Electric heating – Inductive heating – With heat exchange
Reexamination Certificate
2000-12-29
2002-03-19
Pelham, Joseph (Department: 3742)
Electric heating
Inductive heating
With heat exchange
C219S601000, C099SDIG014
Reexamination Certificate
active
06359268
ABSTRACT:
The invention relates to a method according to the precharacterizing clause of claim
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, correspondingly designed devices for carrying out this method and receptacles for heating meals by this method, it being possible to carry out a wide variety of application areas in the catering industry, such as for example the holding of banquets, serving of meals in public establishments, such as hospitals and care homes in particular, and also the serving of meals in vehicles, in particular on aircraft.
The invention is based on the method and device for heating food described in DE 27 11 088, in which the heating of the food located in closed containers takes place by means of induction heating of conducting elements in the containers.
In the case of the solution described there, the use of special food receptacles is generally necessary, as is also the case elsewhere for the inductive heating of food. The use of special kitchenware or, as likewise specified in DE 27 11 088, specially fitted-out containers or trays, the increased cost aspect of which is not generally justified, has also generally only been accepted rarely by users up until now.
Furthermore, the heating which can be achieved by induced eddy currents takes place in the known systems exclusively by means of heat conduction, convection and radiation, which, in particular in the case of convection and radiation, is hindered by the medium surrounding the food to be heated, air, so that increased time spent and reduced efficiency have to be accepted.
A further disadvantageous aspect to be noted in the case of this known solution is that it is necessary for the effectiveness of this method that the distance between the induction coils and the metallic parts actually to be heated of the containers which are intended for accommodating the food and are to be heated and their positioning are set optimally. For this purpose, a complicated mechanism is proposed there, with which the elements accommodating the induction heating coils can be set appropriately before the heating operation, at least in their height.
In particular on aircraft, it is customary to provide conventional ovens which are operated by resistance heating and with circulating air for the heating of meals. The relatively low efficiency of these known ovens results in a great expenditure of time and energy being required, which has extremely disadvantageous effects in this sector in particular. The ovens, normally standardized in their dimensions, must be manually loaded with the containers, which may also include conventional tableware, in a relatively laborious way and be heated appropriately to the desired temperature over a time period of about 20 minutes and then removed again individually, assigned individually to trays and the fully loaded trays introduced into insulating carts and transported by them to the individual passengers, where they are handed out.
Since the various catering companies also use different receptacles of different materials and in different dimensions, there may be further increased energy consumption and not optimum utilization of the space available in the ovens used there.
It is therefore the object or the invention to specify a possible way of heating prepared meals in a short time, to the extent that they are suitable for consumption, with low expenditure, in a highly effective manner and with good quality.
This object is achieved according to the invention by the features of patent claim
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. Advantageous refinements and developments of the invention emerge from the features contained in the subordinate claims.
In the invention, it is important in particular that the heating of the items of food or meals, if at all, by convection, induction or heat radiation is achieved at least also additionally by hot steam. In this way, not only can the effectiveness, i.e. the efficiency, be improved and the heating time reduced, but a regeneration of the prepared meals can also be achieved, having positive effects not only in terms of improving the esthetic appearance but also in terms of flavor.
For this purpose, one possible way of proceeding is that the steam is generated directly in a device with which the meals are to be heated or externally generated steam is introduced in an apportioned manner into such a device and, in the latter case, the temperature is maintained at an adequate level with the aid of induction, so that condensation of the steam during the heating phase can be avoided. Another possible way is that the steam is generated directly in the device during the heating, the temperature being chosen in both cases such that hot steam can be used for heating the meals.
In the most favorable case, the steam can be generated with the aid of the induction heating coils, so that it is possible to dispense with other heating systems or elements.
In a favorable way, the receptacles in which the meals to be heated are contained are placed into a corresponding device and positioned with respect to the induction heating coils, it being possible for particularly favorable induction heating coils for heat from above and below to be arranged above and below such a receptacle which contains meals to be heated.
Since, according to the invention, virtually any receptacles are to be used, in other words it is not necessary to resort to special kitchenware, it is favorable the eddy currents in electrically conducting materials (preferably ferro- or paramagnetic), which in the form of foils, foil parts or metal sheets favorably constitute part of such a heating device or of push-in containers, which will be discussed in more detail later.
In this case, the metallic sheet-like elements generally to be used in particular for the heat from above may be of a slotted or plastic-coated form, allowing an automatic regulation of power, and accordingly also the temperature, an increase in the corrosion resistance and/or heat emitting capacity.
The sheet-like elements in which the required heat for the heat from below is to be generated by induction may also be advantageously used for the generation of the steam. In this case, these parts may be designed in specific regions in such a way that they can take the water for the steam generation required for the heating and regeneration of the meals and may be designed for example in a channel-like manner and, particularly advantageously, in an annular manner around the respective receptacle.
Such foils or metal sheets may be surface-treated, in order on the one hand to improve their heat emitting capacity and on the other hand to form a corrosion protection.
In this case, the foils or metal sheets may be arranged such that they are individually assigned to an induction heating coil, or else one such element is assigned to a plurality of such coils.
There is also the possibility of using an additional induction in the receptacles containing the meals, in which such a receptacle is enclosed by a ring of a material suitable for this purpose, which can concentrate the field in the direction of the receptacle base.
It must be noted that the sheet-like element responsible for the heat from below in some, cases can absorb only certain parts of the field, if it consists for example of a relatively unfavorable material, is slotted or does not have an adequate thickness for a full skin depth, so that the remaining proportion is transferred into the base of the receptacle.
A further possibility which can be used with the solution according to the invention is that of using receptacles closed by lids, the lids consisting of an electrically conducting material, for example metal, and it being possible for them to be designed in a way similar for example to yoghurt pots. In this case, the upper edge of the receptacle and/or the lid may be designed in such a way that these receptacles can be placed or hung in a frame-shaped element, and the heating can consequently be carried out in a corresponding device. In this case, the latching of the frame-shaped element and the size of the receptacles can be optimally adapted to the
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