US20100108694A1

US20100108694A1 - Heat-insulating container

Info

Publication number: US20100108694A1
Application number: US11/993,615
Authority: US
Inventors: Klaus Sedlbauer; Herbert Sinnesbichler
Original assignee: Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
Current assignee: Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
Priority date: 2005-06-23
Filing date: 2006-06-22
Publication date: 2010-05-06
Also published as: ATE510479T1; EP1893068B1; EP1893068A1; DE102005030310B3; ES2365411T3; WO2006136459A1

Abstract

The invention relates to a heat-insulating container with a surrounding wall (5, 6) that encloses a space for holding foodstuffs or beverages, whereby latent heat storage material (4) is accommodated inside the surrounding wall. A lightweight supporting structure (7) is placed between an inner (5) and an outer (6) casing, which form the surrounding wall, and the supporting structure is filled with the latent heat storage material (4).

Description

The invention relates to a heat-insulating container according to the preamble of the main claim.
Heat-insulating containers are known in the art such as from document EP 1 452 459 A1.
From document DE 199 32 872 A1, a foodstuff box provided for foodstuff distribution is known, which comprises an external container consisting of a bottom portion and a cover portion as well as a dinner dish having a meal hollow for the accommodation of a meal, and which can be inserted into the external container. The dinner dish is provided with a storage chamber in which storage material is arranged such that it is immediately in contact with the meal hollow of the dinner dish. The storage material includes a plurality of latent heat storage components having different transition temperatures. Thus, it is achieved that a part of the released latent heat can be used at a temperature above a defined cooking point of 85° C. for re-cooking the food, whereas another part of the released latent heat at a temperature below the cooking point is used for heat retaining.
It is not explained anything else about the structure of this dinner dish, obviously the dinner dish has to remain inside the bottom portion otherwise stability is not secured.
A container according to the preamble of the main claim which can only be realized with a relatively high weight, however, is shown in DE 198 19 008 A1 as well.
The invention is based on the object to provide a heat-insulating container usable as tableware for receiving foodstuff or beverages, which shows a good heat insulation with adaptation of the temperature conditions, wherein it should ensure a good stability with a weight of commercially available ceramic tableware.
This object is solved according to the invention by the characterizing features of the main claim in combination with the features of the preamble.
As a result of placing a lightweight supporting structure filled with latent heat storage material between an inner casing and an outer casing forming a surrounding wall of the container, a container having good heat insulation is provided which shows a particular strength, wherein the wall thickness of the container can be rather minimized by means of the braced supporting structure, and the proportion of heat storage material related to the total volume can be maximized. As a result, the container is not heavier than conventional tableware.
By providing measures indicated in the dependent claims, advantageous developments and improvements are possible.
For a better heat transfer into the latent heat storage material, the surrounding walls of the lightweight supporting structure formed as a grid pattern or honeycomb pattern, respectively, are made of thermally highly conductive material. The grid, mesh, honeycomb or other chamber patterns form cavities or chambers which are filled with latent heat storage material. At the same time, the supporting structure can be made from cardboard, plastic material or metal, in which the surrounding walls themselves of the supporting structure can be formed as grids.
In an advantageous manner, the grid and honeycomb pattern, respectively, is partially provided with an insulating plastic material layer in order to prevent an increased heat transfer towards the outside of the tableware. Optionally, an insulating layer can be additionally deposited upon the outer casing.
In an advantageous manner, the transition point and the transition points, respectively, are selected such that it and they, respectively, are adapted to the use of the foodstuffs or beverages as directed.
The mass of the heat insulating material in proportion to the mass of the casing and the lightweight supporting structure should be such as greater than 6, preferably greater than 8, preferred greater than 10, if possible.

An embodiment of the invention is shown in the drawing and will be explained in more detail in the following description, in which:

FIG. 1 shows a sectional view through the container according to the invention;

FIG. 2 shows a view of the structure of the container according to the invention in more detail; and

FIG. 3 shows a view of the lightweight supporting structure which is used in the container according to the invention.

In FIG. 1, the container according to the invention is shown in the form of a heat-insulating cup 1 which holds a liquid 2, for example. A surrounding wall 3 made of plastic material, paper, metal or composite material encloses latent heat storage material, e.g. paraffin waxes, which has a transition point being adapted to the respective eating and drinking temperature, respectively, according to the intended purpose. If, for example, hot coffee is poured into such a cup 1 having a latent heat storage material, the transition point of which is at appr. 45° C., then a phase change from solid toward liquid is occurring, wherein the heat is accumulated in the storage materials. Because of this, the temperature of the coffee is decreasing to a drinking level, e.g. 45° C., and subsequently the coffee is longer maintained at the temperature of the transition point due to the heat reserves in the storage material, wherein the latent heat storage material is slowly solidifying by the heat release toward the coffee. Thus, rapid cooling will be efficiently reduced. With hot soups, for example, the transition point is allowed to be at 70° C. This effect can also be applied with cold beverages or foodstuffs, wherein the transition point of the latent heat storage material is accordingly to be selected lower, e.g. 10° C.
In FIG. 2 and FIG. 3 the inner structure of the cup 1 is illustrated in more detail. The cup 1 comprises an inner casing 5 and an outer casing 6 between which a lightweight supporting structure 7 is placed, wherein the latter in the embodiment of the honeycomb pattern is provided with thin partitions 8. The blank cavities between the thin walls 8 are completely filled with latent heat storage material 4 such that the cup 1 is substantially made of this storage material 4. The honeycombs, i.e. the walls of the honeycomb pattern, consist e.g. of plastic material, metal, paper or similar, and are integrated both in the bottom area and the circumferential wall of the container 1, and are entirely enclosed by the storage material 4. The particular strength is achieved by the hexagonal honeycomb pattern 7.
The thin walls 8 of the lightweight supporting structure which can also be formed themselves as grids are made of a thermally highly conductive material, wherein the area of the walls, which faces to the outside of the container, is additionally provided with a casing of heat-insulating material 9 such as a coating for preventing an increased heat transfer towards the outsides.
The inner casing 5 and outer casing 6, for example, represent a thin coating which protects the latent heat storage material 4 on the surface. On the outer casing 6, an insulating layer can be additionally deposited, if desired.
In the following, a coffee cup is determined as an example, which has a usable volume of about 0.25 litres being defined by a diameter of 8 cm and a height of 9 cm. If, for example, coffee having an assumed temperature of 100° C. is poured herein which is to cool down to a drinking level of appr. 45° C. by means of latent heat being storable in the storage material, for this purpose quantity of energy of 48 kJ has to be stored by means of the phase transition inside the casing. A possible storage material to be used is organic C17-C28 type paraffin wax having a melting point of 42 to 44° C. and organic C20-C33 type paraffin wax having a melting point of 48 to 50° C., respectively, with a specific melting enthalpy of 189 kJ/kg each. For storing the necessary energy quantity of 58 kJ, per cup 0.31 kg of storage material is required. A commercially available ceramic cup including the indicated sizes has a mass of appr. 0.35 kg. So that the coffee cup according to the invention having the storage material will be not heavier than conventional tableware, the supporting structure for stabilizing the molten storage material is allowed to merely increase the total mass insignificantly. This will be achieved, e.g. using the thin hexagonal honeycomb pattern 8.
Expressed more generally, the object based on the present invention to provide a container as lightweight as possible by means of which foodstuffs or beverages can be maintained at a desired temperature as long as possible, is solved by a heat-insulating container with a surrounding wall which encloses a space for the accommodation of foodstuffs or beverages, in which latent heat storage material is received, wherein between an inner and an outer casing forming the surrounding wall, a lightweight supporting structure connecting the inner casing to the outer casing is placed, which is filled with the latent heat storage material. At the same time, the mentioned lightweight supporting structure preferably comprises braces and/or walls which connect the outer casing with the inner casing.
Such walls can be realized as continuous walls so that the chambers or cavities formed by the lightweight supporting structure between the casings are completely separated from each other by means of which a particularly good support of the container will be achieved. The walls, however, can also be realized in an open-worked manner so that the chambers or cavities formed by the lightweight supporting structure are not completely separated from each other. Because of that, the weight of the container can still be further reduced. There is preferred an embodiment of the invention, in which a plurality of chambers are formed by means of a plurality of walls arranged between the inner casing and the outer casing and connecting the inner casing with the outer casing, which as already said are allowed to be completely separated from each other or else connected to each other due to apertures of the mentioned walls.
In the outlined manner it can be achieved without any problems that the ratio of the mass of the latent heat storage material and a mass formed by the lightweight supporting structure having the inner casing and outer casing is greater than 2, or advantageously greater than 4. Particularly preferred are embodiments, in which this ratio is greater than 6, more preferably greater than 8 or greater than 10.

Claims

1. A heat-insulating container with a surrounding wall, which encloses a space for holding foodstuffs or beverages, whereby latent heat storage material is accommodated within said surrounding wall, characterized in that, a lightweight supporting structure (7) filled with said latent heat storage material (4) is placed between an inner casing (5) and an outer (6) casing forming said surrounding wall.

2. A container according to claim 1, characterized in that said lightweight supporting structure (7) is formed as a grid pattern or honeycomb pattern, the cavities of which are filled with said latent heat storage material.

3. A container according to claim 1, characterized in that the ratio of the mass of said latent heat storage material to the mass of said casing and of said lightweight supporting structure is greater than 6, preferred greater than 8, preferably greater than 10.

4. A container according to claim 3, characterized in that said casing consists of plastic material, metal and/or composite material.

5. A container according to claim 1, characterized in that the outside of said container comprises an insulating layer in addition to the further insulation.

6. A container according to claim 1, characterized in that said latent heat storage material is a paraffin wax mixture.

7. A container according to claim 1, characterized in that said latent heat storage elements have a transition point of between 0 and 70° depending on the intended purpose.

8. A container according to claim 1, characterized in that said lightweight supporting structure filled with said latent heat storage material is provided with coatings forming said casing.

9. A container according to claim 1, characterized in that said lightweight supporting structure (7) is made of a thermally highly conductive material, and is provided with a heat insulating layer towards said outer casing.

10. A container according to claim 1, characterized in that said latent heat storage material consists of microencapsulated storage elements.

11. A container according to claim 1, characterized in that said grid or honeycomb pattern is made of cardboard, metal and/or plastic material.