Electric heating – Microwave heating – With diverse-type heating
Patent
1999-09-24
2000-11-28
Leung, Philip H.
Electric heating
Microwave heating
With diverse-type heating
219738, 219756, H05B 680
Patent
active
061538663
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a method and a device for IR irradiation of foodstuffs in a microwave oven. In particular, the present invention relates to a device and a method for the arrangement of IR radiating elements in a microwave oven.
TECHNICAL BACKGROUND AND PRIOR ART
At the present time, there are known microwave ovens which comprise grill elements, i.e. means for irradiation of foodstuffs which are to be cooked in the oven with IR radiation, in order to create a grilled texture of said foodstuffs.
The conventional method is to arrange grill elements outside the oven cavity, in a so-called grill bulge, in order to avoid creating serious disturbances of the microwave pattern in the oven cavity. However, this results in new problems since a route must be created for the IR rays into the oven cavity, which route leads to the creation of an opening in the cavity wall through which microwaves pass into the grill bulge, from where the microwaves can leak out into the surrounding room.
In order to avoid such leakage a solution has been created, which is presented in EP 0 420 319. The invention defined in this patent aims to prevent the microwave field present in the grill bulge from leaking out into the surrounding room. In order to achieve this, measures are taken in two steps: the first step is the arrangement of a perforated metal sheet in the opening of the cavity wall so that this sheet physically shields the grill bulge from the cavity. Even though this shield shields off some of the microwaves, the resulting field in the grill bulge is still relatively strong, which causes problems with radiation leakage to the surrounding room. The second step is that in order to prevent this leakage to the surrounding room, one has attempted to insulate the grill bulge from the surroundings in such a way that the relatively substantial amount of microwaves which, despite the sheet, make their way into the grill bulge do not penetrate into the surrounding room. This insulation has substantially been created by the sheet being in electric contact with a metallic reflector arranged in the grill bulge, which reflector is used to reflect IR radiation from the grill elements in the oven cavity. The reflector and the sheet are electrically insulated from the walls of the oven cavity so that they form a cage, which acts as a microwave seal in relation to the surrounding room.
A special difficulty in this context are the electric connections of the grill elements, which connections function as antennae for the microwaves. The microwaves picked up by them can then escape from the grill bulge by the intermediary of those wires from the connections which lead out from the bulge. In order to prevent this, a specially configured shielding arrangement for the connections and their conductors are shown in the patent, which arrangement has the task of reflecting the microwaves back into the grill bulge.
OBJECTS OF THE INVENTION
The object of the present invention is to provide a method and a device which make the manufacture of the grill bulge and the grill elements including their connections to feeders considerably simpler and less expensive and improve the efficiency of the grill. In addition, one object of the method and the device according to the present invention is to increase the technical life of the grill elements.
SUMMARY OF THE INVENTION
The object of the invention is achieved by a microwave oven according to the independent claim 1 and a method according to the independent claim 12. Preferred embodiments of the invention are described in the dependent claims 2-11 and 13-17.
The invention is based on the insight that it is possible by means of the design of cavities to control their microwave-propagation properties in such a way that parts of them will be essentially microwave free.
According to one aspect of the present invention, a microwave oven is provided, to which is arranged a space for IR radiating means, which has a connection opening to the oven cavity, the space includi
REFERENCES:
patent: 2920174 (1960-01-01), Haagensen
patent: 3878350 (1975-04-01), Takagi
patent: 4728763 (1988-03-01), Bell et al.
patent: 4761529 (1988-08-01), Tsisios
patent: 5147993 (1992-09-01), Braun et al.
patent: 5313036 (1994-05-01), Chartrain et al.
Andersson Ann-Marie
Gunnar Nyren
Leung Philip H.
Rice Robert O.
Roth Thomas J.
Van Winkle Joel M.
Whirlpool Corporation
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