A COOKING ASSEMBLY

Abstract

A cooking assembly comprising a countertop (6) and an induction cooking device (1) attached to the bottom (8) of the countertop (6). The induction cooking device comprises: an induction coil formed from a wire having a substantially uniform non-circular cross-section which is higher than it is wide and which is at a distance (d.sub.6) from a top surface (7) of the countertop between 10 and 50 mm, said induction coil having an outer diameter and an inner diameter which is at least equal to 40% of said outer diameter; a generator (15, 16) configured to supply an AC current to the induction coil with a frequency between 30 and 80 kHz; and a magnetic flux concentrator disposed underneath the induction coil and covering at least 50% of the bottom of the induction coil and having a relative magnetic permeability of at least 1000.

Claims

1. A cooking assembly comprising a countertop and an induction cooking device to be mounted underneath the countertop, the induction cooking device comprising: a frame; an induction coil supported by the frame and having a bottom and a top, the top being oriented towards the countertop and being positioned at a first distance from a top surface of the countertop, the first distance being between 10 and 50 mm, the induction coil being formed from a wire having a substantially uniform non-circular cross-section having a width and a height, the height being larger than the width, said induction coil having an inner diameter and an outer diameter, said inner diameter being at least equal to 40% of said outer diameter; a generator connected to the induction coil and configured to supply an AC current to the induction coil, the AC current having a frequency between 25 and 80 kHz; and a magnetic flux concentrator disposed between the frame and the bottom of the induction coil, the magnetic flux concentrator covering at least 50% of the bottom of the induction coil and having a relative magnetic permeability of at least 1000.

2. The cooking assembly according to claim 1, wherein said inner diameter is at most equal to 75%, particularly at most 60%, and more particularly at most 50%, of said outer diameter.

3. The cooking assembly according to claim 1, wherein the magnetic flux concentrator covers at least 70%, particularly at least 80%, and more particularly at least 90%, of the bottom of the induction coil, the magnetic flux concentrator preferably covering substantially the entire bottom of the induction coil.

4. The cooking assembly according to claim 1, wherein the magnetic flux concentrator has a relative magnetic permeability of at least 1600, particularly at least 2100, more particularly at least 2400, and most particularly at least 2600.

5. The cooking assembly according to claim 1, wherein the magnetic flux concentrator is formed by: a substantially flat disc which is preferably formed from a plurality of circle sectors; or a substantially flat annulus which is preferably formed from a plurality of annulus sectors, wherein, preferably, an inner diameter of said annulus is at most equal to the inner diameter of the induction coil and an outer diameter of said annulus is at least equal to the outer diameter of the induction coil, and wherein, more preferably, the inner diameter of said annulus is at least equal to 10% in particular at least 25%, more in particular at least 40%, and most in particular at least 60%, of the inner diameter of the induction coil, and is at most equal to 90%, in particular at most 80%, more in particular at most 75%, and most in particular at most 70%, of the inner diameter of the induction coil.

6. The cooking assembly according to claim 1, wherein the magnetic flux concentrator comprises a soft magnetic material, preferably a ferrite.

7. The cooking assembly according to claim 1, wherein the AC current has a frequency of at most 60 kHz and particularly at most 50 kHz and/or at least 30 kHz.

8. The cooking assembly according to claim 1, wherein the induction cooking device further comprises an insulating sheet disposed on top of the induction coil and/or a further insulating sheet disposed on the bottom of the induction coil, wherein, preferably, the insulating sheet and/or the further insulating sheet substantially covers the induction coil and more preferably also covers the magnetic flux concentrator, wherein, preferably, the insulating sheet and/or the further insulating sheet comprises mica.

9. The cooking assembly according to claim 1, wherein the first distance is at least 12 mm, in particular at least 16 mm, and more in particular at least 18 mm, and/or wherein the first distance is at most 40 mm, in particular at most 30 mm, more in particular at most 25 mm, and most in particular at most 22 mm.

10. The cooking assembly according to claim 1, wherein the countertop has a nearly constant thickness and/or wherein the countertop comprises a heat resistant material, such as porcelain, ceramic, glass, or a sintered material.

11. The cooking assembly according to claim 1, wherein the induction cooking device further comprises a temperature sensing system configured to sense a temperature of a cooking pot positioned on the countertop, the temperature sensing system comprising: an opening extending through the countertop; a support having a proximal end and a distal end and extending through said opening, the distal end being near a top surface of the countertop; and a temperature sensor positioned near the distal end of the support.

12. The cooking assembly according to claim 11, wherein the proximal end is supported by the frame or wherein the proximal end is connected to the bottom surface of the countertop or wherein the support is glued, screwed and/or press fitted into the opening.

13. The cooking assembly according to claim 11, wherein the temperature sensing system further comprises a cover disposed on the distal end of the support and covering the temperature sensor, wherein, preferably, the cover at least partly protrudes with respect to the top surface of the countertop.

14. The cooking assembly according to claim 13, wherein a distance between the top of the induction coil and the distal end of the support is substantially the same as said first distance.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0056] The invention will be further explained by means of the following description and the appended figures.

[0057] FIG. 1 shows a perspective view of an induction cooking device used in a cooking assembly according to the present invention.

[0058] FIG. 2a shows a longitudinal cross-section through a cooking assembly according to the present invention.

[0059] FIG. 2b shows a detail of FIG. 2a.

[0060] FIG. 3 shows a perspective view of the bottom of the inductor in the induction cooking device used in a cooking assembly according to the present invention.

DESCRIPTION OF THE INVENTION

[0061] The present invention will be described with respect to particular embodiments and with reference to certain drawings but the invention is not limited thereto but only by the claims. The drawings described are only schematic and are non-limiting. In the drawings, the size of some of the elements may be exaggerated and not drawn on scale for illustrative purposes. The dimensions and the relative dimensions do not necessarily correspond to actual reductions to practice of the invention.

[0062] Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. The terms are interchangeable under appropriate circumstances and the embodiments of the invention can operate in other sequences than described or illustrated herein.

[0063] Moreover, the terms top, bottom, over, under and the like in the description and the claims are used for descriptive purposes. The terms so used are interchangeable under appropriate circumstances and the embodiments of the invention described herein can operate in other orientations than described or illustrated herein.

[0064] Furthermore, the various embodiments, although referred to as preferred are to be construed as exemplary manners in which the invention may be implemented rather than as limiting the scope of the invention.

[0065] FIG. 1 shows a perspective view of an induction cooking device 1 used in a cooking assembly according to the present invention. The induction cooking device 1 is meant to be attached to the underside of a countertop 6 and is therefore open at its top side. The remaining sides of the induction cooking device 1 are enclosed by a housing 2 in order to protect the components within. Typically, the housing 2 will be attached to the underside of the countertop 6. Within the housing 2, a frame 3 is provided on which the inductor 4 and the temperature sensing system 5 are mounted. The details of both the inductor 4 and the temperature sensing system 5 will be described with reference to FIGS. 2 and 3.

[0066] FIG. 2a shows a longitudinal cross-section through a cooking assembly 10 according to the present invention, which assembly comprises a countertop 6 having a top surface 7 and a bottom surface 8 and two through-openings 9 the purpose of which is described below. The cooking assembly 10 further comprises an induction cooking device 1 mounted against the bottom surface 8 of the countertop 6. The induction cooking device 1 is designed in order to supply heating energy to a cooking pot (not shown) to be placed directly on the top surface 7 of the countertop 6.

[0067] The countertop 6 is made from a heat resistant material, such as porcelain, ceramic, glass, or a sintered material, such as sintered stone. As used herein, a heat resistant material should be able to withstand a contact temperature (i.e. be in contact with a cooking pot having a temperature) of at least 230 C., preferably at least 240 C., more preferably at least 260 C. and most preferably at least 300 C. This ensures that the countertop can withstand the temperatures typically achieved in common cooking application. This typically excludes composite materials as the resins used therein are unable to withstand temperatures exceeding 180 C. Preferably, the countertop comprises a ceramic material or a sintered material, such as sintered stone.

[0068] The countertop 6 has a substantially constant thickness d.sub.5, which may be in the order of 10 to 50 mm and is about 20 mm in the illustrated embodiment. In particular, the bottom surface 8 of the countertop 6 is not provided with any recesses or other local thickness variations that would allow to position the inductor 4 closer to the top surface 7 of the countertop 6.

[0069] As described above, within the housing 2 of the induction cooking device 1, a frame 3 is provided. This frame 3 is positioned with respect to the housing 2 through the use of various feet 11. In the illustrated embodiment, the frame 3 is formed by a substantially flat plate and forms a division wall between the inductor 4 and the temperature sensing system 5 on the one hand and the various electronical components of the induction cooking device 1 on the other hand. The frame 3 is manufactured from a metal, preferably aluminium. This offers the required rigidity and strength and has a sufficiently low magnetic permeability so as to not significantly affect the operation of the inductor 4.

[0070] As shown in FIG. 2a, the inductor 4 comprises an induction coil 12 with a magnetic flux concentrator 13 underneath and an insulation layer 14 on top. Likewise, an insulation layer is also shown between the induction coil and the magnetic flux concentrator 13. A generator is connected to the induction coil 12 in order to deliver the required AC current. In the illustrated embodiment, the generator comprises a net filter 16 and an electronic steering module 15 which controls the operation of the inductor 4. The generator provides an AC current to the induction coil 12 having a frequency between 25 and 80 kHz and preferably not exceeding 60 kHz and particularly 50 kHz with the frequency preferably exceeding 30 kHz.

[0071] The induction coil 12 is made from a copper-clad aluminium wire, but other materials are possible (such as pure aluminium). The induction coil 12 has an inner diameter d.sub.2 and an outer diameter d.sub.3. In the illustrated embodiment, the inner diameter d.sub.2 is about 90 mm and the outer diameter d.sub.3 is about 200 mm, but these values may vary. In general, the inner diameter d.sub.2 is at least equal to 40% and is at most equal to 75%, in particular at most 60%, and more in particular at most 50%, of the outer diameter d.sub.3. As described above, this provides a good balance between the number of windings and the desired magnetic field strength. The wire is a Litz wire with a non-circular cross-section, in particular a rectangular cross-section, such that adjacent wires can be placed as close to one another as possible. It is beneficial in case the Litz wire is higher than it is wide, but the aspect ratio (e.g. the height to width ratio) may vary in general between 1 and 5, preferably between 1.1 and 4, more preferably between 1.2 and 3, even more preferably between 1.3 and 2, and most preferably between 1.4 and 1.6.

[0072] In the illustrated embodiment, the magnetic flux concentrator 13 covers the whole bottom of the induction coil 12 together with a surrounding area and is best illustrated in FIG. 3. FIG. 3 shows that the magnetic flux concentrator 13 is constructed from multiple (in particular 8) annulus sectors 13a, 13b, . . . such that the magnetic flux concentrator 13 has an annular shape. The annulus has an inner diameter d.sub.1 and an outer diameter d.sub.4. In the illustrated embodiment, the inner diameter d.sub.1 is about 60 mm and the outer diameter d.sub.4 is about 210 mm, but these values may vary. In general, the inner diameter d.sub.1 is at least equal to 10%, in particular at least 25%, more in particular at least 40%, and most in particular at least 60%, and is at most equal to 90%, in particular at most 80%, more in particular at most 75%, and most in particular at most 70%, of the inner diameter d.sub.2 of the induction coil 12. As described above, completely covering (or at least covering 70%, preferably 80%, and more preferably 90% of the bottom area of) the induction coil 12 and the adjacent area improves the effect of the magnetic flux concentrator 13 by directing more of the generated magnetic field towards the top surface 7 of the countertop 6.

[0073] In an alternative embodiment, the magnetic flux concentrator 13 is formed by a disc. This further improves the effect of the magnetic flux concentrator 13 since the inner coil area is now wholly covered. However, it requires a different temperature sensing system 5 since there is no longer an opening through the magnetic flux concentrator 13 to the frame 3. The temperature sensor support 19 may then be glued to the bottom 8 of the countertop 6 or press-fitted or screwed into the opening 9. Naturally other shapes are available to form the magnetic flux concentrator 13, such as a rectangular shape, an oval shape, etc. The specific construction is in part determined by the costs of manufacturing the ferrite elements, in particular in order to avoid a grinding operation.

[0074] It will be readily appreciated that the magnetic flux concentrator 13 may also protrude outwards with respect to the coil 12. More specifically, the outer diameter d.sub.4 of the magnetic flux concentrator 13 may be at least equal to, preferably larger than, more preferably at least 5% larger than and even more preferably at least 10% larger than the outer diameter d.sub.3 of the coil 12.

[0075] Various materials are known from which to form the magnetic flux concentrator 13. Soft magnetic materials, preferably a ferrite is used, such as a manganese zinc ferrite.

[0076] The insulation sheets are made from mica in the illustrated embodiment and covers both the induction coil 12 and the magnetic flux concentrator 13 in order to electrically insulate and/or to protect the live parts of the induction cooking device from a safety point of view and/or to provide a thermal protection. Depending on the countertop 6, it will be readily appreciated that other materials may be used to form the insulation sheet 14 or that the insulation sheet 14 may be absent. Moreover, varying thicknesses may be used, e.g. between 0.4 to 2 mm.

[0077] Additionally, a ventilation unit 17 is provided within the housing 2 in order to cool the interior thereof. There is also provided a control unit 18 that may be used to coordinate between multiple induction cooking devices 1. The control unit 18 may also be used to handle user input/output.

[0078] In the illustrated embodiment, the induction cooking device 1 included two inductors 4. It will be readily appreciated that fewer or more inductors 4 may be provided per induction cooking device 1.

[0079] As described above, due to the frequency of the AC current, the non-circular cross-section of the induction coil wire, and the magnetic flux concentrator 13 covering at least 50% of the induction coil 12, the induction cooking device 1 according to the present invention is operable to efficiently provide energy to a cooking pot (not shown) with an air gap d.sub.6 spanning between 10 and 50 mm, in particular at least 12 mm, more in particular at least 16 mm, and most in particular at least 18 mm and/or in particular at most 40 mm, more in particular at most 30 mm, even more in particular at most 25 mm, and most in particular at most 22 mm. It will be readily appreciated that the term air gap refers to the distance between the induction coil 12 (in particular the top thereof) and the cooking surface 7 and does not require actual air to be present between these elements. This is also illustrated in FIGS. 2a and 2b where the air gap is actually filled by a mica layer 14 and a countertop 6.

[0080] The temperature sensing system 5 is also illustrated in FIG. 2b and comprises a support 19 which extends through the opening 9 in the countertop 6. The support 19, in particular at is lower end, is fastened to the frame 3, while the upper end of the support 19 is located near the top surface 7 of the countertop 6. Within the support 19, preferably as near to the top surface 7 of the countertop 6 as possible, there is provided a temperature sensor 20 which is connected by a wire 21 to a processor (not shown) which processes the temperature sensor measurements in order to determine the cooking pot temperature. On top of the temperature sensor 20, there is provided a protective cover 22 which, in the illustrated embodiment is flush with the top surface 7 of the countertop 6. In the illustrated embodiment, the cover 22 is formed by a 1 mm thick stainless steel sheet, but other materials and/or thicknesses are available (e.g. aluminium, alum iniumnitride, magnesiumoxide, heat resistant plastic materials, etc.). Ideally, the cover 22 is made from a thermally conducting material in order to minimize any temperature variations between the cooking pot and the cover 22. Moreover, the cover 22 is preferably made from an electrically non-conductive material in order to avoid generation of eddy currents in the cover as this may heat the cover and influence the temperature reading.

[0081] Between the temperature sensor 20 and the support 19, there is a resilient element 23 (e.g. a silicone ring or a foam material). The main advantage thereof, as described above, is to allow the cover 22 and/or the temperature sensor 20 to protrude slightly with respect to the top surface 7 of the countertop 6 which allows to compensate for cooking pots having a non-flat bottom surface and/or allows determination of cooking pot weight when a weight sensor is present. Alternatively, when the protective cover 22 is fixed in the countertop (e.g. glued flush with the countertop top surface), the resilient element 23 ensures that the temperature sensor 20 is making a good thermal contact with the protective cover 22. In a non-illustrated embodiment, the resilient element (e.g. a compression spring) is positioned between the support 19 and the frame 3. As described above, such an embodiment is less prone to manufacturing tolerances when compared to a foam or silicone ring resilient element.

[0082] Although aspects of the present disclosure have been described with respect to specific embodiments, it will be readily appreciated that these aspects may be implemented in other forms within the scope of the invention as defined by the claims.