Electricity: conductors and insulators – Insulators – With terminal elements
Reexamination Certificate
1995-03-20
2001-10-23
Paladini, Albert W. (Department: 2841)
Electricity: conductors and insulators
Insulators
With terminal elements
C174S178000, C174S209000, C174S212000
Reexamination Certificate
active
06307157
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to composite insulators each formed by molding an elastic insulating material around an insulating rod having an end fitting connected to each of opposite ends thereof. The invention also relates to a process for producing the same.
(2) Related Art Statement
Recently, many composite insulators having light weight and high strength have been used. As shown in
FIG. 3
, the composite insulator includes an insulating rod
51
made of glass fiber-reinforced plastic (FRP) or the like, end fittings
54
crimped to opposite end portions of the insulating rod
51
, respectively, and an elastic insulating material
53
molded around the outer periphery of the insulating rod
51
. A plurality of shed portions
52
a
are integrally formed with sheath portions
52
b
from the insulating material
53
. Each of the end fitting grasps an end portion of the elastic insulating material
53
.
However, there is a problem when such a composite insulator is used in an existing power transmission system in which the entire length of the insulator is preliminarily determined, for example, a feeding system for railroads. That is, the entire length of the insulator to be used in the existing electric power transmission wire system is preliminarily determined, and if the above composite insulator is designed to have the thus preliminarily determined entire length, the composite insulator cannot satisfy an electric characteristic required as a reference value (Lightning impulse withstand voltage, e.g., 320 kV).
The reason why the electric characteristic of the composite insulator does not satisfy the reference value is that since the effective insulating length between the end fittings
54
is narrowed by themselves, an insulating effective insulating length cannot be sufficiently ensured. The effective insulating length between the end fittings
54
may be increased by increasing the the entire length of the insulating rod
51
and the molded elastic insulating material
53
. The term “effective insulating length” used therein means a longitudinal space between both the end fitting. However, in this case, since the entire length of the rod
51
, that is, the entire length of the composite insulator consequently increases, such an insulator cannot be used in the electric power transmission system in which the entire length of the insulator to be employed is preliminarily determined.
Further, in order to prevent invasion of water between the elastic insulating material
53
and the end fittings
54
in the composite insulator, it is necessary to provide a sealant
55
between the rod and the end fitting after the end fitting
54
is crimped around the rod
51
. This is very inefficient from a manufacturing second point.
SUMMARY OF THE INVENTION
The present invention has been accomplished to solve the above-mentioned problem, and a first object of the present invention is to provide a composite insulator which has enhanced insulation tolerance and maintains strength by increasing the effective insulating length without increasing the entire length of the insulator.
A second object of the present invention is to provide a composite insulator in which an insulating material is molded around an insulating rod and end fittings without leaking the insulating material outside.
A third object of the present invention is to provide a process for producing such composite insulators.
The composite insulator according to the present invention comprises an insulating rod, end fittings crimped to opposite end portions of said insulating rod, and an elastic insulating material molded around the outer periphery of the insulating rod, wherein each of said end fittings has a flange around the outer periphery of an end fitting body on an axially external side thereof, and said elastic insulating material is molded around the outer periphery of the insulating rod and those of the end fitting bodies such that the elastic material extends up to and between the flanges.
According to this composite insulator, since the insulating material is molded around a part of each of the end fittings as well as around the rod, the effective insulating length of the insulator can be increased without increasing the entire length of the insulator. Further, leakage of the elastic insulating material during the molding thereof can be prevented by the flange of the end fitting. In addition, sealing is effected, with the elastic insulating material, between the rod and a peripheral surface of a hole of the end fitting into which an end of the rod is inserted.
The following are preferred embodiments of the composite insulator according to the present invention.
(1) The outer peripheral surface of each of the flanges is substantially flush with that of the elastic insulating material. Since the outer periphery of the flange is substantially flush with the outer periphery of the insulating material, concentration of the electric field can be prevented to suppress corona discharging.
(2) A portion of the molded insulating material surrounding the end fittings is thicker than the remainder of the insulating material. Since that portion of the insulating material surrounding the end fittings is thicker than the remainder of the insulating material, insulation can be assuredly realized between both the end fittings.
(3) An area at which the end fitting is to be crimped around the outer periphery of the insulating rod is divided into a plurality of zones in an axial direction of the rod, and crimping pressures at said zones under which the end fitting is crimped around the outer periphery of the rod are reduced as the crimping location approaches the open edge portion of the end fitting. If a high pressure is applied around the rod at the open edge portion of the end fitting, a crack may be develop toward the center of the rod made of FRR.
The process for producing the composite insulator according to the present invention, which composite insulator comprises an insulating rod, end fittings around opposite end portions of said insulating rod, and an elastic insulating material around the outer periphery of the insulating rod, each of said end fittings having an axial hole therein and a flange around the outer periphery of an end fitting body on an axially external side thereof, said process comprising the steps of:
(1) inserting the insulating rod into said holes of the end fittings at opposite ends thereof;
(2) crimping the end fittings around the outer periphery of the insulating rod;
(3) placing the insulating rod having the end fittings inside a mold; and
(4) molding around the outer periphery of the insulating rod and the outer peripheries of the end fitting bodies such that the elastic material extends up to and between the flanges.
These and other objects, features and advantages of the invention will be appreciated upon reading of the following description in conjunction with the attached drawings, with the understanding that some modifications, variations and changes can be easily made by the skilled person in the art to which the invention pertains.
REFERENCES:
patent: 3898372 (1975-08-01), Kalb
patent: 4045604 (1977-08-01), Clabburn
patent: 4440975 (1984-04-01), Kaczergimski
patent: 5043838 (1991-08-01), Sakich
patent: 5220134 (1993-06-01), Novel et al.
patent: 491474 (1970-07-01), None
patent: 1932949 (1971-01-01), None
patent: 2553795 (1976-06-01), None
patent: 0439411 (1991-07-01), None
Sediver Catalogue, Toughened Glass And Composite Insulator Products.
Fujii Shuji
Kawamura So
Burr & Brown
NGK Insulators Ltd.
Paladini Albert W.
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