DE19509569A1 - Food heat treatment oven and baking process - Google Patents

Description

The invention relates to a furnace for the heat treatment of Food, with a housing inside 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 vent.

The invention further relates to a method for baking Food in which the food is in an oven with heat be charged.  

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

The known oven has a lockable by a door Cooking chamber, the upper end of which consists of a the entire width of the door is made of plastic, the one recessed grip and ventilation slots and one with the Has cooking chamber-related vapor extraction opening. To prevent condensation from escaping from the cooking space avoiding vapors on the front of the stove an opening in the door connects to the cooking space standing vase shaft, that of the vase the opening is vertically up to the door molding. An exhaust air fan can also be provided, to remove the vapor by means of at the upper end of the Support door bar of escaping blown air.

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

There is a muffle wall in the ceiling Vapor outlet opening at which a hose-like vapor channel is coupled, through which the vapors to the outside Blown air support flows into an exhaust duct.

It has been found to be disadvantageous in such furnaces that that especially in the treatment of frozen foods and in the case of baked goods, the formation of vapors shortly before the end of the baking time inside the oven is so strong that even a ven tilator-assisted vapor extraction cannot prevent that the food is adversely affected by the vapors or that baked goods do not get really crunchy in some cases.

The invention is therefore based on the object, remedy here to create and an oven as well as a method of baking create what even with strong vapors within the Oven ensures sufficient evacuation of the fumes is. In particular, it should be possible, even deep frozen baked goods with a high moisture content really crunchy to bake.

This task is carried out in a furnace of the type mentioned solved in that the cooking space has a supply air opening for air supply having.

In this way, the oven is not, as is conventional, operated in recirculation mode with vapor extraction, instead instead its in a "through-air mode" because of the blower the supply air opening air is sucked into the cooking space and the Vapors is extracted through the exhaust air opening. Thus arises a constant air flow through the cooking space, which frees up Vapors are effectively removed immediately. Let it this way yourself frozen foods and frozen foods Bakery products with a high moisture content without the adverse influence treat or bake the steam with heat. So you can for example, even deep-frozen baked goods with a very high level Moisture content can be baked crispy.

The object is further achieved by a method for baking Solved food, in which the food is in an oven be subjected to heat, initially with the fluid inside the furnace is circulated (recirculation mode), and before the end the baking time for fluid to be drawn through the oven is switched (through-air operation) to a constant change of the fluid inside the furnace.  

In this way, according to the invention, an energy saving is initially achieved of baking in air recirculation mode and only towards the end of Baking time rapid evacuation of the steam by switching ensures through-air operation, so crisp baked goods to produce in an energy-saving way.

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

This measure has the advantage that the fan at the same time used to extract vapors occurring in the door area becomes.

In a further embodiment of the invention, the blower is an exhaust fan located outside the cooking space, with which the exhaust port is connected to.

In this way, what is usually already in the oven is not Blower used for suction of the vapor, but for this special exhaust fan provided with which a special effective suction is possible.

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

In this way, the exhaust fan is not immediate acted upon by the hot fluid extracted from the cooking space, since the suction via an injector effect on the pressure side the exhaust fan.  

It is understood that instead of such an air duct Exhaust fan also with mixed air, warm air or fresh air can be acted upon, so that this is directly from the Vacuuming the cooking space, but this also a certain for cooling The proportion of cold air is mixed in to avoid overheating.

The exhaust fan can therefore operate at much lower temperatures are operated and designed to be significantly cheaper.

In an advantageous development of the invention, the intake comprises channel a suction funnel that is in the area of the upper end the door opens.

Thus, with the help of the blower support over the entire Door width an effective extraction of escaping vapors enables.

Rib-like can additionally be inside the intake duct Elements can be arranged to pass through the intake duct from the door to cool and condense sucked vapors.

In a further embodiment of the invention, the door has at least one entry opening in the lower area and min at least one outlet opening in the upper area near the Mouth of the intake duct, which via a connecting duct are connected in the door.

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

According to a further embodiment of the invention, the blower is outside the cooking space in a separate blower compartment ordered that on the suction side of the blower over at least  a suction opening is connected to the cooking chamber and on the pressure side of the blower via access openings with the Blower is connected to circulate the fluid within of the cooking space, and the pressure side of the Fan is connected to the exhaust air opening.

In this way, with the help of the known arrangement of a circulating fan in a convection oven that is already present Blowers used to effectively discharge the fumes in connection with the supply air opening. So leave the advantages according to the invention are particularly economical Achieve wise.

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

This creates the possibility of the flow rate of the fluid through the cooking space either manually or automatically depending on the amount of vapors or after a predetermined Program control. This is a particularly energy-saving one Operation of the furnace enables.

For this purpose, in an advantageous development of the invention Control device for opening and closing the supply air opening according to a certain program or depending on one Sensor signal provided.

In this way, an automatic operation of the furnace is on enables the most energy-saving possible.

It goes without saying that the exhaust air opening can also be closed can be trained. It can be in the locking device advantageously a pressure relief valve may be integrated, though  of course also a separate arrangement of a pressure relief valve is possible.

In an additional development of this version, the Control device a time-controlled opening and closing after a selectable program for certain foods. Here the supply air and extract air openings can be separated or controlled synchronously.

This measure has the advantage that it is particularly economical How a program-controlled operation of the furnace is made possible.

In an additional development of this version, the Time control for baked goods at the end of the baking time Opening the supply air opening.

According to this feature of the invention, one for baked goods Typical baking process allows to save energy crisp baked goods, such as rolls, pretzels and the like. Generate to can.

In a further development of the invention is a catalyst intended for cleaning the exhaust air.

Since, according to the invention, vapors which are formed anyway are produced using the Fan support is effectively removed so that strong vapors can be expected from time to time so an effective cleaning of the exhaust air enables, so that practically no environmental pollution occurs.

In an additional development of this version is the Kataly sator arranged outside the furnace and with a heater tion combined.  

In this way, the catalyst can be used on existing furnaces can be retrofitted without having to convert the furnace must be made. Through the heating device a high efficiency of the catalyst ensured.

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

Although with a catalytic converter an optimal cleaning of the exhaust air is often a catalyst in smaller furnaces too complex or too expensive, so that with the help of an exhaust air filter at least a partial reduction in odor nuisance is achieved in a cost-effective manner. It is understood that the exhaust air filter, of course, in addition to a catalytic converter can be used, for example, fat components or the like.

According to a further embodiment of the invention, in addition or alternatively a supply air filter can be provided. It can a pressure sensor may be provided to decrease pressure used filter to show a change in time is carried out.

It is further understood that the above and the Features of the invention not yet to be explained below only in the specified combination, but also in Can be used alone or in any other combination without leaving the scope of the invention.

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

Figure 1 shows a cross section of a first embodiment of an oven according to the invention in a highly simplified, schematic representation.

FIG. 2 shows a section through the furnace according to FIG. 1 along the line II-II;

Fig. 3 is a cross sectional view of a comparison with the embodiment of Figure 1 slightly modified furnace.

Fig. 4 shows a section of the furnace of FIG. 3 along the line IV-IV and

Fig. 5 shows a cross section of another furnace according to the invention.

In Figs. 1 and 2 a first embodiment of to the invention OF INVENTION furnace generally indicated by reference numeral 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 stainless steel-lined cooking space 14 , a floor drain 66 is provided, which is closed to a drain. Heating elements 26 are provided on the top and on the bottom for heating the cooking chamber 14 . Furthermore, there is a blower chamber 30 behind the rear wall of the cooking chamber 14 , within which a blower 32 driven by a motor 34 is provided, which sucks openings 36 through the axial suction on the rear wall of the cooking chamber 14 and that via lateral access openings 38 at the edges of the Rear wall is connected to the cooking chamber 14 . 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 Steuerein device 58 can also control the fan 32 and other controls, 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, an opening of the supply air opening 42 is also preferably effected after a corresponding warming-up time in order to enable effective evacuation of the vapors produced 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 amount and condition of the food 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 fully 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 on 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, there is cooling of the door 16 when the supply air opening 42 is open, since part of the effect of the blower 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.

The embodiment according to FIGS. 3 and 4 differs from the previously described embodiment essentially in that an exhaust fan 80 is provided in the upper rear end of the housing 12 in addition to the blower 32, which is supplied through a divided flow of air from the intake passage 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 chamber 14 , a separating 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 into a first one, which slits from the air 48 according to arrow 72 to the intake opening of the Exhaust fan 80 runs, and in a second, 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 .

As a result of the effect of the exhaust air 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 channel 18 of the door 16 even when the supply air opening 42 is closed. Thus, even when the supply air opening 42 is closed, a suction in the area of the door is ensured, so that steam or vapors escaping effectively when the door is opened is 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 thus 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 which run 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 with corresponding Reference numbers marked.

The furnace of FIG. 5 differs from the previously beschrie surrounded embodiment essentially in that the catalyst and the exhaust fan are not integrated in the furnace, but are arranged outside on the back 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)

1. Oven for heat treatment of food, 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 an air supply opening ( 42 ) for supplying air. 2. 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 ). 3. Oven according to claim 1 or 2, characterized in that the fan is an outside of the cooking space ( 14 ) arranged exhaust fan ( 80 ) with which the exhaust opening ( 44 ) is connected. 4. Oven according to claim 3, characterized in that the suction side of the exhaust fan ( 80 ) is connected to an intake duct ( 13 ) which opens in the region of the upper end of the door ( 16 ), and that the pressure side ( 84 ) of the exhaust fan ( 80 ) is connected to the exhaust air opening ( 44 ). 5. 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 ). 6. Oven according to one or more of claims 2 to 5, characterized in that the door ( 16 ) 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 ) near the Has mouth ( 48 ) of the intake duct ( 13 ), which are connected via a connecting channel ( 18 ). 7. Furnace according to one or more of claims 2 to 6, characterized in that rib-like elements ( 47 ) are provided for cooling and condensation of the fumes sucked in within the intake duct ( 13 ). 8. Oven according to one or more of the preceding claims, characterized in that the blower ( 32 ) outside the cooking chamber ( 14 ) is arranged in a separate blower chamber ( 30 ) which on the suction side of the blower ( 32 ) via at least one suction opening ( 36) is connected to the cooking chamber (14) and which is connected on the pressure side of the blower (32) via inlet openings (38) to the fan (32) to a circulation of the fluid to allow inside the cooking chamber (14), and that the pressure side of the blower ( 32 ) is connected to the exhaust air opening ( 44 ). 9. Oven according to one or more of the preceding claims, characterized in that the supply air opening ( 42 ) is at least partially closable. 10. Oven according to one or more of the preceding claims, characterized in that the exhaust air opening ( 44 ) is closable. 11. 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. 12. 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. 13. Oven according to claim 12, characterized in that the control device ( 58 ) allows a time-controlled opening and closing according to a preselectable program for certain foods. 14. Oven according to claim 13, characterized in that the time control for baked goods causes an opening of the supply air opening ( 42 ) towards the end of the baking time. 15. 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. 16. Oven 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 ). 17. Furnace according to one or more of claims 3 to 16, characterized in that the exhaust fan ( 110 ) outside the housing ( 12 ) of the furnace ( 100 ) is arranged and connected to the catalyst ( 104 ). 18. Oven according to one or more of the preceding claims, characterized in that an exhaust air filter ( 68 ) is provided. 19. Oven according to one or more of the preceding claims, characterized in that a supply air filter ( 48 ) is provided. 20. 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. 21. A method for baking food, in which the food is 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 a suction of fluid through the furnace is switched over (through-air operation) in order to bring about a constant change of the fluid within the furnace.