[0001] The present invention relates to a microwave oven with a feed box system according
to claim 1.
[0002] 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.
[0003] 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.
[0004] 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.
[0005] 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.
[0006] The
US 5,825,000 describes a microwave oven with a feed box fixed directly at the oven cavity. The
feed box comprises a wider portion and a smaller portion. A magnetron is fixed at
the wider portion.
[0007] In the
DE 31 47 044 C2 a microwave oven with a feed box under the bottom wall of the oven cavity is disclosed.
The feed box extends substantially under the whole bottom wall. Under the feed box
a magnetron is arranged. Within said feed box there are a stirrer and an antenna of
said magnetron.
[0008] The
US 3,939,320 discloses a microwave oven with a feed box above the oven cavity. A magnetron is
arranged in the outer portion of the microwave oven. Between the feed box and the
magnetron is a microwave channel.
[0009] 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.
[0010] 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.
[0011] According to the present invention the microwave oven comprises a feed box system,
wherein:
- the feed box system includes a primary feed box and a secondary feed box,
- the primary feed box and the secondary feed box are arranged one upon the other at
a cavity wall of an oven cavity,
- the circumference of the primary feed box is smaller than the circumference of the
secondary feed box,
- the secondary feed box and at least that cavity wall, at which the feed box system
is arranged, form a single-piece part,
- the primary feed box is fixed to the secondary feed box and covers a recess of said
secondary feed box,
- a microwave source is arranged at the primary feed box;
- an antenna of the microwave source extends into the interior of the primary feed box,
and
- the axis of the antenna extends along another direction as a normal vector of the
cavity wall, at which the feed box system is arranged.
[0012] 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. 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.
[0013] 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.
[0014] Preferably, 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 wave labyrinth contributes to the closeness of the oven cavity.
[0015] 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.
[0016] 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.
[0017] 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.
[0018] 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.
[0019] Additionally, the secondary feed box and the oven cavity may be enamelled.
[0020] For example, the primary feed box is welded, screwed, clinched and/or riveted to
the secondary feed box.
[0021] 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.
[0022] 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.
[0023] According to the preferred embodiment of the present invention the microwave source
is a magnetron.
[0024] The invention will be explained in more detail below by means of an exemplary embodiment.
Reference is thereby made to the drawing, wherein
- FIG 1
- shows a schematic sectional view of a feed box system within a microwave oven according
to a preferred embodiment of the present invention.
[0025] FIG 1 shows a schematic sectional view of a feed box system according to a preferred
embodiment of the present invention. The feed box system is arranged within a microwave
oven. The feed box system includes a primary feed box 10 and a secondary feed box
12. The primary feed box 10 and the secondary feed box 12 are arranged one upon the
other at a top wall 14 of an oven cavity 16.
[0026] 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.
[0027] 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.
[0028] 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.
[0029] 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.
[0030] 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.
[0031] 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.
[0032] 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.
[0033] 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.
[0034] 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.
List of Reference Numerals
[0035]
10 |
primary feed box |
12 |
secondary feed box |
14 |
top wall, cavity wall |
16 |
oven cavity |
18 |
magnetron |
20 |
antenna |
22 |
overlapping portions, wave labyrinth |
24 |
stirrer |
26 |
direction of the antenna |
28 |
normal vector of the wall |
30 |
vertical rotation axis |
1. A microwave oven with a feed box system, wherein:
- the feed box system includes a primary feed box (10) and a secondary feed box (12),
- the primary feed box (10) and the secondary feed box (12) are arranged one upon
the other at a cavity wall (14) of an oven cavity (16),
- the circumference of the primary feed box (10) is smaller than the circumference
of the secondary feed box (12),
- the secondary feed box (12) and at least that cavity wall (14), at which the feed
box system is arranged, form a single-piece part,
- the primary feed box (10) is fixed to the secondary feed box (12) and covers a recess
of said secondary feed box (12),
- a microwave source (18) is arranged at the primary feed box (10) ;
- an antenna (20) of the microwave source (18) extends into the interior of the primary
feed box (10), and
- the axis of the antenna (20) extends along another direction as a normal vector
of the cavity wall (14), at which the feed box system is arranged.
2. The microwave oven according to claim 1,
characterized in that
the axis of the antenna (20) extends orthogonal to the normal vector of the cavity
wall (14), at which the feed box system is arranged.
3. The microwave oven according to claim 1 or 2,
characterized in that
overlapping portions (22) of the primary feed box (10) and the secondary feed box
(12) are formed complementary to each other, so that the overlapping portions (22)
form a wave labyrinth.
4. The microwave oven according to any one of the preceding claims,
characterized in that
the overlapping portions (22) of the primary feed box (10) and/or of the secondary
feed box (12) have an S-shaped or meander-shaped cross-section.
5. The microwave oven according to any one of the preceding claims,
characterized in that
the secondary feed box (12) is formed out of that cavity wall (14), at which the feed
box system is arranged, by embossing and/or deep-drawing.
6. The microwave oven according to any one of the claims 1 to 4,
characterized in that
the secondary feed box (12) is formed out of the oven cavity (16) by embossing and/or
deep-drawing.
7. The microwave oven according to any one of the preceding claims,
characterized in that
the secondary feed box (12) and at least that cavity wall (14), at which the feed
box system is arranged, are enamelled.
8. The microwave oven according to any one of the preceding claims,
characterized in that
the secondary feed box (12) and the oven cavity (16) are enamelled.
9. The microwave oven according to any one of the preceding claims,
characterized in that
the primary feed box (10) is welded, screwed, clinched and/or riveted to the secondary
feed box (12).
10. The microwave oven according to any one of the preceding claims,
characterized in that
the primary feed box (10) covers a recess of the secondary feed box (12).
11. The microwave oven according to claim 10 as far as referred back to claim 3,
characterized in that
the wave labyrinth (22) encloses the recess completely or at least partially.
12. The microwave oven according to any one of the preceding claims,
characterized in that
the microwave oven comprises at least one stirrer (24) arranged at least partially
within the secondary feed box (12).
13. The microwave oven according to claim 12,
characterized in that
the stirrer (24) extends partially into the oven cavity (16).
14. The microwave oven according to any one of the preceding claims,
characterized in that
the microwave source is a magnetron (18).