EP2464194B1 - Heater for domestic applications - Google Patents

Description

The invention relates to a heater for household appliances, which has at least one heating track with at least one curved Heizbahnabschnitt.

There are known by screen printing on enameled steel heaters with a Heizleiterschicht for kettles and dishwashers known. For uniform and complete heating of square heating surfaces, the heat conductor layer has heating tracks, which are also equipped with corners. However, this leads to the effect of current displacement, that is, the current, which always takes the shortest path, provides for an uneven heat distribution, possibly even heat overload, in the corners. In order to set a current flow and thus a heat output along the heater, so far additionally electrically conductive bridges can be printed. However, a precise current guidance is difficult to realize by means of the electrically conductive bridges, in particular with angular Heizbahnabschnitten.

DE 10108662 A1 discloses a heater with the features mentioned in the first part of claim 1.

It is the object of the present invention to provide a particularly simple and versatile way of adapting a current flow in curved Heizbahnabschnitten a heater for household appliances.

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

The object is achieved by a heater for household appliances, comprising at least one heating track with at least one curved (non-linear) Heizbahnabschnitt, wherein the heating track has at least one locally limited recess in the region of the curved Heizbahnabschnitts. Through the recess, a distribution of a current flow over a width of the curved Heizbahnabschnitts be unified and consequently a temperature inhomogeneity across the width are at least reduced.

The recess may generally be in the form of a simple, non-closed cut. The recess may additionally or alternatively also in the form of a closed Section may be present, wherein an area enclosed by the cut area may be filled or excluded with the material of the heating track.

It is an embodiment that the curved Heizbahnabschnitt has at least one recess, which follows the shape of the curved Heizbahnabschnitts. The curved Heizbahnabschnitt can thereby be divided into two or more parallel heating tracks. Inhomogeneities of the current flow and thus the temperature can then advantageously occur only on the reduced in their width parallel heating tracks.

It is still an embodiment that the curved Heizbahnabschnitt has a plurality of recesses, which are at least partially arranged in parallel over a width of the Heizbahnabschnitts so that they form at least partially parallel heating strip with substantially equal partial resistances. The provision of the same partial resistances causes a unification of the current flow across the width and can, for example, take into account a length of the Heizbahnstreifen and so on

It is also an embodiment that the curved Heizbahnabschnitt has a plurality of recesses same basic shape, which are distributed or arranged equidistantly over a width of the Heizbahnabschnitts. These are especially easy to design and implement.

It is yet another embodiment that the curved Heizbahnabschnitt has a recess which rounds off a curved edge of the Heizbahnabschnitts, in particular a edge-fitting recess with a constant radius. Thus, a width of the curved Heizbahnabschnitts particularly easy to keep constant.

If the rounded curved Heizbahnabschnitt has at least one recess, which follows the shape of the curved Heizbahnabschnitts, this may be present in particular in the form of a rounded angled, in particular at right angles or by 180 ° angled line.

It is a special embodiment that the two curved edges of the recess have such a respective radius, that a respective curved edge of the recess and an opposite edge of the heating path, a heating strip of constant cross-sectional width limits. Thus, two or more parallel Heizbahnstreifen can be produced with a substantially constant width.

It is still an associated development that the recess has rounded ends.

It is still an embodiment that the curved Heizbahnabschnitt has a recess which rounds off a curved edge of the Heizbahnabschnitts, in particular by means of an edge-fitting recess, in particular with a constant radius. Thus, the Heizleiterbahn can be narrowed to standardize the width.

It is still a development that the recess converts the rounded curved edge into a more rounded curved edge.

It is a specific embodiment that the radius of the recess corresponds to at least approximately an original radius of the curved Heizbahnabschnitts plus a width of the curved Heizbahnabschnitts a subsequent rectilinear Heizbahnabschnitts or a width at a transition to a subsequent rectilinear Heizbahnabschnitt. As a result, in particular a heater with a flat or area-effect heating surface (surface heating) can be provided in an effective manner.

It is also an embodiment that the heating path fills a rectangular area.

It is a development that the heating track substantially completely fills a rectangular area.

It is a further development that the heating track substantially fills a rectangular area in the shape of a frame, thus leaving an inner area free. The inner region is preferably also rectangular.

It is also a development that the heating track has an at least partially spiral course.

It is also a development that the heating track has an at least partially meandering course.

The manner of introducing the at least recess is not limited, but may include any suitable method, e.g. laser cutting, mechanical cutting, micro-machining, etching or other material-removing processes.

The heating track may comprise an electrically conductive heating conductor layer. The heating conductor layer may be applied directly to a substrate to be heated, in particular if the substrate is an electrically non-conductive substrate, e.g. made of plastic. The heating conductor layer may alternatively be applied indirectly over an electrically insulating insulating layer on a substrate to be heated, in particular if the substrate is an electrically conductive substrate, e.g. made of metal. The at least one recess can extend at least completely through the heating conductor layer.

The heat conductor layer may in particular consist of CrNi. In this case, a thickness of the heating conductor layer between one and 300 micrometers, in particular between 25 and 50 micrometers, is preferred.

The insulating layer preferably comprises a dielectric material, preferably aluminum oxide. A thickness of the insulating layer between 150 and 500 micrometers, in particular between 250 and 300 micrometers, is preferred.

In addition, for example, it is also possible to apply a protective layer ("top coat"), in particular as the topmost layer, which comprises e.g. can prevent moisture from entering the hygroscopic insulating layer.

For electrical contacting, e.g. by means of a template, e.g. Bronze surfaces are applied, which contact the Heizleiterschicht and attached to which electrical lines, e.g. welded, can be.

It is still a development that the at least one heating track has been applied by means of a plasma process. In particular, a use of a thermal plasma spraying is advantageous.

By means of the plasma spraying, the heating conductor layer and optionally the insulating layer can be applied to the substrate. For example, a plasma torch can be used for plasma spraying. The plasma spraying has the advantage that it is easy to carry out and allows a high accuracy of the produced layers. In addition, many materials can be plasma sprayed. The substrate hardly heats up during the coating (up to a maximum of 200 ° C.), which is likewise advantageous.

The object is also achieved by a household appliance with at least one such heater. The household appliance, for example, a small household appliance (coffee maker, toaster, kettle, etc.), a laundry treatment device (washing machine and / or dryer, etc.) or a cooking appliance (oven, hob, cooking space divider, etc.) be.

Fig.1

zeigt einen Ausschnitt aus einem Eckbereich einer Heizung für ein Haushaltsgerät gemäß einer ersten Ausführungsform;

Fig.2

zeigt einen Ausschnitt aus einem Eckbereich einer Heizung für ein Haushaltsgerät gemäß einer zweiten Ausführungsform;

Fig.3

zeigt einen Ausschnitt aus einem Eckbereich einer Heizung für ein Haushaltsgerät gemäß einer dritten Ausführungsform;

Fig.4

zeigt einen Ausschnitt aus einem Eckbereich einer Heizung für ein Haushaltsgerät gemäß einer vierten Ausführungsform;

Fig.5

zeigt einen Ausschnitt aus einem Eckbereich einer Heizung für ein Haushaltsgerät gemäß einer fünften Ausführungsform; und

Fig.6

zeigt einen Ausschnitt aus einem Eckbereich einer Heizung für ein Haushaltsgerät gemäß einer sechsten Ausführungsform.

In the following figures, the invention will be described schematically with reference to exemplary embodiments. In this case, the same or equivalent elements may be provided with the same reference numerals for clarity.

Fig.1

shows a section of a corner region of a heater for a household appliance according to a first embodiment;

Fig.2

shows a section of a corner region of a heater for a household appliance according to a second embodiment;

Figure 3

shows a section of a corner region of a heater for a household appliance according to a third embodiment;

Figure 4

shows a section of a corner region of a heater for a household appliance according to a fourth embodiment;

Figure 5

shows a section of a corner region of a heater for a household appliance according to a fifth embodiment; and

Figure 6

shows a section of a corner region of a heater for a household appliance according to a sixth embodiment.

Fig.1 shows a section of a corner region of a heater 1 for a household appliance H according to a first embodiment. On a carrier layer 2, for example, a substrate to be heated of the household appliance or an electrically insulating insulating layer, a rectangular Heizleiterschicht 3 has been applied by means of a thermal plasma spraying process. In the originally full-surface heating conductor layer 3 is a spiral extending trench 4 has been introduced, which generates a rectangular Heizleiterschicht 3 spiral-filling heating track 5. The separation trench 4 has preferably been introduced by means of a laser cutting method, for example with a width of 300 micrometers to 700 micrometers.

In order to utilize the heating conductor layer 3 as completely as possible for heat generation, the heating track 5 has a plurality of angularly curved heating track sections 6. The angularly curved Heizbahnabschnitte 6 have at their edges where the heating track 5 changes direction by 90 °, right angles corners 7. In the curved Heizbahnabschnitten 6 there is a current displacement, that is, that the current at an inner corner 7, 7a may have a higher current density than at an outer corner 7, 7b, resulting in an uneven heat distribution in the corners 7, possibly even to a heat overload on the inner corner 7a. On the other hand, at the outer corner 7b too little heat development can occur, which can be further enhanced by a width of the curved heating track sections 6, in particular from the inner corner 7a to the outer corner 7b, being greater than a width B of one subsequent rectilinear Heizbahnabschnitts 8.

In order to achieve a homogenization of the current flowing through a curved Heizbahnabschnitt 6 or its current density across the width of the curved Heizbahnabschnitte 6, has one or more, in particular all, the curved Heizbahnabschnitte 6 here three locally limited recesses 9, as here by way of example with reference to the outermost Heizbahnabschnitts 6 indicated by the dashed lines. The recesses 9 have been introduced into the heating conductor layer 3 as cuts, in particular laser cuts. The recesses 9 have the same basic shape and follow the shape of the angularly curved Heizbahnabschnitts 6 and are angled at right angles. The recesses 9 are distributed over a width of the angularly curved Heizbahnabschnitts 6 equidistant. The recesses 9 thus form four substantially equal width, parallel Heizbahnstreifen 10, each occupying a quarter of the width of the heating path 5 minus a width of the recesses 9.

The recesses 9 set with their ends in a respective associated rectilinear Heizbahnabschnitt 8, in a region in which the current over the width B is distributed substantially equal. The current is therefore also distributed over the equidistant Recesses 9 substantially uniformly distributed, so that in the angularly curved Heizbahnabschnitts 6 Although a current displacement in the individual Heizbahnstreifen 10 takes place, but the power is still distributed over the Heizbahnstreifen 10. This causes a homogenization of the current or the current density over the angularly curved Heizbahnabschnitt. 6

Fig.2 shows a section of a corner region of a heater 11 for a household appliance H according to a second embodiment. The heating track 5 has in its originally angularly curved Heizbahnabschnitten 6 each have a dashed line notch 19, which rounds a pointed outer corner 7b to a rounded outer corner 17b, while a pointed inner corner 7a remains unchanged. For this purpose, the recess 19 engages on both sides on the outer edge or parting trench 4 of the originally angularly curved Heizbahnabschnitts 6 and is formed in a sector of a circle with a constant radius R. The radius R corresponds at least approximately to a width B of a subsequent rectilinear Heizbahnabschnitts 8, so that a tendency to form zones of low current density is reduced and a homogenization of the current density is improved. Generally, the recess 19 may also have a different radius, for example a larger radius, to narrow the heating track 5 and thus to maintain a current density at a predetermined minimum level.

Figure 3 shows a section of a corner region of a heater 21 for a household appliance H according to a third embodiment. The Heizleiterschicht 3 now has a separation trench 24, which generates a heating track 25, the curved Heizbahnabschnitte rounded curved Heizbahnabschnitte 26 are. This means that the dividing trench 24 in the region of the rounded curved Heizbahnabschnitte 26 itself is rounded, which is particularly advantageous in a generation of the separation trench 24 by means of a laser cut, since the separation trench 24 generating laser beam is continuously feasible, which facilitates manufacture. For a particularly simple manufacture, the radius R of the edges of the curved Heizbahnabschnitte 26 or the associated separation trenches 24 is constant, although this is generally not mandatory. The use of the heating track 25 with the rounded curved Heizbahnabschnitten 26 improved a uniform distribution of the current density compared to a heating track with angularly curved Heizbahnabschnitten. The use of rounded corners of the rounded curved Heizbahnabschnitte 26 may constitute an independent invention.

Figure 4 shows a section of a corner region of a heater 31 for a household appliance H according to a fourth embodiment. The heater 31 is configured similarly to the heater 21 according to the third embodiment, wherein now the heating track 25 similar to the heater 1 according to the first embodiment has three dashed lines recesses 39 which correspond to the rounded basic shape of the rounded curved Heizbahnabschnitts 26, in particular a same Radius and / or can be distributed equidistantly over a width of the heating track 25, and to unify a current flow across the width of the rounded curved Heizbahnabschnitts 26 by generating, for example, four Heizbahnstreifen 40 partially.

Figure 5 shows a section of a corner region of a heater 41 for a household appliance H according to a fifth embodiment. The heating track 25 in turn has rounded curved Heizbahnabschnitte 26. In the region of the curvature or in the rounded curved Heizbahnabschnitt 26 is a recess 49 which has two circular sector-shaped curved edges 49a and 49b. The radius of the rounded curved edges 49 a, 49 b is designed so that a constant width (cross-sectional width) of the separated by the recess 49 Heizbahnstreifen 50 results. The radius is different, with the radius of the inner edge 49a being greater than the radius of the outer edge 49b. The recess thus has pointed ends expiring. The recess 49 may include or be recessed an 'island' of material of the heating layer 3. The Heizbahnstreifen 50 may have a different width, wherein the inner Heizbahnstreifen 50 may be narrower than the outer Heizbahnstreifen 50 particular.

The recess may alternatively have rounded tips or ends with a correspondingly small curvature.

Figure 6 shows a section of a corner region of a heater 51 for a household appliance H according to a sixth embodiment. The curved Heizbahnabschnitte 26 now each have a recess 59 which further rounds a curved edge, more precisely, an outer rounded corner 57b of the separation trench 24 of the Heizbahnabschnitts 26 with a radius R1. For this purpose, the recess 59 as an edge attaching recess 59 formed with a radius R2> R1. The radius R2 of the recess 59 preferably corresponds at least approximately to the original radius R1 of the curved Heizbahnabschnitts, plus a width B of the rectilinear Heizbahnabschnitts 8, so R2 = R1 + B.

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

So different and different types of recesses can also be combined.

LIST OF REFERENCE NUMBERS

1

heater

2

backing

3

heat conductor

4

separating trench

5

heating track

6

angularly curved Heizbahnabschnitt

7

corner

7a

inner corner

7b

outer corner

8th

rectilinear Heizbahnabschnitt

9

recess

10

Heizbahnstreifen

11

heater

12

rounded curved Heizbahnabschnitt

17b

rounded outer corner

19

recess

21

heater

24

separating trench

25

heating track

26

rounded curved Heizbahnabschnitt

31

heater

39

recess

40

Heizbahnstreifen

41

heater

49

recess

49a

inner edge

49b

outer edge

50

Heizbahnstreifen

51

heater

57b

rounded outer corner

59

recess

B

Width of the rectilinear Heizbahnabschnitts

R

radius

R1

radius

R2

radius

H

household appliance

Claims (7)

1. Heater (1; 11; 21; 31; 41; 51) for domestic appliances (H),

   - having at least one heating track (5; 25) with at least one rounded, curved heating track section (6; 26),

   - which heating track (5; 25) has at least one locally delimited recess (9; 19; 39; 49; 59) in the region of the curved heating track section (6; 26),

   - the recess (49) has two rounded, curved edges (49a, 49b), wherein

   - the two rounded, curved edges (49a, 49b) of the recess (49) have such a respective radius that a respectively curved edge (49a; 49b) of the recess (49) and an edge (24) of the rounded, curved heating track section (26) which faces the latter delimits a heating track strip (50) of a constant width,

   - wherein the radii of the edges (49a, 49b) of the recess (49) are different,
   characterised in that

   - the radius of the inner edge (49a) of the edges (49a, 49b) of the recess (49) is greater than the radius of the outer edge (49b) of the recess (49).
2. Heater (1; 31) according to claim 1, characterised in that the curved heating track section (6; 26) has at least one recess (9; 39) which follows the shape of the curved heating track section (6; 26).
3. Heater (1; 31) according to one of the preceding claims, characterised in that the curved heating track section (6; 26) has a number of recesses (9; 39), which are arranged at least partially in parallel across a width (B) of the heating track section (6; 26), so that they form heating track strips (10; 40) which run partially in parallel and have essentially the same partial resistances.
4. Heater (1; 31) according to one of claims 2 or 3, characterised in that the curved heating track section (6; 26) has a number of recesses (9; 39) of the same basic form, which are arranged equidistantly across a width (B) of the heating track section (6; 26).
5. Heater (1; 11; 51) according to one of the preceding claims, characterised in that the curved heating track section (6; 26) has a recess (19; 59) which rounds a curved edge (7b; 57b) of the heating track section (6; 26), in particular a recess (19; 59) joining at the edge with a constant radius (R2).
6. Heater (51) according to claim 5, characterised in that the radius (R2) of the recess (59) corresponds at least approximately to an original radius (R1) of the curved heating track section (26) plus a width (B) of an adjoining straight heating track section (8).
7. Heater (1; 11; 21; 31; 41; 51) according to one of the preceding claims, characterised in that the heating track (5; 25) fills a rectangular surface.

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