US2033790A - Cable - Google Patents

Description

Marh1o,1936. R. A. SCHATZL v2,033790 CABLE Filed June 18, 1930 @Naz/crm 2 /0 FF/A/E j ATTORNEYs Patented Mar. 10, 1936 UNITED STATES PATENT oFFlcE CABLE Application June 18, 1930, Serial No. 461,885

13 Claims.

The present invention relates to improvements in insulated electrical conductors and to methods of making the same.

In the distribution of electrical energy in ex-v posed positions, as by wires carried by poles f through trees and the like, a type of wire is used which is known as tree wire. Experience has shown that the present form of such wire now in general use is not Wholly satisfactory.

l0 For example, the constant abrasion or chafing of the insulation of the Wire incident to contact with branches of treesjcauses the rapid deterioration thereof and this condition is accentuated by reason of the exposure to adverse atmos- 15 pheric conditions, such as moisture, heat and cold.

Among the objects of the invention, therefore, is the provision of improved insulation which meets these conditions, as well as others set forth 20 in the following specification. At the same time, the invention provides an improved method of making such an insulated conductor. It is understood that while this invention has been developed for use in connection with tree wire, it

25 readily lends itself to a variety of other applications, as will be apparent to those skilled in the art. Other objects of the invention will be apparent from the ,following specication, wherein a pre-` sively removed to illustrate the entire construction and assembly thereof.

Referring to the particular embodiment of the invention shown in the drawing, the complete 40 structure is built up on a metallic conductor l which is conveniently surrounded by an insulating covering 2. 'I'his covering is preferably formed Wholly or in large part of vulcanizable material which includes rubber, a vulcanizing 45 agent, such, for example, as sulphur, and possibly an accelerator. The covering 2 is conveniently applied in any suitable manner, as by socalled strip application 0r by passing the conductor I through a tubing machine wherein the 50 covering material is extruded on the metallic conductor.

The covered conductor is now passed directly through vulcanizing apparatus of suitable design, wherein it is subjected to a predetermined 55 vulcanizing heat. The movement of the covered conductor through this vulcanizing apparatus is so timed that as it passes therefrom vulcaniZation is either fully completed or only partially, as desired. Preferably, there is only partial vulcanization of the covering 2 in this apparatus, for reasons as will presently appear. It is noted that the extent of vulcanization may also be controlled by varying the amount of the sulphur or the accelerator used.

Conveniently, the covered conductor is now provided with an inner wrapping 3 of protective material. This may take the form of a strip or tape of rubber impregnated or coated brous material. A braid 4 is next fabricated over the rubberized tape covering 3. This braid is preferably relatively close and formed of cotton or sisal. The braid is rendered moisture-resistant by a suitable saturant, such as an asphalt compound.

Preferably the next step in the production of the insulated conductor comprises the formation of a protective armor 5, which is characterized, among other things, by its resistance to moisture and especially abrasion, such as is caused, for example, by the constant rubbing or chang of tree branches. One convenient method of forming this protective armor involves, first, the impregnation of relatively heavy, brous strip materia] with a synthetic resin varnish, such as phenol-formaldehyde resin base varnish. In practice the coils of bre strip are immersed in an impregnating bath of this varnish for, approximately, 48 hours. 'I'he impregnation period may, of course, be decreased if vacuum and pressure impregnation methods are used. The strips are then wound on spools, passing during this operation through wiping means designed to assure an even and smooth coating of the varnish over the entire surface of the strips.

Next, ,one or more of the strips are wound 4o spirally about the conductor. In the present in'- stance, the winding is directly over the braid I. The spiral wrapping is now provided with a surface coating 6 of the varnish, following which the covered conductor is permitted to remain undisturbed for a period of, say, 24 hours, during which time the solvent in the varnish evaporates and the surface coating 6 sets. This may be expedited by subjecting the coating 6 to a current of air, or by passing the conductor through an oven similar to that used in producing enamelled Wire.

The next step in the formation of the protective armor 5 comprises the baking of the conductor thus constructed until the strip wrapping has been converted into a hard, tough material which is resistant to moisture and which has anexceedingly high abrasionvresistance. In practice, satisfactory results have been obtained with a baking temperature of, approximately, 250 F. maintained for a period of say, v4 hours.

The baking operation, in addition to causing` the conversion of the brous wrapping into a tough, horn-like armor, causes the further vulcanization of the semi-vulcanized covering 2. Inasmuch as the baking temperature is considerably lower` than the usual vulcanizing temperature, this baking operation makes possible a very accurate control of the extent of vulcanization of the covering 2.

Conveniently, the tough, waterandt abrasionresistant armor 5 may be next covered with a coating 'l of caulking putty. This putty is preferably formed of a base of a fatty acid pitch, such as s'tearin pitch, and a mineral ller, such as asbestine (magnesium silicate), as set forth in the copending application of Frank Potter, Serial No. 251,767, led February 4, 1928 and patented April 18, 1933, No. 1,904,527. The asbestine, which is ina nely divided state, is added to the pitch in the amount required to give the desired consistency, which, preferably, at normal atmospheric temperatures, is about like glazing putty, and at 300 F. about like cold molasses. The amount of asbestine added varies with the consistency of the pitch but it is between 10% and 30% of the whole. If a puttyof higher Aviscosity is desired, bre asbestos may also be added with the asbestine as a ller. Other mineral fillers, such as alumina, ground quartz, mica or magnesium oxide may be substituted for the magnesium silicate if desired.

The resulting compound is extremely resistant to heat and to oxidation, inasmuch as each Aindividual substanceis almost completely oxidized before being combined. Moreover, this oxidationand moisture-resistant putty does not become brittle in cold weather, nor unduly soft in hot weather. It is also noted that since the putty maintains its uidity, it follows that it tends to ow toward and heal or seal any bruise or rupture which may later be made to the adjacent portions of the insulated conductor.

Conveniently, a braid 8 is next applied over the putty coating 1. This braid, which is relatively close and formed of cotton threads, is conveniently saturated with a suitable waterproong compound which may include asphalt.

Preferably, the outer braid 8 is now covered with a tough, skin-like wrapper 9, which may take the form of a coating of paint. One satisfactory paint, which is disclosed in the aforesaid application, is formed of a metallic oxide, such, for example, as red iron oxideflitharge, alumina, magnesium oxide, etc. This metallic oxide is mixed with a specially prepared oxidizable oil which may include boiled linseed oil, partially polymerized China-wood oil, stearic acid and zinc resinate.

This paint, when dry, provides a tough, waterproof skin, which is effective to prevent migration of the saturant used in the outer braid 8. The paint also protects this braid from the deteriorating effect of the ultra-violet rays; and the germicide, which is contained in the paint, resists bacterial growth, especially in the braid. 3. Weather conditions over a long period of time have substantially no effect on the paint, and it is especially resistant to acids and alkalis such as are frequently found in the atmosphere. The

paint further aiords the insulation protection against attacks of Ainsects and the like. If desired, the finished conductor may be provided with a coating I0 of paraffin.

Although only one embodiment of the invention-has been shown and described herein, it will be understood that the invention may be variously modified and embodied within the scope of the subjoined claims.

I claim: V

1. 'I'he method of covering an insulated conductor with a tough moistureand abrasion-resistant armor which comprises applying to an insulated conductor an overlying layer of material impregnated with varnish, applying a coating of varnish to the material on the conductor, and baking said coated material to form a hard protective covering for the conductor insulation.

2. The method of covering an insulated conductor with a tough moistureand abrasion-resistant armor which comprises applying to an insulated conductor a material impregnated with varnish, applying a surface coating of varnish to said material, subjecting said surface coating to a current of air and baking the whole to form a hard protective covering for the conductor insulation. I

3. -The method which comprises impregnating insulating material with a synthetic resin varnish, wrapping said material around a conductor,

sitioning around said conductor a fibrous covering impregnated with a varnish, and subjecting both coverings to heat so as to vulcanize further said insulating covering and bake said varnish to produce a tough abrasion-resistant armor.

5. The method which comprises semi-vulcanizing an insulating covering material for a conductor, positioning around said conductor an additional covering provided with a synthetic resin varnish, and baking the whole so as to vulcanize further said insulating material and render said additional covering tough and abrasion-resistant.

6. The step in the method of manufacturing an insulated conductor having a vulcanizable covering and a fibrous jacket provided with a varnish, Wghich comprises simultaneously vulcanizing said covering and baking said varnish.

7. The steps in the method of manufacturing an insulated conductor having a vulcanizable insulating jacket and an overlying protective covering, which comprises positioning about said insulated conductor a brous jacket provided with a varnish, simultaneously vulcanizing said vulcanizable covering and baking said varnish, and applying a coating of an oxidized, moisture-resistant compound over said brous jacket.

8. The method of manufacturing an'insulated conductor which comprises forming a semi-vulcanized covering about the conductor, forming a tough, moistureand abrasion-resistant baked armor about said conductor applying a coating of a migratory, oxidized, moisture-resistant compound, and applying a paint to form a tough, skin-like wrapper for the insulated conductor.

9. An insulated conductor comprising in combination a metallic conductor, a covering of plastic' insulating material, a brous strip wrapping, a fibrous braid treated with a compound mak- Vinsulated conductor, and a second brous braid treated with a waterproofing compound.

10. An insulated conductor comprising incom- .bination a metallic conductona covering oi plastic insulating material, a relativelyv thin protective layer of brous material overlying the plastic insulating material, and a tough, moisture and Y abrasion resistant armor comprising a helical wrapping of brous material saturated and coated with a varnish which has been baked after application to the insulated conductor.

11. An insulated conductor comprising in combination a metallic conductor, a covering of plastic insulating material, a brous strip wrapping, a tough, abrasion resistant, non-metallic armor comprising a fibrous layer iilled with a varnish which has been baked` after application to the insulated conductor, and a iibrous braid treated vwith a waterproong compound.

12. 'Ihe method of manufacturing an insulated conductor which comprises forming a semi-vulcanized insulating covering about the conductor. forming a protective covering about the insulated conductor, completing the vulcanization of the insulating covering and simultaneously baking the protective covering to transform it into a tough, moisture and abrasion-resistant armor about said conductor, and applying a paint to form a tough skin-like wrapper for the insulated conductor.

13. An article of manufacture comprising in combination an electrical conductor, an enveloping wall oi.' plastic insulating material, a tough moistureand abrasion-resistant armor enclosing ,thel insulated conductor, said armor cornprising a heavy, fibrous layer lled with a varnish which has been baked after application to the insulated conductor, and an outer braided Jacket. 20`

RUDOLPH A.

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