JP2003121292A - Leak detection method of vacuum vessel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect leak of a vacuum vessel having wall surface parts formed by welding a plurality of side face members from both inner and outer surface sides. SOLUTION: The vacuum vessel 1 comprises an upper lid part 2, a bottom plate part 3 and side wall parts 4. The side wall parts 4 are formed by inlay- coupling respective welding joint parts 6A-9B formed on a front side plate 6, a rear side plate 7 and two flat side surface side plates 8 and 9. Longitudinally offset outer surface side welded part 10A and inner side welded part 10B are formed by welding them on surfaces 30B and 30C in the thickness direction in the inlay-coupling parts, and a clearance space S is formed in a longitudinal part 30A between them to make a leak check hole 31A communicate to outside so that helium gas can be fed and sucked.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a leak detecting method for a vacuum container used for manufacturing electronic parts such as liquid crystal displays and semiconductors.

[0002]

2. Description of the Related Art Vacuum containers are used in the manufacture of liquid crystal displays, semiconductors and the like. Recently, there is an increasing demand for larger liquid crystal displays and the like, and it is becoming more and more necessary to increase the vertical and horizontal dimensions of the vacuum container (the height is almost the same). In the case of manufacturing such a large-sized vacuum container, in the method of manufacturing by shaving a portion corresponding to the inside of the vacuum chamber from an integral aluminum or aluminum alloy, the larger the vacuum container, the more waste of material occurs. Further, since the number of processing steps is also increased, it has been attempted to weld a plurality of side surface members to form a square tubular side wall portion and attach a bottom plate portion or an upper lid portion to the side wall portion. Examples of these are, for example, those shown in FIG. 1 of Japanese Patent Application Laid-Open No. 8-64542 and FIGS. 1 to 5 of Japanese Patent Application Laid-Open No. 5-123356, in which four or two side surfaces are provided on the side wall portion. The member is used.

[0003]

On the other hand, in addition to the above-mentioned increase in size, the number of cases in which a vacuum container is used under ultra-high vacuum is increasing. In this case, if the side wall portion is slightly deformed due to the difference in internal and external atmospheric pressure, leakage occurs. Occurs. Therefore, in order to prevent this leak, and to carry out surface processing after welding and surface regeneration processing after long-term use, a considerably thick aluminum-based plate material is used. This thickness needs to be increased to secure strength as the vacuum container becomes larger and the degree of vacuum becomes higher.

Then, when using an aluminum-based material having a tendency for welding deformation to be larger than that of such a steel material and for welding a thick side member, the side wall portion is suppressed in order to suppress the strength decrease and welding deformation due to welding heat as much as possible. It is desirable that the welded joint portion of the side member that constitutes the above be groove-processed from both the outer surface side and the inner surface side and be welded from each surface side (for example, Sangyo Shuppan Co., Ltd.).
(Page 116 of "Welding Complete Book 13 Welding of Aluminum and its Alloys" by Masao Mizuno, Kazuyuki Kirita, and Akira Sakaguchi, published on February 25, 1999).

However, when welding is performed from both sides in this way, a void (defective penetration) may occur in a part between these welded portions. In this case, if the inner surface side welded portion is defective, residual gas molecules in the cavity are released from the cavity into the vacuum chamber through the inner surface side welded portion, and the work piece inside is damaged. In order to avoid this, it is necessary to inspect for leaks from the inner surface side welded portion and the like.

Although there are various leak test methods, the sniffer method is often used because it is the cheapest and does not require large-scale equipment.
In this sniffer method, helium gas as a tracer gas is sealed in advance in the vacuum container, and the helium gas leaked by the suction pipe (sniffer probe) is sucked in from the outside of the vacuum container to cause a helium gas leak.・ The detector detects this. However, the sniffer method can
Even if the test is carried out, if there is no defect in the welded portion on the outer surface side and the leak is firmly blocked at this portion, there is a problem that the above defect cannot be found.

In this case, a leak test method other than the above-mentioned sniffer method, for example, a hood method or an envelope method is used to put a vacuum container in a closed chamber (hood) and supply helium gas to the outside of the vacuum container. Then, the inside of the vacuum vessel is evacuated to suck the gas in the vacuum vessel and helium gas
Even if an attempt is made to detect with a leak detector, if there is no defect in the welded portion on the outer surface side, even if there is a defect in the welded portion on the inner surface side, the defect cannot be detected.

[0008]

It is an object of the present invention to form side wall parts by welding side members which are made relatively thick for use in a large-sized vacuum container or the like, from the outer surface side and the inner surface side, respectively. Another object of the present invention is to provide a leak detection method for a vacuum container that enables a leak test even in a vacuum container.

[0009]

According to a first aspect of the present invention, there is provided a leak detecting method for a vacuum container, comprising: an upper lid portion, a bottom plate portion, an upper opening formed by an upper lid portion, and a lower opening formed by a bottom plate portion. Leakage of a vacuum container that is covered and has side walls formed in a rectangular tube shape by fixing at least two side surface members at respective weld joints by respective welded portions from the outer surface side and the inner surface side. A detection method, which is between the outer-side welded portion and the inner-side welded portion in the welding depth direction, and which covers the welded joint upper surface side end and the welded joint lower surface side end. A gap space is formed between the welded parts that cover the space, and a leak check hole that allows this gap space to communicate with the outside of the vacuum chamber is formed on the side wall, and also inside the vacuum container or on one side of the leak check hole. Tracer Moth Is supplied, and vacuum is drawn from the inside of the vacuum container or from the other side of the leak check hole to inspect for the presence of tracer gas. Characterize.

According to a second aspect of the present invention, there is provided a method for detecting a leak in a vacuum container, wherein, in the welded portion, preferably,
The tracer gas is blocked from entering and exiting by covering the welded part except the welded part that is checked for leaks with sealing tape.

According to a third aspect of the present invention, there is provided a leak detecting method for a vacuum container, wherein the outer surface side welded portion and the inner surface side welded portion are preferably offset from each other along the longitudinal direction of the welded joint. At the same time, the gap space is formed between the offset positions.

According to a fourth aspect of the leak detecting method for a vacuum container of the present invention, preferably, the offset welded portion is formed in a shape capable of spigot connection, in a thickness direction of the welded joint portion. Are provided on the surface on the outer surface side along with the surface on the inner surface side along the thickness direction of the welded joint,
In addition, the gap space is provided at a portion where the welding joint portions for spigot connection face each other along the surface in the longitudinal direction.

According to a fifth aspect of the present invention, there is provided a leak detecting method for a vacuum container, wherein a welding joint portion for spigot connection is preferably formed into a flat plate shape and a protruding portion obtained by bending both ends of a substantially U-shaped side member. It is provided at both ends of the side member, and the welded joint portion of the protruding portion is formed such that the inner surface side portion is longer than the outer surface side portion.

[0014]

According to the leak detecting method for a vacuum container according to the present invention as set forth in claim 1, the vacuum container is manufactured by welding each of the inner and outer surfaces in order to reduce welding deformation and the like (particularly the side wall portion thereof). In addition, a gap space is positively secured between the double-sided welded portion and the welded portions of the upper surface side end portion and the lower surface side end portion, and a leak check hole communicating with the outside is communicated with the gap space. Therefore, the gap space formed between the inner surface side welded portion and the outer surface side welded portion, and the space portion located above or below the leak check hole also passes through the leak check hole. It is possible to communicate with the outside.

Therefore, in either the sniffer method or the hood method, the tracer gas is supplied to the inside of the vacuum container or one side of the leak check hole, and the inside of the vacuum container or the other side of the leak check hole is supplied. From the tracer gas detector by pulling a vacuum from
Even when there is a defect in the inner surface side welded portion, the tracer gas can be led out to the entire surface of the inner surface side welded portion in the gap space side or the entire surface of the inner surface side welded portion in the gap space side through the above-mentioned gap space. . As a result, the tracer gas flowing in and out through the defective portion of the inner surface side welded portion can be detected by the tracer gas detector, and it becomes possible to inspect whether or not there is a leak from the inner surface side welded portion. Also,
Similarly, it is possible to inspect whether or not there is a leak in the welded portion on the outer surface side.

In the leak detecting method for a vacuum container according to the present invention as defined in claim 2, a tracer is formed by attaching a seal tape to the welded portion except the welded portion where the leak is to be detected.
Since it prevents gas from entering and exiting, it is possible to easily detect the presence or absence of leaks at the welded part of the person who wants to inspect for leaks without sticking the seal tape, using only a simple work such as sticking the seal tape, or a tool. be able to.

In the vacuum container leak detection method according to the present invention as defined in claim 3, the outer surface side welded portion and the inner surface side welded portion are provided at positions offset along the longitudinal direction of the welded joint portion. At the same time, since the above-mentioned gap space is formed between the offset positions, the welded portions from both sides are more blunt than in the case where the outer surface side welded portion and the inner surface side welded portion are not provided in positions where they are longitudinally offset. It is possible to easily prevent a part of the gap space from being cut off from the leak check hole by integrally using it to divide the gap space in the middle, and a reliable leak test can be performed.

According to a fourth aspect of the leak detecting method for a vacuum container of the present invention, an outer surface along a thickness direction of a welded joint portion in which an offset welded portion has a shape capable of spigot connection. And the inner surface side surface along the thickness direction of the welded joint, respectively, and the welded joint portions for interlocking the gap space are provided at portions facing each other along the longitudinal surface. Therefore, similar to the above, it is possible to easily prevent a part of the space from being blocked from the leak check hole, and at the time of welding the welded joint, the spigot joint portion positions and deforms the welded joint. It becomes possible to suppress the formation of the side wall portion.

In a leak detecting method for a vacuum container according to a fifth aspect of the present invention, a welding joint portion for spigot connection is formed into a flat plate shape with a protruding portion obtained by bending both ends of a substantially U-shaped side member. Since it is provided at both ends of the side member and the inner surface side portion of the protruding portion is formed to be longer than the outer surface side portion,
Similarly to the above, it is possible to easily prevent a part of the space from being blocked from the leak check hole, and in addition to enabling positioning of the weld joint during welding with the spigot joint, With the welded portion, it is possible to maintain a strong strength against the pressing force to the inner side of the vacuum container due to the pressure difference between the inside and outside.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. A vacuum container capable of performing a leak test according to this embodiment will be described with reference to FIG. In the figure, the vacuum container 1 is composed of an upper lid portion 2, a bottom plate portion 3, and a square tubular side wall portion 4 arranged therebetween. These upper lids 2,
The bottom plate portion 3 and the side wall portion 4 are, for example, JIS symbol A5.
It is formed from a plate material made of aluminum alloy 052.
The bottom plate portion 3 has, for example, a TIG (TI
G: Tungsteninert-gas) welding method (or GTAW: gas tunstenarc w)
It is fixed at a welded portion (welding bead) 5 that is integrally welded by means of welding.

On the other hand, the upper lid portion 2 is fixed by screwing bolts into a plurality of bolt holes (not shown) provided in the upper surface portion of the side wall portion 4. In this case, a seal groove (not shown) is provided on the upper surface of the side wall portion 4, and the upper lid portion 2 is fixed with a bolt to seal the vacuum chamber with the seal inserted therein.

The side wall portion 4 has four side surface members, that is,
The front side plate 6, the rear side plate 7, and the two side surface plates 8 and 9 are welded by, for example, a TIG welding method as described later to form a rectangular tube shape. As the front side plate 6 and the rear side plate 7, the shorter one of the vertical and horizontal lengths of the vacuum container 1 as the final product is selected, but the names such as the front face, the rear face, and the side faces are used for convenience in this embodiment. However, it is different whether or not the actual vacuum container is arranged according to its name.

The front side plate 6 and the rear side plate 7 are substantially U-shaped,
That is, both ends are formed so as to project in a direction forming a right angle from the central portion, and a welded joint portion is formed at the tip of the projecting portion. On the other hand, the side surface side plates 8 and 9 are flat plate-shaped, and welded joint portions are formed at both ends thereof. The side surface plates 8 and 9 and the front surface plate 6 and the rear surface plate 7 are welded portions (welding beads) 10A and 11A in which welded joint portions of respective end portions are fitted to each other as described below and welded from the outer surface side.
A, 12A, 13A (however, 12A and 13A are hidden behind the side plate 9 in the figure) and welded parts (welded beads) 10B, 11B, 12B, 1 welded from the inner surface side.
3B (however, 10B and 11B are hidden behind the side plate 8 in the figure).

The upper surface and the lower surface of the welded joint portion of the side wall portion 4 are welded portions (welded beads) 14A to 17A,
And 14B to 17B (the lower welding portion 16 in FIG. 1).
B and 17B are hidden behind the side plate 8 on the front side. )
It is stuck in. The side plate 8 has two openings 1
The openings 8 and 19 are formed in the front side plate 6, and the openings 20 are formed in the front side plate 6 so as to be used for loading and unloading the workpiece, for viewing windows, and the like. Further, the front side plate 6 and the rear side plate 7 have leak check holes 31A to 31D described later (however, 31C and 31D in FIG. 2 are hidden behind the rear side plate 7).
Is provided.

Next, the construction and manufacturing method of the side wall portion 4 of the vacuum container 1 will be described in more detail below. FIG. 2 is a diagram for explaining the relationship of each welded joint before groove processing, and FIG. 3 is a diagram showing the side wall portion 4 in a state of temporary assembly before welding. In order to obtain the front face portion 6 and the back face portion 7, first, the aluminum alloy plate material is scored and then cut into a predetermined size. At this time, the height of the wall member is set to be "the height of the wall surface of the vacuum container as the final product plus alpha (processing allowance)".

The front side plate 6 and the rear side plate 7 are machined into inner surfaces when they are assembled into a vacuum vessel, leaving both end portions, and partially scraping between the both end portions to form a substantially U-shape. Therefore, the both ends have a shape projecting toward the side wall plates 8 and 9, and the welded joints 6A, 6B, 7A and 7B are formed at the tips. These welded joint portions 6A, 6B, 7A, 7B are so-called spigot-connectable with welded joint portions 8A, 8B, 9A, 9B provided at both ends of the side wall plates 8, 9. That is, each of the welded joint portions 6A to 9A and 6B to 9B has a stepped shape when viewed from the upper surface, but in this case, the welded joint portions 6A, 6B, 7A and 7B of the front side plate 6 and the rear side plate 7 are formed. Side wall plates 8 and 9
The protruding length toward the inner surface side portion is longer than the outer surface side portion. Therefore, the side plate 8,
In Fig. 9, the welded joint portions 8A, 8B, 9A, 9B are formed such that the inner surface side portion thereof is shorter than the outer surface side portion thereof.

As shown in FIG. 3), the front side plate 6,
Welded joint portions 6A to 9 of the rear side plate 7 and the side surface plates 8 and 9
Grooves for welding (upper surface side grooves 21A to 24A, lower surface side grooves 21B to 24A) are formed by U-shaped groove processing with a planer, a shaper, etc. in the upper and lower end portions of the abutting portion of B and the perpendicular direction connecting them.
B, outer surface side normal direction grooves 25A to 28A, and inner surface side perpendicular direction grooves 25B to 28B) are provided and each plate is cleaned. Note that FIG. 4 shows a part of the front side plate 6 on the joint portion 6B side in an enlarged manner.

Then, as shown in FIG. 3, the front side plate 6
Is the weld joint portion 6A of the side plate 8
Further, the welded joint portion 6B is butted to the welded joint portion 9A of the side surface side plate 9 and is spigot-joined. Similarly, the rear side plate 7 has its welded joint portion 7A butted against the welded joint portion 8B of the side surface side plate 8 and its welded joint portion 7B against the welded joint portion 9B of the side surface side plate 9 for spigot connection.

After the above-mentioned temporary assembly, by TIG welding, the upper surface side grooves 21A to 24A and the lower surface side groove 21B to
24B, the outer surface side normal direction grooves 25A to 28A, and the inner surface side normal direction grooves 25B to 28B, and the outer surface side normal direction welding beads 10A as shown in FIG.
~ 13A, inner surface side normal welding beads 10B ~ 13B,
Upper surface side welding beads 14A to 17A, lower surface side welding beads 1
4B to 17B are provided. Note that some of these weld beads are hidden and do not appear on the back surface in FIG. 1.

In the above welding, the welded joint portions 6A-9
A, 6B to 9B, except for the upper and lower surface side end portions, as shown in FIG. 4 and FIG. 5, which are partially shown in cross section, the front end portions of the outer surface side welding bead 10A and the inner surface side welding bead 10B in the welding depth direction. (The deepest part of the welding) is positioned on the front side in the thickness direction than the surface passing through the portion 30A facing along the longitudinal surface of the side surface side plate 8 in the contact surface 30 of the spigot joint portion. , The tips of the weld beads are separated from each other by a predetermined distance in the thickness direction.

Therefore, in this case, of the contact surfaces of the spigot joint portion, the facing portion 30A along the longitudinal direction surface.
And, in the facing portions 30B and 30C of the non-welded portion along the thickness direction surface orthogonal to this, the welding bead does not enter, and these portions and the welded portions at the upper surface side end portion and the lower surface side end portion (in FIG. 1). 16A, 16B) to form a gap space S between them. However, the gap space S is not so large even if it is a space, and it is sufficient if gas molecules can move, and therefore, it may be a minute gap that is naturally formed when the surfaces of the spigot joints are brought into contact with each other. The welding depth from the inner surface side and the welding depth from the outer surface side are substantially the same here.

On the other hand, at the side end portions of the front side plate 6 and the rear side plate 7, as shown in FIG. 32A (32B is not shown) are provided along the hole. This hole 32A extends the tip on the weld joint 6A side along the portion 30A facing in the longitudinal direction to the tip end position on the inner surface side of the spigot joint (the contact surface position in the upper thickness direction in the drawing), and the weld joint is formed. The tip on the side of the portion 8A extends to the tip position on the outer surface side of the spigot joint portion (the contact surface position in the thickness direction in the lower part of the drawing), and the threaded portion 33A is formed on the other tip to enable communication with the outside. . This hole 32A and screw part 3
3A constitutes a leak check hole 31A for evacuation.

As described above, the leak check holes 31B to 31D (31C and 31D are also shown in FIGS. 1 and 2) of the rear side plate 7 in the other three places, which have the same structure as the leak check hole 31A. I can't see it hidden behind.) Further, a pipe-side screw portion for vacuuming (not shown) can be screwed into the screw portions 33A to 33D so that a leak check can be performed. After checking the leak, seal it with a sealing screw (not shown).

The side wall portion 4 integrated by welding as described above
Is made flat by machining the upper and lower welded parts, and after welding the bottom plate portion 3 from the lower surface as shown in FIG. 1,
Secondary processing is performed, and the upper lid portion 2 is fixed to the upper surface with bolts.

In the vacuum container 1 configured as described above, as one method for inspecting the presence or absence of a leak from the inner surface side welded portion 10B, for example, the inspection is carried out with the upper lid portion 2 attached to the side wall portion 4. . In this state, the vacuum container 1 is set in the leak test device shown in FIG. This leak test equipment uses helium gas as the tracer gas. Here, helium is used for the tracer gas as follows. 1. The residual gas in the vacuum container and the amount contained in the air are small. 2. It is an inert gas and does not contaminate the vacuum container, etc. 3. The molecular weight is small and it is easy to enter from the leak point. Harmless to human body, 5. It is based on the reason that there is no fear of explosion.

In FIG. 6, inside the vacuum vessel 1, a passage 41 and a gas on-off valve 36 provided in the passage 41 are provided.
The helium gas supply / recovery device 35 is connected via the. On the other hand, one end of the passage 42 is connected in the middle of the passage 41. The passage 42 has a vacuum opening / closing valve 3 in the middle thereof.
8 is provided and the other end is connected to the vacuum pump 37.

A tracer probe 39 is attached to the leak check hole 31A of the vacuum container 1. The tracer probe 39 is connected to a helium gas detector (tracer gas detector) 40. This helium gas detector 39 can be used, for example, on pages 91 to 92 (especially from the Japan Vacuum Industry Association, “Introduction to Learning Vacuum Technology: From Basics to Applications” (published on July 1, 1999 by the Industrial Research Board) (particularly (Fig. 7.2)
Use the one described in.

First, the vacuum opening / closing valve 38 is opened to evacuate the inside of the vacuum container 1. After that, the vacuum opening / closing valve 38 is closed, the gas opening / closing valve 36 is opened, and helium gas is supplied from the helium gas supply / recovery device 35 into the vacuum container 1 to fill the inside thereof. In this state, the tracer probe 39 attached to the leak check hole 31A sucks the inside of the minute space S, and the helium gas detector 40 inspects whether or not there is helium gas during the suction.

Here, if helium gas is detected,
It can be seen that the inner surface side welded portion 10B has a defect. In this case, since the minute space S passes through, the inner surface side welded portion 1
The leak inspection can be performed even on the entire surface of 0B, that is, the portion above and below the leak check hole 31A. When the leak inspection is finished, the suction from the tracer probe is terminated, the helium gas supply / recovery device 35 is operated to suck back the helium gas in the vacuum container 1, and when the entire amount is recovered, the operation is stopped. The gas open / close valve 36 is closed. The above-mentioned leak inspection of the inner surface side welded portion is sequentially carried out for each inner surface side welded portion.

In this leak test, unlike the above method, it is possible to carry out the leak test without attaching the upper lid portion 2 to the side wall portion 4. In this case,
Inner surface side welded portion 1 to be subjected to leak inspection as shown in (a cross section at a position vertically displaced from FIG. 5) is desired.
0B, that is, the outer surface side welded portion 10A and the upper surface side end portion and the lower surface side end portion welded portion 1 shown in FIG.
4A and 14B have sealing tape 3
Attach 4 to prevent gas molecules from entering and exiting.

In this state, helium gas is blown from the inside to the inner surface side welded portion 10B. Then, in the same manner as above, the tracer attached to the leak check hole 31A
The inside of the minute space S is sucked from the probe 39, and the helium gas detector 40 inspects whether helium gas is present during the suction. Even in this case, if there is a defect that leaks in the inner surface side welded portion 10B, it can be detected.

In another method, helium gas is supplied from the leak check hole 31A, and the inner surface side welded portion 1 is supplied.
It is also possible to perform a leak check by disposing the tracer probe 39 inside 0B and moving it along the inner surface side welded portion 10B. In this case, when the leak test is performed by placing the vacuum container 1 in the hood filled with helium gas, the leak test is performed with the upper lid part 2 attached to the side wall part 4, except for the inner surface side welded part to be leak-checked. A seal tape is attached to the welded part on the inner surface side. Also,
It goes without saying that in each of the above leak test methods, the presence or absence of leak from the outer surface side welded portion can be further investigated.

As can be seen from the above, in the leak detecting method for a vacuum container of this embodiment, a plurality of side wall portions are provided for the purpose of increasing the size of the vacuum container, reducing the cost, and enabling it to be used even under ultrahigh vacuum. Even in a vacuum container in which these are welded from the inner and outer side surfaces by the side members of the above, not only the inner surface side welded portion through the gap space and the leak check hole provided between the inner surface side welded portion and the outer surface side welded portion, It becomes possible to inspect for leaks of helium gas from the welded portions on the outer surface side, the upper surface side end and the lower surface side end.

In this leak inspection method, various leak test methods can be used, and the leak test can be performed by the method as described above without attaching the upper lid portion to the side wall portion. Is also possible. In this case, inspection time and inspection cost can be reduced.

Further, the welded joint portion is formed into a spigot joint, and the outer surface side welded portion and the inner surface side welded portion are offset in the longitudinal direction on the surfaces along the respective thickness directions of the outer surface side and the inner surface side of the spigot jointed portion. Since this is provided, it is possible to avoid the problem that some of the welded portions from both the inner and outer surfaces are welded and the middle of the gap space is divided, and leak detection is partially impossible. .

By setting the inner surface side portion of the welded joint portion in the longitudinal direction by the spigot connection to be longer than the outer surface side portion thereof, the internal pressure due to the difference between the internal pressure and the external pressure generated during the vacuum state inside the vacuum container can be improved. It is possible to receive the pressing force to the welding part and the spigot part, and it is also possible to obtain the effect of increasing the strength. Further, even if the welded portion is broken due to poor welding, it is possible to avoid the problem that the side surface plates 8, 9 and the like enter the inside of the vacuum container and damage the internal portion by receiving it at the spigot portion. .

In the above embodiment, the outer surface side welded portion and the inner surface side welded portion are provided at positions offset along the longitudinal direction of the welded joint portion, but they do not necessarily have to be offset and are the same. You may make it provide on the surface of a thickness direction and form a clearance space between both welding parts. Also,
The outer surface-side welded portion and the inner surface-side welded portion have substantially the same welding depth (thickness direction length), but the welding depths may be slightly asymmetric. In this case, the inner portion of the protruding portion of the substantially U-shaped side member is made longer than the outer portion,
It is desirable to set the ratio as shown in FIG. 6.7 on page 116 of "Welding Guide 13 Welding of aluminum and its alloys". Needless to say, the welding is not limited to TIG welding, and other welding methods may be used.

[Brief description of drawings]

FIG. 1 is a diagram of a vacuum device with an upper lid removed.

FIG. 2 is a diagram showing a relationship of a welded joint portion of a side wall portion.

FIG. 3 is a view of a side wall portion of a vacuum container temporarily assembled before welding.

FIG. 4 is a view of an upper surface portion of a side wall portion in a state of temporary assembly before welding.

FIG. 5 is a cross-sectional view of a portion provided with a leak check hole.

FIG. 6 is a diagram showing a leak test apparatus.

FIG. 7 is a view showing a state in which a welding portion is covered with a seal tape.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Vacuum container 2 Upper lid part 3 Bottom plate part 4 Side wall part 6 Front side plate 7 Rear side plates 8, 9 Side side plates 6A-9A, 6B-9B Weld joint parts 10A-13A, 10B-13B Perpendicular welding beads 14A-17A Top end Weld beads 14B to 17B, weld beads 30A on the lower surface side end portions 31A to 31D facing the longitudinal direction, leak check holes 34 seal tape 35 helium gas supply / recovery device 39 tracer probe 40 helium gas, Leak detector S Gap space

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Satoshi Sonobe             2-11-7 Fukuura, Kanazawa-ku, Yokohama-shi, Kanagawa             In ceremony company Toyo Jig (72) Inventor Yoshio Kimura             Kanagawa Prefecture Sagamihara City Tana 5338-7 F term (reference) 2G067 AA24 AA44 BB04 BB07 BB12                       CC11 CC13 DD17 DD18

Claims (5)

[Claims] 1. An upper lid portion, a bottom plate portion, an upper opening is covered by the upper lid portion, and a lower opening is covered by the bottom plate portion, and at least two side surface members are respectively welded to the outer surface side. A leak detection method for a vacuum container having a side wall portion formed in a rectangular tube shape by being fixed by respective welded portions from the inner surface side, wherein each of the outer surface side welded portion and the inner surface side welded portion A gap space is formed between the front end portions in the welding depth direction and between the weld portion covering the upper surface side end portion of the weld joint portion and the weld portion covering the lower surface side end portion of the weld joint portion, A leak check hole capable of communicating a space to the outside of the vacuum chamber is formed in the side wall portion, and a tracer gas is supplied to the inside of the vacuum container or one side of the leak check hole to form the vacuum container. Inside Alternatively, the presence / absence of a leak from the inner surface side welded portion is checked by vacuuming from the other side of the leak check hole and inspecting for the presence / absence of the tracer gas. A leak detection method for a vacuum container. 2. The welded portion is configured such that the tracer gas is prevented from entering and exiting by covering the welded portion excluding the welded portion for checking the presence or absence of a leak with a sealing tape. The leak detection method described in 1. 3. The welded joint portion is provided with the outer surface side welded portion and the inner surface side welded portion at positions offset along the longitudinal direction of the welded joint portion, and the gap space is provided between the offset positions. The leak detection method for a vacuum container according to claim 1, wherein the leak detection method is for forming a vacuum container. 4. The offset welded portion is formed on an outer surface side of the welded joint portion having a shape capable of spigot connection and along a thickness direction of the welded joint portion and a thickness direction of the welded joint portion. The inner surface side surface along the inner surface is provided, and the clearance space is provided at a portion where the spigot-welded weld joint portions are opposed to each other along a longitudinal surface. A method for detecting leak in a vacuum container as described. 5. The welding joint portion for spigot connection is provided at a protruding portion bent from both ends of a substantially U-shaped side member and both end portions of a flat plate-shaped side wall member, and the welding joint portion of the protruding portion is The method for detecting leaks in a vacuum container according to claim 4, wherein the inner surface side portion is formed to be longer than the outer surface side portion.