US2135362A - Insulator - Google Patents

Description

J. L]. TAYLOR Nov. 1, 1938.

INSULATOR Filed Oct. 2'7, 1937 I INVENTOR John J. 7&r /0r' BY Patented Nov. 1, 1938 UNITED STATES PATENT OFFICE IN SULATOR Application October 27, 1937, Serial No. 171,285

4 Claims.

This invention relates to high potential electrical insulators and particularly to insulators for use under adverse atmospheric conditions, such as are found in regions where heavy fogs occur or where the atmosphere is apt to be laden with dust or other foreign material.

One object of the invention is to provide an insulator which will operate effectively under adverse atmospheric conditions, and at the same time will not interfere with radio communication.

A further object of the invention is to provide a device of the class named which shall be of improved construction and operation.

Other objects and advantages will appear from the following description.

The invention is exemplified by the combination and arrangement of parts shown in the accompanying drawing and described in the fol- 20 lowing specification, and it is more particularly pointed out in the appended claims.

In the drawing, the figure is an elevation with parts in section, showing one unit of an insulator string and a fragmentary portion of an attached unit, the unit shown illustrating one form of the present invention.

I have discovered that the operation of a high voltage insulator under adverse atmospheric conditions depends on several different charac- 30 teristics of the insulator and that to get the most effective results, these characteristics must be adapted not only in themselves to operate under the adverse conditions, but must be correlated to one another in such a way that they will cooperate effectively under these conditions. A high surface resistance, a long leakage path, petticoats arranged for effective cleaning by falling rain, control of the dielectric field so as not to produce undue stress at points where electrical discharges are apt to occur, string length efficiency, and ruggedness of construction, all have to be taken into consideration, but in thedesign of an insulator for regions infected with fog or other contamination, the insulator must be so shaped and proportioned that its various physical characteristics are so correlated that each of the desirable characteristics will have due consideration.

In the form of the invention shown in the drawing, it has been found that the arrangement and proportions of the parts are so correlated as to provide an insulator in which the characteristics referred to above cooperate to 55v maintain high insulation during adverse condition's, and at the same time, suppress or eliminate radio interference.

'In the drawing, the numeral l0 designates a dielectric member made of porcelain or other suitable insulating material having a suspension cap ll secured thereto by cement l2 and a pin l3 secured by cement 14 in the pin opening in the dielectric member. One detrimental feature of the action of fog upon insulators heretofore has been the corrosion of the'metal parts adjacent the exposed edge of the cement about the pin. This corrosion in time has produced pressure at the surface of the cement, which pressure, added to the stresses present in the insulator, has in some cases resulted in breaking the porcelain. In order to minimize this effect, the surface level of the cement in the present invention is arranged at a point well within the pin opening as shown at l5. This places the cement surface in a protected position so that the metal parts adjacent thereto are protected from the action of the weather, and at the same time, brings the surface near the lower edge of the cap where the stress produced by any corrosion is counteracted by the reinforcement provided by the cap. This proximity of the cement surface to the lower edge of the cap, however, places the surface in a region of relatively high electrostatic stress, and one in which the direction of some of the electrostatic lines of force that extend in an arc from the rim of the cap I2 would, at their ends adjacent the pin, extend in the general direction along the surface of the dielectric member. This condition would of itself tend to produce discharge from the lower edge of the cement. To overcome this tendency, the porcelain has been continued downwardly by a ring or boss. l6 considerably increasing the length of the pin hole and the inner surface of the pin hole has been metallized as indicated at H, the metal coating extending to a point #8 above the lower surface level of the cement, and to a point I9 adjacent the mouth of the pin hole opening. This conducting surface prevents any tendency for the electrostatic streamers to enter the air at the point I5, and brings the termination of the conducting member to a pointwell below the lower edge of the cap II, where the field is weaker and where the electrostatic lines of force at the termination of the conductor are directed into the porcelain rather than along the surface of the porcelain into air. Since discharge from the terminal point of the conductor tends to follow the direction of the electrostatic lines of force, and since discharge streamers cannot penetrate the porcelain, the tendency to discharge at the termination of the conducting material comprising the cement l4 and the metal coating I! is practically eliminated.

The dielectric member 'is provided with the usual radially extending flange 20, the upper surface of which is exposed to falling rain, so that any accumulated dust is washed away. Extending downwardly from the lower surface of the flange 2D is a petticoat 2| having its lower portion flared outwardly as shown at 22, and having an outwardly and downwardly flared flange 23 about midway of the distance between the upper flange 20 and the lower flange 22. The outer edges of the flanges 20, 22 and 23 are staggered relative to one another, so that although the upper surfaces of these flanges are subject to washing by falling rain, drip water from their edges will be broken up so as not to produce a continuous discharge path over the outer surface of the dielectric member. The arrangement provides a long leakage path which is exposed to washing by falling rain, and yet one which avoids the danger of short-circuiting by drip water.

It should be noted that the petticoat 2| is spaced inwardly from the outer edge of the flange 29 so that the peripheral extent of the leakage path is kept small. Of course, the resistance of the leakage path over the dielectric depends not only upon the length of the path, but upon its peripheral extent and the smaller the periphery, the higher will be the resistance since the resistance of the path is inversely proportional to its width and directly proportional to its length. The shape and position of the petticoat 2! provides suflicient clearance for connecting the pin [3 to the cap ll of the next lower unit of the string, even with a pin and clevis connection, and at the same time, provides a much higher resistance path than is effected by the usual arrangement of a plurality of shorter petticoats projecting downwardly from the flange 20. A long petticoat 2! has the additional advantage of providing greater shelter for the surface inside the petticoat, and in order to provide additional resistance to the leakage path in this sheltered zone, an additional skirt 24 is formed on the lower edge of the boss I6, which skirt will normally stay dry and clean notwithstanding adverse atmospheric conditions. This skirt is of comparatively short peripheral extent so as to provide high resistance for its length of path. The petticoat 2| is spaced sufficiently from the axis of the insulator so that there is no danger of discharge from the lower edge of the petticoat to the cap ll of the next adjacent insulator in the string. Advantage is taken of the space thus provided to locate the skirt 24 in such position that it provides a most effective addition to the leakage path due to its protected position and relatively short peripheral length. This skirt also provides an extension for the porcelain member through which the electrostatic lines of force from the point 19 to the lower edge of the cap H extend, thus reducing the tendency to discharge from the lower edge of the conducting coating I! along the surface of the dielectric member, thus avoiding radio disturbances.

I claim:

1. An insulator comprising a dielectric member having a radially extending flange, a petticoat extending downwardly from the lower surface of said flange at substantially the midposition radially thereof, said dielectric member having an axially extending pin hole therein, the material of said dielectric member extending downwardly about the mouth of said pin hole below the lower surface of said flange forming a hollow boss to provide an extension for said pin hole, the inside wall of which extension is in substantially straight alignment with the inside wall of said pin hole, a pin disposed in said pin hole, cement retaining said pin in position in said pin hole, the lower surface of said cement being spaced inwardly from the mouth of said pin hole an amount comprising the thickness of the boss about the mouth of said pin hole and the major portion of the thickness of said flange, the inner surface of said pin hole from the surface of said cement to a point adjacent the mouth of said pin hole being covered with a conducting coating.

2. An insulator comprising a dielectric member having a boss formed on one side thereof, a cap surrounding said boss and secured thereto by cement, said boss having a pin hole therein the side walls of which have substantially straight line elements extending substantially to the mouth of said pin hole, a pin disposed in said pin hole and secured in place by cement, the outer surface of said cement being spaced inwardly from the mouth of said pin hole, a radially extending flange on said dielectric member, a petticoat extending downwardly from the lower face of said flange at a midpoint radially thereof, the material of said dielectric member extending downwardly about the mouth of said pin hole beyond the lower surface of said flange and forming a ring about the mouth of said pin hole, a supplemental skirt extending downwardly from the lower face of said ring and spaced inwardly from the inner face of said petticoat, and a conducting coating on the inner face of said pin hole extending from the surface of said cement to a point adjacent the mouth of said pin hole.

3. An insulator comprising a dielectric member having a boss projecting at one side thereof and having an axial pin hole opening at the side of said dielectric member opposite said boss, a cap secured to said boss, a radial flange extending outwardly from said dielectric member adjacent the lower edge of said cap, the material of said dielectric member extending downwardly adjacent said pin hole beyond the lower face of said flange to form a dielectric ring about the mouth of said pin hole, a pin disposed in said pin hole and secured therein by cement, the lower surface of said cement being spaced inwardly from the mouth of said pin hole an amount equal to the vertical thickness of said ring plus the major portion of the thickness of said flange, the inner surface of said pin hole from a point adjacent the mouth thereof to the surface level of said cement being covered with a conducting coating electrically connected with said cement, the elements of the inner surface of said ring being substantially in straight line alignment with the elements of the inner surface of said pin hole, a petticoat extending downwardly from the lower face of said flange at substantially the midpoint radially thereof, the lower portion of said petticoat extending downwardly to overlap a portion of the cap of the next adjacent insulator in a string and being flared outwardly, and a supplemental skirt extending downwardly from said ring about the mouth of said pin hole, said supplemental skirt being spaced inwardly from said petticoat and outwardly from said pin.

4. An insulator comprising a dielectric memher having a boss, a cap secured to said boss, said boss having a pin hole therein. opening at the side of said insulator opposite said cap, a pin disposed in said pin hole and secured therein by cement, and means for preventing formation. of corona about said pin at the surface of said cement for substantially all weather conditions, said means comprising a dielectric ring integral with said dielectric member and surrounding said pin, the opening in said ring providing an extension of said pin hole, said cement terminating within said pin hole at a position closer to the plane of the rim of said cap than to the mouth of said pin hole, a conducting coating on the wall of said pin hole electrically connected with said cement and terminating adjacent the mouth of said pin hole in a region of lower electrostatic stress than that adjacent the terminaiton of said cement, the elements of the side walls of said pin hole being substantially straight lines to the termination of said conducting coating, a skirt extending downwardly from the outer edge of said dielectric ring, and means for preventing contamination of the insulator surface adjacent the termination of said conducting coating, said last named means comprising a flange projecting radially adjacent the rim of said cap and a petticoat extending downwardly from said flange at a position beyond said ring and the skirt thereon but spaced inwardly from the periphery of said flange so as to be out of the path of vertically falling drip water from said flange, said petticoat extending downwardly a sufficient distance below the bottom edge of said skirt substantially to insure protection of the surface of said ring and skirt adjacent the termination of said conducting coating from contamination for practically all weather conditions.

JOHN J. TAYLOR.

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