EP4151908A1 - Heating device for a hob and hob with such a heating device - Google Patents

Abstract

A heating device for a hob has a flat or planar carrier, which has a heating conductor side with heating conductors on it and a switching device, the switching device having a movable switching contact and a counter-contact assigned to it. The switching device has an internally movable switching arm which carries the switching contact and is electrically connected to an electrical arm connection means, the switching arm being fastened to the carrier. The mating contact is electrically connected to a mating electrical connection means and attached to the carrier. The switching arm is formed from a bimetallic strip. Switching arm, switching contact and counter-contact are designed and arranged such that when a structurally specified switching temperature is exceeded, the switching contact and counter-contact are brought together by moving the switching arm due to increasing heating to trigger a switching process as a hot indicator for the hob.

Description

Field of application and state of the art

The invention relates to a heating device for a hob and a hob with such a heating device, the heating device preferably being a warming heater.

From the US 2013/0146585 A is a heating device for a hob known with a very low power. In this way, cooking vessels placed above it in a hob can be kept warm. The heating device requires only a small amount of power, for example between 50W and 150W.

task and solution

The invention is based on the object of creating a heating device as mentioned at the outset and a hob provided with such a heating device, with which problems of the prior art can be solved and in particular it is possible to create a practical and easy-to-install heating device that is preferably produced inexpensively can be.

This object is achieved by a heating device having the features of claim 1 and by a hob having the features of claim 18. Advantageous and preferred configurations of the invention are the subject matter of the other claims and are explained in more detail below. Some of the features are only described for the heating device or only for the hob. However, independently of this, they should be able to apply independently both to such a heating device and to such a hob. The wording of the claims is made part of the content of the description by express reference.

The heating device is designed for use in a hob and has a flat or planar support, the support having a heating conductor side and an opposite rear side. Furthermore, it has at least one heating conductor on the heating conductor side and a switching device, the switching device having a movable switching contact and a counter-contact assigned to this switching contact. The shifting device has a shifting arm which can be moved or is movable in itself and which is preferably deformed or can bend as a result of the thermal effect. For example, it can form a warm display or the usual hot display for the heating device on the hob, so that an operator It is pointed out that the hob is hot or dangerous at the point of heating. This also applies if the heating device does not generate particularly high temperatures due to the relatively low installed power, but only around 80°C to 150°C. The switching arm supports the switching contact and is electrically connected to an electrical arm connection means, the switching arm being fixed to the carrier. In particular, it is attached to the carrier with an end area. The mating contact is electrically connected to an electrical mating connection means, preferably it is also attached to the carrier. The switching arm has a bimetallic strip or is formed from a bimetallic strip. Switching arm, switching contact and counter-contact are designed and arranged such that when a structurally specified switching temperature is exceeded, the switching contact and counter-contact are either separated by moving the switching arm due to increasing heating or are brought together to trigger a switching process. This switching process serves to signal the heating to an operator or in general, for example by means of a conventional hot indicator. Due to cooling, the switching arm then moves in the opposite direction for a complementary switching process, which reverses the signaling.

Although the switching arm is made of a bimetal, it is advantageously not designed as a snap switch. The switching arm is particularly advantageously designed without a snap function. So it can be designed simpler and cheaper as well as more robust and less error-prone. Due to the low currents to be switched, a particularly fast switching process is also not required, neither when closing a contact nor when opening it.

The switching contact is arranged on a free end of the switching arm, in particular it is arranged on a side of the switching arm which points towards the carrier. In this case, the switching arm can advantageously be flat. So it can be particularly easy to move.

The switching arm is preferably a bimetallic strip and consists of straight sections and/or sections which are bent at a maximum of 45° or are bent by a maximum of 45°. The change in course can either be continuous due to the bend or be sharp or angled at an edge. So he can be easily trained. Particularly preferably, the switching arm can consist of two straight sections that are connected to one another at an angle. Due to the angling, a precise shape and a change in shape that can be precisely predetermined can be set.

In a possible development of the invention, the switching arm is in turn a bimetallic strip and consists of straight sections and/or consists of sections that are between 15° and are angled at 90° to one another or bent accordingly. This means that adjacent sections each have a corresponding angle to one another. The shifting arm can advantageously consist of exactly or at least three sections, in particular three straight sections. These can be a fastening section for fastening to the heating device, a central section and a switching contact section which is in turn connected thereto and carries the switching contact. An aforementioned angle can be provided between these three sections. In particular, it can be provided that the fastening section and the switching contact section run parallel to one another, ie they are offset parallel to one another or the switching arm has a type of Z shape. In practice, it has been shown that advantages in terms of dimensional accuracy can be achieved and a simpler measurement of a contact spacing is possible. As a further possibility, the fastening section and the switching contact section can be longer than the central section, advantageously twice to ten times as long as the central section.

Alternatively, the switching arm can be slightly bent at the attachment section for attachment to the heating device or angled at a small angle to a first section of the middle section. The shifter arm may have a center section angled in on itself, preferably with two sections of the center section. These two sections can be angled at a relatively small angle to one another, advantageously between 1° and 20° or between 5° and 12°. This allows the attachment portion to lie flat and parallel to the bracket and be attached. The first section of the middle section, which is directly connected to the fastening section, raises the shifting arm slightly above the carrier, but advantageously not too far, so that the shifting arm is still strongly heated by the carrier. A second section of the middle section is angled relatively sharply in relation to the first section, for example by the aforementioned angle of between 15° and 90° or between 40° and 50°. This second section is preferably shorter than the first, in particular approximately as long as in the previously explained configurations. This is followed by the switch contact section or a free end with the switch contact, which is advantageously angled in such a way that it runs parallel to the first section of the middle section. In comparison to the aforementioned configuration, the more strongly angled second section of the middle section and thus also the switching contact section is higher above the fastening level of the switching arm.

A curved design of the switching arm advantageously consists of a continuous bend which runs over at least a portion of its length. It is thus possible to fasten the switching arm at one end with a flat side on the carrier. The angling or bending makes it possible for the switching arm to run over the carrier and thus also to run at a distance over the mating contact. Due to warming Due to the heating conductor and the bimetallic properties, the switching arm bends with increasing temperature and can move the switching contact to the counter contact or press against it from a predetermined switching temperature and thus trigger the switching process. In the cold state or at room temperature, the switching contact is then at a distance from the mating contact, and in the hot state it is in contact with this.

In another embodiment, the switching arm can be straight when it is mounted on the carrier. It can rest with the switching contact on the mating contact with a precisely defined preload, for which purpose it is pre-bent. When heated, the switching arm bends or the switching contact then moves away from the counter-contact above a predetermined switching temperature. In the hot state, the switching contact is then at a distance from the mating contact, but in the cold state or at room temperature it is in contact with this. The switching process is then exactly the opposite of what it was before. There are two options. The switching temperature can be selected in such a way that a temperature of between 50°C and 90°C prevails on a hob plate above the heating device.

In a further refinement, the shifting arm has a fastening section which, in particular, has a length of between 10% and 30% of the total length of the shifting arm. It is therefore relatively short, but advantageously has no other function than fastening the shifting arm. The length of the rest of the switching arm can preferably be movable and thus deform, in particular due to the bimetallic effect. The switching contact can be arranged on a free end area of the switching arm, advantageously just before the end. It should be located on the side of the shifter arm that faces the wearer, i.e. on the underside.

The switching contact can advantageously have a protruding edge or cutting edge in order to form a line contact when it rests against a surface, in which case the edge or cutting edge can advantageously run in a longitudinal direction of the switching arm. In this way it can be ensured that the switching contact actually makes an electrical contact when it is in contact with the counter-contact, regardless of the deflection of the switching arm or its free end.

In yet another embodiment of the invention, the switching arm can be fastened immovably to the carrier together with the arm connection means, so that an electrical connection to the switching arm is direct or goes directly to it. For this purpose, an aforesaid fastening section can be provided, which can be connected to the arm connection means or can bear against it. The switching arm can advantageously be riveted to the carrier, which is a permanent and secure connection.

Advantageously, a form-fitting connection of the switching arm to the carrier or to the electrical arm connection means can be provided on the fastening section, with a holding projection and a holding recess being particularly advantageously provided for this form-fitting connection. The form-fitting connection should be able to prevent twisting of a switch arm that is fixed or rotatable at one point, so that its switch contact always rests against the intended counter-contact when it is moved due to heating. The retaining projection is preferably provided on the fastening section, advantageously as an elongate projection, arm or nose projecting from the end of the fastening section in the same direction. The holding recess can be provided on the arm connection means, preferably as a recess or hole, in which case the holding projection can be introduced or plugged in there when the switching arm is assembled. After it has been attached to the carrier, the switching arm is in any case aligned exactly as desired, as a result of which a reliable electrical contact can be achieved between the switching contact and the mating contact. For this purpose, the switching arm can be fastened resting on the switching contact, so there is still a section of the switching contact between the switching arm and the carrier.

Alternatively, the switching arm can be mounted directly adjacent to the carrier, in particular under the arm connection means. For this purpose, the carrier should be electrically insulating or have a cover layer that forms electrical insulation. The arm connection means presses the shift arm against the carrier so that it is attached thereto, advantageously with the aforesaid attachment portion. This has the advantage that the switching arm is arranged and runs very close to the carrier and is thus also heated very quickly and directly, at least closer than if it were mounted on top of the arm connection means. This can shorten the switching time or the response time. A configuration of the shifting arm described above is particularly suitable for this purpose, which has a middle section bent twice. In this case, it should preferably be provided that the arm connection means does not press the shifting arm onto the carrier over a length that is too great, so that the shifting arm can also move freely with the middle section.

In a further development of the invention, the switching arm can be in the form of strips and/or have an elongated rectangular shape, in particular can be designed with the same width as desired. Its length can be at least 2 times greater than its width, preferably at least 3 or 5 times greater than its width. This applies in particular to the area of the switching arm which can move or which is not attached to the carrier, which means that it is, so to speak, non-deformable or immovable. These dimensions are therefore advantageous for the area of the switching arm, which can deform due to temperature changes and at least move with the switching contact. The width and/or a thickness of the switching arm can remain the same.

So the production is also very easy. Furthermore, the switching arm can be designed in such a way that it has no incisions and/or interruptions in the outer shape, ie has a closed outer contour. So it can be designed very simply. In addition, such a deformation can be as uniform as possible, so that the shifting arm deforms and moves evenly for a defined shifting behavior. In this way, the switching process can advantageously take place at a predetermined temperature.

In a first embodiment of the invention, the counter-contact is arranged in a fixed and immovable manner on the heating device, in particular it rests directly or indirectly on the carrier. Then the formation of the heating device is very simple. The mating contact can thus advantageously be fastened to the carrier together with the mating connection means, which is in particular a plug connection or a plug connection lug. Similar to the shift arm, it can be attached by riveting. It is possible that the counter-contact is part of the counter-connection means or a rivet for riveting. According to a first possibility, such a rivet can form the counter-contact, so that it serves as a contact for the switching contact in addition to its fastening function. It is possible for the mating contact to be connected to a mating connection means or to be attached to the carrier together with a mating connection means. In this way, attachment and electrical contact can in turn be combined. According to a second possibility, the mating contact can be formed by the mating connection means itself. In this case, an elevation or a type of rib can protrude from the counter-connection means and form the counter-contact, in particular protrude in the direction away from the carrier or towards the switching contact.

In a second embodiment of the invention, the counter-contact is movably or is movably arranged on the carrier, in particular arranged on a counter-contact arm which is fastened to the carrier. The counter-contact arm can be designed to be deformable or resilient in such a way that it yields in this direction, i.e. can move or deform, with increasing force with which the switching arm presses the switching contact against the counter-contact and thus against the counter-contact arm as the temperature increases. This allows the counter contact to move, i.e. away from the switching contact or its pressure. Preferably, it can yield or move in a direction towards the wearer.

In general, the switching arm can preferably rest directly on the carrier and be fastened to the carrier together with the arm connection means placed thereon. In this case, the arm connection means and underneath the switching arm can be riveted to the carrier. As a result, the switching arm is arranged relatively close to the carrier and can thus be heated quickly and directly by it, which is advantageous for rapid switching. The contact of the shift arm directly on the carrier or a covering layer provided thereon can also reduce or prevent twisting of the shifting arm, for example around a rivet for attachment. Alternatively, it is also possible for the switching arm to rest on a named arm connection means and thus be at a slightly greater distance from the carrier, if this is desired.

In a development of the invention, the carrier can be electrically insulated or have electrically insulating material, in particular it can have mica or mica. The carrier can consist of at least 90% or even all of mica or mica.

The at least one heating conductor can be applied permanently and inseparably to the carrier, in particular it can be applied as a layer. It can preferably be printed on as a thick-film heating conductor.

The heating conductor can lead to a contact pad that is applied to the carrier, with the switching device preferably also being able to be connected to at least one contact pad. In this case, two free ends of the heating conductor can each go to a contact pad, with the two contact pads being able to have a distance from one another of between 1 cm and 10 cm.

In one configuration, the switching device can be arranged outside of a heating area covered by the at least one heating conductor; it can preferably be arranged between the heating conductor and an outer edge of the carrier. In particular, it can be arranged between an outermost heating conductor and an outer edge of the carrier. The distance means that the switching device is not so close to the heating conductors, i.e. it is not heated up too much or too quickly.

In another embodiment, the switching device can run over at least one heating conductor, i.e. above it, so that at least one heating conductor runs between the mating contact on the carrier and the attachment of the switching arm on the carrier, specifically below the switching arm. The switching arm can run directly over at least one heating conductor or over two heating conductors. Thus, in contrast to the embodiment directly described above, it can be achieved that the switching device is exposed to the heating effect relatively directly because it runs above it. The switching device can then be actuated very quickly, so that a hot indicator switched by it is activated very quickly and can thus warn an operator. The switching device is advantageously arranged between a central area and an outer edge of the carrier, particularly advantageously closer to the outer edge than to the central area.

A hob according to the invention has a heating device as described above, the hob having a hob plate with an upper side and an underside and the heating device being arranged with the rear side facing the underside of the hob plate, in particular being placed against the underside of the hob plate. The hob has a hot indicator device with a light source, wherein the light source can be switched on and off by the switching device and is connected to the switching device for this purpose. This takes place at a certain aforementioned temperature.

A current for such a hot indicator can be low, so the demands on the switching device are not very high. The light source can advantageously be a glow lamp or an LED. Glow lamps have the advantage that they are very temperature-resistant, so they can also be arranged under a hob plate.

These and other features emerge from the claims, the description and the drawings, with the individual features being realized individually or in combination in the form of sub-combinations in one embodiment of the invention and in other areas and are advantageous and protectable in their own right Designs may represent for which protection is claimed here. The subdivision of the application into subheadings and individual sections does not limit the general validity of the statements made under them.

Brief description of the drawings

Fig. 1

eine Schrägansicht von unten auf eine erfindungsgemäße Heizeinrichtung mit einem Träger und einer erfindungsgemäßen Schalteinrichtung daran,

Fig. 2

eine Abwandlung der Heizeinrichtung aus Fig. 1 mit dargestellten Heizleitern, wobei die Schaltarme über zwei solche Heizleiter verlaufen,

Fig. 3

eine Seitenansicht auf einen abgewinkelt ausgebildeten Schaltarm der Schalteinrichtung,

Fig. 4

eine Draufsicht auf den Schaltarm aus Fig. 3,

Fig. 5

eine Seitenansicht der Schalteinrichtung aus Fig. 1 mit dem Schaltarm aus Fig. 3, was dessen Formveränderung zeigt,

Fig. 6

eine Abwandlung des Schaltarms aus Fig. 3 mit kontinuierlich gebogenem Schaltarm,

Fig. 7

eine Einbausituation der Heizeinrichtung als Warmhalte-Heizeinrichtung in ein erfindungsgemäßes Kochfeld,

Fig. 8

eine Abwandlung des Schaltarms aus Fig. 3 mit zwei Abwinkelungen,

Fig. 9

der Schaltarm aus Fig. 8 in einer Anordnung ähnlich Fig. 5,

Fig. 10

eine Schrägansicht auf die Anordnung des Schaltarms am Träger nach Fig. 9

Fig. 11

eine Abwandlung der Anordnung aus Fig. 9, bei der ein nach Fig. 3 ausgebildeter Schaltarm unter einem Arm-Steckanschluss direkt auf dem Träger befestigt ist,

Fig. 12

eine Abwandlung des Schaltarms aus Fig. 8 mit zwei Abwinkelungen im Mittelabschnitt und

Fig. 13

eine Abwandlung der Anordnung aus Fig. 11 mit dem Schaltarm aus Fig. 12.

Exemplary embodiments of the invention are shown in the drawings and are explained in more detail below. In the drawings show:

1

an oblique view from below of a heating device according to the invention with a carrier and a switching device according to the invention on it,

2

a modification of the heating device 1 with shown heating conductors, whereby the switching arms run over two such heating conductors,

3

a side view of an angled switching arm of the switching device,

4

a top view of the shift arm 3 ,

figure 5

a side view of the switching device 1 with the shift arm 3 , showing its shape change,

6

a modification of the shift arm 3 with continuously curved shift arm,

7

an installation situation of the heating device as a warming heating device in a hob according to the invention,

8

a modification of the shift arm 3 with two bends,

9

the shift arm off 8 in a similar arrangement figure 5 ,

10

an oblique view of the arrangement of the switching arm on the carrier 9

11

a modification of the arrangement 9 , at the one after 3 trained switching arm is attached directly to the carrier under an arm plug connection,

12

a modification of the shift arm 8 with two angulations in the middle section and

13

a modification of the arrangement 11 with the shift arm 12 .

Detailed description of the exemplary embodiments

In the 1 a heating device 11 according to the invention is shown obliquely from below. The heating device 11 is designed as a so-called warming heater, as is known per se from the prior art and will also be explained in more detail below. She will, as in 7 is shown, applied to a hob plate from below and can keep a pot T placed above it, including its contents, warm.

The heating device 11 has a planar and flat or planar carrier 12 which advantageously consists of electrically insulating material. This is particularly advantageous mica or mica. Alternatively, it can be made of ceramic. In yet another alternative, it can be made of metal, for example steel, and be electrically insulated on one side 14 of the heating conductor, for example by means of an electrically insulating coating. A design made of mica or mica is considered advantageous since the material and processing costs required for this are low.

On the heating conductor side 14, heating conductors 22 shown in dashed lines run in different forms, as in FIG 2 is also shown in more detail. These cannot be seen here because they are covered by a cover layer 16, which can advantageously consist of mica, similar to the carrier 12. This cover layer 16 forms electrical insulation, so that spacers 28, for example, can be attached thereto as metal springs by riveting. These spacers 28 are known per se, it is on 7 referred.

A connection area 18 is provided on the side of the carrier 12, on which the cover layer 16 is cut out, so to speak. In the connection area 18, on the one hand, two plug-in connections 20a and 20b are provided, which are connected to the heating conductors 22 or the heating conductors 22 emanate from these. For example, the plug-in connections 20a and 20b can be placed on contact pads at the end of the heating conductor 22 and mechanically fastened by riveting and electrically connected to them.

In addition to the plug-in connections 20a and 20b, a switching device 30 according to the invention is arranged in the connection area 18 and near the outer edge, so that it takes up as little space as possible on the heating conductor side 14 and at the same time has the greatest possible distance from the heating conductors 22, in particular for the aforementioned thermal reasons. The switching device is then heated as late or as little as possible by the heating conductors 22, as has been described above as one embodiment. The switching device 30 mainly has a switching arm 32 which is elongated and straight and very simple. He is subsequently in the 3 ff. described in more detail.

At the left end, the switching arm 32 is fastened to the carrier 12 with a fastening section 34 together with an arm plug connection 45 by means of a rivet 44 . The fastening section 34 or the switching arm 32 and the arm plug connection 45 are electrically connected to one another.

Below the right-hand free end 40 of the switching arm 32, which forms the aforementioned switching contact section, a mating plug-in connection 50 is fastened to the carrier 12 with a rivet 48 as a mating contact. The upper rivet head 47 forms the explicit mating contact for a switching contact 42 of the switching arm 32. Otherwise, the switching device 30 or the switching arm 32 and the plug-in connections 45 and 50 are not electrically connected to anything else, in particular to nothing on the carrier 12 on the heating device 11 .

In the 2 an alternative embodiment of a heating device 111 is shown, but without the cover layer 1 , which should advantageously be made of mica as previously described. In the connection area 118, a plug-in connection 120a is arranged on the left, from which an arcuate contact track 121a branches off to the left. From this contact track 121a, three heating conductors 122 of different designs and different shapes and widths extend. They each form a circuit counterclockwise and end at a right-hand arcuate contact track 121b, which is connected to a right-hand plug connector 120b. This is how the electrical contact is made to the heating conductors 122.

while at the 1 the switching device 30 is arranged in the connection area 18 and thus outside the area of the heating conductors 22 2 the switching device 130 is deliberately arranged in such a way that it covers at least the innermost path of the heating conductors 122. Included the two heating conductors 122 run under the switching arm 132 so that they heat the switching device 130 directly. The switching device 130 above the heating conductor 122 can therefore switch particularly quickly here because it is heated very quickly and directly.

The arm plug-in connection 145 and the mating plug-in connection 150 are either separated by an insulating layer, and are sometimes attached directly above the heating conductor 122 . Alternatively, they are fixed in areas left free by the heating conductors 122, in any case they should be electrically separated from them. Otherwise, the structure of the switching device 132 is exactly as before 1 described. In the case of 2 the switching device 130 will of course heat up much faster and reach a higher end temperature than in the case of the 1 , which is why the configuration of the switching device 30 should be somewhat different. Alternatively, it simply speaks much faster.

In the 3 is shown in enlargement of the switching arm 32 in side view. It has a fastening section 34 on the left, which is connected to the free part 39 by means of a bend 37 . In the cold state or at room temperature, there is an angle of about 10° here, and the free part 39 is exactly straight. The switching arm 32 is formed of a bimetal, with an upper layer, the in 1 points away from the heating conductor side 14, is formed from the metal with the larger coefficient of thermal expansion. The layer applied below has the lower coefficient of thermal expansion. Thus, the switching arm 32 bends as it heats up, as shown in figure 5 is shown, down.

In the mounting portion 34 a hole 35 is attached, which from the 4 can be seen. So for arranging the figure 5 a rivet 44 can be pushed through, with the downwardly angled part of the arm plug connection 45 having a corresponding hole being placed first on the heating conductor side 14 of the carrier 12 at the top. The switching arm 32 with the fastening section 34 is then placed on it, and then the rivet 44 is used for riveting Attachment portion 34 is connected and also electrically connected.

The free part 39 has a constant width and also a constant thickness, like the rest of the entire switching arm 32. At its right free end 40, the free part 39 has a switching contact 42 at the bottom. This is advantageously designed as a blade contact or has an elongate blade that runs in the longitudinal direction of the switching arm 32 . This is how switching takes place along a line. Because with the switching device 30 only a small current for a hot display has to be switched, the switching contact 42 does not need to be very complicated and/or to be provided with expensive materials.

From the 4 it can be seen that for a mating contact to the switching arm 32 the mating plug connection 50 is placed with the lower angled section on the heating conductor side 14 and then fastened by means of a rivet 48 . The upper rivet head 47 of the rivet 48 forms the counter-contact on which the closed state figure 5 the switching contact 42 is present. The electrical contact between the arm plug connection 45 and the mating plug connection 50 is thus closed. For the low currents mentioned, the rivet head 47 is entirely sufficient as a counter-contact. Costs for a further separate contact or contact head can thus be saved, and this also does not have to be fixed in any other way.

In the figure 5 it can be seen how the switching arm 32 is broken at room temperature and the switching contact 42 is clearly above the rivet head 47 as a mating contact. When the heating device 11 begins to heat up due to current flowing through the heating conductor 22, the switching device 30 and thus also the switching arm 32 also become warmer. A maximum temperature of the heating device 11 in the area of the heating conductors 22 can be around 120° C., possibly also up to 20° C. above or below. Accordingly, there is a temperature at the switching device 30, which leads to the deformation of the bimetallic switching arm 32, which begins to bend downwards and thus to press the switching contact 42 in the direction of the rivet head 47 as a counter-contact. At a certain temperature and after a certain time, for example a temperature of about 65°C at the switching arm 32 and a time of one minute, the switching arm 32 has deformed so much and bent down due to the bimetallic effect that the switching contact 42 on Rivet head 47 is applied. Thus, a circuit can be closed, which either directly activates a lamp for said hot display or is used in a controller, in particular a microprocessor, as a switching signal, which is then displayed elsewhere. It is significant here that the heating device 11 itself is not influenced or switched in its heating function with the switching device 30 .

The temperature may possibly rise even further as the heating device 11 continues to operate, but this ultimately only leads to an even further deflection of the switching arm 32 towards the carrier 12 . Due to the concern of the switching contact 42 on the rivet head 47 as a counter-contact, however, it cannot move any further here. The left attachment portion 34 is also fixed. This then leads to the switching arm 32 nevertheless being deformed even more strongly towards the carrier 12 . Depending on the further increase in temperature and further deformation, relatively large forces can occur here under certain circumstances. These must include the switching device 30 and the carrier 12 can either endure constructively. Alternatively, it would also be possible to provide not only a rigid mating contact on the rivet head 47, but a kind of short spring arm that extends a little away from the rivet 48 and is therefore movable at its free end in the direction of the carrier 12. This free arm can then be pushed towards the carrier 12 by the further force of the switching arm 32 . This provides a type of overpressure protection and thus also a type of overload protection against damage.

A thickness of the switching arm 32 can be between 0.1 mm and 0.5 mm, which means that it can be achieved that it carries out the movement accordingly in any case due to heating figure 5 . At the same time, however, the development of force can be limited at even higher temperatures, so that the risk of damage remains low.

In the 6 an alternative switch arm 232 is shown. It has no bend, but here a straight fastening section 234 merges into the free part 239 in a constant bend. Also this free part 239 is not straight but bent with the same bend. It can be provided that in the cold state or at room temperature a switching contact 242 at the free end 240 of the free part 239 is just as high above a plane on which the fastening section 234 rests, as in the angled switching arm 3 . Due to the continuous bending, its very high force, with which the switching arm 232 presses against the carrier or a counter-contact at high temperature, can possibly be better absorbed.

In the 6 dashed lines show the shape of switching arm 232 at high temperature or at a temperature at which it is likely to be in contact with its switching contact 242 against a counter-contact. This form is not much different than according to figure 5 , however, there is no mechanical weakening due to the deflection or it is necessary.

In the 7 a hob 55 according to the invention is shown in simplified form. The hob 55 has a hob plate 56, advantageously consisting of glass ceramic, with an underside 57. A heating device 11 according to the invention is pressed onto this underside 57 by means of the spacers 28. Further heating devices are advantageously arranged here, but not according to the invention, but so-called radiant heating devices with a significantly higher output. A pot T is set up above the heating device 11 and is to be kept warm together with its contents at a temperature of approximately 60°C to 70°C.

The heating device 11 is connected by means of the switching device 30 to a hot indicator 60 in the form of a glow lamp. Furthermore, it is connected to a controller 59 via which power is supplied to the hot indicator 60. Thus, the hot indicator 60 is always activated when the switching device 30 is closed. As long as the switching device 30 is closed, the hot indicator 60 is also activated. If the heating device 11 is deliberately switched off after a certain period of operation or by an operator, the temperature also drops again. If it falls below a certain value, the switching arm 32 of the switching device 30 bends back so far that the switching contact 42 moves away from the rivet head 47 as a counter-contact. The hot indicator 60 is de-energized and disabled. An exact switching temperature can be set for this. As is customary and known for such hot displays, these should be set in such a way that there is a temperature of 60° C. on the top of the hob plate 56 in the area above the heating device 11 and as a result or at the same time the hot display 60 is activated to warn an operator becomes. In addition, the information about the switching of the switching device 30 can also be processed in the controller 59 .

In the 8 a further possible embodiment of a switching arm 332 according to the invention is shown in a side view. The switching arm 332 has a kind of Z-shape with a fastening section 334 on the far left, a middle section 336 and a free part 339. Between the fastening section 334 and middle section 336 there is a first bend 337a with approximately 60° or 120° between the two sections . A second corresponding bend 337b is provided between the middle section 336 and the free part 339, so that the fastening section 334 and the free part 339 run parallel to one another. The attachment section 334 is about three times as long as the middle section 336, and the free part 339 is about six times as long as the middle section 336. The free part 339 also has a switching contact 342 on its free end 340 on the underside.

In the 9 in side view and in the 10 according to FIG 8 arranged on a heating device 311 according to the invention. The fastening section 334 is fastened to a carrier 312 of the heating device 311 by means of a rivet 344 together with an angled arm plug connection 345 . The free end 340 with the switching contact 342 rests on a rib 351 of a mating plug connection 350 which is fastened to the carrier 312 by means of a rivet 348 . The arm connector 345 and the mating connector 350 are advantageously of identical design, which reduces the number of parts required. The rib 351 can be produced by stamping or bending in it and forms the previously explained counter-contact for the switch contact 342. From the side view it can be seen clearly that a movement of the switch arm 332 due to heating and the bimetallic effect causes the switch contact 342 to counter-contact the rib 351 presses.

In the 10 It can also be seen that a narrow, elongated retaining projection 341 protrudes in the same direction from the fastening section 334 in the manner of an arm or a nose. This one is also in 8 not drawn in, but recognizable in terms of its design. The holding projection 341 can be 2 mm to 5 mm long. It is inserted or plugged into a slightly larger retaining recess 346 on the arm plug connection 345, which is done before the two parts are attached to the carrier 312 by means of the rivets 344. It is clearly evident that the switching arm 332 cannot be rotated or can only be rotated slightly about its attachment to the rivet 344 by the retaining projection 341 in the retaining recess 346 . This ensures that the position of the switching arm 332 and its switching contact 342 relative to the rib 351 as a counter-contact is always essentially unchangeable and enables reliable switching. A corresponding holding recess can also be seen in the mating plug connection 350 . In addition, this holding recess 346 can simplify the angling of the arm plug connector 345 .

In the 11 is shown as a switch arm 432 corresponding Figures 3 and 4 is formed, is attached to a heating device 411 or on a cover layer 416 of a carrier 412. In this case, the difference falls to figure 5 that the switching arm 432 rests directly on the cover layer 416 with a fastening section 434 . An arm connector 445 is fitted from above and secured to the bracket 412 by a rivet 444 similar to that previously described. A right-pointing area 452, at the end of which a rib 451 is arranged, runs above the free part 439 of the switching arm 432. In order to allow for this upward movement space, this area 452 is slightly bent upwards.

A mating plug-in connection 450, which has the same design as the arm plug-in connection 445 and is arranged in a mirror-inverted manner, is fastened directly to the carrier 412 or its cover layer 416 by means of a rivet 448. On the left-facing area 453, a rib 451 is in turn provided for a switching contact 442 at the lower end of the right-hand free end 440. In FIG 11 it can be clearly seen that compared to figure 5 the switching arm 432 is arranged closer to the carrier 412 and thus closer to the heat source. For this reason, the switching device 34 with the switch 432 reacts more directly or more quickly when heated, ie when the switching arm 432 is to move downwards to close the contact between the switching contact 442 and the rib 451 as a counter-contact.

In the 12 yet another modification of a switching arm 532 is shown. A left first center section 536a adjoins a fastening section 534 on the extreme left. The angle between the two is approximately 80°, so that the left first central section 536a is bent or angled by approximately 10° in relation to the attachment section 534 . To the right the left-hand or first middle section 536a is adjoined by the right-hand second middle section 536b at an angle of approximately 50°. To the right, with a further bend of the same size of approximately 50°, it merges into the free end 540, which has a switching contact 542 on its underside. The left first center section 536a and the free end 540 run approximately parallel to one another and are, so to speak, offset from one another in the manner of steps by means of the right second center section 536b. Thus, it is in the switching arm 532, so to speak, a switching arm according to 3 , which shortly before the free end 540 with a short spaced double bend corresponding to the switching arm according to FIG 8 is provided.

In the 13 the shift arm 540 is off 12 Part of a switching device 530 on a heating device 511. The switching arm 540 is placed directly on a cover layer 516 on a carrier 512 of the heating device 511. It is held in place from above by an arm connector 545 and rivet 544. The arm connector 545 is designed exactly as for 11 described.

At a distance to the right, an identical mating plug connector 550 arranged in a mirror-inverted manner is fastened directly to the carrier 512 by means of a rivet 548 . The vertical distance between the switch contact 542 and a rib 551 on the mating connector 550 is slightly less than the vertical distance of the point at the bend between the left middle section 536a and the right middle section 536b. Thus, the switching contact 542 rests securely against the rib 551 before the right-hand area of the left-hand middle section 536a strikes the cover layer 516 of the carrier 512. This ensures that the switching arm 532 can be bent downwards until the contacts 542 and 551 close, before the switching arm 532 strikes the carrier 512 with a movable area, so to speak.

Claims (18)

Heating device for a hob, the heating device having: - a flat or planar carrier, the carrier having a heating conductor side and an opposite rear side, - at least one heating conductor on the heating conductor side, - a switching device, the switching device having a movable switching contact and a counter-contact assigned to this switching contact, characterized in that - the switching device has a movable or moveable switching arm, - the switch arm carries the switch contact and is electrically connected to an electrical arm connection means, - the shifting arm is attached to the carrier, in particular with an end area, - the mating contact is electrically connected to an electrical mating connection means, preferably attached to the carrier, - the switching arm has a bimetallic strip or is formed from a bimetallic strip, - Switching arm, switching contact and mating contact are designed and arranged in such a way that when a structurally specified switching temperature is exceeded, the switching contact and mating contact are either separated by moving the switching arm due to increasing heating or are brought together to trigger a switching process. Heating device according to Claim 1, characterized in that the switching contact is arranged on a free end of the switching arm, in particular on a side of the flat switching arm which points towards the carrier. Heating device according to Claim 1 or 2, characterized in that the switching arm is a bimetallic strip and consists of straight sections and/or consists of sections which are angled by a maximum of 45° or correspondingly bent by a maximum of 45°, the switching arm preferably being designed without a snap function is, in particular the switching arm consists of two or three straight sections that are connected to each other at an angle. Heating device according to Claim 1 or 2, characterized in that the switching arm is a bimetallic strip and consists of straight sections and/or sections which are angled between 15° and 90° or bent accordingly, with the switching arm preferably consisting of three sections, namely a fastening section for fastening to the heating device, a middle section and an adjoining switching contact section which carries the switching contact, with in particular the fastening section and the switching contact section run parallel to one another and/or are each twice to ten times as long as the middle section. Heating device according to Claim 3 or 4, characterized in that the switching arm has a fastening section, in particular with a length of between 10% and 30% of the total length of the switching arm, the length of the remaining switching arm preferably being movable and having the switching contact on a free end region. Heating device according to one of Claims 3 to 5, characterized in that the switching arm has an angled central section, with two sections of the central section preferably being angled at an angle of between 1° and 20° to one another. Heating device according to one of the preceding claims, characterized in that the switching arm, in particular with a fastening section according to one of claims 4 to 6, is fastened immovably to the carrier together with the arm connection means, the switching arm preferably resting directly on the carrier and together is fastened to the carrier with the arm connection means placed thereon, wherein in particular the arm connection means and, underneath, the switching arm are riveted to the carrier. Heating device according to Claim 6 or 7, characterized in that a positive connection to the carrier or to the electrical arm connection means is provided on the fastening section, a retaining projection and a retaining recess being provided for this positive connection, the retaining projection preferably being on the fastening section is provided, wherein in particular the holding recess is provided on the arm connection means. Heating device according to one of the preceding claims, characterized in that the switching arm is strip-shaped and/or has an elongated rectangular shape and its length is at least 2 times greater than its width, preferably at least 3 times greater than its width, the width of the switching arm in particular remaining constant is, preferably without cuts and / or interruptions in the outer shape. Heating device according to one of the preceding claims, characterized in that the counter-contact is arranged fixedly and immovably on the heating device, in particular bears directly or indirectly on the carrier. Heating device according to Claim 10, characterized in that the mating contact is attached to the carrier together with the mating connection means, preferably a plug connection or a plug connection lug, in particular by riveting, the mating contact preferably being part of a rivet for riveting the mating connection means is or is part of the counter-connection means itself, in particular as a protruding elevation or rib of the counter-connection means. Heating device according to one of Claims 1 to 9, characterized in that the counter-contact is movably or movably arranged on the carrier, in particular is arranged on a counter-contact arm, the counter-contact arm being fastened to the carrier and being designed to be spring-elastic in such a way that with increasing force, with which the switching arm presses the switching contact against the mating contact as the temperature increases, the mating contact arm yields in this direction and the mating contact moves, preferably yielding or moving in a direction towards the carrier. Heating device according to one of the preceding claims, characterized in that the carrier is electrically insulated or has electrically insulating material, in particular mica or mica, the carrier preferably consisting of at least 90% or completely of mica or mica. Heating device according to one of the preceding claims, characterized in that the at least one heating conductor is applied firmly and inseparably to the carrier, in particular is applied as a layer, with the heating conductor in particular leading to a contact field which is applied to the carrier, preferably to the Contact field the switching device is connected, with two free ends of the heating conductor preferably going to one contact field each, with the two contact fields being at a distance from one another of between 1 cm and 10 cm, with the counter-contact or the switching arm with the switching contact being electrically connected to one contact field . Heating device according to one of the preceding claims, characterized in that the switching device is arranged above a heating area covered by the at least one heating conductor, in particular runs directly over at least one heating conductor or over two heating conductors, the switching device preferably being arranged between the outer edge and a central area of the carrier is, in particular, is arranged closer to the outer edge than to the central region. Heating device according to one of Claims 1 to 14, characterized in that the switching device is arranged outside of a heating area covered by the at least one heating conductor, preferably between the heating conductor and an outer edge of the carrier. Heating device according to one of the preceding claims, characterized in that the switching contact has a protruding edge or cutting edge in order to form a line contact when it rests against a surface, the edge or cutting edge preferably running in a longitudinal direction of the switching arm. Hob with a heating device according to one of the preceding claims, wherein the hob has a hob plate with an upper side and an underside and the heating device is arranged with the rear side facing the underside of the hob plate, in particular is placed against the underside of the hob plate, the hob having a Hot indicator device has a light source, the light source being able to be switched on and off by the switching device and being connected to the switching device for this purpose, the light source preferably being a glow lamp.

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