阅读说明：本技术 具有λ-四分之一波陷阱的微波烹饪器具 (Microwave cooking appliance with lambda-quarter wave trap ) 是由 M.库赫勒 K.里戈特 S.施特茨 M.福格特 于 2018-06-08 设计创作，主要内容包括：一种微波烹饪器具(71),其具有门(72),该门在关闭状态下遮盖烹饪室(4)的装料开口(3)并且具有型材状的陷阱结构(77),该陷阱结构与能够导电的门法兰(7)一起形成一个围绕着所述装料开口(3)环绕的λ-四分之一波陷阱,其中所述陷阱结构具有金属的扼流型材(78),该扼流型材具有与所述门法兰对置的敞开的一侧(9),在侧向上在内侧面处于里面的金属舌(10)以及在侧向上在外侧面处于外面的金属舌(73)伸到所述敞开的一侧(9)中,所述处于里面的金属舌和所述处于外面的金属舌与所述扼流型材电连接并且通过微波-进入缝隙(75)彼此隔开,其中所述扼流型材在侧向上在外侧面被朝从所述门法兰(7)的方向突出的平行搭接区域(15)所包围,所述平行搭接区域具有面向所述门法兰的、由能够导电的材料构成的覆盖面(16),该覆盖面与所述门法兰的被其覆盖的区域相同式样地成形并且与所述门法兰隔开。本发明尤其能够应用于微波家用器具、比如独立的微波烹饪器具或者具有微波功能的烤箱和/或蒸煮器具。(A microwave cooking appliance (71) having a door (72) which, in the closed state, covers a filling opening (3) of a cooking chamber (4) and has a profile-like trap structure (77) which, together with an electrically conductive door flange (7), forms a lambda-quarter-wave trap which surrounds the filling opening (3), wherein the trap structure has a metallic choke profile (78) which has an open side (9) opposite the door flange, into which open side (9) laterally the inner metal tongue (10) and laterally the outer metal tongue (73) project, the inner and outer metal tongues being electrically connected to the choke profile and being separated from one another by a microwave entry slot (75), wherein the choke profile is surrounded laterally on the outside by a parallel overlap region (15) projecting in the direction of the door flange (7), said parallel overlap region having a cover surface (16) of electrically conductive material facing the door flange, which cover surface is shaped in the same way as the region of the door flange covered by it and is spaced apart from the door flange. The invention can be applied in particular to microwave household appliances, such as stand-alone microwave cooking appliances or microwave-enabled oven and/or cooking appliances.)

1. Microwave cooking appliance (1; 21; 31; 61; 71) having a door (2; 22; 32; 62; 72) which, in the closed state, covers a filling opening (3) of a cooking chamber (4) and has a profiled trap structure (6; 26; 36; 67; 77) which, in the closed state, forms, together with an electrically conductive door flange (7), a lambda-quarter wave trap which surrounds the filling opening (3), wherein

-the trap structure (6; 26; 36; 67; 77) has a metallic choke profile (8; 24; 34; 66; 78) with an open side (9) opposite the door flange (7),

the metal tongue (10; 33) which is laterally on the inside and the metal tongue (11; 23; 63; 73) which is laterally on the outside extend into the open side (9), are electrically connected to the choke profile (8; 24; 34; 66; 78) and are separated from one another by a microwave entrance gap (12; 75), and

the microwave entrance gap (12; 75) is covered by a microwave-transparent cover (13),

it is characterized in that the preparation method is characterized in that,

the choke profile (8; 24; 34; 66; 78) is laterally surrounded on the outside by a parallel overlap region (15) projecting in the direction of the door flange (7) and

-the parallel overlap region (15) has a cover surface (16) of electrically conductive material facing the door flange (7), which cover surface is shaped in the same way as the region of the door flange (7) covered by it and is spaced apart from the door flange (7).

2. Microwave cooking appliance (21; 31; 61) according to claim 1, characterised in that at least one of the metallic tongues (23; 33; 63) extends inside a cavity (25; 35; 55; 65) formed by the choke profile (24; 34; 66).

3. Microwave cooking appliance (1; 21; 61; 71) according to any one of the preceding claims, characterised in that at least one of the metal tongues (10; 11; 23; 63; 73) is notched with a row of teeth (44; 54; 64; 74) along the profile direction (P), said teeth being separated from each other by a separation gap (45; 55; 68).

4. Microwave cooking appliance (61) according to claim 3, characterised in that the teeth (64) are curved towards the direction of the cavity (65) on at least one side adjoining the separation slit (68).

5. Microwave cooking appliance (51) according to any of the claims 3 or 4, characterized in that the teeth (54) are curved towards the direction of the cavity (55) on the side adjoining the microwave-entry slit (58).

6. Microwave cooking appliance (1; 21; 61) according to any of claims 3 to 5, characterized in that at least some of the separation slits (45; 55; 68) are rectilinear slits and at least some of the teeth (44; 54; 64) have a rectangular basic shape.

7. Microwave cooking appliance (71) according to any of the claims 3 to 6, characterised in that at least some of the teeth (74) have an annular shape.

8. The microwave cooking appliance (71) according to claim 7, wherein at least some of the teeth (74) are interrupted.

9. Microwave cooking appliance (1; 21; 31; 61; 71) according to one of the preceding claims, characterised in that the microwave-transparent cover (13) is a self-supporting cover which is fixed on the trap structure (6; 26; 36; 67; 77) by means of a permanently elastic, temperature-resistant and grease-resistant sealing material (19).

10. Microwave cooking appliance (1; 21; 31; 61; 71) according to claim 9, characterised in that the cover surface (16) of the parallel overlapping area (15) protrudes beyond the microwave-transparent cover portion (13) or is arranged flush with its face.

Technical Field

The invention relates to a microwave cooking appliance having a door which, in the closed state, covers a charging opening of a cooking chamber and has a profiled trap structure (Fallensttruktur), the trap structure forms a lambda-quarter wave trap surrounding the charging opening together with the door flange which can be electrically conductive in the closed state, wherein the trap structure has a metallic choke profile (Droselsprofiler) having an open side opposite the door flange, the metal tongues which are laterally on the inside and the metal tongues which are laterally on the outside extend into the open side, the inner and outer metal tongues are electrically connected to the choke profile and are separated from each other by a microwave entrance gap, wherein the microwave entrance gap is covered by a microwave-transparent cover. The invention can be advantageously applied in particular to microwave household appliances, such as stand-alone microwave cooking appliances or microwave-enabled oven and/or cooking appliances.

Background

For a microwave cooking appliance, microwaves can be applied to a cooking chamber for heating food located in the cooking chamber. The cooking chamber is defined by a cooking chamber wall or "muffle" that is in principle impervious to microwave radiation. The cooking chamber typically has a front loading opening which can be closed by means of a door. The closed door covers the filling opening and its associated edge region, referred to as the door flange. The door and the slit between the door and the door flange should not allow microwaves to propagate outwards and should therefore be sealed against microwave radiation leakage, and rather should be sealed even if there is no electrical contact in the overlap region between the door flange and the door. In order to prevent microwaves from escaping between the door and the door flange when the door is closed, so-called lambda/4 or lambda-quarter wave traps are known, wherein the wavelength of the microwaves is denoted by lambda.

GB 2196520A, US 2004/0079751 a1 and DE 102014224053 a1, for example, describe λ -quarter wave traps. The lambda quarter-wave trap is located behind a cover which protects the lambda quarter-wave trap from dirt or mechanical damage. The cover can be made of a microwave transparent plastic. It is known from DE 10256624B 4, US 2011/0290230 a1, EP 2775794 a1 and DE 3536589C 2 to position λ -quarter wave traps behind a viewing window (Sichtfenster) facing the cooking chamber.

Disclosure of Invention

The object of the present invention is to overcome at least partially the disadvantages of the prior art and in particular to provide a lambda-quarter-gate trap or gate choke for a microwave appliance, the choking or shielding effect of which is particularly insensitive to changes, in particular to an enlargement, of the gate gap. Furthermore, a particularly high insensitivity to obliquely incident microwave radiation should also be possible. In addition, a particularly compact dimensioning of the λ -quarter wave trap should be possible.

This object is achieved according to the features of the independent claims. Preferred embodiments can be gathered, in particular, from the dependent claims.

This object is achieved by a microwave cooking appliance which, in the closed state, covers a filling opening of a cooking chamber which can be filled with microwaves. The door of the microwave cooking appliance to be described below is in the closed state as long as the open state is not explicitly indicated. The door has a profile-like trap structure. When the door is in the closed state, the trap structure forms, together with the door flange which can be electrically conductive, a lambda-quarter wave trap for microwaves which surrounds the charging opening. The trap structure has a metal profile (hereinafter referred to without restricting generality as a "choke profile") with an open side opposite the door flange. The metal tongue projects laterally into the open side on the inner side (in the following referred to without limiting the generality as "metal tongue in the inside"). The arrangement of the inner side in the lateral direction can also be referred to or regarded as an arrangement of the inner side in the radial direction in a front view or an arrangement of the cooking chamber side. Furthermore, a metal tongue (hereinafter referred to without limiting the generality as "metal tongue outside") projects laterally on the outer side into the open side. The arrangement of the outer side on the side can also be referred to or regarded as an arrangement of the outer side in the radial direction in front view or an arrangement facing away from the cooking chamber. The metal tongues are electrically connected to the choke profile and are spaced apart from one another in the open side. In other words, they are separated from one another by a gap (referred to below without restricting generality as "microwave-entry gap"). The microwave entrance gap is covered in particular by a microwave-transparent cover. The choke profile is surrounded laterally on the outside by a door region (referred to below without limiting the generality as "parallel overlap region") which projects from the choke profile in the direction of the door flange. The parallel overlap region has a surface of electrically conductive material facing the door flange (hereinafter referred to without restricting the generality as "cover surface") which is shaped in the same manner as the region of the door flange covered by it and is spaced apart from the door flange.

Such a microwave cooking appliance offers the advantage that the trap structure forms a lambda-quarter wave trap whose choking or shielding effect is particularly insensitive to changes, in particular to enlargement, of the door slot. This in turn offers greater stability, in particular with respect to thermal movements and with respect to manufacturing tolerances, which involves significant advantages for the production process. The trap structure also makes it possible to achieve a particularly high insensitivity to obliquely incident microwave radiation. The choke profile ensures better low leakage radiation as the deviation of the desired effective frequency is smaller when the angle of incidence of the microwave radiation emitted from the cooking chamber varies. In addition, a particularly compact dimensioning of the λ quarter-wave trap can be achieved, which is smaller than the installation space previously occupied inside the door. Thus, it is possible to enlarge the height and width of the cooking chamber-and thus the total volume available for processing food-without losing the microwave shielding property. The optional microwave-transparent cover section prevents soiling or damage to the profile, in particular also to the cavity of the choke profile.

The microwave cooking appliance can be a household appliance, in particular a kitchen appliance. The microwave cooking appliance can be a stand-alone microwave cooking appliance, but also other cooking appliances, for example an oven and/or a cooking appliance with microwave functionality.

The door is microwave-tight with respect to transmission (durchtrahlung) and can also be referred to as a microwave door.

The door has a profile-like trap structure, which can include, inter alia, the following aspects: the trap structures have at least substantially the same cross-sectional shape along their longitudinal extension ("profile direction"). The profile direction extends in front view around the charging opening.

The metal tongue is arranged in particular parallel to the open side.

In one development, the choke profile is a C-shaped choke profile in cross section. This enables particularly easy production with effective choking or shielding.

The metal tongue is electrically connected to the choke profile, which can include the following aspects, namely: the metal tongues are produced separately and then connected to the choke profile, for example by welding. An alternative development is that the metal tongue is an integrated region of the choke profile, in particular already produced integrally with the choke profile. The metal tongue, the throttle profile and/or the overlap region can be made of aluminum, copper and/or steel, for example. In general, every other suitable well-conducting material can also be used instead of metal.

In one refinement, the microwave entrance gap has at least substantially the same width.

In a further development, the metal tongue is recessed in a cross-sectional view in a direction towards the interior of the door relative to the covering surface. In particular, the parallel overlap region can be arranged directly, in particular in a stepped manner, on the outer metal tongue or the choke profile.

The parallel overlap region and the choke profile can already be produced in one piece or alternatively can already be produced separately and connected to one another in the future.

The cover surface is shaped in the same manner as the region of the door flange covered by it, which results in an at least substantially identical spacing between the two surfaces and thus in a particularly uniform shielding effect. The cover surface and the region of the door flange covered thereby can be designed in particular as a flat or planar structure and arranged parallel to one another, which enables a particularly stable throttling action.

In one embodiment, at least one of the metal tongues extends into the cavity formed by the choke profile. The following advantages are thus achieved, namely: the travel of the microwave radiation (Laufweg) is extended and the volume of the cavity can therefore be reduced. Thus, the height and/or width of the cooking chamber-and thus the total volume available for processing food-can be enlarged without losing the microwave shielding properties.

At least one of the metal tongues extends towards the inside of the cavity, which can include, inter alia, the following aspects: these metal tongues are bent into the cavity or have one or more bends in cross section. At least one of the metal tongues thus extends behind the open side of the choke profile.

Usually, only the outer metal tongues, only the inner metal tongues or both metal tongues can extend into the cavity or be bent accordingly.

It is also conceivable that at least one of the metal tongues is provided with a row of teeth or is notched with a row of teeth (zahnen) in the profile direction, wherein the teeth are spaced apart from one another in the profile direction, in particular by interruptions such as slits (in the following referred to as "separating slits" without restricting the generality).

The following facts are utilized here: that is, microwave radiation present in the cooking chamber of the microwave cooking appliance impinges on the λ -quarter wave trap at different angles of incidence. An accurate prediction of the angle of incidence that occurs is very cumbersome, since the microwave radiation, after it has been generated, for example in a magnetron, is reflected multiple times at the wall of the cooking appliance before it strikes the lambda-quarter wave trap. At oblique incidence of the microwave, the effective active trap length of the ungated trap is extended by a factor of 1/cos (θ), where θ describes the angle between the face normal of the gate plane and the propagation or propagation direction of the incident microwave. Correspondingly, the effective frequency also varies with the effective trap length, so that a lambda-quarter wave trap without teeth no longer works optimally for any angle of incidence. This effect is particularly pronounced for microwave cooking appliances with large muffle or cooking chamber dimensions, since different angles of incidence may occur in a very broad spectrum. If the lambda-quarter wave trap is not divided or notched, surface currents can flow unimpeded along the wave propagation direction. However, the interruptions between the teeth prevent this and deflect the current in the direction of the interruption, so that the associated microwaves have a significantly smaller angle of incidence. This angle of incidence can be so small that the situation corresponds almost to microwaves incident in the normal direction. This embodiment therefore makes it possible to achieve a particularly high level of insensitivity to obliquely incident microwave radiation.

Usually, only the outer metal tongues, only the inner metal tongues or both metal tongues can be notched.

In one refinement, at least one of the metal tongues is slotted by means of a row of laterally oriented separating slots.

An arrangement of metal combs, the teeth of which have a width of about 4mm and the slits of which have a width of about 2mm, has proved particularly effective.

In a further embodiment, the teeth are curved in the direction of the cavity on at least one side adjacent to the separating gap. This design again enables a significant improvement in the effect of the choke profile or the lambda-quarter-wave trap with respect to obliquely incident microwaves.

In a further embodiment, the teeth are curved in the direction of the cavity on the side adjacent to the microwave entrance slot. This design also enables a significant improvement of the effect of the choke profile or the lambda-quarter wave trap with respect to obliquely incident microwaves.

In order to be able to design the teeth or the teeth to be bent particularly easily, it is advantageous if the interruptions or separating gaps to be cut (einbringen) between the teeth are formed by: the interruptions are not completely cut and removed (freiarbeiten), but the material to be removed has been bent along the long and/or short sides in the direction of the cavity and remains as an effective trap element.

In general, the length and/or spacing of the interruptions or the like can be varied alternately.

Furthermore, it is provided that at least some of the separating slots, in particular all separating slots, are rectilinear slots and that at least some of the teeth, in particular all of the teeth, of at least one of the metal tongues have a rectangular basic shape. This embodiment can be produced particularly easily.

It is also provided that at least some of the teeth have an annular shape. This can again improve the effect of the choke profile or the lambda-quarter wave trap with respect to obliquely incident microwaves. The annular shape can be a shape that is continuously curved, such as a circular shape, an oval shape, an elliptical shape, etc., or a polygonal shape, such as a rectangular shape, etc. The design of the teeth with an at least almost oval basic shape ("oval teeth") is particularly advantageous.

The annular tooth can close on itself.

Furthermore, it is provided that at least some of the ring teeth, in particular all of the ring teeth, are interrupted. The wave propagation along the ring shape is prevented by the associated gap, which further improves the choking effect. The voids can be symmetrically arranged in the center. Alternatively, however, the recesses can also be in different segments (segments) or angular directions of the ring gear. These positions can also alternate, if desired.

The annular tooth can be connected to the choke profile and/or to the overlap region by means of a separate web for each tooth. In a further development, the ring teeth can be placed on a common consecutive web. However, they can also be connected to the throttle profile and/or to the overlap region of the door without tabs or by direct connection.

In addition, it is provided that the microwave-transparent cover is a self-supporting cover. Such a cover is particularly stable and furthermore prevents the formation of corrugations (Welligkeit) of the cover on the contact region with the choke profile.

It is also provided that the microwave-transparent cover is fastened to the trap structure by means of a permanently elastic, temperature-resistant and grease-resistant sealing material. The sealing material particularly reliably prevents vapor or dirt from penetrating into the cavity of the choke profile through the slot between the cover and the choke profile. In one development, the sealing material is or has a temperature-resistant silicone resin.

In a further development, the sealing material is arranged in the region formed by the projecting parallel overlap region, the outer metal tongue and the edge of the microwave-transparent cover.

In one refinement, the microwave-transparent cover has a disk made of glass, in particular hardened glass. The glass is particularly resistant to thermal and chemical influences and furthermore-particularly in the form of hardened glass-to mechanical loads.

In one embodiment, the cover surface of the parallel overlap region projects beyond the microwave-transparent cover. The microwave-transparent cover can therefore be protected particularly reliably against direct mechanical contact with the door flange. A particularly reliable and tolerable shielding effect is thus also produced. Alternatively, the cover surface of the parallel overlap region and the microwave-transparent cover surface are arranged flush with one another on the flange side.

Drawings

The above features, characteristics and advantages of the present invention and the manner of attaining them will become more apparent and the invention will be better understood by reference to the following description of an embodiment taken in conjunction with the accompanying drawings, wherein like reference numerals are used to designate like elements in the figures.

Fig. 1 to 3 show, in a sectional view, a cut-out from a side view of a corresponding microwave cooking appliance having a corresponding different design of the trap structure according to a first to a third exemplary embodiment;

fig. 4 to 5 show, in oblique views from below, a cut-out of a corresponding microwave cooking appliance, in particular according to the first or second embodiment, with a comb-like trap structure;

fig. 6 to 7 show, in oblique views from below, a cut-out of a corresponding microwave cooking appliance according to a fourth or fifth embodiment, with a corresponding different design of the trap structure; and is

Fig. 8 to 10 show graphs which, in comparison with the prior art DE 10256624B 4, show the shielding effect of a microwave cooking appliance with a lambda-quarter wave trap according to the invention.

Detailed Description

Fig. 1 shows a sectional view in a side view of a microwave cooking appliance 1 according to a first exemplary embodiment, with a cut-out of a door 2, which covers a filling opening 3 of a cooking chamber 4 in the illustrated closed state. The cooking chamber 4 is defined by a cooking chamber wall or muffle 5.

The door has a profile-shaped trap structure 6, which is shown here on the upper edge of the door 2. The trap structure 6 forms a lambda-quarter wave trap around the charging opening 3 together with a door flange 7 which can be electrically conductive in the closed state of the door 2.

The trap structure 6 has a metallic, C-shaped choke profile 8, which has an open side 9 opposite the door flange 7. A metal tongue 10, which is laterally on the inside and a metal tongue 11, which is laterally on the outside, project into the open side 9. The metal tongues 10 and 11 are formed integrally with the choke profile 8 and are separated from one another by a microwave entrance gap 12. In a first variant, the metal tongues 10 and/or 11 can be designed continuously or without interruption or in the form of strips in the profile direction extending perpendicular to the plane of the drawing. In a second variant, the metal tongues 10 and/or 11 can be comb-shaped or toothed along the profile direction.

The microwave entrance gap 12 is covered by a microwave-transparent cover, which is formed in the form of a glass disk 13, which is shown in an exemplary manner and is made of hardened glass. This prevents steam and dirt from penetrating into the cavity 14 formed by the throttle profile 8.

The choke profile 8 is laterally surrounded on the outside by a parallel overlap region 15 which projects in the direction of the door flange 7 and which is in this case, in one variant, integrally formed with the choke profile 8 (ausarbiten). The parallel overlap region 15 has a cover surface 16 of electrically conductive material facing the door flange 7, which cover surface is shaped in the same manner as the region of the door flange covered by it (i.e., is vertically flat here) and is arranged at a distance from the door flange 7. The door flange 7 and the cover surface 16 thus form a door slot 17.

The glass disk 13 is flush with the cover surface 16. In its region opposite the filling opening 3, the glass disk 13 has a microwave-opaque viewing grid (Sichtgitter) 18, which can be shaped, for example, in the form of a printed metal grid. The glass disk 13 is fixed to the trap structure 6 by means of a permanently elastic, temperature-resistant and grease-resistant adhesive (adhesive) or sealing material 19. For this purpose, sealing material 19 is introduced here into the lateral gap between the edge of the glass disk 13 and the parallel overlap region 15.

Fig. 2 shows a sectional view in a side view of a microwave cooking appliance 21 according to a second exemplary embodiment, with a cut-out of the door 22. The door 22 is constructed similarly to the door 2, but now the outer metal tongue 23 of the trap structure 26 is partially bent in cross section into the cavity 25 formed by the choke profile 24. The cross section of the metal tongue 23 is thus bent or curved. As a result, the choke profile 24 and thus the cavity 25 can be made smaller with the same shielding effect, wherein: having a smaller height than the cavity 14.

In a first variant, the metal tongues 10 and/or 23 can be designed continuously or without interruption along a profile direction extending perpendicular to the plane of the drawing. In a second variant, the metal tongues 10 and/or 23 can be comb-shaped or toothed along the profile direction.

Fig. 3 shows a cut-out with a door 32 of a microwave cooking appliance 31 according to a third embodiment as a sectional view in a side view. The door 32 is constructed similarly to the door 2, but with the metal tongue 33 of the trap structure 36 now lying inside being partially bent in cross section into the cavity 35 formed by the choke profile 34.

In another variant (not shown), both metal tongues can be bent into the cavity.

Fig. 4 shows a cut-out of a microwave cooking appliance 1 according to a second variant of the microwave cooking appliance 1 in a view from obliquely below, with the glass disk 13 shown partially hidden. The outer metal tongues 11 of the trap structure 6 are here toothed in the profile direction P with a row of teeth 44 or are provided with a row of teeth 44, which are separated from one another by a straight separation gap 45. The teeth 44 each have a rectangular shape with a width of 4mm along the profile direction P, while the separation gap 45 has a width of 2 mm.

Fig. 5 shows a view similar to fig. 4 of a microwave cooking appliance 21 according to a second variant of the microwave cooking appliance 21. For this purpose, the door 22 has an outer metal tongue 23 with teeth 54, which teeth 54 are separated from one another by a separating gap 55. The teeth 54 are bent locally in the direction of the cavity 25 of the choke profile 24 and more precisely around a bending line B running in the profile direction P. This can also be expressed as follows: the teeth 54 are curved in the direction of the cavity 25 at or along the side (upper) adjoining the microwave-entry slot 12.

Fig. 6 shows a microwave cooking appliance 61 according to a fourth embodiment in a view similar to fig. 4. The door 62 is constructed similarly to the door 43, but the outer metal tongue 63 of the trap structure 67 now has teeth 64 which are bent locally in the direction of the cavity 65 of the choke profile 66 and, more precisely, are each bent around a bending line C running perpendicularly to the profile direction P. This can also be expressed as follows: the teeth 64 are curved in the direction of the cavity 65 on at least one side adjoining the separating gap 68.

Fig. 7 shows a microwave cooking appliance 71 according to a fifth embodiment in a view similar to fig. 4. The door 72 is constructed similarly to the door 42, but with the now outer metal tongue 73 having teeth 74 which have an oval annular shape. The teeth 74 each have a respective interruption 76 at their end facing the microwave inlet slot 75.

In other variants, however, the interruption can be present at other positions of the tooth, if necessary at different positions in the profile direction. In one variant, the annular tooth can also be uninterrupted.

In addition to the connection of the oval teeth 74 to the remaining trap structures 77 by corresponding webs, which is shown in fig. 7, the teeth 74 can also be connected, for example, in the following manner (for example, by a common continuous web or also without webs in direct connection with the trap structures 77, in particular with the choke profiles 78 or with the parallel overlap region 15).

The trap structure 77 with the oval teeth 74, which is generally a ring-shaped tooth, also compensates the influence of obliquely incident electromagnetic waves significantly more effectively than the non-ring-shaped trap structures 6, 26, 36, 46, 56 and 67.

Fig. 8 shows a diagram of the attenuation in dB on the y-axis for the frequency in GHz on the x-axis of a microwave cooking appliance, with attenuation curves F1 and F2 for the characterization of the prior art DE 10256624B 4 and with attenuation curves F3 and F4 for the characterization of the λ -quarter wave trap according to the invention, such as according to the embodiment of fig. 4.

The attenuation curves F1 and F3 show the case of an "ideal" door slot of 1mm, i.e. a door slot for which the effective frequency of the microwave trap or trap structure coincides with the operating frequency of the microwave cooking appliance. However, in practical applications, the door slots may have different dimensions, wherein widening of the door slots represents a critical situation. In this case, the reasons are manifold and may be due to manufacturing tolerances or thermal movements of the appliance during the heating process, for example. In actual use, such variations in the gate seam and different angles of incidence θ of the microwave radiation contribute first to undesired variations in the shielding properties. The lambda quarter-wave trap is particularly reliably shielded from microwave leakage radiation if, due to its structure, it is particularly insensitive to variations, in particular to an enlargement of the gate gap. In particular, an improvement in the stability with respect to changes is shown for small changes in the attenuation characteristic, in particular for small deviations in the frequency position of maximum attenuation. For this purpose, the damping curves F2 and F4 show a door slot that is 1mm wide (i.e. a total width of 2 mm).

For an ideal slit of 1mm as can be seen from the attenuation curves F1 and F3, the attenuation characteristics are practically the same. Especially the location of maximum attenuation is at the same microwave frequency of about 2.455 GHz.

Whereas the damping curves F2 and F4 show a clear difference when the door slot is additionally opened 1mm wide. The attenuation curve F4 of the lambda-quarter wave trap according to the invention advantageously has a significantly smaller shift of the frequency position of maximum attenuation compared to the attenuation curve F2 according to the prior art.

Fig. 9 is a graph of the frequency shift of the position of the maximum attenuation in GHz on the y-axis for the prior art DE 10256624B 4 (curve G1) and for the λ -quarter wave trap of fig. 8 (curve G2) with respect to the enlargement of the gate gap in mm on the x-axis.

In the prior art, the ideal effective frequency is much more shifted than the λ -quarter wave trap according to the invention when the gate gap is enlarged. The fact that the lambda-quarter wave trap according to the invention reacts much less to changes in the gate gap means that the gate can be opened even more before the leakage radiation reaches an impermissibly high value. In particular, greater stability with respect to thermal movements and manufacturing tolerances therefore results, which brings about significant advantages in particular for the production process.

Fig. 10 shows a diagram of the attenuation in dB on the y-axis with respect to the frequency in GHz on the x-axis, with attenuation curves H1 and H2 for the characterization of the prior art DE 10256624B 4 and with attenuation curves H3 and H4 for the characterization of the λ -quarter wave trap with the trap structure 77 according to fig. 7. The attenuation curves H1 and H3 describe the attenuation produced at small angles of incidence θ = 7 °, while the attenuation curves H2 and H4 describe the attenuation produced at large angles of incidence θ = 40 °. The smaller the shift in the desired effective frequency when the angle of incidence θ of the microwave radiation from the cooking chamber 4 varies, the lower the leakage radiation can be better ensured by the lambda-quarter wave trap or choke profile.

The trap structure 77 of fig. 7, which has elliptically or generally annularly shaped teeth, compensates the influence of obliquely incident electromagnetic microwaves significantly more effectively than in the prior art. This embodiment has a particularly reliable attenuation function as a microwave trap due to the lower sensitivity with respect to changes in the angle of incidence θ.

Of course, the invention is not limited to the embodiments shown.

Thus, the features of the different embodiments can be combined arbitrarily. For example, oval teeth can also be bent into the cavity and/or different types of teeth can be present on the metal tongue.

"a", "an", etc. can mean in general a single number or a plurality of numbers, especially in the sense of "at least one" or "one or more", etc., as long as this is not explicitly excluded, for example by the expression "exactly one".

The numerical designation can also encompass not only the numbers just specified but also common tolerance ranges, as long as this is not explicitly excluded.

List of reference numerals

1 microwave cooking appliance

2 door

3 charging opening

4 cooking chamber

5 muffle furnace

6 trap structure

7 door flange

8 choke profile

9 open side of choke profile

10 metal tongue inside

11 metal tongue at outside

12 microwave entrance gap

13 glass disk

14 cavity

15 parallel overlap region

16 cover surface

17 door gap

18 view grid

19 sealing Material (adhesive)

21 microwave cooking utensil

22 door

23 metal tongue on the outside

24 choke profile

25 cavity

26 trap structure

31 microwave cooking appliance

32 door

33 metal tongue in

34 choke profile

35 cavity

36 trap structure

44 tooth

45 separating gap

54 teeth

55 separating slit

61 microwave cooking utensil

62 door

63 metal tongue at outside

64 teeth

65 cavity

66 choke profile

67 trap structure

68 separation slit

71 microwave cooking appliance

72 door

73 metal tongue outside

74 teeth

75 microwave-entrance slit

76 interruption portion

77 trap structure

78 choke profile

B bending line

C bending line

F1-F4 decay Curve

Curves of positions of highest attenuation of G1-G2

Attenuation curves H1-H4

And (3) a P-shaped material direction.