US1802704A - Insulator - Google Patents

Description

S. L. CASE A ril 28, 1931.

INSULATOR Original Filed March l7 192g INVENTOR Samuel L. Case.

ATTORNEY Patented Apr. 28, 1931 UNITED STATES.

PATENT oFFicE BAHUEL L. CASE, PALO ALTO, CALIFORNIA, ASSIGNOR T0 WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA msmua'roa I Application filed larch 17, 1922, Serial Na-544,471. Renewed October 80, '1930.

' My invention relates to insulators and par ticularly to. suspension insulators of the capand-pin type adapted for highpotent1al service.

One object of my invention is to provide an insulator of the above indicated character, that shall have a pin disposed in spaced relation to the walls of a recess therein and that shall be so constructed as to automatically center the pin during the.assembly thereof.

Another object of my invention is to provide a suspension insulator of the cap-and pin type in which the cap shall have a rela tivel long gripping surface on the insulating ody and in which tension load forces of the pin shall be so resolved into lateral components at a position deeply in the cap portions are homogeneous.

Anotherobject of my invention is to provide an insulator of the cap-and-pin type in which the heads of the cap, of the pin and of the insulating member shall be so constructed to have concentric sphericall curved portions to uniformly distribute di-electric stress radially between the ca and the pin to thereby increase the capacity of the insulator.

A further object of my invention is to provide an insulator that shall be simple and durable in construction, economical to manufacture and effective in its operation.

In practicing my invention, I provide an insulator of the cap-and-pin type in which the cap and the hollow insulating head are constructed to provide greater gripping surface.

The ends of the cap, insulating member and pin, at the closed end of the msulator, are

constructed to so uniformly distribute dielectrio stresses, between the cap and the pin, as to increase the capacitance of. the insulator. The pin is constructed to reduce the likelihood of fracturing the insulatin member by expansion forces and to resolveTongitudinal load forces into lateral components at a position deeply in the recess of the insulating head. The latter feature, in conjunction with the increased gripping surface of the cap provides the cement, WlllCh holds the pin, with greater shearing resistance and, consequently increases'the mechanical strength of the insulator.

The cap and the pin are provided with longitudinally and laterally spaced inner and outer diagonal annular surfaces which, in i any plane parallel to the insulator axis, may be represented by substantially parallel straight lines. The space between these surfaces is filled with solid material consisting of bonded parts, one of which .isa' portion of the side wall of the insulator head extending diagonally to said surfaces and substantially parallel to the insulator axis whereby it may be a solid of revolution without overhangin or undercut parts.

Furt er, the parts are so constructed as to automatically center the pin, in spaced relation to the walls of the pin recess, during assembly.

The single figure of the accompanying drawing is a side View, partially in section and partially in elevation, of two juxtaposed units of a suspension insulator embodying my invention.

An insulator constructed in accordance with my invention may comprise a plurality of juxtaposed units 1, the number of such units being dependent upon the potential of the line which is to be supported and insulated. Each unit 1 comprises a hollow body portion 2, a laterally extending petticoat portion 3, a cap member 4 and a pm member 5. The body portion 2 is tubular in form and has a closed end 6, the inner and outer surfaces of which are preferably spherically curved and concentrically disposed about a common center to render the end 6 of uniform thickness.

The cap member 4, having an eye orclevis portion for co-operation with a similar eye 'or clevis portion on the pin 5 of other similar of the portion 2. The cap 4 further comprises a lower portion 7 constituting a raised annulus or rim to provide an inwardly sloping surface 8, preferably at an angle of 45 with the longitudinal axis of the insulator. The portion 7 is rounded to have a relatively wide radius at its outer surface to avoid the concentration of dielectric stresses thereon.

Inner and outer sand belts or roughened annular zones 9 and 10, respectively, are provided in longitudinally offset relation on the surfaces of the insulating body 2.

The pin 5 comprises a shank portion of relatively small diameter. That is, the shank portion 18 onl of such diameter as to ensure suflicient mec anical strength and may be surrounded by a body of yieldable material 11. This construction reduces lateralexpansion forces of the pin to a minimum for an insulator of a given load.

The inner end of the pin'5 between which and the head of the body 2 a body of yieldable material 12 may be placed is provided with an enlarged head portion having a spherically curved surfaces 0 curved surface 14 and a frusto-conical portion 15, preferably sloped at 45 to the longitudinal axis of the insulator.

During assembly, when the pin 5 is placed in the insulating ortion 2, the spherically f the latter and of the pin serve to automatically center the shank of the pin 5 with res ect to the portion 2. After being so centere a body of cement 16 is placed in position around the pin.

The frusto-conical portion 15 serves to resolve the longitudinal tension load forces, in the pin 5, into lateral components, at a relatively great distance from the open end of the cap member 4, that extend diagonally from the pin, through the cement 16 and the body portion 2 to the surface 8, as indicated by the vector 17 on the lower unit 1. Vectors '18 and 19 illustrate the horizontal and vertical components, respectively, of the load forces in the insulator.

The above described arrangement of parts, whereby the longitudinal component, indicated by the vector 19. is materially reduced in value andthe shearing area, the length of which is represented by the length of the sand belt 10 in the direction of the vector 19, is materially increased, improves the mechanical strength of a pin-type insulator beyond that of any similar unit known to me.

Further, the surface 8 and the surface of the portion 15 are so related that an appree ciable ortion of the diagonal-component forces 0m one of these surfaces toward the solid of revolution havin electrical properties.

other lie coincident with the corresponding forces from the other surface and are widely distributed over these surfaces.

The vector 17 liesalong a frusto-conical element substantially at the center of the wall of a frusto-conical tube of the widely distributed diagonal component forces, the thickness of this wall being substantially defined bythe diagonal width of the surface 8 and the surface of the portion 15. Thus, the material between the latter surfaces is in substantially fiat compression.

'This material consists of portions of the body of cement 16, the wall portion 2 and the cement between the portion 2 and the cap 4 which are bonded together. Thus, an efl'ect is obtained similar to that which would be obtained if the cement and porcelain parts in the compression zone were all of one homogeneous' mass of porcelain, without, however, requiring a one-piece mass of porcelain with an undercut recess for the head of the pin 5 or an overhanging projection for longitudinal interlocking relation to the cap portion 7 In other words, the head portion 2 is 21 its side walls extending in the general dlrection of the insulator load axis, a structure which is easier and more. economical to manufacture than a porcelain piece havin overhanging or undercut portions and o taining substantially equivalent advantages.

Tests have been conducted in an insulator in which the petticoat portion 3 was twelve inches-in diameter and the other parts in proportion, as shown in the drawings, in which the pin 5 sheared off at over 23000 pounds tension and the insulating member did notbreak. An electrictal test of the illsulating member, conducted after the mechanical test, showed no impairment of its It can, thus, be seen that the mechanical test was limited only by the tensile strength of the pin 5 and that higher mechanical strength is possible to attain.

Cap-and-pin type insulators have here toforc been subject to mechanical failure by reason of irregularities in the cross-section of the insulating material at the inter-section of the body portion 2 with the petticoat portion 3. The stresses at thispoint ultimately fracture the insulator at the position of least cross-sectional area.

This objection has been eliminated in my insulator by constructing the region embraced by the curved surface 20 of uniform cross-sectional areas.

lVhile I have shown and described a par- What I claim as my invention is: 1. An insulator including a body having a longitudinal side surface extending in the general direction of theinsulator load axis,

' one sloping surface lying coincident with an appreciable portion of the forces extending from the other sloping surface, and means for preventing lateral displacement of the terminal members. I

2. An insulator including a tubular body having a longitudinal side surface extending in the general'direction of the tube-and-insulator-load axis, portions fixed to the inner and outer sides of said body, each having a surface of relatively great area sloping relative to said axis, one of said portions being bonded to said longitudinal side surface and being held in position solely by its bonded relation thereto, a pin-like terminal member in said body, and a terminal member having a portion around said body, each of said terminal members having a surface cooperating with and substantially conforming to. the sloping surface of its adjacent slopingsurface portion to resolve the longitudinal load forces into widely distributed com ponent forces extending diagonally to said longitudinal side-surface, an appreciable proportion of said diagonal forces extending from one sloping surface lying coincident with an appreciable portion of the forces extending from the other sloping surface.

- 3. An insulator including a tubular body having a longitudinal side surface extending in the general direction of the tube-and-' insulator-load axis, portions fixed to the inner and outer sides of said body, each having a surface 'of relatively great area substantially parallel to the other and sloping relative to said axis, one of said portions being bonded to said longitudinal side surface and being held in position solely by. its bonded relation thereto, a pin-like terminal member in said body, and a terminal memher having a portion around said body, each of said terminal members having a surface cooperating with and substantially conforming to the sloping surface of its adjacent sloping-surface portion to resolve the iongitudinal load forces into widely distributed component forces extending diagonally to said longitudinal side surface, an appreciable proportion of the diagonal forges extending from one sloping surface lying coincident with an a preciable portion of the iorces extending romthe other sloping surace.

4. An insulator including a head of substantially cup-shape having inner and outer longitudinal side surfaces of revolution generated by substantially straight lines, annular portions fixed to the inner and outer sides of said head, each having an annularsurface of relatively greatarea sloping relative to the longitudinal axis of the cup, one of said portions being bonded to one of said longitudinal side surfaces and bein held in position solely by its bonded relation thereto, a cap terminal member over said. head and a pin terminal member in said head, each of said terminal members having an annular surface cooperatin with and substantially conforming to the a jacent sloping surface onthe head to resolve the longitudinal load forces into Widely distributed component forces extending diagonally to said longitudinal side surfaces, an appreciable proportion of said diagonal forces extending from one sloping surface lying coincident with an appreciable portion of the'forces extending from the other sloping surface. 1

5. A suspension insulator including a head of substantially inverted cup-shape having inner and outer lon itudi-nal side surfaces of revolution generate by substantially straight lines, annular upper and lower portions fixed respectively, to the inner and outer sides of said head, each having an annular surface of relatively great area sloping relative to-the longitudinal axis of the cup, each of said por-' tions beingbonded to one of said longitudinal side surfaces and being held in position solely by its bonded relation thereto, a cap terminal member over said head and a pin terminal member in said! head, said cap and pin terminal members having, respectively, a lower annular inner surface and an upper annular outer surface co-operating with and substantially conforming to the adjacent sloping surface on the head to resolve the longitudinal load forces into widel distributed component forces extending iagonally to said longitudinal side surfaces, an appreciable proportion of said diagonal forces extending from one sloping surface lying coincident with anappreciable portion of the forces extending from the other sloping surface.

6. An insulator including a body having a longitudinal side surface extending in the general direction of the insulator load exis, portions held in substantially fixed relation to opposite sides of said body, having surfaces totalling substantial area at each of said sides sloping relative to said axis, one of said portions having a surface next to said longitudinal side surface substantially conforming thereto, terminal members for said portions having surfaces cootperating therewith and substantially con ormin to the sloping surfaces thereof to resolve t e longitudinal load forces into widely distributed component forces extending diagonally to said longitudinal side surface, an appreciable proportion of said diagonal forces extendmg from a sloping surface at one side of said body lying substantially coincident with an appreciable portion of the forces extending from the sloping surface at the other side of said body and means for preventing lateral displacement of the terminal members.

7. A suspension insulator including a dielectric head of inverted substantiall cupshape having a substantially hemi-sp erical closed-end wall and inner and outer longitudinal side surfaces of revolution generated by sweeping lines substantially throughout the inner and outer lengths of the head and merging gradually into, and substantially constituting continuations of, the inner and outer surfaces of said closed-end wall, said side surfaces being free from appreciable lateral shoulders at any position therealong, a

terminal cap bonded in position on the head having a substantially hemi-spherical inner surface at its upper end and an annular inner side surface ad aCent to its lower end sloping away from the insulator axis in the upward direction, a terminal pin having an annular inner-end longitudinal side surface of smaller diameter than the mouth of the head sloping away from said axis in the upward direction, said sloping cap and pin surfaces being substantially parallel each to each and lines radiating from the median circle of each being substantially coincident with corresponding lines from the other, said pin having a transverse inner-end surface substantially conforming to the inner-hemi-spherical surface of the head, said sloping surfaces being of substantial extent in the direction of slope, and a body of molded material between the head and the pin for holding the pin in position.

In testimony whereof, I have hereunto sub- I scribed my name this 8th day of March, 1922.

* SAMUEL L. CASE.

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