Electric heating – Microwave heating – With control system
Utility Patent
2000-02-28
2001-01-02
Leung, Philip H. (Department: 3742)
Electric heating
Microwave heating
With control system
C219S700000, C219S746000, C219S748000, C219S761000
Utility Patent
active
06169277
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention resides in an apparatus for heating foods particularly in an air plane wherein the foods are disposed, ready to be served, on a tray and are moved on the tray through a heating apparatus for heating the food on the tray to 50 to 55° C. before it is served to the passengers.
The hot meals on airplanes are heated today in hot air ovens, in induction ovens or in microwave ovens. However, the apparatus in use are not suitable for a rapid, homogeneous and spacially selective heating of the foods. DE 195 25 878 C1 discloses, for example, a vertical conveyor for the transport of foods on an airplane with two belt systems which move in opposite directions and which engage menu boxes by way of strip-like engagement members extending transversely to the belts. At least one heating apparatus is provided. This apparatus consists essentially of at least one packet of heat inductors, which are pivotable around a vertical axis and which each includes an induction coil and can be pivoted into, an out of, spaces between the menu boxes.
It is the object of the present invention to provide an apparatus for the selective heating of foods by which a multitude of menus can be heated properly and immediately before serving in order to provide for an as uniform as possible supply of the food to all the passengers especially of a jumbo jet.
SUMMARY OF THE INVENTION
In an apparatus for the selective heating of foods disposed on a serving tray to serving temperature by means of a microwave oven having a gyrotron as a heat source, individual guide means are provided for guiding the microwave radiation individually to particular dishes on the tray and a control computer for controlling the radiation of, and the heat generated in, the dishes during passages of the tray with the dishes through the microwave oven.
With the method according to the invention the foods can be heated to predetermined serving temperatures in a fast, selective and uniform manner whereby not only the processing times and the energy consumption can be substantially reduced but, at the same time, the quality of the menu being served can be improved. The microwaves used in a preferred embodiment of the invention for heating the food have preferably a frequency greater than about 24 GHz, that is, they are much above the plane-related aviation frequency so that air plane traffic is not disturbed by the microwave ovens. The used millimeter waves provide for good coupling of energy into the foods. The radiation enters the foodstuff directly from the outside without any bypasses. The food particles are subjected to vibrations, whereby heat is generated by friction within the foodstuff itself so that all the food irradiated is heated. Heating occurs in seconds. A rapid automatic heating of the meals in jumbo jets can therefore be achieved without problems.
In a further embodiment according to the invention, which is particularly advantageous, the foodstuff on the tray can be selectively heated by a computer-controlled focussing of the beam-guided high frequency microwaves generated by the gyrotron in the microwave oven. That is, if the tray contains various foods requiring different heating, they can be selectively heated to the desired temperature while other foodstuff is not heated at all.
In further embodiments of the invention, the microwave oven is part of a processing line, which extends through the microwave oven and includes means for homogenizing the heated food on the tray. The processing arrangement may include additional microwave ovens for treating the food on the trays by high-frequency millimeter waves by means of at least one hollow conductor system for uncoupling the waves. (The walls of the hollow conductor systems are coated so as to absorb any scattered radiation). The radiation is piped by the hollow conductor system directly to the respective dishes using a mirror system including at least one mirror, whereby the foods on the tray can be very selectively heated. The trays may have reflection layers below the dishes to be heated so that any microwaves passing through the dishes are reflected back into the dishes. Sensors for determining the temperature of the respective dishes may also be provided. The control computer preferably reads the desired food temperature from bar codes so that the heating of the dishes can be automatically controlled in a menu-specific manner. By way of the control computer, the optical axis and the focussing properties are adjustable by adjustment means for the mirrors as well as the focussing properties of the beam to be coupled into the food.
Below, the invention will be described in greater detail on the basis of the accompanying drawings.
REFERENCES:
patent: 3867606 (1975-02-01), Peterson
patent: 4839485 (1989-06-01), Koch et al.
patent: 4963709 (1990-10-01), Kimrey, Jr.
patent: 5245150 (1993-09-01), Grandi
patent: 9-112873 (1997-05-01), None
patent: WO 99/18758 (1999-04-01), None
Feher Lambert
Schnack Manfred
Schnack Sven
Bach Klaus J.
Forschungszentrum Karlsruhe GmbH
Leung Philip H.
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