Note: Descriptions are shown in the official language in which they were submitted.
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INSULATED CONTAINER, INSULATING MATERIAL, AND
MANUFACTURING METHOD OF THE INSULATED CONTAINER
BACKGROUND OF THE INVENTION
The present invention relates to an insulated container
used for example as a cooler box, a thermos bottle or an
insulated lunch box, a suitable insulating material for such a
container and a method for its manufacture. More particularly
the present invention relates to an insulated container wherein
an insulating material, made by filling a gas having a lower
thermal conductivity than that of air into a bag having gas
barrier properties, is disposed between inner and outer walls of
a double walled container having inner the outer walls 30ined
together as one. The invention also relates to the insulating
material used in the container and the method of manufacturing
the container.
Heretofore, there have been available insulated containers
such as cooler boxes made with inner and outer walls of a
synthetic resin, with the space between the inner and outer
walls filled with, an organic foam material such as rigid
urethane foam or polystyrene foam, or an inorganic powder such
as perlite, to thereby form an insulating layer.
Moreover there are also available insulated containers
wherein the inner and outer wall are made from a metal material,
with the space between forming a vacuum insulating layer.
However, with the former insulated container which is
filled with an insulating material such as foam, since the
thermal conductivity of the insulating material is high, then a
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thick insulating layer is required to increase the insulating
performance of the container. Moreover, when filling the foam
material and the like into the space between the inner and outer
walls, the insulating layer must be of a predetermined thickness
to enable an efficient filling operation. As a result, the
insulating layer must be made from 5 to 10 times thicker than
that for an insulated container having a vacuum insulating
layer. Therefore, in the case of insulated containers filled
with an insulating material, the volumetric efficiency, namely,
the ratio of the inside container volume to the total volume
with the opening closed, is reduced, so that such containers are
generally not suitable for portable use.
With the latter insulated container having a vacuum
insulating layer, excellent insulating performance is possible
even if the insulating layer is made thin, so that the container
is ideal for portable use. However there are problems due to
difficulties with manufacture and high cost. Furthermore, since
the inner and outer walls are subjected to atmospheric pressure
loadings, the shape of the inner and outer walls is restricted
to a pressure resistant structure which can resist the
atmospheric pressure loadings. It is therefore difficult to
make a convenient rectangular box like shape container with
plain walls.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an
insulated container having low manufacturing cost, excellent
insulating performance, and a high volumetric efficiency, and
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also to provide a method for its manufacture and a suitable
insulating material therefor.
A first aspect of the present invention involves an
insulated container made with an insulating layer between inner
and outer walls of a double walled container with the inner and
outer walls joined together as one, wherein an insulating
material made by filling a bag with a low thermal conductivity
gas comprising at least one of gases such as Xenon, Krypton and
Argon is disposed between the inner and outer walls.
In a preferred embodiment of the insulated container, the
bag may be made from a material selected from synthetic resin
film, metal laminated synthetic resin film, and metal vapor
deposited synthetic resin film. The thickness of the insulating
material may be less than 5 mm. Within the space, several
layers of insulating material of less than 5 mm in thickness
can be arranged overlapped together. Noreover a soft foam type
insulating material may be filled in the space between the inner
and outer walls of the double walled container and the
insulating material.
According to a second aspect of the present invention, the
insulating material comprises a bag made from a film having gas
barrier properties, which is filled with a low thermal
conductivity gas of at least one of Xenon, Krypton and Argon.
In a preferred embodiment of the insulating material, the
bag is made from a material selected from synthetic resin film,
metal laminated synthetic resin film, and metal vapor deposited
synthetic resin film. The inside of the bag may be formed with
multi-layered pleats to prevent gas convection. Moreover, the
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insulating material may be made by overlapping together a
plurality of bags respectively filled with a low thermal
conductivity gas and with a thickness of each layer of less than
5 mm. The bag may be arranged between the walls of the double
walled structure, and a soft foam type insulating material
provided between the double walled structure and the bag.
A third aspect of the present invention involves a method
of manufactùring an insulated container made with an insulating
layer between inner and outer walls of a double walled container
with the inner and outer walls joined together as one, wherein
the inner and outer walls are joined together as one with the
bag disposed beforehand in a space therebetween, and the bag is
then filled with a low thermal conductivity gas of at least one
of Xenon, Krypton and Argon, and sealed to form an insulating
layer.
In a preferred embodiment of this method, the bag is made
from a material selected from synthetic resin film, metal
laminated synthetic resin film, and metal vapor deposited
synthetic resin film. The thickness of the insulating layer may
be made under 5 mm. A plurality of bags may be arranged
overlapped together in the space between the inner wall and the
outer wall, and these bags respectively filled with a low
thermal conductivity gas to give a plurality of overlapped gas
filled bags.
In a more preferred embodiment of this method, a tube
shaped gas inlet may be provided in the bag, and an opening
leading to the gas inlet provided in the double walled
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container, such that when the bag is arranged in the space
between the inner wall and the outer wall, the gas inlet leads
out from the opening in the double walled container. The bag
arranged in the double walled container may thus be filled with
a low thermal conductivity gas through the gas inlet, after
which the gas inlet is sealed. The sealed gas inlet may then be
inserted into the opening and the opening covered.
With the insulated container of the present invention,
since the insulati~g material which comprises a bag filled with
a low thermal conductivity gas of at least one of Argon, Xenon,
and Krypton, is arranged in the space between the inner and the
outer walls, then compared to existing insulated containers
using foam type insulating materials, the insulating layer can
be made thinner, and the volumetric efficiency of the insulated
container improved. More specifically, compared to insulated
containers using foam type insulating materials and the like,
the thickness of the insulating layer can be reduced by more
than half with the equivalent or greater insulating performance,
and the volumetric efficiency can also be increased. Moreover,
with the insulated container using urethane type foam as the
insulating material, since the thermal resistance of urethane
itself is poor, this cannot be used for thermos flasks and the
like which take boiling water, even if a synthetic resin
material of good thermal resistance is used in the inner and
outer walls. The insulated container of the present invention
can however also be used as a heat ret~;n;ng container, since
the inner and outer walls and the bag are all made of a
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synthetic resin or metal having good thermal resistance.
Moreover by using a gas filled bag for the insulating material,
the insulated container may be made lighter.
Furthermore, compared to the insulated containers with a
vacuum insulating layer, since the inner and outer walls are not
subjected to atmosphere pressure loadings, the insulated
container does not need to have a pressure resistant structure.
Therefore, the insulated container can be made thin and light
weight and in various shapes such as a box like shape with plain
walls.
Since a flexible insulating material is filled in the space
between the inner and an outer walls and the bag, the insulating
performance of the insulated container can be improved due to
the effect of the flexible insulating material in offsetting the
reduced insulating performance at the corners where the
thickness of the bag is less.
With the method of manufacturing the insulated container of
. . ~,
the present invention, since the inner and outer walls are
joined together as one, with the bag disposed beforehand in a
space therebetween, and the bag then filled with a low thermal
conductivity gas and sealed, the bag can be fitted snugly into
the space. Therefore, the bag can be installed even when the
space is small or narrow. Moreover, compared to the foam
material filling operation or the evacuation and sealing
operation involved with the conventional insulated containers,
the manufacturing operation for the insulated container is
simple, involving merely filling the bag with a gas and sealing.
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Therefore, manufacturing operations for the insulated container
can be improved, and since these operations are simplified, and
foam material or evacuation equipment is not required, the
manufacturing cost of the insulated container can be reduced.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a longitudinal sectional view showing an example
of an insulated container according to the present invention:
FIG. 2 is a transverse sectional view of the insulated
container of FIG. 2:
FIG. 3 iS a development view of a bag:
FIG. 4 is a longitudinal sectional view for explaining a
method of manufacturing the insulated container of FIG. 1,
showing a condition of the bag prior to filling with a gas: and
FIG. 5 is a cross sectional view showing an insulated
panel being an example of an insulating material according to
the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
AS follows is a detailed description of the present
invention based on embodiments thereof. The scope of the
present invention however is not to be restricted to the
disclosure of the embodiments. The disclosure of these
embodiments is merely for example only, and it goes without
saying that various modifications and alterations can be made
thereto without exceeding the scope of the invention.
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First Embodiment
FIGS. 1 and 2 show an example of an insulated container
according to the present invention. The insulated container 1
comprises an inner wall 2, an outer wall 3 disposed around the
inner wall 2, and a bag 5 (insulating material) which is
arranged in a space 4 between the inner wall 2 and the outer
wall 3. The bag 5 is filled with a low thermal conductivity gas
comprising one of Argon, Xenon, or Krypton or a mixture of these
at approximately atmospheric pressure, and then sealed. The
inner wall 2 and outer wall 3 are joined together as one with a
`space therebetween to make up a double walled structure. The bag
5 is accommodated in the space 4 between the inner wall 2 and
the outer wall 3 to thus form an insulating layer 8. The
thickness of the insulating layer 8-is made less than 5 mm so as
to restrict convection of the gas inside the bag 5.
The low thermal conductivity gas has a thermal conductivity
k smaller than that of air (2.41 x 102 W-m 1-K-1; 0 C ). For
this gas an inert gas such as xenon ( k = 0.52 x 102 W-m~1-
K 1; o C ), Krypton (k = 0.87 x 102 W-m 1-K 1; o C ), Argon
(k = 1.63 x 102 W-m~1-K~1; 0 C ), or a mixture of these gases
may be used. Of the inert gases, Xenon, Krypton, and Argon gas
are particularly suitable since they have low thermal
conductivity and present m;nim~l problems to the environment.
The inner wall 2 and outer wall 3 are manufactured from a
synthetic resin material such as Ass resin, polypropylene,
polyethylene, polyethylene-terephthalate, polycarbonate,
polystyrene, acrylic resin, or rigid PVC. However the material
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for the walls 2 and 3 is not limited to synthetic resins, and
may be a metal material such as stainless steel. Moreover one
wall may be made of a synthetic resin and the other of a metal.
The inner wall 2 is formed in a box like shape with an open
top end and a closed bottom end. A flange 2a is formed on the
top end of the inner wall 2. The outer wall 3 comprises a
rectangular sleeve shaped side wall 3a, wlth a base plate 3b
joined to a lower edge thereof. The side wall 3a is disposed
around the inner wall 2, with an upper edge of the side wall 3a
joined as one to the lower face of the outer rim portion of the
flange 2a of the inner wall 2. The joint between the upper
edge of the side wall 3a and the lower face of the outer rim
portion of the flange 2a, and the joint between the lower edge
of the side wall 3a and the base plate 3b is m--ade using a
jointing method involving one ofi an adhesive, heated fusion, or
ultrasonic welding. A circular shaped aperture 3c is formed in a
middle portion of the base plate 3b of the outer wall 3. This
aperture 3c may be blocked by a stopper or a lid.
A metal coating may be provided on the inside of the outer
wall 3 and on the outside of the inner wall 2 to m; n; m; ze
thermal radiation. This metal coating can be formed by a method
or a combination of two methods selected from methods such as;
vacuum vapor deposition, chemical plating, and electroplating,
using a metal such as copper, silver, aluminum or chrome or an
alloy thereof.
The bag 5 which is inserted into the space 4 between the
inner wall 2 and the outer wall 3 is shown in the development
view of FIG. 3. It is formed with a rectangular shaped bottom
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portion 5b having side portions 5a connected to the four edges
thereof. A gas inlet Sc which extends out in the form of a tube,
is provided in a central portion on the bottom face of the
bottom portion 5b. The bag can be made from a synthetic resin
film, a metal laminated synthetic resin film, or a metal vapor
deposited synthetic resin film. The material of the synthetic
resin film will preferably have a low gas radiation amount and
gas permeability, and a high rigidity. For example, it may be
selected from materials such as; polypropylene, polyethylene-
terephthalate, polyester, polycarbonate, polystyrene, rigid PVC,
polyamide and the like. The thickness of the synthetic resin
film is preferably from O.OS - 1.0 mm. With the metal laminated -
film, this is made by l~m; n~ting a metal foil such as aluminum
foil with a synthetic resin film. With the metal vapor deposited
synthetic resin film, this is made by vapor depositing a metal
such as aluminum onto a synthetic resin film.
The bag 5 is filled through the gas inlet 5c with a low
thermal conductivity gas of one or a mixture of the above-
mentioned low thermal conductivity inert gases of Argon, Xenon,
and Krypton, and is then sealed. With this operation the four
side portions Sa are erected to give the form of box having a
bottom, and of a size so as to be accommodated within the space
4 between the inner wall 2 and the outer wall 3.
The corners in the space between the inner wall 2 and outer
wall 3 into which the sealed gas bag 5 cannot reach are filled
with a flexible foam type insulating material 7 such as soft
-urethane foam.
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An example of a method of manufacturing the insulated
container 1 will now be explained with reference to the
drawings.
The synthetic resin inner wall 2 and the outer wall 3 are
first made up, and the bag 5 prepared. An edge portion of the
bag is adhered beforehand to the lower face of the flange 2a of
the inner wall 2. The lower face of the outer rim portion of
the flange 2a of the inner wall 2 and the upper edge of the
side wall 3a of the outer wall 3 are then joined together with
an adhesive such as an epoxy resin. The corners of the space 4
be~ween the inner wall 2 and an the outer wall 3 are then filled
with a foam insulating material 7. Then with the unfilled gas
bag installed in the space 4 between the inner wall 2 and the
outer wall 3 as shown in FIG. 4, the base plate 3b is joined
with an adhesive such as an epoxy resin to the lower edge of the
side wall 3a of the outer wall 3. At this time the gas inlet 5c
of the bag 5 passes out through the aperture 3c in the base
plate 3b. A low thermal conductivity gas such as Argon, xenon,
or Krypton or a mixture of these gases is then introduced into
the bag 5 through the gas inlet 5c, which is then sealed with an
adhesive or by heat sealing. The sealed gas lnlet 5c is then
placed in the base plate 3b inside of the aperture 3c which is
then blocked with a stopper or a lid.
with such an insulated container 1, since the bag 5
(insulating material ) which is filled with a gas having a lower
thermal conductivity than that of air, is arranged in the space
4 between the inner wall 2 and the outer wall 3, then compared
to the foam type insulated container, the insulating layer 8 can
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be made thinner, and the volumetric efficiency of the insulated
container 1 improved. More specifically, compared to insulated
containers using foam type insulating materials and the like,
the thickness of the insulating layer 8 can be reduced by more
than half with the equivalent or greater insulating performance,
and the inside volume can also be increased by the amount of
reduced thickness. Moreover, with the insulated container using
urethane type foam as the insulating material, since the thermal
resistance of urethane itself is poor, this cannot be used for
thermos flas~s and the like which take boiling water, even if a
synthetic resin material of good thermal resistance is used in
the inner wall 2 and the outer wall 3. The insulated container
1 of the present-embodiment can however also be used as a heat
ret~;ning container, since the inner wall 2 and the outer wall 3
and the bag 5 are all made of a synthetic resin having good
thermal resistance. Moreover by using the gas filled bag 5 for
the insulating material, the insulated container may be made
lighter.
Furthermore, compared to the insulated containers with a
vacuum insulating layer, since the inner wall 2 and the outer
wall 3 are not subjected to atmosphere pressure loadings, the
insulated container 1 does not need to have a pressure resistant
structure. Therefore, the insulated container can be made thin
and light weight and in various shapes such as a box like shape
with plain walls.
Since the flexible insulating material 7 is filled in the
space between the inner wall 2 and the outer wall 3 and the bag
5, the insulating performance of the insulated container 1 can
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be improved due to the effect of the flexible insulating
material 7 in offsetting the reduced insulating performance at
the corners where the thickness of the bag S is less.
Moreover, with the method of manufacturing the insulated
container 1 of the present embodiment, since the inner wall 2
and the outer wall 3 are joined together as one, with the bag 5
disposed beforehand in a space 4 therebetween, and the bag 5
then filled with a low thermal conductivity gas and sealed, the
bag 5 can be fitted snugly into the space 4. Therefore, the bag
5 can be installed even when the space is small or narrow.
Moreover, compared to the foam material filling operation or the
evacuation and sealing operation involved with the conventional
insulated containers, the manufacturing operation for the
insulated container 1 is simple, involving merely filling the
bag 5 with a gas and sealing. Therefore, manufacturing
operations for the insulated container 1 can be improved, and
since these operations are simplified, and foam material or
evacuation equipment is not required, the manufacturing cost of
the insulated container 1 can be reduced.
With the insulated container 1 of this em~bodiment, a single
bag 5 is accommodated in the space 4 between the inner wall 2
and the outer wall 3. However this bag 5 may be made from a
plurality of layers. By having such a construction with layers
of bags 5, convection and thermal radiation of the gas in the
bag can be m;nim;zed. As a result, the insulation performance
of the bag can be improved. When the construction involves a
plurality of bags, the respective bags may be filled with gas
from a single gas inlet 5c. Moreover, in order to prevent
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convection of the gas, the thickness of the bags in the
respective layers should be made less than 5 mm. Furthermore,
an insulating material having multi-layered pleats on the inside
to prevent convection may be used for the bag 5.
Second Embodiment
FIG. 5 shows an example of an insulating material of the
present invention in the form of an insulating panel 11. The
insulating panel 11 is constructed by inserting between the
walls of a double walled casing 12 made of a synthetic resin, an
insulating material 15 comprising a bag 13 made from a film
having gas barrier properties which has been filled with a gas
14 of a thermal conductivity less than that of air. Moreover
urethane foam 16 is filled into the spaces in the insulating
panel 11, between the insulating material 15 and the inner face
of the double walled casing 12. Furthermore, multi-layered
pleats 17 for preventing convection are provided on the inner
face of the bag 13 of the insulating material 15.
The bag 13 can be made from a synthetic resin film, a metal
laminated synthetic resin film, or a metal vapor deposited
synthetic resin film. The material of the synthetic resin film
will preferably have a low gas radiation amount and gas
permeability, and a high rigidity. For example, it may be
selected from materials such as polypropylene, polyethylene-
terephthalate, polyester, polycarbonate, polystyrene, rigid PVC,
polyamide and the like. The thickness of the synthetic resin
film is preferably from 0.05 - 1.0 mm. With the metal laminated
film, this is made by laminating a metal foil such as aluminum
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foil with a synthetic resin film. With the metal vapor deposited
synthetic resin film, this is made by vapor depositing a metal
such as alllm;nl1m onto a synthetic resin film.
The gas 14 which is filled into the bag 13, has a thermal
conductivity k smaller than that of air (2.41 x 102 W-m~1-K 1;
O C ). For this gas an inert gas such as Xenon ( k = 0. 52 x
102 W-m 1, K 1; o C ), Krypton (k = 0.87 x 102 W-m 1-K 1; o C
), Argon (k = 1. 63 x 102 W-m 1-K 1; o C ), or a mixture of
these gases may be used. Of the inert gases, Xenon, Krypton,
and Argon gas are particularly suitable since they have low
thermal conductivity and present m;n;m~l problems to the
environment.
Moreover, the thickness of the insulating material 15 is
made less than S mm. This is because if the thickness is
greater than 5 mm, there is the likelihood of convection of the
interior gas 14 resulting in a deterioration of the insulating
efficiency due to an increase in the conduction amount in the
direction of the thickness of the insulating material 15.
Moreover, if made thicker the effective improvement in
volumetric efficiency by the insulating material 15 will be
reduced.
The insulating material 15 is not limited to a single
material, and can be used as several sheets overlapped with each
other. Moreover, this can be used overlapped together with the
conventional urethane foam and polystyrene foam.
In the manufacture of the insulating panel 11, at first the
synthetic resin walls 12a, 12b are made by a suitable process
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such as injection molding and the like. Then at the time of
assembling these together to join the edges and form the double
walled casing 12, either a separately manufactured insulating
material 15, or a bag 13 which has not yet been fiIled with gas,
is inserted between the two walls 12a, 12b which are then ~oined
together as one. A gas such as Xenon is then filed into the bag
13 from a previously installed gas inlet which is then sealed to
complete the manufacture.
The bag 13 is made by attaching multi-layered pleats 17 to
one face of a synthetic resin film. Respective faces of two
layers of film having the multi-layered pleats 17 are then
positioned so as to face each other, and the peripheral edges of
the film heat sealed together.
The insulating panel 11 constructed in this manner, can be
used as an insulating material for various types of heat or cold
ret~;n;ng containers such as a cooler box, or an insulated lunch
box, as well as an insulating material for use in various types
of structures such as general houses and buildings.
When a gas of an extremely low thermal conductivity such a
xenon is used as the gas filled into the insulating panel 11,
then an equivalent or greater insulating performance can be
obtained compared to the conventional urethane foam insulation,
with approximately half the thickness. Therefore, the thickness
of the insulation portion can be reduced, resulting in a thin
type light weight insulating panel.
Moreover by making the thickness of the insulating material
less than 5 mm, and providing convection inhibiting multi-layer
pleats on the inner walls of the film of the bag, the insulating
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performance of the bag can be improved due to m;n;m~l gas
convection inside the bag.
The present embodiment is constructed with the insulating
material 15 inserted inside the double walled casing 12 made of
a synthetic resin to form a panel shaped insulating panel 11.
However the invention is not limited to this arrangement, and
can also be applied to double walled structures and multi-walled
structures of various shapes. Moreover, the bag 13 and the
insulating panel 11 can be used overlapped in two or more
layers. While this will result in an increase in thickness, the
insulating performance will be appreciably increased.
