US1994281A - Insulator - Google Patents

Description

March 12, 1935.

J. T. LUSIGNAN, JR

INSULATOR Filed Jan. 17, 1933 2 Sheets-Sheet 2 mv zyroze Jose 0f; TAM/900mb? A TTORNE)" Patented Mar. 12, 1935 UNITED STATES PATENT OFFICE INSULATOR Joseph T. Lusignan, Jr., Akron, Ohio, assignor to The Ohio'Brass Company, Mansfield, Ohio, a corporation of New Jersey Application January 17, 1933, Serial, No. 652,126

3 Claims.

This invention relates to electric insulators and particularly to high potential insulators for use under adverse atmospheric conditions, such as those encountered with fog, dust, smokeor other contaminating substances present in ,the

atmosphere.

One objector the invention is. to prevent -corona discharge and to provide an insulator which will operate satisfactorily under such adverse conditions.

Another object of the invention is to provide an insulator which shall be of improved construction and operation. V

Other objects and advantages appear from the following description.

The invention is exemplified by the combination and arrangement of parts shown in the accompanying drawings and described in the following specification, and it is more particularly 2o pointed out in the appended claims.

In the drawings-z Fig. 1 is an elevation with parts in section, showing one embodiment of the present inven Figs. 2 and 3 are fragmentary sections, each showing a slight modification of the invention.

Fig. 4 is a view similar to Fig. 1 showing the invention applied to another form of insulator.

In the form of the invention shown in Fig. 1, two porcelain bodies 10 and 11 are provided; the upper body 10 having downwardly extending skirts or petticoats 12, 13 and 14 which are intermeshed with upwardly extending petticoats l5 and 16 on the lower dielectric member 11. The two members 10 and 11 have the general form of suspension insulators heretofore used' be somewhat deeper to provide a greater over lap of these parts than would be provided by the ordinary form of suspension insulator. The length, as well as the spacing, of the skirts may of course be varied to suit various conditions. The dielectric members are provided with caps 17 and 18 which may be of the usual form; one of the caps being provided with a socket l9 and the other with a headed pin 20 to cooperate with the pin and socket respectively of the connected insulator units.

The two members 10 and 11 are connected to each other by a connecting bar or pin secured in the recesses of the respective insulators by cement 21. Any approved form of insulator pin may be used for this purpose. The connecting bar may be formed in two sections 22 and 23 or may be continuous, as desired. Where two sections are used, they may be joined together by threaded parts 24. A lock washer 25 is pref erably inserted between the parts to prevent accidental separation. If the supporting fittings for the insulators are arranged so as to prevent relative rotation of the parts, as where clevis and pin fittings are used, it will not be necessary to provide the lock washer 25 and the sections 22 and 23 may be loosely screwed together so that they can be easily separated. The divided connecting bar facilitates assembly of the insulator and also separation of the two dielectric members for more easy cleaning. The arrangement shown provides a smooth, outer porcelain surface which is easily cleaned by rain and wind, and an inner surface which is provided with petticoats affording an extended. sheltered leakage surface The spacing of the interfltted parts on one another should be such that suflicient distance exists between the petticoats at all points to prevent sparks or stream ers bridging across from one to the other under any surface conditions that may be encountered. The number and shape of the interspaced petticoats may be varied to secure the proper labyrinth of insulating air path for withstanding. the voltage duty on the unit. The shape of the outer rims of both porcelain members should be such that air currents and floating bodies are least liable to be drawn into the space between the two dielectric members.

The outer petticoat of the lower member may be provided with a lip or head 26, as shown in Fig. 2, to check the downward fiowof water over this portion and prevent its accumulation at the rim of the cap 18. However, where the lip 26 is omitted, as in Fig. 1, a more complete washing of the outer surface of the member 11 may be secured.

The connecting bar may be formed of metal or if an insulating material of suitable strength is available, it may be formed of such material. In some cases, wood or a phenolic condensation product, such as "Bakelite, may be used for this purpose. The use of an insulating connecting bar will provide a very favorable electrostatic field about the insulator. If metal is used for the connecting bar, care should be exercised in shaping the bar and the adjacent porcelain so as to reduce as far as possible the liability for the formation of corona. All of the metal parts and adjacent porcelain should be designed to minimize corona as much as possible, thereby reducing the danger of foreign deposit precipitation, radio interference, cor rosion of metal parts, etc.

It has been found that the formation of corona at the termination of the metal parts or at the surfaces of the cemented joints may be materially reduced or eliminated by coating the surface of the dielectric at this point with a conducting coating; the coating being arranged so that lines of force emanating fromits termination will extend through the dielectric material. A

; cated in the solid dielectric with little or no air thin strip of metal or a metallic coating on the porcelain and cement surface may be provided, as shown at 26 and 27 for this purpose. This will avoid arcing from the metal fitting or the edge of the cement at these points. It should be noted that the conducting coating is conductively connected with the metallic fitting. The member 27 is disposed in a depression below the it is fired, or it may be formed in the green piece- It is a simple operation to form a depression in the dielectric member 10, and such forming operation is much more economical than it would be to attempt to build up a projection to overlap the marginal portion of a coating on the surface of a dielectric member.

In Fig. 1 the unfired porcelain is undercut up to the side walls of the head. In some cases to facilitate assembly, it might be well to cut the groove some distance out from the head, as shown in Fig. 3. The metal 27 may then be carried out into the groove as shown.

The purpose of both of the above arrangements is to provide an electrode, the outer edge of which is below the surface of the porcelain, and in intimate contact with the porcelain dielectric; In that way the intense electrostatic field terminating at the edge of the electrode is.lo-

located so as to fail and involve corona discharges.

The outer edge of the metal surface should be carried out far enough to shield the metal member above so that discharges do not result in the air space below the latter.

Where a metal pin is used, the internal capacity of an insulator, as shown in Fig. 1, will be approximately half that of the ordinary suspension type insulator, and consequently the insulator unit will withstand a voltage approximately twice the voltage of a single suspension unit as heretofore used. Where a dielectric pin is used, the capacity will be still less and the voltage which the unit will withstand still higher. Because of this increased ability to withstand voltage, a single unit of the type shown may be sufficient in each suspension string to maintain sufiicient line insulation under all conditions. Of course, more units may be used in each string if found desirable.

It will be noted that the inner surfaces are inclined outwardly throughout the entire extent so that if water should collect on' the inside of the insulator, this may be drained off by whirling the insulator about its axis or by turning the insulator upon its side. However, the parts are so shaped that under usual conditions, water cannot reach the inside of the insulator. The outer flange '14 of the upper insulator overhangs and overlaps the outer periphery of the lower insulator so as effectively to exclude water from entering the space between the two insulator parts. In tunnels or other places where the insulator is protected from falling rain or snow, the relation of the parts may be reversed so that the lower member overlaps the upper.

In Fig. 4, the invention is shown as applied- In this figure the numerals 28 and 29 designate the porcelain members of a two-part insulator secured together by cement 30. The two parts are formed with petticoats or flanges having interspaced skirts 31, 32 and 33 on the member 28, and 34 and 35 on the member 29. These interspaced parts provide a labyrinthine passage or opening between the adjacent faces of the two dielectric members which insures an extended dry leakage path under all weather conditions. At the same time, the outer surfaces of the two members are exposed to the cleaning action of rain and wind. Flanges may be formed on a single piece insulator having interfitting projections similar to those shown in Fig. 4, but it is usually more economical to form the flanges on separate pieces which are secured together to form a twopart insulator as shown.

The head of the insulator in Fig. 4 may be provided with a conducting coating 36 which terminates at its outer edge beneath the general contour of the surface of the member 28, as in Fig. 1. This will form an electrode that will screen the tie wire or other form of fitting that may be attached to the insulator head.

I claim: p

1. An insulator comprising a dielectric member having a terminal portion for receiving a conductor, the surface of said dielectric member having a depression therein adjacent said terminal portion, and conducting material disposed in said depression and electrically connected with the conductor attached to said terminal portion the outer surface of the portion of said conducting material in said depression being below the surface of the portion of said dielectric member beyond said depression to prevent electrical discharge along the surface of said dielectric member.

2. The combination with an insulator having a terminal portion for receiving an element of conducting material, of means for preventing the formation of corona at the extremity of said element, said means comprising a coating of conducting material electrically connected with said element and extending beyond said element and having the extremity thereof disposed in a depression in the surface of said insulator so that the major portion of the lines of force emanating from said extremity will extend through the body of said insulator and not over the surface thereof and the upper surface of said coating immediately back of the terminal edge thereof being disposed in said depression below the surrounding surface of said insulator.

3. An insulator comprising a dielectric member having a boss portion, a cap, said boss portion being cemented in said cap and having a recess therein, a pin cemented in said recess, a flange on said dielectric member projecting radially therefrom adjacent the edge of said cap, said flange having a depression in its upper surface encircling said boss portion adjacent the lower edge of said cap, and a thin coating of conducting material disposed in said depression and electrically connected to said cap for directing electrostatic lines of force between said pin and cap through the material of said dielectric member, said depression having a shoulder at its outer edge projecting above the upper sur-' face of said conductor coating to prevent discharge from the upper surface of said conductor coating along lines of force extending radially therefrom.

JOSEPH T. LUSIGNAN, JR.

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