JPS63119208A - Cryostat - Google Patents

Abstract

PURPOSE:To reduce the consumption of a refrigerant by mounting a shielding cover clogging a hole in a partition plate and a valve mechanism in which a closing cover for a hole separately formed to the cover or the partition plate is used as a valve, the valve is displaced by pressure difference received by one surface when the refrigerant is evaporated abnormally and a closed hole in the valve is opened. CONSTITUTION:A support bar 16 is hung to a cap 14 by employing a cord or a thread 15, and a shielding cover 17 inserted into a hole 11a in a partition plate with the minimum clearance required for insertion and retraction is set up at the lower end of the support bar penetrated into a hole 8a in a baffle plate. Since at least the hole 11a in the partition plate is closed on normalcy, an evaporation gas has to escape to an outlet through a circulating pipe, thus increasing the quantity of the gas circulated in the pipe. Thin finny second shielding covers 18 approximately clogging the holes 11a in each baffle plate without clearances are fitted on its midway of the support bar in conformity with the pitches of arrangement. A valve member 19 is blown up by the difference of pressure working on both surfaces of the shielding covers 17, 18 and the holes 8a, 11a are opened only when a refrigerant C in an inner vessel 1 is evaporated abnormally and the internal pressure of. the vessel suddenly rises. Accordingly, the greater part of the evaporation gas flows through the circulating pipe 6 on normalcy while passing through a short circuit path formed through the opening of the holes 8a, 11a and slipping off to an outlet on abnormality.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a cryostat that is provided with a heat shield plate that includes a circulation pipe for evaporative refrigerant gas within a vacuum insulation layer between an inner and an outer container, and in particular, an inner container. This invention relates to a cryostat that automatically switches between a normal flow path for evaporated gas and a flow path when an abnormality occurs, in order to ensure that the evaporated gas generated within the cryostat flows through the circulation pipe without shortage.

[Conventional technology]

Medical NMR (=MHI) that uses superconducting magnets
-CT (Nuclear magnetic resonance computed tomography imaging device)
As shown in FIG. 5, a horizontal cryostat installed in a room-temperature bore is generally used as a magnet storage container.

This cryostat has a heat-insulating structure in order to minimize the amount of evaporation of the refrigerant C (generally liquid helium) that cools the magnet B from the viewpoint of maintenance and operating costs. That is, the inner container 1 is placed inside the vacuum insulation layer 3 created between the hollow annular inner container 1 that stores the magnet B and the refrigerant C, and the outer container 2 that concentrically surrounds it.
A heat shield plate 4 for shielding radiant heat is provided on the outer periphery of the housing.

In addition, a circulation vibro that allows the evaporated gas of the refrigerant to enter and exit from the cylindrical port 5 of the inner container 1 is attached to this heat shield plate by wrapping and soldering, etc., so that the evaporative gas flowing inside this circulation pipe is attached. This is to forcibly cool the heat shield plate 4 to improve the heat insulation performance.

In addition, in an actual cryostat, in order to eliminate the intrusion of external heat transmitted through the circulation pipe, as shown in Figure 5, the gas coming out from the outlet of the circulation vibro is returned to port 5, and then is discharged from the lower outlet at the tip of the port. A baffle plate 8 for heat shielding is supported by a mounting rod 10 suspended from a top flange 9 at the entrance of the port 5 in order to allow the heat to go outside and to suppress the intrusion of radiant heat from the tip side of the port 5. is inserted.

In addition, if a method is adopted in which the gas after circulation is once returned to the port 5, it becomes difficult for evaporated gas to flow into the vibro, so a partition plate 1) is installed in the port 5 between the inlet and the outlet at the outlet of the vibro, above the inlet. It's profitable. Reference numeral 12 denotes a safety valve that opens when an abnormality occurs or a fuse cap that ruptures when an abnormality occurs.

[Problem that the invention seeks to solve]

The baffle plate 8 and the partition plate 1) have small holes 8a at corresponding positions for the purpose of passing a current lead wire to the magnet in the inner container and for the purpose of eliminating abnormal internal pressure increase in the inner container.
1) Since a is provided, it is not possible to prevent evaporated gas from passing through these holes and escaping directly to the outlet lower after the lead wire is pulled out, and as a result, the gas pressure on the inlet side of the circulation pipe is reduced. There is a problem in that the amount of gas flowing into the pipe is insufficient, making it difficult to cool the heat shield plate to the desired temperature, and even if cooling is possible, it takes time and the amount of refrigerant consumed during that time increases. Ta.

[Means for solving problems]

In order to eliminate the above-mentioned problems, the present invention provides a cryostat equipped with the above-described heat shield plate, partition plate, and baffle plate. A valve mechanism was installed in which the closing cover of a hole separately provided in the plate acts as a valve body, and the valve body is displaced by the pressure difference across one side during abnormal evaporation of the refrigerant, opening the hole that the valve body had closed. .

[Effect]

The above-mentioned valve mechanism closes at least the hole in the partition plate under normal conditions, so that the evaporated gas has no choice but to pass through the circulation pipe to the outlet, thereby increasing the amount of circulating gas in the pipe.

In addition, when an abnormality occurs in the refrigerant (when the magnet quenches), the valve body is displaced by the pressure difference and opens the hole. The inner chamber and the gas outlet provided at the port are short-circuited, and the evaporated gas passes through the short-circuit path to the outlet, thereby eliminating abnormal internal pressure increase in the inner container.

〔Example〕

A preferred embodiment of the invention is shown in FIGS. 1-3.

As shown in FIG. 1, the top flange 9 of the port 5 is provided with openings corresponding to the holes 8a, 1)a of the baffle plate 8 and the partition plate 1) (the figure shows one of them). ), this opening is closed by a camp 14 which is sealed by a Wilson seal 13. In the illustrated cryostat, a support rod 16 is suspended from the cap 14 using a string or thread 15, and the lower end of the support rod is inserted into and removed from the hole 1)a of the partition plate, which is passed through the hole 8a of the baffle plate. The shielding lid 17 is inserted with the minimum necessary clearance and is attached by screwing or gluing. Further, in the middle of the support rod, a thin fin-shaped second shielding lid 18 is inserted into the hole 1)a of each baffle plate to close the hole 1)a almost without a gap.
Attach the baffle plates in the same manner as above, and set the length l of the string or thread 14 to 1, and set the lid 17.
supports the support rod 16 in the position inserted into the holes 1)a and 8a, and allows the support rod to rise until the cover 17 is fully removed from the hole 1)a, but the lower baffle plate The value is set such that the lid 18 that closes the hole will not be allowed to rise to the position where it closes the hole in the upper baffle plate.

In addition, each of the support rod 16 and the shielding lid 17.18 is
From the viewpoint of reducing the weight of the valve member 19 made of aluminum and preventing heat from entering through the valve member 19, it is preferable to use an organic material with low thermal conductivity such as glass fiber-reinforced plastic, Teflon, or carbon fiber-reinforced plastic. However, the total weight of the valve member is determined so that the valve member cannot be pushed upward by the pressure difference of the evaporated gas under normal conditions. This weight adjustment may be performed by changing the volume of the lid 17. Since it is desirable that the lid 18 be thinner in terms of heat penetration, it is not preferable to adjust the weight by changing the thickness.

As shown in FIGS. 2 and 3, the exemplary cryostat is completed when the valve member 19 is provided in all of the partition plate 1) and the baffle plate 8 with corresponding holes.

By doing so, only when the refrigerant C in the inner container 1 abnormally evaporates and the internal pressure of the container rises rapidly, the valve member 19 acts on the pressure difference acting on both sides of the shielding lid 17.18. As shown by the chain line in FIG.
) Release a. Therefore, as mentioned in the function section, under normal conditions, most of the evaporated gas flows into the circulating vibro.
On the other hand, in the event of an abnormality, the hole 8a, 1)a opens and the air passes through the created short circuit path to the exit. Here, as shown in FIG. 3, there is a gap between the baffle plate 8 and the inner surface of the port 5 of, for example, 0.1 to 0.0 mm, which is necessary for inserting and removing the baffle plate.
Since there is a minute clearance g of about 2fl, the gas that comes out from the vibro outlet during normal operation (the amount is about 0.2n/hour in the case of a normal horizontal cryostat) will be exhausted from the clearance g even if the hole 8a is closed. can do.

Note that the valve member 19 may have the following structure, although this is not very preferable in terms of preventing intrusion of external heat. That is, the support rod 16 is fixed to the cap 14 and suspended, and the lid 17. is attached to the rod 16 as shown in FIG.
18 is preferably urged downward by a spring 20 and is slidably attached, so that only the lid can be pushed up in the event of an abnormality.

Further, since the object of the present invention is achieved by opening and closing the hole 1) a of the partition plate, the second shielding lid 18 is not essential. It is preferable that it works effectively to prevent heat intrusion from the inside. That is, the presence of the lid 18 makes it difficult for evaporated gas to escape from the holes in the baffle plate during normal operation, and since the baffle plate is sufficiently cooled before being removed, the amount of external heat entering is reduced.

Furthermore, when only the hole in the partition plate is closed, the shielding lid 17 is inserted into the hole 1)a so that it is held in the hole 1) even in the event of an abnormality, and the short circuit is made by drilling another hole in the partition plate 1) and using that hole. The closing lid may be formed by a valve mechanism using a valve body, and since the valve mechanism in this case is provided at a position away from the hole 1) a, it can be fixed to the partition plate.

〔effect〕

As described above, in the normal state when evaporative gas is naturally generated, at least the holes in the partition plate are closed and most of the generated gas is forced to flow through the circulation pipe, so the heat shield plate is cooled. This increases effectiveness and improves radiant heat shielding performance.

In addition, in the event of an abnormality, a valve mechanism in which the lid that closes the hole in the partition plate acts as a valve body shorts the inside of the inner container and the gas outlet of the port, so a dedicated safety gas is used that causes the port to become larger in diameter. It is possible to prevent an abnormal increase in the internal pressure of the inner container without providing a drainage passage.

Furthermore, if the holes in the baffle plate are also closed with the opening/closing lid, the cooling effect of the baffle plate is improved, so that the intrusion of radiant heat from the port entrance can be further reduced.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing a part of the main part of the Talaiostasoto according to the embodiment, FIG. 2 is a cross-sectional view showing the entire port part, and FIG.
The figure is a sectional view taken along line m-m in FIG. 2, FIG. 4 is a front view showing a part of another embodiment of the valve member, and FIG. 5 is a sectional view showing a well-known horizontal taliostat. FIG. 6 is a detailed sectional view of a port portion of a conventional taliostat. 1...Inner container, 2...Outer container, 3...
...Vacuum insulation layer, 4...Heat shield plate, 5
・・・・・・Cylindrical port, 6・・・・・・Circulation pipe,
7...Gas outlet, 8...Baffle plate,
8a...hole, 9...top flange,
10...Mounting rod, 1)...Partition plate, 1
)a...hole, 12...safety valve or fuse cap, 13...Wilson seal part,
14... Cap, 15... String or thread, 16... Support rod, 17.18... Shielding lid, 19... Valve Part, 20...Spring.

Claims (3)

[Claims] (1) In the vacuum insulation layer between the inner and outer containers, there is a heat shield plate wrapped with a pipe that circulates the evaporated gas of the refrigerant in the inner container, and in addition, there is an opening in the port of the inner container. a partition plate that partitions the inside of the port between the inlet of the circulation pipe and the outlet located above the inlet, and a baffle plate that is inserted into the port inlet and has a slightly smaller diameter than the port inner diameter. In a cryostat in which the partition plate and the baffle plate have holes in corresponding positions, at least a shielding cover that can be inserted and removed from the outside of the port that closes the hole in the partition plate, and a hole separately provided in the cover or the partition plate is closed. A cryostat characterized in that the lid serves as a valve body, and the valve body is displaced by a pressure difference between one side and the other side when abnormal evaporation of refrigerant occurs, thereby opening a closed hole in the valve body. (2) The above-mentioned valve mechanism includes a support rod that is suspended from a closing cap of a hole formed in the top flange of the port and passed through a hole in a baffle plate, and the above-mentioned shield that is attached to the lower end and inserted into and removed from a hole in a partition plate. Claim 1, characterized in that the shielding lid is configured to move up and down together with the support rod to open and close its own closed hole.
Cryostat described in ). (3) The support rod has a thin plate whose outer diameter is slightly smaller than the hole diameter of the baffle plate inserted into the hole of the baffle plate. Cryostat.