Liquid heater and method for heating liquid

Abstract

A liquid heater (1) comprising a container (2) for containing a liquid to be heated, a base (3), a heating device (13), and a stirring device (12), The stirring device (12) constitutes a part of a heating device (13) up to a predetermined heating level (H), exhibits a heating temperature (TH) up to the heating level (H), and includes a rotor (11) and a drive mechanism (15); The first member (16) is magnetically coupled to the second member (17); The rotor (11) is configured to rotate the liquid in the container (2) and cause it to rise along the side (9), A liquid heater (1) and a method for heating a foamable liquid in the liquid heater (1), characterized in that the rotation speed of the rotor (11) is within a range of rotation speeds that causes a defined minimum amount of liquid in the container (2) to rise to a height at least equal to the heating height (H) and within which the surface of the heated liquid does not have a continuous foam surface.

Description

Technical Field

[0001] The present invention relates to a liquid heater according to the preamble of claim 1 and a method for heating a foaming liquid in a liquid heater according to claim 15.

Background Art

[0002] Liquid heaters that stir a liquid being heated, such as milk, during heating are known in the prior art.

[0003] US 9,107,533 B2 discloses an automatic milk frother comprising a container for holding milk, a base into which the container for heating and foaming the milk is inserted, a rotor of a stirring device for foaming the milk contained in the container, the rotor being held in the container, and a heating device for heating the milk held in the container. The rotor is driven by magnetic coupling via a motor disposed in the base. The container has no electrical components or a continuous drive shaft for the stirring device.

Summary of the Invention

Problems to be Solved by the Invention

[0004] A drawback of the milk frother according to US 9,107,533 B2 is that heating of the milk contained in the container is limited to cases where it is performed on the milk simultaneously with foaming.

[0005] However, when heating liquids for subsequent consumption by infants, the formation of bubbles or air bubbles in the liquid should be avoided. Avoiding the introduction of air helps alleviate common feeding problems such as colic and bloating. Furthermore, liquids, especially milk, should be heated gently, and so-called hot spots—areas with temperatures that damage nutrients, enzymes, and antibodies in the liquid being heated, particularly in breast milk—should be avoided. Scientific studies indicate that breast milk should not exceed a maximum temperature of 40°C when heated. See, for example, Bransburg-Zabary S, Virozub A, Mimouni FB, Human Milk Warming Temperatures Using a Simulation of Currently Available Storage and Warming Methods. PLoS ONE 10(6), published on 10 June 2015.

[0006] Herein, the object of the present invention is to create a liquid heater and method for heating foaming liquids, such as those initially described, that avoid or at least reduce the drawbacks of the prior art. The liquid heater and method are intended to enable the most uniform heating of the liquid contained therein without forming a superheated region within the liquid volume and without causing foaming of the liquid. Furthermore, the liquid should be heated as efficiently as possible. In addition, the liquid heater needs to be inexpensive to manufacture and easy to clean.

[0007] This objective is achieved by the liquid heater described in claim 1 and the method described in claim 15. Advantageous and further embodiments are described in the dependent claims. [Means for solving the problem]

[0008] The liquid heater according to the present invention is characterized in that, in operation, the rotor rotates the liquid contained in the container, raising the liquid level along the side, and the rotational speed of the rotor is within a range of rotational speeds such that a specified minimum amount of liquid in the container exposed to the rotating rotor is at least equal to the heating height, and the heated liquid does not contain the surface of continuous bubbles.

[0009] The method according to the present invention is characterized in that, in operation, the rotor rotates the liquid contained in the container and raises it to the side, the rotational speed of the rotor during rotation is within a range that raises a predetermined minimum amount of liquid in the container to a height at least equal to its heating level, and after the rotation of the rotor, the heated liquid obtained in the container still does not have a continuous surface of bubbles on its surface.

[0010] Liquid heaters are used to heat liquids, and in particular to heat milk, such as breast milk, powdered milk, or milk produced from animal milk. A liquid heater comprises a container provided for receiving the liquid to be heated, a base on which the container can be placed and from which it can be removed, a heating device designed to heat the liquid in the container, and a stirring device designed to agitate the liquid in the container. The container has a bottom and sides extending therefrom, and can be designed, for example, as a can that can be filled and emptied, and for this purpose may be provided with an openable and re-closeable lid and a handle for the user to grip. For example, the sides may be cylindrical. Preferably, the container is designed to hold a maximum intended filling amount of the liquid to be heated of 300 ml, preferably 200 ml, and particularly preferably 120 ml, although the amount of liquid that can actually be held may be higher. In operation, particularly for heating liquids, the container is positioned on a base that has the necessary electrical components to operate the liquid heater. For this purpose, the base may have a power cable for connection to a socket. The user of the liquid heater can remove it from the base to remove the heated liquid and clean the container.

[0011] The heating device is used to heat the liquid in the container and may include a control device for setting a desired target temperature for the liquid to be heated by the user. The sides of the container are part of the heating device up to a predetermined heating height, starting from the bottom, and include a heating temperature for heating the liquid, i.e., the heating height at which the liquid heater is operational. In this way, the liquid in the container is heated slowly through the sides. The side surfaces generally have a larger surface area than the bottom of the container, so the liquid can be heated particularly efficiently. Furthermore, due to the relatively large surface area of ​​the sides, particularly high heating temperatures can be avoided. For example, the heating temperature is up to 30 degrees, preferably 20 degrees, above the target temperature of the liquid being heated.

[0012] The stirring device comprises a rotor. The rotor is housed in a container and comprises a first member for generating a magnetic field or magnetism, and a drive mechanism for the rotor. The drive mechanism is housed in a base and comprises a second member for generating a magnetic field or magnetism. The first and second members may be permanent magnets or coils to which an electric current can be applied to generate a magnetic field, but the magnetizable first and second members may be particularly ferromagnetic. The rotor is housed in a container and is set to rotate by the drive mechanism provided in the base during the operation of the liquid heater, i.e., while the liquid in the container is being heated. For this purpose, the first member is magnetically coupled to the second member. The rotor is also magnetically coupled to the drive mechanism via the first and second members, and the drive mechanism is designed to rotate the rotor at at least one speed. The drive mechanism comprises a motor for this purpose, particularly an electric motor. As the rotor rotates while the liquid in the container is being heated, the heat introduced through the heating device is distributed as evenly as possible within the liquid volume without creating superheated areas, so-called hot spots. Avoiding such overheated areas and hot spots has a beneficial effect on the liquid's components and also prevents discomfort and injury when drinking the liquid if it is not stirred sufficiently beforehand.

[0013] To efficiently heat the liquid in the container while simultaneously minimizing the formation of bubbles, the rotor's rotation speed is set such that, during its rotation, a specified minimum amount of liquid in the container is raised to at least the heating level, and within the range of rotation speeds, the heated liquid does not develop a continuous surface of bubbles on its surface even after the rotor's rotation ends. Therefore, the drive mechanism is designed to rotate the rotor at a rotation speed that raises the liquid rotated by the rotor to at least the heating level, while avoiding the formation of a continuous surface of bubbles on the surface of the liquid itself, such as in (breast) milk, at the end of the rotor's rotation or after the rotor's rotation. In this way, even if a specified minimum amount of liquid in the container is efficiently heated, the entire surface of the container is heated so that the liquid is in contact with the entire surface. To achieve this, the rotor's rotation speed is set to be at least equal to or greater than the lower limit of the rotation speed range. Furthermore, by ensuring that the rotor's rotation speed does not exceed the upper limit of its rotation speed range, continuous foam formation on the surface is avoided even with effervescent liquids such as milk. This allows heated liquids to be consumed immediately after being removed from the container without ingesting air as foam formed on the liquid's surface. Avoiding foam formation is particularly advantageous when young children are drinking heated liquids. However, individual bubbles or areas covered with bubbles may appear on the surface of the heated liquid after the rotor has been running.

[0014] Any speed within the rotational speed range is suitable for raising the liquid in the container to at least a heated level and avoiding a continuous foam surface after the rotor rotates. The rotational speed or range of rotational speeds depends on numerous design-related parameters of the liquid heater. The drive mechanism can also be designed to adjust the rotational speed and / or range of rotational speeds to suit the properties of the liquid contained in the container. For example, a pre-programmed table or setting aid can be provided within the liquid heater to show the user the favorable rotational speed or range of rotational speeds for different liquids. Within the rotational speed range, the rotor rotational speed can be kept constant.

[0015] When references are made in descriptions of positions or directions such as above, above, below, or downward, these should be understood in relation to the position of use of the liquid heater and the state in which the liquid is heated within the container.

[0016] According to a preferred embodiment of the present invention, the density of the liquid is 1.018 to 1.048 g / cm³. 3 If the density is within this range, the Newton number corresponding to the agitator is 0.1 to 0.3, preferably 0.1 to 0.2. A liquid in this density range is substantially equivalent to the density of milk. If the surface tension and / or viscosity of the liquid is essentially equivalent to that of milk, the Newton number corresponding to the agitator is also preferably between 0.1 and 0.3, preferably between 0.1 and 0.2. In this case, the surface tension is in the range of 30 to 43.5 mN / m, and the viscosity is 1.06386 to 3.27726 mm 2 It can be in the range of / s. The given values ​​for density, surface tension, and viscosity depend on the temperature and type of liquid, especially milk. It is clear that differently designed rotors may require different rotational speeds to allow a specified minimum amount of liquid in a container to rise to at least a heating level. However, since the Newton number is a characteristic of the power introduced into the liquid through the rotor, different rotors can also have different Newton numbers. Thus, the design of the rotor is well determined by the Newton number. Therefore, rotors housed in a container can have various shapes. In particular, the Newton number indicates which ratio of the rotor's power P is actually available as hydraulic power. The following applies: Ne = P / (ρ * n 3 * d 5 ) Here: Ne... Newton number P... Rotor output, W ρ ... density of a liquid, kg / m³ 3 n ... rotational speed, s -1 d ... rotor diameter, m

[0017] The rotor output P is calculated from the rotor section modulus: P = M * 2 * π * n Here: P... Rotor output, W M... Rotor torque, Nm n ... rotational speed, s -1

[0018] Particularly preferable is a rotor output in the range of 0.05 to 0.1 W, a heating height ratio to rotor height in the range of 3 to 5, and a ratio of the envelope diameter of the container provided at the heating height to the envelope diameter of the rotor in the range of 1.20 to 1.4, with the rotor rotation speed in the range of 370 to 450 rpm. The rotor height is defined in the axial direction of the rotor, and the envelope diameter of the container or rotor is defined as the smallest circular diameter that completely accommodates the inside of the side surface of the container or rotor when viewed in the axial direction of the working fluid heater.

[0019] To enable the formation of a container without electrical components in the heating device, it is possible to provide that the heating device is an induction heating device. Thus, the container, particularly the sides, which are part of the heating device up to a heating height, can be heated by induction from an energy source supplied to the sides from the outside. For this purpose, the sides are made of a material that can be heated by induction, at least in the region up to the heating height.

[0020] To heat the liquid in the container, the base comprises a bottom and a side surface protruding therefrom, the side surface being arranged next to the side surface of the container positioned on the base and preferably having a magnetic field generating mechanism of the induction heating device up to a heating height, which is particularly preferred. Particularly preferably, the side surface of the base is at least partially curved around the side surface of the container. In particular, the side surface can be formed completely around the lateral surface, for example, in an annular or cylindrical shape. Thus, the container can be inserted into the base to heat the liquid. If the magnetic field generating mechanism of the induction heating device is arranged over as large an area as possible on the side surface of the base, the side surface of the container and the liquid in the surface container can be heated particularly efficiently. For example, the magnetic field generating mechanism can cover more than half of the surface area, particularly more than three-quarters of the surface area of the side surface. In particular, the magnetic field generating mechanism can be at least one coil that generates an alternating magnetic field when an alternating current flows through it.

[0021] When the bottom of the base also comprises a magnetic field generating mechanism of the induction heating device, the bottom of the container can also be heated, and the liquid in the container can be heated more efficiently. In this case, the bottom of the container is also made of a conductive material that can be heated by induction.

[0022] The container is preferably electrically insulated from the base to make it as easy as possible to clean and to eliminate electrical contacts that may damage the appearance. For this reason, the container has no electrical connection to the base and can be immersed in water for cleaning without worrying about damage to the contacts. Furthermore, since there are no electrical components, the bottom and side surfaces of the container can be made thin.

[0023] For the durable structure of the container, and for efficient heating of the liquid and most efficient prevention of foaming of the liquid within the container, the sides of the container may be made of metal, particularly stainless steel, and preferably cylindrical, at least up to the heating height. The side surfaces may also include a metal-free portion, such as a transparent observation window, preferably at least in the heating height region, to allow observation of the stirring process or the height of the introduced liquid. Stainless steel also offers the advantage of corrosion resistance.

[0024] If at least part of the bottom surface of a container is flat, the container can be easily designed, manufactured inexpensively, and securely placed on a support surface. The bottom side of the container bottom is understood to be the side of the container bottom that faces away from the inside of the container.

[0025] If the top side of the container bottom is flat and the rotor preferably lacks a circular or ring-shaped receptacle for the rotating shaft, the top side of the container bottom facing the inside of the container can be cleaned particularly easily and reliably. For this purpose, the top side of the container bottom does not have any cylindrical or peg-shaped projections that would serve as the rotor's axis of rotation. Furthermore, the rotor can be easily inserted into the container before the liquid heater is activated, without needing to be precisely positioned on or above the axis of rotation. This is particularly advantageous when the container has a small diameter relative to its height, making it difficult for the user to insert their hand into the container to a depth sufficient to precisely position the rotor on the axis of rotation. It is also preferable that the rotor does not have a circular or ring-shaped receptacle or recess for the axis of rotation, particularly a cylindrical receptacle or recess. This means that the rotor can also be cleaned easily and carefully, as it does not contain a receptacle or recess for the rotating shaft where residue of the heated liquid could accumulate.

[0026] To allow the container to be designed independently of the drive mechanism, it is advantageous that the second component of the drive mechanism is located below the bottom of the container, which is positioned on a base. In contrast, the rotor is located on or above the bottom of the container, which is positioned on a base. Since the second component of the drive mechanism and the first component of the rotor are magnetically coupled, and power is transmitted from the drive mechanism to the rotor via the bottom of the container, it is advantageous that the bottom of the container has thin walls for efficient power transmission. For example, the thickness of the bottom of the container is a maximum of 3 mm, preferably a maximum of 2 mm.

[0027] This is particularly advantageous when the rotor is magnetically centered by a second member of the drive mechanism while connected to it. In this way, the mechanical axis of rotation for the rotor can be distributed. The centering of the rotor, i.e., the rotor position that is convenient or necessary for agitating the liquid in the container, is achieved by the magnetic attraction between the first and second members. The distance between the second members of the drive mechanism and the distance between the first members of the rotor is particularly preferably as large as possible, for example, at least half, and preferably at least two-thirds, of the diameter of the rotor's envelope circle in order to transmit the highest possible torque from the drive mechanism to the rotor via the magnetic coupler. Furthermore, as a result of the large distance, the rotor can be reliably centered by a user outside the center of the bottom of the container, for example by touching the side, even if the rotor is inserted into the container.

[0028] To achieve a reliable magnetic connection between the rotor and the drive mechanism, it is preferable that the extension of at least one of the first and second members in a plane parallel to the bottom of the container positioned on the base is larger than the extension of at least one of the first and second members in a plane perpendicular to the bottom of the container positioned on the base. Preferably, at least one of the first and second bodies extends in a plane parallel to the bottom of the container positioned on the base by at least 10%, more preferably at least 20%, and particularly preferably at least 30% of the envelope diameter of the rotor.

[0029] To facilitate handling of the liquid heater, the rotor may be provided to be removable from the container without tools, and in particular to be freely movable in the radial direction. This allows the rotor to be removed from the container, for example, by rotating the container, which has been removed from the base, so that the bottom of the container faces upward, in order to clean the rotor and container. Removal of the rotor is further preferred according to this embodiment by the fact that the rotor of the container removed from the base is freely movable in the radial direction, i.e., there are no mechanical guides.

[0030] In a further embodiment, the rotor may be provided with at least two, preferably three, arms extending radially from the rotor, on which the first member is positioned. The arms projecting from the center or center of gravity of the rotor serve to agitate the liquid. Furthermore, the positioning of the first member on the arms, in particular on the radially outer half or radially outer third of the arms, enables efficient transmission of torque from the drive mechanism to the rotor. For example, the arms of a rotor inserted into a container run in a plane at least partially parallel to the bottom of the container. It is also preferable that the longitudinal length of the arms in the radial direction of the rotor is greater than the vertical length of the arms in the axial direction of the rotor.

[0031] To ensure efficient stirring of the liquid and minimize torque transmission from the drive mechanism to the rotor, the rotor is preferably provided with three curved arms within the rotor plane, preferably in the direction of rotation, and preferably with an axially projecting vertical surface acting as a bearing surface on the side facing the bottom of the container. The rotor plane runs perpendicular to the virtual axis of rotation of the rotor, i.e., perpendicular to the axial direction of the rotor. The curvature of the arms in the direction of rotation promotes stirring of the liquid. The projection that functions as a bearing surface and protrudes axially from the rotor advantageously reduces the frictional resistance of the rotor held in the container on the bottom of the container. For example, the height of the axially projecting rotor can be a bulge or pin toward the bottom of the container.

[0032] The present invention is described in more detail below by preferred embodiments, but is not limited thereto. The drawings show: [Brief explanation of the drawing]

[0033] [Figure 1] Figure 1 is a perspective view of a liquid heater with a lid according to the present invention.

[0034] [Figure 2] Figure 2 is a perspective view of the liquid heater shown in Figure 1 without the lid.

[0035] [Figure 3] Figure 3 is a view of the liquid heater shown in Figure 2 from above, showing a portion of its interior.

[0036] [Figure 4] Figure 4 is a cross-sectional view of the liquid heater shown in Figure 1.

[0037] [Figure 5] This is another cross-sectional view of the liquid heater in Figure 1, corresponding to the portion rotated 90° compared to Figure 4.

[0038] [Figure 6] Figures 6(a) to 6(d) show the rotor of the liquid heater in Figure 1 viewed from different directions.

[0039] [Figure 7] Figure 7 shows the rotor output as a function of time.

[0040] [Figure 8] Figure 8 shows the Newton number as a function of time. [Modes for carrying out the invention]

[0041] Figure 1 shows a liquid heater 1 according to the present invention, comprising a container 2 (not shown in Figure 1) for receiving a liquid to be heated (not shown), a base 3 on which the container 2 is positioned or mounted depending on the position of use, a lid 4 which can be removed or opened in a different manner to cover or close the container 2, and a handle 5 (not shown) for facilitating the user's grip of the liquid heater 1. Furthermore, an operating element 6 in the form of a power button 6a is shown. The base 3 comprises a bottom surface 7 and a side surface 8 projecting upward from there toward the lid surface 4, the side surface 8 enclosing most of the container 2. The bottom surface 7 of the base 3 may include a cavity for housing components of the liquid heater 1 housed inside, as shown, for example, in Figure 4. In the example shown in Figure 1, the container 2 is completely enclosed by the base 3 and the lid surface 4. In another embodiment (not shown), the container 2 may be partially enclosed or covered by the base 3 and the lid surface 4.

[0042] Figure 2 shows the liquid heater 1 of Figure 1 without the lid 4, so that the container 2, and in particular the side 9 of the container 2, are visible. In the illustrated example, the container 2 also has a handle 5 and a lip 10 and is at least partially cylindrical. Preferably, the side 9 of the container 2 is at least partially cylindrical.

[0043] Figure 3 shows the liquid heater 1 of Figure 2 viewed from above, housed within the container 2. The container 2, which is placed on or inserted into the base 3, and the rotor 11 of the stirring device 12 housed within the container 2 for stirring the liquid in the container 2 are clearly identifiable. The rotor 11 can be made of, for example, plastic, particularly polypropylene.

[0044] Figure 4 shows a vertical cross-sectional view of the liquid heater of Figure 1. Clearly recognizable are the container 2, the base 3, the heating device 13 for heating the liquid in the container 2, and the stirring device 12. The container 2 comprises a bottom 14 and a side 9 extending from the bottom 14. The side 9 is part of the heating device 13 up to a predetermined heating height H on the side 9, and the heating height H extending from the container bottom 14 and the side 9 includes a heating temperature TH up to the heating height H for heating the liquid. The stirring device 12 comprises a rotor 11 housed in the container 2 and a drive mechanism 15 for the rotor 11 housed in the base 3, the rotor 11 comprising a first member 16 that generates a magnetic field, i.e., is magnetic, and the drive mechanism 15 comprising a second member 17 that generates a magnetic field, i.e., is magnetic. The drive mechanism 15 is designed to rotate the rotor 11 at at least one rotational speed, to which the first member 16 is magnetically coupled to the second member 17, and the drive mechanism 15 comprises a drive device 18, in particular a motor 18a, especially preferably an electric motor 18b, which can be operated at a specified rotational speed. The rotational speed of the rotor 11 is a range of rotational speeds in which the rotor 11 raises a specified minimum amount M of liquid in the container 2 to at least a heating height H during its rotation, and the heated liquid is within a range of rotational speeds in which no continuous surface of bubbles is formed on its surface O after the rotation of the rotor 11. In Figure 4, the minimum liquid volume M in the container 2 is symbolically represented by the surface O of the liquid. In the illustrated embodiment, the heating device 13 is an induction heating device 13a. In Figure 4, it can be seen that the side surface 8 of the base 3 rising upward from the bottom 7 of the base 3 is positioned next to the side surface 9 of the container 2 positioned on the base 3, and preferably includes a magnetic field generating mechanism 13b of the induction heating device 13a up to a heating height H. Furthermore, the side 8 of the base 3 can be understood as a side wall with considerably varying wall thickness to accommodate the magnetic field generating mechanism 13b of the induction heating device 13a. The magnetic field generating mechanism 13b of the induction heating device 13a may be, for example, at least one coil 13c connected to an AC current source (not shown) that generates an AC magnetic field during the operation of the liquid heater 1. This alternating magnetic field heats the side 9 of the container 2, and therefore heats the liquid inside the container 2. For this purpose, it is preferable that the side 9 of the container 2 be made of metal, particularly stainless steel, at least up to the heating height H.Furthermore, the bottom 7 of the base 3 may be equipped with a magnetic field generating mechanism 13b of the induction heating device 13a, which may generate an additional magnetic field. This is symbolically shown in Figure 4 by extending the magnetic field generating mechanism 13b down to below the rotor 11. Of course, the magnetic field generating mechanism 13b that generates an additional magnetic field may also extend below the bottom 14 of the container.

[0045] Figure 4 also shows that the container 2 is electrically insulated from the base 3, meaning there is no electrical connection between the container 2 and the base 3. In particular, the container 2 has no components that conduct electricity during the operation of the liquid heater 1.

[0046] Furthermore, in the example shown in Figure 4, it can be seen that at least one bottom surface 19 of the container bottom 14 is flat. Similarly, the upper surface 20 of the container bottom 14 may also be flat. The flat bottom surfaces 19 and / or upper surfaces 20 allow for slight undulation, especially for the manufacturing process, but there are no heights or depressions where the dimension in the axial direction A of the liquid heater 1 is greater than the thickness of the container bottom 14.

[0047] In the example shown in Figure 4, the second member 17 of the drive mechanism 15 is positioned below the bottom 14 of the container 2, which is positioned on the base 3. Therefore, the bottom 14 of the container does not require any recesses or indentations to receive the second member 17. The rotor 11 is positioned inside the container 2 and magnetically coupled to the drive mechanism 15, and is magnetically centered by the first member 16 of the rotor 11 and the second member 17 of the drive mechanism 15. In particular, according to the example shown in Figure 4, the rotor 11 can be removed from the container 2 without tools and is freely movable in the radial direction R.

[0048] Figure 5 shows another cross-sectional view of the liquid heater from Figure 1, generated by a cross-sectional plane rotated by 90° compared to Figure 4. Also in Figure 5, the outer diameter KB of the container 2 is shown, which is measured inside the side 9.

[0049] Figures 6a to 6d show an exemplary rotor 11, which in the illustrated example includes at least two sets of three arms 21 extending radially R of the rotor 11, on which the first member 16 is positioned. Figure 6(a) is the bottom surface of the rotor 11, which faces the bottom surface 14 of the container when the liquid heater 1 is in operation. Figure 6(b) shows a side view of the rotor 11, Figure 6(c) shows a top view of the rotor 11 facing away from the bottom surface 14 of the container when the liquid heater 1 is in operation, and Figure 6(d) shows a cross-sectional view of the rotor 11 along the line CC. The rotor 11 has a height HR and a diameter (envelope diameter KR).

[0050] In the example shown in the figures, it can be seen in Figures 6a to 6c that the rotor 11 does not have a circular or ring-shaped receptacle or any other arbitrary recess for the rotation axis. Furthermore, it can be seen that the rotor 11 consists of three arms 21 curved in the rotor plane E, and in the example shown in the rotation direction DR, a projection 22 that protrudes in the axial direction A as a bearing surface on the side facing the bottom surface 14 of the container, particularly at the center of the rotor 11.

[0051] Figure 7 shows the rotor output P (watts) as a function of time t (seconds) for three different rotor-rotation speed combinations. Combination 1: Rotor height HR = 16.5mm, rotor diameter KR = 70mm, rotational speed = 380rpm Combination 2: Rotor height HR = 16.5mm, rotor diameter KR = 65mm, rotational speed = 390rpm Combination 3: Rotor height HR = 10.73mm, rotor diameter KR = 70mm, rotational speed = 420rpm

[0052] Figure 8 shows the Newton's number Ne as a function of time t (seconds) for three rotor-rotation speed combinations from Figure 7.

[0053] Tests were conducted using the aforementioned liquid heater 1 to determine the rotor dimensions and associated rotational speed range such that, during rotation, the rotor 11 raises a specified minimum amount of liquid in the container 2 to at least a heating level H, thereby preventing the heated liquid from forming a continuous bubble surface on its surface after the rotor 11 has rotated.

[0054] The test results are shown in Tables 1 and 2 below. [Table 1]

[0055] [Table 2]

[0056] The test results indicate that rotors 11 with numbers 1, 2, and 7 are particularly suitable for achieving the set objective. Rotors 11 with numbers 8 through 11 are also at least conditionally suitable. In particular, with these rotors 11, if 60 ml or 100 ml is picked up as the defined minimum amount of liquid in container 2 at the specified minimum rotational speed, the side 9 can wet the liquid up to the heating height H. In addition, up to the specified maximum rotational speed, the heated liquid did not produce a continuous foam surface on its surface at the end of the stirring process. Milk at 7°C was used as the liquid to be heated.

[0057] The liquid heater 1 can be designed and operated with the following characteristic values, for example:

[0058] Container inner diameter: 84.7 mm Heating height: approx. 50mm Rotor height: 10.725 mm Ratio of heating height to rotor height: 4.662 Rotor diameter: 65mm Ratio of the inner diameter of the container to the diameter of the rotor: 1.303 Maximum rotation speed at which the liquid does not foam (60ml milk): Approximately 450 rpm (depends on the rotor shape) Minimum rotor power output: P = 0.05 W Newton's number: Ne = 0.1

[0059] If the height HR or diameter KR of the rotor 11 is small, a higher rotational speed will be required to allow the rotation of the rotor 11 to raise the liquid to the heating height H on the side surface 9, but this rotational speed may cause bubbles to form on the surface of the liquid.

Claims

1. A liquid heater (1) comprising a container (2) for containing a liquid to be heated, a base (3) on which the container (2) is positioned, a heating device (13) for heating the liquid in the container (2), and a stirring device (12) for stirring the liquid in the container (2), The container (2) includes a bottom (14) and a side (9) extending from the bottom (14), The side surface (9) from the bottom (14) to a predetermined heating height (H) on the side surface (9) constitutes part of the heating device (13), and indicates the heating temperature (TH) for heating the liquid up to the heating height (H). The stirring device (12) includes a rotor (11) housed in the container (2) and containing a first member (16) capable of generating or magnetizing a magnetic field, and a drive mechanism (15) for the rotor (11). The drive mechanism (15) is housed within the base (3) and includes a second member (17) capable of generating or magnetizing a magnetic field, and the drive mechanism (15) is designed to rotate the rotor (11) at at least one speed at which the first member (16) is magnetically coupled to the second member (17). The rotor (11) is configured such that, in operation, the liquid contained in the container (2) rotates and rises along the side surface (9). The rotational speed of the rotor (11) is such that it raises the defined minimum amount of liquid in the container (2) to at least the heating height (H), and within the range of rotational speeds, the surface of the heated liquid does not have a continuous surface of bubbles. The liquid heater (1) described above, characterized in that, for liquid densities in the range of 1.018 to 1.048 g / cm³, the Newton number corresponding to the stirring device (12) is 0.1 to 0.

3.

2. 1.018~1.048g / cm ３ In the case of the density of the liquid in the range of , the Newton number corresponding to the stirring device (12) is characterized in that it is 0.1 to 0.

2. The liquid heater (1) according to claim 1.

3. The output of the rotor (11) is set to a range of 0.05 to 0.1 W, the ratio of the heating height (H) to the height (HR) of the rotor is set to a range of 3 to 5, the ratio of the envelope diameter (KB) of the container (2) provided at the heating height (H) to the envelope diameter (KR) of the rotor (11) is set to a range of 1.20 to 1.4, and the rotational speed of the rotor (11) is set to a range of 370 to 450 rpm. A liquid heater (1) according to claim 1 or claim 2.

4. The heating device (13) is characterized in that it is an induction heating device (13a), The liquid heater (1) according to claim 1.

5. The base (3) comprises a bottom (7) and a side surface (8) protruding therefrom, is positioned adjacent to the side surface (9) of the container (2), is positioned on the base (3), and is characterized by comprising the magnetic field generating mechanism of the induction heating device (13a). The liquid heater (1) according to claim 4.

6. The container (2) is characterized by being electrically insulated from the base (3), The liquid heater (1) according to claim 1.

7. The side surface (9) of the container (2) is made of metal at least up to the heating temperature (H), The liquid heater (1) according to claim 1.

8. The bottom portion (14) is characterized in that at least the bottom side surface (19) is flat. The liquid heater (1) according to claim 1.

9. The upper surface (20) of the bottom (14) of the container is flat. The liquid heater (1) according to claim 1.

10. The second member (17) of the drive mechanism (15) is positioned below the bottom (14) of the container (2) located on the base, The liquid heater (1) according to claim 1.

11. The rotor (11) is characterized in that it is magnetically positioned in the center while being connected to the drive mechanism (15) by a second member (17). The liquid heater (1) according to claim 1.

12. The rotor (11) is characterized in that it can be removed from the container (2) without tools. The liquid heater (1) according to claim 1.

13. The rotor (11) is characterized in that it comprises at least two arms (21) extending radially (R) from the rotor (11), and the first member (16) is positioned on the arms (21). The liquid heater (1) according to claim 1.

14. The rotor (11) is characterized by having three arms (21) that are curved in the rotor plane (E), The liquid heater (1) according to claim 1.

15. A method for heating a foaming liquid in a liquid heater (1), wherein the liquid to be heated is contained in a container (2) in a state where it does not have a continuous foam surface on its surface, the container (2) is positioned on a base (3), the liquid in the container (2) is heated by a heating device (13), and the liquid in the container (2) is stirred by a stirring device (12). The container (2) includes a bottom (14) and a side (9) extending from the bottom (14), The side (9) from the bottom (14) to a predetermined heating height (H) on the side (9) constitutes part of the heating device (13), and indicates the heating temperature (TH) for heating the liquid up to the heating height (H). The stirring device (12) includes a rotor (11) housed in a container (2), the rotor (11) is equipped with a first member (16) capable of generating or magnetizing a magnetic field, The drive mechanism (15) includes a second member (17) housed within the base (3) that is capable of generating or magnetizing a magnetic field. This drive mechanism (15) rotates the rotor (11) at at least one rotational speed, and in that rotation, the first member (16) is magnetically coupled to the second member (17). The rotor (11), in operation, rotates the liquid contained in the container (2) and causes it to rise along the side (9), and during rotation, raises a defined minimum amount of liquid in the container (2) to at least a height equal to the heating height (H), and within the range of the rotational speed, the heated liquid obtained in the container (2) after the rotation of the rotor (11) does not still have a continuous surface of bubbles on its surface. The density range of the liquid contained in the container (2) is 1.018 to 1.048 g / cm³. ３ A method for heating a liquid, characterized in that, in this case, the Newton number corresponding to the stirring device (12) is 0.1 to 0.3.

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