US2175336A - Safety core insulator - Google Patents

Description

A. O. AUSTIN SAFETY CORE INSULATOR Filed June 18, 1936 3 Sheets-Sheet 1 g I T744750 to? 01F F4JP/c 2 I4 WWW TPEAT (aka a? mwmm / WNW IPE47E0 c 020 0/? F4 a FIG 0a. 10, 1939. A, o, AUsTlN 2,175,336

SAFETY CORE INSULATOR Filed June 18, 1936 3 Sheets-Sheet 2 Fig.|6.

lNVENTOR 'mocwzi Oct. 10, 1939. O ug-rm 2,175,336

SAFETY CORE INSULATOR Filed June 18, 1936 3 Sheets-Sheet 3 Fig. l7.

Fig..l9.

INVENTOR Patented 0a. 10, 1939 UNlTED a STATES PATENT OFFICE SAFETY CODE INSULATOR Arthur 0. Austin, near Barherton, Ohio Application June 18,

4 Claims.

In the transmission of power and in the insulation 01' radio stations there is need for insulators of high strength and mechanical reliability, and having good electrical properties. Desirable mechanical and electrical properties may be obtained by making up an insulator having an outer sleeve such as glass or porcelain which will withstand leakage current and weathering but which may carry little or no mechanical load, together with an internal member which sustains the mechanical load particularly where this load is in tension. Insulators of this general type heretofore have been used but they are large and costly, consequently their use is restricted. The previous methods of gripping the internal tension member require rather large and costly heads. -7 a One of the objects of my invention is to provide an improved type of construction which-simplifies the mechanical construction and reduces the size, weight and cost of the insulator.

vAnother object is toprovide a construction which will have improved mechanical reliability.

Another object is to provide an improved tension member and method of attaching same.

Other objects and advantages will appear from the following specification and will readily suggest themselves to those skilled in the art..

. The invention is exemplified by the oombina tion and arrangement of parts shown in the accompanying drawings and described in the following specificationand it, is more particularly pointed out in the appended claims.

In the drawings:

Figs. 1, 4 7, 8, 11, and are longitudinal sections of insulators showing difi'erent embodiments of the present invention.

Figs. 2, 5, 9, 12, and on lines 2-2, 5-4, of Figs. 1, 4, 8, 11, and 20 respectively.

21 are transverse sections Fig. 3 is a fragmentary longitudinal section at right angles to the section shown 11112;. 1.

Fig. 6 is atransverse section on 1 H oi Fig. 4 but showing the addition of a filler.

Fig. 10 is a side elevation of apparatus for forming reinforcing links.

Figs. 13, 15, 1'7, and 19 are elevations, partly in section showing other forms of the invention.

- Fig. 14 is a plan view of Fig...l3.-

Figs. 16 and 23 are elevations, respectively, of other forms of the invention.

Fig. 18 is a transverse section on line Il-IB of Fig. 17.

Fig. 22 is a transverse section, similar to Fig. 21, of a modification of the invention.

a-s, 12-12, snarl-2|,-

1936, Serial No. 85,948

Fig. 24 is a transverse section of the member I28 on line 24-24 in Fig. 23. v

Fig. 25 is a transverse section of the member I29 on line 25-2i in Fig. 23.

Fig. 26 is a transverse section, similar to Figs. 5 24 and 25, of a modification of member I29 in Fig. 23.

In the form of the invention shown in Figs. 1, 2 and 3 the outer jacket III is held between heads II having attaching ears I2. Gaskets II are pro- 10 vided so that oil or other insulating medium can be retained within the sleeve or member III so as to prevent electrical discharge under operating conditions. An insulating link Il is made in the form of a fiat loop. Flat shaped eyes I! l are inserted in a slot I6, and a bearing yoke or keeper IT is inserted in the eye IS. The yoke has projecting lugs I8 which engage the edges of the link H. The inner surface of the link bears upon the rounded edge I9 of the member 20 I1, which is shown in section in Fig. 3. The eye members I! are enlarged at their inner ends as shown at 20 in order to provide increased bearing 7 area between the member I5 and thegyoke member II. The slots I8 are made long enough so 26 that the member II with the enlarged portion can be shoved thru the slot. If desired two separate links can be used although the single unit is preferable as it tends to prevent disenga i oi. the parts. The space between the internal ele- 30 ments and the sleeve is filled with oil or insulating compound, suflicient space being allowed only for the expansion of the material unless separate expansion chambers are provided.

In Fig. 1 the heads II are screwed onto the 36 studs 2|. This places the sleeve II in compression and the insulating link I4 in tension. In general sufiicient tension is applied on the central member so that under working conditions the seal between the insulating sleeve I. and the 40 heads II will not be broken. In other words the insulators are preloaded. This has some very great advantages as cement joints and pacldng glands are eliminated. This greatly reduces the size and cost of the insulator and tends to eliminate mechanical stress which may cause damage to the insulating sleeve ll, brought about by the large difierence in the linear coefllcient ofexpansion between theinsulating sleeve II and the metal for changes in temperature. Due to the practical elimination of this so-called thermal stress, materials such as copper, bronze or aluminum which have higher linear coemcients of expansion than iron or steel can be used without increasing the danger of cracking of the insulatl6 ing member, which usually is porcelain or glass having a relatively low linear coeflicient of expansion.

In Fig. 1 a construction is used which permits of the use of an insulating link having a cross section which is a large percentage of the cross section of the opening in the insulating sleeve. Insulating sleeves are not necessarily restricted to circular types, but these are the most easily constructed and generally are stronger mechanically than members having rectangular cross sections. Where the cross section of the insulating link constitutes a large percentage oi the cross section of the opening in the insulating sleeve, the size and cost of the latter can be materially decreased.

Where the space 22 between the insulating link and the insulating sleeve is relatively small, the volume of oil or insulating compound is reduced. Since most insulating compounds have a relatively large volumetric coefiicient of expansion for changes in temperature, this small volume has the advantage that reduced space can be provided for the expansion of the filling medium for the higher temperatures. Where this volume is small expansion chambers may be omitted or the length of the insulating links with respect to the sleeve may be increased. Where appreciable space is required particularly for long insulators the insulating links may not be covered by the insulating medium.- When working at high voltages this may subject the insulating link to electrical discharges. In order to prevent this shields 23 which are electrically connected to the terminals thru the draw bolts l5 and yokes I! are provided. Other forms of shielding may be used which will permit a lowered level of the filling medium without exposing the insulating links to a discharge.

Where it is not necessary to use as large a cross section of the link as the interior of the insulating member will permit, other types of construction may be used. A construction of this kind is shown in Fig. 4.

In Fig. 4 the insulating link 24 has a much smaller cross section relative to the opening in the sleeve 25 than in Fig. 1. A cross section thru the center of the insulator is shown in Fig. 5. The space 26 between the insulating link 24 and the insulating sleeve 25 is relatively large. In Fig. 4 one end of the insulating link 24 is held by a U shaped bolt 21. The other end is held by a pin 28 which passes thru cars 23 which are a part of the head 33. The reaction between the insulating link 24 and the insulating sleeve 25 is obtained by tightening the nuts 3| which bear upon the head 32. Load is applied to the insulator by means of the eye 33 and clevis 34.

Where it is desired to reduce the volume of the insulating medium used to fill the space between the insulating link and the sleeve, this may be accomplished by suitable insulating fillers. One method of construction is shown in Fig. 6. In Fig. 6 sectional pieces of insulation 35 and 36 are placed in the slot formed by the two sides of the link 24. By making the pieces with suitable interlocking projections they will be held in place while the link mechanism is passed thru the insulating sleeve 25. It is readily seen that these filling members will displacea large portion of the filling liquid in'the space between the insulating links and the insulating tube. The amount of filling medium may be further reduced by filling in any remaining space 31 with sand or insulating material. By using methods of this kind the amount of filling medium may be greatly reduced so that the space required for expansion will be exceedingly small. This is important where an expensive filling material is used or where the insulator is operating in a horizontal or nearly horizontal position and it is desired to eliminate a space which may permit of a discharge inside the tube When the insulator is subjected to a high voltage or to lightning.

This method of reducing the volume of filling material is applicable to practically all of the various types of insulators shown in the several figures. In some cases the filling pieces and material can be used to prevent internal discharge and increase the internal breakdown voltage. This is valuable where the length of the insulating sleeve is so short that the links which engage the insulating member are brought near together.

Fig. 7 shows a further modification of the insulator shown in Fig. 1. The method of gripping the insulating link is the same. However, the insulating sleeve 38 bears against a terminal 39 at one end and expansion chamber 40 at the other. The expansion chamber allows for variations in volume of the filling medium. The construction has the advantage that the initial or preloading of the insulator can be applied'very easily and determined with a high degree of accuracy. The insulating link 4| with the tension eye 42 is passed thru the insulating sleeve 38 and the expansion chamber 40. Ground joints 43 may be coatedto insure a tight seal betweenthe insulating sleeve and the adjacent terminal members when they are under pressure. If desired gaskets may be applied at this point. The draw eye 42 is provided with a long threaded stud 44 and a nut 45. By using a suitable mechanism which will draw the stud 44 outward thru the top of the expansion chamber 40 it is possible to subject the link 4| to tension and set up the desired pressure between the insulating sleeve 33 and the terminals at the joint 43. It is evident that this may be readily accomplished by attaching suitable pulling means to the end of the stud 44 and applying an equivalent pressure against the top of the expansion chamber 40, the eye member 46 being removed. When the necessary stress is set up the nut 45 may be seated against the top of the expansion chamber. This nut can be used to form a tight seal. The resiliency or deformation in the various mechanical parts will maintain the pressure under operating conditions.

After the insulator is assembled the eye member 46 may be screwed onto the stud 44. A filling plug 41 is provided so that the insulating medium 43 may be poured into the insulator. The expansion chamber is provided with a weather shed or shield 49 which deflects drip water and reduces the leakage loss 01' the insulator under storm conditions. This member also provides an electrostatic shield.

In Fig. 7 the insulator is suitable where it is operating in a vertical or inclined position. Where the insulator is operating in a horizontal position it generally is advisable to place the expansion chamber above the insulator. An arrangement of this kind is shown in Fig. 8. The expansion chamber 50 is provided with an opening 5| which connects with the interior of the insulator. Since the expansion chamber is 'well above the insulating sleeve 52, the space between the insulating links 53 and 54 and the insulating sleeve can be maintained full of the insulating medium at all times. The general method of preloading the insulator which was described in Fig. 7 can be applied to the insulator shown in 'thru the Fig. 8. However, the ension member is in the form of a clevis having ears 6. A pin 51 passes ears it and engages the insulating links ill and I4. Tension is applied to the draw clevis II before the terminal eye I is screwed in place, after which the nut 59 may be tightened and the terminal bolt ll screwed into position. A filling plug I is provided for the expansion chamber.

,Where high strengths are desired a single insulating link may become quite thick and dimcult to form and cure. member may be made up of two links 53 and N. A c section thru the insulating sleeve 52 and the 53 and 54 is shown in Fig. 9. The link 4 is made so that it can be slipped over the link 53. The links are held at oneend by a pin I which is elongated in cross section. This pin bears against the terminal head 02 and is sealed in by a plug 83. The elongated or oval shape of the pin 8| provides stiffness even though the space between the sides of the insulating link I! is relatively small.

In order to provide an eilicient insulator the insulating link must be of small size and have high strength for a given cross section, and must be easily formed. In order to provide an emcient tension member a design been developed which will meet the various conditlonsvery satisfactorily. Insulating links embodying the above advantages can-be made up in several different ways. A very satisfactory link is one made of canvas or fabric treated with a phenolic condensation product well known in the art by the trade name Bakelite. The style of ink used has the advantage that links of various lengths can be readily made without being limited as to the width of the fabric. In order to form the links treated fabric of any desired width is wound over flat mandrels while being subject to heat and tension. After the mandrels are covered to the desired thickness they are placed in a vulcanizing or treating press where they are cured.

Such an arrangement is shown in Fig. in which the fabric M tobe treated is wound on a mandrel I. The mandrel is provided with pins I which engage driving mechanism so that the fabric under tension.

fabric can be wound onto the mandrel under If desired the mandrel may be made in parts with joints at '1 so that various lengths of links can be made by simply using the different lengths of mandrel between the carefully formed ends. The mandrel 68 is equipped with separableends I! and springs ll which place the tension while being treated. The platens II, II and I3 are heated and the rams 14 subject the" fabric to pressure while curing. This insures a dense material and binds the various fibers together.

An increased strength is obtained by using fabric which has the strongest threads running lengthwise. This method "of forming links makes it possible to use good widths of material to form a wide link. After treating narrow links may be sawed or cut from the wide link. This greatly reduces the caste! producing allink and makes .it possible to obtain a wide range in' the sine and strength with a minimum amount of equipment. It is'evident that a suitable mandrel may be wrapped with a treated cord. Individual links may be formed by using platens-with suitable grooves or by placing forms between the platens. This method makes it possible to conform more nearly to the shape of the inner If desired the tension of insulating link has surface of the tube. The cord has to be wound under considerable tension in order to provide a compact mass which will distribute the load between the various cor In Fig.11 a somewhat different form is shown. 5

The insulating sleeve is composed of two members I! and IS. Two rain sheds or shields l1 and II also are used. The tension member is composed of an inner insulating link I9 and an outer insulating link 00. The inner insulating link bears 10 upon pins ti and 82, and the outer insulating link bears upon pins 83 and 84. Using separate bearing members for the two links reduces the maximum bearing pressure between the pins and f abric, and permits of a larger cross section in the tension members without a reduction in the ultimate strength for a given cross section. The lower head 85 is provided with ears, the construction being similar to that in Fig. 4. The insulator is given an initial load in the same manner as that of Fig. '7 and Fig. 8. The nut 86 bears upon a recess in the weather shed 11. After the insulator is given the desired loading the clevis or eye 81 is screwed into position. By placing some initial pressure between the heads and the insulating sleeves it is possible to fill the insulators to the desired point before placing them under final tension. In this way any special filling means can be omitted as the insulator can be filled thru the, space between the draw bolt and the cap 11 before the nut 86 is tightened. If desired filling and draining means may be readily applied. In this type of construction additional weather sheds may be used which will greatly reduce the leakage loss during rains. weather sheds also can be used to set up a more uniform gradient, as they act as capacitance plates. For very high working loads the weather sheds preferably are of metal. Where the insulating housing or sleeves are not subject to heavy working stresses the weather sheds like that shown in It can be formed of insulation, thereby adding to the surface insulation of the insulator. Where insulating flanges or weather sheds are used they usually have much greater thickness at the point where they are clamped between the adjacent insulating sleeves. This is in order to prevent a discharge over the inner surface due to the voltage built up over the outside.

Fig. 13 shows a diilerent modification in which the insulating link 88. is surrounded by an insulating member I9 which is provided with petticoats or weather sheds 90. .The space 91 may be partially filled with insulating oil or compound I as previously described. The insulator is provided with a wire groove 92 and holes 93 for attaching a clamp which will hold' the. conductor in the groove 92. The insulator is given a conical shape so as to provide high strength for side 00 pull where the insulator is rigidly mounted by the base 94.

Fig. 14 is a plan looking down on the top of the insulator, and shows the holes 95 for bolting the base 94. The draw link is similar to 21 in Fi 4.

Tension is applied by tightening the nuts 96. The plug 91 is provided so that the insulator may be filled with insulating oil or compound-. The use of an insulating link which is easily and cheaply made and which may be gripped with interlinked attachments makes it possible to construct a number of different insulators on a more efficient basis than heretofore.

In Fig. 15 the insulating link 98 is attached to terminal members using someone of the vari- 1s plates III and H2 is shown in Fig. 18.

one schemes described. Insulating members 09, I and IM are clamped between the terminal members I02 and I03. Gaskets or joints are provided between the various sections, or the housing may be made in one piece if desired. In order to prevent internal discharge Where the oil level does not entirely cover the insulating member a pocket I04 lined with a conducting coating may be used to screen the insulating member 98.

In Fig. 16 the general construction is similar to that of Fig. 13 with the exception that the insulator is provided with ears I05 which are attached to a bracket I08 by a bolt or pin i071. This arrangement allows the insulator to swing in the direction of the line, relieving it of a large portion if not all of the bending moment due to a broken conductor or an unbalanced stress in the conductor I08. At the same time the construction provides rigidity so as to prevent side sway of the conductors under transverse wind loads. This type of construction is particularly applicable to railway work.

Fig. 17 shows an application of the insulating link in the construction of multiple element post or radio insulators. In this construction insulating members I09 and'IIO are gripped between plates III, H2 and II 3. A cross section between The several plates are provided with suitable bearlug surfaces and gaskets. Draw clevises or attachments III and I I5 are provided so that insulating links IIG can be placed under tension. This clamps the plates and insulating members together, forming sealed in compartments or spaces for the insulating links II6. This method of construction has the advantage that several insulating members maybe used in multiple to provide a high mechanical strength in tension, compression or for bending moment. By reducing the length of the individual insulating members and using intermediate moment plates or members such as II2 the strength of the insulator for a transverse load applied at the top is greatly increased. The insulators may be heated with a heating element immersed in the filling liquid, or by an outside circulating system. Ports I I1 and ;I II provide for a circulation of the oil. An additional expansion chamber may be provided as in some of the other types so that the space within the insulating sleeves will be completely filled and a circulation of warm oil can be obtained. The circulation of the oil is desirable as it is then possible to warm the surface of the insulator to removed films of mois-,

ture.

Fig. 19 shows another application of the insulating link. This is similar to Fig. with the exception that the insulating housing II 9 is made in a single piece.

In Fig. 20 the conical insulating housing I20 provides rigidity for a post or pillar insulator, where the conductor is mountedabove the insulator in the wire groove I 2|. The insulator is provided with a metal rain shed or shield I22 which projects well down into the open end of the insulating member I20. The insulating link I23 is attached inside this projection by a suitable pin I24. The downwardly projecting portion I25 of the member I22 engages an insulating member I26. The object of the insulating member I26 is to provide rigidity for the insulator in case that the insulating sleeve I20 is damaged. As

the member I20 usually is made of fragile material this member may be damaged by shooting or by rocks thrown against the insulator. It

is highly desirable that the insulating member will not drop the conductor, which may be carrying a high voltage. The member I26 has sufficient strength so that the conductor can be sustained where the fragile insulating sleeve is damaged. In the case of pendant or underhung insulators an additional sleeve is not necessary as the links are in tension and not subject to bending moment. The intervening space is filled with oil, just sufficient space being allowed for expansion.

The various types of the insulators shown are particularly applicable where it is desirable to prevent discharges which will cause radio interference, the electrostatic field due to the construction being very favorable to operation at high voltage. The insulators have small electrostatic capacity and therefore they are particularly valuable for installation in fog districts,

for radio strain insulators and for insulating self-supporting radiators.

Fig. 21 is a section thru Fig. 20 showing the safety sleeve I26.

Other arrangements may be used such as that shown in Fig. 22 in which the insulating link is surrounded by a safety member I21 composed of wood or other suitable material.

Fig, 23 shows an application of an insulating cross arm of the swinging type. The member I28 is a tension member, and the member I29 normally is in compression but may be thrown in tension. This member being in approximately horizontal position is provided with an expansion chamber I30. The arms support an insulator string III. The member I29 may be constructed in several different ways with or without safety compression members.

Fig. 25 shows one construction in which a non-shattering insulating sleeve I32 is placed between the insulating link I33 and the fragile insulating member I34.

Fig. 26 shows a section with a different form of safety compression member I35 formed of wood or other material. Grooves I36 may be placed in the side into which the tension insulating links can be fitted.

I claim:

1. An insulator comprising a housing of solid insulating material, fittings at each end of said housing, a tension member in the form of a closed loop of insulating material connecting said fittings, solid insulating filling within said housing and extending between the arms of said loop in space not occupied by said arms, and a filling liquid or compound filling remaining space within said housing.

2. An insulator comprising a link of insulating materials, the arms of the link being flat bars extending close together and disposed side by side providing a slot therebetween and extending about the ends of the link to form loops connecting the two arms, and fittings for opposite ends for said link, said fittings comprising keepers extending through the slot between said arms and engaging said loops, and attachment means secured to said keepers for applying a load to said insulator, said link being formed of fibrous material impregnated with an artificial resin and cured to impart rigidity to said links.

3. An insulator comprising a link of insulating materials, the arms of the link being flat bars extending'close together and disposed side by side proiliding a slot therebetween and extending about the ends of the link to form loops connecting the two arms, and fittings for opposite ends member and a link of non-fragile dielectric material connecting said fittings, said link comprising a continuous flat bar formed into a loop, the opposite ends of said loop being disposed adjacent said fittings, keepers passing through said loop, one at each end thereof, said bar being slotted transversely of said keepers, and eye members projecting from said fittings and extending into the slots in said bar to engage said keepers and connect said loop with said fittings.

ARTHUR O. AUSTIN.

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