US1250387A - Electric insulator. - Google Patents

Description

P. H. THOMAS. 'ELECTBlC-INSULATOQ.

APPLICATION FILED MAYI6. I913.

Patented Dec. 18, 1917.

INV NTO Jr/ max WITNESSES UNITED STATES PATENT OFFICE."

PERCY H. THOMAS, or UPPER MONTCLAIB, NEW JERSEY.

ELEcraIo IINS'ULATOB.

To all whom it may concern:

Be it known that I, PERCY H. Tnoms, a

citizen of the United States, andresident of Upper Montclair, county of Essex, State of New Jersey, have invented certain new and useful Improvements'in Electric Insulators, of which the following is a specification.

My invention relates to insulators for high tension electric lines, such as power transmission lines. More particularly my insulator is of the suspension type and is adapted an insulator which is relatively free from of being obtained of great uniformity andthese defects and is at the same time cheaper and easier to construct and more convenient inform. I also utilize a novel mechanical principle in insulators of this type, in that I may rely on vitreous material in tension.

I prefer to use insulating material for the main body of my insulator of porcelain, glass or other vitreous material which has a very high dielectric quality and is capable high quality. This material has certain mechanical limitations, however, due to manipulation in manufacture so that many desirable forms and methods of construction trio and I have taken advantage of this principle in my insulator. I have also used such forms of constructionwhereb a larger thickness of insulatin material 1s practicable than in the o'rtIinary insulator constructions. Y 7 Y I also provide a form favorable for resisting the effects of heavy rain or mist which tend to cause a breakdown of an insulator. I provide an insulator that will have a rela- Speciflcation of Letters Iatent.

Patented Dec. 1-8, 191 '7.

Application filed Hay 16,'1913.. Serial No. 767,995.

tively great mechanical strength as well as good electrical characteristics.

My invention will be understood by reference to the accompanying drawings, in which Figure 1 is a longitudinal central sectional view of an insulator embodying my invention;

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

Figs. 3 and 4 are similar sectional views of two modifications of Fig. 1;

Fig. 5 is a plan view of a detail of Fig. 4, portions being broken away;

F ig'. 6 is a sectionalviewof a string suspension insulator conforminggenerally with the aforesaid figures;

Fig. 7 is a-sectional view of a modified type of suspension, comprising rigidly connected units;

Fi 8 is a cross section on the line 8-8 of Fig. ll; and i Fig. 9 is .1 vertical sectional view of another modification of vFig. 1..

In the form of my invention shown in Fig. 1 the two U-shaped pieces 22, 23,-are provided with large overhanging ends as shown, whichtend to give a flat electric field between the top and bottom of the insulator. There is of course a much more concentrated field between the U-shaped pieces 22, 23, within the porcelain 19but this is not a stress in air and the porcelain itself must be punctured for a break to occur at this point. These enlarged conduct: ing portions serve particularly to control the electric field in the air at the ends of the porcelain piece, and thus ture breakdown of the alr locally. They further serve to make the natural direction of the lines of electric force along this surface more nearly parallel to the center line between the terminals. I prefer to so shape this overhanging ortion and the surface of the porcelain itse f that no lines of electric forceshall enter or leave the porcelain surface, or at least to approximate-this condirevent a premashown the main body portions above and below, but in these insulators I rely on the tensile strength of the porcelain to carry the load of the insulator. I am aware that-it'his has not been attempted heretofore in lineinsulators but with the precautions which I take in my designs this plan is not only feasible but desirable. This design permits of a much greater insulation strength, of a better control of the distribution of the electric field and a simpler mechanical construction.

In Fig. 3,24 is the porcelain piece with the recesses at top and the bottom respectively. In these recesses are pipes or metal cylinders fitting rather closely and cemented to the porcelain with Portland or other cement. These pipes carry plugs 27 and 28 which are provided with hooks or rings as. may be desired. At the top and bottom of the insulator and carried if desired on the pipes are overhanging conducting pieces 25 and 26, which serve to control the form of the electric field at the surface of the porcelain as described in connection with Fig. 1. At 31, I show a ring or rib for breaking up any tendency for water to form streams on the surface of the porcelain and to increase the creepage surface. If desired there may be used more of these ribs at various points on the surface of the porcelain.

Fig. 4 is like Fig. 3, except that the porcelain piece 34 is larger in size and is furnished with larger recesses, which areformed to carry porcelain or other insulat ing cups cemented into the recesses, as shown at 37 and 41. Withinthese cups are cemented pipes as before, shown at 38 and 40, carrying plugs 45 and 46, screwed or otherwise fastened into the pipes 38 and 40. Fig. 4 as well as Fig. 3 shows a flat screw thread on the inside of the porcelain surface which is to make the cement take a better hold thereon, see 39, 39, in Fig. 4. At 35 and 36 are shown plates constituting the field controlling conductors at the top and bottom of the porcelain. The porcelain surface here shown is curved at 44 to conform more nearly to the lines of electric force in the air. A rib 43 is used, similar to the rib 31 of Fig. 3.

With the type of insulator shown in Figs. 3 and 4, it is clear that the porcelain barriers 32. and 42 between .the recesses in the porcelain can be made as thick as desired and thus may withstand very high potential strains. Similarly the use of the cups of -F1g. 4 again greatly increases the insulation strength of the insulator and has the advan-' tage that the cups may be made separately and may be tested separately and then assembled and cemented, thus insuring more uniform material and avoiding'the use of any very thick material.

In Fig. 5 is shown the: top view of the porcelain cups of Fig. 4 with the major portlon of the porcelain piece 34 broken away.

In Fig. 6 is shown a train'of insulators of the general t pe of Fig. 3, but having wings or umbrel a-plates to assist in securing an even distribution of potential between the several units of the string. It is well known that, since in a string of insulators, all the charging current that must satisfy the ground capacity of the several insulators of thestring will have to pass through or over the line unit, this unit will tend to take more than its share of the potential and so one down the line, the last insulator having less stress than any of the others. I overcome this condition by providing a means of giving more capacity to the insulator units nearer the line, to compensate for the greater charging current flowing over such insulators. Of course, I can similarly increase the capacity of any particular.

plugs or pipe pieces at 48, the top and bot tom conductors at 49 and the umbrella pieces at 50, graded to .give progressively greater capacities toward the insulator nearer the conductor 51. If it be desired to grade the capacity in the opposite direction this can, of course, be done by reversing the order of the umbrella pieces. The pieces 48 are shown having rounded terminals at the central portions of the porcelain, to give a more uniform electric field.

Figs. 7 and 8 show a modification of the insulator of Fig. 3, where instead of using a single pipe piece to carry the load a number of smaller pieces, extensions, or rods are used arranged to get a better hold on the porcelain and yet to form, electrically speaking, substantially a single similar conductor or electrode. -porcelain walls are obtained, which 1s an advantage from a manufacturing point of view. This insulator is shown as made up of two parts, semi-rigidly fastened together. Other numbers of units than the two shown may be used. The porcelain pieces'are shown at 52, the rods used for carrying the load and forming the electric field are shown at 53 and the metal caps at the top and bottom of the porcelain. pieces are shown at 54, 58, 59 and 60. The'ipiece 56 carries the piece 54 and the otheiij supporting pieces are fitted together mechanicallyto give strength and to shed the rain asfisshown. There are ribs By this construction thinner terminal at the central portion of the porcelain, similar to pieces 48 of Fig. 6, as above described to give a somewhat more uniform electric field. This train of insulators will swing as a unit and not each unit on the other as may be the case when the connection between units is flexible; The piece 61 carries the line conductor.

The insulator of Fig. 9 is like that of Fig.

1, except that the porcelain piece 62 is not round in cross section, but is flattened and pieces are more that the rods 01 holding numerous and are of differentlengths to utilize the compressive strength of the porcelain. The short rods'are shown at 65 and. the long rods at 64. The porcelain piece is '62 and the two metal overhanging pieces are shown at 63. These overhanging pieces will act as a protection from the weather both in this and the other structures where they are used. I

It will be understood that the various forms of insulators and other devices that I have shown in connection with any one figure maybe fused with the other forms wherever appropriate and that -I do not limit my inventlon to the particular constructions shown but that any other embodiments of the same ideas, obtaining substantially thesame results by equivalent means come within its scope.

What I wishto secure is in part the design of an insulator to secure a relatively uniform distribution of electric field at the critical points, which willgreatly increase the voltage that the insulator will stand and to get simple mechanical forms relyin in some instances on thetensile stren li of porcelain. With the relative-short an thick 'sha be ound reliable. Y Y

A suitable distribution of the electrostatic field in the portion of the main body of the rcelain or other insulating material lying tween the metal attachment piecesis important, as well as in the air'surrounding the insulating member, since this will pro vide greater reliability with a given mini:

mum thickness of porcelain, or a thinner ma.

' terial as may be appropriate. This-control of the field within the porcelaln may be attained by properly shaping the opposing faces of the metallic attachment pieces. For example, by making them approximately flat and parallel as in Figs. 3 and 4,or as in Figs. 7 and 8, where there are a plurality recommended these insulators will a -New York and State of New by locating the several faces of each attachment piece on a mathematical surface,

approximately aplane surface and generally parallel to the similar surface con-,

' the central metallic figures may be advanced slightly over the outer figures, as described above. 7 I

I claim as myi'nvention.

1. Ina high tension line insulator, a load carrying tension member of vitreous ma-. terial, having a plurality of recesses'on opposite faces, stress taking members entering saidrecesses, means for distributing the me- .chanical stress from the stress taking members' dver the surfaces of said recesses and of opposing faces. on each attachment piece,

thin walls for that portion of the tension member adjacent to the. stress taking members, whereby the-mechanical forces are favorably distributed.

2. In a line insulator, a porcelain tension member carrying the load of 'the insulator,

. having its end portions disposed in the form of walls or partitions thin relative to the stress receiving surface of the member and forming recesses in the said tension mem-. ber, metal stress bearing members secured in said recesses, whereby mechanical stress may forming recesses in thesaidstension member,

metal stress bearing members secured in said recesses, whereby mechanical stress; may be favorably distributed throughout the material of the tension member, the metal members attached to the respective ends. of the porcelain tension memberbelng dlsposed with their opposed faces located in a plane surface lying generally parallel, whereby the electrostatic stresses in the porcelam between the oppo sed faces are favorably dIS- tributed. e I v p Signed at New York, in thecounty of York, this 15 day of May, A. D. 1913.

rERcY H. THOMAS.

Witnesses:

GEORGE H; Sil'oonnnmGE,' Jr., .Tnos. Brown.

Ill

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