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EP 1 947 393 B1 |
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EUROPEAN PATENT SPECIFICATION |
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Mention of the grant of the patent: |
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15.07.2009 Bulletin 2009/29 |
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Date of filing: 22.01.2007 |
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International Patent Classification (IPC):
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Oven and method for its operation
Ofen und Verfahren für dessen Betrieb
Four et procédé pour son fonctionnement
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Designated Contracting States: |
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AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HU IE IS IT LI LT LU LV MC NL PL PT RO SE
SI SK TR |
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Date of publication of application: |
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23.07.2008 Bulletin 2008/30 |
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Proprietor: Electrolux Home Products Corporation N.V. |
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1930 Zaventem (BE) |
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Inventor: |
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- Fich Pedersen, Thomas
91541 Rothenburg (DE)
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Representative: Hochmuth, Jürgen |
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AEG Hausgeräte GmbH,
Patente, Marken & Lizenzen 90327 Nürnberg 90327 Nürnberg (DE) |
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References cited: :
DE-A1- 2 557 867 GB-A- 1 177 434 US-B1- 6 615 819
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DE-A1- 10 313 913 US-A- 4 671 250
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Note: Within nine months from the publication of the mention of the grant of the European
patent, any person may give notice to the European Patent Office of opposition to
the European patent
granted. Notice of opposition shall be filed in a written reasoned statement. It shall
not be deemed to
have been filed until the opposition fee has been paid. (Art. 99(1) European Patent
Convention).
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[0001] The invention relates to an oven, especially to a domestic oven, with a cooking cavity,
wherein grill means are arranged in the cavity for grilling food placed in the cavity.
Furthermore, the invention relates to a method for operating such an oven.
[0002] Ovens of this kind are well known in the art and useful for an effective grilling
of food placed in the cavity of the oven. Examples are shown in
US 6 615 819 B1 and in
DE 103 13 913 A1. The grill function used today does not use any convective movement of the air in
the oven cavity. On the contrary, it is aimed that the heat is transferred almost
to 100 % to the food by radiation to obtain a good grilling result. When the grill
is used in this way, the top part of the oven is heated by radiation and most importantly
by natural convection around the grill element, as long as it is mounted inside the
cavity.
[0003] In distinction to hot air ovens the heat is transferred during the grilling operation
mainly by radiation, which is beneficial in some cases. In the case of a hot-air cooking
operation air is heated and fed to the food in the cavity.
[0004] The grill element will normally reach a surface temperature above 500 to 600 °C.
Consequently, the temperature of the cavity roof can easily reach more than 400 to
450 °C. Below the grill the air is only heated slowly, because the natural convection
primarily occurs around the grill element. Therefore, the air in the lower part of
the oven is only heated slowly by a combination of conduction in the air and heating
from the walls and bottom that are heated by the radiation from the grill. Therefore,
the food is mainly heated by radiation from the grill element.
[0005] Due to the quite high temperatures of the roof of the cavity during grilling operation
it is problematic to cover the inside of the cavity with a non-stick coating which
normally cannot bear temperatures above 325 °C.
[0006] Therefore, it is an object of the invention to provide an oven, especially a domestic
oven, which allows an effective grilling operation but makes sure that the maximum
temperature of the roof of the oven does not exceed a temperature at which the use
of a usual non-stick coating would not be possible. Furthermore, the efficiency of
the grilling operation has to be improved.
[0007] The solution of this object according to the invention relating to an oven is characterized
in that fan means are arranged in the cavity for generating a slow air flow within
the cavity, wherein the air flow is low enough not to influence significantly the
radiation heat of the grill means and wherein the fan means are adjustable to having
a fan rotating with a speed between 200 rpm and 600 rpm.
[0008] The air flow produced by the fan means is to be "low", i. e. it is not comparable
to the air flow used in hot-air ovens. Consequently, the radiation heat effect should
be maintained substantially. The heat brought into the food is aimed to be at least
75 % due to radiation. In the case of hot-air ovens the main heat introduction into
the food is done by convection of the hot air and not by radiation.
[0009] Compared with the fan employed for a hot-air oven, which usually operates at a speed
between 1,500 and 2,500 rpm, the fan speed according to the present invention is relatively
low, i. e. at a maximum of about 66 % of the minimum speed of a fan used for hot-air
applications. More precisely, the fan means are adjustable to having the fan rotating
with a speed between 200 rpm and 600 rpm.
[0010] As can be seen, a relatively low air flow is produced according to the present invention.
[0011] The fan means can be arranged at a reverse side of the cavity, opposite to a door
of the cavity. Furthermore, the gill means can be arranged in a top region (roof region)
of the cavity.
[0012] Preferably, the grill means are formed by a heating coil which extends in a plane.
Usually, the grill means are an electrical heating element.
[0013] The method for operating an oven, especially of a domestic oven, employs an oven
with a cooking cavity, wherein grill means are arranged in the cavity for grilling
food placed in the cavity. The method is characterized in that an air flow is generated
by fan means, which are arranged in the cavity, wherein the air flow is low enough
not to influence significantly the radiation heat of the grill means and wherein a
fan of the fan means is operated at a speed between 200 rpm and 600 rpm.
[0014] The present invention thus describes a combined use of the grill element of the oven
with a fan mounted preferably at the back wall of the oven cavity, operated at a speed
preferably between 50 and 800 rpm. Such a fan is normally present in a convection
oven and is normally also equipped with a ringshaped heating element, to provide hot
air for the convection cooking mode. Hot air cooking normally involves a fan speed
of 1,500 to 2,500 rpm, but at this high speed the grill element is cooled to such
a degree that the heat is mainly transferred by convection, which is aimed for in
the case of a hot-air oven.
[0015] However, by lowering the speed the invention has observed the following beneficial
effect: The roof of the oven is no longer heated by the cushion of hot air from the
natural convection around the grill element; the grill element is still hot enough
to make sure that the main heat transfer to the food is done by radiation. The slow
air speed resulting from the slow fan ensures that a more even distribution of the
air temperature is obtained. This in fact improves the result of the grilling compared
to normal grill mode as the gentle convection provides an extra heat transfer without
drying the surface excessively. In addition the grill effect becomes more uniformly
distributed.
[0016] The slow fan moves the air heated by the grill element away from the roof, and thereby
roof temperatures of less than 325 °C can be maintained even with grill element surface
temperatures up to 550 °C.
[0017] Consequently, the invention has the following advantages:
[0018] The grilling effect is distributed more evenly on the food as it is a combination
of radiation and convection, but with a large percentage of it from radiation.
[0019] The maximum temperature in the roof of the oven and on the top part of the walls
is reduced to below 325 °C for an oven centre air temperature setting of 250 °C, making
the use of non-stick coatings with temperature limits in this range inside the cavity
possible.
[0020] The grilling performance of a household oven grill is thus improved significantly.
[0021] In the drawings an embodiment of the invention is depicted.
- Fig. 1
- shows schematically a cross-sectional side view of a domestic oven,
- Fig. 2
- shows the cavity of the oven in view "A" according to fig. 1 with a fan standing still
(static grill mode) and
- Fig. 3
- shows the cavity of the oven in view "A" according to fig. 1 with rotating fan (slow
fan grill mode).
[0022] Fig. 1 shows a domestic oven 1. It has a cooking cavity 2 which can be opened by
a door 9 to put food into the cavity 2 and to take cooked food out of it. The oven
1 is equipped with grill means 3. The grill means are a heating coil 11 which are
arranged in the top region 10 (roof region) of the cavity 2. Opposite to the door
9, the cavity 2 has a reverse side 8. Here, fan means 4 are arranged. The fan means
4 have a fan 7 which is mounted on a shaft 12, which in turn is driven by an electrical
motor 13.
[0023] The view "A" according to fig. 1 is shown in fig. 2. Here the fan 7 is not moving.
The grill means 3 are on power so that radiation heat 6is generated which is shown
in fig. 2 only schematically.
[0024] The operation according to the invention is depicted in fig. 3. Here the fan 7 is
rotating around the axis 14. Thus, a slow air flow 5 is generated which is indicated
by arrows.
[0025] According to the invention the fan means 4 are arranged in the cavity 2 for generating
the slow air flow 5 within the cavity 2, wherein the air flow 5 is low enough not
to influence significantly the radiation heat 6 of the grill means 3. Specifically,
the fan 7 rotates with a revolution which is relatively low compared with usual operation
in hot-air ovens. Here, the speed of the fan 7 is at a maximum of 1,000 rpm, preferably
significantly below that value.
[0026] The slow air flow 5 thus cools the roof of the cavity 2 in such a way that the maximum
temperature is approximately below 325 °C. This allows the coating of the inside of
the cavity with a non-stick cover which facilitates to keep the inside of the cavity
2 clean.
[0027] Also, the efficiency of the grilling operation is improved. The heat is better distributed,
but without having an effect as known from hot-air applications. On the contrary the
major part of the heat introduction is done by radiation, so that the food in the
cavity is grilled.
[0028] It is possible to connect the motor 13 with a control unit so that a desired speed
of the fan 7 can be adjusted and maintained. It is possible to input the desired revolution
of the fan. First suitable effects are obtained when the fan 7 rotates with a speed
of 50 rpm. This speed is not comparable with that one necessary to establish a hot-air
mode.
Reference Numerals
[0029]
- 1
- Oven (domestic oven)
- 2
- Cavity
- 3
- Grill means
- 4
- Fan means
- 5
- Slow air flow
- 6
- Radiation heat
- 7
- Fan
- 8
- Reverse side
- 9
- Door
- 10
- Top region
- 11
- Heating coil
- 12
- Shaft
- 13
- Motor
- 14
- Axis
1. Oven (1), especially domestic oven, with a cooking cavity (2), wherein grill means
(3) are arranged in the cavity (2) for grilling food placed in the cavity (2), and
fan means (4) are arranged in the cavity (2), characterized in that the fan means (4) are for generating a slow air flow (5) within the cavity (2), wherein
the air flow (5) is low enough not to influence significantly the radiation heat (6)
of the grill means (3) and wherein the fan means (4) are adjustable to having a fan
(7) rotating with a speed between 200 rpm and 600 rpm.
2. Oven according to claim 1, characterized in that the fan means (4) are arranged at a reverse side (8) of the cavity (2), opposite
to a door (9) of the cavity (2).
3. Oven according to at claim 1 or 2, characterized in that the grill means (3) are arranged in a top region (10) of the cavity (2).
4. Oven according to at least one of claims 1 to 3, characterized in that the grill means (3) are formed by a heating coil (11) which extends in a plane.
5. Oven according to at least one of claims 1 to 4, characterized in that the grill means (3) are an electrical heating element.
6. Method for operating an oven (1), especially a domestic oven, which has a cooking
cavity (2), wherein grill means (3) are arranged in the cavity (2) for grilling food
placed in the cavity (2),
wherein an air flow (5) is generated by fan means (4), which are arranged in the cavity
(2), characterized in that the air flow (5) is low enough not to influence significantly the radiation heat
(6) of the grill means (3) and wherein a fan (7) of the fan means (4) is operated
at a speed between 200 rpm and 600 rpm.
1. Ofen (1), insbesondere ein Haushaltsofen, mit einem Koch-Innenraum (2), wobei in dem
Innenraum (2) ein Grillmittel (3) zum Grillen von Nahrungsmitteln in dem Innenraum
(2) angeordnet ist, und wobei im Innenraum (2) ein Ventilatormittel (4) angeordnet
ist, dadurch gekennzeichnet, dass das Ventilatormittel (4) der Erzeugung eines langsamen Luftstroms (5) im Innenraum
(2) dient, wobei der Luftstrom (5) ausreichend schwach ist, um die Strahlungshitze
(6) des Grillmittels (3) nicht wesentlich zu beeinflussen, und wobei das Ventilatormittel
(4) so einstellbar ist, dass der Ventilator (7) mit einer Drehzahl zwischen 200 UpM
und 600 UpM betrieben werden kann.
2. Ofen gemäß Anspruch 1, dadurch gekennzeichnet, dass das Ventilatormittel (4) an einer Rückseite (8) des Innenraums (2) gegenüber einer
Tür (9) des Innenraums (2) angeordnet ist.
3. Ofen gemäß Anspruch 1 oder 2, dadurch gekennzeichnet, dass das Grillmittel (3) in einem oberen Bereich (10) des Innenraums (2) angeordnet ist.
4. Ofen gemäß mindestens einem der Ansprüche 1 bis 3, dadurch gekennzeichnet, dass das Grillmittel (3) durch eine Heizspule (11) gebildet wird, die sich in einer Ebene
erstreckt.
5. Ofen gemäß mindestens einem der Ansprüche 1 bis 4, dadurch gekennzeichnet, dass das Grillmittel (3) ein elektrisches Heizelement ist.
6. Verfahren zum Betrieb eines Ofens (1), insbesondere eines Haushaltsofens, der mit
einem Koch-Innenraum (2) ausgestattet ist, wobei das Grillmittel (3) im Innenraum
(2) zum Grillen von Nahrungsmitteln angeordnet ist, die im Innenraum (2) platziert
sind, wobei durch ein im Innenraum (2) angeordnetes Ventilatormittel (4) ein Luftstrom
(5) erzeugt wird, dadurch gekennzeichnet, dass der Luftstrom (5) ausreichend schwach ist, um die Strahlungshitze (6) des Grillmittels
(3) nicht wesentlich zu beeinflussen, und wobei ein Ventilator (7) des Ventilatormittels
(4) mit einer Drehzahl zwischen 200 UpM und 600 UpM betrieben wird.
1. Four, en particulier four domestique, avec une cavité de cuisson (2), dans laquelle
des moyens formant gril (3) sont agencés dans la cavité (2) pour griller des aliments
placés dans la cavité (2), et des moyens de ventilation (4) sont agencés dans la cavité
(2),
caractérisé en ce que les moyens de ventilation (4) sont destinés à produire un flux d'air lent (5) dans
la cavité (2), où le flux d'air (5) est suffisamment bas pour ne pas agir d'une manière
importante sur la chaleur de rayonnement (6) du moyen formant gril (3), et où les
moyens de ventilation (4) sont ajustables pour avoir un ventilateur (7) tournant à
une vitesse entre 200 tr/min et 600 tr/min.
2. Four selon la revendication 1, caractérisé en ce que les moyens de ventilation (4) sont agencés à un côté arrière (8) de la cavité (2),
en face d'une porte (9) de la cavité (2).
3. Four selon la revendication 1 ou 2, caractérisé en ce que les moyens formant gril (3) sont agencés dans une région supérieure (10) de la cavité
(2).
4. Four selon au moins une des revendications 1 à 3, caractérisé en ce que les moyens formant gril (3) sont formés par une bobine chauffante (11) qui s'étend
dans un plan.
5. Four selon au moins une des revendications 1 à 4, caractérisé en ce que les moyens formant gril (3) sont un élément chauffant électrique.
6. Procédé pour faire fonctionner un four (1), en particulier un four domestique, qui
possède une cavité de cuisson (2) dans laquelle des moyens formant gril (3) sont agencés
dans la cavité (2) pour griller des aliments placés dans la cavité (2),
où un flux d'air (5) est produit par des moyens de ventilation (4), qui sont agencés
dans la cavité (2), caractérisé en ce que le flux d'air (5) est suffisamment bas pour ne pas agir d'une manière importante
sur la chaleur de rayonnement (6) des moyens formant gril (3), et où un ventilateur
(7) du moyen de ventilation (4) fonctionne à une vitesse entre 200 tr/min et 600 tr/min.
REFERENCES CITED IN THE DESCRIPTION
This list of references cited by the applicant is for the reader's convenience only.
It does not form part of the European patent document. Even though great care has
been taken in compiling the references, errors or omissions cannot be excluded and
the EPO disclaims all liability in this regard.
Patent documents cited in the description