US1786784A - Insulator - Google Patents

Description

Dec. 30, 1930. B SMITH 1,786,784-

INSULATOR Filed July 15, 1925 INSULATION /0 1 m. 5; :5 ii &

INSULA 7701 mew ma Hora/d5. 507/777.

6 ATTdRNEY WITNESSES:

-unirso'srATEs I HAROLD B. SMITH, or woncns'rnn, massacnusn'r'rs, nssrenoa r 'wnsrmenousn Patented Dec. 30,1930

rATENr orrlcs v nnnc'rnrc & Manuracrunme COMPANY, A CORPORATION or PENNSYLVANIA ms LA'roa Application filed July 13,

My invention relates vto insulators and particularly to high-potential insulators of the suspension type. a

One object of my invention is to provide an insul'atorot the above-indicated character that shall permit the proper spacing of highspotential transmission conductors and, at the same time, employ laterally extending annular field-controlling members of relatively great diameter. I v

Another object of my invention is to provide means for so, grouping and mountinga plurality of high-potential suspensioninsulators as toprevent the detrimental efi'ects sometimes causedby violent winds. I

Another object of my inventionis to pro;

, 'vide a highspotential insulator in which'the danger of arc-over during Wet conditions is efi'ectually reduced. A further object of-my invention istoprQ- vide a high-. 'otential insulator that shall be simple and. urab-le in construction and economical to manufacture. a 1 J V Heretofore, in the art of supporting highpotential transmission. conductors, it .has been the most general practice, in commercial service, to attach the conductors to the upper ends of rigid insulators projecting upwardly from cross-arms of poles or towers andto attach the conductors to the lower ends of insulators hung flexibly from. the lower sides of the cross-arms, Q

Attempts have been made, in high-voltage service, to utilize rigidly depending insu- Y lators but no high-voltage insulators of this type have been extensively adopted because of the relation of the length and weight of the insulators .to the voltages of the.

conductors supported thereby; In insultstors, as heretofore employed, the length and weight thereof have beensuch that, for

voltages up toa certain general value, the rigid orvpin type have been most advantageously mounted abovethecross arms; For

voltages above the values for whi h the rigid pin-type insulator is employed, the flexibly.

suspended insulator has been employed because of the increased length and weight thereof. However, the swaying of the flexibly suspended insulators and the conductors 1923. Serial No. 651,246.

placed relatively. far apart, resulting in largerand more expensive cross-arms and towers. i My invention does'not contemplate the mere. inversionof an ordinary insulator of the rigid pintype so that the conductor hangs below the cross arm because, for the same voltages that could heretoforebe resisted by such an insulator, the mechanical conditions would be' but little varied, there would be practically nothing gained and no invention would be involved. p Y 'In my prior Patents #1,730,250 of ()ct. 1,1929 and #1,? 29,691 of Oct. 1,1929, are set forth structures by which the length of an insulator may very materially reduced fora given voltage.

The first, abovejementioned patent discloses,

member entirely of corona-forming stresses.

The second of the above-mentioned pats ents sets, forth an insulator that materially increases the value of the first, under wet con.- ditions, by removingthe water-drip portion from the zone of maximum potential gradient, as will be apparent by referring to the application. 9 As a'result of the. above-mentioned-developments in the insulator art, a rlgid insulator is obtained which is the 'equi'valentin ability to withstand high voltages of awformer insulator, which, by reason of its length, would not be mechanicallyadapted for rigid mounting at one end only, either vertically above or below'across arm.

In the insulators of all ofthe prior patents herein mentioned, I employ an upper field distributing and directing member of relatively great diameter. Thus, when adapting the member to an insulator of the rigid pin type above. a cross arm, it will be of the same potentialas the, conductor which it supports. Consequently, in designing the tower or support, the spacing of the field distributg member, as well as the spacing of the con actors, must be taken into consideration. In other words, the outer edges of the relatively widely extending field distributing members must in that form be spaced as far from each other as would be the conductors ordinarily.

In providing a flexibly ended insulator with such an upper field controlling member, the lateral extent of the member 11 st also be taken into consideration in prong proper spacing and lateral swing of conductor. Hence, with either the rigid pin-type insulator above the cross-arm or the flexible suspension"insulator below the cross-arm, certain space and structure considerations are sary.

In practicing my invention, 1 provide a rigid insulator, rigidly suspended from the underside of a support or cross arm, that comprises a laterally extending upper-field-controlling member which grounded to the cross-arm, and is provided with an annular intermediate portion of maximum potential gradient adjacent to surface. A lower terminal member, of substantially toroidal shape having a rim portion of relatively great radius, surrounds the longitudinal axis of the insulator in spaced relation thereto and cooperates with the upper field-controlling member.

Since the upper iield controlling member is grounded, it may be placed as close to other similar members as desired to ensure the proper spacing of the conductors. Thus, since the wide spacing of the upper field controlling members, as in the pin-type insulator above the cross-arm, is eliminated and the members do not sway with thewind, as in the flexibly suspended type of insulator, an effective and economical structure is obtained.

Flexibility for the conductor and compensation fol-lateral stresses in the insulator are obtained by a flexible extension at the lower end of the insulator.

Figure 1 of the accompanying drawings is .an elevational view of a portion of a hightension transmission structure, as viewed in the direction of the conductors, with a plurality of insulators constructed and grouped in accordance with my invention, and

Fig; 2 is an enlarged View, partially in elevation and partially in section, of one of the insulators shown in Fig. l. I

In general, the device embodying my invention may comprise a support or pole 1, only the upper portion of which is shown, crossarms 2 thereon and a plurality ofinsulators 3.

The latter are preferably constructed as shown in Fig. 2, each comprising an elongated preferably plain cylindrical insulating member 4 having end portions 5 and G that are screw-threaded, or otherwise suitably iormed, to receive socket terminal members 7 and 8, respectively. The upper socket member 7 is provided with a flange 9, or is otherwise suitably formed for rigid attachment to the cross-arm 2, as by bolts 10.

A preferably sheet-metal member 11 of substantially hood shape is secured to the upper socket member 7 and comprises an outer perimetral water-drip portion 12 and an intern'iediate annular portion 14 of maximum potential gradient, adjacent to its surface as will hereinafter more particularly be pointed out.

The lower socket member 8 supports a preferably short cable member 15 or any suitable device, such as a pivoted link, to receive and support a conductor 16. This construct. on compel sates for lateral wind pressure andpermits the conductor 16 to swing laterally without transmitting movement to the insulator. A portion 17, which may be a separate member or integrally formed on the socket member 8, is of substantially ring or toroidal shape, surrounding the. insulating member in spaced relation thereto, and secured to thesocket member 8, as by a flange l8. Openings 19 are provided in the'fiange it for the escape of moisture.

The shortest distance from metal to metal,

between the. members '7 and 8 lalongthe surface of the insulating member 4, is greater than the distance shown by a dotted line X, between the member 17 and the portion 14 on the member 11. ,At the upper end of the line X, the portion 141s curved about a relatively Wide radius to preventundueconcentration of the electric field thereon and provides an annular zone o'i'maXimum potential gradient adjacent thereto. The member 17, at the lower end of the line X is similarly of relatively wide radius. The above described construction causes the electric field to be of maximum intensity along the line X, but, since the surfaces of the portions 17 and 14 are widely curved, substantially the maximum break-down strength ofthe air is obtained.

The curvature of the portions 17 and 14 also causes the electric field strength to become weaker substantially in proportion to the distance removed from the'line X in either side of the latter. Thus, the insulat ing member 4 extends through a portion of the field that is so weakened, and directed along lines substantially parallel to its sides, that corona never tends to form thereon. Also, the water drip portion 12 on the member 11 is so removed from the line X as to effectually prevent any considerable reduction in the break-down voltage of the insulator under wet conditions.

Being grounded to the cross-arms 2, the members 11 on one cross arm may be placed as close to each other as desired, it being only necessary to properly space the lower and smaller live ends of the insulator. This construction provides advantages, as pointed out above, over an ordinary rigidly depending insulator and is an improvement over the insulators of my herein mentioned prior patents whether they be mounted rigidly above, or flexibly suspended from, the cross arms.

I While I have shown and described a particular form of .my invention, changes may be effected therein without departing from having an annular toroidal portion intermediate .its axis and perimeter advanced from the adjacent parts thereof'toward the lower terminal member, and means for rigidly securing each insulator to said supporting structure to permit the upper field-controlling members of the respective insulators to be placed relatively close to each other.

In testimony whereof, I have hereunto subscribed my name this tenth day of July, 1923. HAROLD B. SMITH.

the spirit and scope thereof, as set' forth in. i

the appended claims. o

I claim as my invention:

1. In a high-potential insulator device, the

combination with a main supporting structure, of a plurality of insulators depending therefrom each comprising a grounded laterally-projecting upper electrostatic-field-controlling terminal member having a widelyrounded toroidal portionintermediate its outer extremity and the longitudinal axis of the insulator advanced from the adjacent portions thereof toward the lower end of the insulator, an elongated insulating member ture, of a plurality of insulators depending therefrom each comprising a grounded annular laterally-projecting upper electrostatic-fiel'd-controlling member of relatively great diameter, an elongated insulating member depending therefrom, a positive laterally-projecting lower electrostatic-fieldcontrolling member of lesser diameter, disposed outside, and co-operating with, said upper member to confine flash-over thereto to a position laterally between the outer perimeter thereof and the insulating member andto direct a weakened central field portion substantially parallel to said insulating member, and means for connecting all of said parts in fixed relative positions.

3. In a high-potential suspension insulator, the combination with a supporting structure, of a plurality of elongated insulating members depending therefrom, each having rigidly-connected grounded upper, and positive lower, terminal members adapted to direct a weakened central field portionjsubstantially parallel to said insulating member and each upper terminal member comprising an annular laterally-projecting electrostaticfield-controlling portion of relatively great diameter, said laterally-projecting portion

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