The present invention relates to a microwave oven with a feed box system according to the preamble of claim 1.
Microwave ovens are efficient cooking devices for heating food and beverages. However, the strong electromagnetic fields used for the microwave heating are a potential threat to the health of the operator. A special attention has to be paid in order to minimize any leakage of such electromagnetic waves.
One of the critical parts within the microwave ovens is the connection between the wave source and the oven cavity. Very high power densities of the electromagnetic field occur in this area. Thus, a wave-tight system for the connection between the wave source and the oven cavity is required. For example, a magnetron can be used as the wave source.
In known microwave ovens the connection between the magnetron and the oven cavity comprises three functional units. The first functional unit is a feed box acting as a wave channel between the magnetron and the oven cavity. The second functional unit is an interface portion for tightly mounting the magnetron to the feed box. The third functional unit is the fixation of the feed box to the oven cavity.
The connection of the magnetron to the feed box is unproblematic with respect to microwave leakage. Also the setup of the feed box causes no difficulties related to microwave leakage. The critical point is the fixation of the feed box onto the oven cavity, since the connection between two separate components may create gaps through which microwaves can emanate into the surrounding area. For example, said gaps are caused by mechanical tolerances or by a limited planarity.
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In the above microwave ovens there are a lot of potential gaps between the feed box and the oven cavity or between the fed box and the microwave channel, respectively, so that microwave energy can emanate through those gaps.
It is the object of the present invention to provide a microwave oven with an improved closeness between the wave source and the oven cavity.
This object is achieved by the microwave oven according to claim 1.
According to the present invention the secondary feed box and at least that cavity wall, at which the feed box system is arranged, form a single-piece part, and overlapping portions of the primary feed box and the secondary feed box are formed complementary to each other, so that the overlapping portions form a wave labyrinth.
The core of the present invention is the feed box system with two separate feed boxes, wherein one feed box forms a single-piece part with the cavity wall, on the one hand and the direction of the antenna with respect to the normal vector of the cavity wall on the other hand, wherein the overlapping portions of the primary feed box and the secondary feed box are formed complementary to each other, so that the overlapping portions form a wave labyrinth. The number of potential gaps is reduced. The secondary feed box and the cavity wall form a single-piece part, so that there cannot be any potential gap between them. The primary feed box cover the recess of the secondary feed box, so that the probability of potential gaps between the primary and secondary feed box is reduced. The direction of the antenna impacts the streamlines of the electric and magnetic fields of the microwave with respect to the cavity wall.
According to the preferred embodiment of the present invention the axis of the antenna extends orthogonal to the normal vector of that cavity wall, at which the feed box system is arranged. This constellation of the antenna restricts the directions of the streamlines of the electric and magnetic fields and supports the closeness of the oven cavity.
Since the overlapping portions of the primary feed box and the secondary feed box are formed complementary to each other, so that the overlapping portions form a wave labyrinth, said wave labyrinth contributes to the closeness of the oven cavity.
For example, the overlapping portions of the primary feed box and/or of the secondary feed box have an S-shaped or meander-shaped cross-section.
According to the preferred embodiment of the present invention the secondary feed box is formed out of that cavity wall, at which the feed box system is arranged, by embossing and/or deep-drawing. The embossing and/or deep-drawing allow an efficient production of the microwave oven with the feed box system.
Additionally, the secondary feed box may be formed out of the oven cavity by embossing and/or deep-drawing. This is an efficient method for the production of the oven cavity with the secondary feed box.
Further, the secondary feed box and at least that cavity wall, at which the feed box system is arranged, may be enamelled. Since the primary feed box is fixed afterwards, the primary feed box remains un-enamelled. This allows a very good electrical contact between the wave source and the primary feed box.
Additionally, the secondary feed box and the oven cavity may be enamelled.
For example, the primary feed box is welded, screwed, clinched and/or riveted to the secondary feed box.
According to the preferred embodiment of the present invention the primary feed box covers a recess of the secondary feed box. Thereby, the wave labyrinth may enclose the recess completely or at least partially.
For example, the microwave oven may comprise at least one stirrer arranged at least partially within the secondary feed box. However, the stirrer may extend partially into the oven cavity.
According to the preferred embodiment of the present invention the microwave source is a magnetron.
The invention will be explained in more detail below by means of an exemplary embodiment. Reference is thereby made to the drawing, wherein
In this embodiment the primary feed box 10 and the secondary feed box 12 are substantially formed as cuboids. The secondary feed box 12 is arranged directly above an oven cavity 16. The base area of the secondary feed box 12 may be rectangular, circular or square. The primary feed box 10 is arranged directly above the secondary feed box 12. The width of the primary feed box 10 is smaller than the width of the secondary feed box 12. Also the circumference of the primary feed box 10 is smaller than the circumference of the secondary feed box 12.
In this example the feed box system is arranged on a top wall 14 of the oven cavity 16. Alternatively, the feed box system may be arranged at a side wall of the oven cavity 16. The secondary feed box 12 and the top wall 14 or side wall of the oven cavity 16, respectively, form a single-piece part. For example, the secondary feed box 12 is formed out of the top wall 14 or side wall of the oven cavity 16, respectively, by an embossing or by a deep-drawing.
The primary feed box 10 is fixed to the secondary feed box 12 and covers a recess of said secondary feed box 12. For example, the primary feed box 10 is welded, screwed, clinched or riveted to the secondary feed box 12. The overlapping portions 22 of the primary feed box 10 and the secondary feed box 12 comprise multiple grooves extending along the circumference of the recess in the secondary feed box 12. Thus, the overlapping portions 22 of the primary feed box 10 and of the secondary feed box 12 have an S-shaped or meander-shaped cross-section.
Further, the overlapping portions 22 of the primary feed box 10 and of the secondary feed box 12 are complementary to each other, so that said overlapping portions form a wave labyrinth 22. Said wave labyrinth 22 encloses the common portion of the primary feed box 10 and the secondary feed box 12 completely or at least partially.
By an enamel process the top wall 14 of the oven cavity 14 as well as the secondary feed box 12 is coated. The primary feed box 10 is fixed to the secondary feed box 12 after the enamel process. Thus, the primary feed box 10 is not coated by the enamel process. Additionally, further walls of the oven cavity 16 may be enamelled. For example, each wall of the oven cavity 14 and the secondary feed box 12 may be coated by the enamel process.
A magnetron 18 is attached at the outer side of the primary feed box 10. An antenna 20 of the magnetron 18 extends into the interior of the primary feed box 10. In this example, the direction 26 of the antenna 20 extends orthogonal to a normal vector 28 of the top wall 14 of the oven cavity 16. In general, the direction 26 of the antenna 20 of the inventive feed box system extends along another axis as the normal vector 28 of the cavity wall 14, at which said feed box system is arranged.
Within the secondary feed box 12 a stirrer 24 is arranged. The stirrer 24 is rotatable around a vertical rotation axis 30. An axle 32 of the stirrer 24 penetrates a top wall of the secondary feed box 12. In this example, the stirrer 24 is arranged within the secondary feed box 12. Alternatively, the stirrer 24 can extend at least partially into the interior of the oven cavity 16.
The microwave oven with the feed box system according to the present invention requires less material as in the prior art due to the embossing or deep-drawing the secondary feed box 12 out of the oven cavity 16. A wave-tight connection between the primary feed box 10 and the secondary feed box 12 can be easily realized. The connection between the primary feed box 10 and the secondary feed box 12 needs only a few screws or bolts. Thus, the present invention allows a low cost production of the microwave oven with the feed box system.
The connection between the primary feed box 10 and the secondary feed box 12 allows a good electrical contact between the wave source and the feed box system. The embossing and/or deep-drawing of the secondary feed box 12 out of the oven cavity 16 allow an increased stiffness of the oven cavity 16.
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