US2441709A - Strain insulator - Google Patents

Description

May 18, 1948.

G. H. MANKE 2,441,709

STRAIN INSULATOR Filed June 2l, 1945 i f Ml I Ilgml Patented May 18, 1948 George H. Manke, South Milwaukee, Wis.,v assignor to IJne'MateriaiCompany, Milwaukee,.Wis., a corporation offD'elaw/arei Application Jilne 21, 1945, Serial'No. 600,824

(Cl.v 174-176) 3 Claims.

This invention relates to improvements -in a strain insulator for guy Wires-or the' like.

It is common .practice to provide. strain insulators for guy Wires, comprising af-Woodenfbarhaving metal ttings on the end :adaptedior engagement with the ends of guywires. Failure of these insulators to withstand strains imposed thereon is frequent and Amay* be attributed to deterioration of the Wood or its inherent weakness atfthepoints of connection-With the iittings. Many "attempts have heretofore been-made to" provide ttings which strengthen the Woodatthe points ofengagement with the :fittings-.and to. provide'iittings Whichwill not by reason ofltheconnection cause a weakening of the Wood. Theseattemptsehave not been as successful asfdesiredand, attmost, are of a. temporaryvnaturedue` to weatheringV of the wood.

Another weakness `inherent in 'Wooden insulating strain bars is in the fact thatfsomeofVVF the iibers become overloadedy While `others'.` have. not assumed their shareofthestrain, thus ultimately causing the overloaded iibers to fail and thereafter placing an overload on remaining fibers. This condition progresses fromone set `oi bers to another to a point Where the bar ultimately fails by reason of afsplittingzaction rather: than because of the tension forces which itth'eoretically should withstand.

An object of this invention is to provide a Weatherfresistant insulatorbar that has atensiie strength much greaterthan-Wood and including ttings which effectivel-ycounter disruptive forces produced inthe bar when subjected toexcessive stresses.

Another Objectis toprovide'an insulator'bar comprising impregnated laminated material compressed to such densitythat' further; compression will not be effected when subjected` to stresses tending to Withdraw it from its fittings and which will be substantially free from shrinkage.

A further object is to provide an insulator bar comprising impregnated laminated material which will prevent splitting of the bar intermediate the ends thereof and which Will at all points transversely thereof assume a, substantially uniform distribution of tension forces over corresponding cross-sectional areas.

In the drawings:

Fig. l is a fragmentary side view of a strain insulator embodying my invention.

Fig. 2 is a fragmentary top plan view of one of the end ttings and insulator shown in Fig. l.

Fig. 3 is a sectional view taken on the line 3--3 of Fig. 2.

Fig. 4 is a side view of a modified fitting and fragmentary portion ci an insulator bar embodying my invention.

Fig. 5 isa top plan view of the .device shown in Fig.. 4.

Fig. 6Y is a view-showing a modiiiedformvof tting.

The strain rod which I propose to use comprises wood'or fibrous laminations impregnated with .a phenolic resin and compressed to a very dense condition, usually about one-halfof the .original thickness of the wood or ber. The resulting insulator is substantially imperviousfto moisture. not subject to serious deterioration, and-is-not further compressible under the influence of stresses to which it may normally besubjected in use, as Will more fullyl appear hereinafter.

Preferably, the strain insulator rod. I= is rectangular in cross-section so that the maximum available strength of the laminations may` be utilized; As shown in Figs. 1, 2, and 3, theguy iitting's at each end of the insulatorrod comprise a pair of substantially identical members 2. Each member comprises an angle portion 3, one side of which extends beyondrthe other to provide a strainarm 4.'v Corresponding sides ofthe angle portions of the'members are arranged on'opposite sides of therod andthe arms 4 extend therefrom in parallel.

A bolti 5: extends through the longer sides of themembers '-andthe rod I, and nut Gholds the long-ersides in clamped engagementwith the rod'. A'secondbolt I extends through the shorter sides of the members '2 .and the rod I and ismore adjacent to the Vend :of the rod'thany bolt. A nut 8 holds the shorter sides in clamped engagement with" the rod.'

The outer-ends of, the: arms Il supportv` abolt' 9 upon which a grooved; roller; Il) is mounted.` Nut II retains boltS in position.

Theguy. cable,` (notshown) is attached to the strain: insulator' by Vlooping 1 the end around' the roller I0 and clamping it to the body of the cable.

In operation, the strain insulator shown in Figs. 1, 2, and 3 operates as follows: Stresses tending to Withdraw the rod I from the fittings tend to pull the bolts through the material of the rod and to split it in planes paralleling the axes of the bolts. However, splitting yof the rod is effectively prevented by reason of the clamping engagement of the member 2 with the rod, the substantially non-compressibility of the material of the rod, and the inherent strength of the material.

If desired, at least one side of the members 2 may be provided with an arcuate ridge I2 disposed about the bolt receiving hole I3 in the manner indicated in Fig. 6. This ridge serves to penetrate the adjacent surface of the rod I when the member 2 is clamped thereto, thus increasing the holding effect of the members upon the rod.

In Figs. 4 and 5 the rod I is provided adjacent its ends with opposed surfaces I4 and I5 diverging toward the ends. As in the previously described arrangement, the fittings at each end of the rod comprise two identical members I6. Each member is channeled to provide opposed divergent Walls I'I and I8 corresponding to the divergent surfaces I4 and I5, respectively, on the rod. I'he bottom wall I9 of each member extends beyond the channel to provide an arm 28.

Bolts 2I extend through adjacent side walls of the members I6 and nuts 22, threaded thereon, hold the members in clamped engagement with the rod I. A bolt 23 extending through the arms 2U and nut 24 also holds the members I6 in clamped engagement with the rod.

A roller, such as I in Fig. 2, may be mounted between the arms 20 by means of a bolt extending through the coaxial holes 25 in the arms.

In operation, the strain insulator shown in Figs. 4 and 5 operates as follows: When the rod I is subjected to stresses tending to pull the ends from the fittings, the divergent surfaces I4 and I engage the opposed divergent walls II and I8 on the members and prevent withdrawal. The rod, being composed of impregnated, highly compressed material and substantially non-compressible in the arrangement shown, in co-operation with the fittings forms a joint that effectively withstands disruptive forces.

From the foregoing it will be apparent that the strain insulator herein disclosed is reliable in service because of its inherent strength and durability, is simple in construction, is easily and quickly assembled, is comparatively inexpensive, and is manipulated Without diiiiculty when put into use.

I claim:

1. A strain insulator comprising an insulating member of resin impregnated and compressed lamination-s of wood, a pair of fittings attached to said insulator at opposite ends thereof, each of said ttings comprising a pair of angle plates and a plurality of nuts and bolts, each of said bolts extending through each of said angle plates and said insulator member in right-angle relation to each other, said angle plates conjointly forming an expansion limiting means resisting expansion of said ends in two relative right angle directions.

2. The combination with a rod-like insulator of impregnated and compressed laminations of wood having an end rectangular in cross-section and a pair of relatively spaced transverse holes in said end each disposed in spaced relationship to the other longitudinally of said rod 4 and with its axis disposed at right angles to the other and normal to opposed sides of said end, of a tting embracing said end and cornprising two identical interchangeable members, each member including an angle portion pro- 'vided with an aperture each in registry with .one of said holes and an arm extending from said end, bolts extending through said holes and apertures, and nuts on said bolts clamping corresponding sides of said members to corresponding opposed sides of said ends.

3. In a strain insulator, the combination with an elongated substantially impervious non-compressible insulating rod having an end of rectangular cross-section, said end having a pair of transverse apertures each spaced longitudinally of said rod relative to the other and having its axis normal to the axis of the other, said opertures each with its axis normal to opposite sides of said end, of a fitting embracing all sides of said end and including a pair of substantially identical members, each member having side portions in right angle relationship and contiguous to corresponding sides of said end, one of said side portions extending beyond the other and beyond said end to form a strain arm, the strain arm of each member being in parallel relation to the other and spaced therefrom, each of said side portions having an aperture in alignment with the transverse aperture in theY side of said end contiguous thereto, bolts extending through said apertures, and clamping nuts on said bolts holding corresponding sides of'said members in clamped relationship to said end, said members embracing all sides of said end and jointly opposing expansion of said endv in' each of two relative right angle directions.

GEORGE H. MANKE.

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

UNITED STATES PATENTS f Number Name Date 1,640,433 Weldon Aug. 30, 1927 1,654,286 Frost Dec. 27, 1927 1,717,287 Warren et al June 11, 1929 1,782,790 Miller et al Nov. 25, `1930 1,815,598 Stroup July 21, 1931 1,823,977 Hendee Sept. Y22, 1931 1,972,615 Austin Sept. 4, 1934 2,336,324 Warren Dec. 7, 1943

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