EP1671520B1 - Heating element for cooking appliances - Google Patents

Abstract

The invention relates to a heating element for a cooking appliance, particularly for the direct or indirect electrical heating of at least one item to be cooked, comprising at least one supporting layer, at least one heating element layer, which contacts the supporting layer at least in sections in a direct or indirect manner, and comprising at least one electric contact element or conductor element, with at least one elastic arresting element, which is or can be connected to the electric contact element or conductor element. The electric contact element or conductor element can be brought into contact, at least occasionally, with at least one heating resistor and/or with at least one contact point of the heating element layer via the elastic force of the elastic arresting element.

Description

The present invention relates to a heating element for a cooking appliance, in particular for direct and / or indirect heating of at least one item to be cooked, comprising at least one carrier layer and at least one at least partially directly or indirectly adjacent to the carrier layer heating element layer. Furthermore, the invention relates to a cooking appliance, comprising at least one inventive heating element, and a method for producing a heating element layer of a heating element according to the invention.

Heating elements or heating elements for cooking appliances are well known to those skilled in the art. These are generally electrical heating systems or hobs for cooking appliances with a non-metallic, such as ceramic, or metallic carrier plate and thereon directly or indirectly mounted heating resistors. For example, DE 40 28 354 A1 discloses a heating element, comprising a carrier plate made of ceramic material with a plurality of conductive resistance paths mounted on this carrier plate, which in turn can be supplied with power via control elements mounted on the rear side. As control elements bimetallic switches are proposed, which establish or interrupt a conductive contact with the resistance or conductor tracks with sufficient heat-related deflection. The connection of bimetallic strip to electrical lines is conventionally done via solder or screw, so that it can cause failures of the heating element due to heat stress and / or resulting from temperature fluctuations material stresses in the region of the contacts.

DE 100 06 953 A1 is concerned with hob plates, comprising at least one heating element and a temperature sensor which is connected to a heat-conducting element, which may be formed as a spring element and is pressed in the region of the temperature sensor against the underside of the hob plate. In this way, via a permanent contact with the heating plate whose temperature can be determined continuously and reliably. The contact with an electric heater is made via a heat conductor connection part in the form of a plug contact, which is attached to the outer peripheral wall of the cooktop panel. The Heizleiteranschlußteil is on the one hand conductively connected Bandheizleitern and on the other hand with electrical supply lines of the hob, the plug contacts are present directly in the Bandheizleiter the hob and thus are exposed to extreme heat radiation itself. Thus, it can also lead to malfunction of the cooktop panels in case of failure of the electrical contact due to the heat load or the associated material stresses.

DE 694 05 958 T2 discloses a steam generator with an electrically heated plate comprising a first fixed plate equipped with an electrical heating resistor and a second mobile plate pressed against a first main surface of the first plate by elastic spring devices. In this case, the electrical heating resistor is passed through the interior of the fixed first heating plate. By incorporating the heating resistor into the heating plate, it is subsequently no longer possible to locally control the hob via this heating resistor. Also, the failure of a heating resistor leads to the total failure of the steam generator.

DE 36 20 203 A1 describes an electrical heating element of a heating part and a connecting part, which consist at least partially of different electrically conductive materials, whereby the flexibility increases and the assembly should be facilitated. Here, the heating element can be connected via a releasable clamping or plug connection with the connecting part, so as to enable a temporary connection without the use of a spring element. Again, there may be failures of the heating element due to a defect in the electrical energy supply.

Furthermore, from DE 197 01 640 A1 a kontaktwärmeübertragendes cooking system with an electric hotplate with a hotplate body known. The hotplate body is heated by means of a heating resistor mounted on its underside in the form of spirally or radially extending conductor tracks. By selective control of individual tracks or the shorting of several tracks can be obtained from several heating zones Mehrkreiskochplatten. To achieve different heating capacities in different areas of the hotplate body, the conductor tracks in the individual heating zones are controlled separately from one another. This increases the Verschaltungsaufwand and makes the use of several sensors in different areas of the hotplate for adjusting a uniform heating power necessary. This makes the hotplate very maintenance intensive.

Modern hobs or heating systems are characterized by the fact that a plurality of locally limited heating elements can be targeted. Individual heating elements may in turn have one or more heating resistors. The smaller the respective Heizelement- or Heizwiderstandseinheiten and the denser they are, the higher the apparatus-technical effort to control each individual heating resistor separately or can control, which leads to an increased susceptibility to interference. Ideally, each individual heating resistor is connected via a separate electrical line to a control and regulation unit. The connection of the heating resistors to the electrical lines is done regularly via solder contacts. However, their production is both labor-intensive and time-consuming as well as very material-consuming and thus a cost-driving factor as a whole. In addition, these solder joints are permanently exposed to a very high temperature stress and significant temperature fluctuations and consequently regularly rapid material fatigue, especially in continuous use, such. B. in large kitchens or snack chains, to take into account.

From DE 196 48 199 A1 a device for connecting provided on a hob electrical conductor tracks is known. This device has a terminal block for holding connecting parts. These connecting parts are at one end out as resilient contact tongues from the terminal block. The contact tongues are biased on conductor tracks of a hob, while the other ends are available as connecting parts for connecting leads. A disadvantage of this Device is, however, that the connecting parts must be connected as additional intermediate elements in a known manner with a connection line. This connection is usually also achieved via a solder joint, which quickly leads to material fatigue and thus malfunction for the reasons mentioned above.

The complaints that come with this often lead to a negative appreciation of the cooking appliance used, especially since repairs can often only be performed by professionals and are associated with downtime and not negligible repair costs. In addition, a non-uniform contact pressure of a heating element to a surface to be heated lead to a different heat input at different points of the surface and thus to poor cooking results.

The present invention therefore an object of the invention to further develop the generic heating elements for a cooking appliance in such a way that it does not suffer from the disadvantages of the prior art and in particular provides very serviceable and user-friendly cooktop panels with a high density of heating resistors. Notably, a heating element is to be provided which, with a very maintenance-friendly control, enables a uniform and fail-safe introduction of heat into a carrier layer, in particular a crucible of a cooking appliance. It is a further object of the present invention to provide a cooking appliance and a method for producing a heating element layer of a heating element which overcomes the disadvantages of the prior art.

Accordingly, a heating element for a cooking appliance, in particular for direct or indirect electrical heating of at least one food was found with at least one electrical contact or conductor element and at least one resilient locking element which is connected or connectable to the electrical contact or conductor element, wherein the electric Contact or conductor element via the spring force of the resilient locking element at least temporarily in contact with at least one heating resistor and / or at least one contact point of the heating element layer can be brought.

With the heating element according to the invention succeeds heating plates, heating layers or heating resistors without any solder contact with an electrical conductor reliably and permanently and thus virtually maintenance-free to connect. For this purpose, it is generally only necessary to press the conductor element via the spring force of the locking element, for example a spring, to the heating resistor or pinch between locking element and heating resistor. For example, in an expedient embodiment of the invention, the conductor element can be made rigid and can also be firmly connected to the spring-elastic locking element. In this case, the spring force of the locking element is suitably chosen such that, although the conductor element is pressed against the heating resistor, but is not permanently changed in shape by this.

It can be provided according to a further embodiment that this heating element is a, in particular substantially flat, heating plate or a completely or partially substantially tubular, in particular in cylindrical form, heating. Accordingly, the heating elements according to the invention are particularly suitable for use in rotary evaporators, as they are e.g. in WO 02/12790 are described as steam generators for cooking appliances. The heating plates can basically be flat, curved, corrugated or in any other form.

In a further expedient embodiment of the invention, at least in sections at least one separating layer, preferably comprising at least one graphite layer, lies between the carrier layer and the heating element layer for at least partially homogenizing the heat input into the carrier layer and / or on the side of the heating element layer facing away from the carrier layer and at least in sections at least one mechanical buffer layer and / or at least one first thermal insulation layer, preferably comprising a micasheet, between the heating element layer and the resilient locking element. The carrier layer can be configured in one embodiment as a carrier plate. Of course, e.g. the carrier layer, the heating element layer, the separation layer, the mechanical buffer layer, the first thermal insulation layer and / or the resilient locking element to the selected form of the heating element or completely take on or take over.

It can be provided according to an embodiment that the carrier layer completely or partially made of stainless steel and / or the mechanical buffer layer completely or partially made of mica or exist.

According to a further aspect of the present invention, the heating element according to the invention comprises at least one pressing means, preferably comprising a press plate, with which the resilient locking element, preferably comprising a spring element plate, the mechanical buffer layer, the first thermal insulation layer, the heating element layer and / or the release layer against the support layer for the at least regional homogenization of the contact pressure to the carrier layer and / or the heat input into the carrier layer is or can be pressed. The heating element in this embodiment essentially has a pressed sandwich structure. Due to the use of a mechanical buffer layer, for example in the form of a mica layer, or the first insulating layer, preferably in the form of a micasheet, both the locking element and the Heizelement- and / or the separation layer or the graphite layer, even under severe thermal stress before mechanical Overuse or damage protected. This compressed structure is also space-saving to store and transport and install in a simple and reliable way in cooking appliances.

According to a particularly preferred further development, it should be noted that the mechanical buffer layer has or have at least one omission for the contact and conductor element in the region of at least one second section of the spring-elastic locking element, the first thermal insulation layer and / or the pressing means. By the mechanical buffer layer, the first thermal insulation layer and the pressing means between which the resilient locking element is optionally present at least partially constrained, have omissions, a second portion of the locking element is given movement in the direction of the support layer and also away from this. If, for example, the locking element is a metal plate, it is regularly tension-free in the flat, flat state. Upon deflection of at least a first portion of the locking element from the tension-free rest position, a restoring force is generally established. The resulting restoring force can be used in the present case to press a standing with the deflected portion of the locking element in connection conductor element or a contact element against the Heizelementschicht.

It can be inventively provided that the resilient locking element via at least one between the one hand, the heating element layer, the first thermal insulation layer and / or the mechanical buffer layer and, on the other hand, the pressing portion, and a second free portion adjoining the first portion, which is connected or connectable, directly or indirectly, in particular via a third portion, to the contact or conductor element. wherein the second section is preferably in the region of the omission. The locking element accordingly has at least one first section, which is clamped between the pressing means and the carrier layer, preferably the mica layer, and a second section which is substantially freely deflectable. In this case, the conductor element can be connected directly to this second section or with the interposition of a further, third section with the locking element. In one embodiment, the locking element ends with its free end, ie the first or third section in the region of the conductor element.

According to a further embodiment, however, at least a fourth section may be provided, which adjoins the second and / or third section of the resilient locking element and / or the contact or conductor element, the fourth section preferably with the mechanical buffer layer, the first thermal Insulating layer and / or the pressing means is connected or connectable. The fourth section may e.g. serve to support the locking member on the edge of the omission, which is opposite to the first portion thereof. Although in this way the range of motion of the locking element is limited, but not in a scope that could prevent a connection by means of spring force. Rather, succeeds with the help of the fourth section a very secure position attachment of the locking element.

Preferably, the contact or conductor element via an insulator, preferably in the form of an insulating sleeve, connectable to or connected to the resilient locking element. This may be e.g. to act an insulating sleeve, which is admitted on the one hand in the second or third portion of the locking element and on the other hand can absorb the contact element shift invariant.

Particularly advantageous heating elements are characterized in that the heating element according to the invention, viewed from the carrier layer in the direction of the resilient locking element, as a carrier layer or as Heizelementschicht at least partially at least one stainless steel layer and at least partially at least one ceramic layer and Furthermore, at least in sections at least one layer with electrical heating resistors and / or at least partially has at least one glass layer. Of course, the glass layer is not formed consistently at those points at which the conductor element comes into contact with the heating resistor.

According to an alternative embodiment, a carrier layer according to the invention is used, which, viewed from the free outer surface of the same, at least one layer containing at least one thermally conductive metal, in particular steel, at least one layer containing at least one highly thermally conductive metal, in particular copper, and at least one second insulation layer.

Furthermore, it can alternatively be provided that the carrier layer, viewed from the free outer surface, comprises at least one layer containing at least one good heat-conducting metal, in particular copper, at least one layer containing at least one poorly heat-conducting metal, in particular steel, and at least one second insulating layer.

Furthermore, heating elements according to the invention are also suitable in which the carrier layer, viewed from the free outer surface, comprises at least one electrically insulating ceramic layer, at least one electrically conductive ceramic layer and / or at least one second insulating layer.

It can be provided that the heating element layer is formed as a thick film or as a thin film.

It can be provided that the heating element layer by means of silk-screen printing or a printing process, preferably as a thick film, can be produced.

According to a further embodiment, it is proposed that the heating element layer has a plurality of individual heating resistors which are arranged in at least two heating paths such that the heating resistors are electrically connected in parallel to each other within each heating path and the heating paths are electrically connected in series with each other, and all heating resistors can be supplied with electrical energy at the same time, wherein at least two heating resistors have different heating powers and / or the heating resistors are arranged at least in regions on the heating element layer at different distances from each other and the heating resistors are provided via a thick layer.

Furthermore, it can be provided that the heating resistors can be produced on the heating element layer with a serigraphy or a printing process.

Furthermore, it is proposed with the invention that the at least two heating resistors with different heating powers have different electrical resistances, in particular have different geometric dimensions and / or comprise different materials, in particular materials with different dopings.

It is preferably provided that the at least two heating resistors with different surface sizes different peripheral shapes, in particular at least one heating element substantially polygonal, in particular trapezoidal, triangular, square, rectangular, and / or hexagonal peripheral shape, different circumferential lengths, different side lengths, in particular different widths and / or lengths, and / or have different thicknesses.

A further preferred embodiment of the invention provides that the heating power and / or the distance of the heating resistors at least partially, preferably over the entire heating element, to an at least partially existing Andruckstärke the Heizelementschicht to the carrier layer, at least partially, in particular depending on a local thermal conductivity of the carrier layer, predetermined Heizleistungsdichtenverteilung within the heating element layer and / or adapted to an at least partially predetermined heat density distribution within the carrier layer is or are.

In addition, it is provided that the heating power of a first heating resistor, in a first region of the Heizelementschicht with a first Andruckstärke the heating element layer is arranged on the carrier layer, is less than the heating power of at least a second heating resistor, which is arranged in a second region with a lower pressure than the first Andruckstärke the contact pressure of the Heizelementschicht to the carrier layer and / or the distance between two heating resistors to each other in the first region greater than the distance between two heating resistors to each other in the second region.

Furthermore, the invention provides that the first area in the vicinity of at least one, preferably adjacent to at least one attachment or pressure point is preferably in the form of an opening for at least partially performing or Durchgreifung a fastening device for attachment of the Heizelementschicht to the carrier layer , and / or the second area is located farther away from at least one, in particular not adjacent to, at least one attachment or pressure point compared to the first area.

It is further preferred that the heating power of a third heating resistor, which is arranged in a third region of the Heizelementschicht with a first heating power density of the Heizelementschicht, is lower than the heating power of at least a fourth heating resistor, in a fourth region with a lower compared to the first Heizleistungsdichte second heating power density of the heating element layer is arranged, and / or the distance between two third heating resistors in the third region is greater than the distance between two fourth heating resistors in the fourth region.

It can also be provided that the third region of the heating element layer is in the vicinity of at least one, preferably adjacent at least one, first region of the carrier layer having a first thermal conductivity and / or with a first heat density and the fourth region of the heating element layer in the proximity of at least one, preferably adjacent to at least one, second region of the carrier layer having a lower compared to the first thermal conductivity second thermal conductivity and / or a higher heat density compared to the first heat density.

Further, the invention proposes that the electrical heating resistors of a heating track substantially the same heating power, substantially the same geometric dimensions, have substantially the same distance from each other and / or comprise substantially the same materials.

In particular, it can be provided that the separating layer, the heating element layer, the mechanical buffer layer, the first thermal insulation layer, the resilient locking element and / or the pressing means are designed in one element.

In particular, it may be preferred according to the invention that the pressing means, the resilient locking element, the mechanical buffer layer, the first thermal insulation layer, the heating element layer and / or the release layer are releasably or firmly, in particular by means of an adhesion, preferably by means of an adhesive joined together.

In an advantageous embodiment of the invention it is provided that the heating paths each have a plurality of at least pairwise adjacent heating resistors, wherein the heating resistors have a surface which is at least partially, preferably in a plane bounded by first and second side edges, wherein two adjacent Have heating resistors to achieve electrical parallel connection facing each other adjacent first side edges, which are at least partially spaced from each other and / or, in particular via at least one Isolierzwischenschicht or electrical insulation, electrically insulated.

It is proposed according to the invention that two mutually facing, adjacent second side edges of the heating resistors of adjacent first and second heating tracks to achieve the series electrical connection of the heating paths at least partially over at least a first electrically conductive means, in particular in the form of at least one of the, in particular each, second side edge the heating resistors of the first heating track and on the, in particular each, second side edge of the heating resistors of the second heating track adjacent first electrical trace are connected or connected to each other, wherein by means of the first electrically conductive means an electrical current through electrical heating resistors adjacent first and second heating tracks is conductive ,

It is preferred that at least a second electrically conductive means which conductively connects at least two, in particular all second side edges of heating resistors of an outer heating track, which are in particular not adjacent to a first or second side edge of a heating resistor, wherein the at least one second electrically conductive Means in particular has at least one contact point and / or is in operative connection with at least one contact point.

According to the invention it can also be provided that at least one third electrically conductive means to at least one, in particular each, first and / or second side edge of a heating resistor at least a first, outer heating track, in particular not to a first or second side edge of a heating resistor of a first or second Is adjacent heating track, in particular no intermediate insulating layer.

It is also proposed that the first, second and / or third electrically conductive means comprise at least one high-conductivity electrical material, in particular silver or copper.

It may further be provided that adjacent heating tracks are arranged substantially parallel to each other, and / or at least one heating track along a straight, curved or circular path is arranged.

According to the invention, it is particularly preferred that heating paths with different dimensions are provided.

Finally, it can be provided in the heating element according to the invention that each heating track has at least three, in particular at least five, electric heating resistors, and / or at least three, in particular at least five. Heating paths are provided, which are preferably electrically connected to each other and / or at least two contact points with a power source via at least one first electrically conductive means.

The invention further provides a cooking appliance comprising at least one heating element according to the invention.

This cooking appliance may in particular be characterized in that at least one heating element, preferably all heating elements, is releasably attachable to the cooking appliance, in particular via a screw connection.

It is also proposed with the invention that a control and / or regulating unit with at least one, in particular all, heating element (s) and / or at least one, in particular all, electrical heating resistor or heating resistors, and / or at least one sensor , in particular in operative connection.

It is further provided that via the control and / or regulating unit, the heating power of the heating element, preferably the individual heating resistors and / or at least two groups of heating resistors, in particular depending on at least one, in particular detectable via the sensor, measured variable, such as a temperature, a humidity, a degree of browning of a food, a weight of a food, a size of a food, a Gargutart and / or the like, is controllable and / or controllable.

• Bereitstellen eines Substrats; und
• Aufbringen von Heizwiderständen und elektrischen Leiterbahnen mittels einer Serigraphietechnik, bereitgestellt.

Finally, the invention provides a method for producing a heating element layer of a heating element according to the invention, comprising the steps

• Providing a substrate; and
• Application of heating resistors and electrical conductors by means of a serigraphy technique provided.

It can be provided that subsequently at least partially, at least a cover layer is applied.

According to the invention it is preferred that the substrate is provided with at least one electrically conductive material, preferably a metal, in particular stainless steel, a glass, a ceramic and / or a plastic, and / or before the application of the heating resistors at least in regions, at least one thermally and / or electrically insulating layer is applied to the substrate.

Furthermore, it can be provided that the thermally and / or electrically insulating layer is provided with at least one ceramic material and / or at least one glass.

Furthermore, it can be provided that the cover layer is provided with an electrically insulating and / or a material which protects against mechanical influences, preferably a glass and / or a protective lacquer.

The invention finally proposes that the heating power, the electrical resistance and / or the distance of the heating resistors from each other by dimensioning the geometric dimensions of the heating resistors is adjusted.

With the heating elements of the present invention can be readily provided a durable, reliable contact between an electrical supply line and a heating resistor, which is also less material intensive and prone to repair. In addition, in the event of damage, the defect can also be remedied quickly and expertly by a layman. Furthermore, it is possible to accommodate a very large density of individual resistance units on a hob and to control them separately.

The ease of maintenance of the heating element according to the invention is further increased in a claimed embodiment by a separate control of the individual resistance units at the same time high uniformity of heat input is dispensable. In this embodiment, it is possible by the different size and the plurality of heating resistors on a Heizelementschicht not only to achieve a high reliability, but also to adjust the heating power of the different areas of a Heizelementschicht targeted. For example, a uniform heat input into a carrier layer is possible despite different pressure intensities of a heating element layer on the carrier layer. For this purpose, the heating power of the individual heating resistors or the distance between the individual heating resistors to the particular environmental conditions in the individual areas of the heating element layer or the support layer, such as to the contact pressure of the heating element layer to the carrier layer, to the thermal conductivity of the carrier layer in certain areas, etc., adapted. Furthermore, the service life of the heating element layer is also considerably prolonged, since it is harmless for uniform heat input into the carrier layer due to the multiplicity of heating resistors if a single heating resistor fails, since this failure can be compensated by adjacent heating resistors. In particular, this is supported by the arrangement of a separating layer between the heating element layer and the carrier layer, since this leads to a homogenization of the heat input. Furthermore, a current flow through the heating element is not prevented by the failure of one or more electrical heating resistors. Thus, a desired cooking success can be achieved despite a failed heating resistor.

Fig. 1:

eine Teilschnittansicht eines erfindungsgemäßen Heizelements; und

Fig. 2:

eine Draufsicht einer Heizelementschicht des erfindungsgemäßen Heizelements nach Figur 1.

Further features and advantages of the invention will become apparent from the following description in which an embodiment of the invention with reference to a schematic drawing is explained in detail. Showing:

Fig. 1:

a partial sectional view of a heating element according to the invention; and

Fig. 2:

a top view of a Heizelementschicht the heating element according to the invention of Figure 1.

Fig. 1 shows a heating element 1 according to the invention in a partial sectional view. Between a carrier layer or plate 2 and a pressing plate 4 are according to a preferred embodiment, in this order, a release layer in the form of a graphite foil 6, a Heizelementschicht 8, a mechanical buffer layer in the form of a mica layer 10 and a spring element plate 12 before. The graphite foil 6 is applied in particular to equalize a heat input into the carrier layer 2 in a manner known to the person skilled in the art on the underside of the carrier layer 2. The Heizelement- or Heizwiderstandsschicht 8, for example, by means of known screen printing in a desired pattern, for example, applied to the graphite foil 6, are prepared. For mechanical protection of this resistance or the heating element layer, it is at least substantially covered by a mica plate 10. On the side facing away from the heating element 8 side of the mica plate 10 is at least partially a spring element 12 at. For example, this may be a metal plate, which is equipped at least in some areas with resilient properties. The layer sequence of graphite foil 6, Heating element layer 8, mica layer 10 and spring plate 12 is held by the pressing plate 4 as close as possible to the underside of the carrier layer 2. This can be z. B. by means of a nut construction 14 in particular done in such a way that the screw or an extension of the screw with the underside of the carrier layer 2 is fixedly connected via a nut 16 and a pressing pressure, preferably by interposing a washer 18, on the outside of Press plate 4 is exercised. By an appropriate adjustment of the nut 16, an optimal contact pressure can be adjusted without having to fear damage to the layer structure. In the area of the resilient element 12, an omission 22 as well as in the press plate 4 an omission 30 is provided both in the mica layer 10, so that a contact element 24 which is connected to the spring-elastic locking unit acting as a resilient element 12, always in conductive contact with the heating element layer 8 is. If the spring-elastic element 12 is made of metal, it makes sense not to bring the electrical line or the electrical contact element 24 directly, but with the interposition of an insulating sleeve 20, with the resilient element 12 in conjunction. The contact element 24 is preferably designed to be rigid in the region of its contact with the heating element layer 8, preferably with a strength sufficient to withstand a restoring force generated by the resilient element 12 without bending, even under thermal stress. As suitable materials for these contact elements 24, for example, copper rods have been found. The resilient element 12 is forced at least over a portion 26 between the press plate 4 and the mica layer 10 substantially movement invariant. In the area of the omission 22, it is then possible to deflect at least one further section 28 of the resilient element 12 in the direction away from the underside of the carrier layer 2. Due to the resilient nature of the element 12 acts on the locked in the insulating sleeve 20 contact element 24 always a restoring force. This is used to permanently ensure reliable contact with the heating element layer 8. The omissions 22, 30 in the mica layer 10 and in the press plate 4 may each have different dimensions or be the same size. Preferably, the omission 30 of the pressing plate 4 is dimensioned larger than the omission 22 of the mica plate 10. Basically, however, a reverse sizing is possible. Preferably, the resilient element 12 continues beyond the insulating sleeve 20 with, for example, a portion 34 and may be configured such that it comes to rest in the region of the top of the press plate 4 with the same. By also in this section 34 of the resilient element 12 whose deflection away from the underside of the carrier layer 2 targeted is used to establish the connection of the contact element 24 to the Heizelementschicht 8, a particularly secure and reliable contact source to an electrical line, which is at least partially part of the contact element 24, or a voltage source is ensured. In particular, it requires no solder connection of the electrical line to the heating element 1, but it is possible to either completely dispense with a solder joint or to relocate this in a range that is exposed to no thermal and no mechanical stress. The present in an insulating sheath 20 electrical contact element 24 can also replace easily in the event of damage. The same applies to the entire resilient element 12 when the press plate 4 is held by means of a screw construction 14.

The heating element layer 8, the graphite foil 6, the mica layer 10, the spring plate 12 and the pressing plate 4 can be connected to one another detachably as well as to simplify assembly, for example with an adhesive. Furthermore, various functions of the layers can also be achieved by a single component or a single layer, since it is essentially based on the function of a layer, in particular for homogenizing a heat input (release and / or graphite layer) or for equalizing a contact pressure (compression). and / or spring element plate) arrives. For example, the press plate 4, which serves to press the various layers, and the spring plate 12, which is adapted for a resilient pressing of the electrical contact element 24, can be performed in one. Also, the mica layer 10 can not only fulfill the task of a mechanical buffer layer but also the task of a heat insulating layer. Alternatively, an additional first thermal insulation layer, which is preferably a micasheet, may also be provided, in particular adjacent to the heating element layer 8.

Further, the pressing plate 4 may be made elastic at least on the surface facing the heating element layer, so that it is possible to dispense with the mica layer 10.

2, a heating element layer 8 is shown in a plan view. The heating element layer 8 accordingly has substantially rectilinearly aligned and parallel mutually extending heating paths 804, 804 ', 805, 805', which each comprise a multiplicity of electrical heating resistors 806, 807, 806 ', 807'. The electrical heating resistors 806, 806 ', 807, 807' have a rectangular or square surface shape and are in the present case within a heating track 804, 804 ', 805, 805' each of the same surface size and shape within each heating track 804, 804 ', 805, 805 'are adjacent electrical heating resistors 806, 807, 806', 807 'each separated by an electrical insulation 812 from each other. The insulation 812 prevents direct contact of the first side edges 810, namely the first side edges 810.1 and 810.2 or 810.1 'and 810.2' of adjacent heating resistors in the heating track. Second side edges 820 of adjacent heating resistors of a heating track, unlike their first side edges 810.1, 810.2, 810.1 ', 810.2', are not assigned to each other or are adjacent over longer sections. Adjacent heating tracks, eg 804, 804 'and 805, 805', are not in direct contact with each other, but are connected to each other via first electrical traces 808. In this case, the second side edges 820 of the electrical heating resistors 806, 807, 806 ', 807' of a heating track 804, 804 ', 805, 805' are regularly applied to a first electrical track 808. In the same way, the outer side 817 and 819 forming second side edges 820 of the heating resistors 806, 807 of the respective outer heating tracks 804, 805 of the Heizelementschicht 8 with a second electrical conductor track 814 and 816 are connected. In this embodiment of a heating element layer according to the invention, an electric current can not be forwarded directly via adjacent electrical heating resistors 806, 807, 806 ', 807' within a heating track 804, 804 ', 805, 805'. Rather, the electric current is forwarded via an electrical heating resistor 806 of a first heating track 804 by means of a first electrical track 808 into an electrical heating resistor 806 'of an adjacent heating track 804'. A possible path for the electric current is shown by way of example in the illustration of the heating element layer 8 of FIG. 2 and marked with A. If, for example, an electrical heating resistor 806 fails within a heating track 804 during operation, due to the large number of heating resistors and the associated relatively small surface area of the heating resistors, this will mean that the entire heating plate can easily be used further. In particular, the failure of individual electrical heating resistors 806, 807, 806 ', 807' readily by the other electrical heating resistors 806, 807, 806 ', 807' of the heating tracks 804, 804 ', 805, 805' are compensated, so that a proper Cooking operation can be maintained. In this way it is possible to react very flexibly to the failure of individual electrical heating resistors. The desired cooking success is thus achieved even with partially damaged or not completely functional heating element layer 8. Throughout This results in a cooking appliance for a much longer effective life of a hot plate and thus a lower maintenance susceptibility.

In Fig. 2 is also good to see that the individual heating resistors have different surface areas in the different heating paths. Thus, the individual heating resistors also have different electrical resistances and thus different heating powers. Due to the different sizes of the heating resistors 806, 807, 806 ', 807' is to be achieved in particular that a different heat transfer from the Heizelementschicht 8 in the medium to be heated, in particular in the carrier layer 2, see Figure 1, for example, due to a different Andruckstärke the heating element layer 8 can be present on the carrier layer 2 in different regions of the heating element layer 8 of the heating element 1 according to the invention, is compensated. For example, the surface of the heating resistors in areas around first openings 822, 824, 826, 828, which represent the recesses for the screw connection 14, are larger in order to compensate for the improved heat conduction into the carrier layer 2 due to the greater pressure strength. Because of the larger surface of the heating resistors and thus their lower electrical resistances in this area, namely their heat output is lower. Thus, the heating element layer 8 is designed so that the surface of the heating resistors in the areas with the largest contact pressure is greatest, so the lowest heating power is provided by the heating resistors, and the smaller, the farther the heating resistors from the first openings 822, 824th , 826, 828 are removed. The heating power of this from the first openings 822, 824, 826, 828 remote heating resistors is namely greater because of the greater electrical resistance. Thus, it is achieved that the heating element layer 8 allows a very uniform in terms of area heat input into the carrier layer 2 and thus for example in a cooking container. The electrical contact elements 24 shown in FIG. 1 are preferably pressed onto the heating element layer 8 at contact points 830 and 830 'shown in FIG. 2, which are each connected to a second electrical conductor track 814, 816. In the middle of the heating element layer 8 is a second opening 832, which is provided for a thermal sensor (not shown) and has substantially no influence on the contact pressure. As a result, a targeted monitoring of a heating power of the heating element 1 is possible.

Thus, a plurality of heating elements 1 according to the invention, each having a heating element layer 8, are detachably attached to a cooking appliance, wherein the heating elements 1 or their Heizelementschichten 8 may have different sizes, which are then attached like a mosaic. Such a heating element layer 8 can be produced in a method according to the invention by means of a serigraphy technique or a printing technique in a simple and uncomplicated way. In this case, a ceramic layer is applied to a substrate, preferably in the form of a stainless steel plate, to which in turn by means of the serigraphy technique heating resistors, which can have different sizes in the above-mentioned manner, and printed conductors can be printed. Finally, a mechanical protection in the form of a glass layer can be applied. This leads to a very simple production, and the resistors can be configured arbitrarily on a template form.

Cooking appliances, in which heating elements according to the invention can be used, comprise in particular crucibles, Heißluftgargeräte, Dampfgargeräte, combi steamer for operation with hot air and steam, steam generators, heating devices in the form of at least one hob and holding units.

Claims (45)

1. Heating element (1) for a cooking appliance, in particular for directly or indirectly electrically heating at least one item of food to be cooked, said element comprising at least one carrier layer (2), at least one heating element layer (8) which directly or indirectly rests on the carrier layer (2) at least in sections, and at least one electrical contact or conductor element (24), characterized by
   at least one resilient locking element (12) which is connected, or can be connected, to the electrical contact or conductor element (24), the electrical contact or conductor element (24) being able to be brought into contact, at least temporarily, with at least one heating resistor (806, 806', 807, 807') and/or with at least one contact point (830, 830') of the heating element layer (8) using the spring force of the resilient locking element (12).
2. Heating element (1) according to Claim 1, characterized in that
   this heating element (1) represents a heating plate which is, in particular, essentially planar or a heating unit which is entirely essentially tubular, in particular in the form of a cylinder, or is essentially tubular, in particular in the form of a cylinder, in sections.
3. Heating element (1) according to Claim 1 or 2,
   characterized in that
   at least one separating layer, which preferably comprises at least one graphite layer (6), is present at least in sections between the carrier layer (2) and the heating element layer (8) for the purpose of evening out the input of heat to the carrier layer (2) at least in regions, and/or
   at least one mechanical buffer layer, which preferably comprises a mica layer (10), and/or at least one first thermal insulation layer, which preferably comprises a mica layer, is/are present at least in sections on that side of the heating element layer (8) which faces away from the carrier layer (2) and/or between the heating element layer (8) and the resilient locking element (12).
4. Heating element (1) according to one of the preceding claims, characterized by
   at least one contact-pressure means which preferably comprises a press plate (4) which can be used to press the resilient locking element, which preferably comprises a spring element plate (12), the mechanical buffer layer (10), the first thermal insulation layer, the heating element layer (8) and/or the separating layer (6) against the carrier layer (2) for the purpose of evening out the magnitude of contact pressure on the carrier layer (2) and/or the input of heat to the carrier layer (2) at least in regions.
5. Heating element (1) according to one of the preceding claims, characterized in that
   the mechanical buffer layer (10), the first thermal insulation layer and/or the contact-pressure means (4) has/have at least one cutout (22, 30) for the contact or conductor element (24) in the region of at least one second section (28) of the resilient locking element (12).
6. Heating element (1) according to one of the preceding claims, characterized in that
   the resilient locking element (12) has at least one first section (26), which is present between, on the one hand, the heating element layer (8), the first thermal insulation layer and/or the mechanical buffer layer (10) and, on the other hand, the contact-pressure means (4), and a second, free section (28) which adjoins the first section (26) and is directly connected, or can be connected, to the contact or conductor element (24) or is indirectly connected, or can be connected, to the latter, in particular by means of a third section, the section (28) preferably being in the second region of the cutout (22, 30).
7. Heating element (1) according to Claim 6,
   characterized by
   at least one fourth section (34) which adjoins the second and/or third section (28) of the resilient locking element (12) and/or the contact or conductor element (24), the fourth section (34) preferably being connected, or being able to be connected, to the mechanical buffer layer (10), the first thermal insulation layer and/or the contact-pressure means (4).
8. Heating element (1) according to one of the preceding claims, characterized in that
   the contact or conductor element (24) can be connected to the resilient locking element (12), in particular to the second, third and/or fourth section (28, 34) of the latter, by means of an insulator, preferably in the form of an insulating sleeve (20).
9. Heating element (1) according to one of the preceding claims, characterized in that
   the carrier layer (2) completely or partially comprises stainless steel and/or the mechanical buffer layer (10) completely or partially comprises mica.
10. Heating element (1) according to one of the preceding claims, characterized in that,
    when viewed from the carrier layer (2) in the direction of the resilient locking element (12), said heating element has, as a carrier layer (2) or as a heating element layer (8), at least one stainless steel layer at least in sections and/or at least one ceramic layer at least in sections and also at least one layer containing electrical heating resistors (806, 806', 807, 807') at least in sections and/or at least one glass layer at least in sections.
11. Heating element (1) according to one of Claims 1 to 9, characterized in that
    the carrier layer (2), when viewed from the free outer surface, comprises at least one layer, which contains at least one thermally conductive metal, in particular steel, at least one layer, which contains at least one metal having good thermal conductivity, in particular copper, and at least one second insulation layer.
12. Heating element (1) according to one of Claims 1 to 9, characterized in that
    the carrier layer (2), when viewed from the free outer surface, comprises at least one layer, which contains at least one metal having good thermal conductivity, in particular copper, at least one layer, which contains at least one metal having poor thermal conductivity, in particular steel, and at least one second insulation layer.
13. Heating element (1) according to one of Claims 1 to 9, characterized in that
    the carrier layer (2), when viewed from the free outer surface, comprises at least one electrically insulating ceramic layer, at least one electrically conductive ceramic layer and/or at least one second insulation layer.
14. Heating element (1) according to one of the preceding claims, characterized in that
    the heating element layer (8) is in the form of a thick layer or a thin layer.
15. Heating element (1) according to Claim 14,
    characterized in that
    the heating element layer (8) can be produced, preferably in the form of a thick layer, using serigraphy or a printing process.
16. Heating element (1) according to one of the preceding claims, characterized in that
    the heating element layer (8) has a multiplicity of individual heating resistors (806, 806', 807, 807') which are arranged in at least two heating tracks (804, 804', 805, 805') in such a manner that the heating resistors within each heating track (804, 804', 805, 805') are electrically connected in parallel with one another and the heating tracks (804, 804', 805, 805') are electrically connected in series with one another, and
    all of the heating resistors (806, 806', 807, 807') can be simultaneously supplied with electrical energy, at least two heating resistors having different heating powers and/or the heating resistors being arranged on the heating element layer (8) at different distances from one another at least in regions, and the heating resistors (806, 806', 807, 807') being provided using a thick layer.
17. Heating element (1) according to Claim 16,
    characterized in that
    the heating resistors (806, 806', 807, 807') on the heating element layer (8) can be produced using serigraphy or a printing process.
18. Heating element (1) according to Claim 16 or 17,
    characterized in that
    the at least two heating resistors having different heating powers have different electrical resistances, in particular different geometrical dimensions, and/or comprise different materials, in particular materials having different doping.
19. Heating element (1) according to Claim 18,
    characterized in that
    the at least two heating resistors having different surface areas have different circumferential shapes, in particular at least one heating resistor has an essentially polygonal, in particular trapezoidal, triangular, square, rectangular and/or hexagonal, circumferential shape, different circumferential lengths, different side lengths, in particular different widths and/or lengths, and/or different thicknesses.
20. Heating element (1) according to one of Claims 16 to 19, characterized in that
    the heating power of, and/or the distance between, the heating resistors is/are adapted, at least in regions but preferably over the entire heating element, to the magnitude of contact pressure of the heating element layer (8) on the carrier layer (2), which is present at least in regions, to a heating power density distribution within the heating element layer (8), which has previously been determined at least in regions, in particular on the basis of a local thermal conductivity of the carrier layer (2), and/or to a heat density distribution within the carrier layer (2), which has previously been determined at least in regions.
21. Heating element (1) according to Claim 20,
    characterized in that
    the heating power of a first heating resistor, which is arranged in a first region of the heating element layer (8) with a first magnitude of contact pressure of the heating element layer (8) on the carrier layer (2), is lower than the heating power of at least one second heating resistor, which is arranged in a second region with a second magnitude of contact pressure of the heating element layer (8) on the carrier layer (2) which is smaller than the first magnitude of contact pressure, and/or the distance between two heating resistors in the first region is greater than the distance between two heating resistors in the second region.
22. Heating element (1) according to Claim 21,
    characterized in that
    the first region is situated in the vicinity of, and preferably adjoins, at least one fastening or contact-pressure point, which is preferably in the form of an opening (822, 824, 826, 828) for at least partially guiding or engaging a fastening device for the purpose of attaching the heating element layer (8) to the carrier layer (2), and/or the second region, in comparison with the first region, is at a greater distance from, and in particular does not adjoin, at least one fastening or contact-pressure point.
23. Heating element (1) according to one of Claims 16 to 22, characterized in that
    the heating power of a third heating resistor, which is arranged in a third region of the heating element layer with a first heating power density of the heating element layer, is lower than the heating power of at least one fourth heating resistor, which is arranged in a fourth region with a second heating power density of the heating element layer which is lower than the first heating power density, and/or the distance between two third heating resistors in the third region is greater than the distance between two fourth heating resistors in the fourth region.
24. Heating element (1) according to Claim 23,
    characterized in that
    the third region of the heating element layer is situated in the vicinity of, and preferably adjoins, at least one first region of the carrier layer with a first thermal conductivity and/or with a first heat density, and the fourth region of the heating element layer is situated in the vicinity of, and preferably adjoins, at least one second region of the carrier layer with a second thermal conductivity that is lower than the first thermal conductivity and/or a heat density that is greater than the first heat density.
25. Heating element (1) according to one of Claims 16 to 24, characterized in that
    the electrical heating resistors (806, 806', 807, 807') of a heating track (804, 804', 805, 805') have essentially the same heating power, essentially the same geometrical dimensions and are essentially at the same distance from one another and/or essentially comprise the same materials.
26. Heating element (1) according to one of the preceding claims, characterized in that
    the separating layer (6), the heating element layer (8), the mechanical buffer layer (10), the first thermal insulation layer, the resilient locking element (12) and/or the contact-pressure means (4) are configured in one element.
27. Heating element according to one of the preceding claims, characterized in that
    the contact-pressure means (4), the resilient locking element (12), the mechanical buffer layer (10), the first thermal insulation layer, the heating element layer (8) and/or the separating layer (6) are releasably or firmly connected to one another, in particular by means of adhesion, preferably using an adhesive.
28. Heating element (1) according to one of the preceding claims, characterized in that
    the heating tracks (804, 804', 805, 805') each have a multiplicity of heating resistors (806, 806', 807, 807') which are adjacent to one another at least in pairs, the heating resistors (806, 806', 807, 807') having a surface which is at least partially bounded by first and second side edges (810, 820), preferably in one plane, two adjacent heating resistors (806, 806', 807, 807'), for the purpose of achieving the electrical parallel connection, having first side edges (810.1, 810.2, 810.1', 810.2'), which are adjacent to one another, face one another, are at least partially at a distance from one another and/or are electrically insulated from one another, in particular by means of at least one intermediate insulating layer or electrical insulation (812).
29. Heating element (1) according to Claim 28,
    characterized in that,
    in order to electrically connect the heating tracks in series, two facing, adjacent second side edges (820.1, 820.2) of the heating resistors (806, 806', 807, 807') of adjacent first and second heating tracks (804, 804', 805, 805') can be at least partially connected to one another, or are connected to one another, using at least one first electrically conductive means, in particular in the form of at least one first electrical conductor track (808) which is on the second side edge (820.1), in particular on each second side edge, of the heating resistors (806, 807) of the first heating track (804) and on the second side edge (820.2), in particular on each second side edge, of the heating resistors (806', 807') of the second heating track (804'), the first electrically conductive means (808) being able to be used to conduct an electrical current through electrical heating resistors (806, 807, 806', 807') of adjacent first and second heating tracks (804, 804', 805, 805').
30. Heating element (1) according to one of the preceding claims, characterized by
    at least one second electrically conductive means (814, 816) which conductively connects at least two second side edges (820), in particular all of the second side edges, of heating resistors (806, 807) of an outer heating track (804, 805) to one another, which are, in particular, not adjacent to a first or a second side edge of a heating resistor, the at least one second electrically conductive means (814, 816) having, in particular, at least one contact point (830, 830') and/or being operatively connected to at least one contact point (830, 830').
31. Heating element (1) according to one of the preceding claims, characterized by
    at least one third electrically conductive means for at least one first and/or second side edge, in particular each side edge, of a heating resistor of at least one first outer heating track which is, in particular, not adjacent to a first or a second side edge of a heating resistor of a first or a second heating track, in particular does not have an intermediate insulating layer.
32. Heating element (1) according to one of Claims 29 to 31, characterized in that
    the first, second and/or third electrically conductive means (808, 814, 816) comprise(s) at least one electrical material having a high conductivity, in particular silver or copper.
33. Heating element (1) according to one of Claims 16 to 32, characterized in that
    adjacent heating tracks (804, 804', 805, 805') are arranged essentially parallel to one another and/or at least one heating track (804, 804', 805, 805') is arranged along a rectilinear, curved or circular track.
34. Heating element (1) according to one of Claims 16 to 33, characterized in that
    heating tracks (804, 804', 805, 805') having different dimensions are provided.
35. Heating element (1, 1') according to one of Claims 16 to 34, characterized in that
    each heating track (804, 804', 805, 805') has at least three, in particular at least five, electrical heating resistors (806, 806', 807, 807') and/or at least three, in particular at least five, heating tracks (804, 804', 805, 805') are provided, said heating tracks preferably being able to be electrically connected to one another by means of at least one first electrically conductive means (808) and/or to a current source by means of at least two contact points (830, 830').
36. Cooking appliance comprising at least one heating element (1) according to one of the preceding claims.
37. Cooking appliance according to Claim 36,
    characterized in that
    at least one heating element (1), preferably all of the heating elements, can be releasably fastened to the cooking appliance, in particular by means of a screw connection.
38. Cooking appliance according to Claim 36 or 37,
    characterized by
    a control and/or regulating unit which is, in particular, operatively connected to at least one heating element (1), in particular to all of the heating elements, and/or to at least one electrical heating resistor (806, 806', 807, 807'), in particular to all of the heating resistors, and/or to at least one sensor.
39. Cooking appliance according to Claim 38,
    characterized in that
    the control and/or regulating unit can be used to regulate and/or control the heating power of the heating element, preferably of the individual heating resistors and/or of at least two groups of heating resistors, in particular on the basis of at least one measured variable which can be detected using the sensor, in particular, such as the temperature, the moisture, the level of browning of an item of food to be cooked, the weight of an item of food to be cooked, the size of an item of food to be cooked, the type of an item of food to be cooked and/or the like.
40. Method for producing a heating element layer (8) of a heating element (1) according to one of Claims 1 to 35, said method comprising the steps of

    - providing a substrate; and

    - applying heating resistors and electrical conductor tracks using serigraphy.
41. Method according to Claim 40, characterized in that
    at least one covering layer is then applied at least in regions.
42. Method according to Claim 40 or 41, characterized in that
    the substrate is provided with at least one electrically conductive material, preferably a metal, in particular stainless steel, a glass, a ceramic and/or a plastic, and/or at least one thermally and/or electrically insulating layer is applied to the substrate at least in regions before the heating resistors are applied.
43. Method according to one of Claims 40 to 42,
    characterized in that
    the thermally and/or electrically insulating layer is provided with at least one ceramic material and/or at least one glass.
44. Method according to one of Claims 40 to 43,
    characterized in that
    the covering layer is provided with an electrically insulating material and/or a material which protects from mechanical influences, preferably a glass and/or a protective resist.
45. Method according to one of Claims 40 to 44,
    characterized in that
    the heating power, the electrical resistance and/or the distance between the heating resistors is/are adapted by dimensioning the geometrical dimensions of the heating resistors.

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