EP2187704B1 - Cooking device and method for emitting microwaves inside a cooking device - Google Patents

Description

The invention relates to a cooking appliance according to the preamble of claim 1. Furthermore, the invention relates to a method for emitting microwaves in an interior of a cooking appliance.

The US 5,237,141 discloses a high frequency heating apparatus comprising means for generating microwave energy for heating food in a chamber. The microwave generating means comprise a microwave emitter located on one of the side inner walls of the chamber without further details being described.

• eine Quelle für elektromagnetische Heizungsenergie;
• einen koaxialen Wellenleiter mit einem Innenleiter und einem Außenleiter, der von einem Eingangsende zu einem Ausgangsende in der Breite zunimmt;
• Mitteln zum Koppeln der Quelle an das Eingangsende;
• leitende Abdeckungsmittel, die lösbar am Ausgangsende befestigt sind,
• wobei der Innenleiter sich über fast die gesamte Länge des Außenleiters erstreckt, um mit dem Außenleiter zusammenzuwirken, um im Wesentlichen nur die koaxiale laufende Welle zu unterstützen, und mit den Abdeckungsmitteln zusammenzuwirken, um einen Gargutaufheizungsabteil zwischen dem Ende des Innenleiters und den Abdeckungsmitteln zu definieren.

The US 3,532,847 discloses a microwave oven for cooking and heating food in an electromagnetic radiation field, comprising:

• a source of electromagnetic heating energy;
• a coaxial waveguide having an inner conductor and an outer conductor increasing in width from an input end to an output end;
• Means for coupling the source to the input end;
• conductive cover means detachably attached to the output end,
• wherein the inner conductor extends over almost the entire length of the outer conductor to cooperate with the outer conductor to support substantially only the coaxial current wave, and to cooperate with the cover means to define a Gargutaufheizungsabteil between the end of the inner conductor and the cover means.

The US 4,866,233 discloses an apparatus for heating, in particular sterilizing, hermetically sealed packages of objects. The device is with a workspace which is limited by a metallic bottom plate and by a dome-shaped sheath part which can be placed airtight on the ground. Trained as a window radiation inlet openings are arranged in the bottom plate. Hollow waveguides of two microwave radiators are connected to these windows.

The EP 0 429 822 A1 discloses a generic cooking appliance, which has a metallic enclosure for limiting a cooking chamber and a microwave source with two magnetrons. The cooking chamber is subdivided into a further interior space by a dividing wall which extends over the entire height and a part of the width of the cooking space. The microwave heating is achieved in that symmetrically two magnetrons are arranged on the outside of the cooking chamber, wherein the magnetrons are connected to the cooking chamber by means of two identical, arranged on the side and symmetrical funnel-shaped structures, wherein the structures cover not only the respective magnetron, but In addition, fulfill the tasks to prevent leakage of radiation to the outside, to guide radiation in the direction of the cooking chamber and to record a special mode-propagating mixing device.

A disadvantage of the known cooking appliance is the fact that the funnel-shaped structures and the mode mixing device should be adapted to the respective magnetron so that no losses occur when guiding the microwaves into the cooking space. Reflections that could lead to overheating of the magnetron must also be avoided in a complex manner.

The invention is therefore based on the object to further develop the generic cooking appliance and method such that the disadvantages of the prior art are at least partially overcome. In particular, it should be possible to feed microwaves into the interior of the cooking appliance in a relatively simple manner with high efficiency.

According to the object of the cooking appliance is achieved by the characterizing part of claim 1.

Preferred cooking devices according to the invention are described in claims 2 to 10.

The object relating to the method for emitting microwaves in an interior of a cooking appliance is achieved by claim 11. A preferred method according to the invention is described in claim 12.

For the purposes of this application, direct radiation or microwaves radiated along a direct path means that microwave radiation is allowed to pass from a microwave source into the cooking chamber of a cooking appliance without reflections or even waveform changes. In this case, a gate forms the entrance to the interior having the cooking chamber and comprises at least one opening in the lining of the interior.

The invention is based on the surprising finding that in that a coupling-out element microwaves directly from a structure in the microwaves from a microwave source amplified - as by interaction between an electron beam and a microwave signal to be amplified - decoupled, so that they pass through a gate into the interior of a cooking appliance, which includes at least the cooking chamber, the usual necessary for the protection of the microwave source parts, such as waveguides and circulators , omitted. Another effect of this arrangement is that it is relatively compact.

If the coupling-out element comprises at least one antenna part projecting from the wall, the sealing towards the interior is simpler than would be the case with a waveguide. In addition, the radiation characteristic is then favorable because the microwaves are radiated in the direction of all of the inner wall adjacent inner walls or inner wall sections. When using a λ / 4 antenna as much energy is fed into the interior.

When the door comprises a hood of dielectric material separating the decoupling element from the atmosphere in the interior, it is achieved that the hood transmits the microwaves into the interior, but thermally isolates the microwave source from the interior. In particular, in cooking appliances for large kitchen use, this insulation is advantageous because in such cooking appliances a high temperature prevails. Another effect is that also an additional insulation against liquid is made. When the hood is attached to the wall, at the same time the space in which the microwave source is located, sealed against the interior of the cooking appliance. Otherwise, an additional seal would be required in the area of the microwave source, if in fact the space in which the microwave source is located should be sealed off from the interior. A flange connection makes it possible to make the inner wall of a metallic material. A flange connection also compensates for the effects of different thermal expansion coefficients of the hood and the wall. If the attachment to the wall at least one sealing element, gases can not easily escape from the oven.

If the hood is made of glass, in particular tempered borosilicate or quartz glass, it has a low dielectric constant and a relatively high thermal resistance. Alternatively, the hood can also be made of high-purity oxides such as Al ₂ O ₃ and ZrO ₂ .

In the case in which the interior is at least partially divided into the cooking chamber and a pressure chamber via at least one flow guide, a fan wheel and the Auskoppelement are arranged in the pressure chamber, the Strömungsleitglied with at least one, in particular central, opening for sucking atmosphere from the cooking chamber is provided in the pressure chamber and the flow guide between the pressure chamber and the cooking chamber, in particular at its edge region, at least one, in particular slit-shaped, air-permeable compound leaves free, form the pressure chamber and the cooking chamber two coupled resonators for the microwaves. It is therefore irrelevant in which of the two rooms the microwaves are first radiated. In addition, the circulation of the atmosphere in the interior via the fan wheel ensures a mixture of modes and equalization of the microwave energy. For example, to further influence the cooking chamber climate, a steam injection device may be provided which injects steam into the flow, or an electric heater or gas-powered heater may be provided for heating the pumped medium. Especially in cooking appliances for the commercial kitchen use, the homogenization of the cooking chamber climate, which comes about by the circulation of the cooking chamber, is advantageous.

If each milk microwave source is provided on an outer side of the interior, in particular on the outer side of a side wall of a pressure chamber arranged next to the cooking chamber, the fan wheel will usually reflect microwaves, so that a better mixture of modes is achieved without additional measures. Thus, an additional function is provided in an efficient manner, since the fan wheel already exists in combination cooking appliances anyway. The arrangement of the microwave source on an outside of a side wall of the interior is advantageous because the fact that no microwave source is present on the ceiling of the interior, the size is minimized. This in turn is desirable so that two cooking devices can be stacked without affecting operability. Compared to an arrangement of the microwave sources in the bottom region of the cooking chamber, an arrangement on a side wall has the advantage that the requirements in terms of the seal is not that high. In particular, in cooking appliances for large kitchen use is namely in the bottom area pretty much liquid or even a drain device. An arrangement on a side wall of an arranged next to the cooking chamber pressure chamber has the advantage that here, too, the requirements for the seal are not so high, because a certain separation from the oven already exists. Because the pressure chamber and the cooking chamber form coupled resonator chambers, an arrangement on a side wall of the pressure chamber is not detrimental to the uniformity of the microwave distribution in the cooking chamber. In an arrangement in a common installation space electrical connections can be shared. In addition, there is only one room in this case, which is to be separated in a gas-tight manner and, if necessary, made accessible for repair and maintenance. The arrangement on a wall portion, which is at an angle to a projected by a drive shaft of the fan side wall, has the effect that the microwaves are radiated adjacent to the fan. So you are not shielded by the fan. However, it is still a radiation in the direction of the fan present, which is for the turbulence, so the homogenization of the microwave distribution, an advantage.

If a plurality of microwave sources are arranged at different heights in the cooking appliance and have a respective rated power of 2000 watts HF or less, the power required in consideration of the cooking chamber size can be achieved via commercially available microwave sources.

If the cooking appliance comprises a further device for the treatment (treatment device) of food in the cooking chamber, the food can be treated in the same cooking appliance in several ways. This increases the efficiency because the food does not have to be constantly removed from the cooking appliance. It also increases the quality, as a precise cooking is possible.

One effect of a sensing device that is operatively associated with each microwave source, the further treatment device, the display device, the operating device and / or the control or regulating device is that food can be subjected to a complex combination treatment without intervention by a user.

If a plurality of treatment levels in the cooking space is determined via a food support device and a number of microwave sources is provided according to the dimensioning of the cooking space and / or the number of treatment levels, commercially available microwave sources, for example magnetrons, can be used. The required overall performance is achieved by providing a sufficient number of microwave sources.

Figur 1

eine Längsschnittansicht eines erfindungsgemäßen Gargeräts;

Figur 2

einen Querschnitt in Draufsicht des Gargeräts;

Figur 3

eine schematische Querschnittansicht eines handelsüblichen Magnetrons; und

Figur 4

eine Detailansicht der Anordnung einer Mikrowellenquelle an der Wand des Gargeräts der Figuren 1 und 2.

Further features and advantages of the invention will become apparent from the following description in which embodiments thereof are explained with reference to schematic drawings. Showing:

FIG. 1

a longitudinal sectional view of a cooking appliance according to the invention;

FIG. 2

a cross section in plan view of the cooking appliance;

FIG. 3

a schematic cross-sectional view of a commercially available magnetron; and

FIG. 4

a detailed view of the arrangement of a microwave source on the wall of the cooking appliance of Figures 1 and 2 ,

An example in the Figures 1 and 2 illustrated cooking appliance 1 comprises an interior defined by a rear wall 2, a ceiling 3, a bottom surface 4, a first side wall 5, a front wall 6, a second side wall 7 and a side wall portion 8, the rear wall 2 and the front wall 6 also referred to as side walls can be. The interior is at least partially divided by a flow baffle 9 in a cooking chamber 10 and a pressure chamber 11. In the front wall 6 is a door not shown for loading the cooking chamber 10 with food (not shown) and for removing the same.

In the cooking chamber 10 is a frame 12 with a plurality of rails 13a-f for insertion of food supports (not shown), on which the food is placed, provided.

In the pressure chamber 11 is a radial fan 14, which is driven by a motor 16 via a shaft 15. The radial fan 14 sucks atmosphere (steam, vapor, air etc.) from the cooking chamber 10 through an opening located in the center of the Strömungsleitblechs 9 17 and blows it off radially. Thus, there is a pressure difference between the pressure chamber 11 and the cooking chamber 10. The atmosphere is due to this pressure difference through slots 18 between the edge of Strömungsleitblechs 9 and at least one of the rear wall 2, front wall 6, ceiling 3 and bottom surface 4 again led into the cooking chamber 10 , In addition or as an alternative to the slots 18, it is also possible to provide openings in the flow guide plate 9 in the edge area of the flow guide plate 9.

The illustrated cooking appliance 1 comprises a microwave heating and another, not shown, means for the treatment of food in the cooking chamber 10, such as a ventilation device, an electric heater, a gas-powered heater, a heat exchange device, a cooling device, a moisture supply device and / or a Feuchtigkeitsabführeinrichtung.

A moisture removal device is preferably located in a bottom region 19. An electric or gas-operated heater or a heat exchange device, the fan 14 for heating the funded flow medium so the atmosphere completely or partially surround. For example, a moisture supply device may include a steam injector that injects steam into the flow.

At least the regulation or control and the electrical connections of each treatment device are located, as well as the motor 16, in an installation space 20 adjacent to the pressure space 11. In the illustrated example, the installation space 20 is directly via a door (not shown) in an outer side wall 21 accessible from outside the cooking appliance 1 to facilitate maintenance and installation.

Microwaves are generated in magnetrons 22, 23 of the microwave heating. The microwaves generated in the magnetrons 22, 23 are guided to a respective gate 24, 25 in order to be radiated on a direct path into the pressure chamber 11. The pressure chamber 11 and the cooking chamber 10 form coupled, substantially cuboid resonators for the radiated microwaves. For this reason, finds a uniform microwave energy distribution in the cooking chamber 10 instead. The coupling takes place essentially via the slots 18, which are also provided for circulating the cooking chamber atmosphere. In addition, openings (not shown) for microwave-permeable openings may be provided in the flow guide plate 9. In order to maintain the pressure difference between the pressure chamber 11 and the cooking chamber 10, these openings are not permeable to air, but filled with dielectric material, for example, quartz glass, borosilicate glass or ceramic.

The radial fan 14 is at least partially made of a material that reflects microwaves. The gates 24,25 are located in the side wall portion 8, which adjacent to the second side wall 7 through which the drive shaft 15 of the radial fan 14 projects, is arranged. The radial fan 14 extends in the radial direction at most to the transition from the side wall 7 to the side wall portion 8, so that the gates 24,25 are not shielded by the fan 14. For the radiation in the pressure chamber 11 rod or slot antennas are provided. The radiation characteristic is such that at least one emission takes place parallel to the side wall part 8. The microwaves thus radiated therefore also reach the radial fan 14 and are swirled by it. To even out the microwave energy and transfer of the microwave energy into the cooking chamber 10 also contributes that the side wall portion 8 is at an angle to the side wall 7. Due to this arrangement, the microwaves are already partly reflected into the cooking chamber 10 via the rear wall 2.

A further homogenization of the microwave energy distribution is achieved in that the gates 24,25 are provided at different heights in the interior of the cooking appliance 1. Although the cooking appliance 1 is designed for large kitchen use, commercially available magnetrons 22, 23, which are designed for use in household microwave appliances, are used for cost reasons. These usually have a nominal power of about 2000 watts of HF. In order nevertheless to achieve sufficient heating, the number of magnetrons 22,23 depends on the number of rails 13a-f in the frame 12, that is on the number and dimensions of the accommodatable food supports.

To clarify some terms used here is in the FIG. 3 a known per se embodiment of the first magnetron 22 is shown. The first magnetron 22 includes a housing 26 from which an antenna stub 27 protrudes. The antenna stub 27 also includes a protective cap 28. The magnetron 22 includes a cathode 29 which is heated during operation. The cathode 29 is surrounded by an anode 30 with projecting, circumferentially arranged wings 31. The magnetron also contains a magnet stack 32. During operation, the electrons emitted by the cathode 29 are guided around the cathode 29 under the influence of the electric and magnetic fields. The reaction of the fields on the incident on the anode 30 electrons creates an oscillation. An inner conductor 33 of the antenna couples the generated microwaves out of the oscillator device and radiates them into the pressure chamber 11. The microwaves generated in the magnetron 22 are thus emitted directly into the pressure chamber 11 without the interposition of a waveguide. It should be noted that some magnetrons instead of the inner conductor 33 may comprise a waveguide for coupling out the microwaves.

In the cooking chamber 10 of the cooking device 1 prevail at times extreme conditions. In this regard, a cooking appliance 1 for the commercial kitchen use differs from a household microwave. In particular, the moisture in the cooking chamber 10 and in the pressure chamber 11 can be high and the temperature there can reach values of approximately 400 ° C. The magnetrons 22,23 should be protected from this atmosphere.

Like from the FIG. 4 can be seen, a cover in the form of a hood 34 is used for such a protection. The hood 34 is made of a dielectric material which is permeable to microwaves. The material also has a low thermal conductivity. A hood 34 made of ceramic can be used. Due to the low dielectric constant, glass, for example quartz or borosilicate glass (Pyrex), is also suitable as a manufacturing material. The hood 34 surrounds the protruding through the side wall portion 8 antenna stub 27 of the magnetron. To increase the thermal insulation is a gap 35 between the inside of the hood 34 and the antenna strut 37. The gap 35 is in particular filled with air.

In order to take account of the different coefficients of thermal expansion of the hood 34 and the side wall part 8, the hood 34 is fastened in the illustrated embodiment via a flange 36 to the side wall part 8. Thus, the hood 34 fulfills the dual function of the gas-tight sealing of the installation space 20 with respect to the interior atmosphere as well as the thermal insulation of the magnetron antenna stub 27. The flange also comprises two flat gaskets 37,38, a stainless steel rotary member 39 and screws 40,41 for fixing the stainless steel rotary member 39 at the cooking chamber side of the side wall part. 8

The direct magnetron coupling, as shown above, has the advantage that the usual in professional Mikrowellengargeräten fashion mixer boxes and paddle wheels outside the cooking appliance interior omitted. This also applies to the necessary for the protection of the magnetron from mismatch waveguides, circulators and directional couplers, which are commonly used. Thus, both costs and space in the installation space 20 are saved.

LIST OF REFERENCE NUMBERS

1

Cooking appliance

2

rear wall

3

blanket

4

floor area

5

first sidewall

6

front wall

7

second side wall

8th

Sidewall portion

9

flow baffle

10

oven

11

pressure chamber

12

frame

13a-f

rails

14

radial fan

15

wave

16

engine

17

opening

18

slot

19

floor area

20

installation Raumn

21

outer sidewall

22

magnetron

23

magnetron

24

gate

25

gate

26

casing

27

antenna stub

28

protective cap

29

cathode

30

anode

31

wing

32

magnetic stack

33

inner conductor

34

Hood

35

gap

36

flange

37

first flat gasket

38

second flat gasket

39

Stainless steel swivel

40

screw

41

screw

Claims (12)

1. A cooking device (1), comprising
   an interior space (10, 11) that has at least one cooking chamber (10), wherein a carrier device for food to be cooked (12, 13a-13f) is provided that specifies a plurality of treatment levels in the cooking chamber (10), and
   at least one microwave source (22, 23) that comprises an oscillator device for generating microwaves and at least one output coupler element (27, 33) for coupling out the microwaves generated in the oscillator device directly from a structure of the microwave source for the purpose of amplifying microwaves, characterized in that the number of microwave sources (22, 23) depends on the dimensioning of the cooking chamber (10) and the number of treatment levels, and
   each output coupler element (27, 33) guides the microwaves to be coupled out to a port (24, 25) in a wall or a wall section (8) of the interior space (10, 11) and emits the microwaves from the port (24, 25) directly into the interior space (10, 11).
2. A cooking device according to claim 1, characterized in that the output coupler element (27, 33) comprises at least one antenna part (27) that protrudes from the wall or the wall section (8).
3. A cooking device according to claim 1 or 2, characterized in that the port (24, 25) comprises a cap (34) that is made of dielectric material and that separates the output coupler element (27, 33) from the atmosphere of the interior space (10, 11), wherein in particular the cap (34) is attached to the wall or the wall section (8) by means of at least one flange connection and/or using at least one sealing element (37, 38).
4. A cooking device according to claim 3, characterized in that the cap (34) is manufactured from glass, in particular tempered borosilicate or quartz glass, and/or comprises ceramic, in particular Al₂O₃ or ZrO₂.
5. A cooking device according to any one of the preceding claims, characterized in that
   the interior space (10, 11) is divided at least partially into the cooking chamber (10) and a pressure chamber (11) by means of at least one flow directing element,
   a fan wheel (14) and the output coupler element (27, 33) are disposed in the pressure chamber (11),
   wherein the output coupler element (27, 33) guides the microwaves to be coupled out to the port (24, 25) in that wall section (8) that in particular has an inclination relative to the walls (7) that are adjacent to said wall section, in particular the side walls (2, 7) of the interior space (10, 11), is movable and/or aimed at a point of the interior space (10, 11), in particular the center of the cooking chamber (10),
   the flow directing element (9) is provided with at least one, in particular a centered, opening (17) for drawing in air from the cooking chamber (10) into the pressure chamber (11), and
   the flow directing element (9) leaves open at least one air-permeable connection (18) between the pressure chamber (11) and the cooking chamber (10), in particular in the area of its edge as well as in its center.
6. A cooking device according to any one of the preceding claims, characterized in that
   each microwave source (22, 23) is provided on an outer side of the interior space (10, 11), in particular on the outer side of a side wall (7, 8) of a pressure chamber (11) that is disposed next to the cooking chamber and/or in an installation chamber (20) that additionally contains drive means (16) for a fan wheel (14) that is located in the pressure chamber (11), wherein in particular at least one of the ports (24, 25) is provided in a wall section (8) that is positioned at an angle to a side wall (7) through which a drive shaft (15) of the fan wheel (14) projects, wherein preferably a first port (24) is disposed above the fan wheel (14) and a second port (25) is disposed below the fan wheel (14).
7. A cooking device according to any one of the preceding claims, characterized by a plurality of microwave sources (22, 23) that are arranged at different heights in the cooking device (1) and/or respectively have a nominal power of 2000 watts HF or less.
8. A cooking device according to any one of the preceding claims, characterized by at least one additional device for the treatment of food to be cooked in the cooking chamber (10), in particular at least one device from the group comprising:

   an electric heating device,

   a gas-operated heating device,

   a heat exchanger,

   a refrigeration device,

   a humidifying device,

   a dehumidifying device,

   an aeration device and

   a deaeration device.
9. A cooking device according to any one of the preceding claims, characterized in that
   the walls (2, 3, 4, 5, 6, 7, 8) of the interior space (10, 11), a flow directing element (9) that divides the interior space at least partially into the cooking chamber (10) and a pressure chamber (11), and/or a carrier device for food to be cooked (12, 13a-13f) that is provided in the cooking chamber (10) reflects or reflect microwaves at least partially.
10. A cooking device according to any one of the preceding claims, characterized by at least one sensor device, a display device, an operating device and a control or regulation device, wherein the sensor device is operatively connected in particular with each microwave source (22, 23), an additional treatment device, the display device, the operating device and/or the control or regulation device.
11. A method for emitting microwaves into an interior space of a cooking device according to any one of the preceding claims, comprising the provision of at least one microwave source that comprises an oscillator device for generating microwaves and at least one output coupler element for coupling out the microwaves generated in the oscillator device directly from a structure of the microwave source in which microwaves are amplified,
    characterized by
    the emission of the microwaves into the interior space along a direct path by means of the output coupler element.
12. A method according to claim 11, characterized in that
    a carrier device for food to be cooked specifies a plurality of treatment levels in the cooking chamber, and
    a number of microwave sources is provided that depends on the dimensioning of the cooking chamber and/or the number of treatment levels.

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