EP2128528A2 - Oven muffler - Google Patents

Abstract

The muffle (10) has a retaining chamber limited by a bottom side (11), top side (12) and lateral and/or rear-side wall elements (13-15), where one of the wall elements is permeable for infrared (IR) radiations. A reflection element reflecting the radiations is arranged in the area of an external surface of the wall element, where the surface is turned away from the chamber. The wall element is made of glass or glass ceramic, and the reflection element is applied as a tin oxide coating, azo coating and indium tin oxide coating, and absorption elements are formed of imprinted ceramic colors.

Description

The invention relates to a furnace muffle having a receiving space which is bounded at least in regions by wall elements, wherein at least one of the wall elements is transparent to IR radiation or has an area permeable to IR radiation.

Electrically heated ovens for stoves or for installation in a kitchenette are well known. The oven consists essentially of an enamelled oven muffle, which is heated above and below with Rohreizkörpern. On the front, the oven muffle is closed with a framed glass door. Usually, the upper heating is arranged in the interior of the baking oven muffle and is supported in high-quality ovens by a second radiator, which allows a grill function of the oven. The lower radiator is applied to the outside of the muffle floor. In addition to these standard heaters for top / bottom heat and grill operation is often still in the rear wall, a circulating air blower used, which may also have a separate heating ring to not only to circulate air, but also to generate hot air itself. Due to the structural design and the materials used for the radiator and the oven muffle, the entire heating system is very sluggish. The tubular heater takes a very long time until it is at temperature and a uniform temperature distribution in the oven is ensured. In particular, this applies to the bottom heat, which must first heat the muffle floor so that it can then pass the heat to the muffle room and the food. Until a stationary temperature is reached, the entire muffle space including walls is heated, since the enamelled walls very strongly absorb the heat energy generated by the tubular heater. In addition to the long heat-up time, this adds another problem, namely that dirt, grease splashes and the like on the walls of the oven muffle burns very strongly. To circumvent these shortcomings, the use of short-wave IR radiation has already been proposed. A method for using this rapid heat radiation for baking or roasting operations is, for example, in WO 00/40912 A2 and the EP 0 416 030 B1 described. The use of short-wave IR radiation significantly increases the penetration depth into the food to be cooked and shortens the slow heat transfer due to heat conduction inside the food. Disadvantage of this technology is the use of point and line heat sources, which are reflected directly on the food, if no further optical precautions are taken.

A number of inventions attempt to overcome these disadvantages, for example the DE 102 03 607 A1 , Here, by an additional, outside the translucent cover attached structured and reflective layer, the linear light source is reflected in the oven. In addition, the linear light source still moves transversely to its longitudinal extent. This procedure is very complicated by the necessary musculoskeletal system. A disadvantage of this oven described is further that the reflective wall is housed as an additional wall behind the translucent wall in the cooling channel. By this construction, a part of the energy is transported away through the cooling channel.

In the DE 102 03 609 A1 a Lichtwellenofen is described which uses a uniform illumination of the furnace chamber by movable, linear light sources with a pivoting reflector. This structure is mechanically very complex.

Furthermore, the methods described above have the disadvantage that the browning process, which requires the long-wave component of the radiation, is not accelerated here. This disadvantage is in the DE 102 03 610 A1 described and solved by the installation of further long-wave radiators with a different color temperature. This method is also complicated and expensive due to the additional installation of further radiators.

It is also known to make oven walls made of glass or glass ceramic. The use of glass ceramic in ovens is already in the CA 21834987 described. Here, the oven floor is proposed for better cleanability of glass ceramic. In the DE 33 02 794 A1 describes an oven muffle made of glass or glass ceramic, which is heated with printed heat conductors. In this case, however, only long-wave slow radiations can be generated. In the DE 35 27 957 C2 an oven muffle glass ceramic is described, which is detachably joined together and is heated by mounted externally radiant heater. The discs are inserted into a support or holding frame, by the resulting edges and joints, especially in the lower corners of the oven muffle this is very difficult to clean. The bill is in the DE 35 27 958 C2 proposed an enameled sheet steel muffle, in which window openings are provided in the side walls, are inserted into the glass or glass ceramic panes. In this case, there is the same problem with the joints and joints which are difficult to clean and, in addition, a large part of the muffle space is still made of enamelled steel sheet, whereby the effect of the fast short-wave IR radiation is lost again.

It is an object of the invention to provide a baking oven muffle of the type mentioned, in which good cooking results are achieved with good cleanability of the receiving space facing inner surfaces of the wall elements.

This object is achieved in that an IR radiation-reflecting reflection element is arranged in the region of the outer surface of the wall element facing away from the receiving space.

The oven muffle according to the invention can be heated by the known light wave technology, wherein the disadvantages described above, in particular the uneven illumination and the lack of long-wave radiation are solved. The arrangement of the reflection layer on the outer surfaces of the wall elements makes it possible to perform the inner surfaces scratch resistant, so that the oven muffle can be easily cleaned even in heavy soiling. In addition, the arrangement of the reflection layer allows a uniform illumination of the space surrounded by the furnace muffle receiving space. This can be achieved good cooking results. The reflection of the short-wave IR radiation is preferably carried out in the region of the outer surfaces and not by a reflective layer on the inner side of the muffle. A coating on the inside of the muffle would be sensitive to scratching and one would have the problem of missing boring heat radiation, which is necessary for browning the cooking surface. When using the muffle outside as a reflector and scattering surface, the inside remains smooth and easy to clean and in addition, the wall element can be adjusted via targeted adjustment of the transmission or the absorption behavior so that a desired self-heating generates long-wave IR radiation, by far the largest part of the IR radiation but be scattered and reflected by appropriate measures.

According to a preferred embodiment variant of the invention, it can be provided that the wall element consists of glass or glass ceramic. These materials have the advantage that they provide sufficient scratch resistance on the inner surface facing the interior of the furnace muffle.

The transmission or absorption properties of the glass ceramic walls can be achieved, for example, by adjusting the transmission properties of the glass ceramic itself. It is also conceivable that absorption elements are introduced into the wall element and / or applied to this, which absorb IR radiation. For example, decoratively baked in the surface of the wall elements decor colors can be used. These can control the absorption behavior of the wall element in a wide range. As a result, the missing long-wave component of the radiation is generated by targeted self-heating of the wall elements in a skilful manner.

By the absorption elements, both the short-wave and the long-wave IR radiation can be selectively influenced.

According to a variant of the invention, it can be provided, in particular, that the absorption elements are arranged such that zones with different absorption behavior are formed. In this way, the absorption behavior of the oven muffle can be adjusted specifically. According to the desired distribution or absorption of the wall elements, the decoration may be distributed homogeneously on individual or all the conversion elements. The decoration may be provided over the entire surface or only on partial areas of the wall elements. It can also be present in partial grids with different pitch on one or more wall elements. In this way, an almost arbitrary absorption structure can be generated on the wall elements. In addition, absorption can also be influenced by the absorption behavior of the decorative color used. For example, the absorption behavior of the absorption elements can be controlled between 10% to 90% using different decorative colors.

The application of the decors can take place in such a way that the absorption elements are coated on the wall element as décor, for example as screen prints or electrophotographic printing. Screen printing methods allow an accurate reproducible printing of large batch sizes. Electrophotographic processes enable economical printing of small and medium sizes.

If it is provided that the absorption elements are formed by imprinted ceramic colors, then the absorption elements are sufficiently resistant, in particular scratch-resistant, so that they can be applied to the inside of the wall elements without their function being impaired during the cleaning of the oven muffle.

A particularly preferred variant of the invention is characterized in that one or more structural elements for generating scattered radiation are arranged in the region of the outer surface of the wall element. The structural elements ensure a uniform distribution and thus illumination of the entire interior of the oven muffle. However, it is also conceivable that, depending on the arrangement, zones with different degrees of illumination are formed specifically via the arrangement and / or design of the structural elements in the interior. In this way, with the structural elements, the illumination of the interior can be controlled with short-wave IR radiation.

The structural elements can be produced with little manufacturing effort by the fact that the structural elements are integrally formed on the wall element.

A furnace muffle according to the invention is preferably equipped such that a heating body is arranged outside the receiving space in the region of the outer surface of at least one of the wall elements. This further improves the cleanability of the interior. Particularly suitable for the desired functionality of the oven muffle heating elements can be used, which generate IR radiation with a wavelength less than 1.4 microns. This short-wave radiation penetrates deep into the food and effectively shortens the cooking time. When using glass ceramic as the material for the / the wall elements, a high permeability for this IR radiation is possible.

The invention will be explained in more detail below with reference to exemplary embodiments illustrated in the drawings.

Fig. 1

in schematischer Darstellung eine Ofenmuffel in Frontansicht,

Fig. 2 bis 7

verschiedene Varianten der Gestaltung eines Wandelementes gemäß dem in Fig. 1 mit "X" markierten Detail und

Fig. 8

eine Grafik, bei der die Transmission unterschiedlicher Glaskeramiken der Strahlungsemission verschiedener Heizelemente gegenübergestellt ist.

Show it:

Fig. 1

in a schematic representation of a furnace muffle in front view,

Fig. 2 to 7

Various variants of the design of a wall element according to the in Fig. 1 with "X" marked detail and

Fig. 8

a graph in which the transmission of different glass ceramics is compared with the radiation emission of different heating elements.

The Fig. 1 shows a furnace muffle, which encloses an interior, which serves as a cooking chamber. In this case, the interior of five wall elements 11-15, namely a bottom side (11), an upper side (12), two vertical-side and a rear wall element (15) is limited. Outside the interior, a heating element 20 is disposed on the outer sides of the bottom-side and the top-side wall element 11 and 12, respectively. The heating elements 20 are preferably formed by halogen heaters. It is also conceivable to use halogen lamps and normal resistance wire to generate different wavelengths. Furthermore, the cost-available band heaters can be used, as used in glass ceramic cooktops. In addition, heating elements 20 can be provided behind the lateral and / or rear wall element 13, 14, 15 for better energy distribution in the interior of the oven muffle. This embodiment then has the advantage that in the stacked arrangement several baking trays a good illumination of the interior and radiation exposure to the entire food can be achieved.

The Fig. 2 to 7 show exemplary embodiments of the wall element 14 possible designs of the wall elements 11 to 15. Here, all wall elements 11 to 15 preferably the same structure. However, it is also conceivable that the wall elements 11 to 15 each have different adapted designs.

The wall elements 11 to 15 have as a carrier material a disc S, consisting of a glass or preferably of a glass ceramic. In this case, the disc S forms an inner surface 16 facing the interior of the oven muffle and an outer surface 17 facing away from the inner surface 16. The inner surface 16 delimits the entire inner side (side surface) of the inner space.

As the Fig. 2 1, a coating, for example a noble metal coating, is applied to the outer surface 17 of the pane S as the reflection element 30. The coating is suitable for at least partially reflecting IR radiation into the interior space. This coating can for example be sprayed or applied by sputtering.

At the in Fig. 3 In the embodiment shown, instead of the fixedly applied coating, a reflection film (preferably aluminum sequence) attached loosely on the outside is used as the reflection element 30, which can optionally be applied much less expensively than a fixed rear reflection layer. The reflective foil may be adhered to the outer surface 17 or loosely applied, as shown in FIGS Fig. 3 shows.

The Fig. 4 also shows a loosely applied reflection foil (preferably aluminum foil), which is structured to scatter the IR radiation. The structure may vary depending on the desired effect. In the present case, the reflection foil is provided with structural elements 18 which form a corrugated structure, with uniform wave shapes running in the direction of the width of the wall element 14. The reflection element 30 can also be carried by an insulating element 40, for example of a glass or mineral wool. For this purpose, the reflection element 30 can be laminated onto the insulating element 40 in the form of a sheet-like blank. It is also conceivable that the reflection element 30 is coated on the surface of the Dämmelements 40.

The Fig. 5 also shows a glass-ceramic with a back-applied solid reflective layer, as in Fig. 2 However, here the back is structured, with one-piece molded structural elements 18 in the form of stray knobs, to thereby also produce a uniform distribution of the IR radiation in the interior, the scattering knobs can be arranged distributed in a dot pitch in the same pitch grid. It is also conceivable that the Streunoppen form rib-like webs.

In the wall element 14 according to Fig. 6 On the outside again a loosely laminated reflective foil (preferably aluminum foil) is used. The scattering is again achieved by the structured outside of the glass ceramic (as in Fig. 5 ) and the reflection through the laminated reflective foil. By way of example for all embodiments, an interior decoration of the oven muffle is indicated in this cross section, which is formed by individual printed absorption elements 19, through which the absorption of the oven muffle is specifically adjustable. According to the desired distribution of the absorption elements 19 or the absorption of the wall element 14, the decoration can be applied homogeneously over the entire interior or even only selectively in certain areas over the entire surface or in partial rasters. The decor colors used have an absorption behavior that can be controlled between 10% - 90%.

The Fig. 7 shows the use of a structured on the outside glass-ceramic wall (similar to Fig. 5 ) with a reflection film (preferably aluminum foil) located largely smoothly around the outer surface 17, which ensures the reflection of the IR radiation. The scattering is ensured in this case again with molded structural elements 18 through the structured outer side of the disc S. The absorption behavior itself can be varied by the glass ceramic used in the range of 50% - 90%. This decisively influences the self-heating of the oven muffle and the cooking and baking dynamics of the oven. As a further variation variable, in order to influence the heating rate and the pre-and post-run of the wall temperatures of the oven muffle, the thickness of the glass ceramic of 2 - 6 mm, preferably 4 mm, can be influenced. In addition to the scattering function by the structuring of the outer surface 17 of the disc S through Structural elements 18 such as knobs, or a structured reflection film, etc., the glass-ceramic itself can also form their own stray fields by setting appropriate cristalite sizes.

The Fig. 8 shows by way of example the transmission curve of three typical glass-ceramics GC in the range of 500-5000 nm and additionally the radiation emission of a radiant heater with wire helix or band H1, a today usual tubular heater in grill operation (1100 K) (H2) and a tubular heater in operation at normal top heat ( 600K). The short-wave IR-A radiation up to a wavelength of 1.4 μm is responsible for through-cooking with a high penetration depth into the cooking, baking or grilling food. The penetration depth of this radiation in water is up to 7 cm. In this area, the preferably used halogen lamps work predominantly. The subsequent IR-B radiation is in the range of 1.4-3 μm. Here, the radiation heater described with resistance wire or resistance band has its radiation center of gravity. This is followed by the IR-C radiation area. This medium infrared radiation is responsible for the browning of the roast or grilled food and is mainly produced by the standard H3 tubular heaters used today.

The oven according to the invention preferably uses the short-wave IR-A radiation with the advantage that the heat arrives immediately on or in the food to be cooked without preheating the oven. Due to the higher penetration depth of the radiation, a significantly higher energy absorption per unit time is possible from the food to be cooked. Experiments in the laboratory have shown that cooking times can be shortened by more than 50% while at the same time significantly saving energy. Another significant advantage of this mode is that the wall elements 11 to 15 remain significantly colder than the beam walls of an enamelled furnace muffle. Dirt burns less strongly, which is another major advantage of this concept. By selective adjustment of the radiation reflection as in the FIGS. 1 to 7 already described in various embodiments, a very homogeneous energy distribution in the interior is guaranteed. The proportion of the necessary long-wave IR radiation is inventively by the absorption behavior the glass ceramic itself determined or by local partial coatings on the inner surfaces of the wall elements 11 to 15, in particular by using decorative paints, which are firmly connected to the glass-ceramic surface. Laboratory experiments have further shown that when using short-wave IR radiation, a crispy browning of a pork loin is possible even when the casserole is covered with a glass lid. In conventional ovens, a roast pork can only be crunchy on a non-covered casserole. In this case, however, the fat splashes during the cooking process very heavy pollution of the entire interior. With the oven according to the invention, the preparation of roast pork even with closed glass ceilings is possible with the advantage that the interior is not polluted by fat splash.

Claims (17)

Furnace muffle having a receiving space which is delimited at least in regions by wall elements (11-15), at least one of the wall elements (11-15) being permeable to IR radiation or having an area permeable to IR radiation,
characterized,
that in the region of the outer surface facing away from the receiving space (17) of the wall element (11-15), an IR radiation-reflecting reflection element (30) is arranged. Furnace muffle according to claim 1,
characterized,
that the wall element consists of glass or glass ceramic. Furnace muffle according to claim 1 or 2,
characterized,
that outside of the receiving space in the region of the outer surface (17) of at least one of the wall elements (11 - 15) is arranged a radiator (20). Furnace muffle according to one of claims 1 to 3,
characterized,
in that one or more structural elements (18) for generating stray radiation are arranged in the region of the outer surface (17) of the wall element (11-15) and / or in the wall element (11-15). Furnace muffle according to claim 4,
characterized,
that the structural elements (18) are arranged so that zones are formed with different scattering behavior. Furnace muffle according to claim 4 or 5,
characterized,
that the structural elements (18) in one piece on the wall element (11-15) are formed. Furnace muffle according to one of claims 1 to 5,
characterized,
in that absorption elements are introduced into and / or applied to the wall element (11-15) which absorb IR radiation. Furnace muffle according to one of claims 1 to 7,
characterized,
that the existing glass or glass-ceramic wall element (11-15) IR radiation is partially absorbed. Furnace muffle according to one of claims 1 to 8,
characterized,
in that the reflection element (30) is applied to the outer surface (17) of the wall element (11-15). Furnace muffle according to claim 9,
characterized,
that the reflection element (30) as a coating, for example, noble metal or metal coating, for example silver, tin, aluminum, metal oxide - in particular tin oxide -, azo, Itobeschichtung is applied. Furnace muffle according to one of claims 1 to 8,
characterized,
that the reflection element (30) as a sheet-like blank, in particular as a reflecting film in the area of the outer surface (17) is arranged. Furnace muffle according to one of claims 1 to 11,
characterized,
that the reflection element (30) on its outer surface (17) of the wall element (11-15) facing side at least partially with a surface structure (structural elements (18)) is provided. Furnace muffle according to one of claims 7 to 12,
characterized,
that the absorption elements (19) are arranged so that zones are formed with different absorption behavior. Furnace muffle according to one of claims 7 to 13,
characterized,
that the absorption elements (19) as a decor, for example as screen printing or electro-photographic printing on the wall element (11-15) are coated. Furnace muffle according to one of claims 7 to 14,
characterized,
that the absorption elements (19) are formed of printed ceramic colors. Furnace muffle according to one of claims 1 to 15,
characterized,
that the heating element is generated (20) IR-radiation having a wavelength in the range less than 1.4 microns. Furnace muffle according to one of claims 1 to 16,
characterized,
that the reflection element (30) by an insulating element (40) is formed or supported by it.

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