JPH04185973A - Air-tight seal method in very low temperature tank - Google Patents

Abstract

PURPOSE:To perform an air-tight seal at a low cost and easily by setting roughness of an obverse of a flange part and a surface of a cover unit to a specific value, and applying silicon grease or an epoxy adhesive agent annularly to the total periphery in the peripheral direction so that a width in a radial direction of the flange part obtains specific dimension. CONSTITUTION:An obverse 2A of a flange part 2 of a tank main unit 1 and a lower surface 4A of a cover unit 4 are left as finished so that roughness of the surfaces obtains 6.3mum or less maximum roughness Rmax. Silicon grease or an epoxy adhesive agent 10 is left as applied annularly over the total circumference of the flange part 2 in a 5mm or more width on the obverse 2A of the flange part 2. Thereafter, the cover unit 4 is placed on the tank main unit 1 and tightened by bolts by bringing the lower surface 4A of the cover unit 4 into contact with the obverse 2A of the flange part 2. Sufficient air-tight seal performance can be thus obtained by using not a particular and expensive low temperature seal member but only the cheap silicon grease or epoxy adhesive agent, and a cost for an air-tight seal can be decreased to perform work very simply and easily.

Description

[Detailed Description of the Invention] Industrial Field of Use This invention is used for conducting experiments and measurements at extremely low temperatures on samples such as semiconductor materials and various elements, or for storing various substances at extremely low temperatures. The present invention relates to a method for airtightly sealing between the flange portion of the tank body and the lid in a cryogenic tank used for.

Conventional technology With the recent development of low-temperature science, there are increasing opportunities to conduct measurements and cryogenic experiments at extremely low temperatures below 150 to investigate the low-temperature properties and behavior of various materials and elements such as semiconductors. It is starting to increase.

In such a cryogenic test apparatus, it is necessary to cool and maintain the sample at a cryogenic temperature using low-temperature liquefied gas such as liquid nitrogen or liquid helium, and for this purpose, a cryogenic chamber called a cryostat is generally used.

By the way, in a cryogenic chamber such as a cryostat, in order to maintain internal vacuum and airtightness, it is generally necessary to airtightly seal between the flange portion around the open end of the chamber body and the lid (generally the upper lid). In this case, generally a groove 3 is formed on the upper surface of the flange 2 of the tank body 1 as shown in FIG. The sealing member 5 is pressed and deformed by a protrusion 8 on the lower surface of the body 4.

As a sealing member in the above-mentioned airtight seal at extremely low temperatures, ordinary rubber O-rings for room temperature cannot be used due to problems such as hardening.

Therefore, in general, a special low-temperature metal O-ring made of metal is used, or a special composite O-ring known by the product name "Helicotrex" etc. A special O-ring with a cutout and a metal spring stored inside is used, a special-shaped O-ring made of Teflon resin, and a metal wire that is soft even at extremely low temperatures, such as indium wire or gold wire. It is being used.

Problems to be Solved by the Invention As mentioned above, low-temperature metal O-rings and special O-rings used as sealing members in conventional cryogenic airtight seals.
The reality is that rings, indium wires, and gold wires are all extremely expensive, and the work required for sealing with these special sealing members is complicated.

The present invention was made against the background of the above circumstances, and it is an object of the present invention to provide a method that enables hermetic sealing in a cryogenic chamber to be performed more easily and at a much lower cost than in the past. be.

Means for Solving the Problems The method of the present invention provides an airtight seal between the flange of the tank body of a cryogenic tank and the lid that is in contact with it. The roughness of the surface is set to a maximum roughness Rmax of 6.3 um or less, and silicone grease or epoxy adhesive is applied to at least one of the surface of the flange portion and the surface of the lid body in the radial direction of the flange portion. After applying it in an annular manner over the entire circumference in the circumferential direction so that the width is 5 m+ or more, the surface of the lid body and the above-mentioned surface of the flange portion are brought into contact, and the lid body and the flange portion are fastened with bolts. This is a characteristic feature.

Function: In the method of the present invention, the surface of the 7-rung portion of the tank body and the surface of the lid body that is in contact with the surface of the 7-rung portion are both roughened to a maximum roughness (Ra5z) of 6.3 μs or less. Leave it on a smooth surface. Apply silicone grease or epoxy adhesive to such a smooth surface with a width of 51 m.
If the coating is applied as described above, both surfaces are brought into contact, and the flange portion and the lid are fastened together by bolts, sufficient airtightness can be maintained even at extremely low temperatures below 15 OK.

In the past, silicone grease has generally been used to supplement seals with rubber O-rings when sealing at room temperature, but it has not been used as a sealing member by itself, and it is also effective for sealing at extremely low temperatures. This was not thought to be possible, but it can be achieved by simply making the contact surface of the seal part smooth to a certain extent, interposing a thin film of silicone grease between the contact surfaces over a certain width, and applying the pressure equivalent to tightening a bolt. The present inventors have discovered for the first time that sufficient airtight sealing performance can be obtained even at low temperatures. The same is true for epoxy adhesives, and although the use of epoxy adhesives for airtight sealing at extremely low temperatures had never been considered in the past, the inventor of the present application discovered that they can achieve the same effect as silicone grease. This was discovered for the first time.

As is clear from the above, in actual airtight sealing work, all you have to do is apply silicone grease or epoxy resin and tighten the bolts.
The sealing operation is significantly simplified.

Here, if the roughness of the contact surface to be sealed exceeds the maximum roughness Rmax of 6.34, the thickness of the film of silicone grease or epoxy adhesive interposed between the surfaces even if pressure is applied during bolt tightening. becomes thicker, resulting in poor airtight sealing performance. Furthermore, if the width of the applied silicone grease or epoxy adhesive is less than 5III11, sufficient airtight sealing performance may not be obtained. Therefore, the surface roughness was set to Rmxx of 6.3 μs or less, and the application width was set to 5W or more.

Embodiment In carrying out the method of the present invention, for example, the two surfaces of the flange portion 2 of the tank body 1 shown in FIG. ! 6.
Finish it so that it is 31j1111 or less.

In addition, in FIG. 1, 11.12 are bolt holes. Reference numeral 13 denotes an insertion hole provided in the lid 4, and this insertion hole 13 is used to reduce the pressure inside the tank body 1 and to pass a signal line through it. 13 is also hermetically sealed.

Then, as shown in FIGS. 1 and 2, silicone grease or epoxy adhesive 10 is applied to the surface 2A of the flange portion 2 in a circular manner with a width W of 5 Wm or more over the entire circumference of the flange portion 2 with a finger, spatula, etc. It is applied using an appropriate application method. At this time, the width W of the silicone grease or epoxy adhesive 10 is set to be 5II11 or more.

Thereafter, as shown in FIG. 3, the lid 4 is placed on the tank body 1, the lower surface 4A of the lid 4 is brought into contact with the surface 2A of the flange portion 2, and the bolts 7 are tightened.

Note that when using an epoxy adhesive, it is necessary to tighten the lid 4 to the flange portion 2 with the bolts 7 before the epoxy adhesive loses its fluidity.

Furthermore, in the above example, silicone grease or epoxy adhesive was applied to the flange side, but it is of course possible to apply it to the lid side. You can also apply it.

Further, in the above example, the bolt is tightened using a nut, but in some cases, a female threaded hole may be formed in the flange portion, and the bolt may be tightened into the female threaded hole.

Effects of the Invention According to the method of the present invention, when sealing the lid and the flange of the tank body in a cryogenic tank, there is no need to use a special and expensive low-temperature sealing member, and inexpensive silicone grease or epoxy can be used. Sufficient airtight sealing can be achieved just by using a type of adhesive, which can significantly reduce the cost required for airtight sealing compared to conventional methods. It is sufficient to apply the agent and tighten the bolts, making the work extremely simple and easy.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view of an example of the flange portion and lid of the tank body with silicone grease or epoxy resin applied to the seven rung portions of the tank body when carrying out the method of the present invention, and FIG. Figure 1 is a perspective view of the flange part, Figure 3 is a vertical sectional view showing the flange part and lid body after airtight sealing by the method of the present invention, and Figure 4 is an airtight view of a conventional general cryogenic chamber. FIG. 3 is a longitudinal cross-sectional view showing a sealing method. 1... Tank body, 2... Flange portion, 4... Lid, 7... Bolt, 10... Silicone grease or epoxy adhesive.

Claims (1)

[Claims] When creating an airtight seal between the flange of the cryogenic chamber body and the lid in contact with it, the roughness of the surface of the flange and the surface of the lid that should be in contact with the flange surface is set to the maximum roughness Rmax of 6. .3 μm or less, and apply silicone grease or epoxy adhesive to at least one of the surface of the flange and the surface of the lid so that the width of the flange in the radial direction is 5 mm or more. 1. A method for airtight sealing in a cryogenic chamber, characterized in that after the coating is applied in an annular manner around the circumference, the surface of the lid body and the surface of the flange portion are brought into contact with each other, and the lid body and the flange portion are fastened with bolts.