US3309047A - Stand-off insulator bracket - Google Patents

Description

March 14, 1967 .1. w. KANE STAND-OFF INSULATOR BRACKET Filed Aug. 29, 1966 R O T N E V m KANE United States Patent York Filed Aug. 29, 1966, Ser. No. 575,793 Claims. (Cl. 248-65) This is a continuation-in-part of application Ser. No. 349,970, filed Mar. 6, 1964.

The present invention relates to a stand-off insulator bracket used for mounting power line insulators on poles.

It is an object of the present invention to provide a highly efiicient stand-off insulator bracket formed of a suitable rigid, strong, durable di-electric material, preferably a fiber glass reinforced molded resin.

It is a further object of the present invention to provide stand-off insulator brackets capable of attachment directly to a pole and dimensioned to provide, without the use of a cross arm, adequate spacing between power lines conforming at least to code minimums.

It is a further object of the present invention to provide a stand-01f insulator braokethaving a support arm the upper surface of which is transversely curved to facilitate the action of precipitation in cleaning and, removing contamination therefrom.

It is a further object of the present invention to provide stand-off insulator brackets formed of a plastic or resin di-electric material effective to eliminate fire hazard due to formation of relatively dry shadow areas which results from the use of wooden cross arms.

It is afurther object of the present invention to provide a reinforced plastic or resin stand-off insulator bracket characterized in the provision of a support arm and bracing portion adapted to provide full rigidity of the bracket when mounted on a pole.

'More specifically, it is an object of the present invention to provide a reinforced plastic or resin stand-01f insulator bracket having a substantially horizontally extending arm portion having one end adapted to be affixed to a pole, a downwardly and slightly outwardly inclined insulator support portion, and a downwardly and inwardly extending bracing portion having an end adapted to be aflixed to a pole.

It is a still further object of the present invention to provide a stand-off insulator bracket formed of a reinforced resin having a laterally extending arm portion and a .generally laterally extending but inclined bracing portion connected to an intermediate insulator support portion.

It is a further object of the present invention to provide a bracket as described in the preceding paragraph in which the insulator support portion is inclined slightly from the vertical so as to mount an insulator with its longitudinal axis extending slightly upwardly from a horizontal plane.

It is a further object of the present invention to provide a bracket specially adapted for use at opposite sides of a pole to provide spacing between power lines carried thereby equal at least to the thickness of the pole, twice the effective lateral extension of each of said brackets, and substantially twice the effective length of insulator bodies carried by said brackets on which said lines are mounted.

Other objects and features of the invention will become apparent as the description proceeds, especially when taken in conjunction with the accompanying drawing, illustrating preferred embodiments of the invention, wherein:

FIGURE 1 is a side elevation of the stand-off insulator bracket aflixed to one side of a pole.

FIGURE 2 is a plan view of the insulator bracket shown in FIGURE 1, a portion of the pole being shown in section.

FIGURE 3 is a front elevational view of the bracket shown in FIGURE 1.

FIGURE 4 is a fragmentary sectional view on the line 4-4, FIGURE 1.

FIGURE 5 is a view of an insulator bracket attached to a pole and having the insulator mounted thereon.

FIGURES 6 and 7 are fragmentary elevational views illustrating different arrangements of the stand-off insulator mounting brackets on poles.

The stand-off insulator bracket 10 comprises a horizontal support arm 12, a downwardly and slightly outwardly inclined insulator support portion 14, and an inwardly and slightly downwardly inclined brace arm 16. At its inner end the arm 12 is provided with an upwardly extending portion 18 which is transversely curved as seen in FIGURE 1 to conform generally to the outer circumference of a food pole 2E). The brace arm 16 at its inner end includes a similar downwardly extending portion 22 also curved to conform to the curvature of the pole 20. The portions 18 and 22 are aflixed to the pole by suitable means such for example as through bolts 24, or the like. The insulator support portion 14 as best seen in FIGURE 5, carries the usual insulator 26 which is shown as attached thereto by a stud 28 carrying a nut 30, the stud passing through the opening 32 best seen in FIGURE 3. The insulator has an insulating body formed of a suitable insulating material, usually porcelain.

The horizontally extending arm portion .12 is provided with an upper surface which is transversely curved as best indicated at 34 in FIGURE 4. This has the primary effect of providing a surface which is maintained substantially clean and free of contaminants as a result of the action of rain. This in turn tends to eliminate leakage flow across the bracket. Where the horizontal arm 12 is provided with the upwardly transversely convex surface 34 by thickening the arm, as best seen in FIGURE 4, it will of course be apparent that additional strength and rigidity is imparted to the arm. If desired, the upper surface of the bracing portion or arm 16 may also be given a transversely upwardly convex curvature as best indicated at 38 in FIGURE 4. In this case the lower surface of the bracing arm 16 is indicated at 40 as transversely concave, resulting in the formation of a strap portion of substantially uniform thickness from edge to edge.

A prime purpose of the stand-01f insulator bracket disclosed herein is to mount power lines to poles, particularly wooden poles of the type illustrated at 20. In many cases the power lines which are secured to the insulators are three phase lines which desirably are spaced from each other to form an equilateral triangle. By using the present stand-off insulator brackets two lower power lines may be provided at either side of the pole 20 and a third insulator attached directly to the top of the pole so that the insulators are disposed at the corners of an imaginary equilateral triangle, as best illustrated in FIGURE 6. This avoids the necessity of cross arms and provides an economical mounting for power lines in an efiicient manner on inexpensive conventional wooden poles.

Alteratively of course, the brackets may be employed to locate two power lines at one side of the pole and the third line at the opposite side of the pole, as best seen in FIGURE 7. The brackets are furthermore dimensioned so that, taking the width of the pole and the dimensions of the insulators 26 into account, the power lines will be laterially spaced apart a distance suflicient to permit a lineman to move between power lines at the opposite side of the pole to obtain access to a power line located upwardly therefrom. Similarly, it will of course be apparent that if desired, a plurality of threewire lines may be supported from a single pole by the use of the stand-off insulator brackets described herein.

In either of the above mentioned installations it will be apparent that the horizontal spacing between the power lines carried by insulators on the bracket Ill at opposite sides of the pole 20 will be separated horizontally by a distance equal to the thickness of the pole plus twice the effective lateral extension of one of the insulator support brackets, plus substantially twice the length of each of the elonagted insulators 26.

Another advantage of the present construction is that the insulators 26 are separated from the pole 20 by the stand-off insulator bracket, which itself is formed of a solid rigid insulating material which is therefore free of any tendency to absorb moisture or water from the air so as to reduce the resistance to leakage current from high voltage lines connected to the insulators.

The foregoing further avoids fire hazard which has heretofore extisted as the result of wooden cross arms for supporting the power line insulators. Since the wood of the cross arm absorbs moisture from the air and from precipitation, situations develop where a substantial flow of leakage current is present in the cross arm. Where the cross arm joins the pole there is often an area, referred to as the shadow area, which is protected from precipitation and hence is relatively dry and offers increased resitsance to the flow of current. These shadow areas are known to be the source of fire damage as a result to spark-over where the leakage flow of current passes over the relatively dry high resistance shadow areas.

The stand-off insulator brackets are designed to have exceptional strength, due not only to the geometric configuration but also to the material employed. Specifically, the reinforced resin of which the insulator brackets are completely formed, is preferably a fiber glass reinforced resin, either thermo-setting or thermo-plastic resin of known type. Excellent results have been obtained when the resin employed is a polyethylene or epoxy resin, containing the usual fillers such for example as clay. Preferably, the resin also includes conventional fire retardants. The fiber glass reinforcement of the resin is preferably provided in the form of a long bundle in which the glass fibers are of maximum length and extend longitudinally of the bundle. In some cases the fibers may be inter-matted to some extent or alternatively, the bundle may be given body by the provision of transversely extending filaments or elements which may be of glass or other type fibers. In practice, this bundle is passed through a bath of the liquid resin and fully impregnated, the excess liquid resin being removed by convention-al means such for example as light rollers between which the imprednated bundle passes as it emerges from the bath and is flattened thereby.

The brackets are molded to the shape shown and for this purpose there is preferably provided a twopiece mold, one formed to shape the outer surface of the bracket and the other formed to shape the inner surface, the two mold sections having edge portions formed to shape the edges. In order to fill the mold for curing the resing impregnated fiber glass bundles are cut to the appropriate length and placed in one of the mold sections.

With the foregoing method of providing the resin impregnated fiber in the molds, it will of course be apparent that a large proportion of the volume of the insulator bracket is fiber glass. In fact, the bracket may be considered basically as formed of resin impregnated fiber glass. In practice the glass fibers may occupy as much as 85% by volume of the material, and in any case, the proportion of glass fibers should not be less than 30% by volume.

In practice, a number of bundles are employed, as for example eight to twelve, in order to provide sufiicient material to fill the mold. It is to be noted particularly at this time that the material thus placed in the mold is characterized by substantially uniformly dispersed long glass fibers shaped to extend longitudinally of the various strap portions of the bracket.

Thereafter, the mold is closed and the resin cured by conventional means depending upon the nature of the resin. As is well understood, some resins are thermally cured whereas others may be therm-o-setting. In the present case preference is given to thermal curing resins of the type described above.

Preferably, the portion 14 of the bracket provided with the openings 32 for receiving the threaded insulator fastening element is provided with a shallow boss 42 to provide an accurately shaped fiat surface for receiving a washer interposed between the bracket and the nut 30 and to prevent interference between the edges of the washer 44 and the arm portions 12 and 16 of the bracket.

It has been found that the provision of the elongated glass fibers as described herein increases the strength of the insulator bracket by a very substantial amount. However, it is to be understood that it particularly great strength is not required, then the glass fibers may be provided with less attention to orientation longitudinally of the strap portions of the bracket. For example, significant improvement over unreinforced resin is obtained when chopped fibers are employed and the strength characteristics improve as the length of the chopped fibers increases. Good results are also obtained when asbestos fibers are incorporated in addition to the glass fibers.

It has been noted that when an insulator bracket as described herein employing the elongated glass fibers is fractured as for example by a falling branch, the glass fibers in many cases are effective to hold the parts together even though the resin or plastic material has completely fractured.

By way of example, excellent results have been obtained when the strap or elongated portions of the insulator bracket have a width of approximately three inches, a thickness of approximately one-half inch at the edges, the horizontal portion 12 being thickened to approximately five-eights of an inch at the intermediate surface portions 34 thereof. The horizontal distance from the vertical flanges or port- ions 18 and 22 to the centerline of the opening 32 may be approximately nine and onehalf inches. The center lines of the openings receiving the bolts 24 may be approximately twelve inches. In any case, all portions of the bracket are preferably of the same width throughout and the width to thickness ratio of the arm portion is at least 5:1. The width of the bracket measured from edge to edge is at least two inches. With these dimensions a bracket having adequate strength requirements for the environment is provided while retaining in full the required rigidity as well as the electrical properties demanded of it. As previously mentioned, these dimensions of the stand-off insulator bracket provide for horizontal spacing between power lines in excess of 30 inches which is the minimum code spacing permitting a lineman to climb between adjacent lines.

It will be observed from the drawing that the brace arm 16 is disposed substantially at right angles to the insulator support portion 114 and that the insulator support portion 14 is inclined at a minor angle, specifically, about 17 /2 degrees, from the vertical so that the brace arm 16 is disposed at a corresponding minor angle to the horizontal. As a result of this the axis of the elongated insulator body 26 is of course disposed to extend generally outwardly of the pole but at an outward and upward inclination, making a minor angle'with the horizontal.

It will further be observed that all portions of the bracket, including the arms 12 and 16, the insulator support portion 14, .and even the general configuration of the transversely curved feet portions 18 and 22, are of a cross-section throughout in which the width is at least several times the thickness, and as previously described, the width to thickness ratio is preferably at least 5:1.

As described in the foregoing, the insulator brackets disclosed herein are particularly efificient because of strength, rigidity, economy in production and installation, electrical efiiciency in operation, and because they lend themselves particularly to a generally acceptable location and spacing of threewire power lines without employing cross arms.

The drawing and the foregoing specification constitute a description of the improved stand-off insulator bracket in such full, clear, concise and exact terms as to enable any person skilled in the art to practice the invention, the scope of which is indicated by the appended claims.

What I claim as my invention is:

1. An elongated insulator body having means for attaching an electrical conductor thereto intermediate the ends of the body, a stand-oil? insulator bracket adapted to be mounted to a side of a pole to extend laterally therefrom, said bracket being an elongated continuous member having a tranverse cross-section throughout whose width is at least several times its thickness, and disposed with the said width dimension horizontal, said bracket consisting of a pair of vertically spaced outwardly extending arms having means at their inner ends for attachment to the side of .a pole, and a generally upright insulator support portion intermediate the outer ends of said arms, said bracket being formed entirely of electrically insulating material, the upper surface of the upper one of said arms being transversely convexly curved to facilitate removal of contaminants by precipitation, said insulator body being secured at one end to the outer surface of said insulator support portion to extend generally outwardly therefrom.

2. An elongated insulator body having means for attaching an electrical conductor intermediate its ends, a stand-oif insulator bracket formed entirely of electrically insulating material and consisting of a substantially horizontal support arm adapted to extend outwardly from a vertical support such for example as a pole, a downwardly and slightly outwardly inclined insulator support portion at the outer end of said arm, said insulator body being mounted with one end engaging the outer side of said insulator support portion and extending outwardly and slightly upwardly therefrom, an inwardly and slightly downwardly inclined brace arm extending from the lower end of said insulator support portion, and generally vertically extending feet at the inner ends of said support and brace arms for attachment to the vertical support.

3. The combination defined in claim 2 in which the upper surface of said support arm is transversely convexly curved to facilitate removal of contaminants by pre cipitation.

4. The combination defined in claim 2 in which the upper surfaces of said support arm and brace arm are transversely convexly curved to facilitate removal of contaminants by precipitation.

5. The combination defined in claim 3 in which the support arm, the insulator support portion, the brace arm, and the two feet are all of the continuous general strap configuration, having a transverse cross-section in which the width to thickness ratio is at least 5:1.

6. An insulator support bracket formed entirely of electrically insulating material for attachment to the side of a pole to extend laterally therefrom, said bracket being an elongated continuous member having a transverse cross-section throughout whose width is at least several times its thickness, and adapted to be secured to a pole in position such that its said width dimension is horizontal, said bracket consisting of a pair of vertically spaced outwardly extending arms having means on their inner ends for attachment to the side of a pole, the upper surface of said upper arm being transversely convexly curved to facilitate removal of contaminants by precipitation, and a general upright insulator support portion intermediate the outer ends of said arms, said insulator support portion having means for supporting an elongated insulator body at the outer side thereof with its axis extending generally outwardly therefrom.

7. An insulator support bracket for attachment to the side of a pole to extend laterally therefrom, said bracket having a substantially horizontal support arm having means at its inner end for attachment to the side of a pole, an insulator support portion at the outer end of said support arm extending downwardly therefrom and inclined outwardly at a minor angle from the vertical, means on said insulator support portion engageable with one end of an elongated insulator body, a brace arm extending inwardly from the lower end of said insulator support portion and inclined downwardly at a minor angle from the horizontal, means at the inner end of said brace arm for attachment to the side of the pole below the attachment thereto of the inner end of said support arm, said bracket being formed in its entirety of an insulating material of generally strap configuration having a cross-section in which the width to thickness ratio is at least 5:1, and in which the width dimensions of all por tions of said bracket extend horizontally.

8. A bracket as defined in claim 7, the upper surface of said support arm being transversely convexly curved to facilitate removal of contaminants by precipitation.

9. In combination an elongated insulator body and a stand-off insulator mounting bracket assembly adapted to be mounted in pairs at opposite sides of a pole to provide spacing between power lines carried by the insulator bodies of said assemblies at least equal to the thickness of the pole plus twice the effective lateral extension of said brackets and plus substantially twice the effective length of said insulator bodies, said bracket being a one-piece integral body consisting of a pair of vertically spaced outwardly extending arms having means at their inner ends for attachment directly to a pole at one side thereof and a generally upright insulator support portion connecting the outer ends of said arms, means on said insulator support portion to mount an elongated insulator body thereon, said insulator body being mounted with one end thereof secured to the outer surface of said support portion to extend lengthwise generally outwardly therefrom and from the pole on which said bracket is mounted.

10. The combination as defined in claim 9 in which said racket is an elongated continuous member having a transverse cross-section throughout whose width is at least several times its thickness, and arranged with its width dimension horizontal when mounted on the side of a pole.

11. The combination defined in claim 10 in which the upper arm is substantially horizontal, and the lower arm is slightly inclined downwardly and inwardly toward the pole from the end thereof connected to said support portion.

12. A stand-oft insulator mounting bracket adapted to be mounted in pairs at opposite sides of a pole to extend laterally therefrom and to support elongated insulator bodies to extend lengthwise generally outwardly from the outermost part of said brackets to provide a spacing between power lines carried by said insulator bodies at least equal to the thickness of the pole, twice the effective lateral extension of one of said brackets, and substantially twice the effective length of one of said insulator bodies, said bracket consisting of a pair of vertically spaced outwardly extending arms having means at their inner ends for attachment directly to a pole at one side thereof, and a generally upright insulator support portion connecting the outer ends of said arms, means on said insulator support portion to mount an elongated insulator body thereon with an end of the insulator body secured to the outer surface of said support portion to extend lengthwise genera-11y outwardly therefrom and from the pole.

13. The bracket defined in claim 12 in which said bracket is an elongated continuous member having a transverse cross-section throughout whose width is at least several times its thickness, and arranged with its width dimension horizontal when mounted on the side of a pole.

14. The bracket as defined in claim 13 in which the upper arm is substantially horizontal, and the lower arm is slightly inclined downwardlyy and inwardly toward the pole from the end thereof connected to said support portion.

15. The bracket as defined in claim 14, said insulator support being inclined downwardly and outwardly at a small angle from the vertical to provide a slight upward and outward inclination from the horizontal of an elongated insulator body mounted thereon.

References (Iited by the Examiner UNITED STATES PATENTS 809,743 1/1906 Petery 174-149 1,193,602 8/1916 Peirce 248--300 1,725,228 8/1929 Trescott 20048 1,866,104 7/1932 Heim 24867.7 2,996,277 8/1961 Hoffman 248--22l FOREIGN PATENTS 201,274 5/1955 Australia.

CLAUDE A. LE ROY, Primary Examiner.

K. I. WINGERT, Assistant Examiner.

Claims (1)

1. AN ELONGATED INSULATOR BODY HAVING MEANS FOR ATTACHING AN ELECTRICAL CONDUCTOR THERETO INTERMEDIATE THE ENDS OF THE BODY, A STAND-OFF INSULATOR BRACKET ADAPTED TO BE MOUNTED TO A SIDE OF A POLE TO EXTEND LATERALLY THEREFROM, SAID BRACKET BEING AN ELONGATED CONTINUOUS MEMBER HAVING A TRANVERSE CROSS-SECTION THROUGHOUT WHOSE WIDTH IS AT LEAST SEVERAL TIMES ITS THICKNESS, AND DISPOSED WITH THE SAID WIDTH DIMENSION HORIZONTAL, SAID BRACKET CONSISTING OF A PAIR OF VERTICALLY SPACED OUTWARDLY EXTENDING ARMS HAVING MEANS AT THEIR INNER ENDS FOR ATTACHMENT TO THE SIDE OF A POLE, AND A GENERALLY UPRIGHT

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