US2500928A - Insulator support - Google Patents

Description

March 21, 1950 R. cAsE INSULATOR SUPPORT Filed Aug. 4, 1948 f Immun@ @@4314 @die Patented Mar. 21, 1950 IN SULATR SUPPRT Rogers Case, Orange, N.'.., assignor to Transandean Associates, Inc., Orange, N. J., a corporation of Delaware Application August 4, 1948, Serial No. 42,530

2 Claims. l

This invention relates to an insulator-supporting pin for attaching insulators of glass, porcelain, rubber or other suitable material on the cross arms of poles included in the lines of communication systems and like electrical wire lines.

In previous practice such insulator pins have been made of steel, iron or the likeand particularly of steel which is galvanized to increase its resistance to corrosion. In practice and this is particularly necessary in the case of glass insulators, lead sleeves are interposed between the insulator engaging thread of the pin and the body of the insulator or a threaded Wooden structure known as a cob is engaged with the head of the pin and in turn has threaded engagement with the body of the insulator. Such insulator pins of steel or iron are both unnecessarily heavy and relatively expensive to manufacture, inasmuch as they involve the initial forging of the pin structure and a subsequent threading operation performed at the head as well as at the shank of the pin.

I have discovered that insulator pins may be composed of bodies and heads made integral by casting a light metal selected from magnesium, aluminum and the magnesium and aluminum alloys, With increased ease of manufacture and with marked improvement in the utility of the pin in its function of mounting the insulator on the cross arm of the pole. It is an accepted fact that for most of their uses in the arts magnesium and aluminum seldom are used in their pure form but that the light metals called magnesium and aluminum as comprised in manufactured articles, usually include varying proportions of alloying metals. As is most convenient, the terms magnesium and aluminum as herein used are to be understood as defining primarily the useful alloys of magnesium and aluminum in which those metals preponderate. In casting the light metal, the operation is performed by closed-mold casting, and as herein used the word casting is thus to be taken as qualified to a method of casting appropriate to the metal which is cast.

The threaded shank of the insulator pin by Which it is attached to a cross arm or analogous structure being desirablyof steel, iron or other metal having relatively great tensile strength to provide improved shear resistance in this portion of the complete pin, is integrated with the body of the insulator pin in suitable manner as by threading, Welding or the like, and can be integrated in the pin structure by being cast into (Cl. 24S-220.5)

2 the body of the insulator pin during the formation of the latter.

I have discovered that an insulator pin of this sort possesses adequate strength and possesses many advantageous features in use as Well as in the simplicity of its manufacture. Since magnesium and aluminum are highly resistant to corrosion, no galvanizing is necessary to retard corrosion. The omission of galvanizing not only reduces the cost of manufacture but eliminates an undesirable feature of insulator pins as previously made. Galvanizing invariably causes roughness in the threading at the head of the insulator pin, which roughness scores the glass or other substance of insulator bodies mounted on the head of the pin, if the substance of the insulator at any point comes into direct contact with the head, or thimble of the pin.

Previously, the heads of galvanized steel and iron insulator pins have been spaced substantially from the glass of the insulators as by the use of Wooden cobs or lead sleeves. Lead sleeves are separate elements added to the insulator pins when mounting the insulators thereon, and if omitted or if carelessly installed such sleeves have failed Wholly to prevent scoring the bodies of the insulators by the rough galvanized threads on the heads of the insulator pins. Such lead sleeves tend to lose their eifectiveness by deterioration in long continued use, and this is particularly the case when the insulator is mounted in locations in which it is subjected to continuous or frequently repeated vibration or shocks. Any slight scoring of the insulator bodies, and particularly if the insulators are composed of glass, makes them susceptible to breakage under abrupt changes in temperature and under slight blows which would not destroy an unscored insulator body or even under the effect of vibration. Wooden cobs are also separate elements which require an additional and careful operation in mounting them on the insulator pins. Even With care, there is great loss because of the splitting of wooden cobs as they are applied to the insulator pins.

Not only are the corrosion-resistant properties of magnesium and aluminum such that galvanizing with its introduced surface roughness is avoided, but it is also a fact that When formed in a die-casting operation the threads cast on the heads of the insulator pins have a particularly smooth surface which is incapable of scoring the contacted surface of a glass insulator body. Further assurance against scoring the metal of insulators mounted on the pins is pro- 3 vided by the fact that the designated light metals and a Wide range of their alloys are much softer than iron, steel and the like heavy structural metals.

There is also the surprising fact that the magnesium and aluminum insulator pins are at least as resistant to deflection, or bending, as are steel insulatorpins.' Deflection tests under equal loads show that the resistance of the'pins and the steel pins initially are almost equal. Because, however, the steel pins deteriorate by corrosion, over long periods of time and pins composed of-the .light metal promise greater serviceability in maintaining accurate alignment andfspacing ofrthesline Wires. i

For this reason I cast as integral structures th bodies and threaded heads', or at least the threaded heads, of insulator pins from a light metal as above defined. With the body of this structure the threadedshank of the insulator pin,

. `Whichis of metal such assteel orironz-possessing greater shear-resistance thanithat ofrthe'light fmetals, is integrated during the icastingoperaxmtion or in othersuitablemanner.

" s Generally--stated,-the. obiect ofgmys. invention is :to provide afmetal insulator pin onzwhich an insulatorroi glass or other; suitable insulating materialzis. mountable fin direct .contact-With the metal afgheador thimble, of the, insulator pin; the thimble o-fthe insulator pin being so composedl and so formed that the Ametal of lthe thimble does inot scratch onscore thesubstance oiY the insulator at litsbore,that the insulator is vnot broken by thermal expansion-of the thimble and the engagement I oftheinsulator and thimble ist not loosened by thermal contraction of the thimble ini variations of atmospheric temperature.

In the accompanying drawings:

Figi is an elevational view ot my-.insulator pin.

Fig. Ilisa plan vievv oftheinsulator .pin shown -in Fig. I.

.-nFig. III isa viewzshowing the head ofcthe in- 11 sulatorpin as in ,FigyIr in elevation on an enlarged-scale: andshowing in section offzaspoolform insulator of conventional formV thereon.

Fig. IV-is a vertical sectional View@ throughfthe terminal shankregion of. the; insulator pinshowing abolt,` `or threaded stem, secured` thereto.

Referring toFig. I of vvthe'dravvings;'therin- .wsulator pin therein -shownycomprises an integrally .castbody haying abody, or-shank, regionlxvhich circular in crossasection,v asquaredgregion adjacent the :base of zthewpinstructure and ar cir- :cular flange, orfbase, 3. Extendedinwardlyfrom ,fltheiouter surface offbase-S axially ofzzthef shank -thereis a threaded socketlt for the reception of a threaded, attaching stem; r Head l5 ofthe insulator pinis tapered-upwardly and the thread -6 cast on the head is` shown, as -is mostdesirable -as aisquare face, :or approximately. square face,` threadgiving Whatis ineffect an integrallycastcob tolwhich the insulator A shown in Fig. Il-I of thefdrawings i isappliedf It will be noted that the insulator A is in direct contact With the head of the insulator pim .Thesinsulator' vmay be composed ofglass, -hard -rubber,.porcelain yor other suitable Yvitreous or 4 non-.vitreous-material which is electrically .non-iconductive'.'` Becausenthef head orithimble, of the insulator'pin -is composed of the relatively soft flight metal and is vungalvanized, fit does x.not tend to score the opposed. surface oftheanonmetallic insulator in .contact of the threaded -head 5 ofqthe insulator ,pin with the `cooperatively f threaded bore a of theinsulator. i ATheavoidance of this scoring which Would occur if the head of the insulator pin were of relatively hard ferrous metal and particularly if the insulator pin had been galvanized to present a roughened surface, is important with respect to insulators composed of any suitable insulating material. It is of particular importance if the insulator be composed otiglassythe tendency o which to fracture H under wide'ftemperaturerswings is greatly intensified by even slight surface scoring.

For attachment of the insulator pin to a cross arm an attachment pin is connected to the lower -nsulator-p-in andis -provi'dedi'witha nut 8;-forenigaging theremotesuriace of the cross arm.

x The;general-suitability of-a ,light metal ofthe designated sort touse in, directfcontactuwith an ,.insulatonteven it such insulator be'composed of glasshas. been ,explained l above. Y" -Eyen ifcomposed of. such; metal, however.L thereremains the problem o .;thermal'expansiomand contraction of, the insulator pin under wide-temperature swings. .I have compensated for suhiproblem in satisfactory manner by longitudinallyslotting Vthethimblei ot-theinsulator pin throughout its A diameterxand throughout-a large proportion of its :i.:i.,longitudinal extent. As showni this slot-.9 .is of substantial vvidth to.provide an veffective bodily resilienceto the thimbleof tnepinand adequately til to compensate, for. thermal .expansion and contraction at both high and low` atmospheric temperatures.

' In diametrically adjusting the thimble of the insulator pin and the bore of the insulator,-the relationship ismadesuchithat atnormal or room temperature the thimble lof theinsulatorpin ts Atightly in thebore ottheinsulator.Withslight bodily compression in sucht. If then the as- 4'sembly be subjected tosubstantial rise in temi peraturethe tendency of the insulator ,pin thimwbleby` its, thermal expansion to crack the inr-.s sulator is neutralized to anadequate extent by "movement-ofthe. segmental sections of the' thim- Mbleivtoward each other. rfhat is, the reaction tothe pressure of the thirnble vagainst thebore of `theinsulatoris to `decreasethe Width of slot so `that the'insulatorgbodyis ynot* subjected to -'theiull`iorce of the expansiom -Similarlythe 1 zthimble being slightly-compressed in the bore `'as initially introducedfthereinto,` the shrinkage of 'ff-the Aoliametrical'- dimension of the thimble like- `,--Wise is-compensa-ted. That is, the spring'action f provided bysloti9 and-the initial compression of \.-the thirnble causes the thimbleto remain in close l engagement withf'the bore ofthe insulator in :l spite ofthethermal contraction ofthe thimble. It is to be understood Lthatcompensation to thermal expansion and contraction of-the inusulator-Ipin ltluimble under'wde swings of-atmos- .pheriatemperature can be compensated by slot- .ting the-thimble ofgthe insulator pin-otherwise 70.` `than as shown. andfdescribed. :I have found that ;;the-single longitudinallyextended slot as shown provides in simple l manner. compensation4 s ade- `:quate tapreVent-breakage offtheinsulator or loosening oietheiinsulator. on: ,the insulator; pin

75ucaused lbyexpansion or, contraction of. the `thimv1-ment :pinmay 4be ot any length appropriate to the;Pf

ble. Also, though less desirably, the thimble and shank of the insulator pin may be made of diierent, metals, as for example by elongating and thickening the attaching bolt or stud of ferrous metal or the like, and engaging it with a longitudinally extended skirt or base of the thimble. In any event, however, the thimble is cast of one of the designated light metals and is slotted in compensation for its thermal expansion and contraction.

The insulator pin of my invention thus presents great advantage in avoiding the loss through breakage and deterioration of wooden cobs and the breakage of sleeves composed of lead and the like. It avoids the destructive effects of bringing a metal thimble of an insulator pin as previously composed into direct contact with the insulator by the nature of the metal of which the insulator pin is composed and by the compensation to atmospheric temperature changes provided by the slotted thimble. As noted, the slotted thimble maintains a tight engagement of the insulator with the insulator pin at low atmospheric temperatures and conversely avoids breakage of the insulator by thermal expansion at high atmospheric temperatures.

I claim as my invention:

1. An insulator pin arranged for engagement with cross arms and the like comprising a shank,

and a threaded insulator-carrying thimble cast of one of the light metals or their alloys comprising magnesium and aluminum, said thimble being divided longitudinally therethrough by a diametric approximately parallel-side slot, the slotting of the said thimble compensating for thermal expansion and contraction of the thimble with respect to an insulator supportingly engaged thereby.

2. An insulator pin arranged for engagement with cross arms and the like comprising a shank and a threaded insulator-carrying thimble integrally cast of one of the light metals or their alloys comprising magnesium and aluminum, said thimble being divided longitudinally therethrough by a diametric approximately parallelside slot, the slotting of the said thimble compensating for thermal expansion and contraction of the thimble with respect to an insulator supportingly engaged thereby.

ROGERS CASE.

REFERENCES CITED The follovving references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 779,828 Wood Jan. 10, 1905 2,260,917 Ruggieri Oct. 28, 1941

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