AU2014200852B2

AU2014200852B2 - Baking oven with climate controlled temperature limiter

Info

Publication number: AU2014200852B2
Application number: AU2014200852A
Authority: AU
Inventors: Reto Marco Bachofner; Ulrich Frey; Roy Keller
Original assignee: V-Zug AG
Current assignee: V-Zug AG
Priority date: 2013-03-07
Filing date: 2014-02-20
Publication date: 2017-11-30
Anticipated expiration: 2034-02-20
Also published as: EP2775215A2; CH705766A2; SI2775215T1; CN104026995A; PL2775215T3; DK2775215T3; AU2014200852A1; CN104026995B; EP2775215B1; EP2775215A3

Abstract

Abstract A household baking oven comprises a cooking chamber (2) and a hot air heater (5). In normal operation 5 the temperature in the cooking chamber (2) is maintained at a desired temperature by means of a first temperature sensor (12) and a feedback loop (14), which controls the heating power of the hot air heater (5). The device fur ther comprises a climate sensor (19) comprising a first 1o opening (16) in the cooking chamber (2) and a second tem perature sensor (27) arranged outside the first opening (16) . When the temperature at the second temperature sen sor (27) exceeds a threshold temperature, the energy sup ply to the hot air heater (5) is interrupted or at least is reduced, such that the temperature in the cooking chamber (2) decreases. In this manner, foodstuff can be cooked with low energy consumption. 22 4a37 2_ 1 36 24b 15 3 20-/20a 28 23_ 10b 35-- 4b 37 9_ Fig. 1

Description

Cross References to Related Applications

This application claims the priority of Swiss patent application 00560/13, filed 7 March 2013, the disclosure of which is incorporated herein by reference in its entirety. ·

Technical Field

The invention relates to an oven, in particular a baking oven for household applications.

Background Art CH 704 191 describes an oven appliance with a hot air generator, a microwave heater and a steam generator. Further, a climate sensor comprising an opening in the cooking chamber and a temperature sensor outside the opening is provided. When the temperature at the temperature sensor exceeds a given threshold, the feeding of hot steam and the heating with microwaves are reduced, while the hot air generator continues to operate normally.

Disclosure of the Invention

The problem to be solved by the present invention is to provide an oven of the type described above, which has a simple design and still is able to prepare foodstuff with low energy consumption.

According to the invention there is provided an oven comprising a cooking chamber, a heating arrangement comprising a hot air heater and/or a top and bottom heater, a first temperature sensor for measuring a temperature in the cooking chamber, a feedback loop for setting a heating power of the heating arrangement in order to maintain the temperature in the cooking chamber at a desired temperature, and a climate sensor comprising a first opening in the cooking chamber and a second temperature sensor arranged outside the first opening, wherein the oven comprises a thermostat comprising the second temperature sensor and adapted and structured to automatically set the heating power of the heating arrangement to a value below the value given by the feedback loop if the temperature at the second temperature sensor exceeds a threshold temperature, such that the temperature in the cooking chamber falls below the desired temperature.

The signal of the climate sensor can be used in simple manner for controlling the device. When the temperature at the second temperature sensor rises above the threshold temperature, it must be assumed that a comparatively large amount of steam escapes from the foodstuff. In order to avoid an unnecessary loss of energy in this case, the heating power of the heating arrangement is reduced, advantageously until the temperature at the second temperature sensor falls back. In this manner, the foodstuff can be kept cooking or simmering with a small amount of energy.

In a particularly simple implementation, the thermostat comprises a switch adapted to interrupt the current from the feedback loop to the heating arrangement until the temperature at the second temperature sensor falls back below the threshold temperature.

Brief Description of the Drawing

The invention will be better understood and objects other than those set forth above will become apparent when consideration is given to the following detailed description thereof. Such description makes reference to the annexed drawing, which shows a simplified sectional view of a baking oven.

Modes for Carrying Out the Invention Overview :

Fig. 1 shows a sectional view of a baking oven, in particular a household baking oven. The device comprises an enclosure 1, which encloses a cooking chamber 2. Cooking chamber 2 receives the foodstuff to be processed. Enclosure 1 is arranged in a housing 35. At its front side, cooking chamber 2 is closed by a door 3, through which the user can gain access to the cooking chamber. A heating arrangement with resistive heating elements is provided for heating cooking chamber 2. In the present embodiment, the heating arrangement comprises a top and bottom heater 4a, 4b, located at the ceiling and the floor of the cooking chamber, respectively, as well as a hot air heater 5. Hot air heater 5 is arranged in a heating chamber 6 at the backside of cooking chamber 2 and comprises a fan 7, which is designed as a radially blowing fan, as well as a resistive heater element designed as a heating coil 8. Openings 10a, 10b are arranged in a wall that separates cooking chamber 2 from heating chamber 6. Fan 7 is adapted to suck air from cooking chamber 2 through the openings 10a and feed it to heating coil 8, where it is heated. The heated air is fed through the openings 10b back into heating chamber 2. The openings 10b are arranged radially outside fan 7. A first temperature sensor 12 is arranged in or at heating chamber 2 and measures the temperature in the heating chamber 2. It is connected to a feedback loop 14, which forms part of the electronic and/or mechanical control unit 15 of the device. Feedback loop 14 is adapted to maintain the temperature within cooking chamber 2 at a desired value by controlling the heating power of hot air heater 5. Depending on a user-selected device program, feedback loop 14 can also control the heating power of top heater 4a and bottom heater 4b. A first opening 16 and a second opening 17 are arranged in the walls of cooking chamber 2. First opening 16, which is - in the present embodiment - located in a side wall of cooking chamber 2, forms part of a climate sensor 18, which will be described in more detail below. Second opening 17, which is - in the present embodiment - located at the ceiling of cooking chamber 2, is used to remove air from the cooking chamber 2 in certain operating programs.

Second opening 17 can be closed by means of a closing mechanism 19 controlled by control unit 15. Closing mechanism 19 can comprise a door 20, such as a pivoting door or a sliding door, which is operated by a drive 21 for covering/uncovering second opening 17. A small passage 20a, e.g. with a diameter of 8 mm, is arranged in door 20, such that second opening 17 is not fully blocked even if door 20 is closed, thereby guaranteeing that the underpressure in cooking chamber 2, as described below, can be maintained as long as the foodstuff is not outgas-sing. A channel 22 for carrying off air is located above enclosure 1. Channel 22 has an exit opening 23, e.g. at the front side of the device, where it communicates with the environment. A blower 24 is located in channel 22. In the present embodiment, blower 24 is a radial fan with two chamber 24a, 24b. Bottom chamber 24a sucks in air from cooking chamber 2 (through passage 20a if closing mechanism 19 is closed). Upper chamber 24b sucks in air from a space 37, through an opening 36.

Space 37 is located between enclosure 1 and housing 35, and blower 36 generates a cooling air stream therein, in order to cool the walls of housing 35.

Blower 24 is dimensioned such that - without any potentially outgassing foodstuff in cooking chamber 2 - the pressure pi in cooking chamber 2 is lower than the pressure p2 in space 37, even if door 20 is in its closed position.

Climate sensor 18 comprises a duct 26, which connects first opening 16 to space 37. A second temperature sensor 27 is arranged in or at duct 26 in order to measure the temperature at a location along duct 26.

Second temperature sensor 27 is part of a thermostat. By means of this thermostat, the heating power of the heating arrangement can be lowered below the value given by the feedback loop 14 if the temperature at the second temperature sensor 27 exceeds a threshold temperature Ts. In the shown embodiment, this thermostat comprises a switch 28, which is interrupted as soon as the temperature at the second temperature sensor 27 is above the given threshold temperature Ts.

The threshold temperature Ts is advantageously in a range between 60°C and 90°C, in particular between 65°C and 75°C, such that steam outgassing from the foodstuff can be detected and the heating power can be lowered early.

Switch 28 can also be implemented as part of feedback loop 14 or control unit 15, in which case second temperature sensor 27 is directly connected to feedback loop 14 or control unit 15.

The oven further comprises input controls 30, by means of which the user can select a operating program. Several such operating programs are provided, some of which are adapted to control the device in conventional manner.

Operation of the device:

At least one of the operating programs that can be selected by the user through the input controls 30 is a program for energy-efficient cooking under humid temperature. In the following, the steps executed by this program are described in more detail. These steps are controlled by control unit 15.

In a first step, cooking chamber 2 is heated by means of hot air heater 5 (and, possibly, with the help of the top and bottom heaters 4a, 4b), and the temperature. in cooking chamber 2 is then maintained at the desired temperature (which is e.g. specified by the user) by means of control loop 14.

During this program, door 20 at second opening 17 is kept at its closed position, or it can be can be opened after a certain time. Blower 24 is in operation.

The foodstuff in cooking chamber 2 heats up. Once steam starts to escape from the foodstuff, the pressure pi in cooking chamber 2 increases. When pressure pi rises above pressure p2 in space 37, hot, humid air starts two flow from cooking chamber 2 through duct 26, which causes the temperature at second temperature sensor 27 to raise above threshold temperature Ts. As soon and as long as this is the case, the supply of heating power to heating arrangement 5 is interrupted. Hence, the temperature in cooking chamber 2 starts to fall until the escape of steam from the foodstuff is so far reduced that the temperature at second temperature sensor 27 falls back below threshold temperature Ts, whereupon the temperature in cooking chamber 2 can again be maintained at the desired temperature by control loop 14.

In this manner the foodstuff can be kept cooking or simmering with a minimum amount of energy.

Notes:

Second temperature sensor 27 is locate at a duct that connects first opening 16 directly or indirectly with the environment.

In the embodiment of Fig. 1, duct 26 extends from first opening 16 to space 37, such that the temperature at the second temperature sensor 27 rises only when the pressure in cooking chamber 2 is higher than the pressure in space 37. Duct 26 may, however, also communicate with another part of the device or with the environment, in general with any location where the pressure during operation of the device (without outgassing foodstuff) is somewhat higher than the pressure in cooking chamber 2, in particular by an amount of at least 0.1 Pa, in particular by at least 3 Pa.

As mentioned, door 20 at second opening 17 is usually closed in the operating program described above, or it can be opened in time-controlled manner after a certain time. Such a time-controlled opening of door 20 allows to make sure that steam is carried off cooking chamber 2 in a case where the thermostat is not triggered correctly.

In the embodiment of Fig. 1, the supply of energy to heating arrangement 5 is interrupted completely when the temperature at the second temperature sensor 27 rises above the threshold temperature Ts. Alternatively, the energy supply can be reduced only, without being interrupted completely.

Further, control loop 14 can control the heating power of top heater 4a and/or bottom heater 4b, instead of, or in addition to, the heating power to hot air heater 5. In this case, the heating power of top . and/or bottom heater 4a, 4b is reduced when the temperature at second temperature sensor 27 rises above the threshold temperature Ts.

While there are shown and described presently preferred embodiments of the invention, it is to be distinctly understood that the invention is not limited . thereto but may be otherwise variously embodied and prac- ? ticed within the scope of the following claims. : reference in this specification to any prior ilication (or information derived from it), or to any ter which is known, is not, and should not be taken an acknowledgment or admission or any form of gestion that that prior publication (or information 'ived from it) or known matter forms part of the imon general knowledge in the field of endeavour to ch this specification relates. oughout this specification and the claims which low, unless the context requires otherwise, the d "comprise", and variations such as "comprises" . "comprising", will be understood to imply the lusion of a stated integer or step or group of egers or steps but not the exclusion of any other eger or step or group of integers or steps.

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. An oven comprising a cooking chamber, a heating arrangement comprising a hot air heater and/or a top and bottom heater, a first temperature sensor for measuring a temperature in the cooking chamber, a feedback loop for setting a heating power of the heating arrangement in order to maintain the temperature in the cooking chamber at a desired temperature, and a climate sensor comprising a first opening in the cooking chamber and a second temperature sensor arranged outside the first opening, wherein the oven comprises a thermostat comprising the second temperature sensor and adapted and structured to automatically set the heating power of the heating arrangement to a value below the value given by the feedback loop if the temperature at the second temperature sensor exceeds a threshold temperature, such that the temperature in the cooking chamber falls below the desired temperature .
2. The oven of claim 1 wherein the thermostat is adapted and structured to keep the heating power of the heating arrangement below the value given by the feedback loop as long as the temperature at the second temperature sensor is above the threshold temperature.
3. The oven of any one of the preceding claims further comprising: an enclosure enclosing the cooking chamber, a housing enclosing the enclosure, a space between the enclosure and the housing, a blower for sucking air from said cooking chamber and said space, wherein the blower is structured to generate, in the absence of foodstuff in the cooking chamber, a lower pressure in said cooking chamber than in said space, wherein the first opening is connected to said space by means of a duct, and wherein said second temperature sensor is arranged at said duct.
4. The oven of claim 3 further comprising: a control unit, a second opening, wherein the blower is arranged to suck air from the cooking chamber through said second opening, and a closing mechanism for partially closing and opening said second opening, wherein said closing mechanism is controlled by said control unit.
5. The oven of claim 4 wherein the blower is adapted to suck air from said cooking chamber also when said closing mechanism is in a closed state.
6. The oven of any of the claims 4 or 5, wherein the closing mechanism comprises a door, wherein the door comprises a passage such that the second opening is not fully closed even if said door is in a closed position.
7. The oven of claim 6 wherein said door is a pivoting or sliding door.
8. The oven of any one of the preceding claims wherein said thermostat comprises a switch that interrupts an electrical current from the feedback loop to the heating arrangement until the temperature at said second temperature sensor falls below said threshold temperature.
9. The oven of any one of the preceding claims wherein said threshold temperature is between 60°C and 90°C.
10. The oven of any one of the preceding claims wherein said threshold temperature is between 65°C and 75°C.
11. The oven of any one of the preceding claims wherein the heating arrangement comprises a hot air heater, wherein said hot air heater comprises a fan and a heater outside said cooking chamber, wherein said fan is adapted to suck air from said cooking chamber, feed said air to said heater and feed said air back to the cooking chamber. '