JPS5958268A - Flat lid for container for very high degree of vacuum - Google Patents

Abstract

PURPOSE:To avoid a large deformation due to pressure or load and prevent bolts from yielding, by providing a grooved portion inside the portion of a flat lid, which is brought into contact with a metal gasket and by making the section modulus of the grooved portion smaller than that of the portion clamped by the bolts. CONSTITUTION:The section modulus of bolts 5 is made larger than that of a grooved portion 10a so that even if a large thermal deformation occurs, the bolts and a clamped portion 10b located in contact with a hollow metal O-ring 1 are scarcely deformed and only the groove portion is deformed. The temperature difference between the inside and outside of the grooved portion 10b is small. Since the number of times of baking in a high-degree vacuum container or the like is small in general, the yielding of the grooved portion 10a could occur only in its surface part and cause little trouble to the whole body. Because the width of the groove 10a is small, the increase in the quantity of deformation of a flat lid 10 due to pressure or load is minute.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to improvements in flat plate lids that seal fluids using metal gaskets in ultra-high vacuum containers, high-temperature containers, and cryogenic containers.

[Technical background of the invention]

High vacuum machines such as nuclear fusion devices and particle accelerators generally have a
An ultrasonic vacuum of 0 Torr is required. Therefore, when the equipment is in a vacuum, baking is usually performed at about 100°C to 350°C in order to reduce the amount of gas released from the equipment surface. Therefore, metal sockets are generally used in these ultra-high vacuum devices. Rubber gaskets are avoided because they have poor heat resistance and gas permeability at the above temperatures. On the other hand, metal gaskets are also used in high-temperature equipment and cryogenic containers for superelectric magnets and the like from the standpoint of heat resistance and low temperature resistance.

By the way, there are various shapes of metal gaskets, but among them, metal hollow O-rings are often used because they have relatively low rigidity and a large amount of elastic deformation. 1st
The figure shows a cross-sectional view of an example of a conventional vacuum container having a rectangular flat plate lid using this metal O-ring.

In the figure, 1 is a metal hollow O-ring, 2 is a part of the vacuum vessel, and a flange 2aVC of the vacuum vessel 2 is provided.
A metal hollow O-ring 1 is mounted on j2b. The vacuum container 2 also has a flat lid 3 to which various devices 4 are attached.
However, when it is attached with a fastening gel 5, it is closed. Furthermore, in the case of an ultra-high vacuum container, in order to perform baking, an electric sheathed heater 6 is wrapped around the outer periphery of the vacuum container 2 and the flat lid 3, and the vacuum container 2 and the flat lid 3 are kept warm by a heat insulating material 7. In this case, the thickness of the flat plate lid 3 needs to be appropriate in relation to the size and number of bolts 5 to be fastened in order to obtain an appropriate contact sealing surface pressure of the metal hollow O-ring 2. Of course, this is determined in consideration of the pressure on the various devices 4 mounted on the flat plate lid 3, the influence of deformation by the cart, etc.

In the flat plate lid of such a container, during the heating and cooling process during baking, a temperature difference occurs between the front and back of the flat plate lid 3 and the inner and outer peripheries, and a maximum bending moment is generated in the gel fastening part, causing the bolt 5 or the flat plate M3 to It may also yield due to thermal stress. FIG. 2 and FIG. M3 show the deformation modes of the flat plate lid 3 when the temperature rises and when the temperature falls, respectively. As shown in the figure, when the temperature rises, the front surface becomes hotter than the back surface and deforms into a convex shape, while when the temperature rises, the back surface is vacuum insulated, so the temperature of the front surface becomes lower than the back surface. Deforms into a concave shape.

However, if the strength of the bolt fastening part is high and the bolt does not yield, no leakage occurs, but the bolt fastening part generally has lower strength than the flat plate lid 3 portion. Therefore, it becomes impossible to completely fix the gel fastening portion, and the gel 5 yields and stretches by the amount equivalent to thermal deformation. If the elastic deformation of the hollow metal O-ring 1 is greater than the elastic deformation of the hollow metal O-ring 1 due to the expansion of the gel 5, a large leak will occur.

[Problems with background technology]

For the above reasons, the deformation mode is axially asymmetric not only in large containers but also in the case of square containers, so the deformation mode is complicated and leaks often occur even in small containers.

As mentioned above, in conventional flat plate lids, plates with uniform thickness are used, and the strength of the bolt fastening part is lower than that of the flat plate part, so sometimes a large stress is generated in the bolt 5, causing it to yield. There may be leaks.

[Purpose of the invention]

The present invention was made in view of the above circumstances, and its purpose is to reduce the stress applied to the bolt without increasing the deformation due to pressure or load, and to reduce the deformation of the metal hollow O-ring part. An object of the present invention is to provide a flat plate lid for an ultra-high vacuum valley device which does not cause any leakage and does not affect the environment.

[Summary of the invention]

In order to achieve the above object, the present invention is characterized in that a groove is provided in a portion of the flat plate lid body inside the metal gasket contact portion, and the section modulus of this groove is smaller than the section modulus of the gel fastening section. shall be.

[Embodiments of the invention]

An embodiment of the present invention shown in the drawings will be described below.

FIG. 4 is a sectional view showing an example of the structure of the flat plate lid according to the present invention;
FIG. 5 shows a view taken along arrows ①-v in FIG. 4, respectively.

In the figure, a groove portion 10a is provided in a portion of the rectangular flat plate lid body 10 that is inside the metal gasket contact portion. In the case of a rectangular shape as shown in this example, the groove portion 10 m is provided so that the thick portion is approximately square. Moreover, the groove portion 10 a in this case
The plate thickness t of is set to a value that satisfies the following conditions.

Here, zb is the section modulus of the gel for one pitch of the bolt fastening portion, and P is the pitch of the bolt.

Next, the operation of the present invention configured as described above will be explained. In other words, the section modulus of the bolt 5 is 10. Since it is larger than a, even if large thermal deformation occurs, the fastening portion 1 will come into contact with the bolt 5 and the metal hollow O-ring 1.
0b hardly deforms, and the deformation can be avoided in the groove 10a.

Furthermore, the temperature difference between the front and back sides of the groove portion 10a is also reduced.

Generally, such equipment is baked only a few times, so even if the groove portion 10a were to yield, it would only be on the surface, and there would be no problem as a whole. Further, since the width of the groove portion 10a is small, the amount of deformation of the flat plate lid main body IO due to pressure and load is very small.

Next, FIG. 6 shows another embodiment of the present invention.

In other words, the bolt fastening part 10b'Ilr is made thicker, the thin plate 10c is made thinner, and a rib 1 is provided. In this case too, the rib 1 is connected to the bolt fastening part 10.
The same effect as described above can be obtained by providing a relief 12 for preventing deformation without welding to b.

〔Effect of the invention〕

As explained above, according to the present invention, a groove is provided in the inner part of the flat plate lid body than the metal gasket contact part, and the section modulus of this groove is smaller than the coefficient of the bolt fastening part. This prevents the bolt from yielding due to thermal deformation when the temperature rises or falls without increasing deformation due to pressure or load, and is extremely reliable as it does not cause any leakage and does not affect the deformation of the metal hollow O-ring. It is possible to provide a flat plate lid for an ultra-high vacuum container that has excellent durability and maintainability.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a conventional vacuum container, FIGS. 2 and 3 are views showing deformation modes, FIG. 4 is a sectional view showing an embodiment of the present invention, and FIG. 5 is a sectional view of the conventional vacuum container. The v-■ arrow view and FIG. 6 are cross-sectional views showing other embodiments of the present invention. 1... Metal hollow O-ring, 2... Vacuum container, 3
．． 10... flat plate lid body, 5... fastening bolt, 6...
・Electric sheathed heater, 7... Insulating material, IOa... Groove portion, 10 b... Bolt fastening portion, 10 c... Flat plate thin section, 11... Rib, 12... Relief for preventing deformation Department. Applicant's agent Patent attorney Rin Oshiki Chapter Section 2 Figure 3 Section 4

Claims (2)

[Claims] (1) In a flat plate lid that is fastened by a bolt to a container using a metal gas foot such as an ultra-high vacuum container, a flange is provided on the inside of the metal gas foot contact part of the flat plate lid body. 1. A flat plate lid for a Kokutaka Nitrogen container, characterized in that the section modulus of the groove is smaller than the section modulus of the bolt fastening section. (2) Make the bolt tightening part thicker than the inside, and attach a rib to the thinner part on the inside, and what about the rib? A flat plate lid for an ultra-high vacuum container according to claim (1), which is attached with an appropriate distance from the bolt fastening portion.