US2287947A - Weatherproof insulated electric wire - Google Patents

Description

June 30, 1942. R. w. sHoEMAKER WEATHERPROOF INSULATED ELECTRIC WIRE Filed July 24,4 1940 Y w /I/ wwe/2240# Patented June 30, 1942 WEATHERPROOF INSULATED ELECTRIC WIRE Richard W. Shoemaker, Woodbury, Conn., assignor to Chase Brass & Copper Co. Incorporated, Waterbury, Conn., a' corporation Application July 24, 1940, Serial No. 347,178

2 Claims.

The present invention relates to improvements in electric wires and more particularly to weatherproof insulated electric wires designed and adapted for use in exposed locations where the wire is subjected to weather.

One of the objects of the present invention is to provide a weatherproof insulated electric wire having superior resistance to the destructive effects of moisture, sun, ice, etc.

Another object of the present invention is to provide a superior weatherproof insulated electric wire having minimum weight for a given electroconductive capacity.

A further object of the present invention is to provide an electric wire of the character referred to, combining superior resistance to the destructive effects of weather with minimum cross-sectional area for a given electro-conductive capacity of its metallic core and maximum dielectric strength for its insulating covering.

With the above and other objects in view, as will appear to those skilled in the art from the present disclosure, this invention includes all features in the said disclosure which are novel over the prior art and which are not claimed in any separate application.

In the accompanying drawing, in which certain modes of carrying out the present invention are shown for illustrative purposes:

Fig. 1 is a broken view partly in elevation and partly in longitudinal section of one form of Weatherproof insulated electric wire embodying the present invention;

Fig. 2 is a transverse sectional view taken on the line 2-2 of Fig. 1;

Fig. 3 is a broken view of the same Ygeneral character as Fig. 1, but showing another form of Weatherproof insulated electric Wire embodying the present invention; and

Fig. 4 is a transverse sectional view taken on the line 4-4 of Fig. 3.

The structure of Figs. 1 and 2 The so-called two wire service cable illustrated in Figs. 1 and 2 includes a central mainwire or conductor I formed of copper or other suitable electro-conductive metal and constituting in normal expected service what may be characterized as the hot leg of a circuit. The central main-wire III has extruded or otherwise suitably applied to it a. continuous coating of insulation II formed predominantly of ethyl cellulose, as will be more fully hereinafter described. Surto, is a reinforcing braid l2 formed of cotton or other suitable textile material.

Surrounding the braid I2 is an annular series of conducting-strands I3 formed of copper or other suitable electro-conductive metal and jointly constituting what is commonly referred to as a cold leg of an electric circuit in which the structure may be employed. The conducting strands I3 extend generally longitudinally of the structure but on a relatively-slight helix, as is clearly indicated in the drawing, and it is preferred that the combined cross-sectional areas of the entire group of conducting-strands I3 be equal.to the cross-sectional area of the central main-wire I0 when both the latter and the said group of conducting-strands are all formed of the same material. Other relationships of relative conductivity may exist as between conducting-strands I3 on the one hand and the main wire I0 on the other hand.

Over the group of conducting strands I3 is applied an outer braided cover I4 formed of cotton or other suitable textile material. Over the outer braided cover I4 just referred to, and impregnated thereinto, is an outer weather-prooiing and insulating coating I5 indicated by stippling in the drawing. The weatherproof-lng coating permeates into the material of the outer braided cover I4 as well as into the interstices between the threads thereof and also into the spaces between the group of conducting strands I3 and under some circumstances into the inner braided cover I2.

The extruded insulation I I is preferably entirely or substantially entirely of ethyl cellulose, and in any event the said insulation should be dominantly of ethyl cellulose. By way of example the following have been found satisfactory and possess superior attributes both as to weather resistance and dielectric strength:

A. 90% ethyl cellulose and 10% nujol (plasticizer) plus solvent 2B. 90% ethyl cellulose, 9% dibutyl phthalate and l% Japan wax; plus solvent C. 88% ethyl cellulose and 12% asphaltum; plus solvent.

The insulation II which may be conveniently applied by extrusion or, if desired, by wrapping a tape of the material around the central mainwire I0, is effective in a relatively-thin layer as an insulating medium and withstands to a remarkable degree and over long periods of time the deleterious eilects of oxygen and ozone. Furrounding the tubular insulation II Just referred thermore, the insulation II when composed dominantly of ethyl cellulose has no observable chemical reaction with the metal of the central mainwire I0, so that it becomes unnecessary to tin the said central main-wire I to guard against disintegration of either the insulation or the said wire itself by chemical action. Furthermore, it has been found that an insulation such as II may be relatively thin without depriving it of full effectiveness so that the overall dimensions of the weatherproof insulated wire may be greatly reduced. This latter characteristic not only results in economy in storage space and materials, but also minimizes weight and the effects of ice in weighting down the wire in service.

The outer coating I5 is preferably formed of a mixture of ethyl cellulose and asphaltum or coal tar of which the following mixtures may be mentioned by way of example:

methacrylate resin; plus solvent.

The inclusion of ethyl cellulose in asphaltum or coal tar increases the flexibility of the weatherproong coating I5 at even extremely low temperatures to thus avoid one of the maior defects in asphaltum or coal tar insulated compounds which are apt to crack and disintegrate under the combined action of wind and low temperatures. Furthermore, the inclusion of ethyl cellulose with the asphaltum or coal tar effectively guards the tendency of the same to drip or runin extremely hot weather and increases the over-all insulating properties of the mixture.

It is to be also noted that by employing an inner insulation such as II dominantly of ethyl cellulose, it is possible to employ a low-cost outer coating dominantly of asphaltum or coal tarI without harmful interaction and with, a high degree of mutual adhesion.

The structure of Figs. 3 and 4 In Figs.v 3 and 4 is shown a lso-called three wire service cable embodying the present invention. The saidI cable is of the so-called three wire type and comprises two main-wires I6 and I'I arranged side by side and each designed and adapted to constitute a so-called hot leg of a circuit. Each of the main-wires I6 and I1 is provided with a tubular coating of insulation I8,

which may be characterized as an inner insulation inasmuch as it is within an outer insulation to be later described. The said inner insulations Iii-I8 are composed of compounds which are entirely or dominantly of Aethyl] cellulose such, for instance, as the compounds described in connection with the inner insulation II of the structure of Figs. 1 and 2. v

Each ofthe tubular insulations IS-I is preferably surrounded by an inner braided cover I9, each of which may be treated or impregnated with an insulating compound such as has been described in connection with the coating I5, prior to or after the application of the remaining features of the structure.

Arranged around the exterior of the two inner braided covers I9--I9 is an annular series of conducting-strands 20 formed of copper or other suitable conducting material and having a joint conductivity preferably equal to the joint conductivity of the main-wires I6 and I1. though 75 of the service cable on a slight helix so as to permit the ready reeling o f the structure without injury.

Extending over the conducting-strands 20 and enclosing the same, as well as enclosing the elements I6, Il, |8--I8 and I9--I9, is an outer braided cover 2| formed of cotton or other suitable textile material.

The outer braided cover is preferably both coated and impregnated with a suitable insulating and Waterproofing coating 22 (represented by stippling in the drawing), which is preferably applied hot so as to penetrate into the material of the outer braided cover 2| as well as into the interstices between the threads thereof and between the interstices between the 'conductingstrands 2U. .If the inner braided covers IS--IQ have not been .previously treated with an insulating compound, it is preferable to force the material of the weather` proofing coating 22 into the structure as far as and into the said braided covers I S-IQ.

The material used for the weatherproong coating 22 may be of any suitable material such as asphaltum or coal tar but preferably, andwith great advantage, a compound of ethyl cellulose and asphaltum is employed, with the asphaltum or its equivalent, in this instance, dominating over the ethyl cellulose content, as hasbeen pointed out in connection with the coating I5 of the structure of Figs. l and 2.

'I'he invention may be carried out in other specific ways than those herein set forth without departing from the spirit and essential characteristics of the invention, and the present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range of the'appended claims are intended to be embraced therein.

I claim:

l. An outdoor weatherproof insulated electric wire for use in exposed locations where the Wire is subjected -to weather and including in combination: ametallic wire; a seamless insulating coating extruded into surrounding relation with the said metallic wire and having a major portion of said extruded coating of ethyl cellulose and a minor portion of asphaltum; a covering of textile material surrounding the said seamless insulating coating; and a weatherproong coating surrounding the said covering of textile material and containing a major portion of asphaltum and a minor portion of ethyl cellulose.

2. An outdoor weatherproof insulated electric wire for use in exposed locations where the wire is subjected to weather and including in combination: a metallic wire; a seamless inner insulating coating extruded into surrounding relation with the said metallic wire and having a major portion of said extruded coating of ethyl cellulose and a minor portion of asphaltum; an inner covering of textile material surrounding the said extruded coating; a plurality of conducting strands surrounding the said inner covering; an outer covering of textile material surrounding the said plurality of conducting strands; and an outer weatherprooiing coating

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