Evaporator for a steam treatment device as well as steam treatment device

Abstract

Evaporator (1) for a steam treatment device (H), comprising a receiving chamber (R) for liquid to be evaporated with a bottom-side surface heating element (9) which has a circumferential side edge (27), wherein the side edge (27) is at least partially convex in cross-section, characterized in that the surface heating element (9) has several independently operable planar heating conductor tracks (29), wherein at least two of the heating conductor tracks (29) have a different nominal power.

Description

[0001] The invention relates to an evaporator for a steam treatment appliance, comprising a receiving chamber for the liquid to be evaporated and a bottom-side surface heater. The invention further relates to a steam treatment appliance with such an evaporator. The invention is particularly advantageously applicable to steam cooking appliances, either as standalone units or as combination units. The invention is particularly advantageously applicable to household appliances.

[0002] DE 10 2006 029 578 A1 discloses a steam cooker as an evaporator device with a water evaporator, wherein the evaporator has a heatable water container and a detection area connected to the water container in the manner of communicating vessels for detecting the fill level of the water container. The detection area is vertically tubular and has at least one sensor for detecting the fill level.

[0003] DE 10 2009 044 053 A1 discloses a steam generator for a household appliance with an evaporator chamber to which a connection for the water supply and at least one connection for the steam discharge are flow-conducting, and with a heatable evaporator surface arranged at an angle to the horizontal in its installed position, above which an evaporator chamber for the generated steam is formed and in which a steam flow develops towards the steam outlet, wherein the water supply to the evaporator surface is controllable or regulated via a valve or pump arranged in the supply line, and the water level above the evaporator surface is detected by means of a level monitoring device and evaluated for controlling the water supply to the evaporator surface. To create a steam generator for a household appliance with a small installation volume and high heating capacity, or...To design a steam output suitable for continuous steam generation and to reliably prevent the heating device from running dry, the level monitoring device is located in the area of ​​the evaporator chamber of the steam generator where there is little to no flow intensity of the steam over the evaporator surface.

[0004] DE 10 2010 029 307 A1 discloses a household appliance with a container for holding liquids, which is designed in particular for storing and automatically dispensing a detergent. An electrical measuring device is provided for measuring the fill level of the storage container. The measuring device comprises two measuring electrodes spaced apart from each other within the container, as well as a circuit arrangement coupled to the measuring electrodes. This circuit arrangement is configured to apply an alternating voltage between the measuring electrodes and to measure at least one quantity correlated with the alternating voltage and with the conductance of a medium located between the measuring electrodes. A corresponding fill level measurement method is also disclosed.

[0005] WO 2009 / 007456 A2 discloses a device for adding water to generate steam in a cooking appliance, comprising an evaporator vessel into which water can be supplied depending on the fill level of the water contained in the evaporator vessel, and electrodes with which the fill level of the water in the evaporator vessel can be detected, wherein an inner wall of the evaporator vessel is at least partially made of an electrically conductive material and this part of the inner wall is a first electrode.

[0006] EP 0 471 342 A2 discloses an arrangement in which two measuring electrodes are positioned in a container at different horizontal and vertical distances from an electrically conductive, grounded inner wall of the container, one of them in the region of the forming ice layer. The measuring electrodes detect resistance values ​​of the ice and / or the water located between the electrodes and the inner wall of the container. To cool the water, regardless of its chemical and physical composition, potentials corresponding to the resistances are generated and fed to a differential amplifier. Depending on a comparison of the magnitude of the two resistance values, a refrigeration unit acting on the contents of the container is switched on or off.

[0007] DE 10 2009 055 146 A1 discloses a steam generation system for a household appliance, in particular a steam cooker, comprising at least one drainable liquid reservoir, an evaporator supplied with liquid from the liquid reservoir via at least one supply line, and at least one pump for moving the liquid, wherein the liquid can be pumped back towards the liquid reservoir by means of the at least one pump. A method is provided for operating the steam generation system.

[0008] DE 19741881 A1 discloses a household appliance for steam cooking at near ambient pressure, comprising a cooking chamber, a steam generator with a heating element, and a temperature sensor connected to a control device for regulating the heating element of the steam generator. To create a household appliance for steam cooking at near ambient pressure, in which cooking is done exclusively with steam, and which is intended to be flexibly installed in the kitchen and independent of conditions at the installation site, the steam generator with the heating element is arranged separately outside the cooking chamber. A water reservoir is preferably located near the steam generator, and the temperature sensor is located in the cooking chamber.

[0009] EP 1 658 798 A1 discloses a steam generator with a housing for forming a steam generation chamber, the housing having a steam outlet opening. A heating plate is held by the housing within the steam generation chamber. A water inlet valve is in fluid communication with the housing for selectively supplying water to the steam generation chamber, thereby directing water to the heating plate for conversion into steam. The heating plate forms a bottom wall of the steam generation chamber and is designed to have a raised section.

[0010] The object of the present invention is to overcome at least some of the disadvantages of the prior art and in particular to provide a particularly easy-to-assemble and reliable evaporator for a steam treatment device, especially for household appliances, and in particular for cooking appliances.

[0011] This problem is solved according to the features of the independent claims. Preferred embodiments can be found in particular in the dependent claims.

[0012] The problem is solved by an evaporator for a steam treatment device, comprising a receiving chamber for liquid to be evaporated with a bottom-side surface heating element, which surface heating element has a circumferential side edge, wherein the side edge is at least partially convex in cross-section (or bombé or curved outwards).

[0013] The convex design of the side edge facilitates easy sliding of the surface heater against the evaporator housing, preventing mechanical stress on the heater during thermal expansion (e.g., when switched on). This also simplifies the installation of a seal between the heater and the housing. Furthermore, the convex side edge serves as a receiving or holding area for a seal, allowing for easy pre-tensioning. This, in turn, improves the seal's secure fit, even under relative movement between the heater, seal, and / or housing.

[0014] It is a further development that the side edge or border is convex along its entire length or completely around. The side of the surface heating system facing the recording space can also be referred to as its front, and the side facing away from the recording space as its back.

[0015] The floor-mounted surface heating system offers the advantage that the liquid in the receiving chamber can be heated quickly and easily over a large area to generate steam. The liquid level in the receiving chamber can be very low, for example, in the range of millimeters, e.g., between 8 and 10 millimeters, or e.g., 9 millimeters, which further facilitates rapid heating and allows for a low-profile design. The surface heating system therefore preferably forms a wall at the bottom of the receiving chamber.

[0016] The receiving chamber for the liquid to be evaporated may also be referred to as an evaporator chamber or vapor generation chamber. It is at least fillable with liquid, particularly water, and has at least one liquid inlet or feed opening for this purpose. It also has at least one vapor outlet opening for releasing the vapor generated from the liquid. The receiving chamber may also be emptied of liquid. For this purpose, it may have a separate drain opening, or the liquid may be supplied and drained through the same opening. The receiving chamber is preferably filled with fresh water, while any emptied liquid can be considered, for example, wastewater.

[0017] One embodiment of the surface heating system comprises a support plate that defines the receiving space, on the rear side of which, facing away from the receiving space, at least one heating conductor is arranged, and a side edge or border of the support plate is convex in cross-section, at least in sections. This embodiment can be implemented in a compact and robust manner.

[0018] The mounting plate may be made of metal, for example, a ferrous metal such as stainless steel. The mounting plate may be a sheet metal part. The mounting plate may be a flat plate, at least when the evaporator is unheated. The mounting plate may be, for example, bare or scaled on its front surface facing the receiving chamber. Alternatively, the mounting plate may be made of ceramic.

[0019] To achieve particularly low thermal inertia and thus high energy efficiency, while simultaneously maintaining good heat dissipation and high robustness, the carrier plate has a thickness of between one and two millimeters, but this thickness is not limited to that range. Furthermore, within this thickness range, the side edge or border can be formed with sufficient precision using simple methods to achieve a sufficiently convex shape.

[0020] The at least one heating conductor track can be, for example, a thin-film or thick-film heating conductor track and serve as an electrical resistance heating element. A thick-film heating conductor track, in particular, is especially easy and cost-effective to manufacture with high quality and is still very space-saving. The at least one heating conductor track may be attached to the substrate, especially in the case of an electrically conductive substrate, via an electrical insulation layer to prevent a short circuit.

[0021] The surface heating system may have a protective layer on its back side, facing away from the recording room, for example as protection against mechanical stress. It is a further development that the surface heating system has a thickness of between one and two millimeters.

[0022] Another embodiment involves the evaporator having a seal that rests against the convex side edge. The convex side edge, in conjunction with the housing, forms a receiving or holding area for the seal in a particularly simple manner. The seal may be positioned along the side edge of the surface heating element. The seal may have a cross-sectional shape and material composition similar to an O-ring, but may, for example, deviate from a circular annular shape in a top view. However, the type of seal is not fundamentally limited; it may, for instance, also be designed as a flat gasket.

[0023] It is generally a design where the seal is tensioned by means of the side edge, which ensures its correct fit even under thermal deformation of the surface heating element. The seal may be held in place specifically by the housing and the side edge.

[0024] Another embodiment involves a double seal with two sealing elements arranged one above the other, bearing against the side edge on the upper and lower sides, respectively. This achieves a particularly reliable seal. The two sealing elements may be identical or different, for example, having the same or different basic shapes (in top view). Each of the two sealing elements may be designed like a seal as described above. The two sealing elements may be separate parts or connected to each other.

[0025] Another embodiment involves a side edge that is cornerless when viewed from above. This means the side edge has no corners, but is either continuously curved (e.g., circular or oval) or has alternating curved and straight sections with smooth transitions. This allows for a particularly cost-effective and, due to improved process reliability, highly reliable seal against the housing. A further development involves the side edge having a rectangular shape with rounded corners when viewed from above.

[0026] Furthermore, one embodiment of the evaporator comprises a housing with a base and a lid, and the receiving chamber is formed by the lid and the surface heating element. The base and lid are made of different materials. This design takes advantage of the fact that, unlike the lid, the base does not come into contact with the water to be evaporated, and the requirements for the two parts do not need to be the same. The housing is therefore at least two-part. In particular, the two parts may be made of different plastics. A seal can, in particular, prevent the liquid from penetrating to or into the base.

[0027] It is also possible for the lid to be made of a food-grade material. The base, however, does not need to be made of a food-grade material. If a seal is present and may come into contact with the liquid being evaporated, it is advantageous for it to also be made of a food-grade material. This way, the use of often expensive food-grade material can be limited to just a few parts.

[0028] It is a further development that the base is made of a flame-retardant material, which increases operational safety and improves flame protection. Food-grade plastic, on the other hand, is typically not flame-retardant.

[0029] A further improvement is that the base is made of a more elastic material than the lid. This makes it easier to attach the evaporator to a household appliance via its base. It also simplifies the fastening of the base and lid, for example, by using a snap-fit ​​mechanism. Food-grade plastic, on the other hand, is generally comparatively brittle.

[0030] Another design feature is that the surface heating system has several independently operable, flat heating conductor tracks. This allows for a particularly precise gradation of the applied heating power in a simple way (e.g., with a constant heating current and / or a fixed heating current cycle).

[0031] Another design option is to have at least two of the heating conductor tracks have different nominal power ratings or different maximum power ratings. This allows for particularly precise gradation of the applied heating power with a small number of heating conductor tracks.

[0032] For example, the different nominal power ratings can have multiple values ​​relative to each other, e.g. in the form n·L with L a predetermined basic heating power and n a natural number greater than zero, in particular the number of existing heating conductor tracks.

[0033] For example, n = 2 heating conductor tracks can be present with a base heating power of L = 400 W, where the first heating conductor track has a nominal power of 1·L = 400 W and the second heating conductor track has a nominal power of 2·L = 800 W. They can be operated together with a heating power of 1200 W.

[0034] The different nominal power ratings can also be staggered, for example, according to a logarithmic series, for instance in the form 2 (n-1) ·L. With four heating conductor tracks, this results in respective nominal powers of 100 W, 200 W, 400 W and 800 W respectively, based on a basic heating power of L = 100 W.

[0035] However, other values, especially different levels of nominal power, are also possible.

[0036] It is a further development that the evaporator has two exposed electrical contacts in the receiving chamber for determining the fill level, wherein the surface heating has at least one unheated zone and at least one electrical contact is located above this unheated zone. This means that the electrical contacts are less exposed to a turbulent liquid surface when the surface heating is switched on and are therefore far less likely to be unintentionally triggered before the predetermined fill level is reached than if they were located above a heated or heatable zone. In particular, the liquid above a heated zone can boil with bubbling and / or strong turbulence, which agitates the surface there particularly strongly. Nevertheless, a particularly simple and compact design can be maintained.

[0037] It is a further development that the exposed electrical contacts are parts of a level detector or level determination device, which is also referred to below as a "short-circuit level detector". They can, in particular, represent a sensor or sensory component of the level detector. An evaluation unit for evaluating (e.g., for performing a threshold comparison) a signal (e.g., voltage values) output by at least one of the contacts may be part of the evaporator or may be located outside of it. The evaluation unit may, for example, comprise a circuit such as a microprocessor, an ASIC, an FPGA, etc. However, an evaluation unit may also be omitted. For example, a voltage signal output by a sensor may be used to switch a switch, e.g., an electronic switch such as a transistor or an electrical switch such as a relay.

[0038] It is also a further development that the surface heating element has an electrically conductive surface facing the liquid, and that this surface, in particular, forms one of the two electrical contacts of the short-circuit level detector. This eliminates the need for a second dedicated or separate electrical contact. A further advantage is that the liquid is not disturbed at the surface heating element, resulting in an even more reliable determination of when the predetermined fill level has been reached.

[0039] Furthermore, it is a further development that the two electrical contacts are electrically conductive pins ("contact pins") inserted into the recording chamber from the ceiling. This makes them easy to remove or replace and also reduces their frequent exposure to the liquid, thus minimizing, for example, the deposition of substances contained in the liquid and potential chemical corrosion.

[0040] Furthermore, it is a further development that at least one of the electrical contacts can be arranged on a side wall in the receiving chamber. For example, an electrically conductive pin may be inserted through a side wall into the receiving chamber. Alternatively, the inside of the evaporator may be provided with an electrically conductive layer or similar material.

[0041] It is also a further development that a steam outlet or steam outlet opening is located above the unheated zone. This has the advantage that no small water droplets are carried along with the steam stream, which typically form on the agitated water above the heated zone. This improves steam quality. The fewer water droplets contained in the steam stream, the higher its energy content and thus its efficiency. Furthermore, this prevents the food being damaged by water droplets in the food handling area.

[0042] It is a further development that the unheated zone corresponds to an edge area, particularly a corner area, of the underfloor heating. This facilitates, for example, the placement of the steam outlet opening and / or an electrical contact in an area laterally above the unheated zone, especially on a side wall bordering the corner area.

[0043] Furthermore, it is a further development that at least one projection extending into the receiving space and lengthening the distance between the two electrical contacts is present between them. This projection may, in particular, be designed as a transverse wall. This lengthens the electrical creepage distance between the two contacts, which can be formed, for example, by a thin coating of water-absorbing lime. The extended creepage distance improves the reliable detection of a short circuit caused by contact with the liquid. This design can be used regardless of whether the surface heating system has at least one unheated zone and whether at least one electrical contact is located above an unheated zone, and thus also represents an independent inventive concept.However, this combination is particularly preferred because, above the calmed zone, the probability of water splashing onto the inside of the housing between the contacts is low, and therefore the protrusion maintains a significant improvement in detection capability during operation.

[0044] The task can also be accomplished using a steam treatment device, in particular a steam cooker, with an evaporator as described above. The steam treatment device can be designed analogously to the method and offers the same advantages.

[0045] It is further defined that a steam treatment appliance is a device for treating food, in particular a cooking appliance. The steam treatment appliance has a food treatment chamber that can be filled with steam from the evaporator. The steam treatment appliance may be a standalone unit or a combination unit, in particular one comprising an oven with steam cooking functionality. Such an oven may be a standalone unit or an oven / cooktop combination (range). The oven may, in particular, be a conventional oven with a steam treatment function.

[0046] It is also a further development that the steam treatment device is a household appliance, e.g., in the sense of "white goods". Besides being used in a food preparation appliance, the evaporator may also be used, for example, in irons, coffee machines, cleaning equipment, or washing machines.

[0047] The evaporator may be located inside the food handling room, e.g. on the wall or floor, or it may be located outside the food handling room.

[0048] It is also a further development that the steam treatment device has a filling device for filling the evaporator and / or an emptying device for emptying the evaporator. This enables particularly precise dosing of liquid or effective emptying of the receiving chamber.

[0049] It is a further development that the filling and emptying units are separate functional units. This allows the conveying characteristics to be precisely tailored to the respective purpose. It is also a design feature that the filling and emptying units each have their own pumps.

[0050] It is a further development that the filling and emptying systems are fluidically separated from each other and, in particular, are connected to fluidically separated fluid supply lines. This allows, for example, the separation of a fresh water area from a wastewater area.

[0051] Alternatively, a filling and emptying device may be implemented as a single combined filling and emptying unit, e.g., with or as a single pump. Filling and emptying can then be achieved by appropriately positioning one or more valves within a piping system that is at least partially interconnected for the liquid.

[0052] It is a further development that the evaporator is operated by a process with at least the following steps: (i) filling the evaporator at least to the upper fill level; (ii) emptying the evaporator using a draining device; (iii) starting a timer when the upper fill level is undershot; (iv) switching on the evaporator heater when the upper fill level is undershot; (v) stopping the timer when overheating of the heater is detected; and (vi) calculating the flow rate during emptying the evaporator from the emptying time determined by the timer. This further development has the advantage that it can prevent the draining device from running dry without additional sensors (e.g., pressure or flow meters) and is therefore simple and inexpensive.This, in turn, can extend the service life of the emptying device and prevent disruptive noises from the emptying device during normal operation. This method also allows the use of a particularly cost-effective emptying device with higher tolerances for its conveying capacity.

[0053] In step (i), the evaporator's receiving chamber is filled with liquid at least to its predetermined fill level. The level detector determines whether the predetermined fill level has been reached. Then, in step (ii), the emptying device is activated to empty the evaporator or its receiving chamber. If, in step (iii), the level detector detects that the liquid in the receiving chamber has fallen below the upper fill level, the timer is triggered, for example, at a start time t0. The start time t0 corresponds to the moment when the liquid level has just fallen below the upper fill level. Since the deviation from the upper fill level is very small at this point, the start time t0 corresponds to the upper fill level with high accuracy.Switching on the heater in step (iv) ensures that the heater is at operating temperature, or at least close to it, when the emptying device has emptied the evaporator or its receiving chamber (possibly down to small puddles of liquid at the bottom of the receiving chamber). However, emptying the evaporator or its receiving chamber causes the heater to overheat, which is detected by the overheat detector. Since the overheat detector typically responds quickly, the final time t1, at which the heater overheating is detected, corresponds with sufficient accuracy to the time at which the evaporator or its receiving chamber was emptied. In step (v), the time measurement is stopped at this final time t1. Consequently, the emptying time Δt is calculated as the difference between t1 and t0.This draining time Δt takes into account a multitude of otherwise difficult-to-predetermine boundary parameters that influence the flow rate of the draining device. By using this draining time Δt, system-related tolerances can be identified and accounted for. In the case of a draining device in the form of or with a pump, the draining time Δt may also be referred to as the "pumping time." In step (vi), a delivery rate for emptying the evaporator or its receiving chamber is determined from the draining time Δt. This comparatively precise determination of the delivery rate during draining prevents the draining device, and especially the pump, from running dry, even if the draining device is then operated on a timer.

[0054] It is a further development that step (i) includes filling the evaporator beyond the predetermined detectable fill level. This ensures that the transition between "full evaporator" (predetermined, in particular upper, fill level reached) and "no longer full evaporator" (predetermined fill level fallen below) is particularly reliably detectable and, for example, hysteresis effects due to liquid adhesion, etc., are excluded. To prevent liquid from escaping from a vapor outlet opening of the evaporator, the upper fill level is preferably located at a distance below a lower edge of the vapor outlet opening. Step (i) may, for example, include filling the evaporator for a predetermined period of time after the upper fill level has been detected.

[0055] It is also a further development that step (iv) includes switching on the heater immediately when the upper fill level is undershot. This ensures with particular reliability that the heater has reached its normal, high temperature by the time the evaporator or its receiving chamber has been emptied. The volume reduction of the liquid in the evaporator due to vapor formation is typically negligible.

[0056] Furthermore, it is an improvement that step (iv) includes switching on the heater with a defined delay after detecting that the predetermined fill level has been undershot. This ensures that a heater sufficiently heated for carrying out the procedure with an empty evaporator is still available, but now with reduced power consumption.

[0057] It is a further development that the detection of overheating of the heater in step (v) triggers a shutdown of the heater. The detection of overheating may therefore constitute part of a safety shutdown routine to protect the evaporator from damage or even destruction. It is also a further development that the calculation of the delivery rate, Le, during emptying in step (vi) involves dividing the liquid volume, V, of the evaporator or its receiving chamber when filled to the predetermined fill level by the emptying time, Δte, and thus, in particular, Le = V / Δte (1) applies.

[0058] It is a further education course that Le = [(V + A) / (Δte + B)] + C (2) This applies, where A, B, and C are specific numerical values, determined in particular by calculation and / or experimentally, especially so-called "offsets." Each of the numerical values ​​may be negative, positive, or zero. These numerical values ​​may be used to make a correction, determined in particular experimentally, to the parameter added to them. For example, the numerical value B may correct the time required for emptying, e.g., the magnitude of a time lag between emptying the emergency storage area and the heating system overheating.

[0059] Furthermore, it is a further development that the following steps follow step (vi): (a) filling the evaporator at least to the upper fill level; (b) determining the time required to fill to the upper fill level; and (c) calculating the delivery rate during filling by dividing the liquid volume of the evaporator (especially at a predetermined fill level) by the time required to fill (to this predetermined fill level). This design can be used, in particular, as a safety feature of the steam treatment device. It takes advantage of the fact that, after step (vi), the evaporator's receiving chamber no longer contains any liquid. Residues or puddles are typically evaporated by the heating element. Thus, a particularly precise determination of the delivery rate during filling is possible.

[0060] This is a further development of the principle that – particularly in a steam treatment plant – filling of the evaporator is stopped when a safety threshold, determined based on the filling rate, is reached or exceeded. For example, filling might be switched off after a predetermined time threshold has been exceeded. This allows filling of the evaporator to be interrupted in the event of a failure of the level detector. This, in turn, prevents flooding of the steam treatment unit and potentially also water damage outside the unit.

[0061] It is also important to note that the procedure is only performed during abnormal operation of the steam treatment unit, when it is not used for steam treatment of food. This abnormal operation may occur during the initial commissioning of the steam treatment unit, after a power outage, following certain maintenance programs, as part of a descaling program, and / or in connection with a functional test of the draining device.

[0062] The steam treatment device may, in particular for carrying out the process, include an overheat detector for detecting overheating of the heating element, a timing device, and / or a computing device. The timing device may, in particular, be a timer integrated into the steam treatment device. The computing device may be a separate computing device. For a simple and cost-effective design, it is advantageous if a device already commonly present in the steam treatment device, such as a central control unit, can be used as the computing device. The computing device may, in particular, be designed as an electronic circuit, for example, comprising a microprocessor, an ASIC, an FPGA, etc.

[0063] Another design option involves using the surface heating system as an overheating detector. For example, the surface heating system might have a temperature-dependent, electrically conductive layer. In this case, the temperature of the surface heating system, and consequently overheating, can be determined by measuring conductivity or a corresponding electrical parameter, e.g., by comparing it to a predetermined threshold value.

[0064] The properties, features and advantages of this invention described above, as well as the manner in which they are achieved, will become clearer and more easily understood in connection with the following schematic description of an exemplary embodiment, which will be explained in more detail in conjunction with the drawings.

[0065] Fig. Figure 1 shows an exploded view in oblique view of an evaporator according to the invention;

[0066] Fig. Figure 2 shows a sectional view of a steam treatment device with the evaporator;

[0067] Fig. Figure 3 shows a section of the assembled evaporator in a side view as a sectional representation;

[0068] Fig. Figure 4 shows a section in side view of a part of Fig. 3 in the area of ​​a side edge.

[0069] Fig. Figure 1 shows an exploded view of an evaporator in oblique view. 1 , which is for example suitable for use in a household steam cooker H (see Fig. 2) is provided for, e.g. in a stand-alone steam cooker or an oven with a steam cooking function.

[0070] The evaporator 1 a floor section 2 with a bottom-side area 3 and an adjoining, projecting circumferential edge on the front 4 up. The ground-side area 3For example, it has a flat basic shape with a rectangular outer contour A and rounded edges. In the bottom area 3 There are at least two openings, including one water passage opening. 5 and an insertion opening 6 for making an electrical connection. From the edge 4 There are several spring-loaded locking tabs. 7 upwards. In addition, at least one fastening tab extends towards the rear. 8 off, for example for screwing onto the household steam cooker H.

[0071] The ground-side area 3 The entire interior surface is sealed against an electrically operated surface heating system. 9 covered. The underfloor heating 9 It has an electrical connection on its back. 10 on, which through the through-hole 6 protrudes. The underfloor heating 9 It also has a hole11 up, which is identical to the water inlet opening 5 lies. Through the hole 11 and the water inlet opening 5 Water can be added and drained.

[0072] The underfloor heating 9 It can be heated over its entire surface and may, for example, have an electrically conductive front side facing the liquid. 9a exhibit the underfloor heating 9 It can also have a layer (e.g., internal) that becomes electrically conductive when a predetermined temperature threshold is exceeded (not shown). A significant change in electrical conductivity or resistance, or in the current flowing through this layer, indicates that the threshold temperature has been reached and thus that overheating has occurred. The threshold temperature might be, for example, around 200 °C. Surface heating 9It therefore optionally serves simultaneously as an overheating detector to detect overheating.

[0073] The underfloor heating 9 points to its front side when viewed from above 9a a non-angular outer contour, namely that of a rectangle with circularly rounded corners. A narrow side edge. 27 the underfloor heating 9 runs continuously or continuously along this outer contour.

[0074] The underfloor heating 9The system optionally features at least one heated or heated section, or at least one heated zone B1, and at least one unheated section, or at least one unheated zone B2. While at least one heating conductor (e.g., in a meandering pattern) is installed in heated zone B1, this is absent in unheated zone B2. When switched on, the temperature of heated zone B1 is above a predetermined temperature T, while the temperature of unheated zone B2 is below the predetermined temperature T. In particular, this may cause the water in heated zone B1 to become highly agitated, possibly even boiling, while the water, or rather its surface, remains comparatively calm in unheated zone B2. Here, unheated zone B2 occupies at least one corner of the surface heating system. 9 a.

[0075] The underfloor heating 9 and the lid 13Together they form a receiving chamber R for water. The surface heating 9 This forms a floor or a floor-side wall of the recording room R.

[0076] On the bottom part 2 sits above a circumferential seal 12 a domed or bowl-shaped lid part 13 open. The lid part 13 has several locking tabs on the outside 14 on, which are used for intervention with the locking tabs 7 are provided and a simple snap-fit ​​connection between the base part 2 and the lid part 13 allow. The lid part 13 points in its bottom part 2 spaced apart opposite upper wall 15 two holes (not shown) for the insertion of electrically conductive contact pins 16 , especially metallic pins. The contact pins 16 They are freely located in recording room R.

[0077] The two contact pins16 They end on the underside, particularly at the same height, and are connected by the recording space R or... 2 , 13 Standing water electrically connected when the water reaches a predetermined (especially "upper") fill level L1 (see also Fig. 3) reached. This electrical short circuit can be detected to determine the predetermined fill level L1, e.g. by a control device. 24 (see also Fig. 2) The control unit 24 might be connected to the contact pins 16 Apply an alternating low voltage to eliminate electrolytic effects.

[0078] The evaporator 1 When the predetermined fill level L1 is reached, it is filled with a volume V of water.

[0079] The contact pins 16 are located above the unheated zone B2 of the underfloor heating system 9, in order to enable a more reliable determination of a predetermined upper fill level L1, especially one that is little affected by a disturbed water surface.

[0080] On a surrounding side wall 17 of the lid 13 near the top wall 15 There is a steam outlet. 18 The steam outlet, shown here as an example of a nozzle-like design, 18 It may, for example, be connected to a hose for conveying the steam generated by the evaporator into the food treatment chamber S of the household steam cooker H. The steam outlet 18It is positioned above the unheated zone B2 to prevent small water droplets generated by agitated water in the heated zone B1 from being carried along by the steam flow. This improves the steam quality. The fewer water droplets contained in the steam flow, the higher its energy content and therefore its efficiency. Furthermore, it prevents the food being cooked in the food handling chamber S from being damaged by the water droplets.

[0081] Fig. Figure 2 shows a sectional view of a household steam cooker H with the evaporator. 1 out of Fig. 1. The household steam cooker H has a fresh water connection. 20 on, which has a filling pump serving as a filling device 21 with the water inlet opening 5 of the evaporator 1 is connected. The evaporator 1 is with its water inlet opening 5furthermore, a drain pump serving as a draining device 22 with a wastewater connection 23 of the evaporator 1 connected. Operation of the filling pump 21 and the drain pump 22 is via a control unit 24 controlled. The control unit 24 It also works with the contact pins 16 connected and can cause a short circuit at the contact pins 16 notice.

[0082] The control unit 24 This could be, for example, a central control unit of the household steam cooking appliance H, which might also control other functions, such as the operation of the underfloor heating. 9 of the evaporator 1 and / or at least one heating device (not shown) for heating a food processing room S.

[0083] The water inlet opening 5is shown here in the form of two spatially separated water inlet and water outlet openings, but may be designed as in Fig. 1. be a common water passage opening (i.e., a combined water inlet and water outlet opening).

[0084] During operation of the evaporator 1 For steaming food, the steam outlet is used. 18 of the evaporator 1 Steam is introduced into the possibly preheated food preparation chamber S of the household steam cooker H. This is done first using the filling pump. 21 Water was pumped into recording chamber R until a short circuit occurred between the contact pins. 16 achieving the in Fig. The predetermined fill level L1 shown in Figure 3 is detected. Upon detection of the short circuit and thus the predetermined fill level, the filling pump is activated. 21The system is stopped immediately or after a defined period of time (e.g., between 1 and 3 seconds). The surface heating is then activated. 9 This causes the water to evaporate, thus lowering the water level. When the water level drops below level L1, the short circuit caused by the water is eliminated, and the control device... 24 reactivates the filling pump 21 for filling the intake chamber R with water, etc. Typically, the filling pump is used for this purpose every minute. 21 Activated two to three times for five to seven seconds each time. The evaporator's construction 1 enables particularly rapid and immediate evaporation of the filled water, for example through large-area energy input via surface heating. 9 and a low predetermined fill level L1 in the range of millimeters, e.g. between eight and ten millimeters, preferably 9 mm.

[0085] What's next in Fig. 3 shown, protrude from the upper wall 15 of the lid 13 Interior partition walls 25 and 26 into recording room R. At least one of the partition walls 25 and 26 crosses an area between the two contact pins 16 and thereby extends the distance between the contact pins 16 This creates an electrical creepage distance between the two contact pins. 16 extended, which is evident, for example, from a fine coating on the inside of the lid. 13 can form from water-absorbing lime.

[0086] Fig. Figure 3 also shows the structure of the underfloor heating in more detail. 9 as well as the arrangement of the seal 12 Underfloor heating 9 has a support plate on the upper side 28 on, which forms the bottom wall of recording room R and whose front 9apoints into recording room R. The support plate 28 It might be, for example, a sheet steel part whose front 9a for example, whether it is bare or scaled. The carrier plate 28 It may have a thickness of between one and two millimeters, but is not limited to that.

[0087] On one side of the carrier plate 28 There are several thick-film heating conductors 29 , namely from the carrier plate 28 separated by an insulating layer (not shown). The thick-film heating conductors 29 They do not extend below the unheated zone B2. A covering layer (not shown) may also be applied to the thick-film heating conductors from below. 29 and, if necessary, the exposed areas of the insulation layer must be covered. Such a surface heating system 9 It may have a thickness of between one and two millimeters, but is not limited to that.

[0088] For example, two thick-film heating conductors 29 Available are units which can be operated individually or together with a nominal power of 400 W or 800 W.

[0089] Both thick-film heating conductors may be suitable. 29 The heated zone B1 is heated almost across its entire surface. The two thick-film heating elements 29 They might, for example, be intertwined in a meandering pattern.

[0090] The seal 12 is a double seal with an upper sealing element 12a and a matching lower sealing element 12b designed. The sealing elements 12a and 12b run analogously to the side edge 27 The lower sealing element 12b seals a gap between the bottom part 2 , especially its edge 4 , and a reverse side of the carrier plate 28 off. The upper sealing element 12aseals a gap between the front 9a the carrier plate 28 and the lid part 13 off. In particular the upper sealing element. 12a prevents liquid from the receiving chamber R from reaching the bottom part 2 can get there. So while the lid part 13 , the carrier plate 28 and the upper sealing element 12a Parts that come into contact with liquid and therefore should be food-safe need the base part. 2 not being food-safe. The bottom part 2 It may consist in particular of a flame-retardant plastic, which has a higher elasticity than the food-grade plastic of the lid part. 13 .

[0091] How more precisely in Fig. 4 is listed as the side edge 27 The two sealing elements are convex or domed in cross-section. 12a and 12b the seal12 lie on the convex side edge 27 on. Due to its convex shape, the lid part 13 and the side edge 27 a holding area for the upper sealing element 12a , whereby the upper sealing element 12a can be held slightly taut.

[0092] Of course, the present invention is not limited to the embodiment shown.

[0093] In general, "ein", "eine", etc. can be understood to mean singular or plural, especially in the sense of "at least one" or "one or more", etc., unless this is explicitly excluded, e.g. by the expression "exactly one", etc.

[0094] A numerical specification can also include exactly the specified number as well as a normal tolerance range, unless this is explicitly excluded. Reference symbol list 1 evaporator 2. Bottom part of the evaporator 3 Ground-side area 4 rand 5 Water inlet opening 6. Feedthrough opening 7 Rastlatsche 8 Mounting tab 9 Underfloor heating 9a Surface of the underfloor heating 10 Electrical connection 11 holes 12 Seal 12a upper sealing element 12b lower sealing element 13 Lid part 14 Resting nose 15 Top wall of the lid 16 contact pins 17 Side wall of the lid 18 Steam outlet 20 Fresh water connection 21 Filling pump 22 Drain pump 23 Wastewater connection 24 Control unit 25 Interior partition wall 26 Interior partition wall 27 Side edge of the surface heating 28 Carrier plate 29 Thick-film heating conductors A Outer contour B1 heated zone of the underfloor heating B2 unheated zone of the underfloor heating H Household steam appliance L hole L1 predetermined fill level R Recording room S Food Treatment Room Temperature Volume QUOTES INCLUDED IN THE DESCRIPTION

[0095] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0096] DE 102006029578 A1

[0002] DE 102009044053 A1

[0003] DE 102010029307 A1

[0004] WO 2009 / 007456 A2

[0005] EP 0471342 A2

[0006] DE 102009055146 A1

[0007] DE 19741881 A1

[0008] EP 1658798 A1

[0009]

Claims

[1] Evaporator ( 1 ) for a steam treatment device (H), comprising – a receiving chamber (R) for liquid to be evaporated with a floor-side surface heating system ( 9 ), which has a circumferential side edge ( 27 ) shows, characterized by that – the side edge ( 27 ) is at least partially convex in cross-section. [2] Evaporator ( 1 ) according to claim 1, characterized by that – the underfloor heating ( 9 ) a support plate that limits the recording space (R) 28 ) has at least one heating conductor track arranged on the side facing away from the receiving space (R) and – the carrier plate ( 28 ) is at least partially convex in cross-section. [3] Evaporator ( 1 ) according to any of the preceding claims, characterized by that the evaporator ( 1 ) a seal ( 12) which has a side edge ( 27 ) is lying down. [4] Evaporator ( 1 ) according to claim 3, characterized by that the seal ( 12 ) a double seal with two sealing elements arranged one above the other ( 12a , 12b ) is which is located on the top or bottom of the side edge ( 27 ) lie down. [5] Evaporator ( 1 ) according to one of claims 3 to 4, characterized by that the seal ( 12 ) using the side edge ( 27 ) is tense. [6] Evaporator ( 1 ) according to any of the preceding claims, characterized by that a shape of the side edge ( 27 ) is cornerless in top view. [7] Evaporator ( 1 ) according to any of the preceding claims, characterized by that the evaporator has a housing ( 2 , 3 ) with a base part ( 2 ) and a lid part ( 13) and the receiving space (R) is defined by the lid part ( 13 ) and the underfloor heating ( 9 ) is formed and the bottom part ( 2 ) and the lid part ( 13 ) made of different materials. [8] Evaporator ( 1 ) according to claim 7, characterized by that the bottom part ( 2 ) is made of a non-food-safe material and the lid part ( 13 ) is made of a food-safe material. [9] Evaporator ( 1 ) according to one of claims 7 or 8, characterized by that the bottom part ( 2 ) is made of flame-retardant material and / or is made of a more elastic material than the lid part ( 13 ). [10] Evaporator ( 1 ) according to any of the preceding claims, characterized by that the underfloor heating ( 9 ) several independently operable planar heating conductor tracks ( 29 ) exhibits. [11] Evaporator (1 ) according to claim 10, characterized by that at least two of the heating conductor tracks ( 29 ) have different nominal power outputs. [12] Steam treatment appliance (H), in particular steam cooking appliance, comprising at least one evaporator, characterized by that the evaporator is an evaporator ( 1 ) according to one of the preceding claims.

Images