JPS6159414B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a bellows, and particularly to a molded bellows with a long service life.

BACKGROUND OF THE INVENTION Examples of devices using molded bellows (hereinafter simply referred to as bellows) include a vacuum chamber and disconnector as shown in FIG.

This type of vacuum cutter has a fixed electrode 15 at the inner end.
The fixed electrode rod 12 has an internal pressure of 13.33 mPa.
Vacuum vessel 1 evacuated to a pressure below (10 ^-4 Torr)
A movable electrode rod 13 is airtightly introduced into the vacuum vessel 11 via a bellows 14, and has an electrode 16 at its inner end that can freely come into contact with and separate from the electrode 15. By connecting and separating the electrodes 15 and 16, a large current is switched on and off.

By the way, the operation speed of the movable electrode rod 13 during the opening/closing operation is as high as 1.3 m/s when closed and 2.5 m/s when closed. Therefore, the impact during the opening/closing operation is large, and this impact is transmitted to the bellows 14, causing the bellows 14 to vibrate violently in the axial direction.
The peaks and valleys of the bellows 14 will be expanded and contracted repeatedly.

Additionally, vacuum shields and disconnectors are required to be durable enough to withstand repeated opening and closing tens of thousands of times over a long period of 20 years.

Bellows must withstand such harsh conditions, but in the unlikely event that the bellows breaks, the degree of vacuum inside the vacuum container will drop, and the function as a vacuum barrier or disconnector will be lost, allowing large currents to be switched on and off. Failure to do so may result in a major accident. For this reason, further improvement in the durability of the bellows is required.

Therefore, an object of the present invention is to provide a bellows that is difficult to break and has a long life.

The configuration of the present invention to achieve such an objective is as follows:
In a cylindrical metal bellows having multiple peaks and valleys, the radius of curvature r _o of the peaks and valleys at both ends of the bellows in a range of 20% of the total length of the bellows, and the peaks and valleys of other parts of the bellows. The relationship between the radius of curvature r _p and the radius of curvature r _o =r _p ×1.3 to 2.0, and the radius of curvature of the peaks and valleys is gradually increased toward the end.

Hereinafter, the present invention will be explained based on embodiments shown in the drawings.

The inventor conducted an experiment to investigate the destruction of the bellows in a vacuum shield and disconnector, and obtained the results shown in the second section.

In FIG. 2, the horizontal axis shows the total length l of the bellows, and the vertical axis shows the degree of breakage n (number of times), and it is a result of investigating which part of the bellows was broken.

The bellows used in the experiment were as follows.

Material: SUS304L Thickness: 0.2 mm Length: 300 mm Outer diameter: 60 mm Inner diameter: 40 mm Pitch: approx. 4.5 mm Number of peaks: 60 Radius of curvature of peaks and valleys: 1 mm The results of the bellows reciprocating speed at 1.3 m/s are shown in Figure 2. As shown by curve B, it was found that both end portions of the bellows (20% liter range) were extremely susceptible to destruction. Note that line A indicates the degree of fracture when there is no impact, and it can be seen that fracture occurs almost evenly over the entire length of the bellows.

Therefore, the inventor thought that if the strength of the 20% l range at both ends of the bellows, which is easy to break when an impact is applied, could prevent the bellows from breaking, that is, improve the durability of the bellows, I tried to solve the problem by increasing the spring constant of the bellows end.

That is, in order to increase the spring constant, an experiment was conducted to examine the durability of the bellows by making the radius of curvature of the peaks and valleys at the ends of the bellows larger than those near the center.

In the experiment, the radius of curvature of the peaks and valleys at the center in the axial direction of the bellows was set to r _p = 1 mm, and the radii of curvature at both ends in the axial direction of the bellows were
The radius of curvature r _o (>r _p ) of the peaks and valleys was varied within a range of 20%l. Other experimental conditions are the same as those of the previous experiment.

As a result, the results shown in FIG. 3 were obtained. In other words, if r _o = (1.3 to 2.0) x r _p , both ends are 20
It has been found that the life of the bellows is improved within the range of %l. Moreover, even if r _o /r _p is small, r
It has been found that even if _o /r _p is large, the life does not improve.

However, both ends of the bellows (20% x l range)
If the radius of curvature of the peaks and valleys in is made uniformly larger than that of the central part of the bellows,
It was found that simply moving the breakage position of the bellows from both ends to the boundary where the radius of curvature changes does not significantly improve the life of the bellows as a whole.

Therefore, the radius of curvature r _p of the peaks and valleys near the middle part of the plurality of corrugated parts formed over almost the entire length of the bellows is made constant, and the radius of curvature r The experiment was conducted by setting the radii of curvature r ₁ , r ₂ , and r ₃ of the valleys and crests of the range (range), respectively, which were gradually increased from the radius of curvature _{r p near} the middle part. As a result, the life of the entire bellows was improved, and a result similar to the line A in FIG. 2 was obtained.

An embodiment of the invention is shown in FIG.

In this example, r _p =1 mm, and both ends of the bellows are
The radius of curvature r _o of the peaks and valleys in the range of 20%×l, that is, the sizes of r ₁ , r ₂ , and r ₃ were set to the relationship r ₃ > r ₂ > r ₁ > r _p . Specifically, the dimensions were as follows.

r ₁ = 1.3 mm r ₂ = 1.5 mm r ₃ = 1.7 mm Other conditions were as follows.

Material: SUS304L Thickness: 0.2mm Length: 330mm Outer diameter: 60mm Inner diameter: 40mm Pitch: 4.5-7.2mm Number of threads: 60 As a result of the experiment, a result similar to line A in Figure 2 was obtained. The degree of breakage at both ends of the bellows has been greatly reduced, and the durability of the bellows has been significantly improved.

According to the present invention described above, both ends of the bellows
The radius of curvature r _o of the peaks and valleys in the range of 20% x l is set to r _o = r _p ×1.3 to 2.0, where the radius of curvature r _p of the peaks and valleys at the center of the bellows is Since the shape is gradually larger toward the sides, the number of springs near both ends is gradually larger than that near the middle part, and the stress due to the load and gradual impact load when the bellows expands and contracts does not concentrate at both ends, and can be adjusted appropriately. and is dispersed and absorbed as appropriate. Therefore, the life (durability) of the bellows can be further improved.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of the vacuum shield disconnector, Figure 2 is a graph showing the breakage position of the bellows, Figure 3 is a graph showing the life of the bellows versus the curvature radius ratio of the corrugated portion of the bellows, and Figure 4 is the book. FIG. 3 is an explanatory diagram showing an embodiment of the bellows according to the invention. 14...Bellows, 2...Waveform portion, 3...Mountain, 4...
valley.

Claims (1)

[Claims] 1. In a cylindrical metal bellows having a plurality of peaks and valleys, the radius of curvature r _o of the peaks and valleys at both ends of the bellows within a range of 20% of the total length of the bellows,
Radius of curvature r of peaks and valleys of other parts of the bellows
A bellows characterized in that the relationship with _p is r _o = r _p ×1.3 to 2.0, and the radii of curvature of the peaks and valleys are gradually increased toward the end.