CN1084032C

CN1084032C - Suspended insulator

Info

Publication number: CN1084032C
Application number: CN95118204A
Authority: CN
Inventors: 野崎宏; 久保田伦生
Original assignee: NGK Insulators Ltd
Current assignee: NGK Insulators Ltd
Priority date: 1995-08-25
Filing date: 1995-09-28
Publication date: 2002-05-01
Anticipated expiration: 2015-09-28
Also published as: JPH0963378A; CN2253861Y; CN1134026A

Abstract

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. 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 7.5&mu m, preferably, in 7.5 to 20&mu m, 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

Suspension insulator

The invention relates to a suspension insulator, comprising a porcelain insulator, a cap-shaped part and a pin-shaped part bonded to the porcelain insulator by adhesion, wherein the porcelain insulator comprises a hollow cylindrical head having a top wall, a peripheral wall and a pin-shaped part, glaze is applied to the surface of the body, ceramic sand grains are adhered to the inner peripheral surface and the outer peripheral surface of the peripheral wall, and the pin-shaped part is located in the head of the insulator and has a large-diameter end part with a conical surface. The present invention relates to a suspension porcelain insulator which is free from porcelain breakage in view of long-term reliability and can greatly improve a tensile load value when a pin-shaped component is pulled out from porcelain.

In order to increase the bonding strength between an insulator and a cap member and a pin member in a suspension porcelain insulator, there is known a suspension porcelain insulator in which ceramic sand grains are bonded to the inner and outer circumferential surfaces of the head of the insulator, the cap member and the pin member are bonded to the insulator by an adhesive, and the pin member is located in the head of the insulator and has a tapered large-diameter end portion. In such a porcelain insulator, the joint between the cap member and the insulator is achieved by filling the cap member with an adhesive, and since the amount of the adhesive filled in the bottomed cylindrical insulator head for joining the insulator and the pin member is smaller than the above-mentioned adhesive, it is necessary to increase the load stress per unit area of the adhesive in the insulator head, and therefore, in the conventional art, in order to increase the adhesive strength on the pin member side, it is generally necessary to maintain the adhesive for a long time (generally 24 to 48 hours), in other words, if the maintenance time is shortened, although the purpose of rationalizing the process and increasing the adhesive area per unit time can be achieved, it is difficult to have a sufficient tensile failure strength for preventing the pin from coming out due to the restriction on the adhesive strength on the pin member side.

Accordingly, an object of the present invention is to provide a suspension insulator which can prevent a pin-shaped component from being pulled out by a low tensile load even when the adhesive maintenance time is shortened, and which can sufficiently exhibit a sufficient tensile breaking strength, as a result of which the process can be rationalized, the bonding area per unit time can be increased, and the cost can be easily reduced.

As is well known to those skilled in the art, pin pull-out in insulators is primarily determined by shear forces at the interface of sand grains bonded to the insulator surface, with reduced shear forces improving pull-out strength, a particularly effective means of improving the "wedge force" (shear force) of the pin member.

In order to prevent the pin from being corroded by suppressing the reaction between the molten zinc coating on the surface of the pin and the alkaline binder in the process of solving the above-mentioned problems with the die line, the inventors coated a typical asphalt paint film as a general alkali-resistant insulating film on the molten zinc coating, and found that the "wedge force" (shearing force) of the pin is increased by the sliding friction at the interface between the binder and the pin when the film thickness is appropriately controlled, and the bond pull strength is effectively improved. Thereby, the inventive idea is achieved.

That is, the present invention provides a suspension insulator comprising a porcelain insulator, a cap member and a pin member bonded to the porcelain insulator by adhesion, wherein the porcelain insulator comprises a hollow cylindrical head having a top wall, a peripheral wall and a base surface, glaze is applied to the base surface, sand grains of porcelain are adhered to the inner and outer peripheral surfaces of the peripheral wall, and the pin member is located in the head of the insulator, has a large diameter end portion of a tapered surface, and is coated with a metal coating and an alkali-resistant insulator film on the surface thereof, characterized in that: the thickness of the insulating film is at least 7.5 μm, and particularly preferably 7.5 to 20 μm.

As a known technique effective for increasing the "wedge force" of the pin, for example, japanese unexamined patent publication No. 63-271831 discloses design criteria of a suspension insulator cover and the pin. According to this standard, when the outer diameter and the inner diameter of the cap member and the pin member are set, sufficient tensile failure strength can be effectively exhibited without increasing the size of the suspension insulator. However, even if the standard disclosed in the above publication is not necessarily satisfied, the same effect as described above can be achieved with high productivity. In addition, the present invention utilizes a method different from the technique disclosed in the above publication, that is, by controlling the thickness of the alkali-resistant film applied to the surface coating layer of the pin, the tensile rupture strength can be effectively improved without enlarging the insulator and maintaining the insulator for a long time with an adhesive, and the long-term reliability can be greatly improved.

Embodiments of the present invention are described below with reference to the drawings. Wherein,

fig. 1 is a front view of a suspension insulator of the present invention, with half shown in cross-section.

Fig. 2 shows a process for manufacturing a sand of the suspension insulator of fig. 1.

FIG. 3 is a graph showing the relationship between the thickness of the alkali-resistant insulating film and the tensile strength.

FIG. 4 is a graph showing the relationship between the thickness of the alkali-resistant insulating film and the tensile strength.

The symbols in the figures represent: 1-porcelain insulator, 3-hollow cylindrical head, 3 a-peripheral wall, 4-ceramic sand, 5-cover piece, 6-pin piece, 7-adhesive.

The suspension insulator shown in fig. 1 includes an insulator 1 made of porcelain, the surface of the base body of the insulator 1 is coated with glaze in a known manner, and the insulator 1 is composed of a flange-like umbrella portion 2 extending in the radial outer direction and a substantially cylindrical head portion 3 disposed at the center of the tip and protruding upward. The head 3 includes a substantially cylindrical peripheral wall 3a which is connected to the umbrella-shaped portion 2, a ceiling wall 3b connected to an upper end of the peripheral wall 3a, and ceramic sand grains 4 adhered to inner and outer peripheral surfaces of the peripheral wall 3 a. The cap-shaped member 5 and the pin-shaped member are bonded to the outer and inner peripheral sides of the head 3 with an adhesive 7. The pin-shaped member 6 is located in the head portion 3 of the insulator 1 and has a large-diameter upper end portion having a large tapered surface, and a metal coating layer of zinc or the like is formed on the surface thereof, and an alkali-resistant coating film made of asphalt paint or the like is further applied on the metal coating layer. Further, a rim punch washer 8 is interposed between the upper end surface of the pin-shaped member 6 and the inner surface of the top wall 3b of the head 3. The basic structure of such a suspension insulator is known in the art. The thickness of the alkali-resistant insulating coating film on the pin is usually 5 μm, considering only the problem of corrosion of the pin.

As shown in fig. 2, the sand adhered to the inner and outer peripheral surfaces of the head peripheral wall 3a of the insulator 1 is preferably produced by the following method. That is, first, the sand matrix is kneaded in the same manner as in the conventional technique, and dewatered by a filter press to form a cake containing a suitable amount of water. The cake was put into a kneading machine and kneaded, and then extruded from a perforated plate having a plurality of through holes each having a diameter of 1.8 to 2.0mm to obtain a noodle-like molded body. The diameter of the molded body is the same as or slightly larger than the maximum diameter of the target sand grains, and the noodle-shaped molded body is dried, and the molded body is pulverized and granulated by a coarse pulverizer or a splitting and granulating machine into granular bodies having substantially the same diameter as the molded body. The splitting and sizing machine is a device for rotating a drum provided with a plurality of through holes, and crushing and sizing the particles. The diameter of the through hole on the roller is 1.6-1.8mm, and the rotation number of the roller is far lower than the normal rotation number and is 200 rpm. The obtained granular material is small angular, and is placed on a whole sieve with upper mesh of 1.08mm and lower mesh of 0.84-1.0mm, and then sintered in a bowl. Next, the sintered product is placed on a screen for screening, and the insulator sand having a small edge angle is selected. The above-mentioned method for pulverizing the sand grains for insulator is described in detail in the above-mentioned Japanese patent publication No. 6-53601, and refer to the above-mentioned publication.

Fig. 3 and 4 are graphs showing the relationship between the thickness of the insulating coating film and the tensile rupture strength of the insulator. Wherein the suspension insulator of fig. 3 is made in accordance with IEC specification No.305-U120BS and the suspension insulator of fig. 4 is made in accordance with IEC specification No.350-U300 BS. The thickness of the insulating film is at least 7.5 μm, preferably 7.5 to 20 μm as described above, which is an empirical value obtained from the experimental results shown in FIGS. 3 and 4.

That is, as shown in fig. 3 and 4, when the tensile strength at break is 100 in the case where the alkali-resistant insulating film is not coated on the surface coating of the pin 6, the tensile strength at break is not changed at all when the thickness of the insulating film is less than 5 μm. When the thickness of the insulating film is 7.5-20 μm, the adhesive pull-out strength is increased to 110-130%. This is due to the fact that by increasing the thickness of the insulation film, the "wedge force" of the pin causes a greater compressive force of the adhesive on the surface of the insulation at the interface of the adhering grit 4. The brittle material, typically composed of an adhesive, has a compressive failure stress of 10 times its tensile strength, thus taking advantage of the above properties through the "wedge force" of the pin. On the other hand, if the thickness of the insulating film exceeds 20 μm, the dielectric strength of the insulator 1 tends to be lowered. This is because if the wedge force of the pin 6 is too large, the internal pressure applied to the inner surface of the head 3 is also too large, and the breaking strength of the insulator 1 is reduced. In the past, the insulator 1 had a tendency to decrease in breaking strength over a long period of time, and since the suspension insulator was intended to mechanically support the power supply line for a long period of time, such a breaking load test should not be performed in a short period of time. Therefore, the tensile strength exceeding 20cm is the same as that of the insulating film of 15 μm, but the thickness is not preferably larger than 20 μm in consideration of long-term use.

Thus, according to the present invention, by appropriately setting the thickness of the alkali-resistant insulating film coated on the surface of the pin 6 to be in the range of 7.5 to 20 μm, the tensile rupture strength of the insulator can be effectively increased without enlarging the suspension insulator with the adhesive on the pin side and without requiring long-term maintenance of the adhesive. Therefore, the maintenance time of the binder can be shortened, the bonding area per unit time is increased, the process is rationalized, and the cost is reduced.

The present invention is not limited to the above-described embodiments, but various changes can be made within the scope of the present invention.

Claims

1. A suspension insulator comprising a porcelain insulator, a cap member and a pin member bonded to the porcelain insulator by adhesion, wherein the porcelain insulator comprises a hollow cylindrical head having a top wall, a peripheral wall and a base surface, glaze is applied to the base surface, ceramic sand is adhered to the inner and outer peripheral surfaces of the peripheral wall, and the pin member is located in the head of the insulator and has a large-diameter end portion of a tapered surface, and a metal coating and an alkali-resistant insulator coating are applied to the surface of the pin member, characterized in that: the thickness of the insulating film is at least 7.5 μm.

2. A suspension insulator comprising a porcelain insulator, and a cap-shaped member and a pin-shaped member bonded to the porcelain insulator by adhesion, wherein the porcelain insulator comprises a hollow cylindrical head having a top wall, a peripheral wall and a base surface to which glaze is applied, ceramic sand is adhered to the inner and outer peripheral surfaces of the peripheral wall, and the pin-shaped member is located in the head of the insulator and has a large-diameter end portion having a tapered surface, and a metal coating and an alkali-resistant insulating member coating are applied to the surface of the pin-shaped member, characterized in that: the thickness of the insulating film is not more than 20 μm.

3. A suspension insulator comprising a porcelain insulator, and a cap-shaped member and a pin-shaped member bonded to the porcelain insulator by adhesion, wherein the porcelain insulator comprises a hollow cylindrical head having a top wall, a peripheral wall and a base surface, glaze is applied to the base surface, ceramic sand is adhered to the inner and outer peripheral surfaces of the peripheral wall, and the pin-shaped member is located in the head of the insulator and has a large-diameter end portion having a tapered surface, and a metal coating and an alkali-resistant insulating member coating are applied to the surface of the pin-shaped member, characterized in that: the thickness of the insulating film is at least 7.5 μm.

4. A suspension insulator according to any one of claims 1 to 3, wherein: the insulating film is asphalt paint.