Cooking appliance with inflow channel and return channel for a hot gas flow

Abstract

Cooking appliance (1) with at least one cooking chamber (2), a heating device (4), a blower (5), an inlet channel (7) which directs a forward flow (8) of a hot gas stream (6) from the heating device (4) to the cooking chamber (2), and a return flow channel (10) which directs a return flow (11) of the hot gas stream (6) from the cooking chamber (2) to the heating device (4), wherein one of the two channels (7, 10) is connected to an evaporator (16) which is flowed through or around by the forward flow (8) or the return flow (11) of the hot gas stream (6), characterized by a closable bypass device (17) which, in the open position, directs the hot gas stream (6) from the inlet channel (7) directly to the return flow channel (10).

Description

[0001] The invention relates to a cooking appliance with at least one cooking chamber, a heating device, a blower, an inflow channel that directs a forward flow of a hot gas stream from the heating device to the cooking chamber, and a return channel that directs a return flow of the hot gas stream from the cooking chamber to the heating device, wherein one of the two channels is connected to an evaporator that is flowed through or around by the forward or the return flow of the hot gas stream.

[0002] A cooking appliance can be, for example, a conventional oven, a steam cooker, or a combination steamer. If the cooking appliance is designed as a conventional oven, the cooking chamber is also referred to as a baking chamber or oven.

[0003] From DE 1057994 A, a periodically reversible forced circulation oven heating system is known, in which a two-winged reversible flap is arranged in the center of a pipe cross, which is periodically and automatically switched between two limit positions offset by 45° relative to the nozzle axes, thus reversing the flow direction through the oven's flow channels. An evaporator for steaming the baked goods is not mentioned here.

[0004] A cooking appliance designed as an oven, in particular a deck oven, with the aforementioned features is known, for example, from patent DE 195 16 514 C2 filed by the applicant. The deck oven has a plurality of baking chambers arranged one above the other for receiving trays loaded with baked goods. The trays are inserted and removed via oven doors assigned to the baking chambers. In the deck oven disclosed in DE 195 16 514 C2, a heating device designed as a burner unit with a heat exchanger and a blower serve to generate a hot gas stream with which the oven atmosphere is indirectly heated. For indirect heating, the hot gas stream flows via an inlet channel, referred to as a distribution channel arrangement, into individual heating radiators assigned to the baking chambers, through which the heat of the hot gas stream is transferred to the individual baking chambers.In this system, the hot gas flow is not mixed with the oven atmosphere due to a closed flow circuit. The heating radiators have paired supply channels, with each supply channel having a corresponding return channel. The supply channels carry the hot gas flow to the ovens, while the return channels carry the hot gas flow away from the ovens. This ensures a uniform flow rate across the surface of the heating radiator. The return flow of the hot gas, cooled in the heating radiators, to the burner unit is via a return channel known as a manifold. The overall flow path for the hot gas flow is fixed and unchanging.

[0005] The baking chambers of the deck oven disclosed in DE 195 16 514 C2 further feature a steam supply device on the rear wall, which is connected to an evaporator via a steam supply line. Details of the evaporator are not disclosed. Generally, an evaporator generates steam, which is also referred to in technical jargon as steam vapor or steam. The action of the steam vapor on the food being cooked in the appliance positively influences the cooking result. To generate the steam vapor, the evaporator is heated and water is added to or placed on the evaporator. If the appliance is an oven, the evaporator can be heated, for example, by the flow or return of the hot gas stream.

[0006] In cooking appliances with the aforementioned features, if the evaporator is heated by the hot gas stream to heat the cooking chamber, steam can only be generated if the cooking chamber is also heated. Short cooking times are often insufficient to heat the evaporator to the temperature required for steam generation. In this case, preheating the evaporator is necessary, which can negatively impact the cooking process because the cooking chamber is also unintentionally preheated. This unwanted preheating of the cooking chamber can impair the cooking result and / or result in unnecessary energy consumption.

[0007] The object of the invention is therefore to provide a cooking appliance in which the flow path of the hot gas stream for heating the cooking chamber and the evaporator can be actively and flexibly controlled. Such a cooking appliance achieves high flexibility, as well as high time and energy efficiency, while delivering high-quality cooking results.

[0008] This problem is solved by a cooking appliance having all the features of claim 1.

[0009] The cooking appliance comprises at least one cooking chamber, a heating device, a fan, a supply channel that directs a flow of hot gas from the heating device to the cooking chamber, and a return channel that directs a return flow of hot gas from the cooking chamber to the heating device. One of the two channels, i.e., the supply channel or the return channel, is connected to an evaporator through which the supply or return flow of hot gas flows.

[0010] The heating element and the fan generate the hot gas flow, which flows regularly from the heating element through the fan and is conveyed as a supply flow through the inlet duct. The inlet duct opens into the cooking chamber or runs alongside it in such a way that the oven atmosphere in the cooking chamber is heated as described above in connection with the prior art. From the cooking chamber or from the inlet duct, the hot gas flow flows downstream of the cooking chamber as a return flow through the return duct back to the heating element and / or at least partially to a chimney.

[0011] The evaporator can, in particular, be a device with a heat storage element made of a material with high heat storage capacity, for example, metal, especially cast metal. At least one section of the inlet or outlet channel leads to the evaporator. As the inlet or outlet flows through or around the evaporator, the heat storage element is heated, and the water directed onto its surface evaporates. The resulting vapor is then directed into the cooking chamber. Alternatively, it is also possible to design at least one section of the inlet or outlet channel with a large cross-section, allowing the evaporator to be located in this section and surrounded by the inlet or outlet flow. This also makes it possible to convey the water evaporating upon contact with the surface of the heat storage element as steam into the cooking chamber.

[0012] To solve the above problem, the cooking appliance has a lockable bypass device which, in the open position, directs the hot gas flow from the inflow channel directly to the return flow channel.

[0013] In other words, the inlet and outlet channels are connected by a fluid-conducting connection, and this connection can be opened or closed. When the connection is open, the bypass device is in the open position. At least a portion of the supply flow, which would otherwise flow completely from the heating element to the cooking chamber when the connection is closed, can then be diverted and directed directly into the outlet channel without first flowing to the cooking chamber. The connection is closed by a closing device, specifically by covering the opening forming the connection with a cover. This cover is actively adjustable, meaning that its position can be changed by an actuator.When the connection opening is closed with the cover, the bypass device is in the closed position and the flow cannot pass directly from the inlet channel to the return channel. Further details about the cover are described below.

[0014] The hot gas flow can be flexibly directed according to the predetermined heating requirements of the cooking appliance by means of the closable bypass device connecting the inlet and outlet channels. In particular, this flexible routing of the hot gas flow makes it possible to heat individual areas of the cooking appliance according to specific requirements and even independently of one another. For example, the evaporator can be heated more quickly or even selectively, independently of the cooking chamber, when the connection between the inlet and outlet channels is open. Additionally, it is also possible to individually heat other areas connected to the flow channel, or even other devices connected to the cooking appliance, with the hot gas flow.For example, if a fermentation chamber or a holding chamber is connected to the inflow or outflow channel of the cooking appliance, these can also be heated with the hot gas flow according to individual requirements, provided the bypass device is at least partially open. Overall, this significantly increases the flexibility of such a cooking appliance.

[0015] Additionally or alternatively, energy can be saved during cooking by heating the evaporator independently. If it is not necessary to actively heat the cooking chamber during certain cooking phases, the thermal energy of the hot gas flow can be directed to the evaporator. This results in overall energy savings when using the cooking appliance described here compared to a cooking appliance known from the prior art. Furthermore, the targeted heating allows the evaporator to reach the temperature required for steam generation more quickly, thus shortening the overall cooking time. These advantages are achieved in a structurally simple manner with the cooking appliance described here, making the appliance and the cooking process cost-effective and ensuring excellent cooking results.

[0016] In practice, the cooking appliance can be an oven, especially a deck oven. If the cooking appliance is designed as an oven, it is particularly advantageous to heat the evaporator with the hot gas stream that is also used to heat the oven cavity. This is because the temperature of the hot gas stream in an oven is typically very high, and this heat cannot usually be fully utilized to heat the oven cavity anyway. Excess heat can then be used effectively to heat the evaporator.

[0017] Furthermore, due to the high temperature of the hot gas stream, baking processes often require only a short time. With conventional ovens and the characteristics described above, this short time is regularly insufficient to generate the large volume of steam often needed during baking, because the evaporator does not heat up sufficiently during the brief baking period. Therefore, it is particularly advantageous for ovens to be able to heat the evaporator independently of the baking chamber, and especially to be able to preheat it. Of course, selective preheating of the evaporator can also be beneficial for longer baking times.

[0018] In a first embodiment, the oven can be a deck oven in which the oven atmosphere is heated, for example, as is known from the prior art, by passing flue gases as a hot gas stream through heating radiators that form the walls of the baking chamber and heat the baking chamber. This embodiment is referred to in DIN 8766 as a hot gas recirculating oven. The baking chamber is then not fluidically connected to the aforementioned channels for the hot gas (flue gas). For the purpose of indirectly heating the oven atmosphere, deck ovens have a closed channel arrangement with an inflow channel and a return channel, into which the bypass device can be integrated with very little design effort. In this case, the heating device is a burner, and the flue gases from the burner form the hot gas stream that flows through the heating radiators and the steam generator.

[0019] Alternatively, the cooking appliance can be a convection oven, in particular a rack oven, in which the cooking chamber is permeated by hot gas and fluidically connected to the aforementioned channels. This embodiment is referred to in DIN 8766 as a hot air circulating oven. In a cooking appliance whose cooking chamber and channel system are fluidly connected, the hot gas flow used to heat the cooking chamber and the steam generator is the heated cooking chamber atmosphere. This hot gas flow can, for example, be heated via a heat exchanger within the oven housing.

[0020] In practice, the evaporator can be located in or adjacent to the return flow channel. In other words, the return flow can flow through or past the evaporator and heat it. When the evaporator is located in or adjacent to the return flow channel, the power required from the heating element for the proper heating of the baking chamber and the evaporator is particularly low. It is especially lower than the power required to heat the baking chamber and an evaporator located in or adjacent to the supply flow channel. If the heating element is located in the return flow channel and is designed as a burner unit, energy savings of 10 to 15% can be achieved compared to arranging the evaporator in the supply flow channel.

[0021] In practice, the inflow and return channels can share a common partition, and the bypass device can be a closable opening located in this partition. It is sufficient if only a limited section of the inflow and return channels is separated by a common partition. If the opening in the partition is not closed, the inflow and return channels are directly connected.

[0022] The closing device described above for closing the opening can, in practice, be a flap movable by means of the actuator. This flap is suitable for covering or opening the opening in the common partition between the inflow and return channels. In the closed position of the bypass device, the flap rests against the partition with one side, thus covering the opening. The flap can be pivoted into the inflow channel by means of the actuator via a hinge attached to the partition. In the open position, the flap rests against the partition with a second side, opposite the first, or it protrudes into the inflow channel, thus blocking its cross-section. This type of cover design is particularly simple in construction and functionally reliable because only simple components are used.Alternatively, the closing device can also be a slider that, depending on its position, completely or partially covers the opening. A louvered shutter, similar to blinds, or a central shutter, similar to aperture grilles, can also be used as the closing device. For this, an actuator with a shorter travel distance can be used. The actuator can be, for example, electrically, hydraulically, or pneumatically driven.

[0023] In practice, the valve can be a valve that can assume the following three positions: - the flow path from the inflow channel into the cooking chamber is open and the opening between the inflow channel and the return flow channel is closed; - the flow path from the inflow channel into the cooking chamber is closed and the opening between the inflow channel and the return flow channel is open; - the flow path from the inflow channel into the cooking chamber is partially open and the opening between the inflow channel and the return flow channel is partially open.

[0024] For these positions, the geometry of the flap is designed such that the cross-section of the inflow channel downstream of the opening is essentially completely blocked when the bypass device is open and the flap projects into the inflow channel perpendicular to the flow direction. This allows for particularly precise control of the hot gas flow, making cooking with the appliance especially efficient. In particular, it is also possible to switch between the aforementioned positions during a cooking process, even for short periods, according to the heat requirements of the cooking chamber or the evaporator.

[0025] In practice, the partition between the inlet and outlet channels can be located above the cooking chamber. The outlet channel is then positioned, for example, above the inlet channel, which in turn is located above the cooking chamber. This arrangement allows the cooking appliance to occupy a particularly small footprint. Furthermore, optimal heat distribution within the inlet channel, the cooking chamber, and the outlet channel is ensured, as radiant heat lost to the surroundings is at least partially transported back into the cooking chamber via the inlet.

[0026] Further practical embodiments and advantages of the invention are described below in connection with the drawings. They show: Fig. 1 the cooking appliance according to the invention, designed as a deck oven, in a side view with a partially cut side wall and with the cover of the bypass device closed; Fig. 2a a detailed view of the in Fig. 1. Area designated II of the cooking appliance according to the invention with closed cover of the bypass device; and Fig. 2b a detailed view of the in Fig. 1 area of ​​the cooking appliance according to the invention designated II with the cover of the bypass device open.

[0027] Fig. Figure 1 shows a partially cutaway side view of a cooking appliance 1 designed as a deck oven, with a total of six cooking chambers 2 arranged one above the other, which are also referred to as ovens. The cooking chambers 2 are separated from each other vertically by heating radiators 3. Alternatively, the cooking appliance 1 could also be, for example, a steam oven or a combination oven.

[0028] Above the uppermost baking chamber 2 is a heating device 4 for heating a hot gas stream 6 generated by a blower 5. The heating device 4 can, for example, be a burner 4, with the flue gases produced during combustion forming the hot gas stream 6. The hot gas stream 6 flows in an inlet duct 7 from the blower 5 to the individual heating radiators 3, the hot gas stream 6 flowing in the inlet duct 7 being referred to as the supply 8. Like the heating device 4, at least a first section of the inlet duct 7 is arranged above the uppermost baking chamber 2; a second section of the inlet duct 7 is arranged at the rear of the baking chambers 2, opposite the baking chamber doors 9 of the baking chambers 2. The baking chambers 2 are heated indirectly by transferring the heat stored in the hot gas stream 6 from the heating radiators 3 to the atmosphere in the baking chambers 2.

[0029] Once the hot gas stream 6, cooled in the heating radiators 3, has left the heating radiators 3, it is guided back to the heating device 4 and the blower 5 via a return channel 10. The hot gas stream 6 flowing in the return channel 10 is referred to as the return 11. For the return of the return 11, a first section of the return channel 10 is located at the rear of the baking chambers 2 downstream of the second section of the supply channel 7, and a second section of the return channel 10 is located upstream of the first section of the supply channel 7. Due to this arrangement of the return channel 10 adjacent to the supply channel 7, the supply channel 7 and the return channel share a common partition 12. This reduces heat loss from the inflow channel 7, because the return channel 10 is located on its sides facing away from the baking chambers, in which the return flow 11 flows at a temperature far above the ambient temperature.

[0030] The supply line 8 and the return line 11 of the hot gas stream 6 form a closed circuit in the cooking appliance described here.

[0031] In an alternative embodiment of the cooking appliance, not shown here, for example a convection oven, it is also possible to heat the cooking chamber directly with the hot gas stream, with the supply flowing into the cooking chamber and the return flowing from the cooking chamber to a fan. In this embodiment, the hot gas stream is therefore the cooking chamber atmosphere, which flows past the steam generator and, in accordance with the invention, is guided through the supply channel and the return channel.

[0032] The in Fig. The individual baking chambers 2 shown in Figure 1 each have baking chamber doors 9 on a front side 13 of the deck oven 1 for closing loading openings. At their rear wall 14, each individual baking chamber 2 is connected to a steam supply line 15, which in turn is connected to an evaporator 16, also referred to as a steam generator. A steam plume can be conveyed from the evaporator 16 to the individual baking chambers 2 via the steam supply lines 15.

[0033] The steam generator or evaporator 16 is connected to a water supply line (not shown) and is designed to evaporate large quantities of water and supply it to the baking chambers 2. The evaporator 16 is located in the return channel 10 and is heated by the return flow 11 of the hot gas stream 6. Alternatively, the steam generator 16 can also be located in the supply channel 7 (not shown). Heat storage elements (not shown), typically rods or similar steel elements, can be arranged in the steam generator 16.

[0034] The deck oven 1 also features a lockable bypass device 17, which, in the open position, directs the hot gas flow 6 from the inlet channel 7 directly to the return channel 11. The bypass device 17 is in Fig. 1 in the area designated II and enlarged in the Fig. 2a and the Fig. 2b shown. The Fig. 1 and the Fig. 2a the bypass device 17 in a first, closed position and the Fig. Figure 2b shows the bypass device 17 in a second, open position.

[0035] The Fig. 2a and the Fig. Figure 2b shows that the bypass device 17 has an opening 18 formed in the partition 12 between the inflow channel 7 and the return channel 10. The opening 18 can be closed by means of a closing device designed as a flap 19. For this purpose, the flap 19 is designed as a substantially flat sheet metal, the surface area of ​​which is larger than the opening 18, so that the flap 19 can be placed against the partition 12 with one side covering the opening 18. When the opening 18 is covered by the flap 19, the bypass device 17 is located in the position shown in Fig. 1 and Fig. 2a shows the first, closed position. In this closed position of the bypass device 17, the flow path of the hot gas stream 6 from the inlet channel 7 into the cooking chambers 2 is open.

[0036] In contrast to the closed position, the bypass device 17 is located in the Fig. 2b shows the second, open position when the opening 18 is released by the flap 19 and the flow path of the hot gas stream 6 from the inlet channel 7 into the cooking chambers 2 is blocked by the flap 19. In order for the flap 19 to substantially completely block the flow cross-section leading from the inlet channel 7 into the cooking chambers 2, the size of the flap 19 corresponds at least to the size of a cross-section 22 of the inlet channel 7 adjacent downstream of the opening 18.

[0037] In the open position, the inflow channel 7 and the return channel 10 are directly connected to each other, so that at least part of the supply flow 8, which flows completely from the heating device 4 to the baking chambers 2 when the opening 18 is closed, can be diverted and directed directly into the return channel 10 without first flowing to the baking chambers 2.

[0038] The opening 18 is opened and closed by pivoting the flap 19 about a joint 20 fixed to the partition 12 by means of an actuator 21 also attached to the partition 12. The actuator 21 is usually an electric drive, but can also be pneumatically or hydraulically operated and have a control unit that is connected to the oven control system. By connecting the actuator control unit to the oven control system, the actuator position, and thus the position of the flap, can be adjusted during a baking process.

[0039] The bypass device 17 can also be moved into any partially open intermediate position (not shown). In this intermediate position, the flap 19 is in a position between the first and second positions. The opening 18 is then not completely closed by the flap 19, and the flap 19 protrudes into the inflow channel 7 without completely closing it. In other words, both the flow path from the inflow channel 7 into the baking chambers 2 is partially open, and the opening 18 between the inflow channel 7 and the return channel 10 is partially open.

[0040] Using the Fig. 1, Fig. 2a and Fig. In the arrangement described in 2b, it is possible to move the flap 19 flexibly into one of the positions described above during a baking process, so that the hot gas flow 6 can be flexibly directed according to predetermined heat requirements of the baking chambers 2 or the evaporator 16.

[0041] This flexibility significantly improves the performance of the cooking appliance described here. In conventional cooking appliances without a bypass device, the evaporator is only heated when the burner and fan are operating. Switching off the burner also interrupts the heat supply to the evaporator.

[0042] Due to the bypass device 17, it is possible in the arrangement described here to heat the evaporator 16 independently of the baking chambers 2. With the bypass device 17 open (see... Fig. 2b) The hot gas stream 6 flows directly from the burner assembly 4 through the opening 18 in the partition 12 into the upper, second section of the return channel 10, in which the evaporator 16 is located. Consequently, all the heating energy from the burner assembly 4 is supplied to the evaporator 16. This can be useful, for example, before loading the oven if no heating energy is to be supplied to the baking chambers 2, but heating the evaporator 16 to operating temperature is necessary.

[0043] Even during baking operations, phases can occur in which the baking chambers 2 require no or only a small energy supply, but the steam generator / evaporator 16 must be heated intensively. This can happen immediately after a steam burst is released by the evaporator 16. The bypass device 17 can also be opened during this period ( Fig. 2b), so that the hot gas flow 6 flows directly from the burner assembly 4 through the opening 18 in the partition 12 to the evaporator 16.

[0044] If, on the other hand, the baking chambers 2 have an increased energy requirement, the bypass device 17 can be closed (see below). Fig. 2a), so that the hot gas stream 6 flows from the burner device 4 through the baking chambers 2 and only then past the steam apparatus / evaporator 16.

[0045] Furthermore, the heating energy of the burner can be divided as desired by moving the flap 19 to an intermediate position, so that a first predetermined portion of the hot gas flow 6 flows into the baking chambers 2 and the remaining portion of the hot gas flow 6 flows directly through the opening 18 in the partition 12 to the evaporator 16. The features of the invention disclosed in this description, in the drawings, and in the claims can be essential for realizing the invention in its various embodiments, both individually and in any combination. The invention is not limited to the described embodiments. It can be varied within the scope of the claims and taking into account the knowledge of the person skilled in the art. Reference symbol list 1 cooking appliance, deck oven 2 Cooking chamber, baking chamber 3 heating radiators 4 Heating device, burner device 5 blowers 6 Hot gas stream 7 Inflow channel 8 lead time 9 oven doors 10 Return flow channel 11 Return 12 Partition wall 13 Front 14 Back panel 15 steam supply lines 16 evaporators, steam generators 17 Bypass device 18 Opening 19 Locking device, flap 20 joint 21 Actuator 22 Cross-section of the inflow channel

Claims

[1] Cooking appliance (1) comprising at least one cooking chamber (2), a heating device (4), a blower (5), an inlet channel (7) which directs a forward flow (8) of a hot gas stream (6) from the heating device (4) to the cooking chamber (2), and a return flow channel (10) which directs a return flow (11) of the hot gas stream (6) from the cooking chamber (2) to the heating device (4), wherein one of the two channels (7, 10) is connected to an evaporator (16) which is through or around which the forward flow (8) or the return flow (11) of the hot gas stream (6) flows, characterized by a lockable bypass device (17) which, in the open position, directs the hot gas flow (6) from the inflow channel (7) directly to the return flow channel (10). [2] Cooking appliance according to claim 1, characterized by , that the cooking appliance (1) is an oven (1), in particular a multi-level oven (1). [3] Cooking appliance according to claim 1 or 2, characterized by that the evaporator (16) is arranged in or on the return flow channel (10). [4] Cooking appliance according to any one of claims 1 to 3, characterized by , that the inflow channel (7) and the return flow channel (10) have a common partition (12) and that the bypass device (17) is a lockable opening (18) arranged in this partition (12). [5] Cooking appliance according to claim 4, characterized by , that the opening (18) can be closed by means of a flap (19) movable by means of an actuator (21). [6] Cooking appliance according to claim 5, characterized by , that the movable flap (19) is a flap (19) which can assume the following three positions: - The flow path from the inflow channel (7) into the cooking chamber (2) is open and the opening (18) between the inflow channel (7) and the return flow channel (10) is closed; - The flow path from the inflow channel (7) into the cooking chamber (2) is closed and the opening (18) between the inflow channel (7) and the return flow channel (10) is open; - The flow path from the inflow channel (7) into the cooking chamber (2) is partially open and the opening (18) between the inflow channel (7) and the return flow channel (10) is partially open. [7] Cooking appliance according to claim 4, characterized by , that the partition (12) between the inflow channel (7) and the return channel (10) is located above the cooking chamber (2).

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