JPH01214206A - Insulating spacer - Google Patents

Abstract

PURPOSE:To prevent breakdown or peeling due to temperature variation or shifted tightening, by setting the length of a bush shorter than the outer diameter at threaded section but longer than half thereof, and setting the outer diameter of an air gap section shorter than the outer diameter of the bush. CONSTITUTION:The inner diameter (d2) of air gap sections 7 provided at the upper and lower sections of a bush is set shorter than the outer diameter (d1) of the bush 8. The length (h) of the bush 8 is set shorter than the diameter (d0) of a stud 9 but longer than half of (d0). Consequently, lateral load due to temperature variation can be lowered and peeling at the interface 8a of the bush can be eliminated. When shifted tightening is made during assembly, tightening force is transmitted from the stud 9 to the interface 8a of the bush in the form of compression force thus preventing peeling of the interface.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an insulating spacer used for supporting conductors in gas-insulated switchgear.

(Prior Art) In general, an insulating spacer is provided between devices such as circuit breakers and disconnectors of gas-insulated switchgear to separate the gas and support conductors and switching parts. A conventional insulating spacer will be explained using FIGS. 3 to 5. As shown in FIG. 3, the insulating spacer 1 is integrally molded with the insulating part 1b so that the conductor support part 2 is located in the center, and the conductor support part 2 is connected to the conductor through the contact part 3. It has a structure that supports 4.

Next, as a method of fixing the flange portion 1c of the insulating spacer to the flanges Sa and 6a of the metal container 5.6, the method shown in FIG.
Publication No. 15).

In FIG. 3, metal cylindrical bushes 8 are integrally cast in the number of bolts on an insulating spacer, and studs 9 are passed through the bushes 8 and nuts 10 are attached to the tank flange 5a.

Tighten 6a. Here, as shown in FIG. 4, the bushing length h is made smaller than the thickness H of the spacer flange portion 1c, and a cavity 7 is formed in the bushing 8 with an inner diameter d2 larger than the outer diameter d of the bushing 8. Set up at Kabata. As a result, the spacer flange portion 1c and tank flanges 5a, 6a
The plating is performed on the flange surface 1d of the spacer. Since the flange surface 1d has a relatively large area when viewed as a whole of the spacer, the tightening force of the stud 9 is dispersed, allowing relatively uniform tightening on the flange surface. For this reason, the number of bolts is reduced and the tank flange surface 5a.

The number of man-hours required for machining the bolt holes 6a can be reduced and productivity can be improved.

However, this structure has the disadvantage that cracking is likely to occur at the interface 8a of the bushing 8 when the gas insulated switchgear is subject to temperature fluctuations. Gas insulated switchgear is generally assembled at room temperature, but when installed outdoors, the operating temperature can vary from approximately 120 to 80'', taking into account the effects of direct sunlight from midwinter to midsummer. . In general, the linear expansion coefficient of the insulating spacer 1 cast from a plastic material is larger than that of the tank flanges 5a and 6a. A relative displacement of .

Since the direction of relative displacement is simply reversed between the case where there is a temperature rise and the case where there is a temperature fall with respect to the assembly temperature, the case where there is a temperature fall will now be explained. In this case, since the spacer contracts in the radial direction more than the tank flanges 5a and 6a, the tank flange 5a
, 6a are displaced radially outward with respect to the spacer as shown by arrows in FIG. 4, causing relative slip on the flange surface 1d. This amount of displacement S depends on the size of the spacer, but is approximately on the order of 0.5o1 or less. This relative displacement is transmitted as a bending moment to the stud 9 via the nut 10, and acts to separate the bush interface 8a from the insulator IC.

Here, the distance from the seat surface of the nut 10 to the end surface of the bushing 8 is Q, and the stud diameter is do. To simplify this problem, it can be regarded as a problem in which a cantilever beam of length Ω fixed at the end face of the bush receives a concentrated load of W at its tip and is displaced by S, where W is from the mechanics of materials.

becomes. Here, E is the Young's modulus of the stud.

When the tank flange surface is displaced by S, W in formula (■) acts as a shearing force on the bushing, and WxQ becomes a bending moment. Therefore, in order to prevent the bushing interface 8a from being hollowed out, W in 20 must be need to be lower. As a countermeasure against this problem, it is effective to make dll smaller according to equation (2), that is, to make the stud thinner, or to make Ω larger. However, if the studs are made thinner, the number of studs must be increased in terms of strength as a pressure vessel, which does not lead to improved productivity.

On the other hand, by reducing the length h of the bushing, the strength can be increased. As shown in FIG. 5, if the bushing length h is extremely shortened, Q in equation (2) becomes large, so that the bushing interface is less likely to bulge due to temperature fluctuations. But the fifth
With the structure shown in the figure, there is a possibility that the bushing part will break during assembly. In other words, during assembly, a partial tightening condition occurs in which the spacer 1 is fixed to only one side of the tank (for example, 5a), but in this case, the tightening force F is generated in the direction of the arrow as shown in FIG. 5. The average shear path force at the bush interface generated by this F is ・=-1−■ πd1h, and when h is small, τ becomes large, which may cause peeling at the interface 8a or the corner of the insulator with low strength. Part 1e etc. may be destroyed. In order to avoid this, the above-mentioned publication
suggests 80 or more. In general, F is almost uniquely determined by do, and the general tendency is that F is proportional to the square of d, so if h is also made proportional to do in equation (■), τ
is almost a constant value.

The original aim of the structures shown in Figures 3 to 5 is to reduce the number of studs, but for this purpose, the studs must be made thicker in terms of strength as a pressure vessel, and as mentioned above, the shear of the bush interface must be increased. In order to keep the road force below a certain value,
As d increases, h also increases. Since the thickness H of the flange portion of the spacer is constant, the distance Ω from the bushing end face to the nut seat surface cannot be increased much by increasing h, and therefore W stated in equation (2) cannot be reduced.

(Problem to be solved by the invention) In other words, since we are constrained by two problems: the problem of peeling due to temperature fluctuations and the problem of peeling due to uneven tightening, etc., we have achieved the original aim of improving productivity by reducing the number of bolts. This is difficult with Honjuzukuri.

SUMMARY OF THE INVENTION An object of the present invention is to overcome the above-mentioned drawbacks, and to provide an insulating spacer with a stable structure in which the bolts are made thicker to reduce the number of bolts, and which does not cause breakage or peeling due to changes in humidity or uneven tightening.

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above object, in the present invention, the length of the bushing is equal to or less than the outer diameter of the threaded portion and is 172 mm larger than the outer diameter of the threaded portion.
With the above configuration, the outer diameter of the cavity is made smaller than the outer diameter of the bush.

(Function) As a result, the tightening force of the stud acts on the bush interface as compressive stress, preventing interfacial peeling.

(Example) An example of an insulating spacer according to the present invention will be described below with reference to FIGS. 1 and 2. The basic structure is the same as that of the prior art shown in FIGS. 3 to 5, so the same reference numerals are given and the explanation will be omitted. Further, FIG. 2 is an enlarged sectional view of the bushing portion shown on the right flange portion of FIG. 1.

The present invention is used for temporary tightening only in one part of the spacer fixing bolt, and in the other stud parts, the spacer part is used as a simple through hole and sandwiched between the flanges 5a and 6a, as shown in the left flange part in FIG. It can also be tightened.

In FIG. 2, integrally casting a bushing shorter than the thickness H of the spacer flange portion 1c is the same as in the prior art. However, in the prior art, the inner diameter d2 of the cavity 7 provided at the upper and lower parts of the bushing was larger than the outer diameter d1 of the bushing, but in the present invention, d2 is smaller than d□. Also, the length h of the bushing is less than or equal to the diameter d of the stud,
It will be 180 or more.

By making the length h of the bushing 8 as small as possible to d0 or less, it is possible to reduce the lateral load due to temperature fluctuations explained in equation (3), and it is possible to prevent separation from occurring at the bushing interface 8a. can.

Next, in the unevenly tightened state during assembly, the tightening force from the stud is transmitted to the bush interface as compressive force. Therefore, there is no peeling at the interface due to uneven tightening.

The bushing 8 is made of metal and has sufficiently high strength compared to insulators, and in terms of shear strength against force, h is d.
It is sufficient that it is less than 0, and it may be approximately the same as the height h' of the nut 10. For example, according to the JIS standard, the ratio of h' to do is about 60 to 80% for M16 screws and M20 screws, and this is sufficient for the shear strength of the bushing itself.

〔Effect of the invention〕

As explained above, in the present invention, by using a bushing that is shorter than the thickness of the resin part and by making the inner diameter d2 of the end gap smaller than the outer diameter d1 of the bushing, the tightening force of the tank flange is applied to the bushing interface. It is designed to act as a barrier and suppress peeling of the interface. Also, the bushing length h is the outer diameter d of the stand. By making the stud extremely short, less than T and more than T, the stud is made easier to bend.
Relative displacement in the radial direction between the resin part and the tank flange that occurs due to temperature fluctuations can be absorbed by the deformation of the stud, making it possible to provide an insulating spacer that is highly reliable even against temperature fluctuations.

The main purpose of the present invention is to increase the productivity of gas-insulated switchgear by increasing the thickness of the studs and reducing the number of studs. In order to reduce the number of studs, the studs must be made thicker, and the thicker the studs, the more
The effect of the present invention using extremely short bushings is significant.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of an insulating spacer showing an embodiment of the present invention, Fig. 2 is an enlarged sectional view of the right plunge part of the insulating spacer shown in Fig. 1, and Figs. FIG. 5 is a cross-sectional view of an insulating spacer in which the conventional technology is applied to the maximum extent. DESCRIPTION OF SYMBOLS 1... Insulating spacer, 2... Conductor support part, 3...
...Contact part, 4...Conductor, 5.6...Metal container, 5a, 6a...Tank flange, 7...Gap part, 8...Button, 9...Stud, 10. ... Nut, 1b... Insulating part of insulating spacer, 1c... Insulating spacer flange part, 1d... Insulating spacer flange surface. Agent Patent Attorney Ken Nori Chika Kendai Daishimaru 1 @ @ 2 Figure 3 E Figure 4 Figure 5

Claims (1)

[Claims] In an insulating spacer that is integrally cast with a bushing having a threaded part inside an insulator and fixed to the tank flange through the upper threaded part, the length of the bushing is equal to or less than the outer diameter of the threaded part and outside the threaded part. An insulating spacer characterized in that the diameter is 1/2 or more, and the inner diameter of the gap between the spacer flange surface and the bushing end face is smaller than the bushing outer diameter.