US1979092A - Insulator - Google Patents

Description

Oct. 30, 1934. A. o. AUSTIN 1,979,092

INSULATOR Original Filed May 17. 1930 INVENTOR. BY A? M IQ 4% A TTORNE Y5 Patented Get. 30, 1934 twat @FFEQE isracez EINSULATQE Jersey @riginal application May 1'7, 1930, Serial No.

453,180. Divided-and her 13, 1934, Serial Britain July 23, I930 21 Claims.

This invention relates to insulators subjected to mechanical stresses andhas for its object the provision of devices of this class which shall be of improved construction and operation and which are adapted to accommodate themselves to conditions of stress and temperature to which they are subjected.

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

In the drawing the figure is an elevation with parts in section showing one embodiment of the present invention.

This application is a division of application Serial No. 453,180, filed May 17, 1930, which is in part a continuation of application Serial No. 32,715, filed May 25, 1925.

In suspension insulators or insulators used in tension of the usual cap and pin form, there is a tendency for the metallic parts to distort under heavy load. In addition, the differential expansion between the metal and porcelain also tends to change the relation of stress both in the metal and the dielectric. Under some conditions the distortion of the metal may permit the re-arrangement of stress in the dielectric such that the dielectric member will be cracked, destroying its electrical reliability. One of the chief difficulties, particularly on insulators of high mechanical strength, is the radial distortion of the cap.

The figure shows one method of correcting this defect. The dielectric member 50 is cemented into a cap 60. A pin 58 is cemented in a recess in the head of the dielectric member. When load is applied to the cap and pin 58 by their attaching means, there is a tendency to pull the dielectric head out of the cap 60. The resultant pressure tends to expand the cap 60. This has a tendency to permit the dielectric member'to deform and crack under the stress. In order to onset the expansion of the cap 60, the dielectric member is given a wedge shaped head. The tapered bearing surfaces 54, 55 and 56 will maintain pressure against the cement by slipping down as the cap expands from increased temperature or due to the load. These surfaces are preferably smooth and coated with graphite or some material which will lubricate the surface. The remainder of the head is preferably relieved from any stress by dipping or otherwise applying a yielding coat ing. It is evident that while the expansion of the cap may be compensated for, it is also evident this application Septem- No. 743,881. In Great that the cap can set up a very heavy pressure tending to pinch the head off under low temperature conditions, particularly where the load or tension on the insulator is slight. In order to relieve this maximum stress which tends to shear off the head, two methods may be used. The radial stress set up by the cap may be reduced by providing it with slots suitably spaced. This tends to taper 01f the radial pressure and minimize the danger of shearing, particularly under low temperatures. This construction has distinct advantages over a construction where the cement is allowed to slip in the cap. In the latter case the tangential forces in the cement tend to make it diificult to control the pressure between the dielectric and the cement. Where the dielectric, however, has a tapered head, the cement being comparatively weak in tension can always expand and permit adjustment of the head for a distortion in the cap.

A tapered surface to permit slipping for maintaining the radial pressure in the cement'may be applied also to the inner surface of the dielectric. The tapered surfaces 51, 52 and 53 are preferably coated with graphite or graphite and'wax or oil. When a heavy load is applied to the attachments 58 and 60, the resultant forceon the head of the dielectric member 50 tend to cause it to deform. The radial distortion tends to weaken .the cement and permit shearing at a lower load. In this particular case this is compensated for by the cement sliding on the tapered surfaces 51, 52, 53, 54, 55 and 56 so as to maintain proper radial pressure, The grading of the stress may be materially improved by the use of a pin 58 having resilient flanges which have been described in my previous'Patent No. 1,489,689, dated April 8, 1924.

In insulators having large bearing surfaces, the reduction of the diameter of the head, due

to its tapered form, is very material where the stress is carried on a single bearing surface extending for a considerable distance along the axis of the insulator. This may be ofiset as shown in the drawing. In this case several tapered surfaces 54, 55 and 56 are provided on the outside of the head of the dielectric 50. These surfaces are preferably coated as previously explained and the head coated with a yielding material. The angularity of the tapered bearing surfaces 54, 55 and-56 may be changed so that the stress may be tapered ofi' at the end surfaces and the heaviest load placed on 55. This tends to reduce the shearing stress and permits of an increased load being placed on the insulator without danger of lilo . angularity may be varied in accordance to the I causing a stress which will crack the dielectric. The stress on the inner surface may be carried by a cement joint, the load being distributed by the use of a resilient pin and resilient sanded surface, as explained in my previous Patent No. 1,284,975, dated November 19, 1918. As heavy loads or tensionson the insulator usually occur at low temperatures, there is a tendency for the cap to contract under these conditions and compensate for deformation caused by the stresses Set up by the load. In this case, it may not be necessary to apply any compensation to the cap, particularly where the latter has a heavy cross section. The pin, however, has a tendency to contract and relieve the stress as well as the cement, which usually has a lower linear coefficient of expansion for temperature changes. By providing the inner surface of the dielectric with slipping surfaces 51, 52 and 53, as shown in the drawing, it is possible to maintain the radial force on the cement between the surface of the dielectric and the pin. As previously explained, this surface is preferably coated with a thin coating of graphite, wax,ol of some combination in order to control the coefficient of friction. Where slipping is desired, it is necessary to use some material on the surface, for if Portland cement isused, there is likely to be a slight bond between the cement and surface in time so that slipping will not take place except at excessive loads. The slope of the bearing surfaces 51, 52 and 53 may be changed as to angle as shown in the drawing in order to control the stress. A material control in the stress may also be effected by the use of a pin having resilient flanges or through the control of the effective cross-section in the pin.

It is evident that compensating surfaces may be applied to both the inner and the outer surfaces of the dielectric. This is shown in the drawing. A dielectric member 50 is equipped with inner sloping surfaces 51, 52 and 53 and .outer sloping surfaces 54, 55 and 56. The inner surfaces permit compensating for deformation or changes in the inner wall of the dielectric as well as in the cement 57 and pin 58. In general, however, by the use of a resilient pin, a grading of the stress on the inner surface may be effected by controlling the relative stiffness of the flanges on the pin at different points. The tapered slipping on the outside of 54, 55 and 56 tends to compensate for cap and dielectric deformation as well as the deformation of the cement 59 between the dielectric 50 and the cap 60. The

conditions which it is desired to set up and may vary considerably for different designs.

If the metal is allowed to slip, the cement may absorb a large part of the force due to the radial component set-up in the cement. In the case where the dielectric member slips, however, the cement being weak in tension simply checks at different places and permits the proper relation between the parts, tending to develop a high ultimate for a given area.

In the case of the inner tapered surface, the cement projects between the flanges of the resilient pin, forming annular rings or galleries. These galleries may be given an appreciable defiection and form a part of the means for distributing the load. If these galleries are to function properly, it is important that the radial forces or pressure be maintained. This is effected by placing the compensating surface on the dielectric, The resilient caps in accordance with my previous'Patent No. 1,552,663, dated September 8,

1925, may be used to advantage in order to distribute the load properly to make up for any unevenness on the coating of the surface or to prevent excessive stress due to contraction at low temperature.

I claim:

1. An insulator comprising a dielectric member, a fitting for said dielectric member, said dielectric member having a plurality of smooth inclined bearing surfaces differing from one another in angularity and registering with said fitting, and a lubricating coating disposed on said bearing surfaces to facilitate sliding thereof under the force of the load on said insulator.

2. An insulator comprising a dielectric member, a cap for said dielectric member, cement interposed between said dielectric member and cap, said dielectric member having a plurality of bearingsurfaces inclined at different angles to exert a wedging action on the cement and to grade the stress transmitted between said cap and dielectric member, and a lubricating coating disposed on said bearing surfaces to facilitate slipping between said dielectric member and cement, the

edge of said cap having a weakened portion to produce a gradient in the pressure exerted on said dielectric member at the edge of said cap.

3. In an insulator, a dielectric member having a plurality of tapered bearing surfaces, a second member cooperating with said surfaces, said surfaces differing in' angularity to grade the stress in said dielectric member, a central surface having greater angularity than surfaces at either side thereof.

4. An insulator comprising a dielectric member, a holding member secured to said dielectric member, said dielectric member having a plurality of tapered bearing surfaces cooperating with said holding member and differing in angularity to grade the stress in said dielectric member, the

angularity of said surfaces decreasing from a cen- 1 tral position.

5. An insulator comprising a dielectric member, a fitting for said dielectric member, said dielectric member having a plurality of smooth inclined bearing surfaces differing from one another in angularity and registering with said fitting, the angularity. of said bearing surfaces being greatest at a central position and decreasing in opposite directions from said central position, and a lubricating coating disposed on said bearing surfaces to facilitate sliding thereof under the force of the load on said insulator.

6. An insulator comprising a fitting, a dielectric member having a plurality of tapered bearing surfaces distributed along a face of said dielectric member, said fitting having bearing surfaces cooperating with the bearing surfaces of said dielectric member and arranged to slip under the load on said insulator to compensate for deformation in the parts of said insulator, said surfaces differing from one another in angularity to control the distribution of stresses on said dielectric member, the coefficient of friction between cooperating surfaces being low, enough to permit reverse slipping of said surfaces under force normal to the direction of the load.

7. An insulator comprising a dielectric member, a fitting for said dielectric member, cement interposed between said fitting and dielectric member and having inclined bearing surfaces, said dielectric member having a plurality of smooth bearing surfaces in registration with the bearing surfaces of said cement, the bearing surfaces of said dielectric member being inclined at different angles evaoea the influence of the load on said insulator and to grade the distribution of stress transmitted between said fitting and dielectric member, the coefficient of friction between said registering hearing surfaces being low enough to permit relative movement of said surfaces under force normal to the load on said surfaces.

3. An insulator comprising a non-conducting shell, 2, pin, said shell having a recess therein receiving'one end of said pin, which recess has a strain receiving surface tapering inwardly towards the free end of the pin, cement filler within the recess and surrounding the pin to retain the pin in position within the shell, said shell having an outer strain receiving surfac'e tapering in the same direction as the strain receiving surface of the recess, a cap embracing said outer strain receiving surface and cement filler within the cap and surrounding said outer strain receiving surface to retain the cap and shell in proper relationship, said strain receiving surfaces being unbonded with the fillers adjacent thereto 9. An insulator comprising a non-conducting shell, a pin, said shell having a recess therein receiving one end of the pin, which recess has a strain receiving surface tapering inwardly towards the free end of the pin, cement filler within the recess and surrounding the pin to retain the pin in position within the shell, said shell having an outer strain receiving surface tapering in the same direction as the strain receiving surface of the recess, a cap embracing said outer strain receiving surface, cement filler within the cap and surrounding said outer strain receiving surface to retain the cap and shell in proper relationship, and yielding coatings separating the strain receiving surfaces from the fillers adjacent thereto.

10. An insulator comprising a non-conducting porcelain shell, a pin, said shell having a recess therein receiving one end of said pin, which recess has a strain receiving surface tapering inwardly towards the free end of the pin, cement filler within the recess and surrounding the pin to retain the pin in position within the shell, said shell having an outer strain receiving surface tapering in the same direction'as the strain receiving surface of the recess, a cap embracing said outer strain receiving surface, and cement filler within the cap and surrounding said outer strain receiving surface to retain the cap and shell in proper relationship, the strain receiving surface of the recess being unbonded with the flller within said recess.

11. An insulator comprising a non-conducting porcelain shell, a pin, said shell having a recess therein receiving one end of said pin, which recess has a strain receiving surface tapering inwardly towards the free end of the pin, cement filler within the recess and surrounding the pin to retain the pin in position within the shell, said shell having an outer strain receiving surface tapering in the same direction as the strain receiving surface of the recess, a cap embracing said outer strain receiving surface, a cement filler within the cap and surrounding said outer strain receiving surface to retain the cap and shell in proper relationship, said outer strain receiving surface being unbonded with the filler within the cap.

12. An insulator comprising a non-conducting porcelain shell, a pin, said shell having a recess therein receiving one end of said pin, which recess has a strain receiving surface tapering inwardly towards the free end ofthe pin, cement filler withi in the recess and surrounding the pinto retain the pin in position within the shell, said shell having therein receiving one end of said pin, the surface of said recess having strain receiving portions, cement filler within the recess and surrounding the pin to-retain the pin in position within the shell, said shell having an outer surface having strain receiving portions, a cap embracing said outer surface, and cement filler within the cap and surrounding said outer surface to retain the cap and shell in proper relationship, the strain receiving portions of the surface of the recess being unbonded with the filler within said recess.

14'. An insulator comprising a non-conducting porcelain shell, a pin, said shell having a recess therein receiving one end of said pin, the surface of said recess having strain receiving portions, cement filler within the recess and surrounding the pin to retain the pin in position within the shell, said shell having an outer surface having strain receiving portions, a cap embracing said outer surface, a cement filler within the cap and surrounding said outer surface to retain the cap and shell in proper relationship, the strain receiving portions of the outer surface being u'nbonded with the filler within the cap.

15. An insulator comprising a non-conducting therein receiving one end of said pin, which recess has strain receiving portions tapering inwardly towardsthe free end of the pin, cement filler within the recess and surrounding the pin to retain the pin in position within the shell, said shell having outer strain receiving portions opposed to,and tapering in thessame direction as, the strain receiving portions of the recess, a cap embracing said outer strain receiving portions, and cement filler within the cap and surrounding said outer strain receiving portions to retain the cap' and shell in proper relationship, said strain receiving portions being unbonded with the fillers adjacent thereto.

16. An insulator comprising a non-conducting porcelain shell, a pin, said shell having a recess therein receiving one end of the pin, which recess has a strain receiving surface tapering inwardly towards the free end of the pin, cement filler face of the recess, a cap embracing said outer strain receiving surface, cement filler within the cap and surrounding said outer strain receiving surface to retain the cap and shell in proper relationship, and a resilient coating separating the strain receiving surface ofthe recess from the filler therein.

17. An insulator comprising a non-conducting porcelain shell, a pin, said shell having a recess therein receiving one end of the pin, which recess has a strain receiving surface tapering inwardly towards the free end of the pin, cement filler within the recess and surrounding the pin to retain the pin in position within the shell, said shell having an outer strain receiving surface tapering in the same direction as the strain receiving 5 surface of the recess, a cap embracing said outer strain'receiving surface, cement filler within the cap and surrounding said outer strain receiving surface to retain the cap and shell in proper relationship, and a resilient coating separating the from the filler towards the free end of the pin, cement filler within the recess and surrounding the pin to retain the pin in position within the shell, said shell having an outer strain receiving surface tapering in the same direction as the strain receiving surface of the recess, a cap embracing said outer strain receiving surface, cement filler within the cap and surrounding said outer strain receiving surface to retain the cap and shell in proper relationship, and resilient coatings separating the strain receiving surfaces from the fillers adjacent thereto.

19. An insulator comprising a non-conducting porcelain shell, a pin, said shell having a recess therein receiving one end of said pin, the surface of said recess having strain receiving portions, cement filler within the recess and surrounding the pin to retain the pin in position within the shell, said shell having an outer surface having strain receiving portions, a cap embracing said outer surface, cement filler within the cap and surrounding said outer surface to retain the cap porcelain shell, a pin, said shell having a recess therein receiving one end of said pin, the surface of said recess having strain receiving portions, cement filler within the recess and surrounding the pin to retain the pin in position within the shell, said'shell having an outer surface having strain receiving portions, a cap embracing said outer surface, cement filler within the cap and surrounding said outer surface to retain the cap and shell in proper relationship, and a resilient coating separating the strain receivingportions of the outer surface from the filler within the cap and rendering them unbonded with the filler.

21. An insulator comprising a non-conducting porcelain shell, a pin, said shell having a recess therein receiving one end of said pin, the surface of said recess having strain receiving portions, cement filler within the recess and surrounding the pin to retain the pin in position within the shell, said shell having an outer surface having strain receiving portions, a cap embracing said outer surface, cement filler within the cap and surrounding said outer surface to retain the cap and shell in proper relationship, and resilient coatings separating the strain receiving portions of the surfaces from the fillers adjacent thereto and rendering them unbonded with the fillers.

ARTHUR O. AUSTIN.

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