JPH07272572A - Multi-ring type shield and its air-tightness testing method - Google Patents

Abstract

PURPOSE:To lessen the labor of installation work and remarkably lessen the labor for testing air-tightness. CONSTITUTION:A plurality of hollow rings 1 which compose a shield are unitedly connected by a hollow supporting part and the inner spaces 1a of respective hollow rings 1 are communicated one another. The air-tightness of all the hollow rings 1 are simultanesously tested by increasing or decreasing the pressure of the inner spaces 1a through an open part 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-ring type shield for relaxing an electric field at the head of a power device such as a bushing and an airtightness test method therefor.

[0002]

2. Description of the Related Art The multiple ring type shield as described above is
It is made of a thin hollow ring made of thin light metal so that it will not be overweight in consideration of earthquakes. Such a hollow ring can be made by bending a pipe in the case of a small one, but in the case of a thick one with a high shielding effect, such a forming is impossible, so that a pair of upper and lower drawn rings are drawn. It is manufactured by welding half-split pipes. For this reason, if welding is incomplete, water may penetrate into the interior from that portion and freeze, causing a trouble of breaking the hollow ring.

The conventional multi-ring type shield consists of independent hollow rings. Therefore, in order to prevent the above-mentioned accident, it is necessary to perform an airtight test in advance for each hollow ring, which requires a lot of trouble. Further, it is necessary to attach the hollow rings, which have been subjected to the airtightness test, one by one to the tip end portion of the bushing or the like, but this work is a work at a high place, so the workability is poor.

Therefore, the present inventors have previously developed a multiple ring shield having an integral structure in which the hollow rings 11 are connected to each other by a columnar support member 12 as shown in FIGS. 4 and 5. With such a structure, it is not necessary to attach the hollow rings 11 to the tip of the bushing or the like one by one, so that the number of mounting operations can be reduced. However, in this case as well, the airtightness test must be individually performed on each hollow ring 11, which is the same as in the conventional case, and therefore, there is no change in that it requires a lot of trouble.

[0005]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the prior art and not only can reduce the number of steps for attaching to a bushing or the like, but also greatly reduce the number of steps for an airtight test. The purpose of the present invention is to provide a multi-ring type shield that can be used and an airtight test method therefor.

[0006]

In order to solve the above-mentioned problems, the multiple ring type shield according to claim 1 has a structure in which a plurality of hollow rings constituting the shield are integrally connected by a hollow support member. It is characterized in that the inner spaces of the hollow ring are communicated with each other. Claim 2
The airtightness test method for a multi-ring type shield of, wherein the inner space of each hollow ring is pressurized or depressurized from an opening formed in a part of the multi-ring type shield according to claim 1,
The airtightness of each hollow ring is tested simultaneously.

[0007]

Since the multi-ring type shield of the present invention is wholly integrated, it can be attached to the tip of a bushing or the like all at once, and the number of attaching operations can be reduced. Moreover, since the inner space of each hollow ring is made to communicate with each other through the hollow support member, by introducing gas into the inner space of each hollow ring from the opening or sucking air from the inner space, The hollow ring can be pressurized or depressurized simultaneously. Therefore, the airtightness of all hollow rings can be tested at the same time, and the number of steps of the airtightness test can be reduced.

[0008]

The present invention will be described below in more detail with reference to the illustrated embodiments. In FIGS. 1 and 2, 1 is a plurality of hollow rings for constructing a multiple ring type shield, and 2 is a hollow support member composed of a vertical column 3 and a horizontal arm 4. Each hollow ring 1 is not only connected to and integrated with this hollow support member 2 by a method such as welding, but the inner space 1a of each hollow ring 1 also has an inner space 2a of the hollow support member 2 They are in communication with each other through.

The mounting plate 5 provided on the upper end of the support member 2 is formed with an opening 6 communicating with the internal spaces 1a and 2a. Since this opening 6 is only used in the airtightness test, it is sealed by an appropriate means such as a plug after the end of the airtightness test.

In the multi-ring type shield thus constructed, the gas such as the pressurized air can be introduced into the inner space 1a of each hollow ring 1 at the same time by introducing the gas such as the compressed air from the opening 6. The airtightness of each hollow ring 1 can be tested at the same time by, for example, immersing the inside of a water tank. Further, by coating the surface of each hollow ring 1 with soapy water or the like, the air tightness test can be performed without using a water tank. As another method, the air inside the inner space 1a of each hollow ring 1 is evacuated from the opening 6 by a vacuum hoop to make a vacuum and then the opening 6 is closed, and the degree of vacuum that decreases with time is measured with a vacuum gauge. It is also possible to judge whether the airtightness is good or not by using the above method or by using a sensor (He leak detector or the like) which uses helium gas or the like in a vacuum state. According to this method, it is possible to specify the position of the defect and there is an advantage that there is less danger as compared with the pressing method.

Moreover, since the entire multi-ring type shield is integrally formed by the supporting member 2, the whole mounting member 5 can be attached to the tip of the bushing 7 or the like at once by using the mounting plate 5 as shown in FIG. It is also possible to reduce the number of installation work steps. 4 and 5, the horizontal arm 13 of the support member 12 is plate-shaped, but in the present invention, since the horizontal arm 4 of the support member 2 is tubular, its section modulus Z is the horizontal arm 13. Can be greater than. For this reason, the wall thickness of the horizontal arm 4 can be reduced, and the weight of the entire shield can be reduced, which also contributes to the improvement of seismic performance.

[0012]

As described above, the multi-ring type shield of the present invention can reduce the number of steps for attaching it to a bushing or the like, and by adopting the airtightness test method of the present invention, The number of tests can also be greatly reduced. The present invention can exert a particularly great effect when applied to a shield made of a light metal such as aluminum whose surface is polished to improve the electric field relaxation performance, and the polishing powder easily hides defects.

[Brief description of drawings]

FIG. 1 is a partially cutaway perspective view showing an embodiment of the present invention.

FIG. 2 is a partially cutaway front view showing an embodiment of the present invention.

FIG. 3 is a front view showing a mounting state on a bushing.

FIG. 4 is a partially cutaway perspective view showing a previously developed product.

FIG. 5 is a partially cutaway front view showing a previously developed product.

[Explanation of symbols]

1 hollow ring, 1a internal space, 2 support member, 2a internal space, 3 vertical column, 4 horizontal arm, 5 mounting plate, 6 openings, 11 hollow ring, 12 columnar support member, 13 horizontal arm

Claims (2)

[Claims] 1. A multi-ring type shield, wherein a plurality of hollow rings forming a shield are integrally connected by a hollow support member, and the inner spaces of the hollow rings are communicated with each other. 2. The airtightness of each hollow ring is simultaneously tested by pressurizing or depressurizing the inner space of each hollow ring through an opening formed in a part of the multi-ring type shield according to claim 1. Airtight test method for multiple ring shields.