Patent Application
20100275640
The invention relates to a refrigerator according to the pre-characterizing clause of claim 1.
So-called vacuum panels have become known for different insulation purposes. These vacuum panels typically consist of an airtight outer skin which encloses a core consisting of porous insulating material. Silica or aerogels, but also open-cell foams made of polyurethane, are often used as insulating material. Said panels are evacuated and sealed. In this process the internal pressure is reduced to a value of less than 100 mbar. As a result of the evacuation the rigidity and stability of the panels is increased on the one hand, while on the other hand the insulation effect is reinforced. This effect can be explained in that the probability of collisions of the air molecules present in the pores is reduced. Depending on the core material used and the internal pressure, such vacuum panels possess a thermal conductivity in a range of 0.017 to 0.025 W/mK.
In the meantime materials called nanofoams with a pore size lying in the nanometer range have also become known, in particular for building insulation. These nanofoams are fabricated from plastic by way of synthesis. They achieve a thermal conductivity in the range of 0.010 to 0.015 W/mK and so lie far below the values of vacuum panels.
Present-day refrigeration appliances such as e.g. refrigerators, freezers or refrigerator/freezer combinations typically consist of an inner shell which is fixed in an outer housing consisting of lid, base, side walls and rear wall. After the refrigeration generator and the electrical components have been installed, the interspace between inner shell and outer housing is foamed in place. This method is relatively complex and therefore expensive.
Transportable refrigerator boxes of smaller size are already often manufactured more cheaply. Prefabricated vacuum panels which are assembled to form a corresponding housing are used to build said refrigerator boxes. Such vacuum panels must be relatively thick in order to achieve the necessary insulation. The ratio of internal to external volume is therefore unfavorable.
The object underlying the invention is to construct a refrigerator in such a way that it can be manufactured cost-effectively and at the same time a very good ratio of internal to external volume exists. This notwithstanding, it is also aimed to improve the insulating effect in comparison with conventional refrigerators or at least maintain it at an equal level.
The object is achieved by means of a refrigerator having the features recited in claim 1. According to the invention molded parts having a core consisting of nanofoam are used to insulate the interior space. The pore size of the nanofoam is less than 100 nanometers. The core is surrounded by an airtight envelope. The molded part is evacuated such that the internal pressure amounts to less than 100 mbar. Said molded parts can be joined together to form a housing and thereby delimit the interior space of the refrigerator. Equally, however, they can be mounted onto the outside of a housing and in this way form the insulation of the interior space.
In a first exemplary embodiment the molded parts are implemented as rectangular panels. Such panels can be manufactured cheaply and with high precision. By means of such panels a housing for a refrigerator can be easily constructed and assembled with little effort and at little cost.
In a further exemplary embodiment the shape of the molded part is adapted to suit the purpose of the particular application. Thus, for example, recesses for receiving shelf supports can be integrated into the molded parts. Similarly it is possible for a molded part to have a different thickness so that e.g. a freezer compartment can be integrated in the upper section of the refrigerator and the insulating effect in this region can be reinforced.
The molded part forming the base is advantageously embodied in a stepped shape. At the rear of the refrigerator there is thus created a machine bay which is accessible from the rear and in which the compressor, for example, can be housed. A similar structure can be achieved if instead of the base the rear wall is embodied in a stepped shape. In this way also the machine bay can be implemented using simple means.
According to the invention the molded parts are joined to one another in such a way that the joins have a similar thermal conductivity to the molded parts themselves. By this means thermal bridges are prevented at the joining edges of the individual molded parts. Affected by this in particular are the joins between the rear wall and the molded parts adjacent thereto which form the lid and the base, as well as the two side walls. Since the condenser, which has a high level of heat emission, is usually fixed to the rear wall, no thermal bridge into the refrigerated interior space of the refrigerator must exist, in particular at the borders of the rear wall.
In order to be able to ensure the lowest possible heat conductance value of the molded parts, their internal pressure advantageously amounts to less than 5 mbar. Particularly advantageously the internal pressure lies between 1 and 3 mbar.
In practice the internal pressure of the molded part that is relevant for the thermal conductivity cannot be kept constant. This means that at least over the course of several years the original internal pressure increases due to the diffusion of water vapor and air through the envelope of the molded part. In order to keep this increase to an absolute minimum, a metallized multilayer film is used for the envelope of the molded part.
The insulating material of the core advantageously has a pore size of less than 50 nanometers. Particularly advantageously the nanofoam has pores in the size range between 1 and 100 nanometers. At this small pore size the probability of collisions between air molecules is reduced to such a degree that even if there is a rise in the internal pressure the thermal conductivity will increase only to a small extent. In this way the refrigerator maintains an outstanding insulation capacity over its entire useful life.
Further details and advantages of the invention will emerge from the dependent claims in connection with the description of an exemplary embodiment which is explained in greater detail with reference to the drawing, in which:
The core of the molded parts consists of a porous insulating foam, called nanofoam. This open-cell insulating foam consisting of polyurethane has a pore size lying in the nanometer range, ideally around 1-10 nanometers. All the molded parts have an airtight and waterproof envelope. This consists of a metallized multilayer film. The molded parts are evacuated to an internal pressure of ideally 1-3 mbar. The metallized multilayer film can almost totally prevent the diffusion of water vapor and air into the molded part, with the result that said internal pressure is maintained for a long time. This film also prevents the formation of thermal bridges at the abutting edges of molded parts placed against one another, such that no heat can penetrate into the insulated interior space 8 at these points either.
The molded parts are joined together at the factory to form a housing in such a way that heat from outside likewise cannot reach the interior space as a result of the joining technology. This can be achieved for example by means of certain adhesives which contain no or only few heat-conducting materials.
In the exemplary embodiment shown the rear wall 3 is inserted between the lid 5 and the base 4. The side walls 2 are attached below the lid 5 but overlap the base 4 and the rear wall 3. In this way smooth, continuous side surfaces are produced against which only the lid 5 visually abuts. The side walls 2 also form the lateral delimiting surfaces for the machine bay 7. A uniform, easy-to-maintain surface is produced, also when viewed from above.
The interior space 8 delimited by the molded parts 2, 3, 4, 5 is closed by means of the door 6. The latter rests on the frame formed from the narrow sides of the molded parts 2, 4, 5. In this way an attractive, smooth front side is produced.
During the assembly of the refrigerator the narrow side of one molded part is in each case joined to the surface of another molded part. Thus, for example, a rear strip of the surface of the base 4 is joined to the bottom narrow side of the rear wall 3, while the two lateral narrow sides of the base 4 are joined to areas of the inner surfaces of the side parts 2.
The interior space 8 can, of course, also be lined with a one-piece inner shell such that the interior space has no grooves or gaps of any kind and can be cleaned easily. Similarly an outer shell can also be provided for design reasons or in order to increase stability, with the result that the refrigerator takes on the appearance of a conventional refrigerator.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2007 050 403.0 | Oct 2007 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP08/63445 | 10/8/2008 | WO | 00 | 7/7/2010 |
