US1737749A - Insulator - Google Patents

Description

. 1929- A. o. AUSTIN 1,737,749

INSULATOR Filed Feb. 12, 1925 2 Sheets-Sheet 1 Fig.2

' INVENTOR BY v wni n d A TTORNE Y3 Dec. 3, 1929. A. o. AUSTIN 1,737,749

INSULATOR Filed Feb. 12, 1925 2 Sheets-Sheet 2 IN VEN TOR Q/IAMAT M M y wa x 46,;

A TTORNEY Patented Dec. 3, 1929 UNITED STATES PATENT OFFICE ARTHUR O. AUSTIN, OF BARBERTON, OHIO, ASSIGNOR, BY MESNE ASSIGNMENTS, TO THE OHIO BRASS COMPANY, OF MANSFIELD, OHIO, A CORPORATION OF NEW JER- SEY IN SU'LATOR Application filed February This invention relates to insulator construction and particularly to the connection between the dielectric member of an insulator and the metallic fitting.

The object ofthe invention is to provide an improved joint between the dielectric memher and fitting which shall be eflicient under varying conditions and especially under different conditions of load and temperatures.

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

In the drawings Fig. 1 is an elevation partly in section showing a suspension insulator having one embodiment of the present invention, applied thereto.

Fig. 2 is a fragmentary view similar to Fig. 1 showing a modified form of the invention.

Fig. 3 is a view similar to Fig. 2 showing a different form of the invention.

Fig. 4 is a view similar to Figs. 2 and 3 showing still another form of the invention.

F 5 is a view similar toFigs. 2, 3 and 4 showing a different modification of the invention.

Figs. (3 and 7 are fragmentary sections showing other forms of the invention.

In the operation of insulators, particularly suspension insulators and bus insulators Where it is desirable to attach metal parts to transfer the mechanical loads to the dielectric member, it becomes exceedingly difiicult to control the stresses in the dielectric for all conditions of loading and changes in temperature.

This "invention deals particularly with improvements which permit a much better control of stress in the various parts for different combinations of temperature and loading.

In Fig. 1 is shown one form of suspension insulator to which the improvement has been applied. The insulator consists of a dielectrio member 10 having a head 11 provided with roughened surfaces 12 for the engaging of cement 13 interposed between the head 11 of the d-i'e lectric'member and the cap 14 and 12, 1925. Serial No. 8,822.

pin 15, the pin being provided with engaging flanges 16. The lower portion of the cap 14 is reinforced by a band 17. The main cap 14 may be provided with openings or slots at any point, but particularly at the lower edge as shown at 18 for control of the mechanical stress in the adjacent dielectric.

A layer of yielding material may be disposed over the portion of the dielectric member displaced from the reinforcement 17 as shown at- 12. This confines the transmission of the load to the gripping portion of the cap reinforced by the band 17 and prevents undue stresses in the dielectric member due to unequal contraction and expansion of the parts not provided with reinforcement.

Vfhile the improvement is applicable to many types of insulators, it is particularly applicable to suspension or dead-end insulators where the working loads imposed bythe conductors are high, necessitating large parts.

The materials ordinarily used for forming the cap and pin are malleable iron and steel, although in some cases steel or bronze may be used for the cap. Vhen tension is applied to the insulator through its attaching means as in Fig. 1, the mechanical load is transferred to the dielectric through the cement or other material interposed between the metallic members 1-1 and 15 which are equipped with engaging grooves or ridges 16 and 19. The force exerted produces a resultant having the approximate direction of the arrow 20. This force may be resolved into a component in the direction of the axis of the insulator and into a radial component. As the load increases, the radial component places a circumferential tension on the material of the cap 14 adjacent to the surface upon which the component acts. This tends to expand the cap. At the same time there is an equal and opposite reaction acting upon the dielectric member tending to compress the same. Since a bearing must be maintained between the various surfaces in order to establish the stress, it will be seen that the porcelain will tend to be shoved outward due to the expansion of the cap and the force of the load on the pin 15. This tends to set up a tension in the dielectric normal to a plane passing through the axis.

If this tension becomes too great a crack is formed in the dielectric which will destroy its usefulness or limit the load which may be 5 placed on the insulator.

In the ordinary construction the cap 14, made of malleable iron or forged steel has a linear coeflicient of expansion for temperature changes from two to three times that of the dielectric member. If then, the insulator is heated due to the sun or for testing conditions, the cap will tend to expand so that if a heavy load is applied at the same time, the circumferential component in the porcelain will be increased as the dielectric will have to be expanded in order to maintain necessary bearing on its outer surface. In order to correct this inherent defect, which is likely to be serious or a limiting factor in insulators designed for heavy working loads, the cap is re-inforced with a band of metal 17. This reinforcing member 17 may be made in a variety of forms without changing the principle of the invention. When made Q5 of a metal having a linear coeflicient of expansion for temperature changes approximately or even lower than that of the dielectric member, it will be seen that certain very material advantages are obtained. Where a metal such as Monel metal having a composition approximately 1 iron, 26 copper and 72% nickel and a low coefficient of expansion is used, it will be seen that as the temperature is increased, the stress control band 17 will not tend to expand as readily as the body of the cap 14 and will retard the expansion of the cap in accordance with the laws of mechanics of materials. In general, by making the cross section of the band 17 large compared to the cross section of the cap 14,

the inner bearing surface of the cap 14 in contact with the cement may be made to conform'closely to the characteristics of the ban d 17 so that high temperatures will not tend to seriously expand the bearing surface of the cap 14 so as to limit the load which may be placed on the dielectric.

Under operating conditions, the working loads usually tend to increase as the temperature falls. This is particularly true with dead-end insulators as the contraction in the line decreases the sag which, in turn, increases the tension on the insulator. By giving the cross section adjacent the bearing surface of the wall of the cap 14 its proper relation, it is possible to use the contraction of the cap to offset the increasing load at the lower temperature. The same result may be obtained y using a metal for the band 17 which has a lower coefiicient of expansion for temperature changes than that of the dielectric member, such as invar steel. A composition for invar steel which has a linear coefficient of expansion for temperature changes approximately that of porcelain is composed of nickel, 69.4% iron, .4% manganese and 2% carbon-approximately.

Using a reinforcing band 17 having a low linear coetficient of expansion for temperature changes has a material advantage where the cross section adjacent the bearing surface of the cap must be large to withstand high resultant forces. Where the effective cross section of the cap is large and the linear c0- eflicient of expansion for temperature changes is greater than that of the dielectric, it is seen that although the contraction may be balanced by a heavy load at low temperatures, there is danger that the head of the dielectric member may be sheared from the flange at low temperatures where the insulator carries a light load, as the resulting forces tending to counteract the contraction of the cap would not then exist. In the case, however, where the reinforcing band 17-has a linear coeflicient of expansion for temperature changes approximately the same as the dielectric member, a low temperature will not set up a dangerous stress tending to shear the head from the flange of the insulator, even though the cross sect-ion of the reinforcing band may be large. Where the diameters are relatively small as in insulators with relatively low working loads, the refinements may not be necessary, but it is readily seen that as the diameter increases the differential expansion and the difierential movement in the radial direction between the dielectric and the metal members in contact with the bearing surfaces will tend to increase so that refinements are highly desirable for insulators of large size designed for heavy working loads. The reinforcing band may be applied in a number of different ways, such as forcing on after galvanizing the cap and the member 17 where same is of metal which needs weather protection or the member may be galvanized in place in which case, however, it is preferable to provide a slight taper on the cap so that the band may be forced down over the cap so as to counteract the greater expansion of the cap due to the heat of the galvanizing bat-h. Where the reinforcing band 17 is simply forced down over the cap, a reduced cross section of the cap 14 may be utilized to distribute the longitudinal stretch in the cap, thereby controlling the stress set up in the dielectric to a considerable extent. In general, in order to provide against the resultant force in the radial direction, the necessary cross section of the caps has heretofore been too large to permit the desired longitudinal stretch so that the caps are too rigid in a longitudinal direction. By simply providing a radial bearing, however, a small effective cross section throughout the bearing zone of the cap may be utilized to control the longitudinal stretch.

A modification of the reinforcing band which is particularly applicable to set up this condition is shown in Figs. 3 and 4.

' In general, the high linear coefiicient of expansion for steel may be utilized to advantage in the case of the pin. As the highest loads generally 'occur at the lowest tempera tures, a low temperature tends to cause contraction and to offset the longitudinal stretch on the body of the pin. Since the diameter of the pin is much smaller and the pin may be equipped with resilient bearing surfaces as shown in my previous Patent No. 1,489,689, refinements in the pin are not so essential. In some cases, however, it may be an advan tags to make theportion of the pin embedded in the cement with a material having a linear coefficient of expansion for temperature changes approximately the same as that of the dielectric. In general, however, the cost of such material has prohibited its general use. A construction, however, is shown which tends to offset this difficulty. The embedded portion is provided with a threaded end 21 which screws into an attaching section 22. This tends to reduce the quantity of expansive material to a minimum.

From a consideration of the principles in volved, it is obvious that there are several other constructions which may be utilized depending upon the results desired, but which still embody the principles of the invention.

Fig. 2 shows one of these arrangements where the stress control band 17 in place of being forced on or galvanized on to the main cap 14 is held to the cap by a joint filled with material 24. This joint may be formed with a metal such as lead or type metal or by Port-- land or other suitable cement. In the latter case the jointmay be formed at comparatively low temperatures so that the difference in the linear coefficient of expansion for tempera ture changes between the two metals would not necessitate setting up stress between the two parts at ordinary temperatures. This construction has the advantage that parts which are uneven or irregular may be readily assembled together as the material in the joint 24 will take up the irregularities. It is evident that by changing the cross section of the band, its reaction may be controlled at different zones so as to produce a grading of the stress in the dielectric in the adjacent zone.

Another method of grading or controlling the stress by the stress control band is shown in Fig. 3. In this case, several bands 25, 26 and 27 are shown. The size and shape of these bands may vary considerably so that their effect can be controlled so as not to induce a dangerous shearing stress in the dielectric at the ends of the effective pressure or stress zone in the dielectric. This usually necesstates greater reinforcing in the center of the zone and less at the ends where it is desired to relieve the pressure on the dielectric in order to prevent dangerous shearing stress in the dielectric. Splitting the reinforcing band into several zones in addition to controlling the radial component of stress also has a material advantage in that the effective longitudinal cross section of the cap may be reduced so that the elastic stretch in the cap will be more nearly comparable to that in the pin. This is partic ularly important for very high strength units where pins having relatively rigid cement engaging surfaces are used. The reinforcing bands 25, 26 and 27 may be forced into place after the parts have been galvanized or they may be galvanized in place. In the latter case, it is usually advisable to form the cap with a slight taper and force the flanges into position so that there is some initial stress between the reinforcing bands 25, 26 and 27 and the cap body member 1% so that under normal conditions there is no material stress set up between the reinforcing flanges and the body of the cap. by proportioning the relative cross section area of the reinforcing flanges and the adjacent cross section of the cap, it is possible to set up a wide variety of conditions, particularly where the temperature is controlled during the assembly of the flanges to the caps and during the setting of the cement between the cap and the porcelain. Vith the schemes as shown, it is possible to use high temperatures to cure Portland cement quickly without setting up conditions where the head of the dielectric may be sheared off in cold weather, particularly where the loads are light on the insulator.

Another method of providing a reinforcing band is shown in Fig. 4. In this case the body of the cap 14 is wound with a reinforcing wire 28 of the proper composition. By varying the size and the spacing of the wire, the stress may be controlled. If there are successive turns with separation between the strands, it is evident that the wire reinforcing band will not seriously effect the longitudinal elastic stretch of the body of the cap. There are a number of ways of attaching the wire reinforcing band such as making the band up to size and forcing in place or winding in place. The ends may be held by electric welding as at 29 or by wrapping around a projection on the cap as at 30. Where the end turns are welded together as at 29, it is possible to make up the band and force into position and then galvanize the combination together. The friction will hold the bands from unwinding during the galvanizing operation and after galvanizing the zinc adhering to the two parts as well as the friction will hold the bands tightly in place. In most cases, the helical reinforcingbands 28 and the cap 14 may be forced together after galvanizing as the friction will tend to maintain the relative position. If the conditions are extreme so that a loosening will tend to occur, this may be prevented by welding successive strands together at a few points as at 31. If these points are staggered, the longitudinal flexibility of the reinforcing band may be kept down. It is evident that there are a variety of conditions which may be established, but the invention consists essentially in usin a combination of metals having different linear coefficients of expansion for temperature changes in order to control the resultant force set up in the dielectric member under operating or test conditions. The combination may be used to control the conditions usually set up at the extremes in temperature as such are ordinarily found where malleable iron or steel caps are used for suspension or bus bar insulators. In the invention, the amount of expensive material having a low linear coeliiecient of expansion for temperature changes is reduced to a minimum, it being possible to use the ordinary materials such as steel or malleable iron for the major portion of the attaching means.

lVherc it is desired to eliminate the radial force set up by the body member 14 this may be readily effected by slotting the body member 14 with longitudinal slots 33 which may extend entirely through the zone or may be staggered as at slots 34 in Fig. 3. \Vhen for mechanical or assembly conditions, the main body of the cap 14 is likely to set up too high a resultant pressure at low temperatures, this maybe offset to a considerable extent by placing reinforcing material having a low linear coefiicient of expansion for temperature changes between the cap 14 and the dielectric head 11.

One construction of this kind is shown in Fig. 5. In this case the cap 14 is provided with a thread 35 or other engaging means for attaching to the reinforcing band 36. In this case, the reinforcing band 36, composed of material having a low coeflicient of expansion for temperature changes, is provided with a grooved or roughened inner surface 37 for engaging the cement 13 adjacent to the dielectric 11. It is readily seen that in this case the cap portion 1.4 may be made so that it is removable from the head of the insulator and the attached reinforcing band 36. Should the insulator become damaged in any way, it will be possible to simply remove the cap and place on another dielectric member equipped with a reinforcing band 36. Vith this arrangement, it is seen that at low temperatures, the contraction of the cap 14 must act through and compress the band 36 before it can produce a dangerous stress which tends to shear off the head of the dielectric. During high temperature conditions, it is also seen that the construction may be such that the cap portion 14 may expand without appreciably effecting the stress set up by the band 36, which is not true in the former cases ggrcept where the longitudinal slots exist as in Another method of providing reinforcing material is shown in Fig. 6. In this case the reinforcing band 38 is made up of sections having projecting rings 39 which engage corresponding grooves in the cap 14 and in the dielectric 11. The intervening space is filled with cement or other suitable material 13. This tends to produce an interlock between the insulator and the cap. It, of course, is evident that the outer surface between rings 39 and the cap 14 may be similar to that shown in Fig. 5.

Another method of appl ing the invention is that shown in Fig. 7. n this case the reinforcing material is placed in rings 40. It is evident that the shape, as well as the engaging surface of the reinforcing band or bands may be made in a variety of forms for manufacturing reasons or to control the stress at various points. By controlling the angularity of the bearing surfaces of the rein torcing band and the cap as in Fig. 5, the effect of the cap member 14 upon the reinforcin g band and the dielectric may be made little or nothing for certain other conditions. Vhere the bearing surfaces of the thread are nearly flat, it will be seen that a longitudinal tension in the insulator will not tend to set up any reaction between the two parts. If, however, the bearing surfaces are at an angle there may be a radial component between the cap 14 and the reinforcing band 36. All surfaces where it is not desired to set up a stress between the metal parts or between the dielectric and the metal parts can be coated with a wax or a material which will shrink after the assembly, as has been shown in my previous Patents Nos. 1,284,975 and 1,489,690-

I claim 1. In an insulator a dielectric member and 4. In an insulator a dielectric member and a fitting attached thereto, said fitting having an engaging portion for holding said dielectric member, said engaging portion being provided with a reinforcement connected therewith for withstanding stress transmitted from said dielectric member to said fitting, said reinforcement being formed of metal having substantially the same coefiicient of expansion as said dielectric member.

5. In combination a dielectric member and a metallic fitting therefor, said fitting comprising a body member having a higher coefficient of expansion for temperature changes than said dielectric member and having a metallic engaging portion for connection with said dielectric member Which has a coeflicient of expansion approximately equal to that of said dielectric member.

6. The combination with an insulator of a cap therefor and a supplemental band for said cap where it grips said insulator, said band having a diiferent coeificient of expansion for temperature changes from the rest of said cap so that it acts to restrict the expansion and contraction of said cap for temperature changes.

7. The combination with a dielectric member of a metal fitting therefor attached to said dielectric member and a supplemental reinforcement for the portion of said fitting connected to said dielectric member, said reinforcement being in position to withstand stresses transmitted from said dielectric member to said fitting, said reinforcement con sisting of invar steel having a coefficient of expansion approximately that of said dielectric member.

8. An insulator comprising a porcelain dielectric member, a metal cap therefor, and a reinforcing band of invar steel for said cap having approximately the same coefficient of expansion for temperature changes as porcelain.

9. An insulator comprising a dielectric member, a cap for said member disposed about the same and a reinforcement for said cap having a lower coeflicient of expansion for temperature changes than other portions of said cap, said reinforcement being disposed adjacent the rim of said cap and disposed about said member.

10. An insulator comprising a dielectric member, a cap for said member having the gripping portion thereof slotted, and a reinforcing band for said gripping portion said band being composed of metal having a tem perature coefficient of expansion approximately the same as that of said dielectric member.

11. In an insulator a dielectric member, a cap for said member having a gripping portion secured to said member, a reinforcement for said gripping portion having a temperature coefiicient of expansion approximately equal to that of said dielectric member, and yielding spacing means between said dielectric member and ortions of said cap removed from said rein orcement. I

12. In an insulator a dielectric member, a cap for said member and a reinforcing band for said cap having a lower coefficient of expansion for temperature changes than the material of said cap, said band being forced into position against the outer surface of said cap.

13. in insulator comprising a dielectric member, a pin, and cement for securing said pin in said dielectric member, the portion of said pin embedded in said cement being composed of metal having a coefiicient of expansion for temperature changes approximately equal to that of said dielectric member while the remainder of said pin is composed of more expansive material.

14:. An insulator comprising a dielectric member having a recess therein, and a pin having a portion thereof secured in said recess and having another portion projecting from said recess, said first-named portion being separately formed from said projecting portion, the material of said first-named portion having a coefiicient of expansion substantially the same as that of the material of said dielectric member but having a tensile strength substantially as great as the material of the other portion of said pin.

15. An insulator comprising a dielectric member, a metallic fitting for said dielectric member surrounding a portion of said member and attached thereto, and a closed reinforcing ring surrounding the portion of said fitting attached to said dielectric member, said reinforcing ring being formed of material having a coefficient of expansion substantially the same as that of the dielectric member.

16. T he combination with an insulator, of a cap therefor, and a supplemental closed band for said cap surrounding said cap where said cap is secured to said insulator and disposed adjacent the lower rim of said cap, said band being formed of metal having a coeflicient of expansion for temperature changes substantially equal to that of the dielectric material of said insulator and acting to restrict the expansion of said cap for temperature changes.

17. An insulator comprising a dielectric member, a metal cap therefor, and a reinforcingband of invar steel for said cap having approximately the some coefficient of ex ansion for temperature changes as porce'ain, said band being secured against circumferential movement relative to said cap and being; disposed outside of said cap adjacent the rim thereof.

18. An insulator comprising a dielectric member, a cap for said member having the edge portion thereof slotted, and a closed reinforcing band surrounding said cap adj acent the edge thereof, said band being composed of metal having a temperature coeflicient of expansion approximately the same as that of said dielectric member.

7 19. In an insulator, a dielectric member, a cap for said member surrounding a portion of said dielectric member, and a closed reinforcing band for said cap disposed outside of said cap and having a lower coeflicient of o expansion for temperature changes than the material of said cap, said band being under initial tension upon said cap.

20. An insulator comprising a dielectric member, a fitting for said member having a 5 portion surrounding a portion of said dielectric member and attached thereto and other portions being unattached to said dielectric member, and a reinforcing band surrounding the attached portion of said fitting and held go against movement in the direction of the length thereof relative to said fitting, said band being composed of material having a lower coeflicient of expansion for temperature changes than the material of said fitting.

'25 21. An insulator comprising a dielectric member, a cap for said member having a portion thereof cemented to said dielectric member and a reinforcing band surrounding the cemented portion of said cap to prevent separation of the cemented joint between said dielectric member and cap, said band being composed of metal having a lower coeflicient of expansion for temperature changes than the metal of said cap.

22. An insulator comprising a dielectric member, a cap disposed over a portion of said member, said cap having a portion of the inner surface thereof secured to said dielectric member by means of cement and having 49 another portion of the inner surface free from connection with said dielectric member, and

a reinforcing band surrounding the portion of said cap cemented to said dielectric member, said band having a lower coelficient of expansion for temperature changes than the interior of said cap.

23. An insulator comprising a dielectric member having a tapered attachment portion, a cap having a tapered socket arranged to receive said attachment portion, cement interposed between said cap and said attachment portion for holding said arts together, said parts being freely separa le except for the action of said cement, and a metal reinforcing ring surrounding said cap and encircling the cemented joint between said cap and dielectric member, said ring being formed of metal having a lower coeflicient of 60 expansion for temperature changes than that of said cap.

In testimony whereof I have signed my name to this specification on this 7th day of February, 1925.

65 ARTHUR O. AUSTIN.

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