Oven and method for operating an oven

Abstract

An oven (1) has at least one baking chamber (B1, B2) and a heat source (2) for heating the baking chamber (B1, B2). The heat source (2) has at least one electrical heating element (3 i ) and a power circuit (6 i ) for supplying current to the electric heating element (3 i ). A control device (7) is connected to the power circuit (6 i ) for variable setting of heating power in signal connection. The electric heating element (3 i ) is operated with the specified heating output.

Description

[0001] The invention relates to an oven having at least one baking chamber and a heat source for heating the baking chamber with at least one electric heating element. Furthermore, the invention relates to a method for operating such an oven.

[0002] An oven of the type mentioned above is known from DE 10 2020 211 020 A1 and from DE 10 2011 003 122 B4.

[0003] It is an object of the present invention to further develop an oven of the type mentioned at the outset in such a way that a standardized structure of the heat source is possible.

[0004] This object is achieved according to the invention by an oven having the features specified in claim 1.

[0005] According to the invention, it was recognized that by creating the possibility of a variable power setting via the control device and the power circuit, an oven can be equipped with electrical heating elements, each with the same nominal power. The actual specified heating power, which is usually less than the nominal power of the heating element, is then variably specified using the control device. This simplifies the construction of the oven and, in particular, the replacement of electrical heating elements during maintenance or repair. As long as the nominal power is higher than the heating power specified by the control device, a change in the nominal power of the heating element is irrelevant. If undesirable variations in the baking behavior of the oven occur, these can be compensated for by a correspondingly changed specification by the control device and, in turn, do not require the replacement of the respective heating element.

[0006] The electrical heating element may be a resistance heating element, particularly in the form of a heating rod.

[0007] A power specification by specifying a duty cycle according to claim 2 has proven to be particularly effective.

[0008] For the performance specification, the basically known variants - Control via a pulse-width modulated signal, - phase control, - Vibration package control, if necessary also in combination, can be used.

[0009] In a deck oven design according to claim 3, the advantages of variable power settings for the electric heating elements are particularly effective. Alternatively, the oven can also be designed with just one stovetop.

[0010] The power of the electrical heating elements can be specifically set so that the baking chambers can be operated differently or in the same way.

[0011] The advantages of variable power settings are particularly effective when the electric heating elements are configured as top and bottom heat heating elements according to claim 4. Depending on the requirements, top and bottom heat can be operated differently or simultaneously.

[0012] Several top heat heating elements according to claim 5 enable a targeted influence of a top heat baking chamber heating over an extension of the baking chamber.

[0013] The use of multiple bottom heat heating elements according to claim 6 offers corresponding advantages. By subdividing the top heat or bottom heat into multiple heating elements, the associated baking chamber can be divided into multiple baking chamber zones, with each baking chamber zone being assigned at least one of the heating elements, for example, at least one top heat heating element and / or at least one bottom heat heating element. A baking chamber zone-dependent baking temperature can then be specified via the control device, or the baking chamber temperature can be regulated depending on the baking chamber zone. Oven- or operational-related baking temperature differences between the baking zones can then be compensated.

[0014] A duty cycle specification of the duty cycle according to claim 7 has proven successful in practice. Such a specification can be achieved using pulse width modulation.

[0015] An alternative oven design has at least one temperature sensor per baking chamber. This allows at least one actual temperature value to be measured per baking chamber and compared with a target temperature value specified via a correspondingly adapted baking program. Depending on the deviation between the actual and target temperature values, the control unit, which then functions as a regulating device, can adjust the duty cycles of the respective electrical heating elements to specify the power output. This enables controlled oven temperature operation.

[0016] The advantages of an operating method according to claim 8 correspond to those already explained above with reference to the baking oven according to the invention. The at least two sets of power values ​​that are specified can differ in at least one power value or in a plurality of power values ​​or even in all power values. The respective set of power values ​​can be specified in particular as a set of duty cycles for the electrical heating elements. The power values ​​or duty cycles can be specified individually and in particular differently within a set. However, these power values ​​or duty cycles can also be the same, depending on the requirements of the baking program.Power values ​​or duty cycles of the various sets can be individually specified and, in particular, can be different, but can also be the same, depending on the requirements of the baking program.

[0017] A baking step specification according to claims 9 or 10 leads to particularly flexible baking parameters.

[0018] A baking step specification according to claim 11 takes into account that a baking chamber zone adjacent to a removal opening, for example, a baking chamber door, suffers increased losses. Corresponding losses are then compensated by specifying higher heating power values ​​for the heating elements adjacent to the removal opening.

[0019] A baking step specification according to claim 12 takes into account that the lowest baking chamber of a deck oven does not receive any waste heat from the baking chamber below it. This lowest baking chamber is then operated at a higher power level, i.e., higher heating output.

[0020] The performance value sets can also be specified in the form of a control system. For example, a target oven temperature is specified, which can also be specified for specific oven zones. These target values ​​can then be compared with actual temperatures using the oven's temperature sensors and taken into account in the operating procedure specifications through the corresponding performance value specifications in the sets.

[0021] An embodiment of the invention is explained in more detail below with reference to the drawing, in which: Fig. 1 schematically shows a vertical longitudinal section through an electrically heated deck oven; and Fig. 2 schematically shows a flow diagram of a method for operating the deck oven according to Fig. 1.

[0022] An oven 1 designed as an electrically heated deck oven has a plurality of hearths H1, H2, ..., of which Fig. 1, indicated by dashed borders, a bottom oven H1 and an oven H2 above it are illustrated. Each of the ovens H1, H2, ... has an associated baking chamber B1, B2, ...

[0023] Oven 1 can be an industrial oven or a shop oven.

[0024] The oven 1 has a heat source 2 for heating the baking chambers B1, B2, ... For each of the baking chambers B1, B2, ..., the heat source 2 comprises an identical arrangement of electrical heating elements 3 i , so that it is sufficient to describe the heating element arrangement of the baking chamber B1 below.

[0025] The electric heating elements 3i are designed as electrical resistance heating elements, namely as heating rods, which are Fig. 1 are shown in cross section.

[0026] The heating source 2 has a total of seven bottom heat heating elements 3 1 , 3 2 , ... 3 7 and a total of seven top heat heating elements 3 8 up to 3 14 . The bottom heat heating elements 3 1 up to 3 7 form a bottom heat heating device 4 of the heat source 2. The heating elements 3 8 up to 3 14 form a top heat heating device 5 of the heat source 2. The bottom heat heating device 4 and the top heat heating device 5 serve as bottom heat and top heat for the baking chamber B1.

[0027] To power the electrical heating elements 3 i of the respective baking chamber Bi is a power circuit 6 i . In the Fig. 1 illustrates the two power circuits 6 1 , 6 2which is connected in a manner not shown in detail to the electric heating element 3 i are in electrical power connection. The respective power circuit 6 i can be divided into a bottom heat and a top heat power circuit for the respective oven Hi or baking chamber Bi. The respective power circuit 6 i is designed so that each of the electrical heating elements 3 i can be powered independently and variably.

[0028] The oven 1 also has a control device 7, which can also be designed as a control / regulating device. The control device 7 is connected to the power circuits 6 i for variable specification of a duty cycle ED of the power circuits 6 i in signal connection. The duty cycle ED is a parameter that is assigned to each of the electrical heating elements 3 iis individually assigned. The duty cycle ED is a ratio of an operating time BD during which the electrical heating element 3 i is operated at its nominal power, for example with a power in the range between 200 W and 10 kW, in particular in the range between 200 W and 1 kW, and a predetermined useful life ND of the baking chamber Bi to which this electric heating element 3 i is assigned. Therefore: ED = BD / ND.

[0029] The duty cycle ED can thus be used to control the effective electrical power of the respective electrical heating element 3 i possible.

[0030] The respective duty cycle ED can be set via a duty cycle of a pulse control of the respective power circuit 6 i can be variably specified via the control device 7. The following then applies: ED = τ / T where; τ: pulse duration of the pulse control and T: Period of the pulse control.

[0031] All electrical heating elements 3 i of the oven 1 can have the same nominal power (rated power), for example 200 W, 300 W, 400 W or 500 W. The electrical heating elements 3 i can be designed identically.

[0032] When operating oven 1, a baking program is first selected depending on the type of baked goods to be baked in oven 1. This is done in a selection step A (see Fig. 2).

[0033] The following Table 1 shows an example of such a baking program for the baked good "Kaisersemmel." Each row of Table 1 describes a baking step with the associated temperature, duration in minutes, amount of steam that can be supplied to the respective baking chamber Bi via a steaming device 8, and the degree of opening in percent of each steam damper 9. ifor removing steam clouds from the assigned baking chamber Bii, for creating a humidity-reduced atmosphere in this baking chamber Bi

[0034] The last column of the baking program in Table 1 indicates which set of duty cycles for the respective heating elements 3 i is selected.

[0035] Example baking program - Kaisersemmel Table 1 Baking step temperature Duration steam swath damper set 1 230°C 5 2 liters 0% 001 2 235°C 8 0 0% 002 3 230°C 1 0 100% 001

[0036] The following Table 2 again gives an example of the duty cycles ED in percent for the electrical heating elements 3 i These operating times are tabulated first for the bottom heat heating elements 3 1 up to 3 7 of the cooker H1 (columns 1 to 7). The following row shows the corresponding operating times for the top heat heating elements 3 8 up to 3 14(again columns 1 to 7 of Table 2), again of the cooker Hi. The following are the operating times for the bottom heat elements 3 1 up to 3 7 of the cooker above H2 and then the operating times for the top heat heating elements 3 8 up to 3 14 of this overlying focus H2 (again columns 1 to 7).

[0037] Set No. 001 (Example of a set for an oven with 2 stoves) Table 2 1 2 3 4 5 6 7 HI UH 100% 90% 90% 80% 75% 80% 75% H1 OH 100% 95% 85% 85% 80% 80% 75% H2 UH 95% 90% 85% 75% 70% 75% 70% H2 OH 95% 90% 80% 80% 80% 75% 70%

[0038] For example, in this set number 001, the heating element 3 4 of the cooker H1 has a duty cycle of 80%, so that this heating element 3 4 i.e., it is operated at 80% of its nominal power. The top heat heating element 3 11of the cooker H1 has a duty cycle ED of 85% for set number 001. The set of duty cycles shown in Table 2 is an example of a set of power values ​​for the electric heating elements (3 i ).

[0039] The duty cycles are assigned in set number 001 so that those heating elements 3 1 , 3 8 the baking chamber doors 10 1 , 10 2 , ...of the baking chambers B1, B2 are closest, have a longer duty cycle than those further away from the baking chamber door 10 i , i.e. from the removal opening, arranged electrical heating elements 3 2 , 3 3 , ... or 3 9 , 3 10 , ...

[0040] In addition, in set number 001, the duty cycles of the electrical heating elements are assigned in such a way that duty cycles of the electrical heating elements 3 iof the lowest stove H1 tend to be larger than those of the electric heating elements 3 i of the stove H2 above. The electric heating element 3 1 For example, the cooker H1 has a duty cycle of 100% and the electric heating element 3 1 The H2 stove has a lower duty cycle of 95% in comparison.

[0041] This set number 001 is calibrated so that when this set number 001 is used in the baking chambers B1 and B2 the desired temperature of 230 degrees C is set evenly across the entire depth of the baking chambers B1, B2.

[0042] The first baking step of the baking program is now specified according to Table 1. This is done in a preset step V1. Set number 001 is used for this first baking step according to Table 2, as explained above.

[0043] Now the second baking step of the baking program is specified according to Table 1. This is done in a further specification step V2. This is done, among other things, using the schematic flow diagram of the Fig. 2.

[0044] In this baking step 2, another set number 002 comes from the electric heating elements 3 according to the table 3 below i assigned duty cycles ED, which differs from set number 001 according to Table 2.

[0045] Set No. 002 Table 3 1 2 3 4 5 6 7 HI UH 95% 85% 85% 75% 70% 75% 70% H1 OH 95% 90% 80% 80% 75% 75% 70% H2 UH 90% 85% 80% 70% 65% 70% 65% H2 OH 90% 85% 75% 75% 75% 70% 65%

[0046] The duty cycles of this set number 002 are calibrated so that, taking into account the other parameters of baking step 2 (no addition of steam), the desired baking chamber temperature of 235 degrees C is achieved.

[0047] During oven operation, a third baking step is subsequently selected, which corresponds to baking step 1 except that no steam is added. Set number 001 according to Table 2 is also used for the third baking step.

[0048] After the sequence of baking steps, the baked goods, in this case Kaiser rolls, are fully baked.

[0049] The variable specification of the duty cycle provides a way to variably specify the power of electrical heating elements with the same nominal power. As an alternative to the variable specification of a duty cycle, other operating parameters of the respective electrical heating element can also be specified. ibe specified variably, for example a current with which the electrical heating element is operated, an electrical voltage with which the electrical heating element is operated and / or a shift in a phase relationship between voltage and current of an alternating current.

[0050] The following control methods can be used to control performance: - Control via a pulse-width modulated signal, - phase control, - Vibration package control is used.

[0051] Depending on the baked goods, an adapted baking program can be set in the oven 1 with, in turn, adapted duty cycles for the electrical heating elements 3 i be deposited.

[0052] The various sets 001, 002, ... can be created by the oven user and adjusted as desired. Oven 1 can be equipped with a corresponding input for this purpose. It is also possible to adjust the operating time sets using appropriate settings, particularly via remote access to oven 1. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2020 211 020 A1

[0002] DE 10 2011 003 122 B4

[0002]

Claims

[1] Oven (1) - with at least one baking chamber (B1, B2, ...), - with a heat source (2) for heating the baking chamber (B1, B2, ...), comprising: — at least one electric heating element (3 i ), -- a power circuit (6 i ) for supplying current to the electric heating element (3 i ), - with a control device (7) which is connected to the power circuit (6 i ) is in signal connection for the variable specification of a heating power with which the electrical heating element (3 i ) is operated. [2] Oven according to claim 1, characterized by that the control device (7) is connected to the power circuit (6 i ) for variable setting of a duty cycle (ED) of the power circuit (6 i ) is in signal connection, where the duty cycle (ED) is a ratio of: - an operating time (BD) during which the electric heating element (3 i) is operated at its nominal power, and - a predetermined useful life (ND) of the baking chamber (Bi). [3] Oven according to claim 1 or 2, characterized by a design as a deck oven with at least two baking chambers (Bi) arranged one above the other, wherein the heat source (2) has at least two electrical heating elements (3 i ) and wherein each baking chamber (Bi) has at least one of the electrical heating elements (3 i ) is assigned. [4] Oven according to one of claims 1 to 3, characterized by that the heat source (2) per baking chamber (Bi) has at least two electrical heating elements (3 i ), wherein one of the electrical heating elements (3 8 up to 3 14 ) as a top heat heating element and another of the electrical heating elements (3 1 up to 3 7 ) is designed as a bottom heat heating element. [5] Oven according to one of claims 1 to 4, characterized bythat the heat source (2) per baking chamber (Bi) has at least two electrical heating elements (3 i ) which serve as top heat heating elements (3 8 up to 3 14 ) are executed. [6] Oven according to one of claims 1 to 5, characterized by that the heat source (2) per baking chamber (Bi) has at least two electrical heating elements (3 i ) which act as bottom heat heating elements (3 1 up to 3 7 ) are executed. [7] Oven according to one of claims 2 to 6, characterized by an embodiment such that the duty cycle (ED) is controlled by a duty cycle (τ / T) of the power circuit (6 i ) is variably specified via the control device (7). [8] Method for operating an oven (1) according to one of claims 1 to 7, comprising the following steps: - Selecting a baking program depending on the baked goods to be baked in the oven (1), - Specifying a first baking step of the baking program with a first set of power values ​​for the electrical heating elements (3 i ), wherein within the first set of power values ​​each of the electrical heating elements (3 i ) an individual performance value is assigned, - Specify at least one further baking step of the baking program with another set of power values ​​for the electrical heating elements (3 i ), wherein within the further set of power values ​​each of the electrical heating elements (3 i ) is assigned an individual performance value. [9] Method according to claim 8, characterized by a baking step specification such that at least two performance values ​​within one of the sets are different. [10] Method according to claim 8 or 9, characterized by a baking step specification such that the power values ​​of the different sets that correspond to the same electrical heating element (3i ) are assigned. [11] Method according to one of claims 8 to 10, characterized by a baking step specification such that at least one (3 1 ) of the electrical heating elements (3 i ), which has a removal opening (10 i ) of the baking chamber (Bi), a higher power value is specified within a set than for another (3 2 , ... 3 7 ) of the electrical heating elements (3 1 up to 3 7 ), which is further away from the removal opening (10 i ) is arranged. [12] Method according to one of claims 8 to 11, for operating a deck oven according to claim 3, characterized by a baking step specification such that at least one of the electrical heating elements (3 1 up to 3 14), which is assigned to a lowest baking chamber (B1), a higher power value is specified within a set than for another of the electrical heating elements (3 1 up to 3 14 ), which is assigned to a baking chamber (B2) located further up.

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