US1940511A - High voltage conductor - Google Patents

Description

Dec. 19, 1933. 'H D, RICE n 1,940,511

HIGH VOLTAGE CONDUCTOR Filed Jan. 14, 1929 1N VENTO/e Ha/roc D Race A TTORNEY Pafeied Dec. 19, 1933 PATENT oFFlc HIGH VOLTAGE CUNDUCTOR Harold D. Rice. Bristol, R. I., assigner to National IndiaRubber Company, Bristol, R.. I., a corporation of Rhode Island Application January 14, 1929, Serial No. 332,375

2 Claims.

This invention relates to high tension electric cables having a plurality of conductors.

It has been common practice heretofore to make high tension electrical cables by wrapping 5 the individual conductors of the cable with paper. The individual conductors are usually then assembled into a group and a packing of paper fillers folded and crushed between land about the wrapped conductors. A wrapping of fabric is placed about the assembly of wrapped conductors and paper fillers and a final multiple layer wrap of paper is placed over the fabric wrap. 'I'his assembly is then placed in a tank to which a vacuum is applied so as to draw out -the wraps of the cable. Insulating oil'pis then fed into the tank under pressure and allowed to act upon the cable over a period of several hours so as to thoroughly impregnate the cable to thereby increase the dielectric strength of the insulating material and to provide an improved -mechanical bond between the wraps of paper. The oil also serves to ll up the interstices of the cable so as to prevent the access of air thereto. The impregnated cable is finished by coating the same with a vsheath of` lead which serves to protect the cable against the' action of corrosive agents.

A cable built in the usual manner as above described necessarily has a considerable amount of insulating material which makes the diameter `of the cable large and increases the cost of the cable due to the amount of material used, especially the lead, the volume of which is very largely determined by the diameter of the cable. .Such a cable is costly due not only to the vlarge amount of material necessary but also to the increased number of operations in manufacturing, and furthermore is costly due to its weight, which makes more diicult the handling of the same. The process of making the above described cable which involves the steps of applying of vacuum to eliminate entrapped air and then impregnating the insulation with oil under pressure involves a -considerable period of time, usually several hours, and is expensive not only on account of the time involved but also because of the cost of the machinery necessary to carry out this operation as well as the labor V involved in the same.

It is the object ofthis invention to reduce the cost of manufacturing high tension electrical cables having a plurality of conductors by providing an insulating material having a higher l 5.dielectric strength and a higher mechanical the moisture and entrapped air contained within strength so that either the number of wraps thereof may be reduced or the thickness of the -for making my new cable which reduces 'the cost of manufacturing the same as compared with the cost of manufacturing electrical cables under the usual process above described and which' does not involve the use of the expensive machinery necessary to apply a vacuum to the cable and also to impregnate. the cable with oil 7g under pressure. A clear understanding of my invention may be had from the following detailed description and accompanying drawing in which the gure is a cross sectional view of my improved cable.

In the drawing the cable is shown to be made up of three electrical conductors 1 which may be made up of a plurality of strands, such as 37 strands in the particular embodiment herein dislclosed. However, the electrical conductors 1 may 85 be of a different number of strands or may be solid conductors of an equivalent carrying capacity of the 37 strands of .091 inch copper used in the embodiment of my invention herein disclosed.

About the electrical conductors 1 is wrapped 90 insulating material 2 which is composed of a latex paper. This latex paper is made by adding 10% of rubber in the form of latex to kraft and sulphite paper pulps. This paper pulp to which the latex has been added in beat and brushed for a longer period than usual in paper making. The pulp is then formed into paper'in the usual manner and results in a paper which is stronger, more dense, having a greater surface drag and greater elongation than the usual insulating paper. The paper used in making the particular embodiment herein disclosed is of the thicknesses of .004 inch and .005 inch and 3A inch and 1% inches respectively in width.r The strips of latex paper of .004 inch and LA; inch width are spirally wrapped aboutthe conductors 1 with the adjacent edges of the wraps in butt relation. Over each layer of the latex paper is applied a coating of insulating oil such as rosin oil or a mixture of hot petrolatum and rosin oil or any other 110 visis suitable insulating eil. The insulating oil may be applied either by spraying or brushing or dipping the wrapped conductors-into the oil or in any other suitable manner. Alternative layers of latex paper and insulating oil are applied until, in the embodiment herein disclosed, 63 wraps of paper have been applied about the conductors l. The final, sixty-fourth, wrap of latex paper is lapped one-quarter of an inch Yand a coating of oil applied over this flnal Wrap.

The multiple wrapped conductors, three in this instance, when brought together have an irregu- -lar outline and in order to further insulate the conductors and-also to build up the assembly into cylindrical form, a .packing 3 made up of fillers of latex paper is vprovided about and between the conductors. The latex paper used for the filler -in the particular embodiment herein disclosed consisted of latex paper of .004 inch and 3A inch Width which was folded and crushed into place about the conductors. However, a preferred form of my invention involves the use of latex paper having a thickness of .002.inch for fillers. These fillers are coated with insulating oil in the manner described above before being packed about the wrapped conductors. The assembly of wrapped conductors and packing is forced through a die and a wrap of fabric 4 is placed thereabout. This `wrap of fabric may be light weight cotton cloth 11/2 inches in-width which is overlapped 1/2 in the wrapping. About the fabric wrap is placed a multiple layer wrap of latex paper of .005 inch thickness and 11/2` in width, in the embodiment herein disclosed. Thirteen of these layers is a satisfactory number, the layers being overlapped 1/2" vin wrapping. As in wrapping the individual conductors, each layer of this final wrap of latex paper 5 is coated with insulating oil before the sucessive layer of paper is applied. A sheath of lead is applied about the latex paper 5 by extruding or any other suitable manner. The cable herein disclosed, made in accordance with my invention, requires the use of less material and is of a smaller diameter than the cables made heretofore due to the fact that whereas the usual thickness of paper used for wrapping individual conductors is .005 inch. I have found that latex Legami paper of .004 inch is equivalent thereto, 'and falso due to the fact that the final wrap of paper 5 is usually of .00'1 inch in thickness while by using latex paper I have found that paper of .005 inch is equivalent to the previously used thicker paper. Not only is the cost of the cable reduced by the reduction in the amount of material used, but its cost .is further reduced due to the fact that the .application of the insulating oil is carried out during the wrapping process thereby requiring less time, less machinery and fewer operators for performing the operation than is the case with the usual method.

While I have described one embodiment of my invention specifically and have given the sizes and the quantities of the'materials used, I do not intend to so limit my invention inasmuch as the proportions, sizes and quantitiesA of materials may be varied as will be obvious to one skilled in the art.

Having disclosed my invention, I now define the same by the following claims:

1. A high tension electrical cable composed of a plurality of conductors, a wrap of approximately 64 layers of latex paper of a thickness of approximately .004 inch about each conductor, a packing of folded and crushed latex paper of a thickness of approximately .002 inch between and about the wrapped conductors, wraps of fabric and of latex paper having a thickness of approximately .005 of an inch about the assembly of Wrapped conductors and packing, and a sheath of lead over the wraps of fabric and of latex paper.

2. A high tension electrical cable comprising a plurality of conductors, a wrap of approximately 64 layers of latex paper of a thickness of approximately .004 about each conductor, a packing of folded and crushed latex paper of a thickness ofapproximately .002" between and about the Wrapped conductors, an overall wrapping including latex paper having a thickness of approximately .005" about the assembly of wrapped conductors and packing, said wrapping and packing being impregnated with oil, and a sheath of lead over said overall wrapping.

HAROLD BRICE.

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