US2500927A - Insulator pin - Google Patents

Description

R. CASE INSULATOR PIN March 21, 1950 Filed May 15, 1947 D fi l [NVEIYTOR Jagger? Case Patented Mar. 21, 1950 INSULATOB PIN Rogers Case, Orange, N. J., assignor to Transandean Associates, Inc., New York, N. Y., a corporation of Delaware Application May 13, 1947, Serial No. 747,807

2 Claims.

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 pole line installations of communication systems and like electrical wire lines.

In previous practice such insulator pins have been made of steel, iron or the like and 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 engagin 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 pm.

I have discovered that insulator pins may be composed of bodies and heads made integral by casting magnesium or a magnesium alloy such as a magnesium containing a relatively small percentage of aluminum, or aluminum or one of the well known 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 respectively preponderate. In casting these light metals, the operation is performed by die-casting or other permanent-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 desirably of 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, but

most desirably is integrated in the pin structure by being cast into 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 and particularly the former 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.

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. 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, under slight blows which would not destroy an unscored insulator body or even under the eifect of vibration. Wooden cobs are also separate elements which require an additional and careful operation in mounting them on the insulator pins.

Not only are the corrosion-resistant properties of magnesium, aluminum and their alloys 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 material of insulators mounted on the pins is provided by the fact that magnesium and aluminum and a Wide range of their alloys are much softer than iron, steel and the like heavy structural metals. Thus, my insulator pins are usable without a lead sleeve or other cushioning means on the head of the insulator pin so that the metal of the insulator pin is in direct contact" with the substance of the insulator throughout the threaded engagement between the pin and the insulator, if the insulator is composed of a suitable non-vitreous material. or if the location of use of a glass insulator is consistent with such omission.

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 insulator pins. Deflection tests under equal loads show that the resistance of the magnesium pins, the aluminum pins and the steel pins initiall are almost equal. Because, however, the steel pins deteriorate by corrosion, over long periods of time the pins composed of the light metals promise greater serviceability in maintaining accurate alignment and spacing of the line wires.

For this reason I cast as integral structures the bodies and threaded heads, or thimbles of insulator pins from one of the light metals which include magnesium and aluminum as above defined. With the body of this structure the threaded shank of the insulator pin, which is of metal such as steel or iron possessing greater shear-resistance than that of the light metals, is integrated during the casting operation or in other suitable manner. I

In the accompanying drawings:

Fig. l is an elevational view of one form of my insulator pin, indicating in broken lines the pres ence of an insulator mounted on the pin.

Fig. II is a plan View of the insulator pin shown in Fig. I, indication of an insulator mounted on the pin being omitted.

Fig. III is an elevational view of a modified form of my insulator pin indicating in broken lines the presence of an insulator mounted on the pin.

Fig. IV is a plan view of the insulator pin shown in Fig. III, indication of an insulator mounted on the pin being omitted.

Fig. V is an enlarged cross sectional View showing the integration of a threaded shank with the body of the insulator pin, the structure shown in Fig. V being appropriate to both forms of the pm.

Referring to the drawings, the insulator pin shown in Fig. I comprises a body having an upper region I which is circular in cross section, a lower squared region 2 and an extended circular flange or foot 3. Extended downwardly from the body of the insulator pin there is an attaching shank 4, which in accordance with common practice is shown threaded to carry a nut 5. At the upper end of the body of the insulator pin and rising from a collar 6 thereon there is an upwardly tapered head I having relatively sharp threads 8 cut perpendicular to the taper of the head.

Insofar as above described, this insulator pin is of conventional form and is of a sort to which a lead sleeve or thimble commonl is applied around the head of the pin to lie between the head and the surface of the insulator bore. It is to be understood, however, that this pin is a casting composed of a light metal as above defined and that no lead sleeve or thimble is interposed between the head of the insulator pin and the indicated insulator Hi.

It has been the experience of large users of steel insulator pins of the form shown in Figs. I and II in conjunction with lead sleeves, threads or inserts on the heads of those pins that enduring protection is not supplied by the lead elements. In most communication lines and light and power lines the insulator assemblies are subjected to vibration which may in many instances be continuous or frequently repeated. Thus when the insulator assemblies are mounted on bridges, along railway tracks, adjacent street railway lines, adjacent power generating machinery and the like, periods of vibration are frequent. The vibration is particularly marked when cross arms carrying insulator mounting assemblies are mounted directly to the structure of bridges over which traffic is substantially continuous. Under such circumstances vibration causes the protective lead sleeves, threads or inserts to become crystallized and pulverized so that their ability to protect the insulators is lost. In fact the condition is worse than if no protective element were interposed between the insulator pin and the insulator head, because disintegration of the lead leaves the insulator loose on the head of the pin and particularly susceptible to breakage by shocks, jars and vibration.

Referring now to Figs. III and IV inclusive of the drawings, the modified form of insulator pin therein shown comprises a similarly composed and integrally cast body having a region H which is circular in cross section, a squared region l2 and a circular flange or base it. From the flange or base l3 there extends an attaching shank l4 equipped with a nut Hi. It will be noted in Fig. III of the drawings that the body of the pin is relatively short with respect to the length of the body of the insulator pin shown in Fig. I and that the head 16 of the insulator pin is elongate with respect to the head 1 of the insulator pin shown in Fig. I and is of greater cross sectional area. Head 16 is tapered upwardly and the thread I! cast on the head is a square-face, or approximately square-face, thread. This modification in the insulator pin gives what is in effect an integrally cast cob, corresponding in form to the wooden cobs commonly in use, to which the insulator l8 indicated in Fig. III is applied. Fig. III shows the insulator (8 in direct contact with the head of the insulator pin, this being a suitable arrangement if the insulator is composed of hard rubber, porcelain or other suitable non-vitreous material or if a glass insulator is to be mounted in a location of use in which wide temperature swings or mechanical impacts are not to be anticipated.

The elimination of wooden cobs mounted on the insulator pins directly to engage in the bore in the insulator is a great advantage. Thus wooden cobs not only represent a substantial item of additional expense but the application of the cobs to the insulator pins without breakage is a dificult operation and even with care the percentage of broken cobs is high.

Referring now to Fig. V of the drawings, that figure shows the integration of an attaching shank with the body of the insulator pin. Inasmuch as this shank and its integration apply equally to both modifications of the insulator pin as shown respectively in Figs. I and II inclusive and in Figs. III and IV, the body of the insulator pin is designated by letter of reference A and the shank by letter of reference B. As shown,

the upper region B of the shank extends contrally upward into the body of the insulator pin from the base A of the pin and in this specific. exemplification is integrated with the body of the pin by casting the body around the upper region B of the shank. As shown, region B of the shank has a relatively smooth surface, but if desired for purposes of firmer engagement with the body of the insulator pin it may be provided with surface ridges, scoring or indentations. If;

desired, other means may be employed for integrating the shank of the insulator pin with the body of the pin. Thus it may be engaged with the body of the pin by threading, by Welding or the like.

The reason I employ for the shank of the pin an initially separate body which is integrated with the body of the insulator pin, is in order that the shank may be composed of steel, iron or the like suitable metal having shear resistance per unit of cross sectional area greater than that of the light metal of which the body and head of the pin are composed. Because the shank of the insulator pin engages the pin, and the insulator which it carries to the cross arm of a line pole or analogous structure and is subjected to the transverse thrust of a line wire, it usually is desirable to provide in this region of the pin structure shear resistance greater than would be provided by an equal cross section of the light metal. It should be understood, however, that if a proposed use of the insulator pins is such as not to require a high order of shear resistance in the threaded shank of the pin, that shank may be cast of onepiece with the body and head of the insulator pin.

It will be noted that the organization of both modified forms of the insulator pin as herein shown are what is known as short-shank insulator pins, adapted for use on a metal cross arm, plate, or like supporting structure of moderate thickness. Without structural change other than. in the extended length of the shank, the insulator pins may be what is known as long-shank pins adapted to mounting on wooden cross arms of greater thickness.

It is to be understood that as'the bodies and heads of the insulator pins are cast by the die or other permanent-mold casting operations appropriate to the light metals, the threads are cast on the heads of the insulator pins in the same operation. The threads as so cast are clean out and smooth so that no machining operation is required to true or smooth them and even a polishing operation usually may be omitted. Because of the inherent corrosion resistance of the metal of which the pins are composed it is unnecessary to apply to them any coating for the purposes of corrosion protection. When therefore the coating of cushioning material is omitted, it is unnecessary to apply to the threaded heads of the insulator pins any coating, as by galvanizing, which serves to roughen the surface of the threads and to score the bodies of the insulators.

I have above illustrated two specific forms of insulator pins embodying the fundamental fea tures of my invention and it is to be understood that while adhering to those fundamental features numerous changes in the form and relative regional arrangement of these pins may be made within the bounds of my invention as defined in the appended claims.

I claim as my invention:

1. An insulator pin comprising a relatively light non-corrosive body and threaded insulator-engaging head integrally cast of one of the light metals or alloys thereof comprising magnesium and aluminum, and an attaching shank of a metal having greater shear resistance than the light metals engaged with the insulator body and extended from the base thereof.

2. An insulator, pin comprising a relatively light non-corrosive body and threaded insulatorengaging head integrally cast of one of the light metals or their alloys comprising magnesium and aluminum, and an attaching shank extended from the base of the insulator pin body.

ROGERS CASE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 297,699 Klein Apr. 29, 188% 910,799 Edmiston Jan. 26, 1909 1,562,836 Kyle Nov. 24, 1925 1,603,003 Ennis Oct. 12, 1926 1,682,590 Austin Aug. 28, 1928 1,797,238 Lemont Mar. 2 1, 1931 2,228,804 Adams Jan. 14, 1941 2,260,917 Ruggieri Oct. 28, 1941 2,297,600 Williams Sept. 29, 1942 2,345,404 Mack Mar. 28, 1944

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