EP1276350B1 - Electrical radiating heating device with active sensor recognizing cooking ustensil - Google Patents

Abstract

The radiant heating element comprises a sensor (21) which is formed straight and without ties. The sensor has section which runs over the heating zone (17) which in turn has a straight electric conductor. The heating element is arranged on a metal plate which has two connections for the sensor. The sensor is electrically insulated against the metal plate in at least one end region (22). An Independent claim is also included for a hub with electric heating elements.

Description

Field of application and state of the art

The invention relates to an electric radiant heater with an active sensor for detecting the positioning of a cooking vessel on a cooking plate covering the radiator according to the preamble of claim 1.

Such sensors, as they are known for example from DE 196 03 845 A1, are used to detect whether and possibly where a cooking vessel is on the hotplate. The heater is activated only when the cooking vessel is attached. This is done on the one hand to avoid wasting energy by not fitted cooking vessels and on the other hand the risk of burning or destruction of objects by hot, so to speak, open-running hotplates.

The sensor according to DE 196 03 845 A1 is formed as a loop of wire, which runs substantially in a round shape between the radiator and hotplate. The placement of a corresponding metallic cooking vessel causes a change in the inductance of the sensor loop. This change is detected by an associated electronics as placing a cooking vessel. Depending on this, the heating can be activated as intended. Difficulties arise from the attachment of the sensor to the radiant heater. Furthermore, there are problems with the mass of the sensor, in particular in a so-called drop test, in which the sensor can damage, for example, a glass ceramic plate as a hob.

Task and solution

The invention has for its object to provide an aforementioned electric radiant heater in which the attachment of the sensor is simplified to the radiant heater and the sensor has an improved structure.

This object is achieved by a radiant heater having the features of claim 1. Advantageous and preferred embodiments of the invention are contained in the subclaims and will be described in more detail below. The wording of the claims is incorporated herein by express reference.

According to the invention, the sensor is formed without a loop, in contrast to the known and common round sensor loops or coils. He runs substantially straight, preferably at least in the essential sections of its course. It particularly preferably runs in the region of the radiant heater or the heating zone exclusively in a substantially straight line. In the context of the present invention, loopless means that the sensor is not completely or completely closed loop forms for the most part. The sensor preferably does not limit any area in its course.

Under "straight" should also be understood not too curled or similarly trained sensor. Finally, this also runs in one direction or its course can be described with it.

A sensor according to the invention has the advantage that the structure can be considerably simplified. On the radiant heater is not an entire, circumferential loop to install, which may also have several turns, but only straight sections. These can be fastened, for example, with at least one end to the edge of the radiant heater or a surrounding this insulation. Furthermore, loop-shaped sensors have the disadvantage that they do not accurately detect the central zone of the radiant heater because they do not directly cross it. Due to their circumferential, loop-like character, no section can be passed through this central area. By contrast, guiding a straight sensor over this central area is not a problem.

Surprisingly, with the invention it has been possible, for example, to detect both the placement of a cooking vessel and its size and even its position with two wires stretched in parallel over a multi-circle heating element.

Furthermore, it has surprisingly been found that the sensor can have only one section running over the heating zone, for example, it can be designed as a straight electrical conductor. It can range from one edge of the radiant heater to above its middle, preferably to the other edge. Such a sensor does not include any surface at all. Here, surprisingly, the function or the recognition accuracy as well as the parallel conductors described above as sensors. Depending on the set threshold of an associated electronics can be decided whether a cooking vessel was placed on or whether this cooking vessel size or position is accepted.

Advantageously, the sensor extends across a heating zone or the entire radiant heater. In this case, it is possible, in particular in the case of a sensor with a single conductor or section, with great advantage to use radiant heaters which have a metal plate which substantially supports or contains the radiant heater. The metal plate can be designed as a return conductor or second connection for the sensor. So can be omitted here consuming additional connection work. It has surprisingly been found that thereby the function of such a cooking vessel detection sensor is not affected. This may be such that the sensor is electrically insulated from the metal plate of the radiant heater at least at one of its end regions. With this insulated end portion it is connected to an externally accessible first electrical connection. The other end of the sensor is electrically connected to the metal plate, directly or indirectly. In a particularly simple embodiment, a second electrical connection needs to be attached only at an arbitrary position on the metal plate in order to be electrically connected thereto.

A particularly preferred embodiment provides such that a connection possibility or a connector for the sensor contains both connections in a connection block. For this purpose, the connection block can be fastened to the radiant heater or the metal plate in the vicinity of a sensor end. When using the metal plate as a return conductor or second electrical connection, it is very easy to tap this signal at any point or to arrange the connector stone very close to one end of the sensor.

Advantageously, the sensor extends centrally over the heating area of the radiant heater. This can ensure that a cooking vessel placed on the associated hotplate covers the sensor in almost any sensible position and allows it to be detected. In the case of a radiant heater having a plurality of heating regions, the sensor can run over more than one heating region, in particular all heating regions.

It is also possible to arrange the sensor only separated areas overlapping. Thus, a position detection of a cooking vessel for this separated area can be achieved. This is the case, for example, with laterally arranged additional heaters for oblong roasters or the like. advantageous.

According to one possibility of the present invention, it is possible to attach the sensor to the radiant heater in such a way that, when the radiant heater is mounted, it runs a short distance below a cooking plate to which the radiant heater is mounted. This small distance can be 0.1mm to 10mm, preferably be very small and be a few 1 / 10mm. As a measure of this distance, the upper edge of the radiant heater surrounding the insulating plate or the like can be taken, which rests in the mounted state on the underside of the hotplate.

In a further embodiment of the invention, the sensor may have at least one of its ends a height adjustment, so that a desired distance can be set accurately. Such a height adjustment can, for example, have a slot, preferably in a direction perpendicular to the plane of the radiant heater, on the radiant heater itself. Along this slot, the sensor can then be adjusted in height.

On the one hand, it is possible to make the sensor rigid, preferably as a thick wire or tubular. For a tubular sensor, in particular, a metal tube offers itself, which can be electrically insulated to the outside. In one possible embodiment of the invention, the sensor can be combined with a rod regulator usually used for radiant heaters. In this case, the metallic outer tube of the rod controller can form the sensor or be used as an electrical conductor for this. Thus, a combined assembly can be created, which requires considerably less installation effort.

Advantageously, a commonly used rod controller can be grown with a residual heat contact to the radiant heater and designed as a sensor. If the residual heat contact of the rod controller is not required, the space that has become free in the rod regulator can be used as a connection block for the sensor connection.

According to another possibility of the invention, the sensor may be elastic or flexible. For this purpose, a wire, a wire or a metal band to offer. These can be stretched over at least a portion of the heating area and gain their stability by the tensioning.

In the context of the invention, spring means can be provided to compensate for a thermally induced change in length of the sensor. Alternatively or additionally, the spring means may be used for supporting at least one end of the sensor and / or for maintaining the voltage and thus the shape of the sensor. It should be noted that if the position of the sensor is a factor, the spring means should be constructed so as to allow for accurate, position-defined mounting. Furthermore, the spring force should be matched to the time / Temperaturdehngrenze the sensor material or to the cross section of the sensor. This can ensure that the system sensor / spring means is optimally matched. Preferably, a leaf spring is used as the spring means, which can even be punched out and exposed in an embodiment of the invention, even from the metal edge of the support plate for the radiant heater.

It is possible to attach or store the sensor with at least one end by means of spring means on the radiant heater. In this case, the spring means can be electrically insulated from a metal plate for receiving the radiant heater. However, particularly preferably, the spring means serve just for electrical connection of the sensor to the metal plate, which is then used as a return conductor or second electrical connection.

The sensor should be resistant to scale, so as not to be attacked or damaged by the high temperatures in the heating zone. Furthermore, it is advantageous if the material of the sensor has no Curie point. Otherwise, distortions of the measurement results could occur.

In addition, in a commonly used rod regulator described above, it is possible to incorporate a noble metal temperature measuring resistor. Such measuring resistors are, for example, a PT 100 or a PT 1000. In this case, the noble metal Temperaturmeßwiderstand can be exchanged for the ceramic part of the rod controller. In this case, the outer tube of the rod controller may be formed as a sensor and as a holder for the noble metal Temperaturmeßwiderstand.

Finally, the invention also comprises a hob with a plurality of radiant heaters, wherein at least one of the radiant heaters, advantageously all, can be formed in the manner described above.

A necessary sensor electronics for the evaluation of signals of the sensor should of course be present. It may be formed as described, for example, in DE 196 03 845 A1, the content of which is made explicit reference to the content of this description

Brief description of the drawings

Fig.1

einen Querschnitt durch einen erfindungsgemäßen Strahlungsheizkörper, bei dem ein Stabregler den Sensor bildet,

Fig. 2

eine Draufsicht auf den Strahlungsheizkörper aus Fig. 1,

Fig. 3

einen Querschnitt durch eine alternative Ausführung mit einem gespannten Draht als Sensor und

Fig. 4

eine Draufsicht auf den Strahlungsheizkörper aus Fig. 3.

Embodiments of the invention are illustrated in the drawings and will be explained in more detail below. In the drawings show:

Fig.1

a cross section through a radiant heater according to the invention, in which a rod controller forms the sensor,

Fig. 2

a plan view of the radiant heater of FIG. 1,

Fig. 3

a cross-section through an alternative embodiment with a tensioned wire as a sensor and

Fig. 4

a plan view of the radiant heater of FIG. 3rd

Detailed description of the embodiments

Figures 1 and 2 show in cross section a radiant heater 11 according to the invention, which is formed substantially in the usual manner. This means that in a metal plate 12 with laterally raised edge 13, a flat insulating body 14 is arranged with a peripheral edge piece 15. On the insulating body 14 of the heating element 16 of the radiant heater is laid, for example in meandering turns, see Fig. 2. Right is attached to the metal plate edge 13, a connection block 18 of a rod controller. In addition, further electrical connections 19 are provided for the heating conductors 16 of the radiant heater 11.

The tube 21 of the rod controller of the connecting block 18 extends across the entire radiant heater 11 or metal plate 12 away. With its left end 22 it is stored in the insulating edge piece 15 or even stands a little bit beyond.

According to the invention, the metal tube 21 of the rod regulator is designed as a pot detection sensor. As can be seen from FIG. 2, the sensor 21 extends over the entire metal plate 12 or radiant heater 11 and thus covers in any case a heating zone 17 formed by the heating conductors 16. The electrical contacting of the tube or sensor 21 takes place in the right-hand area on the one hand by the fact that the sensor is connected either directly to the metal plate 12 and its edge 13 via the attachment of the rod controller as a ground. Since the sensor 21 passes through the metal plate edge 13, can be provided as an alternative possibility, an electrical contact, for example by simple concern or corresponding resilient contact means. The electrical contacting of the left other end of the sensor 21 takes place at the end 22, which, as can be seen in Fig. 1, extends through both the edge piece 15 and through the metal plate edge 13 and a Bits over the edge 13 protrudes. A attached to the end 22 piece of flexible metal strand 24 is guided to a male lug 25 of a connecting block 27. The connecting block 27 is attached to the metal plate edge 13 and is made in the usual way of insulating, preferably ceramic material. It is important that the sensor end 22 has no contact with the metal plate edge 13 in the region of the opening. For this purpose, the breakthrough may be formed sufficiently large, since a bearing protection of the end 22 anyway by means of the penetration through the insulating edge 15 takes place. Another, even more reliable method is to isolate the breakthrough or a hole or cutout with a kind of electrically insulating shell, such as plastic or ceramic, inwards. In this way, a storage of the sensor end 22 also take place on the metal plate edge 13.

The metal plate edge 13 in turn is connected via a further flexible metal wire 28 with the second plug connection lug 26 of the connecting block 27. Thus, the contacting of the sensor 21 takes place at one end via the sensor end 22 and the metal strand 24. At the other end, it takes place via the metal strand 28 and the plate rim 13. As an alternative to the metal seat 28, the connection lug 26 could be connected directly to the metal plate 12 or even be bent out of this.

As alternatives to the possibility according to FIGS. 1 and 2, it is conceivable to provide a plug connection lug 26 in the area of the connecting block 18 of the bar regulator or sensor 21. This could indeed account for the signal line on the metal plate, this brings electrically or functionally, however, no clear advantage. For this it is of great importance if a single terminal block 27 is provided for both terminals 25 and 26 of the sensor 21, so that the assembly or contacting by means of plugs or the like is very simple and error-free possible. In this embodiment, it would also be possible, the metal wire 28 from the connecting block 27 to the other end of the sensor 21 in the area lead of the connecting block 18 of the rod controller. While this is possible, it means significantly increased effort and therefore is more expensive compared to the illustrated and described option.

Furthermore, it is possible in the embodiment according to FIGS. 1 and 2, via the attachment of the connecting block 18 of the rod controller and / or the holder of the other end 22 of the sensor 21 whose position and thus future position below a glass ceramic plate, the radiant heater 11 covered, set or adjust.

In Figures 3 and 4, a similar radiant heater 111 is shown with a metal plate 112, a metal plate edge 113, an insulator 114 and two annular edge pieces 115a and 115b. The inner edge piece 115a divides the heating zone via the heating conductors 116 into an inner heating zone area 117a and an outer heating zone area 117b. A rod regulator 130 is shown in Fig. 4 in excerpts and corresponds to a conventional rod controller to protect against overtemperature, but here has no connection with the sensor function.

On the right metal plate edge 113, a leaf spring 131 is screwed or riveted, which protrudes with its long resilient leg at an angle of about 20 ° from the metal plate edge 113. At the end of the leaf spring 131, a sensor wire 121 is fixed, wherein the attachment is electrically conductive. The sensor wire 121 runs across the radiant heater 111 in each case through corresponding cutouts 133 in the edge pieces 115a and 115b, wherein it covers the heating zone regions 117a and 117b.

At the left end of the metal plate 112 and its edge 113, a connection block 127 is attached, which corresponds to that of FIGS. 1 and 2. The sensor wire 121 is directly on an upwardly projecting Section of a plug-in lug 125 mounted in the connecting block 127 such that it is held straight by the leaf spring 131 by tension. In accordance with the sensor contacting of FIGS. 1 and 2, the other plug connection lug 126 is connected to the metal plate edge 113 by means of a flexible metal strand 128 and thus to the sensor 121 via the leaf spring 131. In this way, the sensor 121 is contacted via the two plug connection lugs 125 and 126 in a single connection block 127. The advantages of this single connection point and alternatives thereto correspond to those which have been described above with reference to FIGS. 1 and 2.

From the connection block 27 or 127 from a connection cable can be performed to a corresponding cooking vessel detection electronics. This can be combined with other electronics for controlling the radiant heater or an entire hob.

In the embodiment according to FIGS. 3 and 4, it is possible to configure the portion protruding from the connecting lug 126, to which the sensor wire 121 is fastened, flexibly in the direction of the sensor in the manner of a leaf spring or the like. In this case, it would be possible to attach the other end of the sensor 121 directly to the metal plate. Thus, the leaf spring could be saved 131 together with attachment. As a further possibility, a corresponding strip could be punched out of the rim 113 and be bent laterally, in order to replace in this way a leaf spring 131 or its complex attachment.

Furthermore, it is conceivable to guide a bar regulator with a sensor tube or a stiff sensor from the edge only a little way beyond the center of the radiant heater. There can be attached via a bottom of the sensor-supporting portion of a metal part of both the sensor attached and an electrical contact at the end can be achieved. This can then be analogous to the flexible metal strands be led to a connection block or the like, wherein the metal strands should be isolated for this purpose. This design can also be realized with a flexible wire as a sensor accordingly.

Instead of a sensor wire 121, in the embodiment according to FIGS. 3 and 4, a thicker wire, possibly not flexible, can be used. Again, the leaf spring 131 corresponding spring means can be used for attachment to at least one end.

It is within the scope of the invention possible to attach one end of the sensor directly to a terminal lug of a connecting block. This has the advantage that any other attachment for this end is superfluous. When contacting a sensor end by means of or via the metal plate or its edge, it must be ensured that the sensor is insulated at its other end from the metal plate.

It can be seen from the two exemplary embodiments that attachment of a sensor, which consists in particular of only a single straight conductor, is very simple. For this purpose, only two attachment points are needed. Another great advantage of these embodiments is that both terminals and connection leads are very simple by the use of the metal plate as a conductor. By attaching the sensor with one end to the metal plate, a significant simplification in construction can be achieved here as well. This causes less installation effort and thus less costs and sources of error.

Claims (16)

1. Electric radiant heater (11, 111) with an active sensor (21, 121) for detecting the positioning of a cooking vessel on a hotplate covering the heater, in particular a glass ceramic plate, wherein the sensor (21,121)

   - consists of electrically conductive material,

   - is part of a resonant circuit which operates inductively, preferably by resonant circuit detuning, of a control,

   - is positioned in the region of at least one heating zone (17, 117) heated by electric radiant heating elements (16, 116) and at least partly covers said heating zone, characterised in that the sensor (21, 121) runs in a linear manner and is configured without the formation of a completely or predominantly closed loop.
2. Radiant heater according to claim 1, characterised in that the sensor (21, 121) only has one portion extending over the heating zone (17, 117), it preferably being a straight electric conductor.
3. Radiant heater according to either claim 1 or claim 2, characterised in that the sensor (21, 121) extends transversely over a heating zone (17, 117) and/or the radiant heater (11, 111).
4. Radiant heater according to any one of the preceding claims, characterised in that the radiant heater is located in a metal cup (12, 112) substantially carrying said radiant heater, and this metal cup (12, 112) is configured as a return conductor or a second connection for the sensor (21, 121), the sensor (21, 121) preferably being electrically insulated at at least one end region (22) relative to the metal cup, a first electrical connection (24, 124) leading directly to the sensor and a second electrical connection (28, 128) leading to the metal cup (12, 112) which is in turn electrically connected to the sensor.
5. Radiant heater according to any one of the preceding claims, characterised in that the sensor (21, 121) passes centrally over the heating area (17, 11 7) of the radiant heater (11, 111) and in the case of a radiant heater (111) having a plurality of heating areas (117a, 117b) the sensor (121) preferably passes over a plurality of heating areas, in particular over all heating areas.
6. Radiant heater according to any one of the preceding claims, characterised in that the sensor (21, 121) is fitted to the radiant heater (11, 111) such that when the radiant heater is assembled, the sensor passes at a distance of from 0.1 mm to 10 mm below the hot plate, said sensor preferably having a height adjustment at at least one of the ends thereof.
7. Radiant heater according to any one of the preceding claims, characterised in that the sensor (21) is rigid, preferably tubular, being in particular an outwardly electrically insulated metal tube.
8. Radiant heater according to claim 7, characterised in the sensor is combined with a conventionally used rod regulator such that the metallic outer tube of the rod regulator forms the sensor (21).
9. Radiant heater according to either claim 7 or claim 8, characterised in that a conventionally used rod regulator is fitted to the radiant heater (11) with a residual heat contact, the residual heat contact of the rod regulator not being required and the space made available as a result thereof in the rod regulator being configured as a connecting member (18) for the sensor connection.
10. Radiant heater according to any one of claims 1 to 6, characterised in that the sensor (121) is constructed resiliently and/or flexibly and is stretched over at least a portion of the heating area (117a, 117b), it preferably being a wire, a braid or a metal strip.
11. Radiant heater according to any one of the preceding claims, characterised by spring means (131) for compensating a thermally induced change in length of the sensor (121) an/or for maintaining the tension of the sensor and/or for supporting at least one end of the sensor, the spring force being matched to the time/temperature expansion limit of the sensor material and/or to the cross-section of the sensor (121), the spring means preferably comprising a leaf spring (131).
12. Radiant heater according to claim 11, characterised in that the sensor (121) is fastened to the radiant heater (111) by at least one end by means of the spring means (131), said spring means (131) in particular being electrically insulated from a metal disk (112) for holding the radiant heater (111).
13. Radiant heater according to any one of the preceding claims, characterised in that the sensor (21, 121) is non-scaling.
14. Radiant heater according to any one of the preceding claims, characterised in that the material of the sensor (21, 121) has no Curie point.
15. Radiant heater according to any one of the preceding claims, characterised in that a precious metal temperature measuring resistor, preferably a PT100 or PT1000, is installed in a fitted, conventionally used rod regulator, the precious metal temperature measuring resistor being exchanged for the ceramic part of the rod regulator and the outer tube of the rod regulator being configured as a sensor (21) and as a holder for the precious metal temperature measuring resistor.
16. Cooking area with a plurality of electric radiant heaters, characterised in that at least one of the radiant heaters (11, 111) is configured according to one of the preceding claims.

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