EP0732549A2 - Oven for the heat treatment of food and method of baking - Google Patents

Abstract

The oven has a chamber (14) with an air intake (42). This is connected to an intake channel (13), which opens near the top end of the oven door (16). The oven also has an external exhaust ventilator, connected to an exhaust air aperture (44). The intake side of the ventilator is connected to the intake channel, while its pressure side is connected to the exhaust air aperture. The oven door has at least one lower intake aperture (20), and an upper discharge aperture near the top of the door and the opening (48) of the intake channel. The two apertures are connected via a channel (18).

Description

The invention relates to an oven for the heat treatment of food, with a housing within which a cooking space is provided, which can be closed by means of a door, with a heating device for heating the cooking space, with a blower, and with an exhaust air opening.

The invention further relates to a method for baking food, in which the food is subjected to heat in an oven.

A furnace of the type mentioned is known from DE-32 46 333 A1.

The known oven has a cooking chamber which can be closed by a door, the upper end of which consists of a strip of plastic which extends over the entire door width and which has a recessed grip and ventilation slots and a vapor discharge opening connected to the cooking chamber. In order to prevent condensation of the vapors emerging from the cooking space on the front parts of the oven, a vapors shaft is connected to the cooking space via an opening, which is led vertically from the vapors inlet opening up to the door strip. In addition, an exhaust air fan can be provided in order to support the removal of the vapor by means of blown air escaping at the upper end of the door strip.

A furnace of a similar design is known from DE 33 38 094 A1.

Here there is a vapor outlet opening in the ceiling-side muffle wall, to which a hose-like vapor channel is coupled, through which the vapor flows outwards into an exhaust duct with the aid of blown air support.

A disadvantage of such ovens has been found that, especially in the treatment of frozen foods and baked goods shortly before the end of the baking time, the formation of vapors within the oven is so strong that even a fan-assisted fume extraction system cannot prevent the foods from being released by the vapors are adversely affected or that baked goods are not properly crunched in some cases.

The invention is therefore based on the object to remedy this situation and to provide an oven and a method for baking, with which sufficient evacuation of the vapors is ensured even in the event of strong vapor formation within the oven. In particular, it should be possible to bake even deep-frozen baked goods with a high moisture content.

This object is achieved in an oven of the type mentioned above in that the cooking chamber has an inlet air opening for air supply.

In this way, the oven is not operated in the recirculation mode with vapor extraction, as is conventional, but instead in a "through-air mode", since air is sucked into the cooking space through the supply air opening and the vapors are extracted through the exhaust air opening. This creates a constant flow of air through the cooking chamber, which immediately releases any vapors that are released. In this way, even deep-frozen foods and deep-frozen baked goods with a high moisture content can be heat treated or baked without the disadvantageous influence of the vaping. This means, for example, that even deep-frozen baked goods with a very high moisture content can be baked crispy.

The object is further achieved by a method for baking foodstuffs, in which the foodstuffs are subjected to heat in an oven, the fluid inside the oven first being circulated (recirculation mode), and before the end of the baking time the fluid is sucked through the furnace is switched over (through-air operation) in order to effect a constant change of the fluid within the furnace.

In this way, according to the invention, energy-saving baking is first made possible in recirculation mode, and only at the end of the baking time is the vaping rapidly carried out by switching to air-through mode, in order to produce crispy baked goods in an energy-saving manner.

In an advantageous development of the furnace according to the invention, the supply air opening is connected to an intake duct which opens in the region of the upper end of the door.

This measure has the advantage that the blower is simultaneously used to extract vapors occurring in the door area.

In a further embodiment of the invention, the fan is an exhaust air fan which is arranged outside the cooking space and to which the exhaust air opening is connected.

In this way, the fan, which is usually already in the oven anyway, is not used to extract the vapor, but instead a special exhaust air fan is provided, with which particularly effective extraction is made possible.

In an advantageous further development of this embodiment, the suction side of the exhaust air fan is connected to an intake duct which opens in the region of the upper end of the door, and the pressure side of the exhaust air fan is connected to the exhaust air opening.

In this way, the exhaust air fan is not acted upon directly by the hot fluid extracted from the cooking space, since the extraction takes place via an injector effect on the pressure side of the exhaust air fan.

It goes without saying that, instead of such an air duct, the exhaust air fan can also be acted on with mixed air, warm air or fresh air, so that it sucks directly out of the cooking chamber, but a certain proportion of cold air is additionally mixed in for cooling in order to avoid overheating.

The exhaust air fan can thus be operated at much lower temperatures and can be designed considerably more cost-effectively.

In an advantageous development of the invention, the intake duct comprises an intake funnel which opens into the area of the upper end of the door.

With the help of the fan support, effective evacuation of escaping vapors is made possible across the entire door width.

Rib-like elements can additionally be arranged within the intake duct in order to cool and condense vapors drawn in by the door via the intake duct.

In a further embodiment of the invention, the door has at least one inlet opening in the lower region and at least one outlet opening in the upper region in the vicinity of the mouth of the intake duct, which are connected via a connecting duct in the door.

In this way, air flows through the door, which results in advantageous cooling of the door.

According to a further embodiment of the invention, the blower is arranged outside the cooking space in a separate blower space, which at least on the suction side of the blower a suction opening is connected to the cooking space and is connected to the blower on the pressure side of the blower via access openings to allow circulation of the fluid within the cooking space, and the pressure side of the blower is connected to the exhaust air opening.

In this way, the already existing fan is used with the aid of the known arrangement of a circulating fan in a forced-air oven in order to achieve effective evacuation of the vapors in connection with the supply air opening. The advantages according to the invention can thus be achieved in a particularly cost-effective manner.

In a preferred development of the invention, the supply air opening is at least partially closable.

This creates the possibility of controlling the flow rate of the fluid through the cooking space either manually or automatically depending on the amount of vapor or according to a predetermined program. This enables a particularly energy-saving operation of the furnace.

To this end, in an advantageous development of the invention, a control device is provided for opening and closing the supply air opening according to a specific program or as a function of a sensor signal.

In this way, automatic operation of the furnace is made possible in the most energy-saving way possible.

It is understood that the exhaust air opening can also be designed to be closable. In this case, an overpressure valve can advantageously be integrated into the closing device, although a separate arrangement of a pressure relief valve is of course also possible.

In an additional development of this embodiment, the control device allows time-controlled opening and closing according to a preselectable program for certain foods. The supply air and extract air openings can be controlled separately or synchronously.

This measure has the advantage that program-controlled operation of the furnace is made possible in a particularly cost-effective manner.

In an additional development of this embodiment, the time control for baked goods causes the supply air opening to open at the end of the baking time.

According to this feature of the invention, a baking process that is typical of baked goods is thus made possible in order to save crisp baked goods such as rolls, pretzels and the like. To be able to produce.

In an additional development of the invention, a catalyst for cleaning the exhaust air is provided.

Since, according to the invention, vapors which are generated anyway are effectively removed with the aid of the blower support, so that a strong vapors discharge can be expected at times, an effective cleaning of the exhaust air is made possible, so that practically no environmental pollution occurs.

In an additional development of this embodiment, the catalytic converter is arranged outside the furnace and combined with a heating device.

In this way, the catalyst can be retrofitted to existing furnaces without the need to convert the furnace. The heating device ensures a high efficiency of the catalyst.

In an additional development of the invention, an exhaust air filter is provided.

Although an optimal cleaning of the exhaust air is made possible with a catalyst, a catalyst is often too complex or too expensive for smaller stoves, so that with the aid of an exhaust air filter at least a partial reduction of the odor nuisance is achieved in a cost-effective manner. It goes without saying that the exhaust air filter can of course also be used in addition to a catalytic converter, for example in order to collect fat components or the like.

According to a further embodiment of the invention, a supply air filter can additionally or alternatively be provided. A pressure sensor can be provided to indicate a pressure drop when the filter is used up, so that a change is carried out in good time.

It also goes without saying that the features of the invention mentioned above and those yet to be explained below can be used not only in the combination indicated in each case, but also alone or in another combination without departing from the scope of the invention.

Fig. 1

einen Querschnitt einer ersten Ausführung eines erfindungsgemäßen Ofens in stark vereinfachter, schematischer Darstellung;

Fig. 2

einen Schnitt durch den Ofen gemäß Fig. 1 längs der Linie II-II;

Fig. 3

einen Querschnitt eines gegenüber der Ausführung gemäß Fig. 1 leicht abgewandelten Ofens;

Fig. 4

einen Schnitt des Ofens gemäß Fig. 3 längs der Linie IV-IV und

Fig. 5

einen Querschnitt eines weiteren erfindungsgemäßen Ofens.

Further features and advantages of the invention result from the following description of preferred exemplary embodiments with reference to the drawing. Show it:

Fig. 1

a cross section of a first embodiment of an oven according to the invention in a highly simplified, schematic representation;

Fig. 2

a section through the furnace of Figure 1 along the line II-II.

Fig. 3

a cross section of a slightly modified furnace compared to the embodiment of FIG. 1;

Fig. 4

a section of the furnace of FIG. 3 along the line IV-IV and

Fig. 5

a cross section of another furnace according to the invention.

1 and 2, a first embodiment of an oven according to the invention is generally designated by the number 10. A cooking chamber 14 is arranged within a housing 12, the front of which can be closed by means of a door 16. At the bottom of the cooking chamber 14 lined with stainless steel, a floor drain 66 is provided, which is connected to a drain. Heating elements 26 are provided on the top and on the bottom for heating the cooking chamber 14. Furthermore, behind the rear wall of the cooking chamber 14 is a blower chamber 30, within which a fan 32 driven by a motor 34 is provided, which draws in through axial suction openings 36 on the rear wall of the cooking chamber 14 and which also has lateral access openings 38 on the edges of the rear wall the cooking chamber 14 is connected. Additional heating elements 28 in the form of heating coils run coaxially around the blower 32. With this arrangement, which is known per se, heating of the furnace 10 is made possible by means of top and bottom heat as well as by circulating air.

At the upper end of the blower chamber 30, an exhaust air opening 44 is provided, which is connected to a filter 68, the outlet opening of which is connected to an exhaust pipe 56.

At the upper end of the cooking space 14, a supply air opening 42 is also provided shortly in front of the rear wall and is connected to an intake duct 13 via an actuating device 50. The intake duct 13 comprises an intake funnel 46 (see FIG. 2), which opens out at the front end of the furnace above the door 16 via horizontally arranged air slots 48. Optionally, a supply air filter 69 can also be provided above the air slots 48, as is only indicated schematically in FIG. 1.

Both filters 68, 69 can be monitored by means of pressure sensors in order to indicate a pressure drop when the filter is used up, so that a filter change is carried out in good time.

The door 16 is sealed against the front of the cooking chamber 14 by a circumferential seal 24 and has air inlet openings 20 in the form of slots at the lower end below the seal 24, and in a corresponding manner at the upper end above the seal 24 air outlet openings 22 Inside the door 16, the inlet openings 20 are connected to the outlet openings 22 via a connecting channel 18.

The structure of the actuating device 50 can be seen in more detail in FIG. 2. In the simplest case, the actuating device 50 comprises a flap 54 which can be opened and closed by means of an actuating motor 52 or can be pivoted into intermediate positions.

It is understood that numerous other designs of the actuating device 50 are available to the person skilled in the art.

A corresponding closing device 51 or actuating device with a flap 55, which is actuated via a servomotor 53, can be provided within the exhaust air opening 44.

To control the furnace 10, a control device 58 is provided, which preferably comprises a microprocessor control, from which the heating devices 26, 28 and the actuating devices 50 and 51 are controlled, as indicated by control lines 60, 61, 62, 64. It is understood that the control device 58 can also control the blower 32 and other control elements such as sensors and. Like. Can include. It is further understood that the control device 58 can be operated from the front of the furnace 10 via a corresponding input and control unit.

The control device 58 now has a series of preselectable programs for the heat treatment of different foods, via which a desired cooking or baking process can be set for different foods. In this case, the temperature inside the cooking chamber 14 is preferably controlled in a suitable manner and the actuating device 50 is additionally actuated in a suitable manner in order to open completely or, if there is a large amount of vapors, or partially, if the volume of vapors is less to reach the supply air opening 42.

For example, in baked goods such as pretzels, rolls and. To enable a crisp baking method, the supply air opening 42 is only opened in the last minutes before the end of the baking time, while the rest remains closed to enable energy-saving operation. If deep-frozen goods are used, the supply air opening is preferably opened after a corresponding warming-up time 42 acts to enable effective evacuation of the vapors generated during thawing. In addition, numerous program sequences for opening the supply air opening 42 over time are conceivable, depending on the desired heat treatment process and on the quantity and condition of the foodstuffs to be treated. It also goes without saying that the supply air opening 42 can also be opened and closed with the aid of a sensor, for which purpose a temperature sensor or a humidity sensor can be used, for example.

When the supply air opening 42 is completely or partially open, the action of the fan 32 results in an air flow according to the arrows 70 through the door 18 and according to the arrows 72, 74, 76, 78 through the intake duct 13, the supply air opening 42, the intake openings 36 at the Rear wall of the cooking chamber 14, and through the exhaust air opening 44 and through the filter 68, until the extracted fluid finally exits via an exhaust pipe 56 at the upper end of the oven 10, which is optionally connected to an exhaust air duct.

When the supply air opening 42 is closed, there is essentially a recirculation mode, with only small amounts escaping upwards through the exhaust air opening 44 when there is a strong development of vapors within the cooking space 14. On the other hand, when the supply air opening 42 is opened, there is an effective extraction of vapors generated in the cooking space, since the fluid is constantly exchanged due to the low flow resistance of the supply air opening 42 and the exhaust air opening 44.

In addition, the door 16 is cooled when the supply air opening 42 is open, since part of the effect of the fan 32 is used to generate an upward air flow through the door 16.

In the embodiment according to FIGS. 3 and 4, parts corresponding to the embodiment described above are identified with corresponding reference numerals.

3 and 4 differs from the previously described embodiment essentially in that, in addition to the blower 32, an exhaust fan 80 is provided in the upper rear end of the housing 12, which is supplied via a divided air flow from the intake duct 13 . The exhaust air fan 80 is connected on the suction side to the intake duct 13. The exhaust air fan 80 includes an outlet port 84 on the pressure side, which opens into the filter 68. A riser pipe 82 opens into the outlet connection 84, the lower end of which forms the exhaust air opening 44 at the upper end of the blower chamber 30. Above the supply air opening 42 in the cooking space 14, a partition plate 88 is provided within the intake duct 13, through which the air flow within the intake duct 13 is divided into two air flows, namely a first one, which extends from the air slots 48 according to arrow 72 to the intake opening of the exhaust air fan 80, and in a second one, which runs from the air slots 48 according to the arrow 74 through the supply air opening 42 into the cooking chamber 14. Again, the supply air opening 42 can be closed by a suitable actuating device 50 by means of a flap 54 which is driven by an actuating motor 52.

Thus, due to the action of the exhaust fan 80, there is a constant air flow through the air slots 48 and the intake duct 13. This ensures a constant air flow through the air slots 48 and also through the connecting duct 18 of the door 16 even when the supply air opening 42 is closed. Thus, even when the supply air opening 42 is closed, suction is ensured in the area of the door, so that steam or vapors escaping when the door is opened are effectively extracted.

When the supply air opening 42 is open, there is also an air flow through the cooking chamber 14 via the exhaust air opening 44 and the riser pipe 82 into the outlet connection 84, since the exhaust air fan 80 has an injector effect in the selected connection mode and therefore draws in via the riser pipe 82.

With this arrangement, the exhaust fan 80 is only exposed to significantly lower temperatures than the temperatures inside the cooking space (usually up to about 250 ° C.), so that a considerably more cost-effective design can be selected.

As can also be seen from FIG. 4, two catalytic converters 86 are additionally arranged within the blower chamber 30 and are designed as rectangular plates. The catalysts 86, which are thus arranged in the hottest zone of the furnace 10, enable effective exhaust air purification, so that odor nuisance is excluded.

In addition, as in the example shown, the filter 68 can be provided.

In the embodiment shown, the furnace 90 is heated exclusively with the aid of the heating elements 28 running concentrically around the fan 32. It goes without saying that further heating elements can of course be provided, for example such as the heating elements 26 according to the embodiment according to FIG. 1.

The exhaust air fan 80 is also controlled by the control device 58, as indicated by a control line 65.

A further embodiment of an oven according to the invention is shown in FIG. 5 and is designated overall by the number 100.

Here too, corresponding parts are identified with corresponding reference numerals.

5 differs from the previously described embodiment essentially in that the catalytic converter and the exhaust fan are not integrated in the furnace, but are arranged outside at the rear of the furnace and are combined into a separate unit. It is therefore a version that can be easily retrofitted.

The intake duct 13 is connected at its rear end via a vertically extending pipe 102 to a connecting piece 120 of an exhaust air fan 118, which opens into a catalyst body 108 on the pressure side. The catalyst body 108 has an electrical heater 110 and is accommodated together with this and with the exhaust air fan 118 by a common housing 106. A temperature sensor 112 is also provided within the catalyst body 108 in order to control the heater 110 in such a way that the catalyst body 108 is operated in an optimal temperature range, on the one hand to ensure sufficient effectiveness of the catalyst and on the other hand to keep the energy consumption as low as possible.

For this purpose, the exhaust air fan 118, the temperature sensor 112 and the heater 110 are connected to the control device 58 via corresponding control lines 116, 112 and 110.

Claims (21)

Oven for the heat treatment of foodstuffs, with a housing (12) within which a cooking space (14) is provided, which can be closed by means of a door (16), with a heating device (26, 28) for heating the cooking space, with a blower ( 32, 80, 118), and with an exhaust air opening (44), characterized in that the cooking space (14) has a supply air opening (42) for supplying air. Oven according to claim 1, characterized in that the supply air opening (42) is connected to an intake duct (13) which opens in the region of the upper end of the door (16). Oven according to claim 1 or 2, characterized in that the fan is an exhaust air fan (80) which is arranged outside the cooking chamber (14) and to which the exhaust air opening (44) is connected. Oven according to Claim 3, characterized in that the suction side of the exhaust air fan (80) is connected to an intake duct (13) which opens in the region of the upper end of the door (16), and in that the pressure side (84) of the exhaust air fan (80) is connected to the exhaust air opening (44). Oven according to claim 2, 3 or 4, characterized in that the intake duct (13) comprises an intake funnel (46) which opens in the region of the upper end of the door (16). Oven according to one or more of claims 2 to 5, characterized in that the door (16) has at least one inlet opening (20) in the lower region and at least one outlet opening (22) in the upper region of the door (16) in the vicinity of the mouth ( 48) of the intake duct (13), which are connected via a connecting duct (18). Oven according to one or more of claims 2 to 6, characterized in that rib-like elements (47) are provided within the suction duct (13) for cooling and condensing the fumes which are sucked in. Oven according to one or more of the preceding claims, characterized in that the blower (32) is arranged outside the cooking space (14) in a separate blower space (30) which is on the suction side of the blower (32) via at least one suction opening (36) is connected to the cooking space (14) and which is connected to the blower (32) on the pressure side of the blower (32) via access openings (38) in order to enable circulation of the fluid within the cooking space (14), and that the pressure side of the blower (32) is connected to the exhaust air opening (44). Oven according to one or more of the preceding claims, characterized in that the supply air opening (42) is at least partially closable. Oven according to one or more of the preceding claims, characterized in that the exhaust air opening (44) is closable. Oven according to claim 10, characterized in that the exhaust air opening has a closing device (51) which is combined with a pressure relief valve. Oven according to claim 9, 10 or 11, characterized in that a control device (58) for opening and closing the supply air opening (42) or exhaust air opening (44) is provided according to a specific program or as a function of a sensor signal. Oven according to claim 12, characterized in that the control device (58) permits time-controlled opening and closing according to a preselectable program for certain foods. Oven according to claim 13, characterized in that the time control for baked goods brings about an opening of the supply air opening (42) towards the end of the baking time. Oven according to one or more of claims 1 to 14, characterized in that a catalyst (86, 104) is provided for cleaning the exhaust air. Furnace according to claim 15, characterized in that the catalyst (104) is arranged outside the housing (12) of the furnace (100) and is combined with a heating device (110). Furnace according to one or more of claims 3 to 16, characterized in that the exhaust air fan (110) is arranged outside the housing (12) of the furnace (100) and is connected to the catalytic converter (104). Oven according to one or more of the preceding claims, characterized in that an exhaust air filter (68) is provided. Oven according to one or more of the preceding claims, characterized in that a supply air filter (48) is provided. Oven according to claim 18 or 19, characterized in that a pressure sensor is arranged after the filter (68, 69) to indicate a pressure drop when the filter (68, 69) is used up. Process for baking foodstuffs, in which the foodstuffs are subjected to heat in an oven, characterized in that first the fluid inside the oven (10, 90, 100) is circulated (recirculation mode) and that before the end of the baking time there is a suction of fluid is switched through the furnace (through-air operation) to effect a constant change of the fluid within the furnace.

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