EP2187699B1 - Cooking apparatus and method to provide microwaves inside the cavity of said cooking apparatus - Google Patents

Description

The invention relates to a cooking appliance comprising an interior space (10, 11) comprising at least one cooking space (10) and at least one microwave conducting structure (24, 25; 28; 48; 73; 88) for guiding microwaves from at least one microwave source (10). 22, 23) to at least an opening in a wall or a wall part (8; 78; 93) of the inner space (10, 11), the microwave conducting structure (24, 25; 28; 48; 73; 88) having an outer electrically conductive one and fixed walls (31, 32, 34, 39; 51, 52, 54; 76; 77; 91; 92, 99) and at least one element (47; 70; 84; 97) for radiating the microwaves into the interior space (10 , 11). Furthermore, the invention relates to a method for feeding microwaves into an interior of a cooking appliance.

The US 2004/0188429 A1 describes a microwave cooking system with a microwave generator and a microwave line. The microwave line comprises a microwave waveguide coupled to the microwave generator in the form of a waveguide which is connected at one end to a coaxial cable. The coaxial cable splits into two coaxial feed cables, one of which leads microwaves to a microwave oven. Coaxial cables can transmit only low microwave power.

The WO 00/09952 A1 describes a Mikrowellengargerät having a housing and a cooking zone in the housing, where the cooking takes place. An infrared grill is provided in the Garzone. Between the infrared grill and the housing, a reflector is positioned. The microwave cooker further comprises means for generating microwaves and feeding means for controllably guiding microwaves into the cooking zone via a space between the reflector and the housing. The supply means communicates with this space via an opening in the housing. It comprises a first part which extends horizontally and a second part which extends vertically. The microwave cooker further includes a mode mixer positioned in the feed means. It includes a shaft that extends through the first part. The shaft carries four blades located in the second part of the feeder. The second part of the feeding means has sloping sides. Thus, the circumference of the second part increases from the first part towards the opening. The second part is larger than the first part and quadrangular. The first part has a rectangular cross-section.

The US 4,940,869 describes a generic cooking appliance with both a conventional hot air heating and a microwave heating. The unit comprises a room with a front door, side walls, a floor space, a ceiling and a rear wall. In addition to the rear wall is a metal distribution plate, which defines with the rear wall a cavity in which a blower is mounted. The device comprises at least one microwave source, which is located outside the room, with a waveguide outlet, which opens into the room via at least one outlet opening. The exit port is located in the rear wall, opposite the distribution plate, and is terminated by a plate of a material that is permeable to microwaves. A disadvantage of the known device is that the waveguide has a fairly large contact surface with the rear wall, via which heat can be conducted to the microwave source.

The invention is therefore based on the object to develop the generic cooking appliance and the generic method such that the disadvantages of the prior art are at least partially overcome. In particular, a cooking appliance and a method are to be provided, which make it relatively easy to construct the supply of microwaves to an interior of a cooking appliance structurally and to isolate a microwave generator relatively well from the indoor climate to avoid damage and / or malfunction of the microwave generator.

This object is achieved in that the second cross-sectional shape is substantially round, in particular circular and differs from the first cross-sectional shape, and the element is arranged at one end of the second portion.

In one embodiment, the first section has a rectangular cross-sectional shape and / or comprises at least part of its length a waveguide.

It can be provided according to the invention, located at the end of the second section slot antenna.

In one embodiment, the second section comprises over at least part of its length an inner conductor which forms a coaxial conductor with the outer walling.

In a variant of this embodiment, the inner conductor extends into the first section, wherein an end of the inner conductor located in the first section is preferably fastened to a wall of the first section.

In this case, the inner conductor can be bent within the first section, in particular over an angle of approximately 90 ° or more.

In a further development variant, the element for emitting the microwaves into the interior space comprises at least one antenna, wherein optionally the inner conductor merges at its end into the antenna.

This variant can be characterized in that the end of the inner conductor is provided with mechanical fastening means, in particular a thread, for detachably connecting the antenna to the end of the inner conductor, or the end of the inner conductor forms a rod antenna projecting through an opening in the wall of the inner space , or the end of the inner conductor, in particular in the region of the opening in the wall of the interior, directly emits microwaves.

In one embodiment of the cooking appliance according to the invention, the second section is at least one part adjacent to the microwave radiation area and / or at the end of the second section, in particular over only part of its length, with a, in particular dielectric, material having a permittivity that is of the permittivity differs from air, filled, optionally in the form of a disk or a substrate and / or to adapt the impedances of the two sections.

It is proposed that the disc extends to at least the outer electrically conductive Bewandung the second portion, wherein in particular between the disc and the outer electrically conductive walling is at least one elastic sealing element.

The cooking appliance according to the invention may additionally comprise a cover which protects the element towards the interior, in particular in the form of a hood or disk, from a preferably permeable to microwaves, preferably dielectric material.

In this case, a support may be provided in or through the hood for guiding the element.

In a preferred embodiment of the cooking appliance, a flow-guiding element is arranged in the interior, which at least partially divides the interior into the cooking space and a pressure space, a fan wheel being arranged in the pressure space, the flow-guiding element having at least one, in particular centrally arranged, opening for drawing in atmosphere is provided from the cooking chamber into the pressure chamber and between the pressure chamber and the cooking chamber, in particular at the edge region of the Strömungsleitglieds, at least one, in particular slot-shaped connection for blowing out of atmosphere from the pressure chamber into the cooking chamber leaves.

In this case, the Mikrowellenleitstruktur microwaves to at least an opening in a wall or a side wall part, the or at a, in particular blunt, angle to a projected by a drive shaft of the fan wall or side wall, lead, wherein the wall or the side wall portion preferably is directed or directable with the opening on the opening arranged in the flow guide or an air-permeable compound.

It can further be provided that the at least one waveguide structure is attached to an outside of a side wall or a side wall part of the interior, in particular via a flange, and / or on a side wall or a side wall part of a pressure chamber arranged next to the cooking space, in particular in an installation space, which additionally contains drive means for a fan wheel located in the pressure chamber.

In one embodiment, the cooking device according to the invention also comprises a plurality of microwave waveguides, which are preferably arranged at different heights in the cooking appliance and / or in each case with at least one of a plurality of magnetrons, preferably with a nominal power of up to 2000 W HF in combination stand.

At least one further device for the treatment of food to be cooked in the cooking chamber, in particular at least one device from the group comprising: an electric heater, a gas-powered heater, a heat exchange device, a cooling device, a moisture supply device, a Feuchtigkeitsabrühreinrichtung, a ventilation device and a venting device may be provided.

In a further embodiment, the cooking device according to the invention further comprises at least one sensing device, a display device, an operating device and a control or regulating device, which is in particular in operative connection with a microwave source, the further treatment device, the display device and / or the operating device.

The object relating to the method for feeding microwaves into an interior of a cooking appliance is achieved in that the microwaves have a second section adjacent to the end with a round cross-sectional shape and a first section previously arranged in the propagation direction of the microwaves and having a different cross-sectional shape in the microwave structure be led to the interior.

It can be provided that a plurality of treatment levels in the cooking chamber is determined via a food support device, and a number of microwave sources which are directed according to the dimensioning of the cooking chamber and / or the number of treatment levels is provided.

The invention is based on the surprising finding that by using a microwave guide structure having two different sections in a cooking appliance, a second section of the microwave guide structure has a wall or wall section in the region of an opening or a passage in the opening to the wall or wall section only over a round section Circumference touched. The length of the contact circumference is then small compared to a polygonal cross-sectional shape, which keeps the heat transfer via the usually metallic outer wall of the waveguide structure relatively low. A gas-tight seal against the interior is also easier to implement due to the round geometry. Characterized in that at the end of the second portion and thus in the region of the opening is an element for coupling out microwaves from the Mikrowellenleitstruktur and for emitting the coupled-microwaves in the interior, the construction is relatively simple compared to, for example, rotating devices. More specifically, the seal of the waveguide structure is easier to realize in the absence of rotating parts or transitions to other waveguides at the opening. Another effect of the round shape is that even when in one Gargeräteinnenraum inevitable warming of an outer conductor of the microwave structure less tension than in other forms occur. In comparison to a microwave guide structure which has a round cross-sectional shape over its entire length, the coupling of a microwave generator or another waveguide in the two-part embodiment of the microwave guide structure according to the invention is structurally simpler to implement. Because of the tightness of the microwave guide structure, a higher microwave power compared to a microwave line with a coaxial cable can be transmitted.

When the second portion has a substantially circular cross section, the outer conductive wall of the microwave conducting structure has the smallest possible circumference for a diameter dictated by the wavelength of the microwaves to be guided. If the second section extends into the opening in the wall of the interior, the opening is easy to make, for example. By drilling. In addition, a seal between Mikrowellenleitstruktur and wall is easy to implement, because circular sealing elements for circular cylindrical tubes are common.

If the first section has a rectangular cross-section, the coupling of a microwave generator or another waveguide is easy to implement, for example by simple attachment to a flat wall. In addition, the propagation modes of microwaves are well defined in a rectangular conductor. In addition, the coupling of microwaves, such as an antenna or probe to realize with little loss.

If the first section comprises a waveguide over at least part of its length, an antenna, e.g. the antenna of a magnetron or other microwave source, are introduced into the first section.

If there is at least one slot antenna at the end of the second section, it does not necessarily have to have a rectangular shape. It is also possible to provide a plurality of crossed slot antennas or an antenna in the form of a helical opening.

If the second section comprises an inner conductor forming a coaxial conductor with the outer wall over at least part of its length, the outer diameter of the second Section be particularly small depending on the microwave wavelength. If the TE ₁₀ waves were coupled from a rectangular waveguide into a circular waveguide without an inner conductor, where they propagate as TE ₁₀ waves, then a round waveguide with a fairly large diameter would be required. With a coaxial waveguide in the second section, the waves can be easily guided over an antenna projecting into the first section into the second section.

If the inner conductor extends as far as the first section and if an end of the inner conductor located in the first section is fastened to a wall of the first section, then with sufficient rigidity of the inner conductor its position is largely determined without requiring additional measures, such as webs, in the first section is required.

If the inner conductor is bent within the first portion, in particular over an angle of approximately 90 ° or more, attachment to a nearby wall of the first portion is made possible and the first portion need not be designed as a coaxial conductor. In addition, more energy can be absorbed via the bent end acting as a receiving antenna.

If the element for emitting the microwaves into the interior comprises an antenna and the inner conductor merges at its end into the antenna, the function of the element is realized in a structurally simple manner.

If the end of the inner conductor is provided with mechanical fastening means, in particular a thread, for the detachable connection of the antenna to the end of the inner conductor, the installation conditions can be taken into account via the selection of the antenna, without the microwave guide structure or structures being manufactured in different designs have to. Thus, the selection of the antenna material and / or their shape can be varied. If the antenna is heavily soiled or otherwise impaired, it can easily be cleaned and / or replaced without having to remove the microwave guide structure.

If the end of the inner conductor forms a rod antenna projecting through an opening in the wall of the inner space, then it may for example form a λ / 4 or λ / 2 rod antenna. This embodiment has the advantage of a simple construction, since essentially only an elongated inner conductor of the second section is required.

When the second portion is filled over at least part of its length with a material, in particular a dielectric, having a permittivity different from the permittivity of air, an impedance matching can be implemented without, in particular, adapting the dimensions of the outer conductive wall of the second portion Need to become.

If the second section is filled over only a part of its length with a material having a permittivity that deviates from the permittivity of air, further parameters for impedance matching are available without the dimensions of the second section having to be varied, in particular increased. In fact, between the material-filled part of the second section and the first section, the element of selectable length is connected in series. The position of the transition to the material filled part can be varied over the length.

A disc of dielectric material located at the end of the second section extending to at least the outer electrically conductive wall of the microwave guide structure allows microwaves to be coupled out of the waveguide without much energy being reflected at the end. There is also provided an at least partial seal to the interior atmosphere and a suitable material selection, a thermal insulation. In the case that the first section comprises an inner conductor, the inner conductor can be supported by the disc and positioned so.

Located between the disc and the outer electrically conductive wall, an elastic sealing element, then the disc itself may be relatively stiff. In particular, it may be made of a material such as glass. The microwaves are thus guided into the interior with little loss, and nevertheless a largely gas-tight seal is provided.

A hood which surrounds or covers the element towards the interior from a material which is substantially permeable to microwaves, in particular dielectric material, makes it possible to make the second section of the waveguide structure not very gastight, because with the Hood an additional seal against vapors and hot air is provided from the interior.

If there is a support in the hood for guiding a rod antenna, the rod antenna can be a continuation of an inner conductor, wherein almost or no positioning structures are provided in the second section of the waveguide structure.

If a flow guide is arranged in the interior, which at least partially divides the interior into the cooking chamber and a pressure chamber, a fan wheel is arranged in the pressure chamber, the Strömungsleitglied with at least one, in particular centrally disposed, opening for sucking atmosphere from the oven, in the pressure chamber is provided and the Strömungsleitglied between the pressure chamber and the cooking chamber, in particular at the edge region of the Strömungsleitglieds, at least one air-permeable compound leaves free, then forming the pressure chamber and the cooking chamber two coupled resonators for microwaves. Therefore, it is irrelevant in which of the two parts of the interior, the microwaves are first radiated. By the above-defined arrangement, a circulation of the gases is achieved in the interior. This allows a further form of influencing the cooking chamber climate. For example, a steam injection device may be provided, which injects steam into the atmosphere sucked from the cooking chamber, or an electric or a gas heater for heating the sucked-in atmosphere. In particular, in cooking appliances for commercial use, the homogenization of the cooking chamber climate, which comes about through the circulation, is advantageous.

If the at least one microwave guide structure is provided on an outer side of a side wall of the interior, in particular a side wall of a pressure chamber arranged next to the cooking chamber, preferably in an installation space which additionally contains drive means for a fan wheel located in the pressure space, wherein in particular the microwave guide structure microwaves up to at least an opening in the side wall, which is at an angle to a projected by a drive shaft of the fan side wall, leads, the fan will reflect the radiated into the interior of microwaves and swirling by its rotation. It is thus an additional function in an efficient way by the cooking appliances, in particular Kombinationsgargeräten, anyway already existing fan provided, namely the microwave uniformity and / or mode mixture. Analogous embodiments apply to the attachment of the microwave guide structure on a side wall part, in which case there are additional adjustment options for aligning the radiated microwaves on the exact position of the side wall part.

The arrangement of the Mikrowellenleitstruktur on an outer side of a side wall instead of the ceiling of the interior allows to keep the size of the cooking appliance low. In certain embodiments, two cooking devices may then be stacked on top of each other. In comparison to an arrangement of the microwave guide structure in the bottom region of the cooking appliance, the lateral arrangement does not impose such high demands on the seal to the interior. In fact, in the bottom area, processes for liquids are usually provided. In an arrangement in a common electrical installation space electrical connections can be shared. In addition, in the case only one room gas-tight seal and accessible for maintenance.

The guiding of the microwaves to at least one opening in a wall or wall part which is at an angle to another wall or other wall part through which projects a drive shaft of the fan wheel, allows the microwaves in the direction of the fan, but laterally past the same, radiate. They are not shielded from the interior and they are well swirled. The wall at an angle does not need to be long, because thanks to the use of the microwave guide structure behind her no space for a microwave generator must be provided so that a wall part is sufficient.

If the cooking appliance comprises a multiplicity of microwave guide structures, which are preferably arranged at different heights in the cooking appliance and in each case communicate with at least one of a plurality of magnetrons, in particular with a respective nominal power of at most 2000 W HF, magnetrons can be used for microwave appliances for private use be resorted to. If a plurality of treatment levels in the cooking space are determined by means of a food support device, and a number of treatment areas that are determined by the dimensioning of the cooking space and / or the number of treatment levels Microwave sources provided, then commercial microwave sources can be used easily. Thus, commercially available components can also be used in cooking appliances for large-scale kitchen use, without sacrificing the uniformity of a microwave energy distribution.

If the cooking device comprises at least one sensing device, a display device, an operating device and a control or regulating device, which is in particular in operative connection with a microwave source, a further treatment device, the display device and / or the operating device, food can be subjected to a complicated combination treatment, without requiring human intervention or human oversight.

Further features and advantages of the invention will become apparent from the following detailed description of some embodiments of the invention with reference to schematic drawings.

Figur 1

eine Längsschnittansicht eines Teils eines erfindungsgemäßen Gargeräts von vorne;

Figur 2

eine Querschnittansicht eines Teils des Gargeräts der Figur 1 von oben;

Figur 3

eine perspektivische Ansicht einer ersten Mikrowellenleitstruktur mit einem Element zum Abstrahlen von Mikrowellen in den Innenraum des Gargeräts der Figuren 1 und 2;

Figur 4

eine Rückansicht der Mikrowellenleitstruktur der Figur 3;

Figur 5

eine Seitenansicht der Mikrowellenleitstruktur der Figuren 3 und 4;

Figur 6

eine stirnseitige Ansicht der Mikrowellenleitstruktur der Figuren 3-5;

Figur 7

eine Längsschnittansicht der Mikrowellenleitstruktur der Figuren 3-6;

Figur 8

eine perspektivische Ansicht einer zweiten Mikrowellenleitstruktur mit einem Element zum Abstrahlen von Mikrowellen in den Innenraum des Gargeräts der Figuren 1 und 2 und mit einer das Element umgebenden Haube;

Figur 9

eine Rückansicht der Mikrowellenleitstruktur der Figur 8;

Figur 10

eine stirnseitige Ansicht der Mikrowellenleitstruktur der Figuren 8 und 9 ;

Figur 11

eine Seitenansicht der Mikrowellenleitstruktur der Figuren 8-10;

Figur 12

eine Längsschnittansicht der Mikrowellenleitstruktur der Figuren 8-11;

Figur 13

eine Längsschnittansicht einer dritten Mikrowellenleitstruktur; und

Figur 14

eine Längsschnittansicht einer vierten Mikrowellenleitstruktur.

Showing:

FIG. 1

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

FIG. 2

a cross-sectional view of a portion of the cooking appliance of FIG. 1 from above;

FIG. 3

a perspective view of a first Mikrowellenleitstruktur with an element for emitting microwaves in the interior of the cooking appliance of Figures 1 and 2 ;

FIG. 4

a rear view of the Mikrowellenleitstruktur the FIG. 3 ;

FIG. 5

a side view of the microwave guide structure of FIGS. 3 and 4 ;

FIG. 6

an end view of the Mikrowellenleitstruktur the Figures 3-5 ;

FIG. 7

a longitudinal sectional view of the microwave guide structure of Figures 3-6 ;

FIG. 8

a perspective view of a second microwave guide structure with an element for emitting microwaves in the interior of the cooking appliance of Figures 1 and 2 and with a hood surrounding the element;

FIG. 9

a rear view of the Mikrowellenleitstruktur the FIG. 8 ;

FIG. 10

an end view of the Mikrowellenleitstruktur the FIGS. 8 and 9 ;

FIG. 11

a side view of the microwave guide structure of Figures 8-10 ;

FIG. 12

a longitudinal sectional view of the microwave guide structure of Figures 8-11 ;

FIG. 13

a longitudinal sectional view of a third Mikrowellenleitstruktur; and

FIG. 14

a longitudinal sectional view of a fourth Mikrowellenleitstruktur.

One in the Figures 1 and 2 exemplified cooking appliance 1 according to the invention comprises one of 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 part 8 limited interior, wherein the rear wall 2 and the front edge 6 in principle be marked as sidewalls. The interior is at least partially divided by a flow 9 in a cooking chamber 10 and a pressure chamber 11 in the front wall 6 is a non-illustrated door for loading the cooking chamber 10 with food (not shown) and removal thereof.

In the cooking chamber 10, a frame 12 with a plurality of rails 13a-f for the insertion of Gargutträgem (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 from the cooking chamber 10 through an opening 17 located in a central region of the flow guide 9 and blows the atmosphere 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 the Strömungsleitglieds 9 and on the one hand the ceiling 3 and on the other hand, the bottom surface 4 again led into the cooking chamber 10. In addition or as an alternative to the slots 18, openings in the flow-guiding member 9 can also be provided in the edge region of the flow-guiding member 9.

The illustrated cooking appliance 1 comprises a microwave heating device and a further device (not shown) for treating the food in the cooking chamber 10. For example, an electric heating device, a gas-operated heating device, a heat exchange device, a cooling device, a moisture supply device and / or a moisture removal device can be provided. The electric or gas-operated heating device or the heat exchange device can wholly or partially surround the fan wheel 14 for heating the conveyed atmosphere. The moisture removal device is preferably located in a bottom region 19. The moisture supply device may comprise, for example, a steam generator or a steam injection device, which injects the steam into the medium conveyed by the radial fan impeller 14.

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

The microwave heating device in the illustrated embodiment comprises two magnetrons 22, 23 which generate microwaves passing over respective waveguide structures 24, 25 be fed into the interior. In the in the Figures 1 and 2 As shown, the microwaves are radiated 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, a uniform distribution of the radiated microwave energy in the cooking chamber 10 takes place in the pressure chamber 11. The coupling of the cooking chamber 10 and the pressure chamber 11 takes place essentially via the slots 18 and the opening 17, which are also provided for circulating the sucked from the cooking chamber 10 atmosphere. In addition, openings (not shown) for microwave-permeable openings may be provided in the flow-guiding member 9. In order to maintain the pressure difference between the pressure chamber 11 and the cooking chamber 10, such openings are generally not permeable to air, but filled with dielectric material, such as quartz glass, tempered borosilicate glass (Pyrex) or ceramic.

The radial fan 14 is at least partially made of a material that reflects microwaves. This also applies to the walls 2, 3, 4, 5, 6, 7, 8 and the frame 12. The microwaves are emitted via gates 26, 27 in the pressure chamber 11. These doors 26, 27 are located in the side wall part 8 which is disposed adjacent to the side wall 7 through which the drive shaft 15 of the radial fan 14 projects. The radial fan 14 extends with respect to the drive shaft 15 in the radial direction to maximally the transition from the side wall 7 to the side wall portion 8, so that the gates 26, 27 are not shielded by the fan 14. It is explained below that are provided for the emission of microwaves elements in the form of antennas. The radiation characteristic of the antennas is such that at least one emission takes place parallel to the side wall part 8. The thus radiated microwaves therefore reach the radial fan 14 and are reflected and swirled by it, which leads to a homogenization by mode mixing and supports the distribution of the microwave energy in the cooking chamber 10.

Even if the cooking appliance 1 is designed for large kitchen use, for commercial reasons, commercially available magnetrons 22, 23, which are designed for use in household microwave appliances, are used. These have a nominal power of about 2000 W HF. Nevertheless, sufficient heat input into food in the To reach cooking chamber, the number of magnetrons 22, 23 and Mikrowellenleitstrukturen 24, 25 according to the number of rails 13a-f in the frame 12, that is, depending on the number and dimensions of the recordable food supports, determined. In order to realize an even more uniform microwave energy distribution, the gates 26, 27 are provided at different heights. For this reason, in the example shown, a waveguide structure 24, 25 is assigned a respective magnetron 22, 23. In an alternative embodiment, however, it could be several, eg two microwave generators per waveguide structure 24, 25 at two ports 26, 27th

The use of the Mikrowellenleitstrokturen 24, 25 makes it possible to keep the side wall portion 8 relatively small, since the magnetrons 22, 23 may not necessarily be located immediately behind the same in the installation space 20. This in turn allows the use of a larger radial fan 14 and / or a further heating or heat exchange device surrounding the radial fan 14.

In the cooking chamber 10 of the cooking appliance 1, in particular when it has been designed for large-scale kitchen use, sometimes extreme conditions prevail. In particular, the humidity may be high and the temperature may reach values of about 400 ° C. The installation space 20 and the components located therein, in particular the magnetrons 22, 23, should be protected from this atmosphere.

A first Mikrowellenleitstruktur 28, which can be used as Mikrowellenleitstruktur 24, 25 in the cooking appliance 1 is in the Figures 3-7 shown. It comprises a first portion comprising a rectangular waveguide 29 and a second portion 30 composed of a first portion 31 with a cylindrical, circular outer wall and a coupling 32. The diameter of the circular outer wall is smaller than the distance between two parallel Walls of the rectangular waveguide 29. The outer wall of the coupling 32 has on the inside and on the outside at least in the region of an opening in the side wall part 8 (FIG. FIGS. 1, 2 ) also has a circular cross section. The connection from the first part 31 of the second portion 30 to the rectangular waveguide 29 is realized by means of a threaded bush 33 (see FIG. 7 ).

In a substantially flat wall 34 of the rectangular waveguide 29 is an opening 35 with attachment means, e.g. in the form of a thread 36 for screwing on a magnetron 22, 23. The magnetron antenna (not shown) protrudes into the rectangular waveguide 29 acting as a resonator cavity after being screwed through the opening 35 due to the fact that the opening 35 is in a substantially flat Wall 34 is mounted, it is relatively easy to attach the magnetron 22, 23 to the waveguide structure 28.

In the first microwave guide structure 28, the second section 30 comprises a circular waveguide with an inner conductor 37, that is to say a coaxial conductor. The inner conductor 37 extends into the rectangular waveguide 29, as in the FIG. 7 you can see. It is bent there by approximately 90 °, and fastened at a first end 38 by means of a screw 40 to a wall 39 of the rectangular waveguide 29. However, the inner conductor 37 is not conductively connected to the magnetron antenna but functions as a receiving antenna for microwaves emitted by the magnetron antenna into the rectangular waveguide 29.

In the area of the coupling 32 is a disc 41 made of a non-elastic dielectric material, e.g. Quartz glass, borosilicate glass or ceramic. The disk 41 seals the waveguide structure 28 in the region between the outer conductive wall and the inner conductor 37 toward the cooking chamber. The disc 41 is sealed relative to the coupling 32 by means of a sealing element of an elastic material, here in the form of an O-ring 42 which is located in a groove in the disc 41. The disk 41 also centers the inner conductor 37 in the second section 30 of the waveguide structure 28.

In the design of the microwave guide structure 28, impedance matching between the rectangular waveguide 29 and the second section 30 of the microwave guide structure 28 can be made via the thickness of the disk 41, which is made of a material having a permittivity that deviates from the permittivity of air. as well as the way over the length of the first part 31 of the second portion 30th

The microwave guide structure 28 is connected to the side wall part 8 of the interior of the cooking appliance 1 (FIG. Figures 1,2 ) is connected via the coupling 32. The coupling 32 becomes this Purpose passed through a round opening in the side wall portion 8 until it is supported on its outer side via a flange 43 on the side wall portion 8, on the outside thereof. On the inside of the wall there is a flat gasket 44 and a union nut 45 for gas-tight sealing of the installation space 20 with respect to the pressure chamber 11. The flat gasket 44 has the advantage over O-rings of a higher temperature resistance.

At a second end 46 of the inner conductor 37 is in an antenna 47 for emitting the microwaves in the pressure chamber 11 of the cooking device 1 via. The antenna 47 is a fixedly positioned rod antenna, e.g. a λ / 4 or λ / 2 dipole antenna. Since the antenna 47 and the second end 46 are provided with cooperating threads, another type of antenna can be used. In particular, a fixedly positioned circularly polarized antenna, such as a helical antenna, may also be used.

A second microwave guide structure 48, which can be used as Mikrowaveleitstruktur 24, 25 in the cooking appliance 1, is in the Figures 8-12 shown. It comprises a first section comprising a rectangular waveguide 49 and a second section 50 composed of a first part 51 with a cylindrical circular outer wall and a coupling 52. The diameter of the second portion 50 is smaller than the distance between two parallel walls of the rectangular waveguide 49. The outer wall of the coupling 52 has on the inside and on the outside at least in the region of an opening in the side wall part 8 (FIGS. FIGS. 1, 2 ) has a circular cross section. The connection from the first part 51 of the second portion 50 to the rectangular waveguide 49 is realized by means of a threaded bush 53 (see Fig. 12 ).

In a substantially flat wall 54 of the rectangular waveguide 49 is an opening 55 with attachment means, e.g. a thread 56 for screwing on a magnetron 22, 23. The magnetron antenna (not shown) of the screwed magnetron 22, 23 protrudes through the opening 55 into the rectangular waveguide 49 inside. This works as a resonator room.

Also in the second microwave guide structure 48, the second section 50 comprises a circular waveguide with an inner conductor 57, ie a coaxial conductor. The inner conductor 57 extends It is bent there by approximately 90 ° in order to be able to be fastened at a first end 58 to a wall 59 of the rectangular waveguide 49 by means of a screw 60.

In the area of the coupling 52, no disc of a dielectric material is located in the second microwave conducting structure 48. Instead, a hood 61 of dielectric material is used to seal against the cooking chamber atmosphere. The material should also have a low thermal conductivity so that materials such as glass, e.g. Quartz glass or borosilicate glass, or steatite offer. Glass has a lower permittivity compared to ceramic materials.

Although a further seal in the region between the inner conductor 57 and the inner wall of the coupling 52, and the first part 51 of the second portion 50 can be made, eliminating in principle the need to seal such a hole, mainly because of the different expansion coefficients of the coupling material and the material of a dielectric sealing disc is desired.

The hood 61 is supported on the coupling 52 via a flange 62 and a flat gasket 63. In an alternative embodiment, it could similarly be supported on the wall of the interior. The hood 61 is pressed with a union nut 64 against the coupling 52 at the end of the second portion 50 of the microwave guide structure 48 and sealed by a second flat seal 65 against the cooking chamber atmosphere.

The coupling 52 connects the Mikrowellenleitstruktur 48 with the side wall portion 8 of the interior of the cooking appliance 1 ( FIGS. 1, 2 ). For this purpose, the clutch 52 is inserted through a round opening in the side wall part 8 during assembly. It is supported on the outside of the side wall part 8 via a flange 66 of the coupling 52. On the inside of the side wall part 8 are for gas-tight sealing of the installation space 20 with respect to the pressure chamber 11, a flat gasket 67 and a second cap nut 68th

Also in the in the Figures 8-12 In the embodiment shown, the inner conductor 57 goes at a second end 69 into an antenna 70 for emitting the microwaves into the antenna Pressure chamber 11 of the cooking device 1 via. In this case, however, the antenna 70 is integrally connected to the end 69 of the inner conductor 57. As a result, there are fewer components and a jump is avoided. The antenna 70 is a fixedly positioned rod antenna, eg a λ / 4 or λ / 2 dipole antenna. Also in this embodiment, the antenna 70 may have a different shape. In particular, a fixedly positioned circularly polarized antennas, such as a helical antenna, can also be used here.

In the in the Figures 8-12 1, the inner conductor 57 is centered in the second section 50 of the microwave conducting structure 48 by means of a disk 71 of dielectric material, eg quartz glass or steatite. Alternatively or additionally, at least one support 72 in the hood 61 and / or for guiding the antenna 70 is located the hood has a bulge 61a. The position and thickness of the disc 71 may be used to match the impedance of the second section 50 to that of the rectangular waveguide 49 in the design of the second microwave guide structure 48.

A third microwave guide structure 73, which serves as a microwave guide structure 24, 25 in the cooking appliance 1 (FIG. Figures 1 and 2 ) can be used in the FIG. 13 shown very schematically. It includes a first section in the form of a right-hand waveguide 74. A magnetron antenna (not shown) transmits microwaves into the rectangular waveguide 74.

A cylindrical second section 75 includes a conductive outer wall 76 having an integral coupling 77 which passes through an opening in a wall 78, preferably in the side wall portion 8, of the interior of the cooking appliance 1. The outer wall 76 and the wall of the coupling 77 have a substantially circular cross-sectional shape. By means of a union nut 79 and a flat gasket 80, the second portion 75 is screwed to the wall 78.

In this case, a first end 82 of the inner conductor 81 forms a rod antenna located in the rectangular waveguide 74. This end 82 is to be regarded as a coupling pin. The length of the coupling pin can be varied. By this coupling, the second portion 75 may have a relatively small diameter. The wave of a TEM mode requires the smallest possible diameter in order to be able to propagate in a circular waveguide, and is therefore preferred. The inner conductor 81 additionally reduces the required minimum diameter. Still further, a substrate 83 of dielectric material is interposed between the inner conductor 81 and the outer conductor, thereby achieving further miniaturization.

With the length of the inserted substrate 83, a transformer that adjusts the impedance values between the rectangular waveguide 74 and the second portion 75 is realized. The substrate 83 with a permittivity which differs from the permittivity of air is therefore also provided over only a part of the length of the second section 75 for this reason.

On a facing the interior of the cooking appliance 1 end 84 of the inner conductor is a disc 85 of dielectric, microwave-permeable material. The disc 85 is secured by means of a union nut 86 and a flat gasket 87. In an alternative embodiment, the disk 85 is an integral part of the substrate 83.

The coupling 77 is screwed by means of a second union nut 79 and flat gasket 80 with the interior wall 78. Microwaves are emitted via the end 84 in a direct way (without reflections) in the pressure chamber 11.

In a variant of this embodiment, a hood (not shown), for example, like the hood 61 of the second embodiment, may be provided. In another variant (not shown), the inner conductor 81 can protrude through the disc 85 into the interior or be provided with a thread for screwing on an antenna, as in the first embodiment (see Figures 3-7 ).

The FIG. 14 shows very schematically the structure of a fourth Mikrowellenleitstruktur 88, as Mikrowellenleitstruktur 24, 25 in the cooking appliance 1 of Figures 1 and 2 It also includes a first section in the form of a rectangular waveguide 89. A magnetron antenna (not shown) transmits microwaves into the rectangular waveguide 89.

A cylindrical second portion 90 comprises a conductive outer wall 91 having an integral, through an opening in a wall 93, in particular the side wall portion 8, the interior of the cooking device 1 passed through coupling 92. The outer wall 91 and the wall of the coupling 92 have a in Essentially circular cross-sectional shape. through a union nut 94 and a flat gasket 95, the second portion 90 is screwed to the wall 78.

The second section 90 here comprises no coaxial conductor, but a circular waveguide. However, the circular waveguide is only "hollow" in the sense that it does not contain an inner conductor. Over a part of the length, the second section 90 is filled with a substrate 96 of dielectric material. Thus, also in this embodiment, a transformer which adjusts the impedance values between the rectangular waveguide 89 and the second portion 90 is realized. The substrate 96 has a permittivity that deviates from the permittivity of air.

A slot antenna 97 is located at an end of the second section 90 facing the interior of the cooking appliance 1. The slot antenna 97 comprises a rectangular opening in a conductive end wall 98 of the microwave guide structure 88. In variants of this embodiment, a slot antenna 97 having a different shape may be used. For example, a phillips antenna, a T-shaped slot antenna, or a spiral slot antenna can be used.

In the illustrated embodiment, between the substrate 96 and the slot antenna end wall 98 is still provided a seal 99 of a microwave transparent material. The function of the seal can also be taken over by the substrate 96.

In a (not shown) variant of in the FIG. 14 In the illustrated embodiment, the second portion 90 does not include the conductive end wall 98, but the slot antenna 97 is mounted in the cabin wall 93. The microwave guide structure 48 then only guides the microwaves to an outer side of the interior wall 93.

In a further (not shown) variant of the fourth embodiment, a hood, such as the hood 61 of the second embodiment may be additionally provided.

Common to the embodiments described above is that the opening required for feeding in microwaves in the side wall part 8 of the interior is relatively small. This one Opening is also round, the whole system can be easily connected mechanically (eg via union nut) and seal, especially on flat gaskets. Due to the small cross-section of the coaxial conductor formed by the second section, a good thermal decoupling of the magnetron and cooking chamber can furthermore be realized and thermal bridges are minimized.

LIST OF REFERENCE NUMBERS

1

Cooking appliance

2

rear wall

3

blanket

4

floor area

5

1st sidewall

6

front wall

7

2nd side wall

8th

Sidewall portion

9

flow directing

10

oven

11

pressure chamber

12

frame

13a-13f

rail

14

radial fan

15

wave

16

engine

17

opening

18

slot

19

floor area

20

installation space

21

Side wall of the cooking appliance

22

1. Magnetron

23

2. Magnetron

24

1. microwave conducting structure

25

2. microwave guide structure

26

1st door

27

2nd door

28

Mikrowellenleitstruktur

29

Rectangular waveguide

30

2nd section

31

Part 1 of Section 2

32

clutch

33

threaded bushing

34

Wall of the rectangular waveguide

35

Opening in the wall of the rectangular waveguide

36

Thread on the opening

37

inner conductor

38

1. end of the inner conductor

39

Wall of the rectangular waveguide

40

screw

41

disc

42

O-ring

43

flange

44

gasket

45

Nut

46

Inner conductor end

47

antenna

48

Mikrowellenleitstruktur

49

Rectangular waveguide

50

2nd section

51

Part 1 of Section 2

52

clutch

53

threaded bushing

54

Wall of the rectangular waveguide

55

Opening in the wall

56

Thread on the opening

57

inner conductor

58

1. end of the inner conductor

59

Wall of the rectangular waveguide

60

screw

61

Hood

61a

Hood bulge

62

Flange of the hood

63

gasket

64

Nut

65

gasket

66

flange

67

gasket

68

Nut

69

Inner conductor end

70

antenna

71

disc

72

support

73

Mikrowellenleitstruktur

74

Rectangular waveguide

75

2nd section

76

outer wall

77

clutch

78

Interior wall

79

Nut

80

gasket

81

inner conductor

82

Inner conductor end

83

substratum

84

Inner conductor end in the area of the interior

85

disc

86

Nut

87

gasket

88

Mikrowellenleitstruktur

89

Rectangular waveguide

90

2nd section

91

outer wall

92

clutch

93

Interior wall

94

Nut

95

gasket

96

substratum

97

slot antenna

98

end wall

99

poetry

Claims (20)

1. Cooking apparatus (1) comprising:

   a cavity (10,11) comprising at least one cooking chamber (10), and at least one microwave guiding structure (24,25;28;48;73;88) for guiding microwaves from at least one microwave source (22,23) at least to an opening in a wall or in a wall part (8;78;93) of the cavity (10,11), wherein the microwave guiding structure (24,25;28;48;73;88) has external electrically conductive and rigid walls (31,32,34,39;51,52,54;76;77;91;92,99) and at least one element (47;70;84;97) for radiating the microwaves into the cavity (10,11),
   wherein

   the microwave guiding structure (24,25;28;48;73;88) comprises a first portion (29;49;74;89) having a first cross-sectional shape of its external electrically conductive walls (34,39;54,59) and a second portion (30;50;75;90) having a second cross-sectional shape, characterized in that

   the second cross-sectional shape is essentially round, circular in particular, and differs from the first cross-sectional shape, and

   the element (47;70;84;97) is arranged on an end of the second portion (30;50;75;90).
2. Cooking apparatus according to claim 1, characterized in that
   the first portion (29;49;74;89) has a rectangular cross-sectional shape
   and/or
   comprises a waveguide over at least part of its length.
3. Cooking apparatus according to claim 1 or 2, characterized by
   at least one slot antenna (97) located at the end of the second portion (90).
4. Cooking apparatus according to any one of the preceding claims, characterized in that the second portion (30;50;75) comprises, over at least part of its length, an internal conductor (37;57;81) that forms, together with the external walls, a coaxial conductor.
5. Cooking apparatus according to claim 4, characterized in that
   the internal conductor (37;57;81) extends into the first portion (29;49;74;89), wherein an end of the internal conductor (37;57) is preferably fastened to a wall (39;59) of the first portion (29;49;74;89), said end being located in the first portion (29;49;74;89).
6. Cooking apparatus according to claim 4 or 5, characterized in that the internal conductor (37;57) is curved within the first portion (29;49;74;89), in particular over an angle of approximately 90 degrees or more.
7. Cooking apparatus according to any one of claims 4 to 6, characterized in that the element for radiating the microwaves into the cavity (10,11) comprises at least one antenna (47;70;84), wherein the internal conductor (37;57;81) preferably merges, at its end, into the antenna (47;70;84).
8. Cooking apparatus according to claim 7, characterized in that
   the end of the internal conductor (37) is provided with mechanical fastening means, particularly a thread, for detachably connecting the antenna (47) to the end of the internal conductor (37), or
   the end of the internal conductor (57) forms a rod antenna (70) extending through an opening in the wall of the cavity (10,11), or
   the end (84) of the internal conductor (81), particularly in the region of the opening in the wall of the cavity (10,11), directly radiates microwaves.
9. Cooking apparatus according to any one of the preceding claims, characterized in that the second portion (30;50;75;90) is filled, over at least a part arranged adjacent to the microwave radiation region and/or at the end of the second portion (30;50;75;90), particularly over only part of its length, with a material, a dielectric material in particular, having a permittivity deviating from the permittivity of air, preferably in the form of a disk (41;71) or of a substrate (83,96) and/or for adapting the impedances of the two portions (50;74,75;89,90).
10. Cooking apparatus according to claim 9, characterized in that
    the disk (41;71) extends at least to the external electrically conductive walls of the second portion (30;50), wherein at least one elastic sealing element (42;63) is located particularly between the disk (41;71) and the external electrically conductive walls.
11. Cooking apparatus according to any one of the preceding claims, characterized by a cover protecting the element (47;84) toward the cavity (10,11), particularly in the form of a hood (61) or of a disk (85) made of a material that essentially conducts microwaves and is preferably dielectric.
12. Cooking apparatus according to claim 11, characterized by
    at least one support (72,61a) in the or through the hood (61) for guiding the element (70).
13. Cooking apparatus according to any one of the preceding claims, characterized in that a flow conduction member (9) is arranged in the cavity (10,11), said flow conduction member (9) at least partially dividing the cavity into the cooking chamber (10) and a pressure chamber (11),
    wherein a ventilator wheel (14) is arranged in the pressure chamber (11),
    the flow conduction member (9) is provided with at least one, particularly centrally arranged, opening (17) for the suction of atmosphere from the cooking chamber (10) into the pressure chamber (11) and
    leaves, between the pressure chamber (11) and the cooking chamber (10), particularly at the edge region of the flow conduction member (9), room for at least one, particularly slot-shaped, connection (18) for blowing atmosphere out of the pressure chamber (11) into the cooking chamber (10).
14. Cooking apparatus according to claim 13, characterized in that the microwave guiding structure (24,25;28;48;73;88) guides microwaves at least to an opening in a wall or in a side wall part (8), said wall or side wall part (8) being arranged at an angle, at an obtuse angle in particular, with respect to a wall through which a drive shaft (15) of the ventilator wheel (14) extends or with respect to a side wall (7) through which a drive shaft (15) of the ventilator wheel (14) extends, wherein, preferably, the opening in the wall or in the side wall part (8) is directed or directable toward the opening (17) arranged in the flow conduction member (9) or toward a connection (18) that is pervious to air.
15. Cooking apparatus according to any one of the preceding claims, characterized in that the at least one wave guiding structure (24,25;28;48;73;88) is fastened, by means of a flange (43;66;77;92) in particular, to an outer surface of a side wall or of a side wall part (8;78;93) of the cavity (10,11) and/or is fastened to a side wall or a side wall part (8;78;93) of a pressure chamber (11) arranged next to the cooking chamber (10), particularly in an installation chamber (20) that additionally contains drive means (16) for a ventilator wheel (14) that is located in the pressure chamber (11).
16. Cooking apparatus according to any one of the preceding claims, characterized by a plurality of microwave guiding structures (24,25;28;48;73;88) that are preferably arranged at different heights in the cooking apparatus (1) and/or each connected to at least one of a plurality of magnetrons (22,23) preferably having a rated power of up to 2000 W HF.
17. Cooking apparatus according to any one of the preceding claims, characterized by at least one further device for the processing of food to be cooked in the cooking chamber, particularly at least one device from the group comprising:

    an electric heating device,

    a gas powered heating device,

    a heat exchanger,

    a cooling device,

    a moisture supply device,

    a moisture removal device,

    an aerator, and

    a deaerator.
18. Cooking apparatus according to any one of the preceding claims, characterized by at least one sensing device, a display device, an operating device and an open-loop or closed-loop control device that, in particular, is operatively connected to a microwave source (22,23), the further processing device, the display device and/or the operating device.
19. Method to provide microwaves inside the cavity (10,11) of a cooking apparatus (1), particularly of a cooking apparatus (1) according to any one of the preceding claims, comprising:

    providing a microwave guiding structure (24,25;28;48;73;88) with external electrically conductive and rigid walls (31,32,34,39;51,52,54;76,77;91,92,99) for guiding microwaves at least to an opening in a wall of the cavity (10,11), and

    radiating microwaves via an element (47;70;84;97) located at an end of the wave guiding structure (24,25;28;48;73;88),

    characterized in that

    the microwaves are guided in the microwave structure (24,25;28;48;73;98) to the cavity (10,11) via a second portion (30;50;75;90) arranged adjacent to the end and having a round cross-sectional shape and via a first portion (29;49;74;89) having a cross-sectional shape differing therefrom and arranged upstream in the direction of propagation of the microwaves.
20. Method according to claim 19, characterized in that
    a plurality of processing levels in the cooking chamber (10) is fixed by means of a food-to-be-cooked supporting device (12,13a-13f) and a number of microwave sources (22,23) are provided, said number depending on the dimensioning of the cooking chamber (10) and/or on the number of processing levels.

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