US 3549791 A
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Description (OCR text may contain errors)
United States Patent  Inventor EdwardH.Yonke|'s 3,325,584 6/1967 Herzig.......................... I74/l79X Glencoe,lll.
FOREIGN PATENTS Chicago, Ill. a corponfion of Illinois Primary Exammer-Laramre E. Askm Attorney-Mason, Kolehmainen, Rathburn and Wyss eeea CCCm nnn mmm FFFG 8568 255 9999 1111 ///l 0240 l 1 9272 72003 .2 07 8 5920 60 3 11 o C V- I n. n. u S d n 80 67A 99 l ll w z 22n v -V. y m 7M J a de mm 1 8 P i Pmm$ AFPA 1.11.] 253 2247 [[[1  PROTECTED ROD INSULATOR WITH SOFT ELASTOMER FILLER ABSTRACT: There is provided a suspension insulator for 3 Claims, 5 Drawing Figs.
power transmission application including a central tension rod of nonconducting material such as of glass fibers. End fittings are secured to the respective ends of the tension rod. A number of insulator members are strung in axial relation on the tension rod. The insulator members each include a sheath spaced from the rod. The space between the rod and the sheaths is filled with soft-elastomer filler and the filler is s 9 %M0 7 3 1 7 I 4 4 70 I -D l m l 9 H 0 m NW N WW9 n ""7 n m L 0 W d U U he .1 1:1 2 I10 5 55 .l [.1
pring  References Cited UNITED STATES PATENTS 1/1963 Moussou loaded by suitable compression means to maintain void-free interface between the elastomer filler and the rod and 174/179 between the elastomer filler and the insulator members.
ril /71791717175 7? I ill/1411 741 1? The present invention relates to an elongated suspension insulator, and more particularly to a'unitary suspension insulator of the type employing a central tension member and suitable for power transmission applications.
Although porcelain as conventionally used in insulator members has excellent weather and track resistance and therefore has been used for decades in supporting transmission lines, nevertheless there are severe mechanical limitations on the use of such porcelain insulators.
Accordingly it is an object of the present invention to provide an improved suspension insulator having improved mechanical-supporting properties.
A further object of the present invention is the provision of a new and improved suspension insulator.
Further objects and advantages of the present invention will become apparent as the following description proceeds and the features of novelty which characterize the invention will be p'ointed out with particularity in the claims annexed to and forming a part of this specification.
In accordance with these and many other objects of the present invention, there is provided a unitary suspension insulator including a central tension rod of nonconducting material such as of polymer bonded axially aligned glass fibers as the tension element. End fittings secured to the respective ends of the glass fiber rod are adapted for connecting a conductor to the power transmission structure. Suitable juxta-positioned in sulator members of porcelain or other suitable material are strung in axial relation on the tension rod, each including a hollow sheath and a hood. The sheath ofeach insulator is spaced-apart from the rod and the space between the rod and sheath is filled with soft-elastomer filler such as a urethane elastomer. Spring loading of the filler assures that the interfaces between the glass fiber-elastomer and the elastomer-porcelain are kept in void-free tightness under all ambient conditions so that moisture and contaminants are not permitted ingre ss and leakage currents and flashover currents occur outside of the porcelain.
For a better understanding of the present invention, reference may be had to the accompanying drawings wherein:
'FIG. 1 is an elevational view of a suspension insulator according to the present invention;
FIG. 2 is a fragmentary cross-sectional view of the suspension insulator of FIG. 1', drawn to a larger scale;
FIG. 3 is a cross-sectional exploded perspective view of an end of the suspension insulator of FIG. 1;
FIG. 4 is a cross-sectional view of the suspension insulator of ,FIG. 1, taken along line 4-4 of FIG. 2; and
FIG. 5 is a fragmentary cross-sectional perspective view of the suspension insulator illustrating one of the insulator members strung on the tension rod.
Referring now to the drawings, there is illustrated an elongated suspension insulator assembly including a string of insulator members 12 of suitable material such as porcelain. The string of insulator members 12 is held together by a central tension rod 14 of suitable material such as of polymer bonded axially aligned glass fibers. The rod 14 terminates in suitable end fittings 15, which may be similar to those described and claimed in my copending application for Letters Patent of the U.S. Ser. No. 733,131, filed May 29, 1968, now U.S. Pat. No. 3,534,989, filed even date herewith entitled END FITTING.
As is conventional in the insulator art, each of the insulator members 12 includes a generally elongated sheath portion 16 and an enlarged hood portion 17. The sheath portion is formed with an axial opening 18 terminating in a bell-shaped chamber 19, FIGS. 2 and 5, to provide an expansion chamber. The space between the tension rod 14 and the axial opening 18 is filled with a soft elastomer such as a urethane elastomer filler 20.
As best illustrated in FIG. 2, the insulator members 12 are juxtaposed in axial relation so that the sheath end of one insulator member is received within the bell-shaped chamber of the adjacent insulator member permitting relative movement of the insulator members to each other. A metal washer 21 may be provided to close and seal the space between the sheath end of an insulator member and the adjacent bellshaped chamber 19.
The end fittings 15 may be of any suitable configuration, but in the illustrated embodiment include an outer housing 23 tapered on its inner surface to receive a collet assembly 24 gripping the end of the tension rod 14 by wedge action.
To maintain a void-free interface between the tension rod 14 and the filler 20 and between the filler 20 and the axial opening 18 of the insulator members 12, the filler 12 is maintained under compressive load by suitable compression springs 28 and 29. The upper string 28 acts between a spring cover 30 and an upper clevis member 31 secured to the outer housing 23 of the upper end fitting 15, and the uppermost one of the insulators 12. The lower compression spring 29 acts between a tongue member 33 secured to the outer housing 23 of the lower one of the end fittings I5 and a lower spring cover 34 which in turn bears against the filler 20 in the lowermost one of the insulator members 12. Thus the tiller 20 is constantly' under compression by the compressive force of the springs 28 and 29. 7
It will be understood that the relatively large expansion chambers 19 formed in the lower end of the sheath portion 16 minimize axial expansion of the filler 20 due to ambient temperature changes. Moreover the spring loading of the filler 20 insures void-free interfaces between the glass fiber rod 14 and the elastomer filler 20, and between the elastomer 20 and the porcelain of the insulator members 12. Leakage currents and flashover currents must occur outside the porcelain. Tests have indicated a slightly higher flashover value for the instant insulator string as compared to a conventional insulator string employing similar insulator members. Advantageously the suspension insulator according to the present invention provides positive and reliable mechanical loading. Moreover since the mechanical integrity of the string is maintained even though an insulator may break, there is no danger of dropping a power line upon cracking or failure of an insulator member, and therefore there is less urgency for replacing insulator strings with damaged insulator members. In addition since there is no porcelain puncturing, the insulator string may be made with a lower weight, provides less possibility of porcelain damage, and may be manufactured at considerably less cost than standard cap and pin suspension insulators.
Although the present invention has been described by reference to only a single embodiment thereof, it will be apparent that numerous other modifications and. embodiments will be devised by those skilled in the art which will fall within the true spirit and scope of the present invention.
1. An elongated suspension insulator comprising:
a central tension rod of nonconducting material;
end-fitting means secured to respective ends of said tension rod;
a plurality of juxtaposed insulator members strung in axial relation on said tension rod, each including a hollow sheath and a hood, the sheath of each insulator member being spaced from said rod;
soft-elastomer filler entirely filling the space between said rod and said sheath:
the opening in each sheath being formed with a bell-shaped chamber to provide for expansion of said elastomer and loosely receiving the opposite end of an adjacent sheath for relative movement therewith.
2. An elongated suspension insulator as set forth in claim 1 including compression spring means acting between at least one of said end fitting means and said elastomer to compression load said elastomer permitting expansion thereof against the bias of said spring. 7
3. An elongated suspension insulator comprising:
a central tension member of nonconducting material;
tension member and said insulator members; and an expansion chamber for said elastomer formed in each of said insulator members.