WO2013049946A1 - Induction-compatible cookware with a low noise level and increased emc - Google Patents

Abstract

The invention relates to novel, induction-compatible cookware which, when used, emits very limited noise and radiation due to a special base design. Such a base design allows EMC to be increased and allows the noise level to be minimized or eliminated completely. From a functional viewpoint, the claimed cookware design differs from the conventional design having a so-called sandwich base in that inductive heat is produced in a second ferromagnetic base disc (4) or in the metal insert (6) rather than in the disc near the coil, namely the austenitic cookware capsule (5). The magnetic "invisibility" of the austenitic high-grade steel, which the cookware capsule (5) is made of, allows the second base disc (4) or the metal insert (6) to be magnetized.

Description

 Construction of an induction-capable cookware

 with low noise level and

 high EMC

State of the art

Most cookware is today produced by thermoforming processes. This process is simply the industry process. Other forming processes (ironing, aluminum alloys, etc.) are present, but not of great importance, and are considered secondary here. So, if we speak here of a manufacturing process, then this means exclusively the thermoforming process.

In order to produce an induction-suitable tableware, at least its bottom part must be made of a magnetizable material. Best of a ferromagnetic. A marketable, induction-suitable cookware is available today in various designs. The simplest form is in a dish made of cast iron. An enamelled tableware is also an induction-suitable cookware, since it consists of a enamel-capable, ferritic steel. The mentioned cookware has been on the market for many decades and in less developed countries, it will dominate it for a long time, as it is quite cheap. In recent years, other materials appear that are suitable for the construction of an induction-suitable cookware. So z. For example, Silit offers cookware made of sintered material, which consists of steel and high-tech ceramics (e30: known by the commercial name Silagran). However, the most common induction cooking utensils from ferritic stainless steel floor, and is almost exclusively from the material no. Built in 1.4016. Recently, other ferritic stainless steels such as the nickel-free stainless steels of the 1.452x and 1.4621 groups are appearing. ArcelorMittal, the world's largest supplier of stainless steel, markets such stainless steels under the commercial name of KA A. A promising development by the same company is the new soft magnetic nickel-iron-chromium alloy with the commercial name Phytherm. This has a low currie temperature, which guarantees safety against overheating of the cookware.

It should be noted that the ferromagnetic material, which is integrated into the dish bottom, is to be positioned first, ie closest to the induction source (coil). If this is not done, then you must ensure that the material of the harness capsule consists of a material that has a non-shielding effect. Otherwise, the ferritic

CONFIRMATION COPY Material in the dish floor can not be made magnetizable, that is, no heat can be induced as shielded.

In the Swiss patent application CH 01504/11 a solution is proposed which is similar only in the physical sense of the presented solution, namely in the part concerning the position of the ferritic material. Other design features in this application are different from the o. G. Swiss registration.

The conventional cookware is today produced with a widespread technology, namely by deep-drawing a relatively thin steel sheet (thickness of 1 mm!). This technology is quite cost-effective and the industry will continue to favor it so that no significant technology change is expected.

Description of the invention

general part

The present invention differs from the o. E. Swiss registration essentially by two points. The first difference concerns the construction of the dish floor. The Swiss application provides for a multipart tableware, the present solution is not. The second difference is the properties of the two solutions. The o. G. Swiss registration is characterized by a flat, deformation-free table-top. This is not the case in the solution disclosed here. However, the common characteristic lies in the functional design of the dish floor. In both solutions, the inductively generated heat is generated in the ferritic part, which is not the first to the heat source, so the coil is positioned. The part closest to the coil is the non-magnetizable bottom capsule.

Technical part (functional description)

Of course, in addition to the induction capability, the cookware according to the invention is also suitable for all-round cooking. It has a dish floor, which does not differ significantly from the conventional dish floors in the constructive sense, s. Fig. 1. Conventionally produced cookware is characterized by a compensation bottom in which between the bottom capsule (3) made of a ferritic stainless steel and the most austenitic tableware hull (1) an insert (2) made of aluminum is integrated. The inductive heat is generated in the ferritic soil capsule (3). The insert (2) takes over the functions such as the better temperature distribution and lower ground movement. In the connection of the bottom capsule (3) with the utensil hull (1) by the so-called "beating" the insert (2) serves as a link between the two parts heated all parts to be connected to about 450 ° C and then connected together by the impact of a screw press.

Conclusion: the inductive heat generation occurs in the ferritic soil capsule (3), which is positioned as the first, ie the coil nearest. This is the most important feature of today's induction cookware.

Version: multi-part bottom

The presented invention in the version multi-part bottom, sees a harness bottom with at least two bottom discs, resp. Slice materials, in front. The schematic diagram shows the construction of the new cookware, s. Fig. 2. The first bottom plate is the insert (2) made of aluminum. It takes on the task to minimize the soil deformations, resp. to prevent them. The second bottom plate (4) provides for inductive heat generation, for a significant increase in EMC (EMC = electromagnetic compatibility), resp. the reduction of the electromagnetic stray field and the reduction of the noise level, which lies even below the audible perception of the audible. An additional electromagnetic shield is not required because the insert (2) is made of aluminum and shields itself enough. For inductive heat to be generated in the second bottom plate (4), it must be made of a magnetizable material. Preferably, soft magnetic materials such as pure iron, Fe-Ni alloys, Fe-Si alloys, etc. are used. In particular, if the harness is to produce very little, even better no noise, a material with low magnetostriction is to be selected. For example, pure iron or Fe-Si alloy with a Si content of 6.5%, Fe-Ni alloys with a Ni content of about 35% (Invar), etc. The materials mentioned have a noise level, which is much lower is considered to be the same of a ferritic stainless steel, e.g. B. 1.4016. In addition, they are sufficiently effective as electromagnetic shielding. The soil capsule (5) in the solution according to the invention is made of a non-magnetic material, preferably austenitic stainless steel. It may also be made of a non-magnetic material, however, always pay attention to the thickness of this material in order not to lose the magnetizability of the ferritic bottom disc (4).

Basically, you could get along without a bottom capsule (5). In such a case, one must ensure that the other criteria of the material such as corrosion resistance, dishwasher strength, etc. of the second bottom disc (4) are met. This could be done by the surface coating.

Version: one-piece bottom

The presented invention in the version one-piece bottom, sees a harness bottom with only one bottom plate, respectively. Slice material in front. The schematic representation shows the construction of the new cookware, s. Fig. 3. The bottom plate is a metallic insert (6). On the one hand, it assumes the task of minimizing the soil deformations, resp. to prevent them and on the other hand to generate the inductive heat. It ensures a significant increase in EMC (EMC = electromagnetic compatibility) resp. the reduction of the electromagnetic stray field and the reduction of the noise level, which lies even below the audible perception of the audible. An additional electromagnetic shielding is not required since the insert (6) is made of a ferromagnetic material and shields or absorbs itself enough. So that in the insert (6) inductively generated heat can arise, it must therefore be made of a magnetizable material. Preferably, soft magnetic materials such as pure iron, Fe-Ni alloys, Fe-Si alloys, etc. are used. In particular, if the harness is to produce very little, even better no noise, a material with low magnetostriction is to be selected. For example, pure iron or Fe-Si alloy with an Si content of 6.5%, Fe-Ni alloys z. B. with a Ni content of 75-82%, etc. The materials mentioned have a noise level, which is substantially lower than that of a ferritic stainless steel, z. B. 1.4016. In addition, they are sufficiently effective as electromagnetic shielding. The soil capsule

^■ (5) in the solution according to the invention is made of a non-magnetic material, preferably austenitic stainless steel. It may also be made of a non-magnetic material, but always pay attention to the thickness of this material so as not to lose the magnetizability of the metallic insert (6). Basically, you could get along without a bottom capsule (5). In such a case, care must be taken that the other criteria of the material such as corrosion resistance, dishwasher resistance, etc. of the metallic insert (6) are met. This could be done by the surface coating.

Conclusion: The advantages of this constructive arrangement are therefore both in a more intense heat generation as well as in the minimization of the noise level and increasing the EMC. Compared to today's induction-capable cookware - except for the above-mentioned patent applications - the characteristics such as inductively generated heat, noise level and scattered radiation have much better, positive values than all current dishes. Due to the known material properties of the ferromagnetic material as a function of temperature, it is possible to achieve a good temperature control of the cooking material.

Technical part Version: multi-part bottom

The insert (2), ie the so-called "thermo-mechanical disk", is considerably thicker than the second bottom disk (4) and is made of a good heat-conducting material such as aluminum between 3-8 mm, this range also includes today's compensation floors, with the tendency that the material is thicker, the lower its thickness may be.When using aluminum alloys other than the material for the insert (2) Of course you can also use copper and / or other copper alloys as the material for the insert (2) .Of a little higher price, nothing speaks against this Proposal: Copper and in particular its alloys have both very good mechanical (strength) and thermal (thermal conductivity) properties.

The second bottom disc (4), the so-called "heat disc" is a somewhat thinner disc and its thickness is preferably in the range of a few tenths of a millimeter to a millimeter., In one case or another, depending on the size of the cookware, The primary task of the second bottom disc (4) is to generate the induction heat, making it clear that it must be made of a good magnetizable material. "Conventional cookware uses almost exclusively the ferritic for inductive heat generation Noble- steel, preferably stainless steel 1.4016. The noise level of this material is very high and is so annoying that it can be very uncomfortable. And that's exactly what many customers are not sure about when it comes to EMC. The ferritic Nobelsathl 1.4016, as well as the other ferritic stainless steels, in addition to the task of generating heat, also have to provide a number of other functions, eg. As the mechanical stability (to prevent shock dents, therefore somewhat thicker than is necessary for the heat indexing), compatibility with the food, dishwasher fitness, corrosion resistance, etc. From this point of view, the ferritic stainless steel has been chosen because he , just had to meet a variety of boundary conditions. If it had only been chosen according to the criterion "magnetizability, noise level and EMC", these stainless steels would certainly not have been chosen, their permeability is very low, the magnetostriction very high (high noise level!) And the EMC low.

Conclusion: in conventional dishes, the bottom capsule (3) is responsible for both the inductive heat generation, as well as for a number of other functional tasks. In the presented invention, according to this version, the double function of the bottom capsule (3) is separated. The inductive heat generation takes place in a separate, second bottom disk (4). For the other objects mentioned above, a bottom capsule (5), but made of a non-ferromagnetic material, is used. Preferably austenitic stainless steel such as 1.4301 and others.

Version: one-piece bottom

The insert (6), which is the so-called "universal disk", is much thicker than the harness body (1) and is made of a material that is a good heat conductor, such as pure iron 3-5 mm This area also contains today's compensation floors, with the tendency that the thicker the material, the smaller its thickness may be.The metallic insert (6) provides the thermo-indexed forces the greatest resistance and prevents or minimizes the Due to the very high thermal conductivity of the pure iron, about 70 W / mK, the insert (6) ensures a good heat distribution in the bottom of the dish The primary task of the metallic insert (6), however, is to generate the induction heat in that it must be made of a readily magnetizable material, preferably of pure iron The effectiveness of the pure iron in terms of its electromagnetic properties is already in the Versi previously described. Also in this version, the bottom capsule (5) consists of a non-ferromagnetic material. Preferably austenitic stainless steel such as 1.4301 and others.

Conclusion: In the case of conventional dishes, the bottom capsule (3) is responsible for both inductive heat generation and a number of other functionally related tasks. In the presented invention, according to this version, the dual function of the bottom capsule (3) is separated. The inductive heat generation takes place in the metallic insert (6). The bottom capsule (5) is made of a non-ferromagnetic material and as in the previous version, preferably austenitic stainless steel such as 1.4301 and others.

The high noise level of z. B. ferritic stainless steel 1.4016, which is now integrated in most dish floors, can be eliminated by other soft magnetic materials. Some of the materials in question are pure iron, iron-silicon alloys and many other soft magnetic materials based on nickel-chromium and cobalt-containing iron alloys, s. the list of soft magnetic materials available from VAC / Hanau, FEFE Corp., ArcelorMittal (Phytherm) and the like. But not all soft magnetic materials are optimally suitable as material for inductive heat generation. Preference is given to those soft magnetic materials which have first a low electrical resistivity, then a high permeability, high losses (ie high heat generation!) And a lower magnetostriction and of course are not so very expensive. To the hum or resp. reduce the noise resp. JFE Steel Corp. offers the opportunity to eliminate Iron-silicon alloys with a silicon content of 6.5% (see corresponding product catalog). Very low magnetostriction has an annealed pure iron, an iron-nickel alloy with 75-82% Ni content (see Magnifer 75, 7904 and 8105 from ThyssenKrupp VDM). All mentioned soft magnetic materials, except pure iron, are very expensive and their kilo price is more than 40 euros. Compared to the pure iron price of 3-4 € / kg they are too expensive.

The elimination of humming and / or noise is a very important matter for the induction field manufacturers, as it has a very promotional effect and is associated with much fewer customer complaints

The inventor assumes that the cookware according to the invention in the version of multi-part bottom can be produced quite inexpensively, if it preferably consists of the following materials: Utensils (1) made of austenitic stainless steel (1.4301) or austenitic stainless steel plated with various materials, thickness greater than 0.5 mm, insert (2) of aluminum, thickness greater than 4 mm,

 Bottom capsule (5) made of austenitic stainless steel (1.4301),

 Second bottom disc (4), the so-called "heat disc" made of pure iron, thickness greater than 0.1 mm and smaller than 1.0 mm, and in the version one-piece bottom, preferably made of:

Dishware (1) austenitic stainless steel (1.4301) or austenitic stainless steel plated with various materials, thickness greater than 0.5 mm,

 Insert (6) made of pure iron, thickness greater than 2 mm and less than 5 mm,

 Bottom capsule (5) made of austenitic stainless steel (1.4301).

The above numerical values are guideline values resp. Optimum values and can be changed accordingly, but are largely for the used in the normal household cookware. For the dishes in the catering kitchens tend to be higher values, since this harness is much larger than the same in a home kitchen.

drawings

Fig.l .: Schematic representation of the structural design of a conventional cookware

2: Schematic representation of the structural design of an induction-capable cookware with low noise level and high EMC, version: multi-part bottom

Fig. 3: Schematic representation of the structural design of an induction-capable cookware with low noise level and high EMC, version: one-piece bottom

Claims

claims 1. The induction-suitable cookware according to the invention with low noise level and high EMC, realized by a crockery hull (1) with a two-layer bottom, characterized in that this from a soft magnetic bottom disc (4) in which the inductive heat is generated, and a bottom capsule (5) positioned between the bottom disc (4) and the magnetic coil. 2. The inductive housing according to the invention with low noise level and high EMC, realized by a crockery hull (1) with a single-layered floor, characterized in that this from a soft magnetic insert (6), in which the inductive heat is generated, and a Bottom capsule (5), which is positioned between the insert (6) and the magnetic coil consists. 3. The induction-suitable cookware according to the invention with low noise level and high EMC, according to claims 1 and 2, characterized in that the crockery hull (1) austenitic stainless steel, preferably from 1.4301, but also from a plated with different material stainless steel. 4. The invention induction-suitable cookware with low noise level and high EMC, according to claims 1 and 2, characterized in that the crockery hull (1) consists of a different materials, 5. The invention induction-suitable cookware with low noise level and high EMC, according to claims 1 and 2, characterized in that the crockery hull (1) consists of aluminum. 6. The invention induction-suitable cookware with low noise level and high EMC, according to claims 1 and 3, characterized in that the second bottom plate (4) made of a soft magnetic material, preferably made of pure iron. 7. The invention induction-suitable cookware with low noise level and high EMC, according to claim 2, characterized in that the metallic insert (6) made of a soft magnetic material, preferably made of pure iron. 8. The invention induction-suitable cookware with low noise level and high EMC, according to claims 1-7, characterized in that the second bottom plate (4) made of a soft magnetic material such as iron-silicon alloy with Si content of 6.5% , an iron-nickel alloy having a Ni content of 75-82%, and an iron-cobalt-chromium alloy. 9. The invention induction-suitable cookware with low noise level and high EMC, according to claims 1-8, characterized in that the bottom capsule (5) consists of a non-magnetic material, preferably austenitic stainless steel 1.4301. 10. The inventive low induction induction cookware with high EMC, according to claims 1-9, characterized in that the bottom capsule (5) consists of a non-magnetic materials such as aluminum, copper and their alloys, assuming that their thickness the magnetizability of the second bottom disc (4) resp. the metallic insert (6) is not affected.