Patent Application
20080078771
In the accompanying drawings:
Examples of an insulated container according to an embodiment of the present invention are illustrated in
In order to achieve the structure, according to the present invention, the sheet-like laminated film 3 is directly thermally welded to a liquid inlet/outlet 5 of the internal container 1 so as to maintain a vacuum state of the heat insulating layer. At a triple point at which two laminated films 3 and the internal container 1 are in contact with each other, a gap is liable to be formed, which makes it difficult to maintain the vacuum state. For this reason, in the present invention, the filler 6 is used to enable thermal welding without forming the gap. The filler 6 is produced using a thermoplastic resin, which is made of the same material as or a different material from an adhesive layer 11 of the laminated film 3 and is melted at the time of thermal welding to fill in the gap. And the filler 6 is formed as a protrusion obtained by processing the joint section 7 of the internal container 1; or is obtained by joining, to the joint section 7 of the internal container 1, a structure which is made of a different material and is capable of controlling generation of the gap.
Next, the internal container 1 whose material is made of a metal or a resin is used. In view of heat insulating properties, the internal container 1 is desirably made of a metal having a large heat capacity, and particularly, the internal container 1 is desirably made of stainless steel having low heat conductivity. However, in a case where manufacturing costs have to be further reduced, or the internal container whose shape is difficult to make of a metal, the internal container 1 can be made of a resin. The resin is selected and used from the group consisting of acrylonitrile butadiene styrene copolymer (ABS), acrylonitrile styrene copolymer (AS), EEA resin (EEA), epoxy resin (EP), ethylene vinyl acetate polymer (EVA), ethylene vinyl alcohol copolymer (EVOH), liquid crystal polymer (LCP), MBS resin (MBS), melamine formaldehyde (MMF), polyamide (PA), polybutyrene terephtalate (PBT), polycarbonate resin (PC), polyethylene (PE), polyethylene terephatlate (PET), tetrafluoroethylene perfluoroalkyl vinyl ether polymer (PFA), plyimide (PI), polymethylmethacrylate (PMMA), polyacetal resin (POM), polypropyrene (PP), polyphtalamide (PPA), polyphenylenesulfide resin (PPS), polystyrene (PS), polytetrafluoroethylene (PTFE), polyurethane (PU), polyvinyl alcohol (PVA), polyvinyl chloride (PVC), and polyvinylidene chloride (PVDC). However, because the resin has larger gas permeability than a metal, in a case where the resin is selected as the material of the internal container, a gas barrier layer is desirably formed to control the gas permeability, and a metal layer is suitably formed by plating. As a result, a degree of vacuum of the vacuum heat insulating layer can be maintained for a long period of time.
The thickness of the laminated film according to the embodiment of the present invention is not particularly limited as long as the laminated film can be produced without any inconveniences. For example, the thickness may be set to 45 to 120 μm, and preferably 60 to 100 μm.
A gas permeation rate of the laminated film according to the embodiment of the present invention is not particularly limited as long as the degree of vacuum of the insulated space can be maintained during a desired time period. For example, the oxygen permeation rate, which is measured using JIS-K7126-1, may be 1.1×10−11 m3/m2·s·MPa or lower, and preferably 1.1×10−12 m3/m2·s·MPa or lower.
In the embodiment of the present invention, a decompressed space formed in an insulated space is controlled to be a pressure lower than the atmospheric pressure (decompressed state) so as to improve heat insulating properties. For example, the pressure may be set to 0.01 to 100 Pa, and preferably 0.1 to 10 Pa.
A known insulating material can be used as an insulating material to be included in the insulated space. Examples of the insulating material include an organic porous body such as polystyrene foam, a compact including ceramic powder such as calcium silicate, silica, or alumina, and an inorganic fibrous insulating material made of glass wool, rock wool, or a ceramic fiber. In particular, it is desirable to use glass wool which has an average fiber diameter of 5 μm or smaller, and whose adsorption moisture is removed in a high temperature atmosphere. The insulating material may be used singly, or a combination of two or more insulating materials may be used.
When the heat insulating layer is used for a long period of time, there is a fear that the degree of vacuum will be lowered by a gas generated from the heat insulating material 2, a gas permeating the resin of the joint section, or the like. In order to prevent lowering of the degree of vacuum, it is necessary to use an adsorbent 4 for adsorbing the gas provided inside the heat insulating layer. It is desirable to use, as the adsorbent 4, calcium oxide which mainly adsorbs water, a barium-lithium alloy which mainly adsorbs oxygen and nitrogen, and cobalt oxide which mainly adsorbs hydrogen. In a case where the adsorbents are individually used to be provided in the heat insulating layer, there arises a problem in that the barium-lithium alloy adsorbs water generated from the heat insulating material, and a capability of adsorbing hydrogen and nitrogen is lowered, which is not intended in the present invention. Therefore, it is suitable to employ a three-layered structure (not shown) including a barium-lithium alloy layer serving as an intermediate layer, a calcium oxide layer, and a cobalt oxide layer.
In order to thermally weld the laminated film 3 to the internal container 1, there is used a sealer which is formed into the shape of the liquid inlet/outlet 5 which corresponds to the joint section 7 of the internal container 1. In the case of using the internal container 1 made of a metal, a sheet made of the same material as the adhesive layer 11 is desirably wound around the internal container joint section 7 in advance so that the adhesive layer 11 can be thermally welded to the internal container joint section 7 with ease and a distance between the internal container 1 and an aluminum foil serving as the gas barrier layer 10 is increased to thereby increase a heat resistance of the joint section 7. In this case, the heat resistance is increased as an amount of sheet to be wound becomes larger. However, because an amount of gas permeating the resin of the adhesive layer 11 is increased according to a thickness of the sheet, the amount of sheet to be wound is desirably 50 μm or less.
In addition, at the triple point at which two laminated films 3, 3 and the internal container 1 are in contact with each other, a gap is liable to be formed. Accordingly, the filler 6 is desirably provided thereto in advance. As described above, the filler 6 is obtained by: joining a rod made of the same material as the adhesive layer 11 of the laminated film 3 to the joint section 7; joining a rod made of the same material as the internal container 1 to the joint section 7; or joining a protrusion obtained by processing the joint section 7 of the internal container 1 or a rod made of a different material to the joint section 7 (see
The glass wool 2 is wound around the internal container 1 to which the filler 6 is formed. The amount of the glass wool 2 to be wound in this case is determined depending on a thermal insulating performance required for the insulated container (which will be described in detail in Example 2).
As illustrated in
The sealer has a high heat-resistance rubber 12 made of fluorine which is molded into the shape of the joint section, and includes a ribbon-like metal heater 13 and a glass cloth 14 that are provided on the high heat-resistance rubber 12. As heat-sealing conditions for the sealer, a state where the laminated films 3 are pressed onto the internal container 1 is maintained for 6 seconds or more at a temperature which is 20° C. higher than a melting point of the adhesive layer 11. Note that, in a case of using the internal container 1 made of a metal, the heat conductivity and the heat capacity of the internal container 1 are large when only the heater of the sealer is used. This makes it difficult to set the temperature of the laminated films 3 at the internal container joint section 7 to be equal to a fusion bonding temperature of the adhesive layer. Accordingly, it is necessary to preheat the internal container joint section 7 by using an auxiliary heater (see
The internal container 1 and the laminated films 3, 3 are heat-sealed, and then both surfaces of the laminated films 3, 3 are thermally welded. Also in this case, in the same manner as described above, the state where the laminated films 3, 3 are pressed onto the internal container 1 is maintained for 6 seconds or more at a temperature which is 20° C. higher than the melting point of the adhesive layer 11. The both surfaces of the laminated films 3, 3 are heat-sealed to form the laminated films 3, 3 into a bag shape. After that, the getter material 4 serving as a gas adsorbent is filled therein.
In this state, the container thus obtained is put in a vacuum chamber, and an interior of the chamber is evacuated and internal pressure thereof is set to 10 Pa or lower. A bottom portion of the container, which is the remaining side to be sealed, is heat-sealed under the above-mentioned conditions to form the vacuum heat insulating layer. The interior of the chamber is evacuated so that the heat conductivity of the heat insulating material is lowered, and an amount of heat radiated from the interior of the insulated container is reduced. The heat propagating in the interior of the fiber heat insulating material is a sum of heat propagating through a gas, heat propagating through a solid, and heat propagating by means of radiation. The internal gas is eliminated by decompression, thereby suppressing the heat propagating through the gas, lowering the entire heat conductivity, and reducing the radiated heat amount.
An example of a manufacturing method for the insulated container according to the present invention will be described in detail below, but the present invention is not limited thereto.
As the internal container 1, there was used a rectangular parallelepiped container which was made of polyethylene and had an internal volume of about 2.6 L and a coating thickness of 8 mm. On one surface of the internal container 1, the liquid inlet/outlet 5 having an outer diameter of 18.5 mm, an inner diameter of 13 mm, and a height of 30 mm was provided. In addition, at a position of the liquid inlet/outlet 5, which was 10 mm apart from an upper surface of the liquid inlet/outlet 5, the filler 6 made of a polyethylene resin having a height of 10 mm as illustrated in
As the covering material 3, there was used a laminated film having a multi-layer structure including a polyethylene terephatlate layer (having a thickness of 12 μm) serving as the protective layer 8, a nylon layer (having a thickness of 15 μm) serving as the protective layer 9, an aluminum foil (having a thickness of 6 μm) serving as the gas barrier layer 10, and a polyethylene resin layer (having a thickness of 50 μm) serving as the adhesive layer 11.
White wool manufactured by ASAHI FIBER GLASS Co., Ltd. was used as the fiber heat insulating material 2, and COMBO3GETTER manufactured by SAES Getters was used as the gas adsorbent 4 (getter material).
Around the container made of polyethylene serving as the internal container 1, the glass wool was coated with a thickness so as to reach a position of the lower surface of the filler 6 provided to the liquid inlet/outlet 5 of the internal container 1. The density of the glass wool in this case was about 0.25 g/cm2 with respect to a surface area of the internal container 1. Next, the adhesive surfaces of two laminated films serving as the covering materials 3 are positioned to face the fillers 6 provided to the liquid inlet/outlet 5 of the internal container 1. Then, the position of the joint section 7 was adjusted so as to obtain the temperature of 160° C with the sealer as illustrated in
After the water was evaporated, the container thus contained was carried in the chamber with an argon atmosphere, and one getter material (about 7 g) serving as the gas adsorbent 4 was provided from the bottom portion at which the covering material 3 was opened, and then the interior of the chamber is decompressed to 10 Pa. Then, the opened portion of the covering material 3 was joined to be sealed by using a heater provided in the vacuum chamber. In this manner, the insulated container having a vacuum heat insulating layer having a thickness of 10 mm was produced. The method described above is Example 1.
Hot water of about 100° C. was poured into the insulated container according to Example 1, was left for about 10 minutes, and then displaced. The hot water of about 100° C. was poured into the insulated container again, a thermocouple was inserted from the liquid inlet/outlet, and the liquid inlet/outlet was closed with a rubber stopper. By setting a time point at which the water temperature within the insulated container became 95° C. as a start, the water temperature was continuously measured for 12 hours.
According to Comparative Example 1, there was employed an insulated container having a duplex tube structure made of a metal, in which a stainless plate having a thickness of about 0.5 mm is used for the internal container and the external container, and a vacuum heat insulating layer was provided between the internal container and the external container. The liquid inlet of the insulated container according to Comparative Example 1 has an insulation structure with a cover material, which suppresses radiation of heat from the liquid inlet. Hot water of about 100° C. with the same volume as Example 1 was poured into the insulated container according to Comparative Example 1, left for 10 minutes, and then discharged. Hot water of about 100° C. was poured into the insulated container again, the thermo-couple was inserted in the insulated container, and then the liquid inlet was closed. By setting a time point at which the water temperature within the insulated container became 95° C. as a start, the water temperature was continuously measured for 12 hours.
Measurement results according to Example 1 and Comparative Example 1 are shown in
In Example 1, the hot water of 95° C. (contained in the insulated container according to the present invention) was maintained at about 83° C. after the hot water was left for 12 hours, while in Comparative Example 1, the hot water of 95° C. was maintained at about 78° C. after the hot water was left for 12 hours. As a result, it has been proved that the insulated container according to Example 1 has a heat insulation property equal to or higher than that of Comparative Example 1. It should be noted that, in the insulated container used in Comparative Example 1, which has a duplex tube structure made of a metal and is a commercially available thermos type container, the internal container and the external container are each formed of a stainless steel plate having a thickness of about 0.5 mm, and a vacuum heat insulating layer is provided between the internal container and the external container. In addition, the liquid inlet of the insulated container according to Comparative Example 1 has the insulation structure, which suppresses radiation of heat from the liquid inlet.
Next, a specific example in which the amount of the glass wool 2 to be wound is determined based on the heat insulating performance required for the insulated container will be described as Example 2.
For example, water of 95° C. was poured into each of insulated containers respectively including a vacuum heat insulating layer having a winding amount of 0.25 g/cm2 with a thickness of 10 mm, a vacuum heat insulating layer having a winding amount of 0.13 g/cm2 with a thickness of 5 mm, and a vacuum heat insulating layer having a winding amount of 0.38 g/cm2 with a thickness of 15 mm, and the insulated containers were left for 12 hours to measure the water temperature thereof. As a result, the water temperature of the insulated container with the thickness of 5 mm was about 70° C., that of the insulated container with the thickness of 10 mm was about 78° C., and that of the insulated container with the thickness of 15 mm was about 82° C.
Example 3 shows examples of combinations of the materials for the insulated container according to the present invention, but the present invention is not limited thereto.
In addition, the insulated container according to the present invention can be used as an insulated container such as an electric pot, or a cold-insulation container for liquid gas or the like.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-266038 | Sep 2006 | JP | national |
| 2007-163023 | Jun 2007 | JP | national |
