U.S. patent application number 11/546279 was filed with the patent office on 2007-04-19 for method of manufacturing low-temperature storage, and low-temperature storage.
This patent application is currently assigned to SANYO ELECTRIC CO., LTD.. Invention is credited to Yasushi Sakata, Hidetoshi Shinya.
Application Number | 20070084231 11/546279 |
Document ID | / |
Family ID | 37671904 |
Filed Date | 2007-04-19 |
United States Patent
Application |
20070084231 |
Kind Code |
A1 |
Shinya; Hidetoshi ; et
al. |
April 19, 2007 |
Method of manufacturing low-temperature storage, and
low-temperature storage
Abstract
An object is to provide a method of manufacturing a
low-temperature storage in which an insulating performance of an
insulating box article is enhanced, and an amount of contents of an
inner box can be enlarged. In the low-temperature storage
comprising: the insulating box article constituted by placing a
foamed insulating material between an outer box and the inner box;
and a vacuum insulating panel disposed on the surface of the outer
box on the side of the foamed insulating material, a thickness
dimension of the foamed insulating material between the inner box
and the vacuum insulating panel is set so that a temperature of the
surface of the vacuum insulating panel on the side of the inner box
is not less than a predetermined temperature.
Inventors: |
Shinya; Hidetoshi;
(Gunma-ken, JP) ; Sakata; Yasushi;
(Tatebayashi-shi, JP) |
Correspondence
Address: |
ARMSTRONG, KRATZ, QUINTOS, HANSON & BROOKS, LLP
1725 K STREET, NW
SUITE 1000
WASHINGTON
DC
20006
US
|
Assignee: |
SANYO ELECTRIC CO., LTD.
Moriguchi-shi
JP
|
Family ID: |
37671904 |
Appl. No.: |
11/546279 |
Filed: |
October 12, 2006 |
Current U.S.
Class: |
62/371 ;
62/457.7 |
Current CPC
Class: |
F25D 2201/126 20130101;
Y10T 29/49359 20150115; F25D 11/04 20130101; F25D 2400/10 20130101;
F25D 23/065 20130101; F25B 2500/08 20130101; F25D 2201/14 20130101;
F25B 2500/06 20130101 |
Class at
Publication: |
062/371 ;
062/457.7 |
International
Class: |
F25D 3/08 20060101
F25D003/08 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 13, 2005 |
JP |
298722/2005 |
Claims
1. A method of manufacturing a low-temperature storage comprising:
an insulating box article constituted by placing a foamed
insulating material between an outer box and an inner box; and a
vacuum insulating panel disposed on the surface of the outer box on
the side of the foamed insulating material, wherein a thickness
dimension of the foamed insulating material between the inner box
and the vacuum insulating panel is set so that a temperature of the
surface of the vacuum insulating panel on the side of the inner box
is not less than a predetermined temperature.
2. The method of manufacturing the low-temperature storage
according to claim 1, wherein the thickness dimension of the foamed
insulating material is set so that the temperature of the surface
of the vacuum insulating panel on the side of the inner box is not
less than a low-temperature-resistant limit temperature of the
vacuum insulating panel on conditions that a temperature in the
inner box is -80.degree. C. or less.
3. The method of manufacturing the low-temperature storage
according to claim 1, wherein a glass wool is disposed in a sealed
vacuum container to constitute the vacuum insulating panel.
4. A low-temperature storage comprising: an insulating box article
constituted by placing a foamed insulating material between an
outer box and an inner box; and a vacuum insulating panel disposed
in the foamed insulating material, wherein the vacuum insulating
panel is constituted by disposing a glass wool in a sealed vacuum
container, and the inside of the inner box is cooled at a low
temperature of -80.degree. C. or less.
5. The low-temperature storage according to claim 4, wherein the
vacuum insulating panel is disposed on the surface of the outer box
on the side of the foamed insulating material, and a temperature of
the surface of the vacuum insulating panel on the side of the inner
box is set to be not less than a low-temperature-resistant limit
temperature of the vacuum insulating panel.
6. The method of manufacturing the low-temperature storage
according to claim 2, wherein a glass wool is disposed in a sealed
vacuum container to constitute the vacuum insulating panel.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a low-temperature storage
constituted of an insulating box article having a foamed insulating
material and a vacuum insulating panel between an outer box and an
inner box, and a method of manufacturing the low-temperature
storage, more particularly to a low-temperature storage in which
the inside of an inner box is set to an extremely low temperature
of, for example, -80.degree. C. or less.
[0002] Heretofore, in the insulating box article constituting a
low-temperature storage such as a refrigerator or a freezer, a
space constituted by combining an inner box and an outer box is
filled with a foamed insulating material to reduce a leakage of
cold in the inner box. At this time, a temperature difference
between the outside and the inside of the inner box is considered
in determining a thickness of the insulating material to fill
between the inner box and the outer box. However, to keep the
temperature in the inner box at an extremely low temperature of,
for example, -80.degree. C. or less, a considerable thickness of
the insulating material has to be secured. Therefore, to secure a
storage amount of a storage chamber of the inner box, the
low-temperature storage itself is enlarged, and power consumption
is large.
[0003] To solve the problem, as a technique for reducing a
thickness dimension of the insulating box article, a vacuum
insulating material is disposed in a space between the inner box
and the outer box, and gaps among them are filled with a foamed
insulating material such as urethane foam (see Japanese Patent
Application Laid-Open No. 8-68591). This vacuum insulating material
is constituted by putting, in a bag-like container constituted of a
multilayered film, a gas-permeable bag including an inorganic fine
powder and preliminarily formed into a predetermined shape;
discharging air from the bag; and then heat-sealing the bag. In
consequence, there is obtained an insulating capability greater
than an insulating effect obtained by filling the gaps with the
usual foamed insulating material, which makes it possible to reduce
the thickness dimension of the insulating box article.
[0004] However, in the method of disposing the conventional vacuum
insulating material in the insulating box article, the
above-described temperature in the inner box is set to an extremely
low temperature such as -80.degree. C., the cold in the inner box
reaches the surface of the bag which covers the vacuum insulating
material, and the temperature of the surface of the bag lowers
below a heat-resistant temperature of the bag owing to the cold. As
a result, thermal contraction occurs, and the bag itself is
destroyed. Therefore, the main body of the vacuum insulating
material cannot exert its insulating capability. In consequence,
the above method cannot maintain the insulating effect.
SUMMARY OF THE INVENTION
[0005] Therefore, to solve the conventional technical problems, an
object of the present invention is to provide a low-temperature
storage and a method of manufacturing a low-temperature storage in
which an insulating performance of an insulating box article is
enhanced, and an amount of contents of an inner box can be
enlarged.
[0006] According to a first invention of the present application,
in a method of manufacturing a low-temperature storage comprising:
an insulating box article constituted by placing a foamed
insulating material between an outer box and an inner box; and a
vacuum insulating panel disposed on the surface of the outer box on
the side of the foamed insulating material, a thickness dimension
of the foamed insulating material between the inner box and the
vacuum insulating panel is set so that a temperature of the surface
of the vacuum insulating panel on the side of the inner box is not
less than a predetermined temperature.
[0007] In the method of manufacturing the low-temperature storage
in a second invention of the present application, the above
invention is characterized in that the thickness dimension of the
foamed insulating material is set so that the temperature of the
surface of the vacuum insulating panel on the side of the inner box
is not less than a low-temperature-resistant limit temperature of
the vacuum insulating panel on conditions that a temperature in the
inner box is -80.degree. C. or less.
[0008] In the method of manufacturing the low-temperature storage
in a third invention of the present application, the above
invention is characterized in that a glass wool is disposed in a
sealed vacuum container to constitute the vacuum insulating
panel.
[0009] According to a fourth invention of the present application,
in a low-temperature storage comprising: an insulating box article
constituted by placing a foamed insulating material between an
outer box and an inner box; and a vacuum insulating panel disposed
in the foamed insulating material, the vacuum insulating panel is
constituted by disposing a glass wool in a sealed vacuum container,
and the inside of the inner box is cooled at a low temperature of
-80.degree. C. or less.
[0010] In the low-temperature storage of a fifth invention of the
present application, the above invention is characterized in that
the vacuum insulating panel is disposed on the surface of the outer
box on the side of the foamed insulating material, and a
temperature of the surface of the vacuum insulating panel on the
side of the inner box is set to be not less than a
low-temperature-resistant limit temperature of the vacuum
insulating panel.
[0011] According to the method of manufacturing the low-temperature
storage in the first invention of the present application, in the
low-temperature storage comprising: the insulating box article
constituted by placing the foamed insulating material between the
outer box and the inner box; and the vacuum insulating panel
disposed on the surface of the outer box on the side of the foamed
insulating material, the thickness dimension of the foamed
insulating material between the inner box and the vacuum insulating
panel is set so that the temperature of the surface of the vacuum
insulating panel on the side of the inner box is not less than the
predetermined temperature. Accordingly, a leakage of cold in the
inner box can be reduced, and wasting of useless cooling energy can
be inhibited.
[0012] Moreover, as in the second invention of the present
application, even when the temperature in the inner box is
-80.degree. C. or less, the thickness dimension of the foamed
insulating material is determined so that the temperature of the
surface of the vacuum insulating panel on the side of the inner box
is not less than a predetermined temperature such as the
low-temperature-resistant limit temperature of the vacuum
insulating panel. In consequence, while destruction of the vacuum
insulating panel itself due to the low temperature can be avoided
in advance, the thickness dimension of the insulating box article
can further be reduced.
[0013] Therefore, even in the low-temperature storage in which the
temperature in the inner box is extremely low, an insulating
capability of the insulating box article itself is enhanced, and
the dimension can be reduced. In consequence, even when an
outer-shape dimension is similar to that of a conventional
low-temperature storage, a storage volume of the inner box can be
enlarged.
[0014] According to the third invention of the present application,
in the above invention, the glass wool is disposed in the sealed
vacuum container to constitute the vacuum insulating panel.
Therefore, even when the thickness dimension of the vacuum
insulating panel is reduced, a great insulating effect can be
obtained. Therefore, the thickness dimension of the insulating box
article can further be reduced, and the storage volume of the inner
box can be enlarged.
[0015] According to the fourth invention of the present
application, the low-temperature storage comprises: the insulating
box article constituted by placing the foamed insulating material
between the outer box and the inner box; and the vacuum insulating
panel disposed in the foamed insulating material. The vacuum
insulating panel is constituted by disposing the glass wool in the
sealed vacuum container, and the inside of the inner box is cooled
at the low temperature of -80.degree. C. or less. Therefore, even
in the extremely-low-temperature storage in which the inside of the
inner box is at -80.degree. C. or less, while the thickness
dimension of the insulating box article is reduced, a necessary
insulating effect can be obtained. Therefore, while the thickness
dimension of the insulating box article is reduced, the
low-temperature storage can be constituted so as to prevent a
temperature of the outer surface of the outer box from being
lowered below a dew point. It is possible to prevent a disadvantage
that the outer surface of the outer box is wetted or a disadvantage
that the useless cooling energy is wasted owing to the leakage of
the cold in the inner box.
[0016] Moreover, according to the fifth invention of the present
application, in the above invention, the vacuum insulating panel is
disposed on the surface of the outer box on the side of the foamed
insulating material, and the temperature of the surface of the
vacuum insulating panel on the side of the inner box is set to be
not less than the low-temperature-resistant limit temperature of
the vacuum insulating panel. Therefore, it is possible to avoid in
advance the destruction of the vacuum insulating panel itself due
to the low temperature.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a front view of an extremely-low-temperature
storage to which the present invention is applied;
[0018] FIG. 2 is a side view of FIG. 1;
[0019] FIG. 3 is a plan view of FIG. 1;
[0020] FIG. 4 is a diagram showing a temperature in each thickness
position of an insulating box article;
[0021] FIG. 5 is a partially enlarged sectional view in the
vicinity of an opening; and
[0022] FIG. 6 is a refrigerant circuit diagram in the present
embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0023] An embodiment of the present invention will be described
hereinafter in detail with reference to the drawings. An
extremely-low-temperature storage 1 of the present embodiment is
used in, for example, storing a frozen food to be stored at a low
temperature over a long period or storing a living tissue, a
specimen or the like at an extremely low temperature, and a main
body of the storage is constituted of an insulating box article 2
having its top opened.
[0024] This insulating box article 2 is constituted of: an outer
box 3 made of a steel plate; an inner box 4 made of a stainless
steel, each of the outer box and the inner box having its top
opened; breakers 5 made of a synthetic resin and connecting upper
ends of the box 3 to those of the box 4, respectively; and a
polyurethane resin insulating material 7 with which a space
enclosed by the outer box 3, the inner box 4 and the breakers 5 is
filled by an on-site foaming system. The inside of the inner box 4
is a storage chamber 8 having its top opened.
[0025] In the present embodiment, to set a targeted temperature in
the storage chamber 8 (hereinafter referred to as the in-chamber
temperature) at, for example, -80.degree. C. or less, the
insulating box article 2 which separates the inside of the storage
chamber 8 from outside air requires a great insulating capability
as compared with a low-temperature chamber having its in-chamber
temperature set in the vicinity of 0.degree. C. Therefore, to
secure the insulating capability by the only polyurethane resin
insulating material 7, the material has to be formed into a
considerable thickness of, for example, about 100 mm. Therefore,
there is a problem that a sufficient storage amount of the storage
chamber 8 cannot be secured with a limited main-body dimension.
[0026] Therefore, in the insulating box article 2 of the present
embodiment, a vacuum insulating panel 30 made of a glass wool is
disposed on left and right side surfaces of the outer box 3 and a
front inner wall surface of the article. The panel is once
tentatively fixed with a double-sided adhesive tape, and the
insulating material 7 is placed between the panel and both the
boxes 3 and 4 by the on-site foaming system.
[0027] This vacuum insulating panel 30 is constituted by disposing
the glass wool having an insulating property in a container
constituted of a multilayered film of aluminum, a synthetic resin
or the like which does not have any gas permeability. Thereafter,
air is discharged from the container by predetermined vacuum
exhaust means, and an opening of the container is heat-sealed.
Therefore, according to insulating effectiveness of this vacuum
insulating panel 30, while the thickness dimension of the foamed
insulating material 7 is reduced as compared with a conventional
material, the same insulating effect can be obtained.
[0028] Here, with reference to FIG. 4, there will be described
experiment results of temperatures of portions in a case where the
vacuum insulating panel 30 having a thickness of 15 mm is used. In
this experiment, assuming that a set temperature in the storage
chamber 8 was -80.degree. C. and an outside air temperature was
+30.degree. C., the temperatures were measured. The vacuum
insulating panel 30 manufactured by the above-described method is
disposed close to an inner wall of the outer box 3. In the present
experiment, since the insulating box article 2 has a thickness of
70 mm, the thickness of the foamed insulating material 7 is set to
55 mm from the inner wall of the inner box.
[0029] According to this experiment, the temperature in the storage
chamber 8 was -80.degree. C., whereas the temperature of the
surface of the inner box 4 (distance of 0 from the inner box 4
surface) was -81.6.degree. C., the temperature of the surface of
the vacuum insulating panel 30 on the side of the storage chamber 8
(distance of 55 mm from the inner box 4 surface) was -39.19.degree.
C., and the temperature of the surface of the outer box 3 (distance
of 70 mm from the inner box 4 surface) was +28.25.degree. C. It is
to be noted that the insulating material 7 constitutes a portion
ranging from the inner box 4 surface to the surface of the vacuum
insulating panel 30 on the side of the storage chamber 8.
Therefore, a change of the temperature is proportional to that of
the thickness of the portion. Moreover, the vacuum insulating panel
30 constitutes a portion ranging from the surface of the vacuum
insulating panel 30 on the side of the storage chamber 8 to the
outer box 3 surface. Therefore, it is considered that the change of
the temperature is proportional to that of the thickness of the
portion.
[0030] In a case where a low-temperature-resistant limit
temperature of the container in which the vacuum insulating panel
30 is put is, for example, -60.degree. C. to -70.degree. C., when
the thickness of the foamed insulating material 7 is about 40 mm,
the temperature of the surface of the vacuum insulating panel 30 on
the side of the storage chamber 8 can be set to a predetermined
temperature of about -50.degree. C. It is possible to securely
avoid destruction of the container itself of the vacuum insulating
panel 30 due to the low temperature.
[0031] Therefore, in the present embodiment, the thickness of the
foamed insulating material 7 is set to about 55 mm, and the
thickness of the vacuum insulating panel 30 is set to 15 mm as in
the present experiment. Accordingly, the temperature of the surface
of the vacuum insulating panel 30 on the side of the storage
chamber 8 can be set to -39.19.degree. C. which is largely above a
heat-resistant temperature. It is possible to securely prevent
destruction of the vacuum insulating panel 30 itself due to the low
temperature.
[0032] Moreover, in this case, if the only insulating material 7 is
used, the thickness dimension of the insulating box article 2 needs
to be about 100 mm. However, as in the present experiment, the
entire thickness dimension can be suppressed to about 70 mm. While
the thickness dimension of the insulating box article 2 is reduced,
a necessary insulating effect can be obtained. Therefore, even
while the thickness dimension of the insulating box article 2 is
reduced, it is possible to inhibit a disadvantage that the
temperature of the outer surface of the outer box 3 is not more
than a dew point. In consequence, even if an outer-shape dimension
is similar to a conventional outer-shape dimension, it is possible
to remarkably expand a storage volume of the storage chamber 8.
[0033] It is to be noted that in a case where the temperature in
the storage chamber 8 is set to, for example, -152.degree. C., when
the vacuum insulating panel 30 having a thickness of about 15 mm is
used, the thickness dimension of the foamed insulating material 7
is set to about 120 mm. Accordingly, it is possible to avoid a
disadvantage that the temperature of the surface of the vacuum
insulating panel 30 on the side of the storage chamber 8 is the
low-temperature-resistant limit temperature of the container in a
range of -60.degree. C. to -70.degree. C. Even in this case, while
the thickness dimension of the insulating box article 2 is
similarly reduced, the necessary insulating effect can be
obtained.
[0034] It is to be noted that the thickness dimension of the vacuum
insulating panel 30 is not limited to the above dimension.
Therefore, especially, in a case where the thickness of the vacuum
insulating panel 30 is set to about 10 to 20 mm, when the thickness
dimension of the foaming insulating material 7 is set to about 40
to 120 mm, it is possible to maintain an insulating performance of
the insulating box article 2 in the extremely-low-temperature
storage at -80.degree. C. or less, or -150.degree. C. or less.
[0035] Moreover, as shown in FIG. 5, the tops of the breakers 5 of
the insulating box article 2 constituted as described above are
formed into staircase-like shapes, and an insulating door 9 is
attached to the breakers via packing members 11 so as to be
rotatable centering on one end, that is, a rear end in the present
embodiment. An inner lid 19 constituted of an insulating material
is disposed so as to open or close an opening in the top of the
storage chamber 8. On the underside of the insulating door 9, a
pressing portion 9A is formed so as to protrude downwards.
Accordingly, after the opening in the top of the storage chamber 8
is closed with the inner lid 19, the insulating door 9 is closed,
whereby the pressing portion 9A of the insulating door 9 presses
the inner lid 19. In consequence, the opening in the top of the
storage chamber 8 is openably closed. A handle portion 10 is
disposed on the other end of the insulating door 9, that is, a
front end thereof in the present embodiment. When the handle
portion 10 is operated, the insulating door 9 is opened or
closed.
[0036] Furthermore, an evaporator (refrigerant pipe) 13
constituting a refrigerant circuit of a freezing device R is
heat-exchangeably attached to the peripheral surface of the inner
box 4 on the side of the foamed insulating material 7. A mechanical
chamber (not shown) is constituted in a lower part of the
insulating box article 2. In this mechanical chamber, a compressor
14 and a condenser 15 are arranged to constitute a refrigerant
circuit 12 of the freezing device R, and there is also disposed a
blower (not shown) for air-cooling the compressor 14 and the
condenser 15. Moreover, the compressor 14, the condenser 15, a
drier 17, a heat exchanger 16, a capillary tube 18 as a pressure
reducing unit and the evaporator 13 are successively annularly
connected to one another by piping as shown in FIG. 6, thereby
constituting the refrigerant circuit 12 of the freezing device R.
It is to be noted that the heat exchanger 16 is disposed in the
foamed insulating material 7.
[0037] FIG. 6 is a refrigerant circuit diagram in which the rotary
compressor 14 is used. The compressor 14 is connected to a
sub-cooler 20, and is constituted to discharge a refrigerant to a
refrigerant discharge tube 21. The refrigerant has once released
heat in the outside and thereafter returned into a shell of a
sealed container to be compressed again. The compressor 14 on a
discharge side is connected to the condenser 15 via the refrigerant
discharge tube 21, and the condenser 15 on an outlet side is
successively connected to the drier 17, the heat exchanger 16 and
the capillary tube 18 as pressure reducing means. The capillary
tube 18 on the outlet side is connected to the evaporator 13. The
evaporator 13 on the outlet side is connected to the compressor 14
on a suction side via a return pipe 22 and the heat exchanger
16.
[0038] In the present embodiment, the refrigerant circuit 12 is
filled with a mixed refrigerant of R245fa and R600, and a
non-azeotropic mixture refrigerant of R23 and R14. The refrigerant
R245fa is pentafluoropropane (CHF.sub.2CH.sub.2CF.sub.3) having a
boiling point of +15.3.degree. C., and R600 is a butane
(C.sub.4H.sub.10) having a boiling point of -0.5.degree. C. The
refrigerant R600 has a function of feeding a lubricant of the
compressor 14 and a mixed moisture that cannot be absorbed by the
drier 17 back into the compressor 14 in a state in which the
lubricant and the moisture are dissolved in the refrigerant.
However, R600 is a combustible substance. Therefore, when R600 is
mixed with incombustible R245fa at a predetermined ratio of
R245fa/R600=70/30 in the present embodiment, the mixture can be
treated as an incombustible mixture. Moreover, R23 is
trifluoromethane (CHF.sub.3) having a boiling point of
-82.1.degree. C., and R14 is tetrafluoromenthane (CF.sub.4) having
a boiling point of -127.9.degree. C.
[0039] Furthermore, in a composition of these mixed refrigerants in
the present embodiment, the mixed refrigerant of R245fa and R600
occupies 64 wt % of the whole composition, R23 occupies 24 wt %,
and R14 occupies 12 wt %.
[0040] In the above constitution, a high-temperature gas-like
refrigerant discharged from the compressor 14 is once discharged
from the sealed container to the sub-cooler 20 via the refrigerant
discharge tube on the side of the sub-cooler 20. After releasing
its heat, the refrigerant returns into the shell of the sealed
container via a refrigerant suction tube. The high-temperature
gas-like refrigerant which has once released its heat is compressed
in the sealed container of the compressor 14 again, and thereafter
discharged to the condenser 15 via the refrigerant discharge tube
21.
[0041] The high-temperature gas-like refrigerant which has flowed
into the condenser 15 is condensed to release its heat, and
liquefied. Thereafter, the moisture of the refrigerant is removed
by the drier 17. The refrigerant then flows into the heat exchanger
16 to exchange the heat with a low-temperature refrigerant in the
heat-exchangeably disposed return pipe 22. Accordingly, a
high-pressure gas refrigerant from the compressor 14 is cooled.
Therefore, the pressure of the mixed refrigerant passed through the
heat exchanger 16 is reduced by the capillary tube 18.
Subsequently, when the refrigerants successively flow into the
evaporator 13, the refrigerants R14, R23 evaporate and absorb
vaporization heat from a surrounding area to cool the evaporator
13. In this case, the temperature of the refrigerant can be
lowered, and a condensing process can be promoted to enhance a
cooling efficiency. The refrigerant is fed back to the compressor
14 via the heat exchanger 16 by the return pipe 22.
[0042] Consequently, it is possible to realize an extremely low
temperature of -80.degree. C. or less in the storage chamber 8. As
described above, the thickness dimension of the foamed insulating
material 7 of the insulating box article 2 forming the storage
chamber 8 is set in accordance with the targeted temperature in the
storage chamber 8 so that the temperature of the surface of the
vacuum insulating panel 30 on the side of the inner box 4 is not
less than the low-temperature-resistant limit temperature of the
vacuum insulating panel 30. Therefore, while the destruction of the
vacuum insulating panel 30 itself due to the low temperature is
avoided in advance, it is possible to realize the reduction of the
thickness dimension of the insulating box article 2 itself.
[0043] In consequence, it is possible to inhibit a disadvantage
that the temperature of the outer surface of the outer box 3 is not
more than the dew point. Therefore, even if the outer-shape
dimension is similar to the conventional outer-shape dimension, it
is possible to remarkably expand the storage volume of the storage
chamber 8. Even in a case where the thickness dimension of the
insulating box article 2 is reduced in this manner, since the
insulating capability can be enhanced, it is possible to reduce a
leakage of the cold in the storage chamber 8, and it is possible to
reduce power consumption.
[0044] Furthermore, the insulating capability of the insulating box
article 2 itself is enhanced. Therefore, in a case where the
opening is disposed in the top as in the present embodiment, even
when an opening close mechanism including the insulating door 9 to
close the top opening is simplified, the leakage of the cold in the
storage chamber 8 is not especially largely influenced. Therefore,
even in the extremely-low-temperature storage in which the
in-chamber temperature is set to -80.degree. C. or less as in the
present embodiment, it is not necessary to adopt a special opening
structure. It is possible to simplify the whole structure, and
reduction of costs can be realized.
* * * * *