US1811530A - Insulating device - Google Patents

Description

June 23, 1931. v B UM 1,811,530

INSULATING DEVICE Filed Oct. 20, 1921 INVENT0R.4

ATTORNEYS.

i Patented June .23, 1931 UNITED STATES PATENTA OFFICE FRANK 'G. BAUM, OF SAN FRANCISCO, CALIFORNIA, ASSIGNOR TO WESTINGHOUSE ELECTRIC AND MANUFACTURING COMPANY, A CORPORATION OF EENNSYLVANIA INSULATING DEVICE Application filed October 29, 1921. Serial No. 509,148.

My inventionhas one of its chief uses in connection with insulating supports for high voltage transmission lines which are exposed to the elements. Particularly where such supports consist of a string or series of elements disposed one above the other, it is recognized that conditions are apt to develop in the string which facilitate the formation ofx arcs or flash-over currents, with the likelihood of serious damage to the units of the string. The desideratum is to maintain the surfaces of the supports at as near infinite resistance as possible, such as they have when they are dry or when they are clean and wet. Dirt, such as dust, smoke, and other solid particles floating in the air, lodge on the surfaces, and in time this tends to become encrusted on the surfaces due to the successive wetting by dew and fog and then drying from the heat of the sun. Before such an encrusted condition arises the dirt will usually be washed off by rains from those portions of the units which are exposed to the rain, but as these units have been cdnstructed heretofore the action of the elements is not uniform on the surfaces of the various units. A thorough natural cleaning has been shown by practical experience to be essential to satisfactory operation. 'On the other hand, if the entire leakage surface of a'unit is exposed to the "action of rain, the continuous water film formed thereon acts as a. leakage medium having a greatly lessened resistance and the effectiveness of the unit is consequently low.

The usual design of suspension insulators is for a normal potential duty of about 10,-

000 volts and is fairly satisfactory for low voltage lines. In the very high voltage lines,

the number of units is necessarily increased to such an extent that the unitsnear, the line end of the string take up most of the potential.

and are consequently under a high stress. This is a great disadvantage since'flash overs and punctures are more likely to follow abnormal increases of voltage, and since the insulators are usually of glass, or porcelain, the

high temperature produced by a flash over current soon fuses and destroys unit after unit of the string and throws the line voltage upon effectively'shorter and shorter strings.

The stress of the units is also increased under various weather conditions, such asldirt, ram, etc. and since the individual units are of small capacity compared to the total voltage from the line to ground the likelihood of a break down is greater than if larger individual units were used.

An object of the invention is to provide an improved insulator unit upon which the weather action will have a maximum possible uniformity, and by the use of which the number of units in a string for a line having a given voltage may be reduced.

A further object is to provide an insulator umt upon which the potential stresses will be more uniform under out door weather condltlons, and which has a higher insulating factor of safety.

A further'obj ect is to provide an improved 1 insulator construction of the interlinked-suspension type for the accomplishment of the objects above enumerated. f

-Other objects and advantages will be apparent from thefollowing detailed description of embodiments of the invention.

In accordance with my invention I provide axially elongated insulator units each with peripheral corrugations or ribs, the distance of the outer peripheries of which from the axis preferably decreases progressively from the upper end downwardly. The grooves be tween the ribs or corrugations are preferably somewhat V-shaped so that the under face of each corrugation will have considerable inclination whereby a driving rain will directly enga e and wash it clean. The upper surface 0 each rib or corrugation is given sufficient slope tov cause the water to readily run off, and because of the preferably greater overhang of the upper ribs of each unit the greater portion of the water oneach rib will not successively drip from the upper ribs are preferably each provided with a narrow upwardly extending surface facing the axis 0 the body, and this may be conveniently accomplished by providing in each underface one or more drip grooves which cause the collected water to drip directly downward from each rib instead of running inwardly entirely across each under surface thereof. The units may be formed into a string or be otherwise connected to form a larger unit or insulating device, and the unit or device may be used to insulate the line from a tower or be in the form of a bushing for a line wire such as is used in transformers or switches.

In the accompanying drawings:

Fig. 1 is an elevation, partly in section of a portion of a string of insulator units constructed in accordance with my invention.

Fig. 2 is a similar view of a slightly modified structure.

Fig. 3 is a sectional elevation of a unit of the interlinked suspension type in which my invention has been embodied.

In the fragmentary string shown in Figure 1, which forms the support between a line wire and an arm on a tower, each unit has an axially elongated body 1 of suitable insulating material, such as of glass or porcelain, and is of an inverted frustro-conical shape with a peripheral surface undulating from end to end. That is, the body may have transversely disposed peripheral ribs or corrugations 2 which become progressively smaller in diameter from the top to the bottom of the unit, whereby each rib slightly overhangs the lower ribs of the unit. The upper surface 3 of each rib is inclined outwardly and downwardly to adegree sufiicient to shed collecting moisture readily, and because of the overhang of each rib the moisture falling from the periphery of the rib will pass clear of the lower ribs of the unit. The under surface l of each rib is inclined inwardly and downwardly to a degree which will ermit of direct contact therewith of drivmg rain in order to be washed thereby. The under faces of at least the ribs'of larger diameter are each provided with a narrow up-" wardly extending surface 5, facing the axis of the body, and a very convenient and satisfactory manner of providing this narrow surface is by forming an annular groove 6 in the under surface, which groove I may call a drip groove. These surfaces or grooves break the continuity of the water film upon the under faces of the ribs and cause the collecting moisture to drip directly downward instead of passing inwardly across the entire under face of each rib. The space between adjoining ribs is therefore somewhat V- shaped and permits a driving rain to enter the same and wash the surfaces uniformly. The upper end of the body is provided with a boss 7 upon which a thin band 8 of metal is securedor anchored in any suitable manner, such as by shrinking the band thereon, or by cement between them. The periphery of the band is threaded for a slightly loose ongagement with the internal threads of a cap member 9 of a-suitable supporting device 10. The lower end of the body is provided with a recess 11 which preferably extends into the boss 7 at the other end. A metal pin 12 from a next lower unit which forms part of a supporting device 10, is anchored within the recess at its upper end in any suitable manner such as by cement, or threads, or both. The remainin space between the pin 10 and the walls of t e recess 11 may be partially or entirely filled with a suitable insulating material or compound, or the walls of the recess may, if desired, be covered with a conducting material so as to provide a definite leakage path between the pin 12 and the lower end of the unit. In the units illustrated in Fig. 2 the body of each unit 1 has the same general characteristics as the units shown in Fig. 1, the parts in the unit shown in Fig. 2 having the same reference characters with the addi tion of the exponent a. The boss 13 corresponding to boss 7 is formed upon the lower instead of the upper end of the body of the insulator and carries a threaded metal band 14, similar to band 8. A metal cap 15 of a supporting device 16 is somewhat loosely threaded upon the band and serves to support the next lower unit or the line wire from the boss. A. recess 17 extends axially of the body from the upper end and into the boss, and a pin 18 flexibly connected to the cap carried by the unit next above dependsinto the lower end of the recess and is secured therein in any suitable manner such as by threads,

cement, or both. The remainder of the re cess surrounding the pin is then filled with a suitable insulating compound or material,

such as with bakelite for example.

Where the insulating device comprises a string of such units, the line wire is carried by the bottom of the string and the highest voltage upon each unit will in such cases always be at the lower end. By the use of the cap at the lower end, as shown in Fig. 2 the potential stress is distributed over a greater peripheral area than is the case when a pin is used at the lower end, and accordingly there is less danger of flash overs.

The flexible oint between the units is very desirable to prevent cracking of the unit bodies due to lateral stresses. Where, as heretofore, the caps were shrunk directly upon the bosses the stresses produced in a boss by the band at cold temperature often cracked the insulators, but with a thin band first shrunk upon the boss and the cap screwed or otherwise somewhat loosely connected thereto there will be a reduction in the number of damaged units due to temperature changes. The elongated body makes use of vertical dimensions to get the desired surface leakage and cleaning, and the numberof units necessary in the string is reduced. The advantages of the increased not lost under wet conditions because the continuity of the water film is broken by the drip grooves.

In Fig. 3, the unit is of the interlinked suspension type. The body 18 of porcelain or other suitable insulatingmaterial is preferably axially elongated with an undulating peripheral surface as shown in Figs. 1 and 2. The body is provided with a recess 19 extending axially from the lower face, and with independent, separate, interlinking apertures 20 and 21, as usual in interlinking" suspension units, both ends of the aperture 20 opening into the recess 19, and both ends of the aperture 21 opening from the upper face of the body. A flexible cable 22 is passed through the aperture 20 with the free ends of the cable terminating withinthe recess 19. The free ends of the cable are received within a McIntyre sleeve 23 which is well known in the art, and the sleeve is twisted, torsionally, to firmly secure the ends of the cable therein. A nipple 24: is threaded into the lower end of the sleeve and the angular free ends of a link 25 passing through the aperture 21 of the next lower body are coupled thereto by a split element 26, the parts of which have in their abutting faces, comple; mentary recesses to .receive the head of the nipple and the angular ends of the link. The parts of the element are clamped together by bolts 27 or other suitable means. The advantages of a long insulating body with a large leakage surface of any desired contour are thus available with the interlinking type of suspension. f

It will be obvious that various changes in the details and arrangements herein described and illustrated by way of explanation of the nature and principle of the inventions, may be made by those skilled in the art within the principle and scope of the invention.

I claim:

1. In a high-voltage suspension insulator,

upwardly-and-outwardly-sloping under surface, and certain of said under surfaces having annular portions formed to prevent the formation of a continuous water path between the ends of the insulator.

2. An insulator of the character described comprising an elongated tubular porcelain body, a metal cap secured upon one end of said body, a bolt extending axially within the body, a mass of cement embedding one end of the bolt within the said end of the body, the other end of the bolt projecting beyond the other end of the body and a mass of water-repellent plastic material filling the space within the body between said mass of cement andthe sceond named end and acting to center the bolt.

In Witness whereof, I hereunto subscribe my signature.

' FRANK G. BAUM.

the combination with a metal cap terminal member and a relatively long pin terminal member having one end in said cap, of a dielectric member comprising a head portion of substantially cup-shape disposed in said cap terminal member over said pin end, a tubular extension of said head portion having itsinner surface sloping, for the greater portion of its length, at a certain angle from said pin and, for a portion of its length adjacent to its outer end, at a greater angle to the pin to form an outer-end flange, and a plurality of laterally-outWardly-projecting annular flanges on said tubular extension of successively smaller diameters from adj acent to said head portion to adjacent to said outer-end flange each having a downwardlyand-outwardly-sloping upper surface andan

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