JPH04366094A - Powder vacuum insulator - Google Patents

Abstract

PURPOSE:To reduce vacuum evacuation time by eliminating an impact of a filter for preventing powder diffusion with small evacuation conductance in vacuum evacuation of a powder vacuum insulator. CONSTITUTION:A powder vacuum insulating layer 15 is formed in a space 14 between an outer vessel 12 and an inner vessel 13 so that it keeps vacuum. An evacuation port 17 is provided to evacuate the space 14 to vacuum. A filter 18 for preventing powder diffusion is provided in the space 14 so that it blocks this evacuation port 17, and an opening means 19 is provided to open the filter 18 after the space 14 is evacuated to vacuum to some extent. In this way, at the time of vacuum evacuation from the initial atmospheric pressure to a viscous flow zone, the filter 18 prevents diffusion of powder by blocking the evacuation port 17. At the time of vacuum evacuation after an intermediate flow zone, the opening means 19 opens the filter 18 and a vacuum evacuation time is reduced.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to powder vacuum insulation,
In particular, the present invention relates to a powder vacuum heat insulating body in which a filter for preventing powder scattering is provided at an exhaust port for evacuating a powder vacuum heat insulating layer.

0002

[Prior Art] As a conventional powder vacuum insulation of this type,
A heat insulating container as shown in FIG. 9 has been proposed. This container is composed of a double-walled structure having an opening 11 on one side, and has an outer container 12 and an inner container 13 made of stainless steel, and a space between the outer container 12 and the inner container 13. 14 and an exhaust cap 16 attached to the wall of the outer container 12. When this heat insulating container is used, the opening 11 is closed with a heat insulating lid to form a sealed space. The powder vacuum heat insulating layer 15 is formed by filling the space 14 with a heat insulating powder 20 such as silica-based fine powder, evacuating the space 14, and then sealing the space 14 to maintain the vacuum.

The exhaust cap 16 is used to evacuate the space 14 and has an exhaust port 17. A filter 18 for preventing powder scattering is attached to the exhaust port 17, and the filter 18 is made of compacted ceramic fiber, metal, soft plastic foam, or the like. That is, since the powder 20 has a scattering property, it is easily scattered during evacuation, and the filter 18 is provided to prevent this scattering. If scattering is not prevented, the exhaust pump may suck in the powder 20 and malfunction, or the powder 20 adhering to the sealing part of the exhaust cap 16 when sealing the exhaust port 17 may cause a sealing failure. It is common to provide a filter 18 as shown in FIG.

0004

However, in the conventional powder vacuum insulated container described above, the filter 18 is directly attached to the exhaust port 17 having the diameter D1.
There is a problem in that the exhaust conductance of the space 14 becomes very small, and the time required to evacuate the space 14 becomes long.

SUMMARY OF THE INVENTION An object of the present invention is to solve these problems and increase the exhaust conductance of the filter, thereby shortening the time required for evacuation.

[0006]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a powder vacuum insulation layer formed to be able to maintain a vacuum in the internal space of a double-walled structure, and a vacuum evacuating layer for evacuating the space. an exhaust port provided on the wall surface of the double-walled structure, a filter for preventing powder scattering arranged to block the exhaust port, and a filter that is opened after the space has been evacuated to a certain extent. The structure includes an opening means for opening.

[0007]

[Function] According to the above configuration, when evacuation is performed from the atmospheric pressure at the beginning of evacuation to the viscous flow region, that is, when consideration must be given to the airflow to the extent that powder is scattered, the filter blocks the exhaust port. , the powder will not scatter. After the evacuation progresses to a certain extent and enters the intermediate flow region, that is, after the airflow is no longer strong enough to scatter powder, the opening means opens the filter, creating an exhaust path that does not pass through the filter. . Therefore,
The influence of filters with small exhaust conductance is removed,
Vacuum evacuation time is shortened.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, parts that are the same as those shown in FIG. 9 are given the same reference numerals. Here, the discharge cap 16 has a dish-shaped sealing portion 21 as shown in FIG. 3(a).
and the diameter of the exhaust port 17 is D1. Filter 1
8, as shown in FIG. 2, a filter body 22 made of ceramic fiber blanket is compressed into a disc shape, and a filter body 22 made of stainless steel is compressed into a disc shape, and then surrounded by a stainless wire mesh 23. , are arranged so that they can move toward or away from the lower end surface of the exhaust cap 16. Note that metal, soft plastic foam, or the like can also be used as the material for the filter body 22.

[0009] 19 is an opening means, and this opening means 19 is
As shown in FIG. 3(a), the sealing plug 24 is arranged inside the exhaust cap 16. This sealing plug 24 is for sealing the exhaust port 17 when the evacuation of the space 14 is completed, and has a large diameter sealing head 25 that can contact the sealing part 21 of the exhaust cap 16. , exhaust port 1
7, a medium diameter portion 26 that is movably inserted in the axial direction;
It has a small-diameter filter support portion 27 with a filter 18 attached to its tip. The exhaust port 17 is sealed by the head 2.
This is done by fixing the periphery of the lower surface of 5 to the sealing part 21.

In the above configuration, first, when evacuation is performed from the initial atmospheric pressure to the viscous flow region, as shown in FIG. 3(a), the sealing plug 24 of the opening means 19 is pulled up and the filter 18 is Block the exhaust port 17. As a result, an exhaust path E1 passing through the filter 18 is formed, so that the powder 20 is prevented from scattering due to vacuum exhaust. After the evacuation progresses to a certain extent and enters the intermediate flow region, the sealing plug 24 is pushed down to open the filter 18, as shown in FIG. 3(b). As a result, the exhaust path E2 that does not pass through the filter 18
is formed, the influence of the filter 18 having a small exhaust conductance is removed, and the evacuation time can be shortened.

As another embodiment of the present invention, FIG. 4(a)
As shown in FIG.
8, and when evacuation is performed from the intermediate flow region onward, a sealing plug 24 is attached as shown in Fig. 4(b).
The filter 18 may be opened by pressing down.

As still another embodiment of the present invention, FIG.
a) As shown in FIG.
4 may be provided with a cylindrical filter perforation 29 as shown. This filter perforation part 29 has a plurality of openings 30 at two stages in the axial direction of the peripheral wall, and a cutting edge 31 for filter perforation is formed at the tip.

In such a configuration, when evacuation is performed from the intermediate flow region onward, the sealing plug 24 is pushed down and its cutting edge 31 closes the filter 1, as shown in FIG. 5(b).
8 is bored in the center to form an exhaust path E2. This exhaust path E2 is connected to the filter perforation 29 as shown in the figure.
It passes through the distal opening 30, the hollow part, and the proximal opening 30. That is, since this exhaust path E2 does not pass through the filter 18, the influence of the filter 18 is removed, and the evacuation time is shortened. As shown in FIG. 6, the filter 18 in this case is not provided with a wire mesh at the perforated portion so that the central portion thereof can be easily perforated by the filter perforated portion 29.

The relationship between the exhaust conductance of the filter 18 and the evacuation time will be explained in detail as follows. Generally, as shown in FIG. 7, when the inside of the container 32 is evacuated by the exhaust pump 34 through the conduit 33, the following equation (
1) and (2) hold true.

[0015]Q=C(P1-P0)...
(1) 1/S1 = 1/C+1/S0 ... (2) Here, Q = amount of gas exhausted (Torr・l/sec) C = conductance of conduit 33 (l/sec) P1 =
Pressure at the outlet of the container (Torr) P0 = Pressure at the exhaust pump side (Torr) S1 = Pumping speed at the outlet of the container (l/sec) S0 = Pumping speed at the exhaust pump side (l/sec) (1) The formula is the amount of gas To shorten the exhaust time by increasing Q, exhaust conductance C
This shows that it is sufficient to increase . Furthermore, equation (2) indicates that when the exhaust conductance C is small, S1≈C, which means that increasing the exhaust speed S0 of the exhaust pump 34 has almost no effect. Regarding the exhaust conductance C, the conduit 33 is circular and the gas has a temperature of 20
It is known that the following equation (3) holds true over a wide pressure range in the case of air at ℃.

C=182・(D4/L)・P+12.1・(D3
/L)・(1+252 PD)/(1+312 PD
) ... (3) Here, D = Diameter of the conduit 33 (cm) L = Length of the conduit 33 (cm) P = (P1 + P0 ) / 2 (Torr) This (3)
Using the equation, the exhaust conductance of the filter 35 as shown in FIG. 8 can be determined as follows. That is, since the filter 35 has a large number of ventilation holes 36, the exhaust conductance of each ventilation hole 36 is reduced to C.
If i, then from equation (3) Ci = 182 ・(d4 /l)・P+12.1・(
d3 /l)・(1+252 Pd)/(1+312
Pd)...(4) Here, d=diameter of the ventilation hole 36 (c
m) l = Thickness of filter 35 (cm) If the number of ventilation holes 36 is n, the exhaust conductance C0 of the entire filter 35 is: C0 = ΣCi = nCi (5) Here, n =
(πD2 /4) / (πd2 /4) ... (6) D=
Diameter (cm) of Filter 35 Normally, the average particle diameter of the powder 20 is several tens of microns, so the diameter d of the vent hole 36 of the filter 35 that prevents its scattering is considered to be about several microns. Now, as an example of the conventional filter 18 shown in FIG. 9, l=0.6 cm,
D=D1=4cm, d=1μm=10-4cm, P=
The exhaust conductance at 5 Torr is calculated from equations (4) and (5) as follows.

Ci =182×((10-4)4/0.
6 )×5+12.1× ((10
-4)3/0.6)×(1+252×5×10−
4)/ (1+312 ×5×10
-4) =1.52×10-13 +1
．． 96×10−11 =1.98×10−11 l
/sec n=(π×42 /4)/(π×
(10-4)2/4)=1.6×109 pieces
C0 =1.98×10-11×1.6×109
= 0.03 1/sec, and it can be seen that the exhaust conductance C0 is very small, which makes the exhaust time longer.

By the way, powder scattering prevention filters are used to prevent powder from scattering due to the airflow generated during vacuum evacuation, but the airflow that causes powder to scatter must be taken into consideration at best when the airflow is generated during evacuation. It is thought that there is no need to consider the range from the atmospheric pressure at the initial stage to the viscous flow region, and from the intermediate flow region where the pressure is lower than the viscous flow region to the molecular flow region.

On the other hand, as can be seen from equation (3), the exhaust conductance C of the filter is relatively large from the atmospheric pressure where the average pressure P is large to the viscous flow region, so evacuation does not require a long time. It is thought that evacuation time becomes significantly longer in intermediate flow regions and molecular flow regions where conductance decreases.

Therefore, in the conventional case shown in FIG.
Since the exhaust conductance of the filter affects all areas, there is a drawback that the evacuation time is longer. In contrast, in the present invention, since the opening means 19 of the filter 18 is provided, by opening the filter 18 during the exhaust process, the influence of the filter 18 having a small exhaust conductance can be removed thereafter. Therefore, the evacuation time in the intermediate flow region and the molecular flow region can be shortened, and the total evacuation time can be shortened. The filter 18 opens when the pressure inside the container reaches the intermediate flow region, but if the container and the same exhaust system are the same, the evacuation time until reaching the intermediate flow region is approximately the same, so the evacuation time can be managed with.

[0021]

[Effects of the Invention] As described above, according to the present invention, the exhaust port is blocked with a filter for preventing powder scattering, and a hole opening means is provided to open the filter after the vacuum evacuation has progressed to a certain extent. During evacuation from the atmospheric pressure to the viscous flow region, the filter can prevent powder from scattering, and during evacuation from the intermediate flow region to the molecular flow region, the aperture means opens the filter to reduce the exhaust conductance. By removing the influence of a filter with a small value, evacuation time can be shortened.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a powder vacuum insulation container according to an embodiment of the present invention.

FIG. 2 is a sectional view of the filter for preventing powder scattering in FIG. 1.

FIG. 3 is an enlarged cross-sectional view of main parts in FIG. 1.

FIG. 4 is a cross-sectional view of essential parts in another embodiment of the present invention.

FIG. 5 is a sectional view of essential parts in still another embodiment of the present invention.

6 is a detailed sectional view of the filter for preventing powder scattering in FIG. 5. FIG.

FIG. 7 is an explanatory diagram of the exhaust conductance when the container is evacuated.

FIG. 8 is a perspective view of the filter for explaining the exhaust conductance of the filter for preventing powder scattering.

FIG. 9 is a sectional view showing an example of a conventional powder vacuum insulation container.

[Explanation of symbols]

12 Outer container 13 Inner container 14 Space 15 Powder vacuum insulation layer 17 Exhaust port 18 Filter 19 Opening means

Claims (1)

[Claims] 1. A powder vacuum insulation layer formed to be able to maintain a vacuum in an internal space of a double wall structure, and a powder vacuum insulation layer provided on a wall surface of the double wall structure to evacuate the space. A powder vacuum insulator characterized by having an exhaust port, a filter for preventing powder scattering arranged to block the exhaust port, and an opening means for opening the filter after the space has been evacuated to a certain extent. .