noted, the coating material is applied while the rubber surface is still virgin and in eiect open-pored or in a condition analogous to porosity. g

The coating is strong, relatively tough, and affords mechanical protection and reinforcement to the rubber jacket I 2. Moreover, and preferably, I include in the compound of which the coating I3 is formed, such as lacquer, suitable coloring materialafpreferably in the form of pigments and, where a plural conductor cable is to be constructed, as the two-conductor cable of Figure 5, the pigment employed in the coating on rubber-jacketed conductor III is different from the pigment employed in that of rubber-jacketed conductor I I, thus to distinguish the several conductors in 'the cable.v selected according to existing color codes and thus, in a two-conductor structure like Figure, the coloring or pigmentation of the one coating may be gray and of the other may be black. In a structure like that of Figure 5 and for reasons later set forth, I prefer next to apply over the coating I3 a layer or coating of a suitable wax-like material; in Figure 5 that coating is' indicated at Il and it is preferably applied as a a step following the step of applyingV and setting the coating I3.

Thus, I may provide an applicator chamber I8 throughwhich the conductor ,structure passes and which contains a suitable wax-like material in heated and hence substantially` liquid form, thus coating the conductor element, any suitable means being provided, if desired, to determine, as by a yieldable wipe, or the-like, the thickness of the layer picked up by the conductor element as it passes through the bath in the applicator I8.

Since, in the preferred process, where the conductor continues to move at the substantial speed at which it is extruded and vulcanized, the conductor element emerges from the coating applicator I5 in a still heated condition even though some of its heat content has been dissipated in setting the coating I3, and. hence I prefer appropriately to regulate or interrelate the characteristics of the wax-like material and the temperature or heat content and speed of' the conductor element. Thus, for exfu may regulate the heat content of the r nf element by a. suitable heat exchanger i, shown) interposed between the applicators i5 and I8 and thus suit it to the characteristic of melting point and viscosity of the material in applicator I8, it being noted that whenf the conductor emerges from applicator I8, the wax-like material should set relatively quickly rather than be kept in such a state of fluidity by the heat content of the conductor element as to cause uneven distribution of the coating, particularly where the conductor element moves in a general horizontal direction.

Or, as in the preferred step, I may achieve such a suitable interrelation of factors by utilizing a wax or like compound that has a melting point suihcie'ntly high relative to the temperature or heat content of the moving conductor element that setting at the desired rate and even distribution or thickness of coating are achieved. Also and preferably I prefer to use a wax compound of appro; siate body; for example, I may employ a Wax loaded with zinc stearate, having a melting point on the order of 16o" F., somewhat higher than the temperature of the jacketed conductor element as it enters the applicator I8. The loaded wax has sufri- These pigments may bev and hence uniformity of thickness during and f after setting results.

The wax compound-in applicator I8 is prefer' ably circulated therethrough in heated and liquid condition by any suitable means, such as a pump 20, connected in series by suitable piping with'the applicator I8 anda tank 2| which is provided with any suitable heating means diagrammaticallyindicated at 22. f

If desired also setting of the wax coating, which may have a thickness on the order of 0.015 inch or cooling of the coated conductor element may be effected by a suitable heat exchange device 23.

Subsequent steps are effected at a lower rate of speed of movement of the conductor element and hence it is preferred now to reel up the conductor element -I2-I3-I`I and in this connection the cooling by heat exchanger 23 may be used to facilitate immediate reeling up.

'From such reels, the element is run off and during continuous movement thereof, in the pref ferred form of my method, I perform a succession of operations diagrammatically indicated in Figure 2, and of which the first comprises Winding about the element and hence onto the last-applied coating, in the above instance being the wax coating I1, a band or tape-like member 24. The latter is preferably of paper and of suitable thickness and width, illustratively a thickness of 0.0025 inch and a width of 1A" and it is wound helically preferably with a small overlap.

A ny suitable apparatus.diagrammatically indicated at 25 may be employed for thus Wrapping the member 24 as the conductor element continues to move in a direction toward the right as viewed in Figure 2; the speed of such movement may be on the order of 60 feet per minute. Leaving the wrapping machine 25, the conductor structure enters a suitable machine or apparatus Awhich applies to the structure and onto the last-applied layer of material, in the illustrative embodiment being the paper wrap 24, a continuous helix of a cord-like element 2'I wound at a pitch to leave a suitable spacing between successive turns somewhat analogous to a form of screw thread. Member 2l may be substantially round in cross-section and is preferably made of twisted paper, being thus a form of so-called paper cord. The pitch of winding may be such, illustratively, as to give a spacing on the order of Ps" from center to center of successive turns, thus forming a helical rib lengthwise of the structure and forming a helical space.

The rib 2T! may be made of relatively tough or strong construction and is preferably wound with sufficient tension or tautness as to cause each turn to resist shifting thereof relative to the underlying supporting core structure. The tenacious and relatively tough coating I3.of lacquer supplemented by. the paper or layer 24 forms a dependable foundationl for this helical rib 2l and the coating i3 in coaction with the covering 2d also protect the rubber jacket l2 against detrimental distortion or compression under the winding tension of the rib member 2l.

Continuing its movement toward the right, the structure, now with the helical rib 2l' about it, passes through an applicator apparatus, generally indicated by the reference character 23. and which, where the material to be next applied to the conductor structurt is a thermoplastic having preferred characteristics as later described, preferably takes the form shown in Figures 2, 3 and 4.

Thus, the apparatus 28 may comprise a tank 30 of suitable capacity and depth to contain the plastic material and provided with suitable means for insuring its application to the conductor structure. The latter may enter through a suitable bushing, or the like, 3| in one end wall of the tank 30 and pass through a suitable device 32 suitably relatedl to the opposite end wall. The device 32 preferably comprises an internally tapered tube-like element having a land or portion 32a at its exit or right-hand end (Figure 3) that is of uniform inside diameter somewhat less than the outside diameter of the helical rib 21; for example, if the outside diameter of the rib 21, in a structure utilizing No. 14 B & S gage wire for the conductors I0 and II is 0.18.7 inch, the inside diameter of the straight portion 32 is about 0.175 inch to 0.180 inch. With this preferred restricted exit throat in element 32, the conductor structure drawn therethrough is subjected to some degree of compression, particularly the turns of the helical rib 2l, and' other actions take place as later described.

To the left of the straight restricted portion 32, the internal diameter of the tube-like appli.

cator member'32 increases, preferably gradually, thus to form by its tapered internal walls guides for the plastic material, as is later described, and also guides to enter the turns of the helix 21 neatly and snug y into the restricted throat portion 32,

vMember 32 is mounted in any suitable manner to the end wall of the tank 30 and preferably detachably; thus, it may be externally threaded at its left-hand end and threaded into a collar or bushing 33 in the end Wall of the tank.

As the structure is drawn through the tank 3U, the plastic compound is picked up or applied to the rib structure and the latter with the compound enters the member 32 where the plastic material is indicated at 34. If desired, suitable means may be employed to insure the application of the material 34 to the moving conductor structure so that, for example, the application of the material does not have to depend too much upon the depth or amount of material in the tank. For

example, Imayemploysuitablerotarymeans, such as two spaced disk members 35, 33 (Figure 4) xed to a shaft'l driven by any suitable means, such as a motor 38, at a suitable speed and positioned relative to the bottom of the tank and the line or axis of movement of the conductor structure, somewhat as is indicated in Figure 2, so that at least portions of the rotary members 35 and 36 are always submerged and as they rotate they pick up and wipe onto the axially moving conductor structure suitable quantities of the plastic material 34.

The material 34 is preferably a thermo-plastic that is preferably quick-setting and, at temperatures usually encountered in the storage or i11- stallation or subsequent use of the finished cable construction, is non-migrating, relatively tough, yieldable or resilient; such temperatures might range from around 30 F. to 180 F. It preferably has other characteristics later pointed out.

For example, this composition or compound may comprise asphalt, bitumen, coal tar pitch, petroleum pitch, vegetable stearine pitch, animal stearine pitch, or like hydrocarbonaceous materials, preferably in suitable combination or combinations with suitable fillers, preferably inert mineral fillers, such as limestone, siliceous materials, like mica, fillers like talc, slate flour, asbestos, diatomaceous earths, and the like, Nylon or glass bcrflockings, etc.

An illustrative mixture or compound comprises by weight '15% of oxidized petroleum asphalt, 10% of slate our, 10% of Muscovite (flake) mica, and of Biotite mica. By way of further illustration another compound may .comprise by weight 50% of oxidized petroleum asphalt, 30% of inactive asphalt, 10% of Muscovite mica, and of fine divided asbestos. Another illustrative compound may comprise by Weight 70% of oxidized petroleum asphalt, 20% of slate flour and 10% of shredded mica.

Such amixture or compound is placed in the tank 30 (Figures 2 and 4) where it is preferably maintained in a suitable plastic or appropriately workable state preferably by heat, the tank 30 having associated with it any suitable heating means diagrammatically indicated at 40 and preferably also the tube-like member 32 is heated by any suitable means, such as a jacket or electric heating unit, or the like, diagrammatically indicated at 4I. The temperature at which the material is maintained preferably is related to the composition and hence characteristics of the thermo-plastic such as the reaction of the material of the helical rib 21 and the material of the wrap 24 and of other elements as is later pointed out. Thus, utilizing one of the above-mentioned illustrative cornpositions for the material 34,its temperature When in the tank Ill and while operated upon by the tubular member 32 is on the order of 300 F., it being noted that a slightly higher temperature is utilized where the percentage of filler is higher..

At such a temperature, the mass is suitably workable to take part in the actions of application about to be described, particularly at the speed of movement of the conductor structure or core, and moreover, does not detrimentally affect the materials, illustratively paper, of the helical rib 21 and the underlying wrap'24, nor does it affect,

, as by over-vulcanization, the rubber jacket I2.

The mass of material in the applicator tank 30,

though relatively dense or thick .and having subf stantial body, has portions of it transferred steadily onto the moving conductor or core structure, illustratively by the rotating applicator members and 36, where the conductor or core structure is not submerged in the plastic mass itself. This transfer or application may and frequently does take place with some non-uniformity in that over-excess of the plastic material may be thus transferred. But the core structure with the plastic material wiped or smeared or otherwise transferred onto it entersthe tapered interior of the device 32 (Figure 3), the tapered or progressively restricted walls thereof compaeting or forcing the material inwardly toward the axis of the conductor structure, particularly in the tapered region just to the left of the straight or land portion 32n above-described. As the material is thus pressed inwardly against and about thc structure, the relatively rigid and non-migrating rib structure 21 vano to move the compressed material along with thc conductor structure andto resist displacement or migration thereof relative to the moving conductor structure, at least so much of the surrounding mass as occupies the continuous helical acts like a continuous material 34 and'to related factors,

paper, takes place in a space formed by the helical rib 21. In effect, the helical rib, after the progressively restricted space within lthe member 32 packs the material against the base of this helical space, specifically against the wrap 24, forces or pulls the material along with the movement of the conductor-core structure and thus insures that that helical space is completely filled up.

As the parts enter and move through the straight or land portion 32a (Figure 3), a combined compressing, smoothing and wiping action takes place, preferably extent to somewhat compress or diminish the outside diameter of the helical rib 21. In the course of this action the material is compacted against the wrap 24, into any interstices that may exist in the rib structure 21 itself or between it and the wrap 24 and also against or onto or into the now somewhat flattened external face of the helical rib, emerging from the member 32 as a smooth cylindrical element substantially free from undulations and in appearance being of the color of the plastic material 34 itself, usually black, with the helical rib 21 hardly or not at all discernible due principally to the impregnation or covering (in an outer layer) of its material by and with the plastic itself. The above described actions are preferably facilitated by maintaining the temperature at a suitable level as by the heater 4I above described. The plastic material, filling the helical space, appears as a helically distributed band or ribbon of subtantial thickness, and as such an entity is indicated in Figure 5 by the reference character 42.

While the `iust described physical actions are taking place, other actions, in this preferred method and form of conductor structure, also take place. Thus, the material of the helical rib 21, preferably of twisted paper, becomes impregnated by the plastic material and a similar impregnation of the wrap 24, also preferably of direction from its external surface toward its internal surface. The above-described magnitude of temperature, it

' might be noted, does not detrimentally affect the paper of the just-mentioned elements.

The heat content of the plastic material, howover, and as soon as it is brought into thermal contact with the wrap 24, acts upon the Wax of the coating I1 which is heated suiliciently to impregnate the wrap 24 in a direction from its interior face or surface toward the outer face, and thus I may achieve impregnation of the wrap 24. Though thereby the-wax of the coating I1 may be somewhat diminished, there is enough wax left either in the coating or at the inner surface of the wrap 24 to function, in a sense like a lubricant, to insure ease of relative movement or slippage between the rubber-,jacketed structure or core and the wrap 24 and the parts that are external of the latter, though it will be understood that even in the complete absence of wax or of a waxy surfacing or impregnation of the wrap 24, the coating I3, preferably and illustratively of lacquer,I as above described, preferably has a smooth and slippery external surface which by itself facilitates such relative slippage or movetreat the material ment, as in bending or curving the vconductor structure either in subsequent stages of manufacture or thereafter. Also, it will be understood that if desired I may initially impregnato or suitable wax or by the use of a suitable saturant; in such case, I may or may not, as desired, -utilize a wax coating like coating I1. The structure also, as above noted, to an of the wrap 24 as by use of a' emerging from the applicator apparatus 28 (Figure 2) next has applied to it a covering preierably in the form of a band or tape-like element 43 preferably of paper, preferably employing any suitable form of tape wrapping machine,- as is diagrammatically indicated at 44 in AFigure 2. This paper tape 43 is preferably very thin and may be', for example, made of a rope-sulphite paper preferablyin a width commensurate with the width of the wrap 24 and applied preferably with a slight overlap, directly over the structure which, as above noted, and as indicated in Figures 2 and 3, presents an external substantially cylindrical surface of plastic material. Onto the latter the wrap 43 is applied and preferably before the mass has materially cooled oil and hence is still at the temperature at which it'leaves the applicator apparatus 28.

It will be understood, however, that I may, in any suitable manner, as by a heat exchanger (not shown) suit the temperature of the conductor or core structure, now embodying the thermo-plastic, to the desired conditions or circumstances of application of the wrap 43.

For example, I prefer to have the mass 42 (Figures 2 and 5) at a temperature such that there is adhesion or uniting between the tape 43 and the element 42 and preferably also imprega nation of the former by the latter, thus bringing about an action similar to that above described in connection with the tape or wrap 24,; where the temperature of the compound or material in the tank 30 is on the order of 300 F., the temperature, by Way of illustration, at the time of the application of the paper tape 43 may be somewhat less and hence on the order of 280 F.

Next I prefer to apply a coating of wax, indicated in Figure 5 at 45, and this application may be made in any suitable Way as the conductor or core construction continues to move along. Thus, the wax-like material employed may be similar to that used in` making the coating I1 and a similar form of apparatus may lbe employed, comprising, for example, an applicater chamber 46 (Figure 2) suitably supplied with the wax material at suitable temperature, as, for example, by'means of a pump 41 serially connected through suitable piping with the applicator 46 and with a tank '48, suitable heating means diagrammatically indicated at 50 being employed to keep the wax at a suitable temperature and a suitable degree of fluidity.

The wax compound may be of any suitable composition and may be loaded or otherwise compounded so that it will have suitable body so that, in relation to the heat content or temperature of the core or conductor structure onto which the wax coating is thus applied, the wax coating does not appreciably migrate or flow, thus to achieve uniformity of thickness during and aftersetting of the coating. But preferably coating 45 is relatively thin and in such case, such factors as body characteristic may be given less consideration.

Also, it will be understood that if desired I may initially impregnate or treat the material of the wrap or tape 43 as by use of a suitable wax or other suitable saturant; in such case I may or may not, as desired and depending upon cir-y cumstances, utilize a separate wax coating 45,

' it being noted that in such case the lheat content of the core structure, principally of the thermoplastic element 42, may take part in effecting a softening or melting of the saturant, where a.)

impregnated tape 43 with its saturant to its new helical condition and preferably also to effect a binding or adhesion between the material or element 42 and the band member 43.

Usually and preferably, the conductor structure is now reeled up and in this connection a suitable heat exchanger (not shown) if desired may be used to reduce the heat content of the structure, andfrom such reels the conductor element may now be further processed. Onto the core thus formed I now apply an outer covering element 5l (Figure 5) which is .preferably braided on, as by using cotton braid, but preferably, because of factors later mentioned, after first applying a suitable sheet material like paper, as indicated at 49, and Where the cable is to contain more than one conductor, illustratively the two conductors I0, of Figure 5, two such cores are encased side by side first in the sheet material 49 and then in the sleeve or tube-like braid formation 5|, the several cores being together run through a suitable machine'to apply first the sheet material 49 and then the braided covering 5| thereover. The element or material 49 may be applied in the form of a helix or wrap with a suitable overlap or it may extend longitudinally with its two longitudinal edge portions overlapped; crinkled kraft paper is preferably employed.

Where two such cores are thus assembled, there extend lengthwise of them two valleys formed by the side by side relationship of the two cores. Due to such features of construction and steps of operation as those above described, the outside diameters of these core structures are materially less than in structures heretofore employed, being each, in the illustrative embodiment, on the order of 0.180 inch in diameter, and these valleys are relatively small. Into preferably only one of them, such as the upper one as seen in the plan view of Figure 5, I run a cord element 52 which has substantial tensile strength for its small cross-section and which preferably also is nonporous or non-cellular and devoid of a wicking action; a suitable material for this paper is a cord or yarn made of woven or twisted synthetic fiber, preferably of synthetic or artificial silk,

wax-like material is used, to reaccommodate the -such as the kind known and available on the market by the trade name Nylon Even in the small cross-section appropriate to substantially fill in this small valley, Nylon yarn has a tensile strength on the order of pounds. It is run into the valley along with the two conductor cores, entering the machine that applies the paper sheath 49. In the other valley I prefer to employ a less expensive material and here a small-cross-sectioned yarn or cord or paper or jute 53, suitably impregnated or saturated, may be employed.

The braided covering 5| having been completed, I now subject it to suitable treatment in any suitable way, as by impregnation with suitable compounds or materials to give it the desired moisture-proof, fire-resistant, mold-resistant, and like characteristics. Thus, I may run the structure successively through saturating baths, for example, first througha tank containing the saturant that gives the braid covering 5| moistureproof qualities, then through a tank to give it flame-resistant and moisture-proof qualities, the sheath 49 acting as a barrier, dam or baille to block penetration of the braid-impregnating compound beyond the thickness of the braid itself or to block migration of the compound to or into other parts of the structure.

able or resilient at ordinary temperatures met Lastly, I prefer to apply, after drying or setting of the just-mentioned saturants, a final 1 coating, indicated at 54 in Figure 5, of a material preferably of the general characteristics and composition like that of which the coating i3 abovedescribed may be made, excepting that, where 1 employ a pigment or coloring element-as an ingredient, I prefer to use aluminum powder as a pigment. Thus, the coating 54 may be in the form of a pigment-carrying lacquer, preferably compounded to be quick-drying so as to facilitate air drying, though it will be understood that any other suitable means may be employed to effect relatively quick setting of the coating. Such a coating though applied in a relatively thin layer is resistant to and substantially impervious to acid-bearing fumes, such as those earlier mentioned above, it films over and thus covers or seals, with a relatively tough stretchable or resilien t skin interstices, and the like, that frequently occur in the braid structure and its saturants, it is resistant to or unaffected by high temperatures liable to be met with in practice and thus counteracts migration of fillers or saturants in the underlying braid, it being noted that frequently such llers or saturants have relatively low melting points or become flowable at relatively low temperatures. Thus, a clean non-tacky longlasting easily handled structure results. Such a. coating is impervious to moisture, is strongly resistant to weather, and the like, and adds protection against the effects of the sun. Also, the materials of which it is made or compounded lend themselves easily' and inexpensively to coloring as by pigments, and thus I am enabled to give the final cable structure a neat and attractive appearance in contrast to the crude appearance of structures heretofore employed, a factor-which has limited its scope of practical application. Also, such a iinal coating forms a good base for ordinary types of paints, and thus the cable structure may be painted, for example, when in' stalled.

',Ihe construction I am enabled to embody in materially smaller cross-section than the crosssection of cable conductors heretofore employed; for example, in the two-conductor structure of Figure 5, utilizing two No. 14 wires, the dimen-l sion along the major axis may be on the order of 1/8 less than the dimension along the minor axis .on the order of 114 less than the corre- Ali) with in installation and ldoes not migrate or ilow, even at the higher temperatures met with. Being present in the form of la helix in the helical space formed by the rib structure 21 and each turn thereof being Well backed up by the relatively tough or rigid adjacent turns of the rib structure 21, the structure offers dependable mechanical resistance to mechanical injury, such as penetration by nails, or the like, any tendency to displace the element 42 or part of it( see Figure 5) being strongly resistant byV the rib structure 21 and other elements that take part in coniining the material. The rib structure 21 itself offers strong resistance to mechanical injury and is well adapted to veering off instruments likea nail, an action in which the compound of the material 42 may take part or which it may assert of itself.

The pliancy or elasticity of the material of element 42 facilitates bending or curving of the structure and in its preferred form its penetration into and adhesion to its directly associated elements, such as the helical rib 21 insure against opening up or the creation of cracks or fissures at the longest radius of curvature when the -structure is bent and the rib structure 21 insures maintenance of concentricity or roundness of the built-up structure. Preferably, also,

sponding dimensions in prior commercial types oi l construction, Thus, also, substantial economies in shipping weight, less bulk and greater facility in handling and greater range of usefulness, such as in passage through smaller holes or entry into more restricted spaces, in course of installation, result. Also, less crowding of conductors in outlet boxes, and the like, may be had.

The construction is also less expensive and the method lends itself to commercial operation on a quantity production scale. For example, the application of the material 34 in Figures 2, 3 and 4 is simply and dependably carried on; the helical rib structure 21 in coaction with other elements insures proper application of the material and makes possible the employment of inexpensive compounds and compounds of low temperature characteristics. Thus, also, considerable loading of the compound, as by such fillers or loaders, preferably inorganic, as those mentioned above, with attendant advantages, may take place evengthough the compound may as a result be relatively stiif.

In the cable structure the element 42 is yield-v ease of bending or curving is contributed to by relative ease of sliding or slippage between the interior face of the wrap 24 and the element underneath it, such as the coating i3 which is pref-- erably slippery, as above-mentioned, or such as the wax coating I1; in such bending or curving, also, relative ease of slippage between the inside face of the element 49 and the elements contacting therewith, such as the paper wrap 43 or the wax coating 45, is preferably present.

Also, I achieve safety and facility of manipulation or handling in installation. The tensile strength of the element 52, even though of small cross-section, resists tensile stresses to which the cable structure may be subjected, as by pullingf and thus resists elongation of the copper conductors and accompanying reduction in crosssection thereof. Also, the tensile strength of element 52 makes it possible for it to function as a dependable rip cord for unsheathing the outer elements of the structure, as by causing the cord 52 to tear, cut or rip the coverings 49 and 5l, as when the ends of the cable structure are to be exposed in turn to be "stripped to expose the wires themselves.

In this latter connection, due to characteristics of the material of element 42 and coactions thereof with other elements, some of which are mentioned above. the relatively strong and tough` helical element 21 acts as a stripping element, `for its extreme end need onlybe grasped and pulled in the general direction of the axis of the conductor, resulting in a sort of unwinding action but accompanied by the removal, with the element 21 and as a unit therewith, of the inner wrap 24, the outer wrap 43, and the compound element 42, the adhesion of the latter to the former and to the helical element 21 causing them all to be removed cleanly, and at substantially the same speed or quickness with which the helical rib 21 itself could be disassembled by a `pull generally in the above-mentioned direction.` Thus, element 21 parts sheet elements 24 and 43 either at their overlaps or by tearing and parts the turns of helical mass 42; the coating i3, .when and where employed, becomes exposed and where it carries a coloring or pigment polarity or like identification of the individual conductor is at once present; the rubber jacket I2 is easily stripped off in known manner and thus the bared conductors are available for making electrical connection.

In installation high protection against moisture, fungi or mold, acid-bearing fumes or vapors, and like effects is achieved. Wicking action is dependably resisted and the small dimensions and compactness of construction with resultant greater ease and dependability of filling the valleys guard against the presence of hollow spaces along which infiltration of moisture or acid-bearing air or gases might otherwise take place. Wicking action by wayof such elements as members 24, 21 and 43, as to moisture, or the like, is well guarded against, even though these elements may be made of an organic material like paper, by the coverage or impregnation thereof, or both, by the compound or material of element 42, While the same or similar effects guard against movement of moisture, or the like, in a radial direction inwardly through these elements, the material of element 42 itself being impervious to moisture and', as above indicated, comprising also preferably inorganic elements and being inert. In effect, the structure also adequately and permanently encloses or seals the rubber or like material of the jacket I2 of the conductor or conductors against passage or infiltration of moisture, fumes, fungi, mold, or other deleterious elements or effects. If desired, also, rodent repellants in the form of suitable saturants or lingredients may be incorporated in the elements 24, 21 and 43 or compounded with the material of element 42.

The above-described construction and method lend themselves to modification or variation. Thus, for example, and returning to Figure 6, the material of element 42 above described may be interrelated with other elements, such as an underlying helical element 56 of fiber-like strands of glass, preferably of a diameter or degree of fineness just large or heavy enough to permit them to become interwoven, or intermingled, or

matted or felted together in a manner analogous to glass wool, preferably with a binding material, such as a phenolic condensation product. Element 56 occupies part of the depth-of the helical space between the helical rib element 21 and may be applied in any suitable manner, preferably by means of a separate carrier element, such as paper, which may comprise a paper wrap 24a to which the glass fiber element 56 adheres or is bound, as by the above-mentioned binding material. The rest of the depth of the helical space may be filled with a material like the material 34, above-described, and of which the abovementioned element 42 is made, being shown in Figure 6 at 42a. Depending upon its composition, the application of element 42u proceeds' preferably in the manner above described, as in connection with Figures 2, 3 and 4, and preferably under conditions such as cause it to be pressed into and impregnate such tape or paper elements with which it contacts and to become also adhered to the glass fiber element 56; or, to illustrate another form which the material 34 may take for making up a helical element of the general shape of element 42 of Figure 5 or for making up an element like element 42a of Figure 6 in association with a material like fiber glass, it may comprise suitably small particles of suitable material bound together and preferably also bound to the parts or surfaces of the conductor core structure with which it is in engagement, an illustrative material comprising verrniculites in suitably divided form, usually granular or flake-like, the abovementioned binding being achieved by a suitable binder which may take the form of a phenolic condensation product, any suitable non-.conductive plastic cement, such as rubber cements, latex, or the like. In its application, as by an apparatus like that indicated in Figure 3, the helical rib element 21 preferably takes part in insuring, in coaction with the interior faces of member 32, the application of the mass of vermiculite particles with their binder, much in the same manner as was described above in connection with Figure 3. Otherwise, the procedure and the lpreferred coacting elements of the construction are as those described in connection with Figure 5, it being noted that the mass of boundtogether vermiculite particles has pliancy and flexibility, individual particles stretching or expanding or contracting.

With a construction like that of Figure 6, stripping off, as by pulling upon the end of the helical element 21 at the end of the conductor structure may be effected with the facility described above in connection with Figure 5. strippi-ng and also certain of the earlier abovementioned advantages of 'my'invention may be achieved with a structure like that shown in Figure 7 where the helical space formed by the helical rib element 21 is occupied entirely bya material like the fiber glass element 5B above-.described, the binding element of which, or a suitable similar binder, preferably binding elements 24, 56, 43 together and to the helical rib element 21. Pulling the latter at its end thus strips off a composite but unitary helix made up of these elements, thus quickly exposing the underlying element or elements.

.Where a mass of particles like verrniculite is employed, the material of the particles is preferably inorganic and substantially inert chemically; where fiber-like material, like the glass fibers of element 56, is employed, the material thereof preferably has similar characteristics, and, moreover, both materials, being inorganic, do not encourage the formation or growth of mold. Fiber-like elements of mineral base, such as Nylon, may also be employed. In applying such materials, the application proceeds preferably with the accompaniment of heat which may be applied in any suitable manner to drive off I noisture that may be related to the materials as, for

example, in interstices between fiber-like elements or 'between particles and also where, as is preferred, an inorganic heat-responsive binderis employed. Thus, or in any other suitable manner, heat treatment may bring about such interactions as impregnation of the tape- like elements 24 and 43 and the rib structure 21 with wax-like material, such as the material of coating I1, or the saturant (where one is employed) in such elements as elements 24, 21 and 43, or a binding together, as mentioned above in connection with Figure 7, to facilitate stripping off of the various elements as a unitary helix, as is preferred.

Recurring to Figure l, subsequent to the step of applying the coating I3, as by the apparatus I5-I6, and just before completion of setting of the applied coating, particularly where it takes the form of a lacquer, I prefer to apply thereto a material comprising small particles or flakes, indicated at |38, preferably mica of suitable and preferably very small mesh; any suitable means (not shown) such as a head or chamber con- Such facility of a helical form, means binding said helical sneatntaining the material and through which the coated conductor core is drawn, may be used to make the application. The particles partially embed themselves inthe outermost portions of the coating, it being noted that in the preferred manner of applying a heat-responsive coatingv namely, to utilize the heat content of the rubber handling become necessary at `that stage of the preferred form of process.

.In the completed conductor structure, as in Figures 5, 6v and '7, these particles I3 toughen the coating and when made of mica contribute a factor of lubrication to still more facilitate ease of relative movement between the coated internal core structure and the parts overlying it, as when bending or curving the conductor structure. Such an external application of such particles does not detrimentally aiect color elements or pigmentation. of the coating material.

Thus, it will be seen that there has been provided in this invention a conductor construction and a method of processing the same in which the various objects hereinbefore noted together with many thoroughlyl practical advantages, are successfully achieved. It will be seen that I am enabled to combat effectively the various elements which in prior practice have been found to have detrimental effects upon materials as heretofore employed; thus, for example, entry of moisture, or the like, into the structure is counteracted in a dependable, inexpensive, compact and mechanically and electrically vefiicient structure, utilizing therein'preferably inorganic non-hygroscopic elements and reliably rendering non-hygroscopic such other elements as are for various other reasons of organic material, such as paper. It will be seen that the construction is well adapted to meet the varying conditions of hard practical use. a

As many possible embodiments may be made of the mechanical features of the above invention and as the art herein described might be ing means and said helical rib together and upon -both sides of the latter to form therewith a substantially continuous insulating and mechanically protective jacket of substantial thickness, and removable covering sheath means thereover, the tensile strength of said rib element being suiilcient, when said covering sheath means is removed and upon subsequent pulling the end of said helical rib element in the general direction of the axis, to break the bond between said helical sheathing means and said helical rib element on that side of the latter opposed to the direction of the coating, and thus faclliy latter given a helical form, with a varied in various parts, all without departing from the scope of the invention, it .is to be understoodA that all matter hereinabove set forth, or shown in the accompanying drawings is to be interpreted as illustrative and not ina limiting sense.

I claim:

1. An insulating conductor construction of the character described comprising a conductor core structure having thereabout a helical tape element, a rib element of substantial thickness -and ytensile strength and extending helically at substantial pitch` about said core structure and tape and whose side walls are denned by the sides vof adjacent turns of said rib element, pliant v stantial thickness and element, thereby providingl a'. helical space therei about of substantial radial dimension and whose bottom comprises portions of said tape `element of pull on the rib element and throughout as ,sheathing means as correspond to the axial length of said core structure -to be bared, said binding means having a strength normally to hold said helical sheathing means and helical rib element bound together on both flexing of the entire conductor construction and also bound together, as said rib element is pulled, on that side of the rib element in the direction of pulling of the latter, thereby to remove said helical sheathing means substantially as a unit with said rib element and to expose said core structure.

2. A conductor construction as claimed in claim `1 in which said helical sheathing means comprises a. mass of material that is pliant at the usual range of temperature of operation or installation of the conductor and which at higher temperatures has suilicient mobility to impregnate impregnatable fibrous elements, said tape element and said rib element being made of impregnatable fibrous material, said binding means comprising portions of said mass flowed under heat into said tape and rib elements.

3. A conductor construction Aas claimed in claim l in which said helical sheathing means comprises a mass of intermingled fibers of non-conductive material in said helical vspace and by the binder binding said fibers together, whereby upon pulling said rib element the helically shaped mass of boundtogether bers is removed turn by turn with said `rib element.

4. A conductor construction as claimed in claim 1 in which said helical sheathing means comprises at least two superimposed helical layers character described, in combination a conductor core structure comprising a conductor andv a. rubber Jacket, said core structure having thereabout a non-conductive sheet-like material overlying said rubber jacket, a rib element of subof a non-conductive material resistant to compression extending helically about said sheet-like material and forming an open winding to provide a helical space, the turns of said rib element having a tightness of winding appropriate to resist shift relative to one another and said sheet-like material coacting to 'protect the rubber of said jacket against the tightness of winding of said rib element, means comprising atough pliant non-,flowable-insulatlng mass compacted into said helical space, a nonconductive sheet material overlying said insulatsides of the latter during ,l

' axis of the structure, said casing backing up and reinforcing said last-mentioned sheet material in confining said pliant non-flowable helical mass whereby the insulating elements about the rubber jacket protect the latter mechanically against crushing, deformation, and the like and displacement, as by an implement, oi said mass in said helical space is resisted by its inherent characteristics and by its coniining elements including said helical rib element.

b'. An insulated conductor as claimed in claim in which said mass comprises a material that is pliant and non-flowable at operating and installation ranges of temperatures and that is relatively flowable and has adhesive qualities a't higher temperatures, said helical mass, said rib element, and said two sheet materials being bound together by the material of the mass itself under heat treatment at said higher temperatures.

7. An insulated conductor as .claimed in claim 5 in which the material of said mass in said helical space is non-hygroscopic, and at temperatures higher than operatingl or installation temperatures has characteristics'of mobility and adhesiveness, said helical least said rst-mentioned sheet material being substantially impregnated by material of said mass under initial conditions of suiiicient temperature to eiect impregnation and adhesion.

8. An insulated conductor as claimed in claim 5 in which there is interposed between the rubber jacket and said first-mentioned sheet material a tough, resilient stretchable coating of a material of the lacquer class, said coating being bound to the rubber jacket and reinforcing the latter mechanically against the winding pressure of said helical rib element.

9. An insulated conductor as claimed in claim 5 in which there is interposed between the rubber jacket and the first-mentioned sheet material a means acting to provide for relative ease of slippage, as during bending, between the jacket and said first-mentioned sheet material, thereby, during bending, to permit relative sellaccommodation, according to the radius oi' bending, between said conductor and rubber jacket as one unit and said mst-mentioned sheet material with said rib element, insulating mass and overlying sheet material as another unit.

10. An insulated conductor as claimed in claim 5 in which there is interposed between the rubber jacket and the first-mentioned sheet material a coating of a material of the lacquer class, said coating being bound to said rubber jacket and being pliant and stretchable therewith .to provide relative ease of slippage between the jacket and said rst-mentioned sheet material,

A thereby, during bending, to permit relative selfaccommodation, according to the radius of bending, between said conductor and rubber jacket as one unit and said first-mentioned sheet material with said rib element, insulating mass and overlying sheet material as another unit.

1`l. An insulated conductor as claimed in claim 5 in which there is interposed between rib element and aty the rubber jacket and the rst-mentoiled sheet material a coating of a material of the lacquer class, and having at its surface or projecting therefrom and substantially uniformly distributed small particles or iiakes of non-conductive materialI thereby, during bending, to permit relative self-accommodation, according to the radius of bending, between said conductor and rubber jacket as one unit and said firstmentioned sheet material with said rib element. insulating mass and overlying sheet vmaterial as I another unit.

least one valley having 12. An insulated plural-conductor construction of the character described comprising an outer tearable sheath or jacket encasing a plurality of conductor structures each comprising a conductor having an insulating and protecting sheathing means that comprises a rib element of substantial thickness and of a material resistant to compression and extending helically and forming an open winding to provide a helical space of a depth commensurate with the thickness of the rib element and insulating and protective means accommodated in said helical space, the rib elements of said conductor structures and their respective insulating and protective means of said helical spaces coacting to resist diminution of the spacing between the axes of said conductor structures within said outer sheath and the valleys formed along said plurality of conductor structures being lled with suitable means including a cord element in at substantial tensile strength, whereby it functions as a rip cord to rlp lengthwise said outer sheath to expose the c plurality of conductor structures, said rib eletive insulating and protective means, the conductors may be by the coloring or pigment means distinguished from one another.

14. In a method of sheathing and insulating an" electrical conductor, the steps which comprise forming a conductor core structure by applying a rubber jacket to a conductor and by applying over the rubber jacket a non-metallic material to give the rubber of the jacket ease oi slippage, applying a sheet-like material next to said last-mentioned material and about said core structure for'the reception thereon of subsequently applied insulating and sheathing elements and to carry the latter for relative ease of lslippage with respect to said rubber jacket, Winding helically about said sheet material a rib element of substantial thickness and of a masheet material a non-metallic casing to back up 2,251,262 and reinforce said last-mentioned sheet material to compression and at a long lay to provide a v helical space between adjacent turns and at sufficient tension so that the turns thereof resist displacement, compacting into said helical space and in heated condition a mass of insulating material that is pliant and non-ilowable at operating or installation ranges of temperature and that is relatively ilowable and has adhesive qualities when in heated condition, thereby to flow and compact said material into said helical space and to cause it to bind said sheet material and said rib element together, applying a sheet material thereover and while said mass in said helical space is still in heated condition, thereby to cause said second sheet material to become bound to said helical mass, and building thereover a non-metallic casing. y

16. In a method of sheathing andinsulating an electrical conductor, the steps which comprise forming a conductor core structure by applying a rubber jacket to a conductor, applying an impregnable sheet material externally of said core structure, winding thereover a rib element of substantial thickness and of a non-metallic material resistant to compression and at a long lay to provide a helical space between adjacent turns, compacting into said helical space and in heated condition a mass of insulating material that is pliant and non-ilowable at operating or installation temperatures and that is relatively ilowable when in heated condition'beyond said temperature ranges to thereby impregnate and bind said sheet material, applying thereover an impregnable sheet material under temperature conditions high enough to cause impregnation thereof by the material of said mass, and building thereover a non-metallic casing.

17. In a method of sheathing and insulating an electrical conductor, the steps which comprise forming a conductor core structure by applying a rubber jacket to a conductor, applying and binding to the rubber jacket a relatively thin tcugh'stretchable coating to reinforce the rubber of the jacket, winding helically thereabout a/rib element o! substantial thickness and of a nonmetallic material resistant to compression at a long lay to provide a helical space between adjacent turns and at sullicienttension so that the turns thereof resist displacement, compacting into the helical space. a pliant non-flowable insulating mass, and applying thereover non-metallic sheathing means to form a non-metallic casing to coact with said helical rib element in confining said insulating mass in said helical space.

1s. 1n a method of sheathing and insulating a conductor the steps which comprise vulcanizing a rubber jacket about a conductor, applying to the rubber jacket while still retaining heat from the step of vulcanizing a heat-responsive coating material that is set by the heat content of said jacket, winding thereabout a rib element helically at a long lay to provide a. helical space between adjacent turns, compacting into said helical space and in heated condition a protective insulating mediumthat is pliant at operating or installation temperatures and that is relatively nowable when in heated condition at temperatures insufficient to over-vulcanize the rubber of said jacket, and applying thereover non-metallic coniining and insulating casing means.

19. An insulated conductor construction of the character described, in combination, a conductor core structure comprising .a conductor and a rubber jacket, said core structure being enveloped by a built-up 7insulating and protective sheathing structure that comprises a rib element of substantial thickness and of a material resistant to compression extending helically about said core structure at a long lay to provide a helical space betweenA adjacent turns, with a mass of insulating material that is tough, pliant andnon-ilowable at operating and installation ranges of temperature and that has characteristics of mobility and adhesiveness at higher temperatures compacted into said helical space, there being interposed between said core structure and said insulating material a layer of non-conductive meterial adhesively bound to said mass of insulating material under initial conditions of suillcient temperature of the latter to effect adhesion be-` tween the two, said layer of non-conductive inaterial mechanically separating said insulating material from said core structure and thereby preventing the former from adhering to the latter and thereby permitting relative movement,

l as during bending, between said core structure and said insulating and protective sheathing structure. and an outer flexible non-metallic sheathing impregnated with moisture-proofing and rire-resistant saturants and having a sheet .material along its inner face to resist flow of said saturants inwardly from said outer sheathing, and a layer of non-conductive material covering over and bound to said mass of insulating material and preventing the latter from adhering to said sheet material and thereby permitting relative movement. as during bending,

between said outer sheathing and said insulating and protective sheathing structure.

20. An insulated conductor construction as claimed in claim 1 in which said helical tape element extends helically about said rcore structure at substantially lthe same pitch as said rib element, there being binding means binding said helical tape element to said helical sheathing means and' to said helical'rib element, whereby said helical tape element is removed with and as part of the unit` formed by said helical sheathing means and said rib element when the latter is A pulled.

21. An insulated conductor construction as claimed in claim 1 in which said helical tape element extends helically about said core structure at substantially the same pitch as said rib element, there being interposed between said removable covering sheathmeans andsaidhelical'sheathing means a tape element that extends helically about said helical sheathing means and said helical rib at substantially the pitch of the latter, there being binding means binding both of said helical tape elements to said helical sheathing `means and to said helical rib element, whereby both of said helical tape elements are removed with and as part of the-unit formed by said helical sheathing means and said rib element when the latter is pulled. l

22. In a method' of sheathing and insulating a conductor, the steps which comprise jacketing a conductor with insulating means that comprise rubber, thereby to form a conductor core strucf ture, winding helically about the latter an impregnable tape element, winding helically there about a rib element of substantial thickness and 5 of a non-metallic impregnable material resistant to compression and at a long lay to provide a helical space between adjacent turns and at suflicient tension so that the turns thereof resist displacement, drawing the resultant structure in 10 an axial direction and during its movement causing said helical rib element to pick up and' move with it a plastic material that is capable of im pregnating the materials or said tape element and of said rib element and that is pliant at con- 15 ductcr-operating temperatures, drawing the structure through a device having a restricted throat to compact the plastic material into the helical-space and press it against said tape element and said rib element to impregnate them 20 and to become bound thereto, and applying thereover flexible non-metallic sheathing means to confine said plastic pliant material in said helical Space.

23. In a method of sheathing and insulating a conductor, the steps which comprise jacketing a conductor with insulating means that comprise rubber, applying thereto a wax-like temperatureresponsive coating, applying thereover an impregnable sheet-like material, winding helically thereabout a rib element of substantial thickness and at a long lay to provide a helical space between adjacent turns, cornpacting into said helical space and in heated condition a mass of insulating material that is pliant and non-iiowable at operating or installation ranges of temperature and that is relatively ilowable when in heated condition to thereby cause said heated insulating material to impregnato said sheet material from theouter face of the latter and to become bound thereto and by its heat to aiiect said wax-like temperature-responsive coating material to impregnate said sheet material from the other face thereof,v and applying thereover exible nonmetallic sheathing means to confine said pliant insulating material in said helical space.

CHARLES W. ABBOTT.

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