U.S. patent application number 09/871982 was filed with the patent office on 2001-10-25 for full vacuum heat insulation box body and method for producing and disassembling the same.
This patent application is currently assigned to Mitsubishi Denki Kabushiki Kaisha. Invention is credited to Nishimoto, Yoshio.
Application Number | 20010033126 09/871982 |
Document ID | / |
Family ID | 26349728 |
Filed Date | 2001-10-25 |
United States Patent
Application |
20010033126 |
Kind Code |
A1 |
Nishimoto, Yoshio |
October 25, 2001 |
Full vacuum heat insulation box body and method for producing and
disassembling the same
Abstract
A heat insulation box body includes inner and outer boxes
forming a shell of the heat insulation box body and triangular
structural materials inserted in the shell held by close-contact by
means of a vacuum. Further, at the time of disassembling the heat
insulation box body after scrapping, a shell surface is cut and air
is introduced into the inside of the shell to return the state of
the shell to an atmospheric pressure state and then respective
members are separated from each other.
Inventors: |
Nishimoto, Yoshio;
(Chiyoda-ku, JP) |
Correspondence
Address: |
OBLON SPIVAK MCCLELLAND MAIER & NEUSTADT PC
FOURTH FLOOR
1755 JEFFERSON DAVIS HIGHWAY
ARLINGTON
VA
22202
US
|
Assignee: |
Mitsubishi Denki Kabushiki
Kaisha
2-3, Marunouchi 2-chome
Chiyoda-ku
JP
100-8310
|
Family ID: |
26349728 |
Appl. No.: |
09/871982 |
Filed: |
June 4, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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09871982 |
Jun 4, 2001 |
|
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09227855 |
Jan 11, 1999 |
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Current U.S.
Class: |
312/406 |
Current CPC
Class: |
B29C 44/1242 20130101;
Y10S 62/13 20130101; F25D 2400/04 20130101; F25D 2201/1262
20130101; Y10T 428/231 20150115; F25D 2201/14 20130101; Y10T
29/49359 20150115; Y10S 29/044 20130101; F25D 23/062 20130101 |
Class at
Publication: |
312/406 |
International
Class: |
A47B 096/04 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 27, 1998 |
JP |
10-013873 |
Jul 23, 1998 |
JP |
10-207647 |
Claims
What is claimed and new and desired to be secured by Letters Patent
of the United States is:
1. A vacuum heat insulation box body comprising: a shell comprising
inner and outer boxes, and heat insulation walls, the inside of
which are to be kept in a vacuum state; and structural materials
having continuous pores provided inside said insulation walls of
said shell, and between said inner and outer boxes; wherein said
structural materials are held to said shell only by close-contact
caused by means of a vacuum.
2. A vacuum heat insulation box body according to claim 1, wherein
said shell of said heat insulation box body has an uneven surface,
and said structural materials abutting said uneven surface include
moldings formed of crushed matters of a resin foam.
3. A vacuum heat insulation box body according to claim 1, wherein
said structural materials comprise parts provided with grooves or
holes for exhausting air from said continuous pores.
4. A vacuum heat insulation box body according to claim 1, wherein
said structural materials are constituted by a resin foam having
open cells.
5. A vacuum heat insulation box body according to claim 1, wherein
said structural materials comprise a plurality of
triangular-section parts, each of said triangular-section parts
being disposed in a middle layer of said shell in the direction of
wall thickness, or in a layer abutting on an even surface of said
shell.
6. A vacuum heat insulation box body according to claim 5, wherein
said triangular-section parts are formed of foamed polystyrene
having open cells.
7. A vacuum heat insulation box body according to claim 6, wherein
said foamed polystyrene having open cells includes flattened cells
which are spread in a direction perpendicular to the direction of
wall thickness.
8. A vacuum heat insulation box body according to claim 1, wherein
ajoint portion between said inner and outer boxes comprises: a
groove of a predetermined depth formed by bending inwardly one of
said inner and outer boxes, said groove being filled with a liquid
substance having an adhesive sealing function; and; an end side
portion formed in the other of said inner and outer boxes so as to
be insertable into a deep portion of said groove; wherein joining
and sealing of said joint portion are performed by said liquid
substance by utilizing mutual attraction force produced by
evacuation of said shell.
9. A vacuum heat insulation box body according to claim 1, further
comprising: an opening portion formed in said outer box, said
opening portion configured to be closed by a plate member, said
opening portion configured to allow said structural materials to be
inserted into said shell through said opening portion; a joint
portion between said outer box and said plate member comprising a
groove of a predetermined depth formed by bending inwardly one of
said outer box and said plate member, said groove being filled with
a liquid substance having an adhesive sealing function; and an end
side portion formed in the other of said outer box and said plate
member and configured to be inserted into a deep portion of said
groove; wherein joining and sealing of said joint portion are
performed by said liquid substance by utilizing mutual attraction
force produced at the time of evacuation of said shell.
10. A vacuum heat insulation box body according to claim 8, wherein
said groove is formed by bending an end edge portion inwardly in a
zigzag configuration.
11. A vacuum heat insulation box body according to claim 8, wherein
said groove has a wide reservoir portion in its upper portion for
reserving the liquid substance so as to prevent it from overflowing
from the groove.
12. A vacuum heat insulation box body according to claim 8, wherein
said liquid substance is constituted by an adhesive agent
containing particles or powder of a metal oxide or a metal
nitride.
13. A vacuum heat insulation box body according to claim 10,
wherein an indicia is provided in the outer circumferential surface
of the zigzag bent portion.
14. A method for producing a vacuum heat insulation box body,
comprising the steps of: integrating an inner box and an outer box
into a shell which is opened in an open bottom surface of said
outer box; inserting a first structural material having continuous
pores and a triangular section into a space formed between the
inner and outer boxes first shell through the opening of said first
shell, by inserting a bottom side portion of said first structural
material first; inserting a second structural material having
continuous pores and a triangular section into said space through
said opening of said first shell by inserting a vertex portion of
said second structural material first to thereby fill said space of
said first shell; blocking the opening of said first shell with a
third structural material having continuous pores and a shape of a
flat plate; enclosing said third structural material with a plate
member to seal the joint portion between said plate member and said
first shell to thereby fully close said shell; and evacuating said
second shell.
15. A method for producing a vacuum heat insulation box body
according to claim 14, wherein said first structural material is to
be brought into contact with an uneven surface of the shell is
first inserted, then said second triangular-section structural
material having no uneven surface is inserted with a vertex portion
thereof inserted first, so that said space of said first shell is
filled with said structural materials.
16. A method for producing a vacuum heat insulation box body
according to claim 14, wherein evacuation of said second shell is
performed under the condition that said inner and outer boxes and
said structural materials inserted between said inner and outer
boxes are not fixed by an adhesive agent, or the like.
17. A method for producing a vacuum heat insulation box body
according to claim 14, further comprising the steps of: bending at
least one member of said first shell and said plate member for
covering said opening of said first shell at the joint portion to
form a groove of a predetermined depth; filling said groove with a
liquid substance formed of an adhesive agent containing particles
or powder of a metal oxide or a metal nitride; and solidifying said
liquid substance after the other member of said first shell and
said plate member is inserted into said groove which is filled with
said liquid substance, while evacuating said fully closed second
shell to thereby perform both joining and sealing at said joint
portion.
18. A method for disassembling a vacuum heat insulation box body
having a shell constituted by inner and outer boxes, and structural
materials disposed in said shell, said inner and outer boxes and
said structural materials being fixed by close-contact caused by
means of a vacuum, comprising the steps of: cutting a surface of
said shell to thereby introduce air into the inside of said shell
so as to allow the inside state of said shell to return to an
atmospheric pressure state; and separating inner and outer boxes of
said shell and said structural materials from each other.
19. A method for disassembling a vacuum heat insulation box body
according to claim 18, wherein in said full vacuum heat insulating
box body, a joint portion between said inner and outer boxes is
constituted by a groove formed by bending an end edge portion of
one of said inner and outer boxes inward in a zigzag configuration,
wherein said groove is filled with a liquid substance, and wherein
an end side portion is formed in the other of said inner and outer
of said boxes so as to be able to be inserted into a deep portion
of said groove; wherein said cutting step further comprises
providing a notch in an outer surface of said one member having the
zigzag bent portion along a position corresponding to said zigzag
bent portion; and separating from each other said inner and outer
boxes of said shell and said structural materials.
20. A method for disassembling a vacuum heat insulation box body
according to claim 18, wherein in said vacuum heat insulating box
body, said outer box has an opening portion used for inserting
structural materials which is blocked with a plate member, and a
joint portion between said outer box and said plate member is
constituted by a groove formed by bending an end edge portion of
one member of said outer box and said plate member inward in a
zigzag and filled with a liquid substance, and an end side portion
is formed in the other of them so as to be inserted into a deep
portion of said groove; wherein said cutting step further comprises
providing a notch in an outer circumferential surface of said one
member having the zigzag bent portion along a position
corresponding to said zigzag bent portion; and said outer box and
said plate member are then separated from each other and the
materials of said shell and said structural materials are
recovered.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to heat insulation walls
requiring heat insulation in a heat insulation box body such as a
refrigerator, or the like, in which wall surfaces are formed of
thin metal plates, resin moldings, or the like. More particularly,
the present invention relates to a full vacuum heat insulation box
body in which porous structural materials are disposed in a shell
constituting heat insulation walls for the purpose of preventing
deformation so that a vacuum is kept, a refrigerator using such a
full vacuum heat insulation box body, a method for producing such a
full vacuum heat insulation box body, and a method for
disassembling such a full vacuum heat insulation box body.
[0003] 2. Description of the Related Art
[0004] Conventionally, a shell of a refrigerator, or the like, is
so constituted that an outer box is formed of a thin metal plate
such as an iron plate, an inner box is formed of a resin molding,
and closed-cell foaming urethane used for forming a structural
material, is injected into a gap between the inner and outer boxes
and foamed so that the gap is filled with the structural
material.
[0005] FIG. 16 is a flow chart illustrating a process of producing
a conventional refrigerator using closed-cell foaming urethane as a
heat insulating material in walls, and FIG. 17 illustrates a
foaming urethane injection step in the process.
[0006] That is, in a conventional refrigerator, or the like, an
inner box 2 obtained by attaching necessary members, such as an
anchor for fixing interior parts, piping for supplying a
refrigerant, etc., to a vacuum molding of an ABS resin sheet, is
inserted in an outer box 1 of a formed product obtained by bending
a steel plate to thereby form a shell. Injection portions 4 are
provided in the outer box 1 (step 1) to inject a mixture solution 3
of foaming urethane.
[0007] After sheet metal worked parts are attached to the back and
bottom portions which are residual opening portions, a slight gap
in each engaging portion is sealed with a hot melt adhesive agent,
or the like, and further interior parts are partially assembled
(step 2).
[0008] The thus obtained box body is laid down as shown in FIG. 17,
and fixed in a foaming jig heated to an arbitrary temperature.
After a mixing head 5 is successively inserted into and fixed to
injection holes of the injection portions 4 provided in the outer
box 1, a mixture solution 3 of foaming urethane is discharged and
injected. Then, injection portions 4 are sealed with plugs. Because
the foaming urethane mixture solution 3, at the time of injection,
is a liquid having an expansion ratio in a range from several times
to tens of times, the mixture solution 3 flows in a flange portion
corresponding to the opening portions of the box body through the
injection portion 4 so as to disperse. Further, after some seconds,
a foaming agent is vaporized by reaction heat of raw materials and
thereby the foam is caused to fill the residual gap between the
inner box 2 and the outer box 1 with urethane foam. A heat
insulation box body thus formed can be taken out from the foaming
jig after some minutes, generally about 5 minutes from the
injection (step 3).
[0009] Residual parts, for example, electric parts such as a fan
motor and a light and interior parts such as shelves and various
kinds of casings are put in the thus obtained heat insulation box
body. After refrigerant circuit securing parts for securing a
refrigerant circuit are attached to the heat insulation box body,
the refrigerant circuit is charged with a refrigerant. Thus,
assembling of the product is completed (step 4).
[0010] Inspection of various kinds of functions of the completed
product is carried out through an actual operation so as to confirm
that the product is not defective (step 5).
[0011] When a package and documents pertinent to the obtained
product are prepared and added, the production is completed (step
6).
[0012] It has been found that the chlorine containing
1,1-dichloro-1-fluoroethane (HFC141b), which is one of
hydrochlorofluorocarbons that has been used as a foaming agent for
forming urethane foam used as a heat insulating material herein, is
a cause of ozone layer destruction. Accordingly, use of
hydrofluorocarbons or hydrocarbons which do not contain chlorine in
their molecules, has been proposed in recent years.
[0013] For example, a method for producing urethane foam by use of
hydrofluorocarbons such as 1,1,1,3,3-pentafluoropropane (HFC245fa)
and 1,1,1,4,4,4-hexafluorobutane (HFC356mffm) as a foaming agent is
disclosed in JP-A-2-235982, and a method for producing urethane
foam by use of hydrocarbon such as cyclopentane, or the like, as a
foaming agent is disclosed in JP-A-3-152160.
[0014] However, the heat insulating property of such urethane foam
is in a range from 19 to 20 mw/MK and clearly inferior to the heat
insulating property of 16 mw/MK of chlorofluorocarbons used before
issue of regulations on use of ozone layer destruction
substances.
[0015] Since the improvement of the heat insulating property of
urethane foam has reached a limit, a technique of applying a vacuum
heat insulation panel which has more than twice as higher heat
insulating property as the urethane foam as shown in the comparison
view of FIG. 18 has been proposed for a refrigerator, or the like,
allowing a reduction of electric power consumption without use of
any substance which causes ozone layer destruction.
[0016] For example, JP-A-60-243471 discloses a heat insulation box
body in which a member obtained by putting pulverized PUF in a
synthetic resin bag and vacuum-packing the pulverized PUF in the
form of a board is disposed inside walls, and JP-A-60-60483
proposes a refrigerator in which a vacuum heat insulation panel
having a gap which is provided in the flange side of a side plate
to allow PUF to flow in the gap is disposed in a side wall of the
refrigerator.
[0017] The vacuum heat insulation panel such as those proposed
above, has a structure shown in FIG. 19. A method for producing the
vacuum heat insulation panel will be described below. First, a core
material 11 having a porous structure such as an aggregate of
fibers or particles, a foam having open cells, or the like, is
inserted into a bag-like packing material 12. Then, in order to
generate a high quality heat insulating property, its inside is
deaerated by using a vacuum panel making machine 15 comprising
fusion-bonding devices 17 each having a heater 17a, sealing
pressure devices 18, and a vacuum control valve 16 as shown in FIG.
20. While a vacuum state is maintained, end edge portions 12a of
the packing material 12 containing the core material 11 are
heat-sealed to prevent external air from entering inside. Thus, a
vacuum heat insulation panel 13 shown in FIG. 19 is obtained.
Preferably, the inside of the vacuum panel making machine 15 is
kept to 10.sup.-2 torr when the end edge portions 12a are subjected
to fusion bonding. Therefore, adjustment of the degree of vacuum is
performed by use of the vacuum control valve 16 connected to an
evacuator not shown.
[0018] Accordingly, in the packing material 12, a thin metal film
layer is used as its intermediate layer for blocking or suppressing
entrance of gas from the outside into the vacuum heat insulation
panel to thereby keep a heat insulating property. A material having
excellent welding property is used as its inner layer so that
insertion openings can be sealed perfectly, and a material for
stably securing adhesion to urethane foam is used as its surface
layer so that generation of scratches is suppressed and bending
strength of walls in a box body such as a refrigerator, or the
like, can be secured. Because the packing material 12 is required
to have various characteristics as described above, a multilayer
sheet in which different materials are laminated to satisfy the
required characteristics is used.
[0019] Further, the core material 11 must have a strength higher
than atmospheric pressure to satisfy a function of holding the
panel shape in a vacuum state and the quantities of conducted heat
(heat conduction) and penetrated heat (heat radiation) through a
substance constituting the core material itself must be suppressed
to thereby contribute to improvement of heat insulating property.
Accordingly, a porous plate formed of a substance with small heat
transfer rate is used as the core material 11.
[0020] That is, in order to improve the heat insulating property of
the vacuum heat insulating panel 13, it is important to use a
substance that is a good insulator for the core material 11 among
constituent materials, reduces the heat-conduction area of the
material to suppress the heat conduction through the substance, and
reduces the gap to suppress heat radiation. As a substance
satisfying the aforementioned conditions, a porous material of
resin, glass, or the like, is preferably used. In particular, a mat
of glass fiber, a board of a resin foam having open cells, or a
molding of resin or inorganic fine particles is used
preferably.
[0021] For example, JP-A-60-71881 has proposed a material obtained
by putting pearlite powder in a synthetic resin bag and
vacuum-packing it into the form of a board. Similarly,
JP-A-60-243471 has proposed a material obtained by putting
pulverized PUF in a synthetic resin bag and vacuum-packing it into
the form of a board. As other proposals, JP-A-60-205164 has
proposed hard polyurethane foam having open cells, JP-A-4-218540
has proposed a plate-like molding which is formed from
thermoplastic urethane resin powder firmly bonded and, JP-A-7-96580
has proposed a board which comprises long glass fiber, fibrillated
resin fiber and inorganic fine powder, each of which is applied as
a core material of the vacuum heat insulation panel.
[0022] Each of the vacuum heat insulation panels, such as those
proposed above, is generally shaped as a board or a substrate
having a thickness in a range from 10 to 20 mm and is typically
incorporated into the wall of the refrigerator. That is, after the
inner box is inserted into the outer box equipped with the vacuum
heat insulation panels stuck thereon so that the inner box is
united with the outer box, a raw material mixture solution of
foaming urethane is injected thereto, foamed and molded to thereby
form a heat insulation wall.
[0023] Accordingly, in the case of a refrigerator, the vacuum heat
insulation panel is usually not stuck on the inner box having an
uneven surface for shelf rests, or the like, but fixed to the outer
box surface by use of an adhesive agent, or the like, so that
foaming urethane to fill the gap in the shell containing the vacuum
heat insulation panels disposed therein is fully packed without any
remaining gap to thereby prevent spoilage of design characteristic
such as deformation, or the like.
[0024] However, in the cases that the packing material has some
fine defect which is larger than expected, a part of the packing
material is destroyed by an external factor or a large amount of
volatile substance remains in or sticks to the core material,
thereby creating a number of possibilities that a desired heat
insulating property cannot be provided.
[0025] As described above, in the heat insulation wall structure of
the conventional heat insulation box body, the vacuum heat
insulation panel is disposed in the shell and the residual space is
filled with urethane foam having closed cells. Therefore, if the
aforementioned failure occurs in the vacuum heat insulation panel,
it is not only very difficult to repair the vacuum heat insulation
panel but also impossible to replace the vacuum heat insulation
panel with a new one. That is, the heat insulation wall is
conventionally formed on the assumption that the whole of a system
such as a heat insulation box body, a refrigerator, or the like,
must be scrapped when the aforementioned failure occurs.
[0026] As a method to enable lowering of the degree of vacuum
caused by the aforementioned possibilities to be repaired, there
has been proposed a heat insulation box body having heat insulation
walls in which all the inside of the shell of the heat insulation
box body is set in a vacuum state. For example, JP-A-57-52783 has
proposed to insert an air-permeable bag containing a powder
substance into the gap between the inner and outer boxes,
JP-A-3-140782 has proposed to put particles of pearlite, or the
like, into the hollow resin shell, and JP-A-2-192580 and
JP-A-7-148752 have proposed to inject foaming heat insulating
material such as foaming urethane with open cells into the shell.
Each of the shells is evacuated with a vacuum pump, or the like,
through a gas exhaust hole provided in a part of the shell to
secure the vacuum state inside the shell of the heat insulation box
body.
[0027] In the conventional heat insulation box body configured so
that all the heat insulation wall is kept in a vacuum state as
described above, it has been found that it is very difficult to
fill the inside of the shell with a powder or granular substance
uniformly and densely when the powder or granular substance is put
in the shell. Accordingly, if the inside of the shell is kept in a
vacuum state, the shell is pressed by atmospheric pressure so as to
be partly or wholly contracted, so that deterioration of design
characteristic may be caused or in some cases, deterioration of
heat insulating property caused by reduction of the wall thickness
may be triggered.
[0028] Further, in filling a heat insulation box body having
inferior filling property such as a large-size refrigerator, or the
like, a larger amount of filling is required than the amount of
filling corresponding to the density for obtaining a strength
required to prevent deformation caused by the atmospheric
pressure.
[0029] Accordingly, there arise disadvantages such as economical
loss, increase of weight, lowering of heat insulating property,
etc.
[0030] Further, in filling the heat insulation box body with
open-cell foaming urethane, communication of bubbles cannot be
sufficiently achieved so that closed cells remain, if bubbles in a
foamed state flow over a short distance from the start point of
foaming, bubbles flow in a state of stable shape after completion
of bubble growth, and so on.
[0031] Further, because foaming gas remaining in bubbles remains in
cells or is adsorbed into a resin constituting cells even in a
portion in which communication of cells is achieved, foaming gas
remains. Accordingly, if this is used as it is, for a structural
material, there arises a disadvantage that not only a long time is
required for evacuation particularly of a large-size full vacuum
heat insulation box body but also a degree of vacuum changes is
lost over the passage of time.
[0032] That is, in accordance with the aforementioned proposals, it
is indispensable to perform troublesome evacuation substantially
periodically by use of a vacuum pump, or the like, or to
incorporate a suction system for the purpose of preventing a drop
in the degree of vacuum due to generation of gas in the shell.
Furthermore, in a state where the inside of the shell is filled
with no gap, a long evacuation time is required because this
structure brings a great disadvantage for sucking remaining gas in
an opposite portion inside the shell to the gas-exhaust hole up to
all open cells through a long distance along open cells by use of a
vacuum pump from a gas-exhaust hole provided in an end portion of
the heat insulation box body such as a refrigerator, or the like,
to thereby perform evacuation to secure a sufficient vacuum state.
Further, during the period when the degree of vacuum drops with the
passage of time, a cooling operation is carried out frequently, so
that electric power is additionally consumed and the temperature of
the inside of the refrigerator becomes unstable to cause a problem
in that the freshness of foods is affected.
[0033] Further, when the full vacuum heat insulation box body
obtained by the conventional production method is to be
disassembled after scrapping so as to recycle parts or members,
some measures are required to prevent scattering of the filling
materials at the time of disassembling or collecting in the former
case of filling powder or granular materials, and it is also
difficult to handle the materials without damage even in the case
of employing a method in which the filling materials are disposed
in a form protected by bags, or the like.
[0034] On the other hand, in the latter case of the full vacuum
heat insulation box body in which a raw-material mixture solution
of foaming urethane is injected into the shell and foamed to
thereby form heat insulation walls, the filled urethane foam firmly
self-adheres to the inner and outer boxes constituting the shell so
as to be nearly inseparable therefrom when the box body is to be
disassembled after scrapping to recycle the members. In the
conventional method therefore, the shell is not separated into
constituent members but the inner and outer boxes and the filled
urethane foam self-adhering thereto are collectively subjected to a
crusher so as to be broken up, and then, the crushed parts are
separated into respective members by use of a separation method
using weight or magnetic characteristic arranged for a subsequent
step to the crusher, so that the outer box is magnetically
attached, the inner box is made to fall down by itself by weight
and the urethane foam is flown off, for example, laterally by use
of wind, or the like. It is however impossible to perfectly
separate the urethane foam self-adhering to the inner and outer
boxes from adhering surfaces. Accordingly, used members cannot be
reused and therefore, recycling of the members is difficult using
the conventional methods.
SUMMARY OF THE INVENTION
[0035] A technical object of the present invention is to entirely
hold the inside of heat insulation walls in a vacuum state as well
as to provide easy evacuation, light-weight and uniform strength,
reduction of remaining gas and prevention of entrance of gas from
the outside, and also to facilitate disassembling after scrapping
of the heat insulation walls so as to simplify recycling of
respective members.
[0036] In order to achieve the above object, according to one
aspect of the present invention, a full vacuum heat insulation box
body in which the inside of its heat insulation walls is filled
with structural materials having continuous pores and kept in a
vacuum state, is constructed such that inner and outer boxes
constituting a shell of the heat insulation box body and the
structural material put between the inner and outer boxes are held
only by close-contact caused by means of a vacuum. With this
configuration, the constituent materials of the box body can be
separated and collected easily when disassembling the box body
after scrapping, without leaving material on the abutting
parts.
[0037] Preferably, the shell of the heat insulation box body has an
uneven surface, and the structural materials abutting on the uneven
surface of the shell include moldings formed of a pulverized resin
foam. With this configuration, a non-filling portion is not
produced between the uneven surface of, for example, the inner box
and the abutting surface of the structural materials, so that flaws
in design characteristic such as surface deformation can be
prevented even in the case where the inside of the shell is kept in
a vacuum.
[0038] Preferably, the structural materials contain parts
comprising grooves or holes for exhausting air and continuous
pores. With this configuration, gas such as air remaining in the
shell can be exhausted easily, resulting in a short time required
for evacuation and a high degree of vacuum secured to improve heat
insulating property.
[0039] Preferably, the structural materials are constituted by a
resin foam having open cells. With this configuration, heat
insulation walls with small heat conduction can be formed, so that
the quantity of leaking heat can be suppressed and heat insulating
properties can be improved.
[0040] Preferably, the structural materials have parts each having
a triangular section, each of the triangular-section parts being
disposed in a middle layer in the direction of wall thickness, or
in a layer abutting an even surface of the shell. With this
configuration, a wedge effect is obtained so that the walls are
never slackened or deformed, and an inferior design characteristic
such as deformation can be prevented.
[0041] Preferably, the parts having a triangular section are formed
of polystyrene foam having open cells. With this configuration,
dust, or the like, is never produced even if surfaces of the parts
are rubbed in handling, moderate flexibility necessary for handling
is provided to improve working efficiency, and a strength tolerant
to the atmospheric pressure and a fine cell shape are provided to
provide both excellent external appearance and heat insulating
property.
[0042] Preferably, the polystyrene foam having open cells has
flattened cells which are spread in a direction perpendicular to
the direction of wall thickness. With this configuration, the
effect of blocking radiation heat in a heat-insulating direction
are improved.
[0043] Preferably, a joint portion between the inner and outer
boxes is constituted by a groove of a predetermined depth formed by
bending one of the boxes and is filled with a liquid substance
having an adhesive sealing function and an end side portion formed
in the other box so as to be able to be inserted into a deep
portion of the groove. Joining and sealing of the joint portion are
performed by the liquid substance by utilizing mutual attraction
force produced at the time of evacuation of the shell. With this
configuration, the inner and outer boxes can operate as a piston.
Structural materials can be pressed from the outside by the inner
and outer boxes, so that the degree of close-contact between the
structural materials can be enhanced on the basis of a vacuum.
[0044] Preferably, an opening portion, which is later closed with a
plate member, for inserting the structural materials is provided in
the outer box, a joint portion between the outer box and the plate
member is constituted by a groove of a predetermined depth formed
by bending one of the outer box and the plate member and filled
with a liquid substance having an adhesive sealing function and an
end side portion formed in the other of them so as to be able to be
inserted into a deep portion of the groove. Joining and sealing of
the joint portion are performed by the liquid substance by
utilizing mutual attraction force produced at the time of
evacuation of the shell. With this configuration, the plate member
can operate as a piston. Structural materials disposed in the
opening portion can be pressed from the back side by the plate
member, so that the degree of close-contact between the structural
materials can be enhanced on the basis of a vacuum.
[0045] Preferably, the groove is formed by bending an end edge
portion inward in a zigzag arrangement. With this configuration, a
gap continuous along the whole circumference of the joint portion
can be formed between a base end piece of the zigzag bent portion
and the outer circumferential surface of the outer box and the
distance from the outer box to the structural materials can be made
longer. Accordingly, at the time of disassembling after scrapping
an opposite portion of the outer circumferential surface of the
outer box to the base end piece of the zigzag bent portion can be
cut easily without keeping cutting depth accurate. Accordingly, air
can be introduced inside and the shell can be opened easily, so
that respective structural materials can be taken out without
damage and collected.
[0046] Preferably, the groove has a wide reservoir portion at its
upper portion for reserving a liquid substance to prevent it from
overflowing from the groove. With this configuration, the shell can
be filled with an amount of adhesive agent sufficient to seal and
the adhesive agent can be also prevented from overflowing to the
outside, so as to improve workability and prevent both staining of
a core material with the adhesive agent and adhesion of structural
materials to the shell by the adhesive agent.
[0047] Preferably, the liquid substance is constituted by an
adhesive agent containing particles or powder of a metal oxide or a
metal nitride With this configuration, permeation of various kinds
of gasses, water vapors, etc. can be suppressed, so that
degradation of heat insulating property caused by vacuum loss over
time can be prevented.
[0048] Preferably, a mark or indicia is provided in the outer
circumferential surface of the zigzag bent portion. With this
configuration, a portion to be cut without damage of structural
materials to be collected can be easily found at the time of
disassembly.
[0049] According to another aspect of the present invention, a
method for producing a full vacuum heat insulation box body
includes integrating an inner box and an outer box onto a first
shell which is opened in an open bottom surface of the outer box,
inserting a first structural material having continuous pores and a
triangular section into the inside of a space formed between the
inner and outer boxes constituting the first shell through the
opening of the first shell, by inserting a bottom side portion of
the first structural material ahead, inserting a second structural
material having continuous pores and a triangular section into the
space through the opening of the first shell by inserting a vertex
portion of the second structural material ahead to thereby fill the
inside of the room of the first shell, blocking the opening of the
first shell with a third structural material having continuous
pores and a shape like a flat plate, enclosing the third structural
material with a plate member from the outside to seal the joint
portion between the plate member and the first shell to thereby
form a second shell which is fully closed, and evacuating the
second shell. With this method, a heat insulation box body, in
which the inside of the shell is kept in a vacuum and its external
appearance is never deformed, can be obtained easily.
[0050] Preferably, a structural material to be brought into contact
with an uneven surface of the shell is first inserted and a
triangular sectional structural material having no uneven surface
is finally inserted with a vertex portion thereof inserted ahead,
so that the room of the first shell is filled with the structural
materials. With this configuration, structural materials abut on
the shell without any gap, so that tight wall surfaces can be
obtained easily.
[0051] Preferably, evacuation of the second shell is performed
under the condition that the inner and outer boxes and the
structural materials put between the inner and outer boxes are not
fixed by an adhesive agent, or the like. With this configuration,
structural materials can be disposed of easily, so that working
efficiency is improved and the adhesive agent which is a cause of
lowering of the degree of vacuum in the shell can be eliminated to
suppress loss of vacuum.
[0052] Preferably, at least one member of the first shell and the
plate member for covering the opening of the first shell is bent at
the joint portion to form a groove of a predetermined depth, the
groove is filled with a liquid substance formed of an adhesive
agent containing particles or powder of a metal oxide or a metal
nitride, and after the other member is inserted into the groove
filled with the liquid substance, the liquid substance is
solidified while evacuating the fully closed second shell to
thereby perform both joining and sealing at the joint portion. With
this configuration, positioning can be made easily and the joint
portion can be sealed securely.
[0053] According to a further aspect of the present invention, a
method for disassembling a full vacuum heat insulation box body
having a shell constituted by inner and outer boxes, and structural
materials disposed in the shell, the inner and outer boxes and the
structural materials being merely fixed by close-contact caused by
means of a vacuum includes cutting a surface of the shell to
thereby introduce air into the inside of the shell so as to allow
the inside state of the shell to return to an atmospheric pressure
state, then separating the materials of the shell and the
structural materials from each other. With this method, the inner
and outer boxes and structural materials can be separated from each
other by a simple operation of destroying the vacuum state.
Accordingly, respective members can be collected and recycled
easily.
[0054] Preferably, a joint portion between the inner and outer
boxes is constituted by a groove formed by bending an end edge
portion of one member of the boxes inward in a zigzag and filled
with a liquid substance, and an end side portion formed in the
other member of the boxes so as to be able to be inserted into a
deep portion of the groove. Also, preferably, cutting of the shell
surface is performed by providing a notch in an outer surface of
the one member having the zigzag bent portion along a position
corresponding to the zigzag bent portion, and the inner and outer
boxes are then separated from each other and the materials of the
shell and the structural materials are recovered. With this
configuration, as the cut portion of the shell is apart from a
structural material is so as to have a gap between them, this
portion can be cut easily without keeping cutting depth of the
notch accurate and the shell can be opened. Accordingly, respective
structural materials in the inside of the shell can be taken out,
collected and recycled without damage.
[0055] Preferably, the outer box has an opening portion used for
insertion of structural materials which is closed with a plate
member, and a joint portion between the outer box and the plate
member constituted by a groove formed by bending an end edge
portion of one member of the outer box and the plate member inward
in a zigzag and filled with a liquid substance, and an end side
portion formed in the other member of them so as to be able to be
inserted into a deep portion of the groove. Cutting of the shell
surface is performed by providing a notch in an outer
circumferential surface of the member having the zigzag bent
portion along a position corresponding to the zigzag bent portion,
and the outer box and the plate member are then separated from each
other and the materials of the shell and the structural materials
are recovered. With this configuration, since the cut portion of
the shell is separate from a structural material so as to have a
gap between them, this portion can be cut easily without keeping
cutting depth of the notch accurate, and the shell can be opened.
Accordingly, respective structural materials in the inside of the
shell can be taken out, collected and recycled easily without
damage.
BRIEF DESCRIPTION OF THE DRAWINGS
[0056] FIG. 1 is a sectional view showing a full vacuum heat
insulation box body according to a first embodiment of the present
invention in the state where the full vacuum heat insulation box
body is laid on its side;
[0057] FIG. 2 is an enlarged sectional view showing a shell
constituent member joint portion which is a main part of the full
vacuum heat insulation box body according to the first
embodiment;
[0058] FIG. 3 is a sectional view taken along the line A-A in FIG.
1;
[0059] FIG. 4 is a flow chart showing a method for producing the
full vacuum heat insulation box body according to the first
embodiment;
[0060] FIG. 5 is a perspective view showing a refrigerator using
the full vacuum heat insulation box body according to the first
embodiment in the state where a door portion is removed;
[0061] FIG. 6 is a sectional view showing a full vacuum heat
insulation box body according to a second embodiment of the present
invention in the state where the full vacuum heat insulation box
body is laid on its side;
[0062] FIG. 7 is an enlarged sectional view showing the portion B
in FIG. 6 before joining;
[0063] FIG. 8 is a perspective view showing the whole of a grooved
structural material in the full vacuum heat insulation box body
according to the second embodiment:
[0064] FIG. 9 is a perspective view showing a refrigerator using
the full vacuum heat insulation box body according to a fourth
embodiment of the present invention in the state where a door
portion is removed;
[0065] FIG. 10 is an explanatory view showing a section taken along
the line C-C in FIG. 9;
[0066] FIG. 11 is an explanatory view showing a section taken along
the line D-D in FIG. 9;
[0067] FIG. 12 is a flow chart showing a method for producing the
full vacuum heat insulation box body according to the fourth
embodiment;
[0068] FIG. 13 is an explanatory view showing a method for
disassembling a full vacuum heat insulation box body according to a
fifth embodiment of the present invention;
[0069] FIG. 14 is a perspective view showing the full vacuum heat
insulation box body according to the fifth embodiment;
[0070] FIG. 15 is an enlarged sectional view showing a shell
constituent member joint portion which is a main part of the full
vacuum heat insulation box body according to the fifth
embodiment;
[0071] FIG. 16 is a flow chart showing steps for producing a
conventional refrigerator.
[0072] FIG. 17 is an explanatory view showing a foaming urethane
injection step in the conventional refrigerator producing
process;
[0073] FIG. 18 is an explanatory view showing heat insulating
property in various kinds of heat insulating materials;
[0074] FIG. 19 is a sectional view showing the structure of a
vacuum heat insulation panel; and
[0075] FIG. 20 is a sectional view showing the configuration of a
vacuum panel making machine.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0076] Embodiment 1
[0077] The present invention will be described below on the basis
of an embodiment as shown in the drawings.
[0078] As shown in FIG. 1, the full vacuum heat insulation box body
in this embodiment is applied to a chest freezer and so designed
that inner and outer boxes 22 and 23 which constitute a shell 21 of
the heat insulation box body and structural materials with
continuous pores 24, 25, 26 and 35 which are interposed between the
inner and outer boxes 22 and 23 and are preserved only by close
contact based on a vacuum.
[0079] In more detail, a box-like member formed by stainless steel
thin plates welded or jointed with bond is used herein as the inner
box 22 constituting an interior surface of the shell 21. The
material of this member is selected taking such conditions into
consideration as suppression of lowering of heat insulating
property caused by propagation of heat from the outer box 23
constituting an exterior surface of the shell 21, a gas barrier
property for suppressing infiltration of external gas through inner
box surfaces, and tolerance to shock caused by falling of various
kinds of frozen and preserved food.
[0080] Further, a four-side bent member formed of a colored steel
plate capable of bending is used herein as an outer box 23
constituting the exterior surface of the shell 21, preferably as a
box-shaped member in which side wall surfaces are integrated.
Incidentally, one of circumferential side surfaces (four surfaces)
of each of the inner and outer boxes 22 and 23 is not shown in
Figures for the sake of convenience in explanation.
[0081] Among the structural materials 24,25, 26 and 35, structural
materials 24, 25 and 35 inserted inside the respective side walls
of the shell 21 are composed of parts 24a and 24b, 25a and 25b, and
35a and 35b, respectively, each of which exhibits a triangular
sectional structure to produce a wedge effect. Among the parts 24a,
24b, 25a, 25b, 35a and 35b, the parts 24a, 25a and 35a disposed on
the outer sides in the inside of the side walls are set to be
longer than parts 24b, 25b and 35b disposed on the inner sides as
shown in FIG. 1 so that the vertex ends of the outer parts 24a, 25a
and 35a are protruded from the base ends of the inner parts 24b,
25b and 35b to the shell bottom surface side when the parts are
assembled.
[0082] Further, a thickness of a rectangular flat plate-like
structural material 26 finally inserted in the bottom wall portion
of the shell 21 is so set that the structural material 26 is
slightly protruded outward from the opening surface of the bottom
wall. Furthermore, inclined surfaces 26a corresponding to the
inclinations of the outer parts 24a, 25a and 35a of the side wall
structural materials are formed in the circumferential surfaces of
the structural material 26 so that the inclined surfaces 26a abut
on the inner surfaces of the protruded portions of the outer parts
24a, 25a and 35a respectively. In addition, outer circumferential
portions 26b of the inner surface of the structural material 26 are
designed to abut on the base end surfaces of the inner parts 24b,
25b and 35b, respectively, of the side wall structural
materials.
[0083] Each of these structural materials 24, 25, 26 and 35 is
produced by cutting a large slab formed of a resin foam, such as
urethane foam, or the like, having open cells. This is because,
since the chest freezer is designed without an uneven portion in
the surfaces of the inner and outer boxes 22 and 23, and the
structural materials can abut on the inner and outer boxes 22 and
23 having simple shapes formed from planes, insertion of structural
materials obtained by cutting a large slab formed of a resin foam,
such as urethane foam, or the like, having open cells is
inexpensive and materials having various adaptive properties, such
as resistance against fragility enough to prevent generation of
dust or the like in the case of rubbing of surfaces at the time of
handling, strength enough to endure atmospheric pressure, moderate
flexibility necessary for handling, excellent heat insulating
property created on the basis of the shape of a fine cell effective
for radiation heat insulation, the low density needed to suppress
heat conduction in solid matters, etc. are secured easily.
[0084] Incidentally, the bottom surface portion of the shell 21
constituting a surface opposite to the opening portion of the chest
freezer is opened initially so that the respective structural
materials 24, 25, 26 and 35 can be inserted. After the respective
structural materials 24, 25, 26 and 35 are inserted, the opening of
the bottom surface is closed with a plate member 27 from the
outside and the joint portion of the plate member 27 is sealed to
thereby form a fully closed box body. Further, evacuation is
performed through a vacuum valve 28 fitted to the plate member 27
by welding. As a result, the shell 21 constituted by the inner and
outer boxes 22 and 23 and the plate member 27 comes into contact
with the respective structural materials 24, 25, 26 and 35
interposed between the constituent members and the contact state is
thus kept. In this occasion, a joint portion 29 between the outer
box 23 and the plate member 27 is constituted by a groove 32 of a
predetermined depth which is formed by bending an end edge portion
of the outer box 23 inward in zigzag, as shown in FIG. 2, so that
it is filled with a liquid adhesive agent 31 having a sealing
function, and an end side portion 33 so formed in the plate member
27 that it can be inserted deeply into the groove 32. The outer box
23 and the plate member 27 are joined to each other at the joint
portion 29 by use of mutual attraction force caused by negative
pressure produced at the time of evacuation of the inside of the
shell and this state is kept until the adhesive agent 31 in the
groove 32 is hardened, so that the outer box 23 and the plate
member 27 are joined and sealed. In this manner, the plate member
27 is made to operate as a piston by use of the negative pressure
caused by the evacuation at the time of jointing, so that the
structural material 26 disposed in the opening of the bottom
surface can be pressed by the plate member 27 from the back surface
side. Further, the inner parts 24b, 25b and 35b of the structural
materials 24, 25 and 35 inserted in the side wall portion of the
shell 21 are pressed by the pressed structural material 26, so that
the wedge effect can be brought.
[0085] Incidentally, an adhesive agent comprising a mixture of a
liquid resin such as an epoxy resin and ceramics containing metal
oxide or metal nitride particles or powder is used as the adhesive
agent 31. By this, contraction accompanying the effect of the resin
constituting the adhesive agent 31 is suppressed to thereby prevent
occurrence of defects of passing through the adhesive portion and
prevent transmission of various kinds of gases.
[0086] A wide reservoir portion 34 for reserving the adhesive agent
31 is provided in the upper portion of the groove 32 by sheet
bending as shown in FIG. 2, so that the adhesive agent 31 charged
in the groove 32 is prevented from overflowing and leaking when the
end side portion 33 of the plate member 27 is inserted. By this
configuration, the end side portion 33 of the plate member 27 can
be received in the groove 32 easily, so that the plate member 27
can be fixed to a fixed position of the outer box 23. Accordingly,
the adhesive agent 31, which may be excessive but is never
insufficient in quantity, can be charged, so that the sealing
function for blocking entrance of the outside air is enhanced. That
is, by immersing the joint portion between the outer box 23 and the
plate member 27 in the resin charged in the groove 32, a fully
sealed shell structure is obtained, so that defects such as
incomplete joining and communicating portions, etc. can be
eliminated. Incidentally, this joint structure is employed not only
in the joint portion between the outer box 23 and the plate member
27 but also in a joint portion (not shown) between the inner and
outer boxes 22 and 23. By this configuration, efficiency in joining
work and the degree of sealing of the heat insulation box body as a
whole can be enhanced, so that high reliability is obtained.
[0087] In this manner, the end edge portion of the outer box 23 is
bent inward in a zigzag configuration to thereby form the groove
32, and an extreme end side piece 23a of the zigzag bent portion is
bent so as to form the wide reservoir portion 34 for receiving the
adhesive agent 31. Accordingly, as shown in FIG. 2, a gap G, which
is continuous on the whole circumference of the joint portion 29,
is formed between a base end side piece 23b of the zigzag bent
portion and a portion 23c in the outer circumferential surface of
the outer box 23 located opposite to the base end side piece 23b of
the zigzag bent portion. This gap G is never fixed because the gap
G is disposed outside the groove 32 and inside the shell 21 so that
it is not filled with the adhesive agent 31. Accordingly, by
cutting the zigzag bent portion on the outer circumferential
surface of the outer box 23, that is, by cutting the portion 23c
opposite to the base end side piece 23b at the time of
disassembling, the air is introduced into the shell 21 so that the
inside of the shell 21 can be returned to an atmospheric pressure
state. The shell 21 can be thereby opened easily to take out the
structural materials 24, 25, 26 and 35.
[0088] Further, as shown in FIG. 3, in each of the corner portions
of the side walls, the cut shapes of the end edges of the
structural materials including the taper of an adjacent triangular
structural material are secured to make close contact to each
other, and the end edges of the structural materials are combined
in tiers and a labyrinthine form. In each of the corner portions of
the side walls, adjacent structural materials can be thereby made
to contact closely to each other, so that the quantity of leaking
heat can be greatly reduced even on condition that of the same gap
size is formed in butting.
[0089] A method for producing a full vacuum heat insulation box
body configured as described above will be described below on the
basis of the flow chart of FIG. 4 with reference to FIGS. 1 through
3. First, stainless steel thin plates are joined by means of
welding or adhesive bonding so as to be shaped like a box to
thereby obtain an inner box 22 constituting an interior surface of
a shell of the heat insulation box body (step 111).
[0090] Then, a colored steel plate is bent to form a 4-side
pipe-like bent member to thereby obtain an outer box 23
constituting an exterior surface of the shell of the heat
insulation box body. After the inner box 22 is inserted in the
outer box 23, the inner and outer boxes 22 and 23 are joined to
each other in the joint portions to thereby form a first shell in
which the bottom surface of the outer box is opened (step 112).
With respect to the work of joining the outer and inner boxes 23
and 22, the mode of the joint portions is the same as in the joint
portion between the outer box 23 and the plate member 27 explained
in FIG. 2. A groove provided in one of the outer and inner boxes 23
and 22 is filled with an adhesive agent composed as described
above. After an end side portion provided in the other box is
inserted in the groove filled with the adhesive agent, this state
is kept until the adhesive agent in the groove is hardened. Thus,
both joining and sealing between the outer and inner boxes 23 and
22 are performed. In this occasion, the groove can be entirely
filled with the adhesive agent if a larger amount of the adhesive
agent is provided near the center of each groove so that the
adhesive agent is made to flow by inserting the end side portion of
the other box. This is preferable from the point of view of
obtaining uniform and faultless sealing. As described above, into
the resin in the groove formed in one of the outer and inner boxes
23 and 22 at the joint portion therebetween, the end side portion
provided in the other box is immersed to thereby make it possible
to eliminate defects such as incomplete joined portions and
communicating portions, etc. Thus, a shell structure in which the
joint portion is fully sealed is obtained. As a result, the defect
portion such as a hole passing through the shell, etc. is reduced
to secure a sealing structure having an excellent reliability in
blocking gas such as air, water vapor, etc. entering the heat
insulation box body from the outside.
[0091] Then, a structural material for making the shell endure
atmospheric pressure so as not to be deformed at the time of
evacuation in the posterior stage, is prepared and inserted in the
first shell (step 113). The preparation of the structural material
is as follows. First, a foaming resin such as foaming urethane, or
the like, having open cells is foamed to thereby prepare a large
slab-like foamed article. The foamed article is cut to obtain
first, second and third structural materials, that is, parts 24a,
25a and 35a which are first structural materials each exhibiting a
triangular sectional structure, parts 24b, 25b and 35b which are
second structural materials each exhibiting a triangular sectional
structure, and a structural material 26 which is a third structural
material shaped like a flat plate inserted in the bottom wall
portion. The structural materials thus obtained are inserted in
gaps between the outer and inner boxes 23 and 22 through the
opening of the first shell.
[0092] Insertion of the structural materials into the first shell
is carried out as follows. First, the first structural materials
each having a triangular section, that is, parts 24a, 25a and 35a
are inserted in the inside of respective side walls (4 sides)
through the opening of the first shell so as to be preceded by end
sides which are respective base portions of the triangles. Then,
the second structural materials each having a triangular section,
that is, parts 24b, 25b and 35b are inserted in the side walls (4
sides) through the opening of the first shell so as to be preceded
by vertex portions of the triangles. By this configuration, the
inside of the circumferential side walls of the first shell is
filled. Then, the opening of the first shell is blocked by the
third structural material 26 shaped like a flat plate.
[0093] When insertion of all the structural materials into the
first shell is completed, the third structural material 26 is
enclosed by the plate member 27 from the outside to seal the joint
portion between the plate member 27 and the first shell with the
adhesive agent 31 to thereby form a fully closed second shell (step
114). The second shell is evacuated through the vacuum valve 28
attached to the plate member 27 (step 115).
[0094] The evacuation is started under the condition that the
structural materials 24, 25, 26 and 35 put between the inner and
outer boxes 22 and 23 are not fixed by means of an adhesive agent,
or the like, and before the adhesive agent 31 in the groove 32 in
the joint portion 29 between the outer box 23 and the plate member
27 is hardened. The evacuation is continued until the adhesive
agent 31 is hardened. Accordingly, when the evacuation is started,
the plate member 27 is pulled toward the inside of the second shell
on the basis of the pressure difference between the air pressure of
the inside of the second shell and the air pressure of the outside
thereof As a result, the plate member 27 functions as a piston for
pressing the third structural material 26 from the bottom surface
side. The structural materials 24, 25 and 35 inserted in the
circumferential side wall portions of the shell 21, especially
parts 24b, 25b and 35b as the second structural materials are
pressed by the third structural material 26 pressed by the plate
member 27, so that the wedge effect acts. As a result, there is no
slack in the direction of the thickness of each wall. so that the
shell can be substantially entirely filled without any gap.
Accordingly, even in the case where the inside of the shell reaches
a vacuum state. the shell is never deformed, i.e., cavitated, by
the atmospheric pressure. Thus, an excellent external appearance
state can be kept. After the adhesive agent 31 is hardened, the
inner and outer boxes 22 and 23 and the respective structural
materials 24, 25, 26 and 35 are kept only by close contact based on
a vacuum to thereby obtain a full vacuum heat insulation box body
which is light in weight and has a uniform strength characteristic
(step 116). Although the degree of vacuum in the shell varies in
accordance with the kinds of the structural materials used,
sufficient heat insulating property can be provided by keeping the
degree of vacuum higher than 10.degree. torr, preferably higher
than 10.degree. torr.
[0095] In this manner, the inner and outer boxes 22 and 23 and the
respective structural materials 24, 25, 26 and 35 are brought into
close contact with one another by use of the negative pressure
based on a vacuum without use of any adhesive agent. Accordingly,
the problem of vaporization, scattering, etc. of water and
low-molecular substances contained in the adhesive agent material,
into the shell under a vacuum state brought about by use of some
adhesive agent is eliminated, so that degradation of heat
insulating property is prevented. Further, although the respective
structural materials 24, 25, 26 and 35 are not stuck to the shell,
they fill gaps in the shell. Accordingly, their recomotion, or the
like, is not caused by vibration in handling in production and use
and these arises no problem that the external appearance is
spoiled.
[0096] Furthermore, recovery at the time of recycling is
simplified. That is, in the case of a conventional heat insulation
box body such as a refrigerator, or the like, closed-cell urethane
foam as a structural material is firmly stuck to an ABS resin
vacuum-molding and a bent article of a coated steel plate which are
shell materials. Accordingly, in the conventional case, a great
deal of labor is required for separating these materials from each
other and the urethane foam cannot be entirely removed even if
these materials are separated. In the full vacuum heat insulation
box body according to the present invention, however, the shell and
the structural materials are fixed to one another in a state where
they are merely pressed by the atmospheric pressure so as to be in
close-contact with each other. Accordingly, if the vacuum state is
broken, the inner and outer boxes 22 and 23 and the respective
structural materials 24, 25, 26 and 35 can be peeled off and
separated easily.
[0097] FIG. 5 shows a refrigerator produced by the same method as
used for producing the aforementioned chest freezer. In the case of
the chest freezer, an opening for insertion of the respective
structural materials is provided in the bottom surface, whereas in
the case of this refrigerator, an opening initially formed for
insertion of the structural materials in the inside of the opposite
side walls, a ceiling, a floor and a middle wall of the
refrigerator is set on the back surface. According to this
structure, structural material parts of a triangular sectional
structure inserted in the upper, lower, left, right and middle
walls are pressed at the time of evacuation by a rectangular flat
plate-like structural material finally inserted in the back surface
portion and a plate member for enclosing the rectangular flat
plate-like structural material, so that the wedge effect can be
brought about. As a result, no slack or cavitation is caused in the
direction of the thickness of each wall, so that the shell can be
substantially entirely filled without any gap. Accordingly, the
shell is never deformed even if the inside of the shell reaches a
vacuum state. Thus, a refrigerator having its external appearance
kept excellent is obtained. Incidentally, it is a matter of course
that the evacuation is performed at the time of jointing the joint
portion between the outer box 23 and a back plate member (not
shown) in a state where the refrigerator is laid on its side, and
that the evacuation is started before hardening of the adhesive
agent in the groove in the joint portion and continued until the
adhesive agent is hardened.
[0098] When the present invention is applied to a large-scale full
vacuum heat insulation box body such as a refrigerator, or the
like, as described above, the inner and outer boxes 22 and 23 and
the respective structural materials can be peeled and separated
from one another easily so that efficiency in recovery at the time
of scrapping can be enhanced greatly. That is, in the conventional
heat insulation box body such as a refrigerator, or the like,
closed-cell urethane foam as a structural material is firmly stuck
to an ABS resin vacuum-molding and a bent article of a coated steel
plate as shell materials Accordingly, in the conventional case, a
great deal of labor is required for separating these materials from
each other and urethane foam cannot be entirely removed even if
these materials are separated. In the full vacuum heat insulation
box body according to the present embodiment, however, the shell
and the structural materials are fixed to one another in a state
where they are merely pressed by the atmospheric pressure so as to
be in close-contact with each other. Accordingly, when the vacuum
state is broken, they can be peeled off and separated easily.
[0099] Embodiment 2
[0100] Referring now to FIG. 6 through FIG. 8, with respect to the
inside of the circumferential side walls, only left and right walls
are shown and explained.
[0101] In this embodiment, the full vacuum heat insulation box body
is applied to a chest freezer. Parts of structural materials 24 and
25 inserted in side walls of a shell 21 constituted by outer and
inner boxes 23 and 22 and a plate member 27, that is, parts 24a,
24b, 25a and 25b each produced by cutting a large slab-like foamed
article formed from a foaming resin such as foaming urethane, or
the like, having open cells and exhibiting a triangular sectional
structure are so designed that a plurality of grooves 41 extending
in the lengthwise direction as shown in FIG. 8 are provided in
parallel on an inclined surfaces of either one of the inner part
24a and the outer part 24b, or 25a and 25b. The grooves are herein
provided on the inclined surfaces of the inner parts 24b and 25b
disposed on the inner box 22 side in this embodiment. The inner
parts 24b and 25b are combined with the outer parts 24a and 25a
disposed on the outer box 23 side so that the surfaces of the inner
parts 24b and 25b having the grooves 41 formed thereon come face to
face with the surfaces of the outer parts 24a and 25a. Although the
labyrinthine structure of the side edge portions of the structural
materials 24 and 25 is not shown, it is a matter of course that
adjacent structural materials are combined with each other in tiers
at each of the corner portions of the side walls.
[0102] In more detail, because wide grooves 41 in the parts 24b and
25b are easily deformed by atmospheric pressure, it is preferable
to provide a large number of grooves each of which is rather narrow
and deep to an extent not to constitute an obstacle in handling.
Here is shown the case where grooves each having a width of 3 mm
and a depth of 5 mm are provided at intervals of a pitch of 50 mm.
The other conditions such as the configuration of the joint portion
between the outer and inner boxes 23 and 22 and the procedure of
assembling the respective members are the same as in the first
embodiment described previously.
[0103] Also in this embodiment, by performing evacuation through a
vacuum valve 28 attached to the plate member 27 by means of welding
42, the wedge effect of the parts 24b and 25b each having a
triangular section is brought so that the shell 21 constituted by
the inner and outer boxes 22 and 23 and the plate member 27 is
brought into close contact with the structural materials 24, 25 and
26 put therebetween and that the close contact state is kept. In
this occasion, it is necessary that the gasses in a portion located
farthest from the vacuum valve 28 (gasses adsorbed on the surface
of the shell or remaining in pores of the structural materials) are
also sucked and exhausted through the vacuum valve 28. In this
embodiment, as the grooves 41 serving as gas exhaust passages are
present on the mating surface between the triangular sectional
parts of the structural materials 24 and 25 inserted in the inside
of the respective side walls, gasses, or the like, in pores of the
respective structural materials are exhausted through the grooves
41 after moved into the grooves 41. Accordingly, efficiency
evacuation is enhanced so that a sufficient vacuum state can be
secured up to the inside of continuous pores of the structural
materials located opposite to the vacuum valve 28.
[0104] For example, in the case of the heat insulation box body of
a refrigerator having an internal volume of 400 L, a distance not
smaller than 1 m is required as the distance from a position of
evacuation to the farthest end of the structural materials even if
evacuation is performed from any position. Accordingly, a long time
is required to exhaust gasses such as air, etc. remaining in pores
of the structural materials located at far ends, only through the
pores of the structural materials. According to this embodiment
with gas-exhaust grooves 41 on the contrary, gasses can be
exhausted to the outside of the shell easily after they are moved
into the gas-exhaust grooves 41 so that the time required for
exhausting gasses is shortened greatly.
[0105] Embodiment 3
[0106] In the full vacuum heat insulation box body according to
this embodiment, the present invention is applied to the same chest
freezer as in the first embodiment. Among the structural materials
24, 25, 26 and 35 inserted in the inside of the shell 21
constituted by the outer and inner boxes 23 and 22 and the plate
member 27 in FIG. 1, at least parts 24a, 24b, 25a, 25b, 35a and 35b
exhibiting a triangular sectional structure are formed of
polystyrene foam having open cells. Incidentally, FIGS. 1, 2, 3 and
7 explained previously are referred to in the following
description.
[0107] In this embodiment, a resin foam having open cells is used
as a material for the structural materials 24, 25, 26 and 35. As a
material, polystyrene foam having small cell size are used as well
as urethane foam. With respect to a method for producing
polystyrene foam having open cells, as described in WO96/07942
(JP-A-8-503720, Japanese Patent Application No. Hei-6-509062) and
WO96/16876 (JP-A-8-505895, Japanese Patent Application No.
Hei-6-517001), first, polystyrene having a mean molecular weight of
2.times.10.sup.5 is subjected to extrusion mixing, foaming and
quenching by suitable use of carbon dioxide gas which is a main
foaming agent, and an auxiliary foaming agent such as HFC-134a
(1,1,1,2-tetrafluoroethane), HFC-152a (1,1-difluoroethane), etc.,
so that polystyrene foam having the open cell content near to 100%
and a small cell size.
[0108] In this occasion, the cells can be flattened easily by
addition of compression stress so as to be spread in a direction
perpendicular to the direction of thickness because the temperature
of the inside of the obtained extrusion molding having the open
cells is kept sufficiently in a value lower than the melting point
and higher than the heat deformation point. In order to remove the
stress produced in the resin which is involved in flattening of the
cells, the temperature is kept in the compressed state to perform
annealing and then the molding is cooled to a temperature lower
than the heat deformation point, preferably lower than the glass
transition point. Among the structural materials 24, 25, 26 and 35,
structural materials 24, 25 and 35 inserted in the inside of the
respective side walls of the shell 21 are cut out from the thus
obtained molding block into a triangular sectional structure which
brings about the wedge effect. Further, in the structural materials
24, 25 and 35, parts 24a, 25a and 35a disposed on the outer side
inside the side walls are so cut out as to be longer than inner
parts 24b, 25b and 35b as shown in FIG. 1 so that the vertex side
ends of the parts 24a, 25a and 35a are protruded toward the bottom
surface side of the shell from the base sides of the inner parts
24b, 25b and 35b respectively at the time of assembling. Thus,
processed parts each having a desired size and a desired shape are
obtained.
[0109] Incidentally, the process of flattening cells may be
performed after the parts 24a, 24b, 25a, 25b, 35a and 35b each
exhibiting a triangular sectional structure are cut out from the
extrusion molding block. That is, there may be used a method in
which, after processed parts each having a desired size and a
desired shape are obtained from the block-like extrusion molding
block, the processed parts are pressed so that cells are flattened
so as to be spread in a direction perpendicular to the direction of
the thickness, and then the processed parts are annealed if
necessary.
[0110] With respect to the processed parts of polystyrene foam
having open cells, dust, or the like, is hardly produced even if
the surface of polystyrene foam is rubbed in handling, and
polystyrene foam is excellent both in strength tolerant to
atmospheric pressure and in moderate flexibility necessary for
handling, compared with urethane foam having open cells as used in
the aforementioned first and second embodiments. Furthermore, not
only the shape of a fine cell effective for radiation heat
insulation is provided but also an effect of blocking off radiation
heat in the heat insulating direction is enhanced by processing
cells flatly so as to be spread in a direction perpendicular to the
direction of the thickness. Accordingly, the processed parts of
polystyrene foam have various adaptive properties such as excellent
heat insulating property, etc. brought by these effects.
[0111] The thus obtained processed parts of polystyrene foam having
open cells are put between the inner box 99 which is formed like a
box of stainless steel thin plates and which constitutes an
interior surface, and the outer box 23 which is formed as a 4-side
bent article of a colored steel plate and which constitutes an
exterior surface. Then, a rectangular flat plate-like structural
material 26 which has such a thickness that the material 26 is
slightly protruded outward from the opening surface of the bottom
portion of the shell 21 and which has inclined circumferential
surfaces 26a corresponding to inclined surfaces of the outer parts
24a, 25a and 35a of the side wall structural materials is inserted
in the bottom wall portion of the shell 21 so that the inclined
circumferential surfaces 26a are made to abut on the inner surfaces
of the protrusion portions of the outer parts 24a, 25a and 35a, and
further, outer circumferential portions 26b of the inner surface of
the structural material 26 are made to abut on the base end
surfaces of the inner parts 24b, 25b and 35b of the side wall
structural materials. Further, the end side portions 33 of the
plate member 27 covering the bottom wall are inserted in and
engaged with the grooves 32 of a predetermined depth formed by
bending the end edge portions of the outer box 23 inward in zigzag
as shown in FIG. 2 and filled with the adhesive agent 31 of a
liquid matter having an adhesive sealing function.
[0112] Then, evacuation is performed through the vacuum valve 28
attached to the plate member 27 by means of welding, so that the
shell 21 constituted by the inner and outer boxes 22 and 23 and the
plate member 27 is brought in close contact with the respective
structural materials 24,25,26 and 35 inserted therebetween. At the
same time, the outer box 23 and the plate member 27 are strongly
engaged with each other at the joint portion 29 by use of mutual
attraction force based on negative pressure produced at the time of
evacuation of the inside of the shell, and this state is kept until
the adhesive agent 31 in the grooves 32 has hardened, so that
jointing and sealing between the outer box 23 and the plate member
27 are performed. Although the labyrinthine structure of the side
edge portions of the structural materials 24 and 25 is not shown
here, it is a matter of course that adjacent structural materials
are combined with each other in tiers at each of the corner
portions of the side walls.
[0113] Results of evaluation of heat insulating property based on
the quantity of leaking heat and design characteristic based on the
smoothness of the wall surface of the shell in comparison between
test examples 1, 2 and 3 and comparative examples 1 and 2 will be
described below in order to confirm the heat insulating effect of
the full vacuum heat insulation box body according to the
aforementioned first, second and third embodiments.
TEST EXAMPLES 1, 2 AND 3
[0114] For the use of a chest freezer having an internal volume of
280 L, the following test examples 1 through 3 were prepared by the
producing method explained in the first embodiment. That is, a full
vacuum heat insulation box body (test example 1) according to the
first embodiment was formed by using structural materials with no
gas-exhaust groove which were formed by cutting a slab of urethane
foam having open cells and processing the cut out pieces; another
full vacuum heat insulation box body (test example 2) according to
the second embodiment was formed by using structural materials
which were formed by providing each structural material according
to the test example 1 with grooves each having a width of 3 mm and
a depth of 5 mm, arranged at intervals of a pitch of 50 mm; and a
further full vacuum heat insulation box body (test example 3)
according to the third embodiment was formed by using structural
materials formed through steps of pressing a slab of polystyrene
foam having open cells so as to make the cells flat to spread in a
direction perpendicular to the direction of the thickness,
annealing the slab if necessary, and cutting pieces out of the slab
and processing them.
COMPARATIVE EXAMPLE 1
[0115] The shell obtained by the method of fitting the shell
materials and the respective parts explained in the first
embodiment was attached to a jig in a state where the opening
portion of the shell which is a surface opposite to the opening
portion of the inner box was placed upward so that the shell was
not deformed by foaming pressure of foaming urethane. Then, raw
materials of two-part foaming urethane containing cyclopentane as a
foaming agent were discharged while mixed by use of a mixer of a
high-pressure foaming machine so that the raw materials were
injected into the shell in a direction along the bottom surface
from an injection hole located in a machine chamber in the body
portion of the chest freezer. Then, the hole used for injection was
sealed immediately so that foaming urethane did not leak. When a
reaction of the two-part raw materials was started, the mixture
solution flew in the form of produced bubbles while being foamed on
the basis of vaporization of cyclopentane caused by reaction heat
of a resinification reaction and generation of carbon dioxide gas
as a byproduct of the resinification reaction. As a result, gaps in
the shell were filled with the mixture solution. After the shell
was left for 5 minutes during which hardening of the mixture
solution was completed, the shell was taken out from the jig. Thus,
there was obtained a heat insulation box body filled with closed
cells in this comparative example 1.
COMPARATIVE EXAMPLE 2
[0116] Two-part foaming urethane having open cells was injected
into the shell in the same manner as in the comparative example 1
so that the shell was filled with the foaming urethane. After
hardening was completed, the shell was taken out from the jig to
thereby obtain a heat insulation box body in this comparative
example 2. Incidentally, in the comparative example 2, a vacuum
cock was provided in a machine chamber located in its bottom
portion and for receiving a compressor, etc.
[0117] The content of evaluation is as follows.
[0118] (1) Heat insulating property
[0119] The quantity of leaking heat and the change thereof with the
passage of time were evaluated.
[0120] The quantity of leaking heat was obtained on the basis of
electric energy which was given when the inside of a chest freezer
equipped with a heater of known heating power in its center portion
was kept at an arbitrary temperature in the condition that the
chest freezer was put in an thermostatic chamber kept at another
arbitrary temperature.
[0121] In this occasion, the chest freezer was put in an
thermostatic chamber at 20.degree. C. in order to secure 50.degree.
C. as the temperature difference between the inside of the freezer
and the outside of the freezer in an actual use state, and in this
state, electric energy given to the heater was adjusted and
stabilized so that the temperature of the inside of the freezer is
kept to 30.degree. C. The quantity of given heat was calculated on
the basis of given electric energy per unit time and used as the
quantity of leaking heat.
[0122] Incidentally, a chest freezer produced herein was used when
the time longer than 48 hours was passed after the completion of
evacuation. A door having a heat insulation layer filled with
closed-cell urethane foam was used for the opening portion of the
chest freezer in common to the test examples 1 and 2 and the
comparative examples 1 and 2.
[0123] (2) Efficiency in Evacuation
[0124] The time required from the start of evacuation by use of a
vacuum pump having a gas-exhaust capacity of 1500 L/min to the end
when a vacuum value of 0.05 torr is confirmed by use of a Pirani
vacuum gauge disposed in a portion of a vacuum cock, was measured.
After the heat insulation box body was held for 60 seconds after
the confirmation of this value, the vacuum cock was closed so that
air, or the like, did not enter the heat insulation box body from
the outside. Thus, the evacuation of the heat insulation box body
was completed.
[0125] The degree of vacuum after 2 hours and the degree of vacuum
after 48 hours from the completion of the evacuation of the heat
insulation box body were measured by use of the Pirani vacuum
gauge.
[0126] Efficiency in evacuation was evaluated on the basis of the
time required for evacuation and the quantity of reduction of the
degree of vacuum.
[0127] (3) Design Characteristic in External Appearance
[0128] A result of comparison of smoothness in external appearance
by eye observation was evaluated as design characteristic in
external appearance so as to be classified into five-stage levels
based on the comparative example 1 representing a conventional
product.
[0129] Results of the items (1) to (3) are shown in the following
Table 1.
1 TABLE 1 Test Test Test Comp. Comp. Ex. 1 Ex. 2 Ex. 3 Ex 1 Ex. 2
Quantity of Leaking Heat 30.6 31.0 27.3 47.7 38.5 (kcal/h) Vacuum
Reaching Time 162 152 172 -- 282 (sec) Chang of 2 hours 0.06 0.06
0.11 -- 0.47 Degree of 48 hours 0.08 0.07 0.13 -- 1.06 Vacuum with
the Passage of Time (torr) Smoothness of Outer 4 4 4 3 2 Box
Smoothness of External Appearance: 4 = slightly good, 3 = even
level, 2 = slightly bad (with no problem in practical use)
[0130] As was apparent from results of Table 1, it could be
confirmed that all the test examples 1, 2 and 3 had remarkably
excellent heat insulating property compared with the comparative
example 1 showing a conventional heat insulation box body using
closed-cell urethane foam made with cyclopentane as a foaming
agent.
[0131] Further, the heat insulating property in all the test
examples 1, 2 and 3 was enhanced compared with a heat insulation
box body filled with open cell foaming urethane directly injected
as shown in the comparative Example 1.
[0132] As a factor thereof, the evacuation time is shortened and
the quantity of gas remaining in the inside of the shell is small
after the completion of evacuation, because structural materials
cut off from a slab of foamed article are used in the present
invention. This fact was confirmed from the degree of vacuum kept
high and the small quantity of leaking heat providing excellent
heat insulating property.
[0133] Particularly with respect to the test example 3, reduction
in the quantity of leaking heat was achieved with remarkable
enhancement of heat insulating property. It is believed that the
enhanced insulation ability is due to the effect obtained by use of
open cell polystyrene foam and by flattening the shape of each cell
so as to spread the cell in a direction perpendicular to the
direction of the thickness.
[0134] Further, it was found that the smoothness of the outer box
in the comparative example 2using open cell urethane foam as a
structural material was slightly lowered compared with the
comparative example 1 representing a conventional heat insulation
box body filled with closed-cell urethane foam without use of
vacuum heat insulation so that the comparative example 2 was
inferior to the comparative example 1 in external appearance design
characteristic.
[0135] On the contrary, the test examples 1, 2 and 3 according to
the present invention were not inferior in external appearance
design characteristic to the comparative example 1 representing a
conventional product, so that the test examples 1, 2 and 3 could
obtain good results.
[0136] External appearance design characteristic greatly depends on
the uniformity of the heat insulating material packed in the inside
of the shell. Accordingly, in the case of a large-size
refrigerator, the flowing distance of foaming urethane becomes very
long. Accordingly, in the case of comparative examples, a large
difference in the shape of flowing bubbles is generated between the
start point of foaming and the finally filled portion and, further,
flowing bubbles tend to be combined with one another to change the
flow of the bubbles. As a result, mechanical properties such as
compression strength, etc. vary widely in accordance with the
respective portions. That is, non-uniform contraction is created
because of the fact that the inside temperature raised up to about
120.degree. C. by a exothermic reaction and is cooled to the room
temperature after the completion of foaming, or because of the
difference of the environmental temperature of use, or the
like.
[0137] The fluidity of bubbles in foaming of open cell foaming
urethane is further inferior to that in closed-cell foaming
urethane. Accordingly, in foaming of open cell foaming urethane,
the aforementioned disadvantage occurs easily and closed cells are
apt to remain in the vicinity of the wall surface of the shell
where shearing stress caused by the flowing of the bubbles is not
applied to the bubbles so that the closed cells which are apt to be
deformed due to a change of the temperature are distributed
ununiformly. It is considered that this is a factor which tends to
degrade the external appearance design characteristic.
[0138] On the contrary, in structural materials used in the full
vacuum heat insulation box body, the slab of foamed article is so
configured that a foaming urethane mixture solution applied
uniformly is foamed only upward. Accordingly, the physical property
distribution is quite uniform, and moreover, it is possible to cut
structural materials selectively from a portion near the center of
the slab where most of the pores are communicated with one another,
so that deformation hardly occurs in the structural materials.
[0139] Further, in open cell urethane foam packed in the heat
insulation box body, foaming gas remains in the inside as it is,
and remaining of unreacted components, adsorption of the foaming
gas onto the resin, etc. occur frequently.
[0140] On the contrary, in the case of a slab of urethane foam,
foaming is performed in an opened state and structural materials
are cut selectively from a portion near the center where most of
the pores are communicated with one another. Accordingly, it is
unnecessary to keep a state where an excessive amount of foaming
gas remains in pores so as to be adsorbed easily. Furthermore, on a
single structural material cut out, processes such as heating,
drying under a vacuum state, etc. can be carried out easily, so
that extremely stable physical properties can be obtained and the
quantity of gas produced from the structural materials can be
suppressed in a state where the inside of the heat insulation box
body is in a vacuum. Accordingly, degradation of heat insulating
property depending on the degree of vacuum is further suppressed so
that reliability against vacuum loss from the inside over time can
be enhanced and the operating time of an evacuator used for
maintaining vacuum can be shortened. As a result, more power saving
is attained in the chest freezer using this heat insulation box
body.
[0141] Here, a notable result is obtained in comparison between the
test examples 1 and 2. That is, though both full vacuum heat
insulation box bodies exhibit good heat insulating property and are
sufficiently effective compared with the comparative examples 1 and
2, it is found that, in the case of the test example 2 using the
structural materials provided with gas-exhaust grooves, the grooves
do not affect its external appearance design characteristic and
that the time required for evacuation is shortened to thereby
enhance easiness of evacuation.
[0142] Embodiment 4
[0143] Referring now to FIGS. 9-12, the inside of the
circumferential side walls will be explained by illustrating only
the right walls.
[0144] The full vacuum heat insulation box body in this embodiment
is applied to a refrigerator. The inner box 22 having an uneven
shape 22a on its surface and constituting an interior surface of
the shell 21 is formed in such a manner that a complex sheet
material constituted by polystyrene resin containing butadiene
rubber as a middle layer, acrylonitrile, which has an excellent gas
barrier property as an upper layer and polypropylene as a lower
layer is prepared, silicon is also deposited on the surface of the
upper layer, and the thus obtained sheet is molded in a vacuum into
the inner box 21.
[0145] Further, the outer box 23 constituting an exterior surface
of the shell 21 is formed of a bent member which is a colored steel
plate shaped in the form of a hollow box integrating a ceiling, a
floor and opposite sides. An end side portion 33A of the inner box
22 is inserted into a groove 32A which is formed by bending an end
edge portion of the outer box 23 inward and in a zigzag
configuration, as shown in FIG. 10, so that the groove 32A has a
predetermined depth and is filled with an adhesive agent 31 of a
liquid substance having an adhesive sealing function. Thus, the
outer box 23 and the inner box 22 are joined to each other. The
configuration of the joint portion including the adhesive agent 31
is the same as the joint portion between the plate member 27 and
the outer box 23 as described previously in the first embodiment
with reference to FIG. 2. A wide reservoir portion 34A for
reserving the adhesive agent 31 is provided in the upper portion of
the groove 32A.
[0146] A structural material 25A to be inserted in the inside of
each of the opposite side walls, ceiling, floor and a middle wall
in the shell 21 is constituted by two parts 25a and 51. Among these
parts, the part 25a having a simple shape constituted by planes is
inserted in a smooth surface portion of the shell 21, that is, a
portion on the outer box 23 side in the ceiling, floor and middle
wall and opposite side walls. The part 25a exhibiting a triangular
sectional structure is cut out from a large slab of foamed article
obtained by foaming, a foaming resin such as foaming urethane, or
the like, having open cells. Further, the part 51 to be inserted in
the shell on the side of the inner box 22 having an uneven surface
shape 22a for shelf rests, cooled air circulating grooves, etc.
also exhibits a triangular sectional structure basically. However,
if the part 51 is formed, for example, of a simple plate-like
structural material, the structural material does not fully abut on
the uneven-shape portions such as shelf rests, etc., so that the
uneven-shape portions may be deformed by the atmospheric pressure
when the shell is evacuated. Therefore, the structural material
part 51 which can fully abut on the inner box 22 is formed of a
compression molding capable of having a free shape by using a
mixture consisting of powder obtained by pulverized urethane foam
and an adhesive agent melted by heating, so that the part 51 is
made to have a desirable shape following shelves, cooled air
circulating grooves, etc. As the powder used herein, a pulverized
resin foam such as foam of polystyrene, urethane, phenol, urea, or
the like, having open cells is preferably used. However, an
inorganic foam such as pearlite or particles of inorganic substance
or resin may be used. Incidentally, it is preferable that
gas-exhaust grooves as described in the aforementioned second
embodiment with reference to FIG. 8 are provided in the inner
surface of the outer box side part 25a of the structural material
25A. Other configurations including the configuration (labyrinthine
structure) of corner portions of side wall structural materials and
ceiling and floor structural materials, the configuration of the
joint portion between the outer box 23 and the plate member 27, the
composition of the adhesive agent 31, etc. are the same as those in
the aforementioned embodiments.
[0147] A method for producing a refrigerator formed from the full
vacuum heat insulation box body configured as described above will
be described below on the basis of the flow chart of FIG. 12 and
with reference to FIGS. 9 through 11.
[0148] First, a sheet is obtained by vapor deposition of silicon on
an inner surface of a complex sheet material which consist of
polystyrene resin containing butadiene rubber as a base material,
acrylonitrile excellent in gas barrier property arranged on the
inner side of the heat insulation wall, and polypropylene arranged
on the outer side of the heat insulation wall. The thus obtained
sheet is shaped into a box having upper and lower compartments by
vacuum molding to thereby obtain an inner box 22 which has an
uneven shape 22a in its surface and constitutes an interior surface
of the shell of the refrigerator. Then, a hollow bent article
integrating a ceiling, a floor and opposite sides is prepared by
bending a colored steel plate to thereby obtain an outer box 23
which constitutes an exterior surface of the shell of the
refrigerator. After the inner box 22 is inserted into the outer box
23, they are joined to each other at joint portions to form a first
shell which is opened in the back of the outer box (step 211). The
work of joining the outer box 23 and the inner box 22 is as
follows.
[0149] As shown in FIG. 10, the groove 32A provided in the outer
box 23 is filled with the aforementioned adhesive agent,
specifically an adhesive agent 31 obtained by mixing a liquid resin
such as an epoxy resin, or the like, with ceramics such as a metal
oxide, or the like. After an end side portion 33A of the inner box
22 is inserted into the groove 32A filled with the adhesive agent
31, this inserted state is held until the adhesive agent 31 in the
groove 32A has been hardened to thereby perform joining and sealing
between the outer box 23 and the inner box 22. In this occasion,
the adhesive agent 31 is charged more in the vicinity of the center
of each groove to make it flow by the insertion of the inner box
end side portion 33A, so that the groove 32A can be entirely filled
with the adhesive agent 31 and uniform and faultless sealing is
preferably obtained. By immersing the end side portion 33A of the
inner box 22 in the resin in the groove 32A formed in the outer box
23 in the aforementioned manner, defects such as incompletely
joined portions, and communicating portions, etc. can be
eliminated, so that a refrigerator shell structure in which the
joint portions are perfectly sealed is obtained. As a result,
defect portions such as holes passing through the shell, etc. are
reduced to secure a sealing structure having superior reliability
in blocking of gas such as air, water vapor, etc. entering the heat
insulation box body from the outside.
[0150] Then, structural materials to make the shell endure the
atmospheric pressure to prevent the deformation of the shell during
the evacuation work in the posterior step are prepared, inserted
into the first shell, and then sealed with a plate member 27 from
the outside (step 212). The preparation of the structural materials
is as follows. First, a mixture consisting of powder of pulverized
urethane foam and an adhesive agent melted by heating is
compression-molded into a desirable shape following shelves, cooled
air circulating grooves, etc. in the inner box 22 to thereby obtain
a first structural material, that is, a structural material part 51
basically exhibiting a triangular sectional structure. Further, a
foaming resin such as foaming urethane, or the like, having open
cells is foamed to prepare a large slab of foamed article. Second
and third structural materials are cut out from this large foamed
article. That is, the second structural material is a part 25a
having a triangular sectional structure so as to be disposed on the
outer box 23 side, face to face with the structural material part
51 and a third structural material is a structural material 26
having a shape like a flat plate so as to be inserted in the
opening portion in the back of the first shell. The structural
materials thus obtained are inserted in the first shell through the
opening in its back.
[0151] The insertion of the structural materials into the first
shell will now be described in detail.
[0152] First, the first structural materials, that is, the
structural material parts 51 are inserted in the inside of the side
walls along the inner box 22 having protrusion portions such as
shelves, etc. from the opening in the back of the first shell with
the base portions of the structural material parts 51 as the
forefronts. The second structural materials, that is, the
smooth-surface parts 25a are inserted in the flat ceiling and
middle wall from the opening of the back of the first shell with
the base portions of the parts 25a as the forefronts. Then, a
second structural material, that is, a part 25a is inserted on the
outer box 23 side in the side walls face to face with the
structural material parts 51 from the opening in the back of the
first shell with the vertex portions of the parts 25a as the
forefronts. Other second structural materials, that is, other parts
25a are inserted also in the ceiling and middle wall on the
opposite side to the previously inserted parts 25a, from the
opening in the back of the first shell with the vertex portions of
the parts 25a as the forefronts. In this occasion, the length and
thickness of the base portion of a part 25a inserted later are
preferably adjusted so that the base portion of the part 25a
projects backward by a slight distance, preferably, about 10 mm
from an extension line of the back of the inner box 22, in the same
manner as in the case of a chest freezer in the first embodiment.
Accordingly, the inside of side walls and ceiling and middle wall
of the first shell is filled.
[0153] After a bottom plate and a structural material are then
disposed in the back portion and a floor corresponding to a machine
chamber portion for mounting a compressor, etc., the opening in the
back of the first shell including the machine chamber is blocked by
the flat-plate like third structural material 26 and the joint
portion between the plate member 27 and the first shell is sealed
by an adhesive agent 31 to thereby form a fully closed second shell
(step 213). Then, evacuation is performed through a not-shown
vacuum valve attached to the plate member 27 (step 214).
Incidentally, the vacuum valve is attached to the machine chamber
portion so that the fully closed state can be kept after the
evacuation.
[0154] The evacuation is started under the condition that the
structural materials 25a, 51 and 26 put between the inner and outer
boxes 22 and 23 are not fixed by means of an adhesive agent, or the
like, before the adhesive agent 31 in the groove 32 of the joint
portion 29 between the outer box 23 and the plate member 27 is
hardened. The evacuation is continued until the adhesive agent 31
is hardened. Accordingly, when the evacuation is started, the plate
member 27 is pulled toward the inside of the second shell according
to the pressure difference between the air pressure of the inside
of the second shell and the air pressure of the outside thereof. As
a result, the plate member 27 functions as a piston for pressing
the third structural material 26 from the back side. The parts as
the second structural materials 25a inserted in the side walls,
ceiling and middle wall of the shell 21, are successively pressed
by the third structural material 26 pressed by the plate member 27,
so that the wedge effect is produced. As a result, there is no
slack in the direction of the thickness of each wall, so that the
shell can be substantially entirely filled without any gap.
Accordingly, even in the case where the inside of the shell reaches
a vacuum state, the shell is never deformed by the atmospheric
pressure. Thus, an excellent external appearance state can be kept.
After the adhesive agent 31 is hardened, the inner and outer boxes
22 and 23 and the respective structural materials 25a, 51 and 26
are kept only by close contact based on a vacuum to thereby obtain
a refrigerator constituted by a full vacuum heat insulation box
body which is light in weight and has a uniform strength
characteristic (step 215).
[0155] Incidentally, it is preferable, from the point of view of
workability, to use a thixotropic adhesive agent for a portion
where the groove of the joint portion of the shell is inclined
horizontally. Further, by adjusting the viscosity of the adhesive
agent as mentioned above, the joint portion between the inner and
outer boxes 22 and 23 can be joined simultaneously with evacuation
of the shell. That is, the viscosity values of adhesive agents to
be charged in the grooves 32 and 32A are adjusted in accordance
with the inclination of the joint portion 29 between the outer box
23 and the plate member 27 and the inclination of the joint portion
between the inner and outer boxes 22 and 23, respectively, and
evacuation is started before the adhesive agents in the grooves 32
and 32A is hardened, and the evacuation is continued until the
adhesive agents in the grooves 32 and 32A are hardened.
Accordingly, when evacuation is started, not only the plate member
27 but also the inner and outer boxes 22 and 23 can be operated as
pistons to press the structural materials from the outside, so that
the degree of mutual contact of the structural materials by means
of a vacuum can be enhanced. Further, because it is predicted that
air, water, etc. penetrate the adhesive agents to migrate into the
shell, adhesive agents containing an inorganic substance are
preferably used for the purpose of suppressing the penetration of
air, water, etc., into the inside of the shell.
[0156] After sealing the joint portion between the outer box 23 and
the plate member 27, it is effective to simply evacuate the inside
of the shell to form a low vacuum state in a range from about
10.sup.1 to 10.sup.2 torr to thereby stabilize the inside of the
shell so that the plate member 27 is attracted to abut on the
structural materials.
[0157] By keeping the inside of the shell in a vacuum state in the
aforementioned manner, the third structural material 26 is pressed
from the back side by means of the plate member 27 and the
structural material 25a is successively pressed by the third
structural material 26 to thereby produce a wedge effect, so that
slack or cavitation in the direction of the thickness of the wall
is prevented. Furthermore, because the plate member 27 is fixed
under the condition that the movement and contraction of the
structural materials including the aforementioned behavior are
stabilized, there is also produced such an effect that the shell
can be prevented from being deformed at the time of or after
full-scale evacuation in the posterior step for providing heat
insulating property.
[0158] That is, the shell in the fully closed state after
evacuation at the time of attaching the plate member 27 to the
outer box 23 is again evacuated with full-scale evacuation through
the vacuum valve after the attachment of the plate member 27, so
that gasses such as air, etc. remaining in the shell are exhausted
from the shell. Although the degree of vacuum in the shell in this
occasion varies depending on the kind of the structural material
used, sufficient heat insulating property can be provided when the
degree of vacuum is kept higher than 10.sup.-2 torr, preferably
higher than 10.sup.-2 torr. Under these conditions, the vacuum
valve provided in the outer box may be replaced by a sealing valve
such as a check valve, or the like.
[0159] Further, to perform evacuation for keeping a sufficient
vacuum in the inside of continuous pores contained in the
structural materials in the shell with a fully closed structure, it
is effective that grooves or holes extending in the direction of
the major axis from the portion of the vacuum valve or its vicinity
are formed in advance, in structural materials formed from a
solidified molding of a pulverized urethane foam and a molding cut
out from a slab of foamed article. Accordingly, because gasses in
pores of structural materials are conducted in the grooves or holes
and exhausted therethrough easily, the time required for evacuation
can be greatly shortened.
[0160] If the grooves are wide, they are apt to be deformed by the
atmospheric pressure Accordingly, it is rather preferable to
provide large number of grooves each having a depth so as not to
hinder handling of structural materials. When, for example, grooves
each having a width of 3 mm and a depth of 5 mm are formed at
intervals of a pitch of 50 mm, a sufficient effect is obtained.
[0161] In order to confirm the heat insulating effect of the full
vacuum heat insulation box body according to the fourth embodiment,
results of evaluation of heat insulating property based on the
quantity of leaking heat and design characteristic based on the
smoothness of the shell wall surface in comparison of test examples
4, 5 and 6 with comparative examples 3 and 4 will be described
below.
TEST EXAMPLES 4, 5 AND 6
[0162] By using a refrigerator having an internal volume of 120 L,
the following test examples 4 through 6 were prepared by the
producing method explained in the fourth embodiment. That is, a
full vacuum heat insulation box body (test example 4) was formed by
using structural materials which had no gas-exhaust groove, and
which were formed by cutting a slab of urethane foam having open
cells and processing the cut out pieces; another full vacuum heat
insulation box body (test example 5) was formed by using structural
materials which were formed by cutting a slab of foam and
processing them and which were provided with grooves each having a
width of 5 mm and a depth of 5 mm arranged at intervals of a pitch
of 50 mm; and a further full vacuum heat insulation box body (test
example 6) was formed by using structural materials which were
formed by cutting a slab of foam and processing them, and which
were provided with grooves each having a width of 10 mm and a depth
of 5 mm arranged at intervals of a pitch of 50 mm.
COMPARATIVE EXAMPLE 3
[0163] As the steps of the fourth embodiment shown in FIG. 12, a
shell comprising an inner box formed of a vacuum molding of ABS
resin fitted into an outer box formed of a formed product of a
colored steel plate with plurality of bent portions was attached to
a jig to prevent deforming of the shell by the foaming pressure of
foaming urethane. Then, two-part foaming urethane raw materials
using cyclopentane as a foaming agent are mixed by means of a mixer
of a high-pressure foaming machine and the mixed solution was
injected from holes provided in the neighbors of longitudinal
center portions on opposite side walls in the plate member in the
back surface of the shell and then the holes used for injection
were immediately sealed so that foaming urethane did not leak. When
a reaction of the two-part raw materials was started, the mixture
solution flew in the form of produced bubbles while being foamed on
the basis of vaporization of cyclopentane caused by reaction heat
of a resinification reaction and generation of carbon dioxide gas
as a by-product of the resinification reaction. As a result, gaps
in the shell were filled with the mixture solution. After the shell
was left for 5 minutes during which hardening of the mixed solution
was completed, the shell was taken out from the jig. Thus, there
was obtained a heat insulation box body filled with closed
cells.
COMPARATIVE EXAMPLE 4
[0164] Two-part foaming urethane having open cells was injected
into the shell in the same manner as in the comparative example 3
so that the shell was filled with the foaming urethane. After
hardening was completed, the shell was taken out from the jig to
thereby obtain a heat insulation box body in this comparative
example 4. Incidentally, in the comparative example 4, a vacuum
cock was provided in a machine chamber located in its bottom
portion for receiving a compressor, etc The content of evaluation
is as follows. Incidentally, a door used in the same refrigerator
as an existing product was used for the opening portion of the
refrigerator in common to the test examples 4, 5 and 6 and the
comparative examples 3 and 4.
[0165] (1) Weight of Structural Material
[0166] The weight of structural materials put in the shell was
measured.
[0167] In all the heat insulation box body, weight increase, that
is, the difference between weight before putting in structural
materials and weight after putting in structural materials, was
employed.
[0168] (2) Heat Insulating Property
[0169] The quantity of leaking heat and the change thereof with the
passage of time were evaluated.
[0170] The quantity of leaking heat was obtained on the basis of
electric energy which was given when the inside of a refrigerator
equipped with a heater of known heating power in its center portion
was kept at an arbitrary temperature in the condition that the
refrigerator was put in an thermostatic chamber kept at another
arbitrary temperature. As the temperature conditions used in this
occasion, the temperature of the inside of the thermostatic chamber
and the temperature of the inside of each refrigerator as a sample
were set to -0.degree. C. and +30.degree. C., respectively.
[0171] (3) Efficiency in Evacuation
[0172] The time required from the start of evacuation by use of a
vacuum pump having a gas-exhaust capacity of 1500 L/min to the end
when a vacuum value of 0.05 torr is confirmed by use of a Pirani
vacuum gauge disposed in a portion of a vacuum cock. After the heat
insulation box body was held for 60 seconds after the confirmation
of this value, the vacuum cock was closed so that air, or the like,
did not enter the heat insulation box body from the outside. Thus,
the evacuation of the heat insulation box body was completed.
[0173] The degree of vacuum after 2 hours and the degree of vacuum
after 48 hours from the completion of the evacuation of the heat
insulation box body were measured by use of the Pirani vacuum
gauge.
[0174] Efficiency in evacuation was evaluated on the basis of the
time required for evacuation and the quantity of reduction of the
degree of vacuum.
[0175] (4) Design Characteristic in External Appearance
[0176] A result of comparison of smoothness in external appearance
by eye observation was evaluated as design characteristic in
external appearance so as to be classified into five-stage levels
based on the comparative example 3 representing a conventional
product.
[0177] Results of the items (1) to (4) are shown in the following
Table 2.
2 TABLE 2 Test Test Test Comp. Comp. Ex. 4 Ex. 5 Ex. 6 Ex. 3 Ex. 4
Weight of Structural 3.7 3.7 3.7 2.9 4.4 Materials (kg) Quantity of
Leaking Heat 22.1 22.5 22.7 28.9 26.1 (kcal/h) Vacuum Reaching Time
116 108 104 -- 155 (sec) Chang of 2 hours 0.06 0.06 0.06 -- 0.72
Degree of 48 hours 0.08 0.07 0.07 -- 1.43 Vacuum with the Passage
of Time (torr) Smoothness of Outer 4 4 3 3 2 Box Smoothness of
External Appearance: 4 = slightly good, 3 = even level, 2 =
slightly bad (with no problem in practical use)
[0178] As was apparent from results of Table 2, it could be
confirmed that all the heat insulation box bodies of the test
examples 4, 5 and 6 had remarkably excellent heat insulating
property compared with conventional heat insulation box bodies of
the comparative examples 3 and 4 using closed-cell foaming urethane
containing cyclopentane as a foaming agent.
[0179] First, the weight of the structural materials in each of the
test examples 4, 5 and 6 and the comparative example 4 is heavier
than that in the comparative example 3 as a prior art example. This
is because the density of the structured materials is inevitably
increased to obtain a strength necessary for preventing deformation
of structural materials caused by the atmospheric pressure since
the inside of the shell is in a vacuum state. Particularly with
respect to the comparative example 4, the reason (why the weight of
the structural materials is heavy) is because foaming urethane
having open cells is inferior in fluidity, so that it is necessary
to obtain both uniform quality and improved overall mechanical
strength by excessive filling of the foaming urethane so as to
obtain necessary performance in respective parts of the heat
insulation box body.
[0180] Further, in any of the test examples 4 through 6, evacuating
efficiency is improved and excellent values are exhibited in both
heat insulating property and the loss of vacuum over time, compared
with the comparative example 4 in which foaming urethane having
open cells is injected directly to fill the shell.
[0181] Further, design characteristic in external appearance is
also improved compared with the comparative examples 3 and 4. This
is based on the advantage that a low-density large-strength product
is obtained stably in the case of a slab of foamed article whereas
in the case of injection foaming of foaming urethane having open
cells, density and strength distributions are apt to become wide
because remaining of closed cells and non-reacted components,
absorption of the foaming agent onto the resin, etc. occur
frequently and also because the fluidity of bubbles at the time of
formation of the heat insulation box body is inferior so that a
uniform product is not obtained, as described in the aforementioned
first embodiment.
[0182] In addition, from a slab of foamed-article, it is possible
to selectively obtain a portion containing a very large number of
open cells, and further, the amount of gasses generated by
structural materials under the condition that the inside of the
heat insulation box body is in a vacuum state can be better
suppressed because processes such as heating of the cut-out
structural materials, drying of the structural materials under a
vacuum state, etc. can be made easily. Accordingly, lowering of
heat insulating property depending on the degree of vacuum can be
suppressed so that the improvement of reliability against vacuum
loss from the inside over time can be achieved, and further, the
operating time of the evacuator can be shortened correspondingly so
that more power saving can be achieved with the refrigerator using
this heat insulation box body.
[0183] Further, with respect to the design characteristic in
external appearance, in comparison between the test examples 4
through 6, the uneven portions such as shelf rests, etc. of the
inner box are never deformed and never dented by the atmospheric
pressure exerted by a vacuum state kept in the inside of the shell.
Further, any of the full vacuum heat insulation box body exhibits
good heat insulating property compared with the comparative example
4.
[0184] On the other hand, in the case where gas-exhaust grooves are
provided on surfaces of structural materials located in the center
portion in the direction of the thickness of the wall, slight
undulation appears in the test example 6 in which the grooves are
wide but design characteristic in external appearance is only
minimally degraded.
[0185] Further, in the test example 4 in which no groove is
provided, there is obtained a result that heat insulating property
just after evacuation is slightly inferior to that in the test
example 5.
[0186] Although these results vary in accordance with the hardness
and the size of pores of the structural materials, it is considered
that the results do not so widely depart from the values of this
evaluation, when taking a range satisfying preferable conditions in
both the economy and properties such as heat insulating property,
or the like, into consideration.
[0187] It is inferred from the above results that the structural
materials are most preferably provided with gas-exhaust grooves
each having a width of about 5 mm in the neighbor of the center in
the direction of the thickness of the wall.
[0188] In the fourth embodiment, instead of the method of injecting
foaming urethane having open cells into the shell to fill the
latter with the foaming urethane, compression moldings of a mixture
of pulverized urethane foam having open cells and an adhesive agent
melted by heating or moldings cut out from a slab of urethane foam
having open cells are used as structural materials. Accordingly,
the remaining quantity of dispersion components in a vacuum, such
as non-reacted components of foaming urethane, gasses adsorbed onto
the foamed resin agent, etc., is reduced and an advantage that a
low-density large-strength product is obtained stably can be
brought about.
[0189] In addition, in the case of a slab of foamed article, open
cell portions located in the vicinity of the center can be
selectively cut out and the quantity of gasses generated from
structural materials under the condition that the inside of the
heat insulation box body is in a vacuum state can be better
suppressed because processes such as heating of the cut-out
structural materials, drying of the structural materials under a
vacuum state, etc. can be made. Accordingly, the lowering of heat
insulating property depending on the loss of vacuum over time can
be suppressed, so that electric energy required for operating a
refrigerant circuit and devices pertinent to the refrigerant
circuit can be reduced and also, when, for example, an evacuator is
attached to the refrigerator in order to keep the degree of vacuum,
the operating time of the evacuator can be shortened greatly so
that more power savings can be achieved.
[0190] Embodiment 5
[0191] Referring now to FIGS. 13-15, the same parts as those in the
first, second, third and fourth embodiments are referenced
correspondingly. Incidentally, only a joint portion between the
outer box and the plate member is representatively shown here as a
joint portion of the shell constituent members. As to the joint
portion between the outer box and inner box FIG. 10 is referred
to.
[0192] The full vacuum heat insulation box body in this embodiment
is applied to a chest freezer. The configuration of joint portions
between constituent members of the shell 21 constituted by the
outer and inner boxes 23 and 22 and the plate member 27 and the
configuration of structural materials (not shown) inserted in the
shell are substantially the same as in the aforementioned
embodiments. This embodiment is different from the aforementioned
embodiments in that a mark 61 as shown in FIG. 14 is provided to
indicate a preferable cutting position of the shell surface at the
time of disassembling. Here, the mark 61 is formed by a concave
line 61a as shown in FIG. 15.
[0193] In more detail, as shown in FIGS. 13 and 15, the joint
portion 29 between the outer box 23 and the plate member 27 is
constituted by a groove 32 having a predetermined depth which is
formed by bending an end edge portion of the outer box 23 inward in
zigzag and filled with an adhesive agent 31 of a liquid substance
having an adhesive sealing function, and an end side portion 33
formed in the plate member 27 which can be inserted into a deep
portion of the groove 32. The mark 61, that is, the concave line 61
a is formed in a position which is on the outer circumferential
surface of the outer box 23 having the zigzag bent portion and
which corresponds to the zigzag bent portion, that is, in a portion
23c which is opposed to the base end side piece 23b of the zigzag
bent portion.
[0194] Further, if the joint portion between the outer and inner
boxes 22 and 23 is intended to be used for the cutting position of
the shell surface at the time of disassembling, a mark formed by a
concave line, or the like, is given clearly to a position which is
on the outer circumferential surface of the outer box 23 having the
zigzag bent portion forming the groove 32A shown in FIG. 10 and
which corresponds to the zigzag bent portion.
[0195] That is, a gap which is continuous over the whole
circumference of the joint portion between the outer and inner
boxes 23 and 22 is also formed as a groove between the base end
side piece 23b of the zigzag bent portion and a portion 23a on the
extreme end surface of the outer box 23 opposite to the base end
side piece 23b of the zigzag bent portion. Further, a gap G which
is continuous over the whole circumference of the joint portion 29
is formed between the base end side piece 23b and the portion 23c
on the outer circumferential surface of the outer box 23 opposite
to the base end side piece 23b of the zigzag bent portion. Gap G is
outside the grooves 32 and 32A, that is, inside the shell 21, and
is a portion which is not filled with the adhesive agent 31, so
that this gap is not fixed. Accordingly, by cutting the portion
corresponding to the zigzag bent portion on the outer
circumferential surface of the outer box 23 (portion of concave
line 61a) at the time of disassembling, air can be introduced into
the shell 21 easily. Because structural materials disposed in the
shell 21 constituted by the outer and inner boxes 23 and 22 and the
plate member 27 are fixed to the shell 21 only by close contact by
means of a vacuum, the close-contact state of the respective
members is released so that the members are peeled off and
separated easily when the inside of the shell 21 is returned to an
atmospheric pressure state by introduction of air.
[0196] A method for disassembling the full vacuum heat insulation
box body, that is, the chest freezer configured as described above
will be described below with reference to FIGS. 13 through 15
showing the joint portion 29 between the outer box 23 and the plate
member 27 cut by way of example. First, a notch 61b having a depth
of the order of mm, preferably, in a range from 1 to 5 mm, is
formed perpendicularly to the outer surface of the outer box along
a portion forming a preferable cutting position of shell surface in
the joint portion 29 between the outer box 23 and the plate member
27 located on the bottom surface, for example, along the mark 61
formed by the concave line 61 a provided in a position
corresponding to the reservoir portion 34 in the outer surface of
the outer box. The notch 61b is formed over the whole outer
circumference of the joint portion 29. The reservoir portion 34 is
formed in a predetermined position by use of a roll making machine,
or the like. Accordingly, the aforementioned cutting operation can
be carried out efficiently if a cutter 64 provided with a cutting
guide 63 for guiding the tip of a cutting edge 62 to a position at
a predetermined distance from an end side of the outer box 23 as
shown in FIG. 13 is used.
[0197] The reason why the shell surface cutting position is set to
a position corresponding to the reservoir portion 34 is that the
shell surface can be cut easily in this position without the
necessity of keeping high accuracy in the direction of the cutting
depth compared with the other flat surface portions of the outer
box because four steel plates and two or more gap portions are
formed in this position by the zigzag bent portion of the outer box
23 and the end side portion 33 of the plate member 27 inserted in
the groove 32 before the structural material is reached.
[0198] As described above, the gap G which is continuous over the
whole circumference is formed in the joint portion 29 between the
outer box 23 and the plate member 27 and also the structural
materials disposed in the shell 21 constituted by the outer and
inner boxes 23 and 22 and the plate member 27 are fixed to the
shell 21 only by close-contact by means of a vacuum without use of
any adhesive agent. Accordingly, if air is introduced into the
shell 21 through the notch 61b so that the vacuum state is
eliminated, the close-contact of the structural materials with the
inner and outer boxes 22 and 23 is released so that they are
naturally peeled off and separated easily.
[0199] When the outer circumference of the outer box 23 is cut
along the mark 61 represented by the broken line in FIG. 14 in the
aforementioned manner and then the plate member 27 capable of being
cut off by cutting the outer circumference of the outer box 23 is
removed, the structural materials can be taken out and recovered
easily without injury.
[0200] Further, if the mark 61 is formed by the concave line 61a as
shown in FIG. 15, the cutting edge 62 can be guided by the walls on
opposite sides of the concave line 61a. Accordingly, the cutter 64
holding a depth can be used, so that the aforementioned cutting
operation can be carried out more simply and more easily.
[0201] As described above, in the method for disassembling the full
vacuum heat insulation box body according to the present invention,
structural materials can be recovered without injury, so that the
structural materials can be used again as structural materials of a
similar full vacuum heat insulation box body. Further, the shell
members comprising the inner and outer boxes 22 and 23 joined to
each other can be joined again to the plate member 27 and recycled
if a simple repair operation is carried out, that is, if, for
example a new joint portion prepared separately is joined to the
shell members or a new joint portion is formed in the plate member
27.
[0202] Further, if all the joint portion between the inner and
outer boxes 22 and 23 and the joint portion between the outer box
23 and the plate member 27 are removed, members usable for some
other purpose can be obtained. By melting, or the like, usable raw
materials with a small impurity content can be also recovered from
the members. Accordingly, it is possible to collect members which
are usable for various purposes.
[0203] Having now fully described the present invention, it will be
apparent to one of ordinary skill in the art that many changes and
modifications can be made thereto without departing from the spirit
and scope of the invention as set forth herein. This application is
based on Japanese Patent Application No. 10-013873 filed on Jan.
27, 1998 and Japanese Patent Application No. 10-207647 filed on
Jul. 23, 1998, the entire contents of which are hereby incorporated
by reference.
* * * * *