DK1619443T3 - Cooking appliance with controllable ventilation - Google Patents

Description

The invention relates to a cooking device according to the preamble of claim 1. Such an oven is described in EP 319 673.

An oven is known from EP 1 156 282, the cooking space of which has two openings. A sensor for detecting steam is arranged at one of these openings. The second opening is arranged at a fan. If escaping steam is detected by the sensor, the fan is switched on or operated with higher power in order to evacuate the steam exiting the second opening. It is also proposed to arrange a controllable slider at the second opening.

The objective is to reduce the energy consumption of this device.

This objective is reached with the cooking device according to claim 1.

According to the claim the cooking device is formed in such a way that the fan in the subsequent pressure space generates an overpressure, wherein the pressure space has an outlet opening for releasing air transported by the fan to the environment and tapers towards the outlet opening. The first opening opens into this pressure space. This leads to the necessity that the steam has to overcome the overpressure in the pressure space while exiting the first opening. Thus, the sensor detects a steam escape at the first opening only when a certain overpressure is present inside the cooking space. This is the reason why the sensor is only activated if a really excessive amount of steam is generated inside the cooking space. It has been noted that the energy loss can be reduced by this measure without an inadmissible increase of humidity in the cooking space.

Preferably, the second opening opens into the sucking area of the fan, such that the steam is efficiently evacuated when the closure is opened.

Further preferred embodiments result from the dependent claims as well as from the now following description based on the drawings. Therefore it is shown in:

Fig. 1 a schematic view of the most important components of a cooking device and

Fig. 2 an example of possible temperature courses inside the cooking space and at the temperature sensor (upper diagram) and the position of the closure of the second opening (lower diagram).

The cooking device according to Fig. 1 has a cooking space 1 which is delimited by walls 2 and a door 3. The cooking device shown as an example may be operated as oven or as steam cooking device. Accordingly, it has a steam generator 4 in addition to a conventional resistive heating (not shown), as described e.g. in EP 1 166 694. A radial flow fan 6 is arranged as blower outside the cooking space 1. It conveys air from a sucking area 7 into a pressure space 8. The air escapes from the pressure space 8 into the environment through a frontal outlet opening 9 of the device. The pressure space 8 is limited towards the top by an inclined covering plate 10 and towards the bottom by an inclined bottom plate 11, in such a way that the pressure space 8 tapers towards the outlet opening 9. To the sides, the pressure space is closed by lateral walls (not shown).

Two openings are arranged in the cover of the cooking space 1, having approximately the same size and having e.g. a diameter of about 2.5 cm each. A first opening 14 leads from the pressure space 1 into the interior 15 of a protecting casing 16. The protecting casing 16 is arranged inside the pressure space 8 and communicates with it via a connecting opening 17. The connecting opening 17 is arranged on the side of the protecting case 16 which is opposed to the blower. Furthermore, a temperature sensor 18 is arranged inside the protecting casing 16 at the exit of the first opening 14. The first opening 14 is always opened. A second opening 20 connects the cooking space 1 with the sucking area 7 before the blower 6. A seal 21 is provided for closing the second opening 20, consisting of a flap 22 which can be pushed to a greater or smaller extent over the exit of the opening 20 by a step motor or a servo motor 23, in such a way that the seal can be transferred substantially continually from a closed into an opened position. A controller 24 is provided for controlling the steam generator 4, the seal 21 and the further components of the cooking device, which amongst others monitors the temperature signal issued by the temperature sensor 18.

During operation of the cooking device the blower G is always in operation. It sucks air from the environment through openings in the back wall and in the side walls of the cooking device. This air passes the sucking area 7, is blown into the pressure space 8 and escapes from it through the outlet opening 9. Because the pressure space 8 tapers towards the outlet opening 9, a slight overpressure is created inside the pressure space 8.

In this way a task of the blower 6 is to guide air which heated up outside the cooking space to the outside, in order to cool the device.

The function of the cooking device depends on its use either as steam cooking device or as conventional thermal oven.

In conventional operation, the food to be cooked or the cooking space 1, respectively, is heated up by the not shown resistive heaters. The cooking space temperature Tgr may thereby increase above 100 °C, as shown in Fig. 2.

The seal 21 is in the closed position at the beginning of a conventional cooking phase, as illustrated in Fig. 2, because the controller 24 is adapted to keep the temperature at the temperature sensor 18 at a predetermined value Tr of e.g. 63 °C.

If the temperature Tgr of the cooking space increases above 100 °C, a more or less strong steam exit from the food is the result. In this way the pressure in the cooking space 1 increases. If this pressure increases above the pressure in the pressure space 8, the steam enters the interior 15 of the protecting case 16 via the first opening 14 and consequently the pressure space 8. During this process it passes the temperature sensor 18, such that the temperature Ts measured by it increases.

If the temperature Ts approaches the value Tr or exceeds it, the controller 24 starts opening the second opening 20 by actuating the step motor 23. In this way the cooking space 1 is connected to the sucking area 7, which has a relatively low pressure, via the second opening 20, such that the steam is evacuated through the opening 20 and the overpressure in the cooking space 1 is released. In this way the pressure gradient between pressure space 8 and cooking space 1 is reversed and only cooler and drier air travels from the pressure space 8 into the cooking space, with the consequence that the temperature sensor 3 cools down, such that the controller 24 closes again the seal 21.

Thus, the controller 24 forms a regulatory circuit trying to keep the temperature Ts at the sensor 18 as much as possible at the value Tr by opening the seal 21 to a greater or lesser extent.

If the steam generation rate in the cooking space 1 exceeds a certain value, e.g. during cooking of relatively large, humid food, the seal 21 remains entirely opened (as shown in Fig. 2) and the temperature Ts at the sensor 18 exceeds the value Tr significantly, until the steam generation rate decreases again.

If the temperature at the temperature sensor 18 remains low and therefore no steam exit is noticed anymore, the controller 24 closes the seal 21 preferably entirely, such that no more steam can escape and an unnecessary energy loos is avoided.

In this way steam is evacuated from the cooking space 1 needs-based. At the same time the blower 6 may however be kept in operation continuously and independently from the temperature value Ts of the sensor and may thereby cool the cooking device. A separate blower for sucking out excess steam from the cooking space 1 is not necessary, a radial flow fan is sufficient.

The seal 21 remains normally closed in operation as steam cooking device. However, the controller monitors the temperature Ts at the sensor 18 and uses it for controlling the power of the steam generator 4 in the way described in EP 1 166 694.

Optionally, at the end of the steam operation the seal 21 may be opened and in this way the steam may be evacuated from the cooking space 1. At the same time drier air is inserted into the cooking space 1 via the first opening 14.

In this way it is possible to use the opening 14 and the temperature sensor 18 for controlling the device in both operating modes.

The protecting casing 16 shields the temperature sensor 18 from the air coming from the blower 6, such that the temperature sensor 18 is able to detect even small guantities of escaping steam.

When the door 3 is closed, the cooking space 1 is gastight except for the first and the second opening. In steam cooking operation it is avoided by this measure that steam escapes the cooking space in an uncontrolled way and may consequently cause e.g. humidity damages. In the conventional oven operation mode the air exchange with the environment occurs in a controlled way via the openings 14 and 20.

As mentioned, the temperature Tr may have a fixed, predefined value. It may however also be chosen depending on the temperature in the cooking space 1. In this way it is possible to take into account that the steam exiting the hot cooking space has a higher temperature, thus enabling a more precise detection of the steam and therefore making possible a better regulation of the device.

Depending on the food to be cooked it may also be useful to control the seal 21 independent of the signal of the sensor 18. For example, the seal 21 may be kept continuously partially or entirely opened in a program phase, independently of the temperature at the sensor 18, in case of products from which very much humidity has to be withdrawn. For this purpose the cooking device may be formed in such a way that it keeps opened the seal 21 during at least a part of the program, independently of the sensor 18, when a special cooking program is chosen.

Instead of a temperature sensor another suitable sensor may be used as sensor for detecting the steam exiting the first opening 14, as described in EP 1 156 282.

Claims (14)

A cooking apparatus with a cooking space (1), a blower (6) for transporting gas from an intake area (7) outside the cooking space (1) to a pressure room (8) outside the cooking space (1), a first opening (14) in the cooking chamber (1), a sensor (18) for detecting steam coming out of the first opening (14), a second opening (20) in the cooking space (1) spaced from the first opening (14) ), and a closure device (21) for closing the second opening (20), the fan (6) being designed to produce an overpressure in the pressure chamber (8), characterized in that the first opening (14) opens into the pressure space (8), wherein the pressure chamber (8) has an outlet opening (9) for delivering air conveyed via the fan (6) to the surroundings and narrows in the direction towards the outlet opening (9), and the boiler has a closing device control (24) for controlling the closing device (21) depending on a signal from the sensor (18). Cooker according to claim 1, characterized in that the second opening (20) opens into the suction area (7). Cooker according to one of the preceding claims, characterized in that a protective housing (16) is arranged in the pressure chamber (8), the first opening (14) opening into an interior space (15) of the protective housing (16), the sensor (18) is disposed in the interior space (15) and the interior space (15) is in communication with the pressure space (8), and in particular that the interior space (15) is in communication with the pressure space (8) via a connection opening. (17) disposed on one side of the protective housing (16), which side faces away from the fan (6). Cooker according to one of the preceding claims, characterized in that the sensor (18) is a temperature sensor located at the mouth of the first opening (14). Cooker according to one of the preceding claims, characterized in that the closing device control (24) is designed as a control circuit which, when opening and closing the closing device (21), attempts to control a temperature (Ts) at the sensor (18) to a setting temperature ( Tr). Cooker according to one of the preceding claims, characterized in that when the closing device control (24), when it is detected that steam is escaping through the first opening (14), the closing device (21) opens more and more, and in particular that it closes the closing device when it can be detected that no steam is coming out. Cooker according to one of the preceding claims, characterized in that the fan (6) is a cross-flow fan. Cooking apparatus according to one of the preceding claims, characterized in that it is designed in such a way that the fan (6) conducts air which has been heated on the outside of the cooking space (1) for cooling apparatus. Cooker according to one of the preceding claims, characterized in that the fan (6) is operated substantially independently of the signal of the sensor (18). Cooker according to one of the preceding claims, characterized in that it is designed as a combined thermal baking oven and as a steam cooker and, in addition to at least one resistive heating device for the cooking space (1), has a steam generator (4) for introducing steam into the cooking space (1). ) and that it is designed to control a quantity of steam produced by the steam generator (4), depending on a signal from the sensor (18) when operating as a steam cooker. Cooking apparatus according to claim 10, characterized in that it is designed to open the closing device (21) at the end of a steam boiling operation in order to discharge steam from the cooking space (1). Cooker according to one of the preceding claims, characterized in that the cooking space (1) is gas-tight except for the first and second openings (14, 20). Cooker according to one of the preceding claims, characterized in that the closing device (21) can be transferred substantially continuously from a closed position to an opened position. Cooker according to one of the preceding claims, characterized in that it is designed in such a way that, during at least part of a cooking program, it keeps the closing device (21) at least partially open independently of the sensor (18).