DE102014210669A1 - Evaporator - Google Patents

Abstract

An evaporator (1) for a steam treatment device (H), in particular domestic appliance, has a receiving space (R) for liquid to be evaporated with a bottom-side surface heating (9), which has a peripheral side edge (27), wherein the side edge (27) at least is formed in sections convex in cross section. A steam treatment device (H), in particular Dampfgargerät, has at least one such evaporator.

Description

The invention relates to an evaporator for a steam treatment device, comprising a receiving space for liquid to be evaporated with a bottom-side surface heating. The invention further relates to a steam treatment apparatus with such an evaporator. The invention is particularly advantageously applicable to steam cooking appliances, as individual appliances or as combination appliances. The invention is particularly advantageously applicable to household appliances.

DE 10 2006 029 578 A1 discloses a steamer as evaporator device with an evaporator for water, wherein the evaporator has a heatable water tank and connected to the water tank in the manner of communicating tubes detection area for detecting the level of the water tank. The detection area is vertically tubular and has at least one sensor for detecting the filling level.

DE 10 2009 044 053 A1 discloses a steam generator for a household appliance with an evaporator space to which a connection for the supply of water and at least one connection for the discharge of steam are connected in flow conduction and with a heated and with respect to the horizontal in installation position obliquely arranged evaporator surface, above the evaporator space for the generated steam is formed and in which a steam flow is formed in the direction of the steam outlet, wherein the water supply to the evaporator surface via a arranged in the supply line valve or a pump is controlled or regulated and the water level above the evaporator surface detected by a level monitoring device and for the control of Water supply to the evaporator surface is evaluated. In order to design a steam generator for a household appliance with low construction volume and high heating power or steam power, which is designed for continuous steam generation and in which a drying of the heater is reliably avoided, the level monitoring device is arranged in the region of the evaporator chamber of the steam generator, in the only a slight to no flow intensity of the vapor forms over the evaporator surface.

DE 10 2010 029 307 A1 discloses a household appliance with a container for holding liquids, which is set up in particular for storing a detergent and for automatically dosing the same detergent. An electrical measuring device is provided which measures a filling level of the storage container. The measuring device has two measuring electrodes spaced apart from one another in the container and a circuit arrangement coupled to the measuring electrodes, which is designed to apply an alternating voltage between the measuring electrodes and at least one measured variable correlated with the alternating voltage and with a conductance of a medium located between the measuring electrodes measure up. Also disclosed is a corresponding level measurement method.

WO 2009/007456 A2 discloses a device for adding water for steam generation in a cooking appliance, with an evaporator vessel, in which water can be supplied depending on the level of the water contained in the evaporator vessel, and electrodes, with which the level of water in the evaporator vessel is detectable, wherein an inner wall of the evaporator vessel is at least partially formed of an electrically conductive material and this part of the inner wall is a first electrode.

EP 0 471 342 A2 discloses an arrangement in which two measuring electrodes are arranged 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 jacket. The measuring electrodes detect resistance values of the ice and / or the water which is located between the electrodes and the container inner wall. For cooling the water, regardless of its chemical-physical composition, the resistors corresponding potentials are formed, which are supplied to a differential amplifier. Depending on a size comparison of both resistance values, a refrigeration unit acting on the container contents is switched on or off.

DE 10 2009 055 146 A1 discloses a steam generating system for a domestic appliance, in particular a steam cooking appliance, which has at least one emptying liquid reservoir, an evaporator which can be supplied with liquid from the liquid reservoir via at least one supply line and at least one pump for moving the liquid, the liquid being conveyed by means of the at least one pump in the direction of the Liquid reservoir is recoverable. A method is used to operate the steam generation system.

DE 19741881 A1 discloses a domestic appliance for steam cooking at approximate ambient pressure, which has a cooking chamber, a steam generator with a heater and a temperature sensor, which is connected to a control device for controlling the heating device of the steam generator. To create a household appliance for steam cooking at approximate ambient pressure, in which exclusively with steam is cooked, which should be installed flexibly in the kitchen, and regardless of conditions at the installation, the steam generator with the heater is arranged separately outside the cooking chamber. A water tank is preferably arranged in the vicinity of the steam generator and the temperature sensor in the cooking chamber.

EP 1 658 798 A1 discloses a steam generator having a housing for forming a steam generating chamber, the housing having a steam outlet opening. A heating plate is held by the housing within the steam generating chamber. A water inlet valve is in fluid communication with the housing for selectively supplying water into the steam generating chamber, thereby directing water to the hot plate for conversion to steam. The heating plate forms a bottom wall of the steam generating chamber and is configured to have an elevation.

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

This object is achieved according to the features of the independent claims. Preferred embodiments are in particular the dependent claims.

The object is achieved by an evaporator for a steam treatment device, comprising a receiving space for liquid to be evaporated with a bottom-side surface heating, which surface heating has a peripheral side edge, the side edge at least partially convex in cross-section (or convex or arched outwards).

The convexity of the side edge facilitates easy sliding of the surface heater to a housing of the evaporator, which prevents mechanical stressing of the surface heater as it expands thermally (e.g., at power-up) on the housing. Also, such a seal between the surface heating and the housing easier to assemble. In addition, there is the advantage that the convex side edge is adapted to serve as a receiving area or holding area for a seal, so that the seal can thereby be biased by simple means. This in turn improves a secure fit of the seal under a relative movement of surface heating, seal and / or housing.

It is a development that the side edge or the side edge over its entire length or completely circumferentially convex. One of the receiving space facing side of the surface heating can also be referred to as the front, a side facing away from the receiving space as the back.

The floor-mounted surface heating has the advantage that the liquid located in the receiving space for generating steam in a simple manner over a large area and thus can be heated very quickly. A level of the liquid in the receiving space may be small, e.g. in the range of millimeters, e.g. between 8 and 10 millimeters, e.g. of 9 millimeters, which further supports rapid heating and allows a flat design. The surface heating thus preferably forms a bottom-side wall of the receiving space.

The receiving space for liquid to be evaporated may also be referred to as evaporator space or steam generating chamber. It is at least fillable with liquid, in particular water, and has at least one liquid inlet or liquid feed opening for this purpose. It also has at least one steam outlet opening for discharging the steam generated from the liquid with its aid. The receiving space may also be emptied of liquid. For this purpose, he may have an independent discharge opening, or the liquid is fed through the same opening and drained or emptied. The receiving space is preferably filled with fresh water, while possibly emptied liquid can be regarded as wastewater, for example.

It is an embodiment that the surface heating has a receiving space limiting support plate, at the receiving space facing away from back at least one Heizleiterbahn is arranged and a side edge or a side edge of the support plate is formed at least partially convex in cross section. This embodiment is compact and robust feasible.

The support plate may in particular be made of metal, e.g. a ferrous metal, e.g. made of stainless steel. The carrier plate may e.g. be a sheet metal part. The support plate may be a flat plate at least in the unheated state of the evaporator. The support plate may, for example, be bare or scalloped on its front side facing the receiving space. The support plate may alternatively be e.g. made of ceramic.

The support plate has a thickness to achieve a particularly low thermal inertia and thus high energy yield at the same time good heat spreading and high robustness between one and two millimeters, but is not limited thereto. Also, in such a thickness range, the side edge or the side edge can already form sufficiently precisely convex with simple means.

The at least one heating conductor, for example, may be a thin-film heating conductor or a thick-film heating conductor and serve as an electrical resistance heating element. In particular, a thick-film heating conductor can be produced particularly simply, inexpensively and in high quality and is still very space-saving. The at least one heating conductor may be fastened to the carrier plate, in particular in the case of an electrically conductive carrier plate, via an electrical insulating layer in order to prevent a short circuit.

The surface heating may be covered on its rear side facing away from the receiving space by a cover layer, e.g. as protection against mechanical stress. It is a development that the surface heating has a thickness between one and two millimeters.

It is still an embodiment that the evaporator has a seal which rests on the convex side edge. The convex side edge forms in a particularly simple manner, in particular together with the housing a receiving area or holding area for the seal. The seal may be laid along the side edge of the surface heating. The gasket may have an O-ring-like cross-sectional shape and material composition, but e.g. deviate in plan view from a circular ring shape. However, the type of seal is basically not limited, but may for example be designed as a flat gasket.

It is generally an embodiment that the seal is tensioned by means of the side edge, which ensures their correct fit even under thermal deformation of the surface heating. The seal may be held in particular by means of the housing and the side edge.

It is a further embodiment that the seal is a double seal with two superimposed sealing elements which rest on the upper side or the lower side on the side edge. This makes it possible to achieve a particularly secure seal. The two sealing elements may be the same or different, e.g. have an identical or different basic shape (in plan view). Each of the two sealing elements may be formed like a seal described above. The two sealing elements may be separate parts or related to each other.

It is yet a further embodiment that a shape of the side edge is free of corners in plan view. Thus, the shape of the side edge does not have any corners but is either continuously curved (e.g., circular or oval) or has alternately curved and straight sections with smooth transitions. Thus, a seal relative to the housing can be realized particularly cost-effectively and due to improved process reliability particularly reliable. It is a development that the shape of the side edge in plan view is a rectangular basic shape with rounded corners.

It is also an embodiment that the evaporator has a housing with a bottom part and a cover part and the receiving space is formed by the cover part and the surface heating and the bottom part and the cover part made of different material. It is exploited that the bottom part in contrast to the lid part does not come into contact with the water to be evaporated and the requirements of the two parts need not be the same. The housing is thus formed at least two pieces. In particular, the two parts may be made of different plastic. In particular, a seal can prevent the liquid from penetrating to or into the bottom part.

It is also an embodiment that the lid part consists of a food-safe material. The bottom part does not need to be made of a food-safe material. If a seal is present and can come into contact with the liquid to be evaporated, this advantageously also consists of a food-safe material. Thus, a use of often expensive food-safe material can be limited to a few parts.

It is a development that the bottom part consists of a flame-retardant material, which increases operational safety and improves flame retardancy. However, food grade plastic is typically not flame retardant.

It is still a development that the bottom part consists of a more elastic material than the cover part. This provides the advantage that attachment of the evaporator is facilitated via its bottom part to a household appliance. Also, a fixture, e.g. Locking, simplified by bottom part and lid part. In contrast, food plastic is generally comparatively brittle.

It is also an embodiment that the surface heating has a plurality of independently operable planar Heizleiterbahnen. This can be done in a simple way (eg with a constant heating current and / or with a fixed timing of the heating current) achieve a particularly accurate gradation of the introduced heating power.

It is also an embodiment that at least two of the Heizleiterbahnen have a different rated power or a different maximum power. Thus, a particularly accurate gradation of the introduced heating power can be achieved with a small number of Heizleiterbahnen.

For example, the different nominal powers may have multiple values, e.g. in the form n · L with L of a predetermined basic heating power and n of a natural number greater than zero, in particular the number of existing Heizleiterbahnen.

For example, n = 2 Heizleiterbahnen be present at a base heat output of L = 400 W, of which a first Heizleiterbahn has a rated power of 1 · L = 400 W and a second Heizleiterbahn a rated power of 2 · L = 800 W. They can be operated together with a heating power of 1200W.

However, the different nominal powers can also be staggered, for example, in the manner of a logarithmic series, for example in the form 2 ^(n-1) · L. In the case of four heating conductor tracks, the respective nominal power of the heating conductor tracks of 100 W, 200 W, 400 W or 800 W results at a base heating power of L = 100 W.

However, other values, in particular graduations, of nominal performance are possible.

It is a development that the evaporator has two exposed in the receiving space electrical contacts for determining a level in the receiving space, wherein the surface heating has at least one unheated zone and at least one electrical contact is disposed above an unheated zone. As a result, the electrical contacts are less exposed to an agitated surface of the liquid with activated surface heating and are triggered to a much lesser extent unintentionally even before reaching the predetermined level than above a heated or heated zone. In particular, the liquid can boil over a heated zone with formation of bubbles and / or strong turbulences, which causes the surface to become particularly turbulent. Nevertheless, a particularly simple and compact design can be maintained.

It is a further development that the exposed electrical contacts are parts of a fill level detector or a fill level determination device, which is also referred to below as a "short-circuit fill level detector". In particular, they can represent a sensor or sensory part of the level detector. An evaluation unit for evaluating (e.g., performing a threshold comparison) of a signal (e.g., voltage values) output from at least one of the contacts may be part of the evaporator or may be located outside the evaporator. The evaluation unit may e.g. a circuit such as a microprocessor, an ASIC, an FPGA, etc. include. However, an evaluation unit may also be dispensed with. For example, a switch may be switched by a voltage signal output by a sensor, e.g. an electronic switch like a transistor or an electrical switch like a relay.

It is also a development that the surface heating has an electrically conductive surface facing the liquid and the surface heating, in particular this surface, forms one of the two electrical contacts of the short-circuit fill level detector. This makes it possible to dispense with a second dedicated or separate electrical contact. Another advantage is that the liquid is not stirred up at the surface heating and thus results in a more reliable determination of the achievement of the predetermined level.

It is also a further development that the two electrical contacts inserted into the receiving space on the ceiling side are electrically conductive pins ("contact pins"). As a result, they are easily removable or exchangeable and also not as often exposed to contact with the liquid, which for example reduces deposition of substances contained in the liquid and possibly a chemical corrosion.

It is also a development that at least one of the electrical contacts can be arranged on a side wall in the receiving space. For example, an electrically conductive pin may be guided through a side wall into the receiving space. Also, an inside of the evaporator may be there with an electrically conductive layer or the like. be provided.

It is also a development that a steam outlet or the steam outlet opening is arranged above the unheated zone. This provides the advantage that no small drops of water are entrained with the vapor stream, which, however, typically form on the churned-up water above the heated zone. This increases a steam quality. The less water droplets are contained in the vapor stream, the higher its energy content and thus the efficiency. In addition, will Prevents the food or food in the food treatment room is damaged by the water droplets.

It is still a development that the unheated zone corresponds to an edge area, in particular corner area, the surface heating. This facilitates, for example, an arrangement of the steam outlet opening and / or an electrical contact in an area laterally above the unheated area, in particular on a corner wall bounding the lateral wall.

It is also a further development that between the two electrical contacts at least one projecting into the receiving space, extending a distance between the two electrical contacts projection is present. The projection may in particular be designed as a transverse wall. As a result, an electrical creepage distance between the two contacts is extended, which can form, for example, by a fine coating of water-absorbing lime. The extended creepage distance improved a reliably detectable short circuit due to contact with the fluid. This embodiment may be used regardless of whether the surface heating has at least one unheated zone and at least one electrical contact is disposed above an unheated zone, and thus represents an independent inventive idea. However, the combination is particularly preferred because above the calm zone the likelihood of water splashes on the inside of the housing between the contacts is low and therefore the projection maintains a significant improvement in detection capability during operation.

The object is also achieved by a steam treatment device, in particular Dampfgargerät, with an evaporator as described above. The steam treatment apparatus can be formed analogously to the method and has the same advantages.

It is still a development that the steam treatment device is a device for the treatment of food, in particular a cooking appliance. For this purpose, the steam treatment device has a food treatment space which can be filled with steam from the evaporator. The steam treatment device may be a stand-alone device or may be a combination device, in particular comprising a furnace with Dampfgarfunktionalität. Such an oven may be a single appliance or an oven / hob combination. The oven may in particular be an oven with a steam treatment function.

It is further a development that the steam treatment device is a household appliance, e.g. in the sense of "white goods". Except in a food treatment device, the evaporator may be used for example in irons, coffee machines, cleaning appliances or washing machines.

The evaporator may be housed in the food processing room, e.g. wall side or bottom side, or may be housed outside the food treatment room.

It is also a development that the steam treatment device has a filling device for filling the evaporator and / or an emptying device for emptying the evaporator. This allows a particularly precise dosing of liquid or an effective emptying of the receiving space.

It is still a further development that the filling device and the emptying device are different functional units. As a result, the conveying properties can be adapted particularly precisely to the respective purpose. Thus, it is also an embodiment that the filling device and the emptying device have or are respective pumps.

It is still a further development that the filling device and the emptying device are fluidically separated from one another and, in particular, are connected to fluid supply lines which are fluidly separated from one another. For example, a separation of a fresh water area from a wastewater area can be achieved.

Alternatively, a filling device and emptying device may be implemented as a single combined filling and emptying device, e.g. with or as a single pump. The filling and emptying can then be achieved by appropriate placement of one or more valves of an at least partially connected line system for the liquid.

It is a development that the evaporator is operated by means of a method with at least the following steps: (i) filling the evaporator at least up to the upper level; (ii) emptying the evaporator by means of an emptying device; (iii) starting a time measurement when the upper level is exceeded; (iv) switching on a heater of the evaporator when the upper level is exceeded; (v) stopping the time measurement if overheating of the heater is detected; and (vi) calculating a discharge rate at emptying of the evaporator from a time duration for emptying determined by the time measurement. This development has the advantage that it without additional sensors (eg printing or Flow meter) and thus easy and inexpensive can prevent emptying an emptying to empty the evaporator. This, in turn, a life of the emptying device can be extended, and it can disturbing noise of the emptying device are prevented during idling in normal operation. Also, this method allows the use of a particularly cost-emptying with higher tolerances of their capacity.

By step (i), a receiving space of the evaporator for the liquid is filled at least to its predetermined level. The detection of whether the predetermined level has been reached is done by means of the level detector. Then, in step (ii), the emptying means for emptying the evaporator or its receiving space is put into operation. If it is detected in step (iii) by means of the filling level detector that the liquid in the receiving space has fallen below the upper level, the time measurement is triggered, e.g. at a start time t0. The start time t0 thus corresponds to the time at which the level has just fallen below the upper level. Since the deviation from the upper level is very small at this time, the start time t0 corresponds to the upper level with high accuracy. Turning on the heater in step (iv) will cause the heater to be at operating temperature or at least near operating temperature if the draining device has drained the evaporator or its receiving space (possibly down to a small pool of liquid at the bottom of the receiving space). With the emptying of the evaporator or its receiving space, however, the heater overheats, which is detected by the overheating detector. Since the overheat detector typically responds quickly, the end time t1 at which the overheating of the heater is detected corresponds with sufficient accuracy to the time at which the evaporator or its receiving space has been emptied. In step (v), at the end time t1, the time measurement is stopped. Consequently, an emptying period Δt results from a difference t1-t0. This emptying period .DELTA.t takes into account a variety of otherwise difficult to predeterminable edge parameters that affect the flow rate of the emptying device. By using this emptying period Δt, the system-related tolerances can thus be recorded and taken into account. In the case of an emptying device in the form of or with a pump, the emptying time period Δt may also be referred to as "pumping down time". In step (vi), a delivery rate when emptying the evaporator or its receiving space from the emptying time period or time duration for emptying Δt is determined. Due to the comparatively precisely determined delivery rate during emptying, idling of the emptying device, in particular the pump, can be avoided, even during a time-controlled operation of the emptying device.

It is still a further development that step (i) comprises filling the evaporator beyond the predetermined detectable level. This ensures that the transition between "full evaporator" (predetermined, in particular upper, level reached) and "no longer full evaporator" (predetermined level falls below) is particularly secure and detectable, for example. Hystereffekte by a fluid adhesion, etc. are excluded. In order to prevent liquid from escaping from a vapor outlet opening of the evaporator, the upper filling level is preferably spaced below a lower edge of the steam outlet opening. Step (i) may be e.g. filling the evaporator for a predetermined period of time after detecting the reaching of the upper level.

It is also a further development that step (iv) comprises switching on the heating immediately when the upper filling level is reached. This ensures that the heating has been heated to normal, high temperature, when the evaporator or its receiving space has been emptied. A volume reduction of the liquid present in the evaporator by a vapor development is typically negligible.

It is also a development that step (iv) comprises switching on the heating with a defined delay after determining the undershooting of the predetermined filling level. As a result, a heater sufficiently heated for the purpose of carrying out the method with the evaporator deflated can still be provided, but now with reduced power consumption.

It is a further development that the determination of the overheating of the heater in step (v) triggers a shutdown of the heater. Thus, the detection of overheating may be part of a safety shutdown routine to prevent the evaporator from being damaged or even destroyed. It is also a development that comprises calculating the delivery rate, Le, when emptying in step (vi) by dividing a liquid volume, V, the evaporator or its receiving space when filled at the predetermined level with the duration for emptying, .DELTA.te, in particular Le = V / Δte (1) applies.

It is a continuing education that Le = [(V + A) / (Δte + B)] + C (2) where A, B and C are specific, in particular by calculation and / or experimentally determined numerical values, in particular so-called "offsets". Each of the numerical values may be negative, positive or zero. These numerical values may be used to correct, in particular experimentally determined, the added parameter. Thus, by means of the numerical value B, a correction of the time duration required for emptying may be undertaken, for example, the magnitude of a time offset between emptying the exception space and overheating the heater.

It is also a further development that the following further steps follow at step (vi): (a) filling the evaporator at least up to the upper level; (b) determining a time to fill up to the upper level; and (c) calculating a flow rate at filling by dividing a liquid volume of the evaporator (in particular, at a predetermined level) with the time for filling (up to this predetermined level). This embodiment can be used in particular as a safety feature of the steam treatment device. It makes use of the fact that after step (vi) the receiving space of the evaporator no longer contains any liquid. Residues or pools have typically been evaporated by the heater. Thus, a particularly accurate determination of the capacity during filling is possible.

It is a development of this that - especially in a steam treatment operation of the evaporator - the filling is stopped when a certain based on the flow rate during filling certain safety threshold is reached or exceeded. For example, filling may be switched off after exceeding a predetermined time threshold value. As a result, filling of the evaporator can be interrupted in the event of a failure of the fill level detector. This in turn prevents flooding of the steam treatment device before and possibly also a water damage outside of the device.

It is also a further development that the method is carried out only in an abnormal operation of the steam treatment apparatus, which does not steam treatment of a feed is performed. This abnormal operation may be performed during a first startup of the steam treatment device, after a network return, following certain maintenance programs, as part of a descaling program and / or in connection with a functional test of the emptying device.

The steam treatment device may have, in particular for carrying out the method, an overheating detector for detecting an overheating of the heater, a time measuring device and / or a calculating device. The time measuring device may in particular be a "timer" present in the steam treatment device. The calculation device may be an independent calculation device. It is advantageous for a simple and inexpensive design, if as calculating means a device already commonly used in the steam treatment device can be used, e.g. a central control device. The calculation means may be designed in particular as an electronic circuit, e.g. comprising a microprocessor, an ASIC, an FPGA, etc.

It is still an embodiment that the surface heating serves as the overheat detector. For example, the surface heating may have a temperature-dependent electrically conductive layer. Then, a surface heating temperature and consequently overheating can be determined by detecting a conductivity or corresponding electrical quantity, e.g. by comparison with a predetermined threshold.

The above-described characteristics, features and advantages of this invention, as well as the manner in which they are achieved, will become clearer and more clearly understood in connection with the following schematic description of an embodiment which will be described in detail in conjunction with the drawings.

1 shows an exploded view in an oblique view of an evaporator according to the invention;

2 shows a sectional side view of a steam treatment apparatus with the evaporator;

3 shows a sectional side view of a section of the assembled evaporator;

4 shows as a sectional representation in side view of a section 3 in the area of a side edge.

1 shows an exploded view in an oblique view of an evaporator 1 which, for example, for use in a household steam cooker H (see 2 ) is provided, for example in a standalone steamer or an oven with steaming function.

The evaporator 1 has a bottom part 2 with a bottom area 3 and an adjoining, frontally projecting circumferential edge 4 on. The bottom area 3 Here, for example, has a planar basic shape with a rectangular outer contour A with rounded edges. In the bottom area 3 There are at least two openings, here comprising a water passage opening 5 and a lead-through opening 6 for performing an electrical connection. From the edge 4 There are several springy locking tabs 7 up high. In addition, at least one fastening strap goes in the rearward direction 8th from, for example, for screwing with the household steam cooker H.

The bottom area 3 is inside the whole area and tight of an electrically operated surface heating 9 covered. The surface heating 9 has an electrical connection on its rear side 10 on, which through the passage opening 6 protrudes. The surface heating 9 also has a hole 11 on, congruent with the water passage opening 5 lies. Through the hole 11 and the water passage opening 5 Water can be filled in and drained.

The surface heating 9 is areally heated and likes this, for example, a liquid-facing electrically conductive front 9a exhibit. The surface heating 9 In addition, it may have a layer (eg inside), which becomes electrically conductive when a predetermined limit temperature is exceeded (see above). A strong change in the electrical conductivity or the electrical resistance or a current which can be conducted through this layer indicates that the limit temperature has been reached and thus also an occurrence of an overheating case. The limit temperature may, for example, be around 200 ° C. The surface heating 9 So, optionally, it also serves as an overheat detector to detect overheating.

The surface heating 9 has a plan view of her front 9a a non-angular outer contour, namely that of a rectangle with circular rounded corners. A narrow side edge 27 the surface heating 9 runs circumferentially or closed along this outer contour.

The surface heating 9 optionally has at least one heated or heated portion or at least one heated zone B1 and at least one unheated portion or at least one unheated zone B2. While, for example, at least one heating conductor (eg meander-shaped) is laid on the heated zone B1, it is missing at the unheated zone B2. A temperature of the heated zone B1 is in the on state above a predetermined temperature T, while a temperature of the unheated zone B2 in the on state is below the predetermined temperature T. In particular, the water may thereby be agitated strongly at the heated zone B1, possibly even boiling, while the water or its free surface at the unheated zone B2 remains comparatively calm. The unheated zone B2 takes here at least one corner of the surface heating 9 one.

The surface heating 9 and the lid 13 make up a receiving space R for water. The surface heating 9 forms a bottom or a bottom wall of the receiving space R.

On the bottom part 2 sits over a circumferential seal 12 a domed or cup-shaped cover part 13 on. The lid part 13 has several locking lugs on the outside 14 on, which for engagement with the locking tabs 7 are provided and a simple locking connection between the bottom part 2 and the lid part 13 allow. The lid part 13 points in its bottom part 2 spaced opposite top wall 15 two holes (not shown) for the passage of electrically conductive contact pins 16 , in particular metallic pins on. The contact pins 16 are in the receiving space R free.

The two contact pins 16 ends at the bottom, in particular at the same height and by in the receiving space R or 2 . 13 standing water are electrically connected to each other when the water has a predetermined (in particular "upper") level L1 (see also 3 ) reached. This electrical short circuit can be detected for determining the predetermined fill level L1, for example by a control device 24 (see also 2 ). The control device 24 likes the pins 16 apply an alternating low voltage to eliminate electrolytic effects.

The evaporator 1 is filled upon reaching the predetermined level L1 with a volume V of water.

The contact pins 16 lie above the unheated zone B2 of the surface heating 9 to allow a more reliable determination of a predetermined upper level L1, in particular less affected by a turbulent water surface.

On a circumferential side wall 17 of the lid 13 near the top wall 15 there is a steam outlet 18 , The exemplified neck-like steam outlet 18 like For example, be connected to a hose for guiding the steam generated by the evaporator in the food treatment room S of the household Dampfgargeräts H. The steam outlet 18 is located above the unheated zone B2 so that small drops of water generated by chilled water in the heated zone B1 are not entrained in the vapor stream. This increases the quality of the steam. The less water droplets are contained in the vapor stream, the higher its energy content and thus the efficiency. Furthermore, it is prevented that the food or food in the food treatment room S is damaged by the water droplets.

2 shows a sectional side view of a household Dampfgargerät H with the evaporator 1 out 1 , The household steam cooker H has a fresh water connection 20 on, which via a filling device serving as a filling 21 with the water passage opening 5 of the evaporator 1 connected is. The evaporator 1 is with its water outlet 5 also via a discharge pump serving as a drain 22 with a wastewater connection 23 of the evaporator 1 connected. An operation of the filling pump 21 and the drain pump 22 is via a control device 24 controlled. The control device 24 is also with the contact pins 16 connected and can short circuit to the contact pins 16 determine.

The control device 24 For example, may be a central control device of the household Dampfgargeräts H, which may for example control other functions, such as operation of the surface heating 9 of the evaporator 1 and / or at least one heating device (not shown) for heating a food treatment room S.

The water passage opening 5 is shown here in the form of two spatially separate water inlet or water outlet, but like in 1 a common water passage (ie, a combined water inlet and outlet).

When operating the evaporator 1 for steaming food is via the steam outlet 18 of the evaporator 1 Steam in the possibly warmed up food treatment room S of household Dampfgargeräts H admitted. This is done first by means of the filling pump 21 Water pumped into the receiving space R, through a short circuit between the contact pins 16 the achievement of in 3 shown predetermined level L1 is detected. With determination of the short circuit and thus the predetermined level is the filling 21 stopped immediately or after a time-defined overrun (eg between 1 sec and 3 sec). The then activated surface heating 9 lets the water evaporate, so that the water level drops. As the water level drops below the level L1, the short circuit mediated by the water is removed, and the controller 24 activates the filling pump again 21 for filling the receiving space R with water, etc. Typically, this is the filling pump per minute 21 activated twice to three times for five to seven seconds each. The construction of the evaporator 1 allows a particularly fast and delay-free evaporation of the filled water, for example, by the large-scale energy input by means of surface heating 9 and a low predetermined level L1 in the range of millimeters, eg between eight and ten millimeters, preferably 9 mm.

As in further 3 shown, protrude from the top wall 15 of the lid 13 inside partitions 25 and 26 in the receiving space R. At least one of the partitions 25 and 26 crosses an area between the two contact pins 16 and thereby extends a distance between the contact pins 16 , This will cause an electrical leakage path between the two contact pins 16 extended, for example, by a fine coating on the inside of the lid 13 can form from water-absorbing lime.

3 also shows more exactly the structure of the surface heating 9 as well as the arrangement of the seal 12 : The surface heating 9 has a carrier plate on top 28 on, which forms the bottom-side wall of the receiving space R and the front side 9a in the receiving space R points. The carrier plate 28 For example, may be a sheet steel part whose front 9a exemplified bare or scaled. The carrier plate 28 may in particular have a thickness between one and two millimeters, but is not limited thereto.

At a back of the carrier plate 28 There are several thick-film heating conductors 29 , and of the support plate 28 separated by an insulating layer (not shown). The thick film heating conductors 29 do not extend below the unheated zone B2. Also like from below a cover layer (not shown) on the thick-film heating conductors 29 and optionally the exposed areas of the insulating layer may be applied. Such surface heating 9 may in particular have a thickness between one and two millimeters, but is not limited thereto.

For example, two thick-film heating conductors 29 be available, which can be operated with a nominal power of 400 W or 800 W individually or together.

Both thick-film heating conductors like it 29 heat the heated zone B1 practically over the entire surface. The two thick-film heating conductors 29 may be meandered into each other, for example.

The seal 12 is as a double seal with an upper sealing element 12a and a bottom same sealing element 12b designed. The sealing elements 12a and 12b run analogous to the side edge 27 , The lower sealing element 12b seals a gap between the bottom part 2 , especially its edge 4 , and a back of the carrier plate 28 from. The upper sealing element 12a seals a gap between the front 9a the carrier plate 28 and the lid part 13 from. In particular, the upper sealing element 12a prevents liquid from the receiving space R to the bottom part 2 can get. So while the lid part 13 , the support plate 28 and the upper sealing element 12a come into contact with the liquid and therefore should be formed food safe, needs the bottom part 2 not to be trained in food safety. The bottom part 2 may in particular consist of a flame-retardant plastic which has a higher elasticity than the food-safe plastic of the lid part 13 ,

How closer in 4 listed, is the side edge 27 formed convex or convex in cross-section. The two sealing elements 12a and 12b the seal 12 lie on the convex side edge 27 on. Due to the convex shape form 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 kept slightly tense.

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

Generally, "on", "an", etc. may be taken to mean a singular or a plurality, in particular 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.

Also, a number may include exactly the specified number as well as a usual tolerance range, as long as this is not explicitly excluded.

LIST OF REFERENCE NUMBERS

1

 Evaporator

2

 Bottom part of the evaporator

3

 Bottom area

4

 edge

5

 Water passage opening

6

 Through opening

7

 snap tab

8th

 mounting tab

9

 panel heating

9a

 Surface of the surface heating

10

 Electrical connection

11

 hole

12

 poetry

12a

 upper sealing element

12b

 lower sealing element

13

 cover part

14

 locking lug

15

 Upper side wall of the lid

16

 pin

17

 Sidewall of the lid

18

 steam outlet

20

 Fresh water connection

21

 filling pump

22

 drain pump

23

 Waste water connection

24

 control device

25

 Internal partition

26

Internal partition

27

 Side edge of the surface heating

28

 support plate

29

 Thick film heating element

A

 outer contour

B1

 heated zone of surface heating

B2

 unheated zone of surface heating

H

 Household steam device

L

 hole

L1

 predetermined level

R

 accommodation space

S

 Dining Treatment Room

T

 temperature

V

 volume

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The 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

• 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 (12)

Evaporator ( 1 ) for a steam treatment device (H), comprising - a receiving space (R) for liquid to be evaporated with a bottom-side surface heating ( 9 ), which has a peripheral side edge ( 27 ), characterized in that - the side edge ( 27 ) is at least partially convex in cross-section. Evaporator ( 1 ) according to claim 1, characterized in that - the surface heating ( 9 ) a the receiving space (R) limiting support plate ( 28 ), on whose side facing away from the receiving space (R) side at least one Heizleiterbahn is arranged and - the carrier plate ( 28 ) is at least partially convex in cross-section. Evaporator ( 1 ) according to one of the preceding claims, characterized in that the evaporator ( 1 ) a seal ( 12 ), which at the side edge ( 27 ) rests. Evaporator ( 1 ) according to claim 3, characterized in that the seal ( 12 ) a double seal with two superimposed sealing elements ( 12a . 12b ), which on the upper side or on the underside on the side edge ( 27 ) rest. Evaporator ( 1 ) according to one of claims 3 to 4, characterized in that the seal ( 12 ) by means of the side edge ( 27 ) is stretched. Evaporator ( 1 ) according to one of the preceding claims, characterized in that a shape of the side edge ( 27 ) is cornerless in plan view. Evaporator ( 1 ) according to one of the preceding claims, characterized in that the evaporator is a housing ( 2 . 3 ) with a bottom part ( 2 ) and a lid part ( 13 ) and the receiving space (R) through the lid part ( 13 ) and the surface heating ( 9 ) is formed and the bottom part ( 2 ) and the lid part ( 13 ) consist of different materials. Evaporator ( 1 ) according to claim 7, characterized in that the bottom part ( 2 ) consists of a non-food-safe material and the cover part ( 13 ) consists of a food-safe material. Evaporator ( 1 ) according to one of claims 7 or 8, characterized in that the bottom part ( 2 ) consists of flame-retardant material and / or consists of a more elastic material than the cover part ( 13 ). Evaporator ( 1 ) according to one of the preceding claims, characterized in that the surface heating ( 9 ) several independently operable flat Heizleiterbahnen ( 29 ) having. Evaporator ( 1 ) according to claim 10, characterized in that at least two of the Heizleiterbahnen ( 29 ) have a different rated power. Steam treatment device (H), in particular steam cooking appliance, comprising at least one evaporator, characterized in that the evaporator is an evaporator ( 1 ) according to any one of the preceding claims.

Images