Supports: cabinet structure – Spaced insulated wall – Refrigerator cabinet
Reexamination Certificate
1999-01-11
2001-10-23
Cuomo, Peter M. (Department: 3624)
Supports: cabinet structure
Spaced insulated wall
Refrigerator cabinet
C220S592090
Reexamination Certificate
active
06305768
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
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.
2. Description of the Related Art
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.
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.
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.
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
).
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
).
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
).
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
).
When a package and documents pertinent to the obtained product are prepared and added, the production is completed (step
6
).
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.
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.
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.
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.
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.
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
17
a
, sealing pressure devices
18
, and a vacuum control valve
16
as shown in FIG.
20
. While a vacuum state is maintained, end edge portions
12
a
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
−2
torr when the end edge portions
12
a
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.
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.
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 (
Anderson Jerry A.
Cuomo Peter M.
Mitsubishi Denki & Kabushiki Kaisha
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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