Cooking appliance with microwave function and microwave traps

Abstract

The invention relates to a cooking appliance comprising: a housing (2) with a cooking chamber (3), the cooking chamber (3) having a cooking chamber opening, a cooking chamber door (5) for closing the cooking chamber opening, the cooking chamber door (5) having a viewing window (5.2) and at least one heating element for generating microwaves of a nominal frequency in the cooking chamber (3), the cooking chamber door (5) and the housing (2) forming a contact area (2.5) with each other, a surface of the housing (2) in the contact area (2.5) being metallic, a first seal (15) being formed on the cooking chamber door (5) and a first microwave trap (13) and a second microwave trap (14) being arranged one behind the other in the contact area (2.5), the microwave traps (13, 14) each being formed as a cavity (13.1, 14.1) with a trap opening (13.2, 14.2), the trap opening (13.2) the first microwave trap (13) is covered by the viewing window (5.2) and the trap opening (14.2) the second microwave trap (14) is covered by the first seal (15), wherein a second seal (17) is provided and arranged on the housing (2) in the contact area (2.5) and wherein the second seal (17) is made of glass silk.

Description

Technical FieldThe invention relates to cooking devices, in particular a cooking device, comprising: a housing having a cooking chamber bounded by housing walls, wherein the cooking chamber has a cooking chamber opening, a cooking chamber door for closing the cooking chamber opening, wherein the cooking chamber door has a viewing pane, and at least one heating means for generating microwaves of a nominal frequency in the cooking chamber.BACKGROUND OF THE INVENTIONCooking devices, in particular microwave devices and ovens with microwave function, are known from the prior art.In such cooking devices, in order to avoid hazardous persons in the environment of the cooking device, it is necessary to prevent microwave radiation from emerging. For this purpose, microwave traps in the form of cavities for coupling in varying microwave radiation are provided in the region of a door gap, so that the microwave radiation is prevented from emerging through the door gap. The resonant frequency of a microwave trap is also determined, among other things, by the gap dimension of the door gap. A microwave device with a microwave double trap is known, for example, from the publications DE 10 2022 201 198 A1 and US 2007 / 0 012 691 A1.It is also known to provide seals in cooking devices in the region of a door gap, as shown in the publications DE 36 07 557 A1 and EP 1 758 432 A2. Seals of this type serve in particular to prevent the escape of steam or emerging hot air. The tolerance of the door gap dimension is disadvantageously increased by the provision of such seals, so that the resonant frequency of the microwave trap may no longer match the nominal frequency of the microwave radiation used at any time and microwave radiation can subsequently emerge through the door gap.It is also a common requirement for the aforementioned cooking devices that they should be cleaned as simply as possible and also designed to be appealing in their design.DESCRIPTION OF THE INVENTIONBased on the background of the invention, it is an object of the present invention to reliably prevent microwave radiation from emerging in a cooking appliance with a microwave function and a door gap seal, wherein cleaning of the cooking appliance is intended to be possible in a simple manner.The object of the invention is achieved by the features of the independent main claims which define the invention in this respect. Advantageous embodiments are specified in the dependent claims. Insofar as technically possible, the teachings of the subclaims can be combined as desired with the teachings of the main and dependent claims.Advantages of the claimed aspects of the invention are explained below and preferred modified embodiments of the aspects of the invention are described below. Explanations, in particular regarding advantages and definitions of features, are basically descriptive and preferred, but non-limiting examples. Where an explanation is limiting, this is expressly mentioned.If ordinal numbers ("first", "second", etc.) are used, for example for designating a component, an element, a method step or a method action, these ordinal numbers are provided purely for differentiation in the designation and do not indicate dependencies or orders. That is to say, in particular, that, for example, a device does not have to have a "first component" in order to have a "second component". A device can also have a "first component" and a "third component", but without necessarily having a "second component". It is also possible to provide a plurality of units of the same ordinal number, that is to say, for example, a plurality of "first components".In particular, the object is accordingly achieved by a cooking appliance, comprising: a housing having a cooking chamber bounded by housing walls, wherein the cooking chamber has a cooking chamber opening, a cooking chamber door for closing the cooking chamber opening, wherein the cooking chamber door has a viewing pane and at least one heating means for generating microwaves of a rated frequency in the cooking chamber, wherein the cooking chamber door and the housing together form a contact region, wherein a surface of the housing is formed metallic in the contact region, wherein at least a first seal is formed on the cooking chamber door and a first microwave trap and a second microwave trap are formed in the contact region lying one behind the other, wherein the microwave traps are each formed as a cavity having a trap opening and wherein the trap opening of the first microwave trap is covered by the viewing pane and the trap opening of the second microwave trap is covered by the first seal.According to the invention, it is provided that a second seal is provided and arranged on the housing in the contact region, wherein the second seal is formed from glass silk.A cooking appliance is designed in particular as an oven with an integrated microwave (so-called combination appliance), in which temperatures of approximately 100-250° C., for example, are provided in the cooking chamber for preparing a product to be cooked. The cooking appliance can also be designed as an oven with a pyrolysis function and / or a steam cooking function. The cooking appliance can furthermore be designed as a steam cooker or as a microwave oven.The heating means for generating microwaves are designed, for example, as a magnetron or as a semiconductor element and, in addition to the means for generating the microwave radiation, also comprise means for coupling the microwave radiation into the cooking chamber, such as, for example, corresponding waveguides. The nominal frequency is in particular 2.45 GHz plus / minus 50 MHz. In particular, the geometry of the cooking chamber is designed such that the microwaves of the rated frequency form waves therein.A contact region is in particular formed as an abutment region which extends at least partially around the cooking chamber opening between an outer region of the cooking chamber door and front edges of the lateral cooking chamber walls. In this case, the housing forms a metallic contact surface in the contact region, opposite which the microwave traps on the door side are situated with the trap openings. The microwave traps extend corresponding to the extent of the contact region at least partially circumferentially around the cooking chamber opening and are thus channel-shaped. The trap openings then form a slot in each case. Insofar as the housing forms a metallic surface in the contact region, this can be the surface of a metallic component or a metallically coated surface of a component made of another material.Insofar as a trap opening is covered by the viewing pane or by the first seal, the trap opening is in particular tightly closed off, at least protected from the penetration of dirt and / or liquid, in particular of vapour or parts of the cooked product such as grease sprays. The viewing window and the first seal are designed to be transmissive for microwave radiation at least in the region in which they cover the trap openings, in order to ensure reliable coupling of the microwave radiation into the microwave traps.The solution of the object with the above-described cooking appliance thus comprises the teaching that in an outer region of the cooking chamber door, which is assigned to the contact region, a double microwave trap is formed, by means of which advantageously microwaves not only of a specific frequency can be prevented in a narrow band from emerging from the door gap, but can be prevented by means of the microwaves from emerging from the door gap over a specific, relatively wide band of frequencies. For this purpose, the microwave traps are designed at slightly different resonant frequencies, the distance between which determines the width of the band. It is achieved in this way that even in the case of the tolerance of the door gap dimension caused by the first seal and the associated displacement of the resonant frequencies of the microwave traps, the nominal frequency of the generated microwaves is always within the band and the microwaves generated by the heating means are thus reliably prevented from exiting the door gap.The solution further comprises the teaching that in the outer region of the cooking chamber door, the latter can be configured to be relatively compact, such that both microwave traps and the first seal can be arranged together in the region. The optical design of the cooking chamber door can thus be made relatively free of boundary conditions predefined by the microwave traps, so that a design that is perceived as advantageous is made possible. At the same time, the viewing window extends relatively far outwards and forms with the first seal a substantially planar surface which can be cleaned in a simple manner overall. As a result of the extension of the viewing pane outwards, that is to say as far as the trap opening of the first microwave trap, the region of the cooking chamber door which is primarily exposed to contamination from the cooking chamber is additionally largely or even completely covered by the completely planar viewing pane and therefore particularly easily cleaned.The arrangement of the first seal also achieves a relatively wide outer appearance and, to the extent that the requirements with regard to the temperature resistance of the first seal are moderate. Due to the distance from the cooking chamber, the temperatures prevailing in the region of the first seal are already significantly reduced compared to the cooking chamber temperature even at relatively high cooking chamber temperatures. Therefore, many materials can be used for forming the first seal, in particular also those which have particularly favorable sealing properties and service lives without, however, having particularly good temperature resistance.As an alternative to features of the solution described above or in a preferred embodiment of the solution described above, it is provided that the first seal is formed liquid-tight, in particular vapor-tight. A further seal can then be dispensed with in order to prevent air, vapor and / or liquid from escaping from the cooking chamber.As an alternative to features of the solution described above or in a preferred embodiment of the solution described above, it is provided that the first seal is formed from a silicone material. Such a material has particularly good sealing properties, in particular with respect to vapor and / or liquid, with a particularly good service life, wherein silicone materials have at least sufficient properties with respect to the temperature resistance in order to be arranged relatively far outside on the cooking chamber door. In addition, silicone materials have a favorable permittivity in order to form the second microwave trap with compact geometries at the necessary resonant frequencies in favor of a compactly formed cooking chamber door. In this case, the first seal acts as a dielectric there when covering the trap opening of the second microwave trap and thus also determines the oscillation behavior of the microwave trap.The microwave traps each behave like an LC resonant circuit, the inductance L of which is determined by the volume and the geometry and surface condition of the entire wall of the cavity, and the capacitance C of which is characterized by the input capacitance at the trap opening. At the trap opening, preferably two mutually opposite printed circuit boards form a capacitor. The capacitance is dependent on the permittivity between the material at the trap opening, which is determined by the material covering the trap opening, and the conductor material of the printed circuit boards on both sides of the trap opening. The resonant frequency ω 0( here angular frequency) of a microwave trap results in the capacitance C resulting from ε being the permittivity, A being the surface of the printed circuit boards at the trap opening and d being the width of the trap opening.As an alternative to features of the solution described above or in a preferred embodiment of the solution described above, it is provided that the viewing pane is formed from a glass material. A glass material is easy to clean and also has a favorable permittivity in order to form the first microwave trap with compact geometries at the necessary resonant frequencies. The glass can furthermore be printed in the region in which the viewing pane covers the first microwave trap, in order to avoid visibility of the first microwave trap. The pressure is then designed to be transmissive to microwave radiation.As an alternative to features of the solution described above or in a preferred embodiment of the solution described above, it is provided that the first microwave trap is designed for a resonant frequency below the nominal frequency and the second microwave trap is designed for a resonant frequency above the nominal frequency. It is then reliably prevented that microwave radiation of the rated frequency escapes both when the band is displaced upward and when the band is displaced downward, depending on the direction of the tolerance deviation of the door gap.As an alternative to features of the solution described above or in a preferred embodiment of the solution described above, it is provided that the cooking appliance has a second seal arranged on the housing in the contact region. Such a second seal is preferably formed on the inside relative to the first seal, i.e. closer to the cooking chamber, and can advantageously serve to keep particularly hot air away from the first seal. The requirements imposed on the first seal with regard to temperature resistance are thus reduced depending on the temperatures present in the cooking chamber. In particular, a second seal is provided in the case of a pyrolysis function provided in the cooking appliance, in order to keep the particularly hot air which arises in the process away from the first seal.In addition or in a manner complementary to the feature described immediately above, it is provided in a further embodiment of the solution that the second seal is formed from glass floss. Glass silk offers a particularly good temperature resistance and can thus also be arranged close to the cooking chamber at temperatures during a pyrolysis cleaning of the cooking chamber.In addition or in a manner complementary to the features described immediately above, it is provided in a further embodiment of the solution that the second seal is arranged in a groove formed on the housing in the contact region. The second seal is then held on the housing with a particularly secure fit and advantageously does not influence, or only insignificantly influences, the tolerance of the door gap dimension given a correspondingly designed arrangement.In addition or in a manner complementary to the features described immediately above, it is provided in a further embodiment of the solution that the second seal is arranged opposite the viewing pane on the housing. The second seal is then advantageously provided in a simple manner for bearing against the viewing window in the region of the first microwave trap when the cooking chamber door is closed, so that the contact region for the second seal does not have to be designed to be substantially larger in order to create a bearing region for the second seal.As an alternative to features of the solution described above or in a preferred embodiment of the solution described above, it is provided that the cooking appliance has a spring element for pressing the cooking chamber door onto the housing in the contact region in a closed state of the cooking chamber door. In this way, the tolerance of the door gap dimension is relatively low even in the case of a seal provided, so that the deviations of the resonant frequencies of the microwave traps from their design turn out to be small and the escape of microwaves of the rated frequency is reliably prevented. The spring element is particularly preferably arranged in a hinge of the cooking chamber door and interacts with the hinge.As an alternative to features of the solution described above or in a preferred embodiment of the solution described above, it is provided that at least one microwave trap has a protrusion projecting from the trap opening into the cavity, so that the trap opening is designed as a channel bounded on both sides. The projection and an outer wall of the microwave trap then form printed circuit boards which together form a particularly high input capacitance C of the microwave trap. For this purpose, the printed circuit boards are embodied to be metallically or at least metallically coated. Due to a high input capacitance C, the entire geometry of the microwave trap can be designed to be particularly compact, and the microwave trap is also particularly suitable for the entry of obliquely incident microwaves and microwaves of higher modes.In addition or in a manner complementary to the feature described immediately above, it is provided in a further embodiment of the solution that the projection is slit. As a result of the slitting, the microwave trap is designed with further improved properties with respect to obliquely incident microwaves and microwaves of higher modes.As an alternative to features of the solution described above or in a preferred embodiment of the solution described above, it is provided that the cooking appliance has means for providing a pyrolysis function. With regard to a pyrolysis function, the advantages achieved by the first seal and, if appropriate, the second seal are particularly relevant since potentially harmful vapors which are produced during pyrolysis are reliably prevented from emerging from the cooking chamber.Brief Description of the DrawingsThe invention is explained in more detail below with reference to the attached drawings on the basis of preferred exemplary embodiments. The formulation figure is abbreviated with Figure in the drawings.In the drawings, FIG. 1 shows a schematic view of a cooking appliance according to one aspect of the invention; FIG. 2 shows a detail view of a contact region between a cooking chamber door and a housing according to one aspect of the invention in a first embodiment; FIG. 3 shows a detailed view of a contact region between a cooking chamber door and a housing according to one aspect of the invention in a second embodiment; and FIG. 4 is a graph showing the frequency lowering by a single microwave trap and by a double microwave trap at a door gap.Detailed Description of the DrawingsThe described exemplary embodiments are merely examples which can be modified and / or supplemented in a wide variety of ways within the scope of the claims. Each feature described for a particular embodiment may be used independently or in combination with other features in any other embodiment. Each feature described for an embodiment of a particular claim category may also be used in a corresponding manner in an embodiment of a different claim category.FIG. 1 schematically shows a cooking appliance 1 designed as an oven with a housing 2, wherein a cooking chamber 3 surrounded by cooking chamber walls 2.1, 2.2, 2.3, 2.4 is formed in the housing 2. The cooking chamber 3 is accessible through a cooking chamber opening 4, in particular for the introduction and removal of items to be cooked, wherein the cooking chamber opening 4 can be closed by means of a cooking chamber door 5, which is shown in an open manner. In a closed state, the cooking chamber door 5 abuts the housing 2 in a contact region 2.5 circumferentially with respect to the cooking chamber 3. The cooking appliance 1 has heating means, for example a circulating air heating means 6 with a fan, not shown in detail, heating means 7.1, 7.2 for generating radiant heat in an upper and lower heating mode and heating means 8, shown in hidden form, for generating microwaves of a rated frequency w 0, wherein the heating means 8 is arranged such that the microwaves are coupled into the cooking chamber 3. The heating means 8 is, for example, a magnetron or a semiconductor generator. Built-in parts 9 with a food carrier 10 resting thereon are arranged in the cooking appliance 1. The cooking appliance 1 further comprises operating elements 11 and a display 12.FIG. 2 shows a contact region 2.5 between a closed cooking chamber door 5 and the housing 2 in a cross-sectional view in detail. The cooking chamber door 5 is substantially formed by a frame 5.1 and a viewing pane 5.2, which is formed for example from glass. The frame 5.1 forms a first microwave trap 13 and a second microwave trap 14 in the outer region of the cooking chamber door 5, wherein the microwave traps 13, 14 are each formed with a cavity 13.1, 14.1 and with a trap opening 13.2, 14.2. In addition, in the region of the trap openings 13.2, 14.2, a projection 13.3, 14.3 projects into the cavity 13.1, 14.1, respectively, which projection forms an input capacitance C with an opposite wall of the microwave trap 13, 14. The projection 13.3, 14.3 and the opposite wall are designed as metallically conductive printed circuit boards. The frame 5.1 also has an external closing fold 5.3 of the cooking chamber door 5.The trap opening 13.2 of the first microwave trap 13 is covered by the viewing window 5.2 and is protected by the viewing window 5.2 against the penetration of air, vapor and / or liquid, in particular dirt. The trap opening 14.2 of the second microwave trap 14 is covered by a first seal 15 and is protected by the first seal 15 against the penetration of air, vapor and / or liquid, in particular dirt. The first seal 15 bears as the only component of the cooking chamber door 5 against the metallically conductive surface of the housing 2 in the contact region 2.5 and seals the door gap T.The first seal 15 is formed from silicone, for example. Due to the relatively large distance from the cooking chamber 3, the temperature effectively present at the first seal 15, i.e. the thermal influence acting on the first seal 15 by the air and the surrounding components of the cooking appliance 1, is significantly reduced compared to the cooking chamber temperature. The use of a silicone seal is thus made possible without risk of thermal damage. Furthermore, the cooking chamber 3 and a part of the cooking chamber door 5 projecting relatively far into the contact region 2.5 are covered by the viewing pane 5.2, so that the region of the cooking chamber door 5, which is mainly affected by dirt from the cooking chamber 3, is substantially formed by the viewing pane 5.2 that is easy to clean.FIG. 3 shows a variant of a contact region 2.5 between a closed cooking chamber door 5 and the housing 2 in detail in a cross-sectional view which substantially corresponds to the embodiment shown in FIG. 2 and is not explained again with regard to the same features. In addition to the features of the embodiment according to FIG. 2, a groove 16 is formed in the contact region 2.5 on the housing 2, in which groove a second seal 17 is arranged. The second seal 17 is formed from glass silk and is arranged closer to the cooking chamber 3 opposite the first seal 15. The second seal 17 thus forms a protection against the penetration of hot air from the cooking chamber 3 into the door gap T or into the contact region 2.5 and to the first seal 15, for example at particularly high cooking chamber temperatures during a pyrolysis cleaning of the cooking appliance 1. the second seal 17 rests against the viewing pane 5.2 in the region of the first microwave trap 13 when the cooking chamber door 5 is closed.FIG. 4 shows a diagram of a frequency band of frequencies which can pass through the door gap T, wherein microwave traps 13, 14 cause a lowering of this frequency band about their resonant frequency. The angular frequencies ω are shown on the X axis, a level A is shown on the Y axis. The nominal frequency of the heating means 8 is also indicated by ω 0. The frequency bands or frequency reductions are shown with a continuous line while exactly maintaining the rated dimension for the door gap T between the cooking chamber door 5 and the housing 2. Broken lines represent deviations of the frequency bands or frequency reductions in the event of a tolerance-dependent deviation of the door gap T from the nominal dimension.In an upper illustration, the frequency band for a single microwave trap is illustrated, in a lower illustration for a double trap as in FIGS. 2 and 3, in which the resonant frequency of the first microwave trap 13 is nominally below the nominal frequency ω 0 that is hot at the nominal dimension of the door gap T, and the resonant frequency of the second microwave trap 14 is nominally above the nominal frequency ω 0. It can be recognized that, due to the illustrated tolerance deviation of the door gap T, the rated frequency ω 0 falls out of the frequency decrease in the case of a single microwave trap and microwaves of the rated frequency ω 0 can consequently pass through the door gap T at a relevant level. In the case of a double trap, on the other hand, the lowering is substantially wider band, so that in the case of the illustrated tolerance deviation of the door gap T, the nominal frequency ω 0 continues to lie in the completely lowered range.List of reference characters1 Cooking appliance 2 housing 2.1 cooking chamber wall of the housing 2.2 cooking chamber wall of the housing 2.3 cooking chamber wall of the housing 2.4 cooking chamber wall of the housing 2.5 contact region of the housing 3 cooking chamber 4 cooking chamber opening 5 cooking chamber door 5.1 frame of the cooking chamber door 5.2 viewing window of the cooking chamber door 5.3 terminating fold of the cooking chamber door 6 circulating air heating means 7.1 heating means for generating radiant heat 7.2 heating means for generating radiant heat 8 heating means for generating microwaves 9 installations 10 items carrier 11 operating element 12 display 13 first microwave trap 13.1 cavity of the first microwave trap 13.2 trap opening of the first microwave trap 13.3 protrusion of the first microwave trap 14 second microwave trap 14.1 cavity of the second microwave trap 14.2 trap opening of the second microwave trap 14.3 protrusion of the microwave trap second microwave trap 15 first seal 16 groove 17 second seal A level T door gap ω angular frequencies ω 0 nominal frequency

Claims

Cooking appliance (1), comprising: a housing (2) with a cooking chamber (3) delimited by housing walls (2.1, 2.2, 2.3, 2.4), wherein the cooking chamber (3) has a cooking chamber opening (4); a cooking chamber door (5) for closing the cooking chamber opening (4), wherein the cooking chamber door (5) has a viewing pane (5.2); and at least one heating means (8) for generating microwaves of a nominal frequency (ω 0) in the cooking chamber (3); wherein the cooking chamber door (5) and the housing (2) together form a contact region (2.5); wherein a surface of the housing (2) in the contact region (2.5) is metallic and defines a contact surface; wherein at least one first seal (15) is formed on the cooking chamber door (5) and a first microwave trap (13) and a second microwave trap (14) are formed in the contact region (2.5) lying one behind the other; and wherein the microwave traps (13, 14) are each formed as a cavity (13.1, 14.1) with a trap opening (13.2, 14.2); wherein the trap opening (13.2) of the first microwave trap (13) is covered by the viewing pane (5.2) and the trap opening (14.2) of the second microwave trap (14) is covered by the first seal (15), characterized in that a second seal (17) is provided and arranged on the housing (2) in the contact region (2.5), wherein the second seal (17) is formed from glass silk.Cooking appliance (1) according to claim 1, wherein the first seal (15) is formed liquid-tight, in particular vapor-tight.Cooking appliance (1) according to one of the preceding claims, wherein the first seal (15) is formed from a silicone material.Cooking appliance (1) according to one of the preceding claims, wherein the viewing pane (5.2) is formed from a glass material.Cooking appliance (1) according to one of the preceding claims, wherein the first microwave trap (13) is designed for a resonant frequency below the rated frequency (ω 0) and the second microwave trap (14) is designed for a resonant frequency above the rated frequency (ω 0).Cooking appliance (1) according to one of the preceding claims, wherein the trap openings (13.2, 14.2) of the door-side first microwave trap (13) and of the door-side second microwave trap (14) are opposite the contact surface of the housing (2).Cooking appliance (1) according to one of the preceding claims, wherein the second seal (17) is arranged in a groove (16) formed on the housing (2) in the contact region (2.5).Cooking appliance (1) according to one of the preceding claims, wherein the second seal (17) is arranged on the housing (2) opposite the viewing pane (5.2).Cooking appliance (1) according to one of the preceding claims, having a spring element for pressing the cooking chamber door (5) against the housing (2) in the contact region (2.5) and in a closed state of the cooking chamber door (5).Cooking appliance (1) according to one of the preceding claims, wherein at least one microwave trap (13, 14) has a projection (13.3, 14.3) projecting from the trap opening (13.2, 14.2) into the cavity (13.1, 14.1), such that the trap opening (13.2, 14.2) is designed as a channel bounded on both sides.Cooking appliance (1) according to the preceding claim, wherein the projection (13.3, 14.3) is slotted.Cooking appliance (1) according to one of the preceding claims, having means for providing a pyrolysis function.Cooking appliance (1) according to one of the preceding claims, designed as an oven.

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