EP1992879A1

EP1992879A1 - Cooking oven, especially domestic cooking oven

Info

Publication number: EP1992879A1
Application number: EP07009765A
Authority: EP
Inventors: Karl Dr. Leidig; Florian Ruther; Christoph Walther
Original assignee: Electrolux Home Products Corp NV; AEG Hausgeraete GmbH
Current assignee: Electrolux Home Products Corp NV; AEG Hausgeraete GmbH
Priority date: 2007-05-16
Filing date: 2007-05-16
Publication date: 2008-11-19

Abstract

The invention relates to a cooking oven (1), especially to a domestic cooking oven, with a heatable cavity (2), wherein a fan (3) having a rotating fan wheel (4) is arranged in or adjacent to the cavity (2), wherein a first fluidic connection (5) is arranged between at least one air input opening (6) of the cavity (2) and the fan (3) and wherein at least one second fluidic connection (7) is arranged between an air output opening (8) of the fan (3) and the cavity (2). To improve the homogeneity of the distribution of hot air in the cavity the invention is characterized in that at least one cover element (9) is arranged which forms a wall for the air blown by the fan (3) along the second fluidic connection (7), wherein the cover element (9) extends substantially along the entire height of the cavity (2) and wherein the cover element (9) is formed to establish a substantial uniform air flow along substantial the entire height of the cover element (2).

Description

The invention relates to a cooking oven, especially to a domestic cooking oven, with a heatable cavity, wherein a fan having a rotating fan wheel is arranged in or adjacent to the cavity, wherein a first fluidic connection is arranged between at least one air input opening of the cavity and the fan and wherein at least one second fluidic connection is arranged between an air output opening of the fan and the cavity.
Ovens of this kind are well-known in the art. The dish to be cooked in the oven is exposed to hot air which is transported by a fan. Most of today's hot air systems in ovens generate a three-dimensional air flow inside the cavity of the oven. In the case that a plurality of trays (e. g. baking trays) is arranged on top of each other in the cavity it is not ensured that the food placed on the different trays is exposed to heat in the same manner. Consequently, the result of the cooking / baking process is sometimes not satisfactory.
When trying to generate a symmetrical two-dimensional air flow pattern and volume flow using a fan wheel in a housing that has openings on the left and right side, two problems are experienced.
Firstly, the fan wheel blows air out not perfectly radial but at an angel. This situation is shown in FIG 2 and depicted by the arrows extending away from the fan wheel 4. Furthermore, the air blown to the top and bottom is forced to the side outlet openings which lead to a higher air volume flow in the upper and lower corners. Due to the two effects the air volume flow distribution at the outlet of a usual fan cover 27 becomes inhomogeneous as shown by the air distribution 26 in FIG 2. This influences also the air flow pattern over the different baking trays placed in the cavity of the oven.
Furthermore, the air exits the fan cover not in a perpendicular direction but rather at an angle resulting from the angle the air is blown out from the fan wheel.
Secondly, the inlet of such a fan is also problematic because a rotation of the air that is sucked in the fan is also generated. As shown in FIG 3 for a conventional solution showing the air flow in front of the fan less air is sucked in from the upper and lower regions of the cavity if the fan wheel 4 is mounted in the centre as it is depicted by the arrows.
Therefore, it is an object of the invention to improve the homogeneity of the distribution of hot air in the cavity when the fan is operated. This should be reached specifically when several baking trays are inserted into the cavity. More specifically, a two-dimensional air flow pattern is desired which is equal on every tray. So, a better cooking or baking result should be achieved.
The solution of this object according to the invention is characterized in that at least one cover element is arranged which forms a wall for the air blown by the fan along the second fluidic connection, wherein the cover element extends substantially along the entire height of the cavity and wherein the cover element is formed to establish a substantial uniform air flow along substantial the entire height of the cover element. Preferably, the cover element extends along at least 80 % of the height of the cavity.
The fan is normally arranged in the rear part of the cavity, opposite to a front door of the oven. The axis of rotation of the fan wheel is usually arranged horizontally and from the rear side to the front side of the cavity.
The cover element according to the invention has - according to a first concept - a first section extending substantial parallel to the backside of the cavity and has a second section wherein the distance between the cover element and the backside of the cavity becomes smaller in the second section when moving away from the fan. Herewith, a noz-zle-like design is created by the fan cover. The first section is preferably adjacent to the fan while the second section is remote from the fan.
The cover element, especially its second section, can have different distances from the backside of the cavity along its height in a vertical section at at least one location of the second fluidic connection. Thus, a kind of air regulator is achieved to obtain a desired distribution of air flow in vertical direction. The cover element, especially its second section, can have a smaller distance from the backside of the cavity in the upper and lower region than in the middle region. Preferably, the distance from the backside of the cavity is symmetrically in the upper and lower region relatively to the middle region.
Another concept of the invention, which can be employed alternatively or additionally, comes up with the cover element having a plurality of air guiding channels which are arranged horizontally and are formed by at least two guiding ribs arranged at or on the cover element. The guiding ribs can have a length which is between 2 times and 4 times of the distance of the guiding ribs, especially three times as long. The length of the guiding ribs can alter in vertical direction, to achieve an air regulation effect. The length of the guiding ribs can be longer in the upper and in the lower region than in the middle region.
Another feature of the invention is characterized in that a cover plate is arranged in front of the input opening of the fan, wherein the cover plate has a plurality of openings for the entry of air.
The cover plate can have a homogeneous distribution of openings; the openings in the cover plate can have a round shape and can be equal in diameter.
Alternatively, to create a desired flow of the air the cover plate can also have a non-homogeneous distribution of openings; the openings in the cover plate can have a round shape and can have at least partially different diameters.
A further embodiment of the invention has a heating element which is arranged in front of the fan. The heating element can be arranged between the cover plate and the fan. It is preferably ring-shaped.
The proposed solution has different advantages:
To overcome the above mentioned drawbacks the fan cover of the invention has thus outlet openings with a characteristic geometry. It spans almost the whole height of the cavity to provide all levels where trays can be inserted with the same or approximately the same air volume flow.
Further, the channel from the fan wheel to the outlet narrows like a nozzle which increases the flow resistance and herewith the pressure drop and levels out the inhomogeneous pressure profile and air speed profile generated by the fan to a certain degree. To achieve an even higher level of homogeneity of the air speed the mentioned air regulators can be inserted in addition to the usage of a nozzle or replacing it.
To get more laminar air flow that exits the fan cover with the same direction the mentioned channels can be employed. Their length can be about three times their width and they can be combined with the air regulator principle, because longer channels and guiding ribs respectively give a higher flow resistance as does a smaller opening area. Those channels and ribs respectively can further work as a "circulation divider" to get rid of the rotation of the air inside the cavity which is caused by the non-perpendicular exiting direction of the air from the fan cover. Additionally guiding vanes can be placed inside the cavity and/or mounted at the tray supports which have the same circulation divider effect and help to generate the desired two-dimensional air flow pattern.
Also the inlet is made to deal with the mentioned problems of the rotation of the air sucked in and the differing air speed (volume flow) over the height of the cavity. A cover plate can thus put in front of the inlet opening of the fan which flattens the low pressure profile at the inlet by increasing flow resistance and reshapes the inlet from a hole to two slits which prevents the rotating of the air to a certain degree. Further, this inlet cover levels out the pressure difference between the trays on the different levels and the inlet opening. By this way almost the same amount of air is sucked in on every level. Additionally air regulators and/or channels as described above can be used to further modify the air flow.
If air is needed to be sucked in over the whole backside of the cavity and not only through the two slits the inlet cover can be extended over the whole back of the cavity and be punctured with holes which could be distributed in a specific way and/or have specific different sizes to create any intended air inlet profile (distribution of entering volume flow over the cover area).
Further with this kind of assembly the ring shaped heating element could be placed not only around the fan as know in the prior art, but also in front of the fan in the sucking channel. This has the advantage that the heated air is mixed up while pressed through the fan wheel and therefore the air temperature distribution over the outlet opening is more even. For this alternative it is crucial where the holes are put in the inlet cover because the inlet cover has to block the food from the direct radiation coming from the heating element.
Using such a fan cover helps to get the desired two-dimensional air flow pattern and the same air volume flow on all trays on all levels. Also the left and right half of the tray is heated equally. This results in a very even heat distribution over one tray and over the trays on different height levels.
In the drawings embodiments of the invention are depicted.

FIG 1: shows a sectional side view through a domestic cooking oven, wherein different baking trays are arranged in the cavity of the oven,
FIG 2: shows the air flow and the air distribution in a prior art oven seen in direction "C" according to FIG 1,
FIG 3: shows the air flow in front of the fan of the oven according to the prior art, seen in direction "C" according to FIG 1,
FIG 4: shows a cover element arranged in the backside of the cavity according to a first embodiment of the invention, seen in direction "C" according to FIG 1,
FIG 5: shows the cover element according to FIG 4 in a top plan view,
FIG 6: shows a second embodiment of the invention in a top plan view,
FIG 7: shows the section A-B according to FIG 6,
FIG 8: shows a third embodiment of the invention with air guiding channels, seen in direction "C" according to FIG 1,
FIG 9: shows a cover plate of the fan according to a further embodiment of the invention, seen in direction "C" according to FIG 1,
FIG 10: shows the arrangement according to Fig 9, viewed in direction "E" according to FIG 9,
FIG 11: shows an alternative embodiment of the cover plate of the fan, seen in direction "C" according to FIG 1,
FIG 12: shows the arrangement according to Fig 11, viewed in direction "F" according to FIG 11 and
FIG 13: shows a top plan view of the air flow reached by the invention.

FIG 1 shows the general design of a cooking oven 1, specifically of a domestic cooking oven, having a cavity 2. The cavity 2 is closed at the front of the oven 1 by a door 10. At the rear side or backside 13 of the cavity a fan 3 is arranged, having a fan wheel 4 which rotates around an axis 11 of rotation. A plurality of trays 24 can be'inserted into the cavity 2, which are arranged on top of each other.
Without the concept of the invention an air flow and an air distribution 26 is reached as depicted in FIG 2 and FIG 3 as explained above.
To overcome the problems in connection with the air flow pattern and the air distribution according FIG 2 and FIG 3 the invention suggests the following alternative or additive features:
In FIG 4 and FIG 5 a cover element 9 is shown which improves the homogeneity of the air flow created by the operation of the fan 3.
In general, the fan 3 with its rotating fan wheel 4 is arranged adjacent to the backside 13 of the cavity 2 and sucks in air from the cavity 2 from an air input opening 6 via a first fluidic connection 5 (see FIG 5). The air is transported by the fan wheel 4 and is blown out to an air output opening 8 (or more specific: to two output openings 8) via a second fluidic connection 7.
Thus, the first fluidic connection 5 is arranged between the air input opening 6 of the cavity 2 and the fan 3 and the second fluidic connection 7 is arranged between an air output opening 8 of the fan 3 and the cavity 2. This is depicted in FIG 5 by the lines with the arrows.
As can be seen in FIG 4 and FIG 5 a cover element 9 is arranged which forms a wall for the air blown by the fan 3 along the second fluidic connection 7. The cover element 9 extends substantially along the entire height of the cavity 2, see FIG 4. Furthermore, the cover element 9 is formed to establish a substantial uniform air flow along substantial the entire height of the cover element 2.
According to the embodiment of FIG 4 and FIG 5 this is achieved by a first section 12 of the cover element 9 which is arranged parallel to the backside 13 of the cavity and adjacent to the fan 3. At the end of the first section 12 of the cover element 9 a second section 14 is arranged. The distance D (see FIG 5) between the backside 13 and the cover element 9 measured in horizontal direction and along an axis between the front door 10 and the backside 13 of the cavity 2 becomes smaller when moving away from the fan 3. Thus, a nozzle-like design is created which improves the homogeneity of the air flow. The air is blown out by the fan 3 at the air output opening 8 of the cover element 9.
As can be seen in FIG 6 and FIG 7 an air regulating element can be employed in addition (as depicted) or as an alternative to the design shown in FIG 4 and FIG 5. The air regulator 25 is basically a sheet metal element which creates an altering distance d between the cover element 9 and the backside 13 of the cavity 2 with respect to the vertical height. As can be seen in FIG 7 the distance d is a maximum in a middle region 17 of the cavity 2 and becomes smaller in an upper region 15 and lower region 16. Thus, the air flow can be influenced by choosing the run of the distance d along the height of the cavity 2.
Another alternative or additive possibility to homogenise and to influence the air flow from the fan 3 into the cavity 2 is shown in FIG 8. Here a plurality of air guiding channels 18 is arranged on the sheet metal of the cover element 9. The air guiding channels 18 are formed by two adjacent guiding ribs 19, 20 which are arranged at a vertical distance x. Preferably the length L of the ribs 19, 20 is about three times of the distance x. The length L of the ribs 19, 20 can also alter along the vertical height of the cover element 9, as shown in the left part of FIG 8. The longer the ribs 19, 20 are the higher is the flow resistance which is exerted onto the air flowing through the air guiding channels 18. Thus, a regulation of the air flow can occur by choosing the right length L of the ribs 19, 20.
In FIG 9 and FIG 10 another possibility is shown by which the air flow can be homogenised. Here, a cover plate 21 is arranged in front of the fan 3. The cover plate 21 has a plurality of openings 22, preferably bores, which can have the same diameter or different diameters.
In the left upper corner of the cover plate 21 in FIG 9 a homogeneous distribution of openings 22 is shown which have all the same diameter.
In the right upper corner of the cover plate 21 in this figure openings 22 are shown which have different diameters, i. e. several classes of diameters.
In FIG 11 a cover plate 21 is shown which has a substantial homogeneous distribution of openings 22 with the same diameter but leaves a certain field with no bores in the middle part of the cover plate 21, behind which the ring-shaped fan is arranged. By selecting the diameter of the openings 22 and their distribution it can be made sure that a quite uniform air flow enters into the fan 3.
In the embodiment according to FIG 11 and FIG 12 another feature is depicted which is beneficially. Here a heating element 23 with a circular shape is placed between the cover plate 21 and the fan wheel 4. So, the air sucked into the fan 3 is heated up. The heat introduced by the heating element 23 into the air is homogeneously distributed in the air when it leaves the cover element 9 at both sides.
In FIG 13 a top plan view is depicted which shows schematically the flow pattern in one certain level of height in the cavity 2. Due to the pre-described provisions an evenly distributed air flow is guaranteed which is substantial equal on all tray levels.

Reference Numerals

1: Cooking oven (domestic cooking oven)
2: Cavity
3: Fan
4: Fan wheel
5: First fluidic connection
6: Air input opening
7: Second fluidic connection
8: Air output opening
9: Cover element
10: Front door
11: Axis of rotation
12: First section
13: Backside
14: Second section
15: Upper region
16: Lower region
17: Middle region
18: Air guiding channel
19: Guiding rib
20: Guiding rib
21: Cover plate
22: Opening
23: Heating element
24: Tray
25: Air regulator
26: Air distribution
27: Fan cover
D: Distance
d: Distance
L: Length
x: Distance of the guiding ribs

Claims

Cooking oven (1), especially domestic cooking oven, with a heatable cavity (2), wherein a fan (3) having a rotating fan wheel (4) is arranged in or adjacent to the cavity (2), wherein a first fluidic connection (5) is arranged between at least one air input opening (6) of the cavity (2) and the fan (3) and wherein at least one second fluidic connection (7) is arranged between an air output opening (8) of the fan (3) and the cavity (2),
characterized in that
at least one cover element (9) is arranged which forms a wall for the air blown by the fan (3) along the second fluidic connection (7), wherein the cover element (9) extends substantially along the entire height of the cavity (2) and wherein the cover element (9) is formed to establish a substantial uniform air flow along substantial the entire height of the cover element (2).
Cooking oven according to claim 1, characterized in that the cover element .(9) extends along at least 80 % of the height of the cavity (2).
Cooking oven according to claim 1 or 2, characterized in that the fan (3) is arranged in the rear part of the cavity (2), opposite to a front door (10).
Cooking oven according to at least one of claims 1 to 3, characterized in that the axis of rotation (11) of the fan wheel (4) is arranged horizontally and from the rear side to the front side of the cavity (2).
Cooking oven according to at least one of claims 1 to 4, characterized in that the cover element (9) has a first section (12) extending substantial parallel to the backside (13) of the cavity (2) and has a second section (14) wherein the distance (D) between the cover element (9) and the backside (13) of the cavity (2) becomes smaller in the second section (12) when moving away from the fan (3).
Cooking oven according to claim 5, characterized in that the first section (12) is adjacent to the fan (3) and the second section (14) is remote from the fan (3).
Cooking oven according to at least one of claims 1 to 6, characterized in that the cover element (9), especially its second section (14), has different distances (d) from the backside (13) of the cavity (2) along its height in a vertical section at at least one location of the second fluidic connection (7).
Cooking oven according to claim 7, characterized in that the cover element (9), especially its second section (14), has a smaller distance (d) from the backside (13) of the cavity (2) in the upper (15) and lower (16) region than in the middle region (17).
Cooking oven according to claims 8, characterized in that the distance (d) from the backside (13) of the cavity (2) is symmetrically in the upper and lower region (15, 16) relatively to the middle region (17).
Cooking oven according to at least one of claims 1 to 9, characterized in that the cover element (9) has a plurality of air guiding channels (18) which are arranged horizontally and are formed by at least two guiding ribs (19, 20) arranged at or on the cover element (9).
Cooking oven according to claim 10, characterized in that the guiding ribs (19, 20) have a length (L) which is between 2 times and 4 times of the distance (x) of the guiding ribs (19, 20).
Cooking oven according to claim 10 or 11, characterized in that the length (L) of the guiding ribs (19, 20) alter in vertical direction.
Cooking oven according to claim 12, characterized in that the length (L) of the guiding ribs (19, 20) is longer in the upper (15) and in the lower (16) region than in the middle region (18).
Cooking oven according to at least one of claims 1 to 13, characterized in that a cover plate (21) is arranged in front of the input opening (6) of the fan (3), wherein the cover plate (21) has a plurality of openings (22) for the entry of air.
Cooking oven according to claim 14, characterized in that the cover plate (21) has a homogeneous distribution of openings (22).
Cooking oven according to claim 14, characterized in that the openings (22) in the cover plate (21) have a round shape and are equal in diameter.
Cooking oven according to claim 14, characterized in that the cover plate (21) has a non-homogeneous distribution of openings (22).
Cooking oven according to claim 14, characterized in that the openings (22) in the cover plate (21) have a round shape and have at least partially different diameters.
Cooking oven according to at least one of claims 1 to 18, characterized in that a heating element (23) is arranged in front of the fan (3).
Cooking oven according to at least one of claims 14 to 18 and claim 19, characterized in that the heating element (23) is arranged between the cover plate (21) and the fan (3).
Cooking oven according to claims 19 or 20, characterized in that the heating element (23) is ring-shaped.