EP3939385A1

EP3939385A1 - An induction heated kettle

Info

Publication number: EP3939385A1
Application number: EP20715271.1A
Authority: EP
Inventors: Søren Hansen; Jesper LARFORT
Original assignee: Norqi Aps
Current assignee: Norqi Aps
Priority date: 2019-03-12
Filing date: 2020-03-12
Publication date: 2022-01-19
Also published as: DK180268B1; WO2020182262A1; DK201900312A1

Abstract

An induction heated kettle (10) comprising a bowl (20) having a bottom (23) comprising a material suitable for being heated by generate eddy currents generated by an electromagnetic field is disclosed. The kettle (10) comprises one or more induction coils (33) arranged to generate one or more electromagnetic fields that generate eddy currents in the bottom (23) of the bowl (20). The bowl (20) and the one or more induction coils (33) are integrated in the induction heated kettle (10) and that at least one temperature sensor (35, 74) is arranged to measure a temperature of the bowl (20).

Description

An Induction Heated Kettle

Field of invention

This invention relates to an induction heated kettle.

Prior art

Prior art kettles have the disadvantages that they are made of many parts, both mechanical and parts for making pressure, and they need a surrounding jacket, are heavy, complicated to install, maintain and use and they are not very good to keep a constant temperature when making food.

Moreover, prior art kettles use too much power and have a great deal of heat losses to the surroundings.

Accordingly, it is an object of the present invention to provide a kettle that comprises fewer mechanical parts, that requires no jacket, that has a reduced weight, that is easy to install, that requires less or no maintenance, that requires no pressured part, and that is simple to use for the user and easy and fast to control in order to maintain a constant temperature when making food.

Furthermore, it is an object of the invention to provide a kettle that consumes less power and by which the heat losses to the surroundings can be reduced.

EP453634A2 discloses a domestic cooking system including a base defining one or more cooking locations, electromagnetic induction apparatus for heating a food at the cooking location and apparatus for automatic stirring of the food at the cooking location. The cooking system, however, comprises a separate heating unit and separate cooking utensils. Accordingly, the heating unit cannot be controlling on the basis of the temperature of the cooking utensils. US2007000915A1 discloses a multiple layer clad article of cookware has an upper rim wherein the inner and outer layers of the cladding, generally stainless steel, are joined together by a weld that covers and protects the one or more inner layers. The inner layers are alternatively at least one of copper and aluminium, or combinations of the same.

None of these prior solutions makes it possible to provide an accurate control of the temperature of the food being cooked. Accordingly, it is an object of the present invention to provide an induction heated kettle that enables a more accurate temperature control of the food being cooked.

The objects of the present invention can be achieved by an induction heated kettle as defined in claim 1. Preferred embodiments are defined in the dependent subclaims, explained in the following description and illustrated in the accompanying drawings. Described below are specific embodiments of that which the inventor considers at present to be the best mode of fabrication, assembly and operation for carrying out the invention. These are necessarily narrow embodiments, and cover only a few of the many possible ways to practice the invention. Therefore, it is to be understood that the invention itself is actually much broader in scope, as set forth in the invention defined by the appended claims.

Summary of the invention

The object of the present invention can be achieved by an induction heated kettle as defined in claim 1. Preferred embodiments are defined in the dependent sub claims, explained in the following description and illustrated in the accompanying drawings. The induction heated kettle according to the invention is an induction heated kettle comprising a bowl having a bottom comprising a material suitable for being heated by generate eddy currents generated by an electromagnetic field, wherein the kettle comprises:

- one or more induction coils arranged to generate one or more electromagnetic fields that generate eddy currents in the bottom of the bowl, wherein the bowl and the one or more induction coils are integrated in the induction heated kettle, wherein at least one temperature sensor is arranged to measure a temperature of the bowl.

Hereby, it is possible to provide an accurate control of the temperature of the food being cooked.

In one embodiment, the kettle comprises a single induction coil arranged to generate an electromagnetic field that generates eddy currents in the bottom of the bowl.

In one embodiment, the kettle comprises two induction coils arranged to generate electromagnetic fields that generate eddy currents in the bottom of the bowl.

In one embodiment, the kettle comprises four induction coils arranged to generate electromagnetic fields that generate eddy currents in the bottom of the bowl.

In one embodiment, the kettle comprises more than four (e.g. 6 or 8 or more) induction coils arranged to generate electromagnetic fields that generate eddy currents in the bottom of the bowl.

It may be an advantage that the bowl comprises several temperature sensors each being arranged to measure a temperature of the bowl.

In one embodiment, the at least one temperature sensor is arranged in a hole provided in the bowl.

In one embodiment, at least one temperature sensor is arranged to measure a temperature of the bottom of the bowl.

It may be an advantage that the bowl comprises several temperature sensors each being arranged to measure a temperature of the bottom of the bowl.

In one embodiment, the material suitable for being heated by generate eddy currents is a ferromagnetic material.

In one embodiment, the material suitable for being heated by generate eddy currents is iron.

In one embodiment, the material suitable for being heated by generate eddy currents is steel.

In one embodiment, the material suitable for being heated by generate eddy currents is stainless steel.

In one embodiment, the bottom of the bowl comprises a plate comprising several metal layers.

In one embodiment, the bottom of the bowl comprises a sandwich plate having three metal layers.

In one embodiment, the middle layer arranged between the top layer and the bottom layer of the sandwich plate comprises aluminum.

In one embodiment, the middle layer arranged between the top layer and the bottom layer of the sandwich plate is made of aluminum.

The use of aluminum enables a fast heat transfer and thus a faster temperature regulation of the kettle.

In one embodiment, the top layer is made of stainless steel. This may be an advantage due to its durability. Moreover, stainless steel is easy to clean and has large mechanical strength.

In one embodiment, the kettle comprises a number of metal cores made in a ferromagnetic material.

In one embodiment, the kettle comprises a number of metal cores made in a ferromagnetic ceramic material.

In one embodiment, the kettle comprises a number of ferrite cores.

The cores are preferably arranged below the one or more induction coils. Hereby, the cores can be used to control (limit the extension of) the electromagnetic field(s).

In one embodiment, the kettle comprises an alternating current (AC) generator electrically connected to the one or more induction coils.

The AC generator is arranged and configured to generate an AC that enables one or more electromagnetic fields to be generated by means of the one or more induction coils.

In one embodiment, the kettle comprises a control unit arranged and configured to receive information from the at least one temperature sensor and to control the AC generator. Hereby, it is possible to regulate the AC generator on the basis of data from at least one temperature sensor. Accordingly, the temperature of the bowl can be controlled on the basis of the data from at least one temperature sensor.

In one embodiment, the kettle comprises a stirring mechanism for stirring ingredients in the bowl.

In one embodiment, the stirring mechanism comprises a centrally arranged shaft.

In one embodiment, the stirring mechanism comprises a centrally arranged shaft arranged inside a sleeve. In one embodiment, the stirring mechanism comprises an electric motor and a frequency inverter for controlling the speed of the motor.

In one embodiment, the motor is an AC motor.

In one embodiment, the motor is a three-phase AC motor.

In one embodiment, the motor is a DC motor.

In one embodiment, the kettle comprises a number of legs allowing the kettle to be positioned on a floor.

In one embodiment, the kettle comprises four legs.

In one embodiment, the kettle comprises six legs.

In one embodiment, the kettle comprises eight legs.

In one embodiment, the kettle comprises a mounting structure for mounting the kettle to a floor.

In one embodiment, the kettle comprises an insulation structure arranged between the bottom of the bowl and the one or more induction coils. Hereby, the insulation structure can protect the coils against the heat generated in the

In one embodiment, the insulation structure is an insulation layer.

In one embodiment, the insulation structure is made of a ceramic material (e.g. having a wool-like structure).

In one embodiment, the insulation structure is made of a ceramic material comprising S1O2, CaO and MgO. In one embodiment, the kettle comprises a temperature sensor arranged to detect a temperature of the one or more induction coils.

In one embodiment, for each of the one or more induction coils, the kettle comprises a corresponding temperature sensor arranged to detect a temperature of the relevant induction coil.

It may be an advantage that the control unit is configured to receive temperature data detected by the one or more temperature sensors.

In one embodiment, the bowl comprises one or more cooling fluid guiding structures arranged to allow a cooling fluid flow through the one or more cooling fluid guiding structures and hereby carry out heat exchange in order to change (e.g. reduce) the temperature of the bowl and/or the contents of the bowl.

In one embodiment, the fluid guiding structure(s) are provided in a side wall of the that the bowl.

In one embodiment, one or more of the at least one temperature sensors are arranged in a mounting arrangement comprising a force generating structure arranged to keep the temperature sensor in contact with the bottom of the bowl or with a thermally conducting structure arranged between the temperature sensor and the bottom.

In one embodiment, the force generating structure is a spring.

In one embodiment, the force generating structure is mounted in a bracket.

In one embodiment, the volume of the bowl is at least 75 liters.

In one embodiment, the kettle comprises a tilt mechanism. Description of the Drawings

The invention will become more fully understood from the detailed description given herein below. The accompanying drawings are given by way of illustration only, and thus, they are not limitative of the present invention. In the accompanying drawings:

Fig. 1 shows an example of prior art;

Fig. 2 shows a prior art mounting frame;

Fig. 3 shows a cross-sectional view of a prior art steam kettle;

Fig. 4 shows a kettle according to the invention;

Fig. 5 shows a close-up view of the bottom of a bowl of a kettle according to the invention;

Fig. 6 shows a kettle according to the invention;

Fig. 7 shows a sandwich plate of a bowl of a kettle according to the invention;

Fig. 8 shows an induction coil arrangement of a kettle according to the invention;

Fig. 9 shows another induction coil arrangement of a kettle according to the invention;

Fig. 10 shows a further induction coil arrangement of a kettle according to the invention;

Fig. 11 shows a cross-sectional view of a kettle according to the invention and

Fig. 12 shows a cross-sectional view of another kettle according to the invention.

Detailed description of the invention

In the is following, the three figures: Fig. 1, Fig. 2 and Fig. 3 are used to explain the prior art to better indicate the advantages of the invention over the prior art. The remaining figures Fig. 4 to Fig. 12 are shown in order to explain the invention in detail and disclose various embodiments of the induction heated kettle according to the invention.

In the figures, reference numeral 10 indicates the induction heated kettle. Reference numerals 26, 28, 30 indicate structures of a sandwich plate. Reference numerals 36, 38 and 40 indicate structures of a ventilation system. It is to be understood that numerals that refer to the same or similar elements essentially carrying out the same function. Fig. 1 shows a cooking kettle equipped with powered stirrer (according to EN 13886). The cooking kettle comprises a support pillar 1, a control pillar 3, a bowl 3, a pouring lip 4, a lid 5 and a bottom-mounted stirrer 6. Fig. 2 illustrates a prior art mounting frame configured to be used to fix a prior art steam heated kettle in a concrete floor. The electric power supply and water supply for a prior art steam heated kettle is routed in the floor and enter the kettle in one of the pillars. Fig. 3 illustrates a cross-sectional view of a prior art steam kettle 41. It can be seen that the steam kettle 41 comprises a steam generator 43 comprising a heating element 45. There are two heating principles for the prior art kettles: 1) heated by build-in steam generator 43 and 2) heated by steam from external source. The steam kettle 41 has a build- in steam generator 43. The working principle is a jacketed 41 bowl, in which the steam condensates and delivers the energy.

The water in the steam generator 43 is heated by electrical heating elements 45 and the water evaporates into the state of steam. As the steam rises along the inner sides of the bowl it delivers the energy to the wall and goes back to the state of water and runs back into the steam generator 43 and the process is started again.

As this example of a prior art kettle works with steam, the jacket 41 is and needs to be pressurized. To control the pressure the prior art kettle is equipped with a lot of features such as a pressure control, a pressure gauge and a safety valve, an air vent valve as well as level control for the water in the steam generator 43. When the heating process starts, the jacket 41 is filled with cold air. To drain out the air and give room for the steam the vent valve is open during start. When this prior art kettle cools down it will build up a vacuum in the kettle as the air/steam mixture cools down. This is also avoided by the vent valve.

Steam from external source

Using steam from an external source is quite complicated. Water used in the steam generator, the steam generator is outside the kettle, typically in a boiler room, must be treated for hard ness to avoid clogging the generator with limescale. Piping must be insulated to avoid heat loss. Condensate must be drained from the piping prior to use of this kettle to avoid 'water hammer'.

Typically, a pressure reduction valve must be placed up-steam of the kettle. It takes a positive pressure to return the condensate to the steam generator or a pump must be used. As the condensate is reused in the steam generator, a steam trap must be placed in the bottom of the kettle to separate steam and condensate. The heat generation in the jacket 41 is done in the same way as the build in generator. However, the condensate tends to queue in the generator when simmering for some time as there is no pressure to push it back to the steam generator.

Fig. 4 illustrates a kettle 10 according to the invention. Fig. 5 illustrates a close-up view of the bottom of the bowl 20 of the kettle 10 shown in Fig. 4. In one embodiment, the bowl 20 is at least partly made of a steel (e.g. stainless steel), and it is intended for heating, cooking or boiling food present in the bowl 20. In an embodiment of the invention the bowl has a volume of at least 75 liters. The bowl 20 comprises a side wall 68 and a stirring mechanism comprising a shaft arranged in a centrally arranged sleeve 62. In one embodiment, the bowl 20 comprises a bottom part 23 made of a sandwich swiss ply constructed plate comprising a top layer 26, a middle layer 28 and a bottom layer 30 (see Fig. 7 for a better view). In a preferred embodiment, the upper top layer 26 is made of a stainless steel material. Stainless steel may be chosen for both long durability and for hygienic purposes.

In one embodiment, the middle layer 28 comprises or is made of aluminium.

In one embodiment, the bottom layer 30 is made of a stainless steel material. Hereby, it is possible to provide a quick and an even power, energy and heat distribution through the bottom part 23 of the kettle 10.

An insulation layer 32 is placed below the sandwich plate. This insulation layer 32 protects the induction coils against heat from the bottom part 23 of the bowl 20. In one embodiment, the insulation layer 32 comprises a ceramic material.

The kettle 10 comprises a number of induction coils 33 arranged to generate one or more electromagnetic fields in order to generate eddy currents in the bottom 23 of the bowl 20. A number of cores 34 are arranged below the induction coils 33.

In one embodiment, the cores 34 ferrite cores 34 configured to control the magnetic field lines in order to control the heating of the kettle 10, when the induction coils 33 are provided with an AC. In one embodiment, the kettle 10 comprises a AC generator configured to generate an AC. Th AC may be a 560 V (rectified 400 V) 20kHz signal. The generator is preferably configured to be connected to the mains delivering a standard AC power voltage (e.g. 400 V at 50 Hz in Europe or 400-460 V at 60 Hz in USA). The AC generates electro-magnetic fields around the induction coils 33, and these electromagnetic fields generate eddy currents in the bottom 23 of the bowl 20, since the bottom part 23 of the bowl 20 is manufactured in a material suitable for being heated by generate eddy currents generated by an electromagnetic field. Such material may be a ferromagnetic material.

The generated eddy currents heat the bottom 23 of the bowl 20, the other parts of the bowl 20 and any food present in the bowl 20.

The cores 34 (e.g. ferrite cores 34) makes it possible to control the electromagnetic fields induced by the induction coils 33. A coordinate system comprising an X axis and a Y axis is illustrated.

The kettle 10 comprises temperature sensors 35 each being arranged to measure a temperature of the bowl 20. In a preferred embodiment, the temperature sensors 35 are arranged in a cavity provided in the bottom 23 of the bowl 20. The sensors 35 may have a sensing area provided in the distal portion of the sensors 35. Each sensor 35 is mounted in a bracket 48, in which the sensor 35 is pressed along the Y axis so that the distal portion of the sensor 35 is keep in contact with the bottom 23 of the bowl 20. Each bracket 48 is attached to a mounting plate 66 extending along the X axis. The sensors 35 have a cable 50 for being electrically connected to a control unit (see Fig. 6).

In a preferred embodiment, one or more additional sensors are positioned to detect the temperature of the induction coils 33. It is important that the induction coils 33 are cooled to ensure that they work effectively.

Fig. 6. Illustrates a kettle 10 according to the invention. The kettle 10 comprises a stirring mechanism 84 comprising an electric motor 58 and a shaft 60 arranged in a sleeve 62. The shaft 60 comprises an engagement portion 64 provided in the distal end of the shaft 60. The engagement portion 64 is configured to engage with a corresponding receiving portion of a stirring tool (not shown). The motor 58 is configured to rotate the shaft 60. The kettle 10 comprises a bowl 20 corresponding to the one shown in Fig. 4 and Fig. 5. The kettle 10 comprises a control unit 82 and an AC generator 80. The control unit is arranged and configured to receive information from the at least one temperature sensor 35 and to control the AC generator 80. Hereby, it is possible to regulate the AC generator 82 on the basis of data from at least one temperature sensor 35. Accordingly, the temperature of the bowl 20 can be controlled on the basis of the data from at least one temperature sensor 35. The control unit 82 is electrically connected to at least one temperature sensor 35 and to AC generator 80 by means of cables 78, 78'. It is important to notice that Tte control unit 82 and AC generator 80 may be arranged elsewhere, e.g. in a separate housing provided next to the bowl 20.

Cold air 36 is coming into a ventilation box 37 comprising an electric ventilator. In one embodiment, the ventilation is controlled the by the control unit 82 by using temperature measurements made by a temperature sensor arranged to detect the temperature at the induction coils 33. The air 36 flows along the induction coils 33. Hereby, the air 36 cools down the induction coils 33 so that at suitable working temperature can be maintained.

A high pressure builds up in the cabin 37 due to the hot air is coming out. The pressure gradient between the high pressure in the cabin 37 and the surroundings cause the hot air to flow out.

The ventilation system is constructed in such a manner that the hot air and the cold air 38 are avoided to get mixed. Cold air, from outside is sucked in by beans of the fan 38. This cold air cools down the induction coils 33. Hereby, the air is heated and let out again through the opening 40.

Fig. 7 illustrates a sandwich plate of a bowl of a kettle according to the invention. It can be seen that the sandwich plate comprises a middle layer (intermediate layer) 28 arranged between a top layer 26 and a bottom layer 30. In one embodiment, the middle layer 28 is made of aluminium. In one embodiment, the top layer 26 is made of steel (e.g. stainless steel). In one embodiment, the bottom layer 30 is made of steel (e.g. stainless steel).

Fig. 8 illustrates an induction coil arrangement of a kettle according to the invention. The coil arrangement comprises a single induction coil 33 and four ferrite cores 34 arranged to control the electromagnetic fields induced by the induction coil 33. The induction coil arrangement comprises a centrally arranged temperature sensor 35 arranged in a configuration, in which a spring 46 presses the temperature sensor 35 in a direction away from the ferrite cores 34. Fig. 9 illustrates another induction coil arrangement of a kettle according to the invention. The induction coil arrangement almost corresponds to the one shown in Fig. 8, however, it comprises a bevelled portion 70. Fig. 10 illustrates a further induction coil arrangement of a kettle according to the invention. The induction coil arrangement comprises four induction coils each arranged in an arrangement corresponding to the one shown in Fig. 9. It can be seen that the induction coil arrangement comprises a free space 72, in which a sleeve 62 and a shaft 60 is provided. It is important to underline that the number of induction coils of the induction coil arrangement of kettle may vary. Accordingly, the induction coil arrangement may comprise 1, 2, 4, 5, 6, 7,8 or more induction coils.

Fig. 11 illustrates a cross-sectional view of a kettle 10 according to the invention. The kettle 10 basically correspond to the one shown in Fig. 4.

The kettle 10, however, comprises a cooling arrangement comprising a plurality of cooling fluid guiding channels 76 and fluid guiding structures 77 provided in the side wall 68 of the bowl 20. In one embodiment, the fluid guiding structures 77 are arranged and configured to generate a turbulent flow of the fluid. Hereby, an improved (more efficient) heat exchange can be provided. Accordingly, the efficiency of the cooling arrangement can be enhanced. In one embodiment, the kettle 10 comprises a cooling unit (not shown) configured to cool the cooling fluid. In a preferred embodiment, the kettle 10 comprises a pump arranged to circulate the cooling fluid in a closed system, in which the cooling fluid leaves the cooling unit and inters the cooling fluid guiding channels 76 of the cooling arrangement, wherein the cooling fluid leaving the cooling fluid guiding channels 76 is pumped into the cooling unit for being cooled down. In one embodiment, the cooling fluid enters the cooling fluid guiding channels 76 at a first level at the bowl 20 and leaves the cooling fluid guiding channels 76 at a second level at the bowl 20, wherein the first level is a higher level (e.g. the top portion) than the second level (e.g. the bottom portion) of the bowl 20. In one embodiment, the cooling fluid guiding channels 76 constitute a helical structure.

Fig. 12 illustrates a cross-sectional view of another kettle 10 according to the invention. The kettle 10 basically correspond to the one shown in Fig. 4. The kettle 10, however, comprises a temperature sensor 74 provided in the side wall 68 of the bowl 20. It may be an advantage that the temperature sensor 74 is arranged close to the bottom 23 of the bowl. In one embodiment, the temperature sensor 74 is arranged in a distance of 10 cm or less from the bottom 23 of the bowl. In one embodiment, the temperature sensor 74 is arranged in a distance of 5 cm or less from the bottom 23 of the bowl.

Kettles known in the art are made to optimize the process of cooking in the commercial kitchen - both in economic and ergonomic, while cooking large portions. When cooking large portions in a pot on a stove, a large pot is needed, and this gives issues from above 50 - 70 liters - depending on choice of type of pot. Pots above 50 -70 liters have three problems when cooking in them on a stove. First problem is the diameter of the surface in the bottom, which is 400 mm and above. This is a problem because the standard within coil size on the market is that they are not larger than 300 mm. When cooking with pots above 400 mm in bottom diameter the pots does not get the best possible effect, because the coil is smaller than the bottom of the pot. Another issue is that the pot is bigger than the coil size, which means it takes up more space than a coil on a stove - this means it is difficult to have two pots next to each other when cooking and therefor nobody cannot make optimized cooking with big pots on a stove.

Second problem is the height of the pot, when cooking in pots above 50 - 70 liters. A standard stove is 850 - 900 mm in height, and a pot with 50 - 70 liters starts around 400 mm. This means the working height of this solution starts at 1250 mm. This is a very high Work height, when the user has to put ingrediencies in the pot, manually stir the pot and manually empty the pot.

The third problem is the weight of the pot, when it is full of food. This gives the user many heavy processes while cooking, emptying and afterwards cleaning.

All above mentioned issues is solved in the new induction heated kettle. The prior art steam kettle has always only had one option; to boil at approximately 100 degrees. If another process of cooking is needed, the kitchen needs another machine than a steam kettle. This could be, if they should make sous vide, then they should buy a sous vide machine. If they should fry a product before cooking it in the steam kettle, they should use a brat pan for the frying process. When a frying process is needed before cooking in a steam kettle, this would also mean more than one work process for the chef - by that saying using more time, chance of food waste and increased workload.

The induction kettle of the invention can cook in all these ways - giving may new opportunities for the chef and kitchen staff. A brat pan is developed for frying. The brat pan has a big cooking surface area and a small edge from bottom to top. This makes the cooking process easier when frying beef patties, meatballs, chicken breast etc. The brat pan is also designed with the right work height for the user and so the user does not get burn on the arm while frying the food - because of the height between bottom and top of the cooking surface.

A brat pan is comparable to the use of a pan on a stove in a kitchen and an induction kettle is comparable to the use of a pot on a stove in a kitchen. Kettles according to the invention, however, are made to optimize the process of cooking in the commercial kitchen - both in economic and ergonomic, while cooking large portions.

While the foregoing embodiments of the invention are at pre-sent considered to be preferred, it is understood that numerous variations e.g. in construction of the sandwich layers, the materials thereof, the temperature sensor(s), how to provide the AC power voltage, the alternating current drawn from the AC power voltage source, its shape, its RMS value and its frequency, it may be harmonic and/or with over harmonic frequencies be made therein by those skilled in the art and it is intended to cover in the appended claims all such variations and modifications as fall within the true spirit and scope of the induction heated kettle invention.

In one embodiment, the main material of the induction heated kettle is stainless steel. The bottom of the kettle (cooking surface) may be made of Swiss Ply, a product made of aluminium coated with stainless steel. Stainless steel is chosen due to durability, it is easy to clean and have a good strength. Because the invention, i.e. the induction kettle, is not a pressurized product, it has a lot of advantages in production and in the volume, weight of the materials over the prior art kettles. Why is the production easier of the inventions' induction kettle? When manufacturing traditionally steam heated kettles (of the prior art) with pressure above 0.5 bar, it is subject to the Pressure Equipment Directive, PED, which means: The design must be approved by Notified Body. When using the prior art solutions, you must have a Quality management system. Annually audits in the production by Notified Body. Moreover, the welder workers must pass exam every two years. Furthermore, all accessories for monitoring (pressure, level) and safety (safety valve) must be approved by PED.

The induction heated kettle according to the invention does not contain pressurized parts that's why the above-mentioned is-sues do not apply.

The induction heated kettle 10 of the present invention does not contain a double jacket (jacketed bowl - see figure 3). Accordingly, considerably less stainless steel is needed and accordingly a lower mass and weight can be acheived.

The welding job is correspondingly much less when the kettle of the invention is to be manufactured and mass produced. Further installation issues provide the invention induction heated kettle with advantages according to the following:

When installing the prior art steam heated kettles, the Pressure Equipment Directive distinguishes between the two types of kettles. The one kettle with build-in steam generator is called an 'assembly' which means it is a fully operational unit, which include safety accessories. The kettle is accompanied by an EC declaration of conformity for an 'assembly' and is ready to use.

The kettle which is supplied with steam from an external source is called a 'vessel' meaning the safety accessory is part of the fixed installation. This kettle is accompanied by an EC declaration of conformity for a 'vessel', meaning the kettle must not be used before a new risk assessment has been performed and a new EC declaration of conformity has been issued.

The induction heated kettles according to the invention are standing on a number of legs. The installation does therefore not require any comprehensive preparations. The legs of the induction heated kettle can be bolted and fixed to the floor with simple brackets.

Electrical AC power and water supply can be routed in the ceiling and made to enter the kettle from the above space over the kettle.

Why does the kettle of the invention offer more cooking opportunities than prior art kettles? A prior art kettle driven with steam can only operate between 80-120 degrees C. (because it has 1 bar pressure). In a heating interval between 80-120 degrees, the only cooking method is boiling. And because the prior art steam driven kettle is not very accurate in its precision. Then the user can not boil at a precise temperature (+/- 5 degrees).

The induction kettle of the present invention can work between 40 - 250 degrees C. and with a 1-degree precision (which in-deed is very precise!). Because of this the induction kettle of the present invention can make following cooking methods:

• Sous vide: Sous vide cooking (precision cooking at low temperatures. Must have 1-degree precision. Working between 40 - 75 degrees C.) This cooking method is very used because it extends durability of the cooked products, it makes sure that the products are loss less in production and keep a high level of uniformity after their production.

• Classic boiling: ca. 95- 100 degrees. But the precision cooking can give energy savings, because a lot of products are cooked lower than 100 degrees, and it demands precision to keep the temperature and have the energy saving.

Frying / crust: To fry or brown/make crust on vegetables, meat, fish or other products you must reach about 140 degrees. (The reaction is called the Maillard reaction by French chemist Louis Maillard, who described it in 1912. The Maillard reaction is the primary reaction that causes meat to have a crust and taste more aromatic. It works most effectively at 140 degrees and above.) (No wonder the food for the elderly is not tasting of anything when they never have been able to do this in a steam kettle).

• Precision cooking: It is very important to be able to keep the same temperature, if somebody wants to cook the same product every time or to make energy savings.

Steam heated of the prior art:

The temperature control system is very slow reacting. Any changes in heating of the prior art kettle is done by starting and stopping the heating elements in the steam generator. A big mass of water and steel therefor have to change temperature.

There is practically no heating of the prior art kettle bowl beneath 100°C as steam need to be formed in or-der to transfer heat. So, temperatures below 100°C, are problematic for the prior art kettle. At the same time the temperature span of the prior art kettle is limited to app. 120°C due to the pressure in the jacket. Temperature and pressure are evenly proportional.

Advantages of the kettle according to the invention :

The temperature control is very fast. The heat is generated directly in the bottom of the kettle of the present invention and the mass that needs to be heated before heating the food is quite low. The electronic control is a real PID system which re-acts very fast on changes. The bottom of an empty kettle (of the present invention) can be heated from 20°C to 200°C in 90 seconds. Temperature span of the induction heated kettle is 40-250°C. The induction of the present invention is controlled digitally and will therefore hit the right, and keep, the wanted required temperature. The steam kettle (of the prior art) will first "turn off" when it hits the marked temperature, but because power is still building up, the temperature will not stop at the marked temperature but go beyond it.

The induction kettle of the present invention is good at precision cooking, and it can save a lot of energy by not overheating and evaporating water. A lot of products are cooked at lower temperatures than 100 degrees. Potatoes are actually cooked at 96 degrees and not at 100 degrees, therefore there is a good saving in controlling the temperature precisely by using the kettle of the present invention.

Explanation of the higher efficiency of the present invention over the prior art kettles technology:

The energy used to heat the content of the two types of kettles are basically the same. The difference is the energy used to heat the kettle body and the losses to the surroundings.

Example: Heating of a 3001 kettle of the present invention

Conditions:

Heating from 10-100°C, 4 times a day, 220days a year

Specific heat: Stainless steel (0,5kJ/kg°C), water (4,18kJ/kg °C), copper (0,42kj/kg°C)

Steam heated kettle of the prior art:

Weight of inner part of the bowl 160kg, water in steam generator 30kg Heating elements (Copper) 3kg

å loss / sequence 5,2kWh

å loss / year 4547kWh

Stand-by power consumption is typically 20-40W (control volt-age transformer)

Induction heated kettle of the present invention : Weight of the bowl 48kg

å loss / sequence 0,6kWh

å loss / year 528kWh Stand by power consumption is typically < 1W (from the switch mode power supply)

Loss to surroundings:

Steam kettle of prior art. Outer side of the bowl is insulated. Bottom and steam generator are not insulated. Induction kettle of the present invention, it is insulated on all its surfaces. Better temperature control on the induction kettle - of the present invention - will minimize the heat loss when avoiding evaporating of water during simmering.

List of reference numerals

1 Support pillar

2 Control pillar

3 Bowl

4 Pouring lip

5 Lid

6 Stirrer

10 Induction heated kettle

20 Bowl

23 Bottom

26 Top layer

28 Middle layer

30 Layer

32 Insulation layer

33 Induction coil

34 Ferrite core

35 Sensor

36 Air

37 Cabin (ventilation box)

38 Fan

40 Opening

41 Jacket

43 Steam generator

45 Heating element

46 Spring

48 Bracket

50 Cable

52 Threaded rod (bolt)

54 Body portion

56 Arm

58 Motor

60 Shaft 62 Sleeve

64 Engagement portion

66 Mounting plate

68 Side wall

70 Bevelled portion

72 Free space

74 Temperature sensor

76 Cooling fluid channel

77 Cooling fluid guiding structure 78, 78' Cable

80 Electric generator

82 Control unit

84 Stirring mechanism

X, Y Axis

Claims

1. An induction heated kettle (10) comprising a bowl (20) having a bottom (23) comprising a material suitable for being heated by generate eddy currents generated by an electromagnetic field, wherein the kettle (10) comprises:

- one or more induction coils (33) arranged to generate one or more electromagnetic fields that generate eddy currents in the bottom (23) of the bowl (20),

characterised in that the bowl (20) and the one or more induction coils (33) are integrated in the induction heated kettle (10) and that at least one temperature sensor (35, 74) is arranged to measure a temperature of the bowl (20).

2. An induction heated kettle (10) according to claim 1, characterised in that at least one temperature sensor (35) is arranged to measure a temperature of the bottom (23) of the bowl (20).

3. An induction heated kettle (10) according to claim 1 or 2, characterised in that the material suitable for being heated by generate eddy currents is a ferromagnetic material.

4. An induction heated kettle (10) according to one of the preceding claims, characterised in that the bottom (23) of the bowl (20) comprises a sandwich plate having three metal layers (26, 28, 30).

5. An induction heated kettle (10) according to claim 4, characterised in that the middle layer (28) arranged between the top layer (26) and the bottom layer (30) of the sandwich plate (26, 28, 30) comprises aluminum.

6. An induction heated kettle (10) according to claim 4 or 5, characterised in that the top layer (26) is made of stainless steel.

7. An induction heated kettle (10) according to one of the preceding claims, characterised in that the kettle (10) comprises a number of ferrite cores (34) arranged below the one or more induction coils (33).

8. An induction heated kettle (10) according to one of the preceding claims, characterised in that the kettle (10) comprises an alternating currents (AC) generator (80) electrically connected to the one or more induction coils (33).

9. An induction heated kettle (10) according to claim 8, characterised in that the kettle (10) comprises a control unit (82) arranged and configured to receive information from the at least one temperature sensor (35, 74) and to control the alternating currents (AC) generator (80).

10. An induction heated kettle (10) according to one of the preceding claims, characterised in that the kettle (10) comprises a stirring mechanism (84) for stirring ingredients in the bowl (20).

11. An induction heated kettle (10) according to claim 10, characterised in that the stirring mechanism (84) comprises an electric motor (58) and a frequency inverter for controlling the speed of the motor (58).

12. An induction heated kettle (10) according to one of the preceding claims, characterised in that the kettle (10) comprises a number of legs allowing the kettle (10) to be positioned on a floor.

13. An induction heated kettle (10) according to one of the preceding claims, characterised in that the kettle (10) comprises an insulation structure (32) arranged between the bottom (23) of the bowl (20) and the one or more induction coils (33).

14. An induction heated kettle (10) according to one of the preceding claims, characterised in that the kettle (10) comprises a temperature sensor arranged to detect a temperature of the one or more induction coils (33).

15. An induction heated kettle (10) according to one of the preceding claims, characterised in that the bowl (20) comprises one or more cooling fluid guiding structures (76) arranged to allow a cooling fluid flow through the one or more cooling fluid guiding structures (76) and hereby carry out heat exchange in order to change the temperature of the bowl (20) and/or the contents of the bowl (20).

16. An induction heated kettle (10) according to one of the preceding claims, characterised in that one or more of the at least one temperature sensors (35, 74) are arranged in a mounting arrangement comprising a force generating structure (46) arranged to keep the temperature sensor (35, 74) in contact with the bottom (23) of the bowl (20) or with a thermally conducting structure arranged between the temperature sensor (35, 74) and the bottom (23).