US1868479A - Compensating strut type insulator - Google Patents

Description

July 26, 1932-. v A. o. AUSTlN 1,853,479

COMPENSATING STRUT TYPE INSULATOR Filed April 5, 1950 2 Sheets-Sheet l ATTORNEYSY' July 26, 1932- A. o. AUSTIN 1,

COMPENSATING STRUT TYPE INSULATOR Filed April 5, 1930 2 'Shee ts-Sheet 2 A T T ORNE Y5 tions in temperature and load conditions and Patented July 26:, 1952 UNITED sins FFICE ARTHUR 0. AUSTINZOF NEAR BARBERTON, CHI-3, .ASS IGNOR, BY MESNE ASSIGNMENTS, TO THE OHIO BR-ASS COM'PANY, OF MANSFIELD, OHIO, A CORPORATION OF NEW JERSEY i 1 Application filedApril 5, 1930.

This invention relatesto jointsfor connect ing the parts of insulators and has for its oh j ect the provision of connecting means which shall automatically compensate for variawhich shallbe of improved construction and operation.

The invention is exemplified in the combination and arrangement of parts shown in the accompanying drawingsand described in the following specification, and it is more particularly pointed out in the appended claims.

This application is a continuation in part of application, Serial Number 8,823, filed February 12, 1925.

I In the drawings:

Fig. l is an elevation of an insulator with parts in section showing one embodiment of so the present invention.

Fig. 2 is a view similar toFig. 1, showing a modified form of the invention.

Figs. 3, 4, 5, 6 and 7 are fragmentary sec- .tional views showing other modifications of the invention.

Fig.8 isa sectionon line 8-8 of Fig. 1. Fig. 9 is a section on line 9-9 of Fig. 2.

Fig. 10 is a perspective view of a'compem sating strut member.

In addition to provlding insulation between electrical conductor and ground, an insulator must carry the mechan cal load ima posed by the conductor.

Insulators in general are made up in two parts, a dielectric member and ;a metalllc member for transferring the 'mechanical stresses. In general, there is-a material difference in the linear coefficient of expansion between the metal. and the dielectric for temperature changes. Since the dielectrics are usually fragile materials and are neither malleable nor ductile and have a comparatively low ultimate in tension or shear compared with their strength in compression, it is exceedingly important that a careful control of the mechanical stress set up in the dielectric be effected. If this is not done, the design will be unnecessarily large or, failure may occur under comparatively mild conditions. In transferring the mechanical load,

o'omrnnsa'rine srnnr TYPE INSULATOR Serial No. 441,871.

the distortion of the metal parts under the mechanical load may cause failure ofv the di electric. The insulator as ordinarily constructed may effect a fair compromise, as one factor may tend to offset another. VVheninsulators of large size, however, are reached, thisis likely to become diliicult. This will be seen ;more readily by reference to Fig. 1.

lnl ig. 1, a load applied to the pin 10 and to the cap 11 will set up a resultant stress in theapproximate direction of the line 12, the load being transferred from the bearing surfaces of the pin and cap through the cement 1-3 and the struts 14 and 15. As the load or tension is increased on the insulator through its attachments in the direction of the arrows 1O andll, there is a tendency to compress the dielectric member 16 between the bearing to that of an arch structure, it will be seen that there is a radial component adjacent the. her ing section 17 of the cap tending to press? outward as well as downward If the load ishigh, this radial. component sets up a tangential stress'in' the cap and causes it to expand. For a givenpressure per unit area on the inner surface of he cap, this tangential expansion will be proportional to the diameter of the cap where the cross section.

of the portion of the cap affected remains the same. This follows zfI'CHl the factthat for a unit pressure on the inside of a cylinder, the

tangential tension to which the cylinder wall is subjected per unit length of cylinder will be the pressure per unit area times the diameter divided by 2. From this it follows that. the unit stress on the hoop or band in the circumferential direction is directly propor tional to the diameter. Since the elastic stretch will be'direc tly' proportional to the unit stress and directly proportional to thelen th, it will be seen that as the diameter increases, the length of the band'or hoop will cylindrical body that the elongation of the wall of the cap in a circumferential direction for a given pressure per unit area within the cap will be proportional to the square of the diameter of the cap. Since the circumference is pi times the diameter, it follows that the radial movement will be the circumferential stretch or deformation divided by pi. In

other words, the radial deformation is proportional to the circumferential deformation, hence, the radial deformation increases approximately as the second power of the cliameter where the same pressure exists per.

- a failure in an ordinary arch structure, a

crack started in the dielectric of an insulator is fatal as the ability to carry high voltage would be destroyed by the defect. The failure of the dielectric in an insulator is usually 7 caused by a stress set up by tension or shear or a combination of these stresses rather than by compression. This is due to the fact that the material is usually 8 to 10 times as strong in compression as in tension or shear and it is diflicult to util ze the compressive strength of the material without causing a limiting stress in tension or shear which will destroy the dielectric.

In order to reduce the diametrical expansion of the cap, reinforcing ribs 18 are added. In insulators as ordinarily put out, these reinforcing ribs, while beneficial under heavy loads, may set up a serious stress at low temperatures, particularly where the lead supported islight. Where the load carried by the insulator is light and the temperature is low, there is no resulting component tending to expand the cap and the contraction of the reinforcing ribs and the body of the cap due to low temperature and greater linear coefficient of expansion of the can for temperature changes may increase the bearing stress on the head ofthe dielectric member to the po nt where a zone on the head is caused tofail by a shearing stress. This is usually a maximum where the flared flange joins the cemented head of the insulator. It is evident, then, that where the reinforcing flanges are used which'have a linear coefficient of expansion for temperature changes greater than the dielectric, it'is highly desirable to provide some relief for stresses which may be set up at low temperatures. In addition, if the diametrical expansion can be reduced by the maximember 16 inserted therein.

mum loads, less material will be required and the cost of the article kept down..

Fig. 1 shows one method of accomplishing the desired results. The construction consists of a closed receptacle 19 with a dielectric The intervening space may be filled with Portland cement or other suitable material. The dielectric member may have its efiective bearing surface limited by coating with wax or-suitable yielding material. This is shown at 20. .In addition to the coating, a yielding material or cushioning material 21 is placed on each side of the struts 14.

load or tension is increased on the insulator,

a force in exerted on the ends of the strut members 14 through the cement 13 which fills the space between the strut and cap and also between the strut and the dielectric member. As the load increases, thecap expands owing to the radial component as previously explained. This movement, however, does not affect the dielectric appreciably as the struts 14 assume a more nearly horizontal position, taking up the expansion without permitting an outward movement of the dielectric. In fact, the angularityof the strut may be used to cause a forcing in of the outer surface of the dielectric as the load increases. This may be accomplished by placing the strut in a more nearly horizontal position. It will be seen that this arrangement permits of the expansion of the cap and at the same time holds the dielectric in position so that it will not be cracked by the distortion. A very slight movement will make a very material difference in the mechanical load which may it is evident that when the'cap contracts at low temperatures, the outside of the strut members 14: will be forced in. This will tend to lift the inner ends of the struts without setting up a forcing compression which will.

tend to shear the head of the dielectric from the flange. The cushion or clearance provided by theyielding material 20 permits of the slight amount of actual travel necessary.-

It is seen that where a material benefit is required, the struts must have a sufiicient length and angula-rity compared to their thickness so that their angularity can shift without producing a radial pressure on the sides of the struts. The strut members 14 may be in the form of a continuous or sectionalizedring depending upon the thickness and rigidity of the ring. here relatively thin, these rings may be continuous, but where thick, it is advisable to use them in sections orprovide them with restricted sections so as to reduce their rigidity. Each strut as shown.

is disposed obliquely, across the space hetweenthe confronting faces of tlieconnect-ed parts and the bearing ends of the struts are wider circumferentially of the insulator than they are radially of the insulator, thus preventing lateral tilting of the struts circumferentially of the insulator and restricting them to rotary movement about their ends in directions radial to the insulator so that they will maintain effective connection between the insulator parts notwithstanding relative separation of the parts.

It will be apparent that if the struts werepermitted to tilt laterally upon their end bearings in a direction circumferentially to the insulator, rotation of the connected parts in opposite directions would operate to tilt the struts so that the entire support formed of the several struts distributed about the insulator would collapse, thus destroying the effective. connection between the parts.

Where the struts areconstrained'to rotate in a direction radial of the insulator any increase in the spacing of the connected parts permits the struts to assume a position more nearly normal to the confronting faces so that they continue to span the increased space and thus maintain effective connection and pressure on their bearings irrespective of the variation in the spacing of the confronting faces. The same general method maybe used for transmitting stress to theinner surface of the head of the dielectric. In this case, strut members 22, 23, 24 and 25 are screwed on to a threaded portion 26 of the pin. In order to permit free movement, the space 27 between the strut members is filled with wax or yielding material. Any soft cushioning material which will keep the cement out may be used. Inaddition, the surfaces 28 are coated with yielding material. This is to permit a free angular movement of the strut members 22, 23, 24 and 25. It is not necessary that the whole space 27 be filled with cushioning material, if the sides of the strut members are covered with yielding material as in the case of the struts 14, as the amount of movement is exceedingly small. load, the resulting pressure transmitted from the strut members to the dielectric will tend to cause a compression of the dielectric in accordance with the laws governing the clasticity of materials.

' This will tend to reduce the thickness of thedielectric and unless more than counter acted by an outward radial force, the di- It is seen that under a electric will tendto 'recede' in a radial direction. This tends to permit the cement to shear andthe insulator to fail through the.

breaking of the cement joint. 1 i

As the dielectric member tends to expand due to the resulting forces, it will be seen that this is readily taken upby the. change in angularity of the strut members 22, 23, 24

and 25, as theywill assume a more nearlyv horizontal position increasing their effective.

diameter. This will provide for distortion,

not only in the dielectric member, but inthe. A considerable metal members themselves. gradingin the stress may-be provided by changing the angularity and the length of the strut members. These strut membersfiare preferably in the form of rings which are slotted whenthick in order to permit changein angularity. This construction. not only-' permits-of taking up the deformation of the dielectric and the adjacent material and metallic members, but also permits taking upchanges due to differential expansion or contraction of the dielectric andthe metallic members. members tend to expand, the radial stress will be relieved by the strut members tending to assume aniorenearly cylindrical shape.

Thisforces the pin up into, the closed portion,

of the dielectric, provision being made by the cushioning material 20. At low. tempera thick, it. may be necessary to slot them radi-l allyin order to permit them todeflect more readily. Theflanges may be made so that there is considerable deflection under some conditions which may tend to cause them to crystallize or break loose from the body. This will have no'effect upon the operation providing the location of the flange cannot be shifted. Small projecting beads 32-between the flange struts may be provided so; that the flange cannot strip. over the body of the pin. These flanges may be made in many shapes without affecting the principle involved. W' here they are apart of the main pin body, they are held in placeand assembly is readilyperformed. In order to provide the distributedbearing area and to prevent cement filling the intervening space, a thinsheath 33 preferably of metal may he forced orv spun over the flange struts. The air space 34. then permits free movement of the flanges V It is evident that if the metallic and the strut section will not act as a reinforced concrete member. It is evident that the space 34 may be filled with wax or yielding material or the upper and lower surfaces of the flanges covered with wax or yielding material, which w1ll give the same result as previously explained. The outer ends of the flanges may have a large bearing area or be relatively small depending upon the conditions. WVhcre the outer surface is covered with metal, the load may be distributed on the cement with a comparatively small bearing surface on the flange strut. Struts 35 are interposed in the line of stress between the dielectric member 16 and the inner bearing surface of the cap 36. In order to allow the struts free movement, they are covered with a layer of thin metal 37. This increases the I bearing surface on the cement and allows the 20' free movement of the strut members 35. The strut members may be made in various forms, being continuous, helical or in sections. The angle of the successive ones may vary so as to control the resultant forces as desired. Their size, length and rigidity may be controlled upon which no stress is desired.

In Fig. 7 the strut members are made up with a soft paper or other cushioning material between, the whole mass being held together with'wax or wrapped in any way so that they can be readily inserted in the joint. The metal struts 35 owing to the presence of the cushioning material 40 will be free to move'the necessary amount.

In Fig. 4, the cement struts 41 are used to transfer the load, the spacers 42 being inserted to provide a plane of separation so as to permit the lateral movement without shear. These members 42 may be thin metal coated or may be paper.

longitudinal direction in the joint as they may be large enough to provide actual shearing strength; It is evident that in this case the cracking of the cement does not necessarily mean the mechanical failure of the insulator. It is seen, however, that the general I properties of the joint may be materially changed by the placing of the spacers 42 in order to control the cement struts.

Where a metal or solid insert 42 is used, it is usually necessary to coat it with the yield- VVhere made of g metal, they will prevent a breakdown in. a 55 V Fig. 5 shows one modification in which the compensating struts are shown assembled in several different ways to produce the desired result. In this case the struts bear'directly on the cap at their outer ends. The struts may be secured into place or they may be put in positionbefore the cap is galvanized.

This gives an intimate contact at the outer end and the flexibility of the strut permits the necessary movement for changesin angularity. Free movement for the strut 45 is pro-.

vided by a wax cushion or other yielding material 46. While this permits a free angular change of the strut, the cement 47 is allowed to bear on the end of the strut. Space between the struts may be filled with air as shown for space 48.

-Another method isto coat the surfaces with waxor yielding material 49 allowing the cement 50 to fill the remaining space. The cement be prevented from entering any space by blocking the same off by a layer of foil or paper. Another method of providing the air space is to fill the space with wax or other material which will be melted out later. ax coating 50 may be replacedby any yielding material such as soft paper or cork as the movementin general is exceedingly small.

It is understood in any of the various modifications discussed that full use may be made of the thickness, angularity, cross section, stiffness and the relieving of the struts to control the distribution of stress.

The same general principles that apply in the'cap also apply to the bearing on the'inner surfaces. In order that this can be seen more clearly, reference is made to F 6. In

Fig. 6, the same general arrangement of F ig.

5 is applied to pin 51. 'The struts 52 have their inner ends in contact withthe grooves on the pin. The struts 52 may be separate or in form of a helix. They may simply bear against the pin or may be galvanized in place. Free movement of the struts may be insured by a wax or yielding filling 53, by an air space 54 or by a coating or cushion 55 placed on the surface. i

I claim: ,7

1. An insulator comprising a dielectric member, a fitting connected therewith,and a plurality of struts interposed between said member and fitting and spaced from one another in the direction of the load on said insulator.

2. An insulator comprising a dielectric member, a fitting connected therewith, and a plurality of strut members interposed between saiddielectric member and fitting and distributed along said member and fitting in the direction of the load on said insulator, said members being disposed in different angular positions to control the distribution of force transmitted between said dielectric member and fitting.

, 3. An insulator comprising a dielectric member, a fitting for said member, cement for connecting said member and fitting, strut rings disposed in said cement and spaced from one another, and means for excluding cement from thespaces between said rings.

4. An insulator comprising a dielectric member, a fitting for said member, cement for connecting said member and fitting, and a plurality of strut'bands disposed in said cement, said bands differing from one another in cross section to control the distribution of force transmitted by said strut bands.

5. An insulator comprising a dielectric member, a fitting forsaid member, cement connecting said member and fitting, and strut bands disposed in said cement, said bands differing from one another in cross section and being differently spaced to control the distribution of force transmitted by said bands.

6; An insulatorcomprisinga pair of concentric members arranged one within the other one of said members being formed of dielectric material, cement interposed between said members for connecting said members together, and means embedded in said cement for compensating for variation in-the spacing of said members, said compensating means comprising a plurality of annular strut bands spaced from one'another in the direction of the axis of said insulator parts, the circumferentially distributed portions of'said bands constituting strut elements, each disposed at an oblique angle to the axis of said insulator parts andso inclined that the load on said parts tends to tip said elements in a direction to increase their radial extent, and an envelope enclosing said bands to exclude the cement from the spaces between said bands. 7. An insulator comprising a pair of connected parts one of said parts being formed of dielectric material, cement interposed between said parts and means for compensating for variation in the spacing of said parts,

said compensating means comprising a plu rality of members embedded in said cement and bearing on said respective parts and spaced from one another and movable under the force of the load of said insulator, and an envelope enclosing said members to exclude cement from the space between said members. 1

8. An insulator comprising apair of nested parts one of said parts being formed of dielectric material, cement interposed between said parts and aplurality of separated bands embedded in said cement, said bands bearing at their opposite edges on said parts to transunit the load on said insulatorfromioneof said parts to the'other, said bands having the faces thereof inclined to the axis of said nested parts so that/sections of said bands will tend to tip under the force of the load on said insulator and increase the radial extent of said bands when the load is increased, said bands differing from one another in load transmitting characteristics to control the distribution of stresses in said insulator. 9. An insulator comprising a pair of nested parts one ofsaid parts being 'formedof dielectric material. having cement interposed therebetween, a plurality of bands disposed between said nested parts and enclosed in an envelope to exclude cement from the spaces between said bands, the sections of said bands being arranged to rotate under increased force of the load on said insulator in a direction to increaseJthe radial extent thereoff 10. An insulator comprising. a pair of nested members one of said members'being formed of dielectric material, cement interposed between said members, a pluralityvof circumferentially extending members disposed in said cement and having tiltable or rotatable sections, and jan'jenvelope enclosing said members and expanded by the tilting or rotating of said sections when said nested members are moved by the load on said insulator.

1 1. 'An insulator comprising nested parts having spaced confronting faces, one ofs'aid parts being formed of dielectric material, struts interposed between said parts and having thrust bearing connections at their 0pposite ends with said respective faces, said struts being held by said bearing connections against tilting movement circumferentially of said insulator parts but each strut being rotatable on its bearing connections in a plane radial oflsaid insulator, the spaces at the sides of said struts adjacent theconfronting faces of said insulator parts being open to permit of rotation of saidstruts on their bearing connections when the spacing between said confronting faces is varied, thus enabling said struts to mamtaln effectlve connection between said insulator parts notwithstanding'variations in the spacing of said parts.

12. An insulator comprising nested parts hafvingspaced confronting faces, one ofsaid parts, being formed of dielectric material, struts interposed between said parts and having thrust'bearing connections at their opposite' ends'with'said respective faces, said struts being held by said bearing connections against tilting movement circumferentially of said insulator but each strut being rotate able upon its bearing connectionsin a direction radial to the insulator, cementinterposed between said confronting faces to hold said parts together, the cement being spaced away from the sides of said struts toward the confronting faces of saidinsulator parts to permit of rotation of said struts on their end bearing connections under the force of. the load on said insulator when the spacing between said confronting faces is increased by expansion of the outer insulator part, to maintain effective connection between said parts notwithstanding variation in the spacing thereof.

, 13. An insulator comprising a dielectric member and a metallic fitting therefor disposed one within the other, struts interposed between said dielectric member and fitting and inclined relative tothe axis of said insulator, said struts having thrust bearing connections at their opposite ends with said dielectric member and fitting respectively, said bearing connections being greater in extent circumferentially of said insulator than radially thereof to brace said struts against lateral tilting circumferentially of the insulator while permitting rotation of said struts about said bearingsin directions radial of said insulator, cement interposed between said dielectric member and fitting to hold ,saidmember and fitting together, said cement .b'eing spaced from the sides of said struts toward said dielectric member and fitting to permit rotation of said struts on their end.

bearing connections when the spacing be tween said dielectric member and fitting is varied, to maintain effective connection between said dielectric member and fitting notwithstanding variation in the spacing between said dielectric member and fitting.

14. An insulator comprising a dielectric member, metallic fittings disposed at opposite sides of said dielectric member, struts interposed between each of said fittings and said dielectric members, said struts having thrust bearing connections with said fittings and said member at their opposite ends respectively, said struts being held by said bearing connections against lateral tilting concentrically with the confronting faces .of-said dielectric member and fittings but beingrotatable upon said bearing connections toward andfrom the confronting faces of said dielectric member and. fittings to permit said struts to maintain effective connection'between said member and fittings not withstanding variations inthe spacing between said member andfittings, the space at the sides of said struts toward said member and fittings being open to permitrotation of said struts on their end bearings. ,15. An insulator comprising a cup-shaped dielectric member, metallic fittings disposed respectively Within and without said dielectric member, struts disposed between said dielectric member and fittings and having thrust bearingconnections at their opposite ends with said member andfittings respectively, said struts being inclined relative t0 the axis of said insulator and being held by their end bearing connections against lateral tilting circumferentially of said insulator but rotatable upon said bearing connections in directions radial ofsaid insulator,

at their opposite ends with said respective faces, said struts being held by said bearing connections against lateral tilting movement in'a direction; concentric with said faces but being pivoted on said bearing connections for rotary movement toward and away from said faces, the spaces at the sides of said struts adjacent said faces being open to permit rotary movement of said struts on said end bearing connections whenever the spacing between said faces changes, thus enabling said struts to maintain effective connection between said insulator members not-withstanding variation in the spacing thereof.

17. An insulator for supporting a conducv tor comprising a pair of connected members having spaced confronting faces one of said members being formed ofdielectric material, inclined struts disposed in the space between said faces and having end thrust bearing connections at their opposite ends with said respective faces, said struts being held by said bearing connections from lateral tilting in a direction parallel with said faces but being pivoted on said bearing connections for rotary movement toward and away from said faces, cement interposed be tween said faces for holding said members together, saidcement being spaced away from the sides of said struts adjacent said confronting faces to permit rotary movement of said struts about their end bearing connections whenever the spacing between said faces is varied. 7

18. An insulator comprising a dielectric member, a cap surrounding a portion of said dielectric member, said dielectric member and cap having spaced confronting faces, struts disposed between the confronting faces of said cap and dielectric member and inclined to the axis of said insulator, said struts having thrust bearing connections at their opposite ends with the confronting faces of said dielectric member andcap respectively, said bearing connections being-of greater extent Qircumferentially of said insulator than radially thereof to hold said struts from lateral tilting circumferentially of said insulator while permitting rotary movement upon said end bearing connections in directions radial of said insulator, and cement interposed between said cap and dielectric member, said cement being spaced away from the sides of said strut adjacent said cap and dielectric member to permit rotation of said struts radial of said insulator.

19. An insulator comprising a dielectric member, a fitting connected with said member, cement for securing said dielectric member and fitting together, struts interposed in said cement and having end thrust'bearing connections at their opposite ends with said dielectric member and fitting respectively, for transmitting the force of the load between said member and fitting, and means for excluding the cement from the lateral faces of said strut members to permit variation in their angular position.

20. An insulator comprising a dielectric member, a fitting connected therewith, and a plurality of struts interposed between said member and fitting and spaced from one another in the direction'of the load on said insulator, said struts differing from one another in their load transmitting capacity to control the distribution of the load transmitted between said dielectric member and fitting.

21. An insulator comprising a pair of connected parts, one of said parts being formed of dielectric material, and means for compensating for variations in the spacing of said parts, said means comprising force transmitting members interposed between said parts and having bearing engagement with said parts, said members being movable on said bearing engagement, when the spacing of said parts is changed, to compensate for the change in said spacing, the bearing surface of one of said parts being fragile, and a bearing sheet interposed between said fragile surface and said members to prevent destruction of said fragile surface by the moving of said members thereon.

22. An insulator comprising a pair of connected parts, one of said parts being formed of dielectric material and the other of said parts being formed of metal, means for compensating for variations in the spacing of said parts comprising force transmitting members interposed between said parts and having bearing engagement on said parts, said members and one of said parts being relatively movable under the force of the load on said insulator when the spacing of said parts is changed to compensate for said change, said members being fixed to said metal part.

23. An insulator comprising a pair of connected parts, one of said parts being formed of dielectric material and the other of said parts being formed of metal, means for com pensating for variations in the spacing of said parts comprising force transmitting members interposed between said parts and having bearing engagement on said parts, said members and one of said parts being relatively movable under the force of the load on said insulator when the spacing of said parts is changed to compensate for said change, said members being held tosaid metal part by means of a fusible attaching metal.

24. An insulator comprising a pair of connected parts, one of said parts being formed of dielectric material and the other of said parts being formed of metal, means for compensating for variations in the spacing of said parts comprising force transmitting members interposed between said parts and having bearing engagement on said parts, said members and one of said parts being relatively movable under the force of the load on said insulator when the spacing of said parts is changed to compensate for said change, the bearing surface of said metal part being galvanized and said members being held to said metal part by the galvanizing coating thereof,

25. An insulator comprising a pair of connected parts, one of said parts bemg formed of dielectric materials and means for compensating for variations in the spacing of

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