JPH0963378A - Suspended insulator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent slipping-out of cement under an action of a low tensile load even when curing time of the cement is shortened, and effectively exhibit sufficient tensile breaking strength. SOLUTION: A suspended porcelain insulator is provided with a porcelain- made insulator 1 where ceramic quality sand 4 is adhered to an inside surface and an outside surface of a peripheral wall 3a in a hollow cylindrical head part 3. A cap metal fitting 5 and a pin metal fitting 6 are joined to the head part 3 of the insulator 1 by cement 7. The pin metal fitting 6 is positioned in the head part 3 of the insulator 1, and contains a large diameter end part having a taper surface. A metal plating layer is formed on a surface of the pin metal fitting 6, and an alkali-proof insulating coating film is applied onto the plating layer. A thickness of the insulating coating film is set in at least 7.5μm, preferably, in 7.5 to 20μm, and slipping-out of the pin metal fitting 6 under an action of a low tensile load is effectively prevented, and sufficient tensile breaking strength is exhibited.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention includes a hollow cylindrical head having a top wall and a peripheral wall, a surface of the base material is glazed, and a ceramic sand is adhered to the inner and outer peripheral surfaces of the peripheral wall. A porcelain insulator, and a cap fitting and a pin fitting joined to the head of the insulator by cement. The pin fitting is located inside the head of the insulator and has a large diameter. With regard to suspension insulators including ends, in particular, from the viewpoint of long-term reliability, porcelain destruction does not occur, and the tensile load value that causes the pin metal fitting to come out of the porcelain (so-called "cement removal") is greatly improved. It proposes a porcelain insulator that has been modified to obtain it.

[0002]

2. Description of the Related Art In order to increase the joint strength of a cap fitting and a pin fitting to an insulator in a suspended porcelain insulator, ceramic sand is adhered to the inner and outer peripheral surfaces of the insulator head to form a cap fitting and a pin fitting. 2. Description of the Related Art Suspended porcelain insulators, which are obtained by cementing an insulating material with cement, have pin fittings located in the head of the insulating material and include a large-diameter end portion having a tapered surface, have been widely known. In such a porcelain insulator, a cylindrical insulator head with a bottom for joining the insulator and the pin fitting rather than the cement filled in the cap fitting for joining the cap fitting and the insulator. The small amount of cement filled inevitably results in high stress per unit volume for the cement in the insulator head. for that reason,
In the prior art, it is common to cure the cement for a long time (typically about 24 to 48 hours) in order to increase the cement strength on the side of the pin fitting. In other words, if the curing time is shortened for the purpose of cost reduction by rationalizing the process and improving area productivity, the cement strength on the pin fitting side will be restricted, and sufficient tensile fracture strength to prevent cement loss will be developed. Becomes difficult.

[0003]

Therefore, the main object of the present invention is to prevent the cement from falling out under the action of a low tensile load even when shortening the curing time of the cement, and to obtain a sufficient tensile breaking strength. The present invention proposes an improved suspended porcelain insulator which can be realized in a desired manner and, as a result, cost can be easily reduced based on the rationalization of the process and the improvement of area productivity.

As is well known in the art, the loss of cement in a suspended porcelain insulator is governed by the magnitude of the shearing force at the interface of the sand adhered to the surface of the insulator, and the reduction in shearing force improves the strength of the removal. As a concrete means for that, it is effective to increase the "wedge force" of the pin fitting.

Then, in the process of searching for a technical means for solving the above-mentioned problems, the inventor suppressed the reaction between the hot dip galvanized layer applied to the surface of the pin fitting and the alkaline cement. At the same time, paying attention to the alkali-resistant insulation film, which is usually applied on the hot-dip galvanized layer, typically bituminous paint film, for the purpose of protecting the pin fittings from corrosion, and appropriately controlling the thickness of the film. In the case of carrying out the present invention, the "wedge force" of the pin metal fitting is increased by the sliding friction at the interface between the cement and the pin metal fitting, and the present invention was found for the first time to effectively act to improve the cement pull-out strength. Is.

[Means for Solving the Problems]

That is, the present invention includes a hollow cylindrical head having a top wall and a peripheral wall, and an insulator made of porcelain in which ceramic sand is adhered to the inner peripheral surface and the outer peripheral surface of the peripheral wall, and the insulation. A cap fitting and a pin fitting joined by cement to the head of the body, the pin fitting including a large diameter end located in the head of the insulator and having a tapered surface, and its surface In a suspension insulator having a metal plating layer and an alkali resistant insulating coating applied thereto, the thickness of the insulating coating is at least 7.5 μm, particularly preferably 7.5 μm to 20 μm.

As a known technique effective for increasing the "wedge force" of a pin fitting, for example, Japanese Patent Laid-Open No. 63-271831.
The gazette discloses design standards for cap fittings and pin fittings of suspension insulators, and when setting the outer diameter and the inner diameter of the cap fittings and pin fittings according to this standard, it is necessary to increase the size of the suspension insulator. It is possible to effectively exhibit sufficient tensile strength at break.
However, even when the criteria disclosed in the above publication are not always satisfied, it may be desirable to achieve the same advantage with high productivity. And, the present invention is different from the technique disclosed in the above publication, that is, by appropriately controlling the thickness of the alkali-resistant insulating coating applied on the surface plating layer of the pin fitting, It effectively develops sufficient tensile fracture strength without requiring upsizing and curing of cement for a long time, and also greatly improves long-term reliability.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below in detail with reference to the preferred embodiments shown in the accompanying drawings. The suspension insulator shown in FIG. 1 comprises an insulator 1 made of porcelain, and the surface of the base body of this insulator 1 is coated with glaze in a known manner. The insulator 1 is composed of a flange-shaped cap portion 2 extending outward in the radial direction, and a substantially cylindrical head portion 3 arranged in the center of the cap portion 2 and protruding upward. The head 3 has a cap 2 at the lower end.
And a top wall 3b continuous with the upper end of the peripheral wall 3a. Ceramic sand 4 is adhered to the inner and outer surfaces of the peripheral wall 3a. Furthermore, the cap metal fitting 5 is on the outer surface side with respect to the head 3,
Further, the pin fittings 6 are joined by cement 7 on the inner surface side. The pin fitting 6 is located in the head 3 of the insulator 1 and has a large-diameter upper end portion having a tapered surface, and a metal plating layer formed by hot dip galvanizing or the like is formed on the surface thereof, and the metal plating layer is formed on the metal plating layer. It is configured to be coated with bitumen paint as an alkali resistant insulating coating. Further, a buffer spacer 8 is interposed between the upper end surface of the pin fitting 6 and the inner surface of the top wall 3b of the head 3. The basic structure itself of such a suspension insulator is conventionally known, and in this case, the thickness of the alkali-resistant insulating coating on the pin fitting 6 is usually 5 μm or less in consideration of only the corrosion prevention of the pin fitting. It is said that.

As shown in FIG. 2, the sand 4 adhered to the inner surface and the outer surface of the head peripheral wall 3a of the insulator 1 is preferably manufactured by the following method. That is, first, a sand substrate is prepared in the same manner as in the conventional case, and dehydrated by a filter press to obtain a cake containing an appropriate amount of water. This cake is put into a kneading machine and kneaded to have a pore diameter of 1.8 to 2.0.
A noodle-shaped molded body is obtained by extruding from a perforated plate having a large number of through holes of about mm. The diameter of this compact is the same as or slightly larger than the maximum grain size of the intended sand. Next, this noodle-shaped molded product is dried, and is pulverized and sized by a coarse crusher and a de-sinter sizing machine into granules having substantially the same diameter as the diameter of the molded product. The de-sinter sizing machine is a device for crushing and sizing while rotating a drum provided with a large number of through holes. It is preferable that the diameter of the through holes in the drum is about 1.6 to 1.8 mm, and the rotation speed of the drum is about 200 rpm, which is much lower than in the usual case. The granules thus obtained are granules with few sharp edges, and the upper net has a size of 1.68 m.
m, the lower net is 0.84 to 1.0 mm, and the powder is screened through a sieving sieve, and then squeezed and baked. After that, the fired product is disentangled through a disintegrating sieve and finished as an insulator sand with few sharp edges. The method for crushing the sand for insulators is described in detail in, for example, Japanese Patent Publication No. 6-53601, so refer to the description in that publication as well.

As described above, in the present invention, the thickness of the alkali-resistant insulating coating (bitumen paint) applied on the surface plating layer of the pin metal fitting 6 is first noted to meet the reliability required for the suspension insulator. The thickness of the insulating coating is at least 7.5 μm, preferably 7.5 μm to 2 μm.
0 μm.

FIG. 3 shows the IEC standard No. 305 of U120
The thickness of the insulation coating on the suspension insulator that complies with BS,
A graph showing the relationship between the tensile fracture strength of insulators and FIG.
EC standard No. It is a graph which shows the relationship between the thickness of the insulation coating in the suspension insulator of 305 conforming to U300BS, and the tensile fracture strength of the insulator. Then, the thickness of the insulating coating is at least 7.5 μm, preferably 7.5 as described above.
The setting of μm to 20 μm is based on the empirical rule obtained from the experimental results shown in FIGS. 3 and 4.

That is, as shown in FIGS. 3 and 4,
Assuming that the tensile breaking strength is 100 when the alkali resistant insulating coating is not applied on the surface plating layer of the pin fitting 6, if the insulating coating has a thickness of 5 μm or less, there is almost no change in the tensile breaking strength. , The thickness of the insulating coating is 7.5 to 20
When the value is μm, the cement removal strength is 110 to 13
Improves to about 0%. This is because by increasing the thickness of the insulating coating, the "wedge force" of the pin fitting is made to give a greater compressive force to the cement at the interface of the sand 4 adhered to the surface of the insulator 1. Generally, the compressive fracture stress of brittle materials such as cement has 10 times the strength of the tensile fracture stress, and this property is utilized by the "wedge force" of the pin fitting. On the other hand,
If the thickness of the insulation coating exceeds 20 μm, the insulation 1
It is recognized that the fracture strength of the is decreased. This is because the "wedge force" of the pin fitting 6 becomes excessively large, so that the internal pressure applied to the inner surface of the head 3 becomes excessively large and the breaking strength of the insulator 1 is reduced. Originally, the breakdown strength of the insulator 1 tends to decrease with use over many years, and the function of mechanically supporting the power transmission line, which is required for suspension insulators, is maintained over a long period of time. In order to achieve this, a strength reduction must not occur in this type of breaking load test for a short period of time. Therefore, even if the tensile strength in the region of more than 20 μm is equal to or more than 15 μm of the insulating coating, its application is not preferable when considering the long-term strength.

As described above, according to the present invention, the pin fitting 6
By appropriately setting the thickness of the alkali-resistant insulating coating applied on the surface plating layer of the above within the range of 7.5 to 20 μm described above, the size of the suspension insulator and the long time of the cement on the pin metal 6 side can be increased. It is possible to effectively exhibit sufficient tensile fracture strength without requiring any curing. As a result, the cement curing time can be shortened, and the cost can be surely achieved by streamlining the process and improving the area productivity.

The above embodiment is merely an example and does not limit the present invention. Needless to say, the present invention can be implemented in various modifications within the scope.

[Brief description of drawings]

FIG. 1 is a front view of a suspension insulator to which the present invention can be preferably applied, showing a half portion thereof in cross section.

FIG. 2 is a flow chart showing a manufacturing process of a sand which can be used in the suspension insulator of FIG.

FIG. 3 is a graph showing the relationship between the thickness of the alkali-resistant insulating coating and the tensile fracture strength of the insulator in hanging insulators having different guaranteed strengths.

FIG. 4 is a graph showing the relationship between the thickness of the alkali-resistant insulating coating and the tensile fracture strength of the insulator in the suspension insulators having different guaranteed strengths.

[Explanation of symbols]

1 porcelain insulator, 3 hollow cylindrical head, 3a peripheral wall, 4 ceramic sand, 5 cap metal fittings, 6
Pin hardware, 7 cement

Claims (4)

[Claims] 1. A porcelain insulator including a hollow cylindrical head portion having a top wall and a peripheral wall, wherein ceramic sand is adhered to an inner surface and an outer surface of the peripheral wall, and a cement for the head portion of the insulator. The cap metal fitting and the pin metal fitting joined by the pin metal fitting are located in the head of the insulator and include a large-diameter end portion having a tapered surface, and the surface thereof has a metal plating layer and an alkali resistant insulation. A suspended insulator provided with a coating, wherein the insulating coating has a thickness of at least 7.5 μm. 2. A porcelain insulator including a hollow cylindrical head having a top wall and a peripheral wall, ceramic sand being adhered to the inner surface and the outer surface of the peripheral wall, and a cement for the head of the insulator. The cap metal fitting and the pin metal fitting joined by the pin metal fitting are located in the head of the insulator and include a large-diameter end portion having a tapered surface, and the surface thereof has a metal plating layer and an alkali resistant insulation. A suspended insulator provided with a coating, wherein the thickness of the insulating coating does not exceed 20 μm. 3. A porcelain insulator including a hollow cylindrical head having a top wall and a peripheral wall, ceramic sand being adhered to the inner and outer surfaces of the peripheral wall, and a cement for the head of the insulator. The cap metal fitting and the pin metal fitting joined by the pin metal fitting are located in the head of the insulator and include a large-diameter end portion having a tapered surface, and the surface thereof has a metal plating layer and an alkali resistant insulation. In a suspension insulator provided with a coating, the thickness of the insulating coating is 7.5 to 20.
Suspension insulator characterized by being μm. 4. The suspension insulator according to claim 1, wherein the insulating film is a bitumen paint.