EP0927503A1

EP0927503A1 - Radiant heating element with a metal foil heat conductor

Info

Publication number: EP0927503A1
Application number: EP97909277A
Authority: EP
Inventors: Günter Dittmar; Josef Hecht; Günther Wildner
Original assignee: AKO Werke GmbH and Co KG
Current assignee: Diehl AKO Stiftung and Co KG
Priority date: 1996-09-21
Filing date: 1997-09-16
Publication date: 1999-07-07
Anticipated expiration: 2017-09-16
Also published as: CA2263937A1; DE59705582D1; CZ98499A3; AU4703697A; DE19638640A1; ATE209845T1; WO1998012899A1; JP2001504261A; AU720572B2; EP0927503B1; PL332274A1; US6207935B1; DE19638640C2

Abstract

A radiant heating body for a cooking hob has a heating conductor comprising a metal foil and an insulating bottom (12). To make the heating conductor easy to fit and to provide advantageous heat radiation properties the flat geometrical heating conductor pattern is separated out of the metal foil. The pattern forms heating limbs (1) whose large surface is towards the cooking hob and which are held at least at an outer annular rim (13) of the insulating bottom (12).

Description

Radiant heater with a metal foil heating conductor

The invention relates to a radiant heater for a hob, in particular a glass ceramic hob, with a heating conductor made of a metal foil and with an insulating base under the heating conductor, the heating conductor running in a geometric pattern between the hob and the insulating base.

Such a radiant heater is described in DE 42 29 375 AI and EP 0 585 831 A2. The heating conductor consists of a flexible flat strip, which is laid in a spiral on the insulating floor so that its large surface is perpendicular to the insulating floor and the hob. Only its narrow top edge faces the hob. With this arrangement, the large surfaces irradiate each other.

To fix the heating conductor tape, it has holding tabs on its lower edge, which are inserted into the insulating base itself. The assembly of the heating conductor is complex because the flat strip has to be laid in spiral windings and the retaining tabs have to be pressed into the insulating base.

At the high temperatures, greater than 600 ° C, of the radiation operation, corresponding strains occur on the heating conductor, which must not lead to the heating conductor becoming detached from the insulating base.

A heating conductor is described in EP 0 175 662 B1, the flat geometric pattern of which is separated by punching from a foil lamb enclosing a metal foil. This radiator is only suitable for T Teemmppeerraattuurreenn uunntteerr 220000 °° CC ,, mmaaxx .. 440000 °° CC ,, and can therefore not be used as a radiant heater

According to EP 0 175 662 B1, two nested metal-shaped radiators are punched out of the film lambate, which reduces the punching waste.

EP 0 229 928 A2 discloses a heating element for hotplates which has a heating conductor track using flat conductor technology, preferably thick-film paste technology, which is applied to a dimensionally stable supporting element. A radiant heater in which the heating conductor track is heated up is not described there.

US Pat. No. 3,567,906 describes a sinusoidally wound flat heating wire which is laid in parallel strips under the hotplate. The flat heating wire should not be visible through the hotplate. So it is not a radiant heater, it is important that the heat conductor glows visible to the user.

DE 41 22 106 AI describes a radiant heater, the heating coil of which is held down by means of a molded part on the insulating base.

The object of the invention is to propose a radiant heater of the type mentioned, the

The heating conductor can be easily mounted above the insulating floor, the thermal expansion of the heating conductor being safely absorbed and favorable radiation properties, especially with regard to the quickly visible glowing and the efficiency, to be achieved. According to the invention the above object is achieved in a radiant heater of the type mentioned by the features of the characterizing part of claim 1.

Since the heat conductor is cut out of a metal foil, for example punched out, cut out or etched out, it is quite stable in the plane of its flat geometric pattern, this plane lying parallel between the plane of the hob and the plane of the insulating floor. The geometric pattern is, for example, star-shaped, meandering or spiral-shaped. It can also take the form of a company logo, for example a character, a characteristic sequence of letters, or letters and / or numbers.

The heating conductor can be removed in one piece from a metal foil if a metal foil is available which corresponds to the diameter of the heating conductor

Width. However, it can also be composed of several pieces, each of which forms part of the geometric pattern. The heating conductor pieces are preferably connected to one another in such widened zones that remain cold in operation compared to the heating elements.

The prefabricated heating conductor can be easily placed over the insulating floor, whereby laying processes, such as spiral winding, are omitted.

The heating elements of the heating conductor turn their large surface towards the hob. It is thereby achieved that the heating conductor takes up a large part of the surface of the hob, which is favorable

Radiation properties are achieved. The distances between the narrow edges of the heating conductor only have to be so large that the necessary electrical insulation between the heating bars is guaranteed. The available surface of the hob can be largely covered with heat conductors.

Comparative tests have shown that a

Glow time results, which is much shorter than in known radiant heaters. Since the radiating surface is large in relation to the cross section, there is good heat dissipation, which allows the heating elements to be loaded with a comparatively large current density. A short heating-up time with high efficiency is also achieved.

Another advantage is that the height of the radiant heater can be made small, or the thickness of the insulating floor and thus its thermal insulation effect can be increased for the same height.

The actual heating webs, especially in the cold and preferably also in the hot state, preferably float freely above the insulating floor. You can sag at the inevitably occurring temperature strains in the direction of the insulating floor due to the high radiation temperatures, which are above 600 ° C and can reach up to 1200 ° C, without causing a loosening of the

Heating conductor comes. The air space between the heating bars and the insulating floor was insulating. In order to reduce sagging, the rigidity of the heating webs, which are flexible per se, can be increased in that their cross-section is profiled in a U or V shape. The profiling can extend over the entire length or part of the length.

The heating conductor is preferably fixed by means of holding tabs designed on its geometric pattern, which are seated, for example, on a ring edge of the insulating base. This ring edge can be placed as a separate part on the insulating base or it can be attached to it be designed.

The outer ring edge is preferably formed by an annular outer zone of the insulating base which projects beyond the insulating base and a ring part made of thermally and electrically insulating material placed thereon, the retaining tabs engaging between the outer zone and the ring part. As a result, the heating conductor can be easily placed on the ring-shaped outer zone during assembly, taking the desired distance from the insulating base. The heating conductor is fixed by attaching the ring part.

The frictional and / or positive fixation can be improved by means of pull-throughs or claws on the retaining tabs, the pull-throughs or claws penetrating the ring part and / or downward into the ring-shaped outer zone of the insulating base by pressing the ring part upward.

In a similar way, the heating conductor can also be fixed at a central, inner location of the heating web.

In a preferred embodiment of the invention

Holding tabs so wide than the heating bars that their temperature remains below the annealing temperature during operation. It is thus avoided that the retaining tabs seated in the ring edge reach a temperature that heats the insulating material unnecessarily. In addition, in such widened, in particular comparatively cool, zones, any necessary electrical connections can also be provided so that these do not impair the service life of the heating element.

Further advantageous refinements of the invention result from the subclaims and the following description of exemplary embodiments. In the drawing demonstrate :

FIGS. 1 to 5 are top views of a heating conductor with different geometric patterns and retaining tabs in the state not yet installed in the radiant heater,

FIGS. 6, 7, 8, 10 schematically show a radiant heater in cross section with the heat conductor inserted,

9 shows a cross section of adjacent profiled hot ridges along the line IX-IX according to FIG. 7,8,

11 shows a detailed view of FIGS. 6, 7, 8, 10 of a possibility of fastening the heating conductor

FIGS. 12 to 14 show a detailed view of further fastening options,

15 shows an alternative to FIGS. 6, 7, 8, 10,

FIG. 16 shows a heating conductor with corrugation in the longitudinal direction,

FIG. 17 shows a second configuration of the corrugation,

FIG. 18 shows a third configuration of the corrugation,

FIG. 19 shows a further arrangement of the heating conductor in the radiant heater in cross section,

FIG. 20 shows a plan view of a meandering film part from which the heating conductor is to be bent,

FIG. 21 shows a heating conductor bent from its geometric pattern from the film part according to FIG. 11,

FIG. 22 shows a cross section of a further embodiment of the radiant heater, Figure 23 is a plan view of a heating conductor with lateral retaining tabs and

Figures 24 to 30 detailed views of other mounting options for the retaining tabs.

A heating conductor is cut out in a desired geometric pattern (see FIGS. 1 to 5) from a thin, equally thick metal foil with a specific electrical resistance suitable for a heating conductor, for example by a cutting process, punching process or etching process. The thickness of the metal foil is, for example, approximately 0.03 to 0.1 mm. The heating conductor is preferably in one piece, its entire flat geometric pattern lying below a circular hob of a glass ceramic plate being separated from a correspondingly wide metal foil. However, if only a less wide metal foil is available or can be processed, it is also possible to assemble the heating conductor from two or more pieces, each piece forming part of the geometric pattern.

Several heating bars (l), outer retaining tabs (2) and two power connections (3) are formed on the heating conductor. The heating bars (l) are so wide that they glow visibly during operation. The retaining tabs (2) and the power connections (3) are wider than the heating elements (l) so that they do not reach an annealing temperature when in operation.

1, the heating webs (1) run parallel in a right and left semicircle. The outer retaining lugs (2) lie on the circumference, two adjacent heating webs in each case being connected on the outside by an outer retaining lug. Two adjacent heating bars (l) are connected on the inside with an inner retaining tab (8), the heating bars (l) being electrically connected in series between the power connections (3). However, a series / parallel connection can also be designed.

The inner retaining tabs (8) lie in two rows on a diagonal zone of the circular shape (see Fig.l). The heat conductor can be fixed to the outer or inner retaining tabs (2, 8) in the manner described in more detail below.

1, extensive coverage of the circular heating surface with heating conductors is achieved. This results in heat radiation with high efficiency and a uniform glow pattern.

1 is also suitable for production from two symmetrical individual pieces. These can be electrically connected to one another at a connection point ^), for example by welding.

1 there are in the outer retaining tabs (2) and the inner retaining tabs (8) and between the power connections (3)

Stabilizing bars (5). These serve to stiffen the flexible heating conductor during transport and assembly. The cross section of each stabilizing web (5) is significantly smaller than that of a heating web (1). After the heating conductor has been installed in the radiant heater, the stabilizing bars (5) are removed, since they represent electrical short circuits. This can be done by applying an electrical voltage, for example to the power connections (3). The stabilizing bars (5) then burn out.

In the exemplary embodiment according to FIG. 2, the heating conductor is composed of six identical segments, which are connected to each other at the connection point ^ X). The heating bars (l) run parallel to each other in each segment. Here, too, there are stabilizing webs (5) in the outer retaining tabs (2). The inner ones

Halteschachen (8) are only indicated schematically. This semiconductor pattern makes good use of the heating surface and provides a star-like glow pattern.

A star-shaped heating conductor pattern is shown in FIG. 3. A pair of parallel heating elements (1) form a beam of the star-shaped pattern. All outer retaining tabs (2), each connecting a pair of heating elements, lie on the circumference. The rays are radially alternately of different lengths, the inner ones

Retaining tabs (8), each connecting a pair of heating elements, lie on circles of different diameters. A star-shaped glow pattern results during operation, a higher power density being achieved in the outer region than in the embodiment according to FIG. 4.

In the embodiment according to FIG. 4, a parallel pair of heating webs (1) forms a beam of the star-shaped pattern. Lateral retaining tabs (4) are provided on the heating webs (1), which can be bent downwards perpendicularly to the plane of the pattern and are used for guiding in recesses or grooves in the insulating base described in more detail below. However, these lateral retaining tabs (4) can also be omitted.

4 there is an inner ring on the heating conductor as a stabilizing web (5). This is only used to increase the stability of the heating element during transport and assembly. The inner ring (5), because it forms an electrical short circuit, is burned out before assembly, for example over oll break points. In operation, the heating webs (l) are electrically connected in series between the power connections (3), with εie above the holding tabs (2), which are provided at outer locations of the geometric pattern, and form the outer connecting webs (6) and are electrically connected to one another via inner connecting webs (7), which also form inner holding tabs (8).

In Fig. 5 different courses of the heating webs (l) are shown to illustrate the possibilities. Part of the heating webs (l) runs in pairs parallel to each other. Other heating webs (1 ') run approximately radially to

Center point (M). For reasons of symmetry, one or the other course can be selected for all heating webs (1,1 ') in practice.

5, the outer retaining tabs (2) protrude outwards relative to the outer connecting webs (6). The inner retaining lugs (8) project inwards relative to the inner connecting webs (7). The widths of the inner connecting webs (7) and / or the outer connecting webs (6) can, depending on the requirement, be designed such that they glow or do not glow in operation like the hot webs (1, 1 ').

6, 7, 8, 10, 15 and 24 to 30, one is mounted under a translucent glass ceramic plate (9)

Radiant heater (10) shown schematically. An insulating base (12) made of a thermally and electrically insulating material known from radiant heaters is arranged in a pot (11) made of sheet metal from the radiant heater (10). There is an outer edge (13) on the insulating base (12) for mounting the outer retaining tabs (2). 6, 7, 8, 10 and 24, 27, the edge (13) is of an annular outer zone (14) which projects beyond the insulating base (12) in the direction of the glass ceramic plate () and an annular part which can be placed thereon (15) formed. Between the annular outer zone (14) and the Rmgteιl (15), the outer retaining tabs (2) are frictional or positive held. To improve the firm fit, the openings (21) or claws described in more detail below can be provided on the retaining tabs (2), which are pressed downwards into the outer zone (14) or upwards into the ring part (15).

6, a base (17) is formed for mounting the inner retaining tabs (8) on the insulating base (12). 1 extends in the diagonal zone on which the inner retaining tabs (8) are located. The two parallel rows of the inner retaining lugs (8) (see FIG. 1) are fixed to the base (17) by means of an inner retaining part (19), which is formed by a straight retaining strip. The retaining strip consists of a ceramic material that is more dimensionally stable than the material of the insulating base (12). The holding strip is fastened to the base (17), for example by gluing or clamping, or is held by means of the ring part (15), and the holding strip (19) extends parallel to the at

Radiant radiators known rod-shaped expansion temperature sensors.

In operation, considerable thermal expansions of the heating webs (l) occur in the longitudinal direction at the usual temperatures above 600 ° C., which leads to considerable sag, particularly in the case of non-professional heating webs (l). Fig. 6 shows the sag (23) of the heating webs (l) in the hot state. The arrangement is preferably selected so that the heating webs (1) do not touch the insulating base (12) even in the hot state. In the cold state, there is a correspondingly greater distance between the large lower surface of the heating webs (1) and the insulating base (12).

FIG. 7 shows an alternative to FIG. 6. The heating webs are profiled here, as is illustrated with reference to FIG. 9, in order to increase the stability of the heating webs and thus to reduce the sag. In Fig. 7, the inner retaining tabs (8) are bent downwards in such a way that they keep the heating webs (1) at a distance from the insulating base (12). They are inserted into a holding part (19) made of electrically insulating material, for example ceramic or micanite (synthetic resin-bonded mica), which is fastened to the insulating base (12). Corresponding insertion openings can be configured on the holding part (19). The thermal expansion occurring on the heating webs (l) is absorbed by the flexibility of the inner holding tabs (8). To absorb the thermal expansion, provision can also be made for the inner and / or outer retaining tabs to be displaceable to a limited extent on their retaining parts.

8, the heating webs (l) are profiled only over part of their length and are not profiled in a length range (L). This length range (L) is slightly angled and absorbs the thermal expansion of the heating elements. The profiled length ranges can rest completely or firmly on the insulating base (12).

Fig. 9 shows a cross section of two adjacent profiled heating webs (1). This profile is made by pressing in the heating elements (l) before installation in the

Radiant heater V or U-shaped. This design has the advantage that the heating webs become more stable in the longitudinal direction and that adjacent, parallel heating webs (1) with a single one when the heating conductor is separated from the metal foil

Cut can be separated from each other without loss of material and the necessary electrical insulation distance (c) is then created by pressing in the V-shaped profile. In addition, this shape has the advantage that the radiation properties of each retaining web (1) can be influenced in a targeted manner by facing either the concave surface or the convex surface of the glass ceramic plate (9). In the embodiment according to FIG. 10 there is a step (16) between the outer zone (14) and the ring part (15) in order to be able to insert the heating conductor without touching the pot (11). The heating conductor engages with its outer holding tabs (2) between the outer zone (14) and the ring part (15), the outer holding tabs (2) not being bent out of the plane of the geometric pattern.

A base (17) projecting like the outer zone (14) in the direction of the glass ceramic plate {9) is formed in the center of the insulating base (12) and, like the outer zone (14), has a step (18). A cap (19), which, like the ring part (15), consists of an electrically and thermally insulating material can be placed on the base (17) as the inner holding part.

Passages (21) can be designed on the outer holding tabs (2) and / or the inner holding tabs (8) (cf. FIG. 11). These passages (21) can be on the

Produce metal foil in the area of the holding tabs (2, 8) simply by driving in a pointed tool, which results in metal foil tips. These engage when pressing on the ring part (15) (see FIG. 11) and / or the inner holding part (19) depending on the orientation

Ring part (15) or the holding part (19) or in the outer zone (14) or the base (17). A combination of tabs and / or claws and / or pull-throughs can also be provided. Instead of the passages (21), bent claws could also be provided at the ends of the holding tabs (2, 8). The passages or claws are used to radially secure the heating conductor in the

Radiant heater. Instead of the passages or claws, a frictional clamping of the holding tabs (2,8) by the ring part (15) and / or the holding part (19) can also be provided.

12 shows a further alternative for the definition the inner retaining lugs (8). On the Iεolιerboden (12) a ceramic base part is attached as a base (17), which is elongated in the case of the heating conductor according to FIG. 1 over the diagonal zone, in the case of the heating conductor according to FIG of the heating conductor according to FIGS. 3 and 4 is circular. About the upper edges (17 ', 17'') of the base part, the retaining tabs (8) are bent at an angle and clamped by means of U-shaped, strip-like retaining parts (19', 19 ''). A firm clamping fit is thereby achieved, which prevents the retaining tabs (8) from becoming loose during the temperature-related expansion or shrinkage. This is supported by the fact that the heating webs exert a tilting moment when shrinking onto the holding parts (19 ', 19''), which increases the clamping effect.

13 and 14 show further alternatives for fastening the retaining tabs. Embossings (8 ') are formed on the inner and / or outer retaining tabs (8, 2) (see FIG. 13), to which a toothing (17' '') of a ceramic base part (17) fastened to the insulating base (12) ) assigned. By inserting the embossments (8 ') between the toothings (17' ''), a positive fit of the retaining tabs is achieved. A similar positive connection could also be created by means of a bore and pin pair.

The assembly takes place essentially as follows: On the outer zone (14) and the base (17) the pre-made heating conductor is placed. The outer retaining tabs (2) and the inner retaining tabs (8) then lie on, the heating webs (l) running between them preferably extending at a distance (a) from the insulator base (12). The bottom big ones

Surfaces of the Heιzstege (l) are facing the Isolιerboden (12). The upper large surfaces of the Heιzstege (l) face the level of the glass ceramic plate (9). Just the narrow edges of adjacent heating webs face each other. Subsequently, the ring part (15) and the inner holding part (19) are attached to fix the outer holding tabs (2) and the inner holding tabs (8). The retaining tabs (2, 8) can thus only move to a limited extent or no longer, a certain degree of mobility in the radial direction being permitted on the outer zone (14) and / or on the base (17). In any case, the holding tabs (2,8) do not detach from their fastening points during the operational expansion and shrinkage.

The upper large surface of the heating webs (l) is thus at a distance (b) from the glass ceramic plate (9). Then the stabilizing webs (5) are then cut if necessary. In operation, when the heating webs (1) radiate visibly at temperatures above 600 ° C, a considerable temperature expansion occurs on them, so that they sag in the space (22) formed by the distance (a). This sag is designated 23 in FIGS. 6 and 10. The distance (a) is designed such that the heating webs (l) preferably do not touch the insulating base (12) when sagging.

A further metal foil part (20) as a temperature sensor can be arranged on the insulating base (12), below one or more of the heating webs (1) (cf. FIG. 10). This has a temperature-dependent electrical resistance, which is a measure of the temperature of the heating webs (1) irradiating it. The temperature sensor (20) can be connected to a temperature controller which is customary in the case of radiant heaters.

15 shows a further exemplary embodiment. There, the insulating base (12) has no outer zone (14) led up to the glass ceramic plate (9). On its outer ring edge (13) there are recesses (24) which engage in the holding tongues (2,8) which are angled downwards in this embodiment. A corresponding design with depressions (25) is used for the inner ones Retaining tabs (8) provided. For further stabilization, bent-over lateral holding tabs (4) reach into the insulating base (12). Thermal expansion is absorbed here by the play of the retaining tabs in the recesses.

16, the outer retaining tabs (2) are bent downwards and engage with play in a recess (24) in the outer zone (14). Similarly, the downwardly bent inner retaining tabs (8) engage in a recess (25) in the base (17). As a result, the heating conductor is secured radially and its thermal expansion is absorbed.

16, 17 and 18, the heating webs (1) are longitudinal, perpendicular to

Insulating floor (12) corrugated. The distance (a) to the insulating base (12) is between the wave valleys. There is a distance (b) between the wave crests and the glass ceramic plate (9). 16, the waves are uniform. 17, the wave crests or troughs are of different heights or depths. As a result, a greater radiation density is achieved in zone (A) with the higher waves than in zone (B) with the flatter waves. 18, the wavelengths are different. As a result, a greater radiation density is achieved in zone (A) with the shorter wavelengths than in zone (B) with the longer wavelengths. This makes it possible to influence the radiation density in a targeted manner in the inner and outer regions of the radiant heater.

19, the Isolιerboden (12) is concave. The Heιzstege (1) run accordingly inclined. This arrangement has the advantage that the heat radiation to the glass ceramic plate (9) is bundled. The free space (22) between the heat ridges (1) and the insulating base (12) is formed here by a circumferential groove (26) or individual pockets under the heat ridges (1). The retaining tabs are not shown. Another embodiment is shown in FIGS. 20 and 21. A straight meandering pattern (see Fig. 20) is cut out of a metal foil strip that has the width (C). The separating cuts, which are followed by the adjacent identical patterns, are located at the power connections (3).

This pattern is bent into the heating conductor shape shown in Fig. 21. For this, the inner connecting webs (7) must be shortened. This is done by corrugating the connecting webs (7) (see Fig. 21). In this form, the heating conductor is placed on the insulating base (12) and fixed to it. This design has the advantage that less metal foil waste occurs when it is separated than if the metal foil strip had the width (D) (cf. FIG. 21).

22 and 23 show further alternatives. Grooves (26) are formed on the insulating base (12), which are arranged so that they follow the course of the heating webs (1). These grooves (26) form the free space (22) between the underside of the heating webs (1) and the insulating base (12). The width of the grooves (26) is somewhat larger than the width of the heating webs (1) (cf. FIG. 22).

Extensions 27) are provided laterally above the grooves (26) to accommodate holding tabs (28) formed laterally on the heating webs (1). On the surface areas (29) of the insulating base (12), which are raised compared to the extensions 27) and the grooves (26), a flat holding part (30) which is transparent or not transparent to infrared radiation is placed, which secures the heating conductor on the insulating base (12). Above the heating webs (1), the plate-shaped holding part (30) has openings (31) which ensure free passage of the heat radiation from the heating web (1) onto the glass ceramic plate (9). The openings (31) are less wide than the extensions 27), so that the retaining part (30) can secure the lateral retaining lugs (28) in the extensions 27). The thermal expansion of the heating webs (I), which may be corrugated in the manner described, is absorbed in the grooves (26) and the openings (31). FIG. 23 shows a heating conductor with lateral holding tabs (28) on the heating webs (1), which can be arranged on the insulating base (12) in the manner described with reference to FIG. 22.

22 also shows the arrangement of the flat-band-shaped temperature sensor (20) in a groove (32) of the insulating base (12). The temperature sensor (20) is also fixed by the holding part (30). It couples thermally via the holding part (30) and openings (33) of the holding part (30) to the temperature prevailing under the glass ceramic plate (9).

24 to 27 show various other possibilities for fixing the outer retaining lugs (2) between the outer zone (14) and the belt part (15). These designs ensure that the retaining tabs (2) do not pull out from under the ring (15) by positive locking and, if necessary, supported by friction.

In the embodiment according to FIG. 24, the outer zone (14) has a slope (34) which slopes outwards towards the pot (11). A corresponding slope (35) is formed on the belt part (15). The retaining tabs (2) engage with a bend (36) between the trays (34, 35). The Umbιegungen (36) on the retaining tabs (2) can be prefabricated. However, they can also arise from the fact that the holding part (15), mounted under the glass ceramic plate (9), prints on the holding tabs (2) ) a force component that tries to pull it outwards, so that the Heιzstege (l) are stretched radially.

In the embodiment according to FIG. 25, an upward bend (37) is provided on the retaining tabs (2), which engages in a recess (38) in the belt part (15). 25, the bend (37) is bent by less than 90 ° with respect to the plane of the geometric pattern of the heating conductor. In the embodiment according to FIG. 26, the bend (39) of the retaining tab (2) is bent upwards by more than 90 ° with respect to the plane mentioned, so that a rather dimensionally stable hook is formed. This is assigned a stop (40) formed by the belt part (15), which does not allow the surrounding area (39) and thus the retaining tab (2) to slide out between the outer zone (14) and the belt part (15).

In the embodiment according to FIG. 27, a downward bend (41) is provided on the outer retaining tab (2). This is similar, as described above for the heating web (1), with a U-shaped or V-shaped cross-section. It is so stiff that it can be pressed directly into the material of the insulating base (12). This material is usually softer than the material from which the ring part (15) is made. 24 and 25 also show the passages (21) described above, which m are printed in the outer zone (14) of the insulating base (12). These passages (21) can also be provided in the exemplary embodiments according to FIGS. 26 and 27.

28, 29 and 30 show alternatives for fastening the inner retaining tabs (8). According to FIGS. 28 and 29, a holding element (1) is provided as the inner holding part. This has two rows of slots (42) for the inner retaining tabs (8) of the heating conductor (cf. FIG. 1), a separate slot being provided for each retaining tab (8). The retaining strip (19) consists, for example, of resin-bonded mica leaves (Micanite). The ends of the retaining tabs (8) are inserted through the slots (42) and bent approximately 90 ° at the top and bottom of the retaining bar (19), so that they are positively locked in the slots 42) (cf. FIG. 28). Eε is thus a fixation of the retaining tabs (8) in

Longitudinal direction (R) of the heating webs (l) and transverse direction (Q) reached. The fixation in the longitudinal direction (R) ensures that the heating webs (1) within the ring part (15) have the necessary tension. The fixation in the transverse direction (Q) ensures that the retaining tabs (8) cannot slip so that adjacent heating webs (1) touch.

28 and 29 can sit on and / or be fastened to a base (17) of the insulating base (12) described above. However, the retaining strip (19) can also float freely above the insulating base (12). The retaining lugs (8) are attached to the retaining strip (19) before the heating conductor is inserted into the pot (11).

FIG. 30 shows a design of the inner holding part (19) similar to that of FIGS. 10 and 12. Here, bends (44) of the retaining tabs (8) engage in a base (17) which is fixed on the insulating base (12). The bends (44) are firmly clamped in the base (17) by a holding part (19) made of ceramic material which is pressed into the base (17). 1, the base (17) and the holding part (19) are strip-shaped. For heating conductors in which the inner retaining lugs (8) lie on a circle, the base (17) and the retaining member 1) are correspondingly circular.

Instead of the fastening of the holding tabs (8) to the holding bar (19) by bending, as described with reference to FIGS. 28 and 29, it is also possible to sew the holding tabs (8) onto the holding bar (19). For this purpose, a commercially available heat-resistant thread or thread, in particular made of ceramic fiber material. When sewing on, the retaining loops (8) and the retaining strip (19) are pierced. The end result is also a fixation of the holding tabs (8) on the holding strip (19) in the longitudinal direction () and in by the sewing

Transverse direction (Q) reached. If necessary, the retaining tabs (8) can also be sewn with two retaining strips (19) lying one on top of the other, the retaining tabs (8) then lying between the two retaining strips (19). Sewing with a ring-shaped carrier can also be carried out on the outer retaining loops (2). This ring-shaped carrier and the holding strip (19) can form an integral molding. Sewing takes place before the heating conductor is inserted into the pot (11) or onto the insulating base (12). The heat conductor sewn onto the molded part is then placed as a prefabricated assembly in the pot (II) or on the insulating base (12), with all retaining tabs being fixed in their desired position. Then the ring part (15) can then be put on.

Numerous further exemplary embodiments are within the scope of the invention. For example, it is possible to combine partial features of the designs with one another.

Claims

claims

1. Radiant heater for a hob, in particular glass ceramic hob, with a heat conductor made of a metal foil and with an insulating base under the heat conductor, the heat conductor running in a geometric pattern between the hob and the insulating base, characterized in that the geometric heat conductor pattern is separated from a metal foil that the heating conductor pattern forms heating webs (l), the thickness of which is substantially smaller than their width and the large surface of which faces upwards and which are held at least on an outer ring edge (13) of the insulating base (12).

2. Radiant heater according to claim 1, characterized in that the insulating bottom (12) facing the underside of the heating webs (l) extends at least partially at a distance above the insulating base (12).

3. Radiant heater according to claim 1 or 2, characterized in that holding tabs (2, 4, 8, 28) are formed on the metal foil in the plane of the geometric pattern.

4. Radiant heater according to claim 3, characterized in that the retaining lugs (2) are formed at least at external locations of the geometric pattern and are held on the outer ring edge (13) of the insulating base (12).

5. Radiant heater according to claim 3 or 4, characterized in that the holding tabs (2, 4, 8, 28) are held on the insulating base (12) by means of a holding part (15, 19, 30).

6. Radiant heater according to one of the preceding claims 3 to 5, characterized in that the retaining tabs (2,4,8,28) are so wider than the heating webs (1) that their temperature remains below the annealing temperature during operation.

7. Radiant heater according to one of the preceding claims, characterized in that the outer ring edge (13) of an annular, raised outer zone (14) of the insulating base (12) and a ring part (15) placed thereon is formed from thermally and electrically insulating material , wherein the outer retaining tabs (2) engage between the outer zone (14) and the ring part (15).

8. Radiant heater according to one of the preceding claims, characterized in that the holding lugs (2,, 8, 28) are frictionally and / or positively held.

9. Radiant heater according to one of the preceding claims, characterized in that passages (21) and / or claws are formed on the holding tabs (2, 4, 8, 28), which are formed in the material of the insulating base (12) and / or the ring part (15) and / or the holding part (19) engage.

ιo. Radiant heater according to one of the preceding claims, characterized in that the retaining lugs (2, 4, 8, 28) are opposite the plane de geometric pattern are bent and to absorb the thermal expansion of the Heιzstege (l) in recesses (24, 25) of the insulating base (12) with play or bendable.

ιι. Radiant heater according to one of the preceding claims, characterized in that the inner holding tabs (8) are formed at inner locations of the flat, geometric pattern of the heating conductor and that the inner holding tabs (8) are held on a base (17) of the insulating base (12) .

12. Radiant heater according to claim 11, characterized in that the inner Haltelaεchen (8) on the base (17) are held by means of a Halteteιls (19) which is fixed to the base (17).

13. Radiant heater according to claim 11, characterized in that the base (17) is formed by a base part attached to the Iεolιerboden (12), around at least one edge (17 ', 17' ') of the inner holding tabs (8) and bent are clamped by means of at least one holding part (19, 19 ', 19' ').

14. Radiant heater according to one of the preceding claims, characterized in that the outer retaining tabs (2) lie on a circumference of the heating conductor and the inner retaining lugs (8) lie on a diagonal zone of the heating conductor and the heating webs (l) run parallel to one another.

15. Radiant heater according to one of the preceding claims 1 to 13, characterized in that the outer Halteschaεchen (2) on a circumference circle of the heating conductor and the inner retaining tabs (8) lie on at least one concentric circle, the heating webs (l) running in pairs in parallel.

16. Radiant heater according to one of the preceding

Claims, characterized in that an outer retaining tab (2) and an inner one

Retaining tab (8) in pairs running parallel to each other

Heιzstege (l) connects together.

17 radiant heater according to one of the preceding

Claims, characterized in that the surrounds (41) of the retaining lugs (2, 8) are profiled in cross-section and are pressed into the material of the insulating bottom (12).

18. Radiant heater according to one of the preceding claims, characterized in that surrounds (36) of the outer retaining lugs (2) are clamped between an outwardly sloping slope (34) of the insulating base (12) and a corresponding slope (35) of the ring part (15) are.

19. Radiant heater according to one of the preceding claims, characterized in that Umbιegungen (37) of the outer retaining tabs (2) in a

Grab recess (38) of the ring part (15).

20. Radiant heater according to one of the preceding claims, characterized in that hook-like surrounds (39) of the outer retaining tabs

(2) a stop (40) of the Rmgteιls (15) is assigned.

21. Radiation heater according to one of the preceding claims, characterized in that the holding tabs (2, 8) are inserted through slots (42) of a holding part (19) and are bent over to the wide sides thereof.

22. Radiant heater according to claim 21, characterized in that daε HalteteiK 19) on a base (17) deε

Insulating floor (12) rests or hovers freely above the insulating floor (12).

23. Radiant heater according to one of the preceding claims, characterized in that the holding tabs (2, 8) are sewn onto a holding part.

24. Radiant heater according to one of the preceding claims, characterized in that in the heating webs (l) in their cross section V or

U-shaped profile is embossed.

25. Radiant heater according to one of the preceding

Claims, characterized in that the heating ridges (l) are at least partially corrugated in the longitudinal direction, perpendicular to the insulating base (12).

26. Radiant heater according to claim 25, characterized in that the heights of the wave crests and / or wave troughs and / or wavelengths are designed in such a way that there is a different radiation density.

27. Radiant heater according to one of the preceding claims, characterized in that current connections (3) are formed on the geometrical pattern of the heating conductor, which are so wider than the heating webs (1) that their temperature remains below the annealing temperature during operation.

28. Radiant heater according to one of the preceding claims, characterized in that the distance (a) between the underside of the heating webs (1) and the Isolιerboden (12) is created in that in the Isolιerboden (12) grooves (26) are formed.

29. Radiant heater according to one of the preceding claims, characterized in that the geometric pattern based on the

Glass ceramic plate (9) is deformed concavely.

30. Radiant heater according to claim 29, characterized in that the insulating base (12) like the heating conductor is concave, or has a recess under the heating conductor.

31. Radiant heater according to one of the preceding claims, characterized in that the heating conductor on the insulating base (12) holding plate (30) in the region of the heating webs (l) is provided with openings (31).

32. Radiant heater according to one of the preceding claims, characterized in that the geometrical pattern of the heating conductor is composed of several pieces which are separated from a flat metal foil.