Patent Description:
For some beverages, such as coffee, chocolate or milk, etc., it may be desirable to froth and/or heat the beverage. For this purpose, a so-called stand-alone frother may be used that may comprise a heated liquid-container and an integrated motor-driven whisk or the like. A drawback of such a frother is that cleaning of the liquid container as well as the whisk may be difficult. The beverage may burn against the heated container wall, making cleaning cumbersome. Further, the design freedom of such a frother may be limited, because the components need to be adapted to the cleaning requirements. In particular, the design must allow the removal of burnt beverage, e.g. milk from the container wall.

Furthermore, handheld frothers are known. This type of frother may comprise a whisk that can be immersed into the beverage for frothing. A drawback of such a frother is that, when a hot beverage is desired, the drink needs to be heated up separately, rendering the entire preparation process cumbersome and lengthy.

<CIT> describes a heating assembly for a kitchen appliance such as a blender, for passively heating food, comprising a heating member for generating heat by means of relative motion. The heating member is arranged adjacent a component of the kitchen appliance with which there is relative motion so as to generate heat, and means are provided for adjusting the heating member so as to adjust the heat generated.

There may therefore be a need to improve frothing of liquids, more specifically beverages, particularly in terms of making it less cumbersome and/or making it more comfortable. The object of the present invention is solved by the subject-matter of the appended independent claims, wherein further embodiments are incorporated in the dependent claims.

According to claim <NUM>, there is provided a device for frothing milk, comprising:.

As used herein, the term "drive unit" may be any suitable electrically operated device allowing for movement, e.g. rotation and/or translation, of the frothing means. For example, the drive unit may include an electric motor that allows battery operation, mains operation or a combination of both. Preferably, the drive unit comprises an electrical connection for the supply of electrical energy and/or power.

As used herein, the term "heating unit" may be any suitable electrically operated device configured to convert electrical energy into thermal energy and configured to transfer such thermal energy, e.g. in the form of heat, to another entity, its surroundings, or the like. For example, the transfer of heat from the heating unit to the frothing means may be based, at least partially, on thermal conduction, thermal convection, and/or thermal radiation. The heating unit may be stationary in relation to the drive unit and/or the frothing means, or move, e.g. rotate and/or translate therewith. Preferably, the heating unit comprises an electrical connection for the supply of electrical energy and/or power.

As used herein, the term "frothing means" may in principle comprise any type of drivable and/or movable means that can meet the conditions in terms of total contact surface area and heat transfer. The frothing means may for example be detachably or fixedly connected to the drive unit via e.g. a rod-shaped element, or the like. Alternatively, the frothing means may for instance be driven contactless, e.g. via an alternating, for instance a rotating magnetic field. During operation, the frothing means is at least partially immersed into or surrounded by the liquid.

Thus, the term "operably connected or connectable" as used herein may include a fixed connection or a detachable connection. The connection may include a mechanical and/or electrical connection. It may include a contactless connection (e.g. based on a magnetic field, induction, radiation, etc.). The connection may be a direct connection, or may include one or more intermediate components.

The frothing means may be operably connected or connectable to the drive unit via a first connection and to the heating unit via a second connection. The first and second connection may differ from each other or comprise, at least partly, the same components.

The "transfer of thermal energy" (e.g. heat) from the frothing means to the liquid may be based on thermal convection. In some embodiments, the frothing means may be formed from a metal material, such as aluminum, steel, stainless steel, any alloy thereof, or the like.

The term "total contact surface" as used herein, may refer to that surface of the frothing means that receives thermal energy from the heating unit and in use may contact the liquid, when immersed therein. In use, the liquid may be partially displaced due to the movement of the frothing means. Therefore, the total contact surface may also be understood as that surface of the frothing means that, when immersed in a volume of liquid as intended, and without being moved by the drive unit, contacts said liquid.

The provided device may improve frothing of liquids, since the functions of frothing and heating are combined in a single component: the frothing means. Thus, frothing and heating can be done simultaneously, by the same means, making frothing less cumbersome then some prior art methods. Also, cleaning of the device may be easier, since there is no separate heating means to be cleaned. Only the frothing means needs cleaning. Also, the risk of liquid, e.g. milk, getting burnt to the heating surface is small or at least smaller then in conventional milk frothers, because the heating surface forms part of the frothing means that in use are in continuous movement relative to the liquid, so the liquid gets no chance to stick thereto and/or become burnt. This will make cleaning easier.

The total contact surface area of at least <NUM><NUM> ensures that sufficient heat can be transferred to the liquid in an acceptable amount of time, taking into account a liquid volume between for instance <NUM> and <NUM> (which corresponds to an average beverage serving).

Preferably, frothing and heating are done simultaneously. However, according to an embodiment, the heating unit and drive unit may be controlled and/or powered independently of each other, thus allowing for example the heating unit to be powered off, at least temporarily, to allow only frothing, e.g. to prepare a cold frothed beverage. Similarly, the drive unit may be powered off, at least temporarily, to allow only heating, e.g. to prepare a hot, unfrothed beverage.

According to an embodiment, the frothing means may be operably connected to or connectable to the heating unit by means of a rod. The rod may serve to transfer thermal energy from the heating unit to the frothing means, e.g. via thermal conduction.

The frothing means may be operably connected to or connectable to the drive unit by a rod, e.g. the same rod or a different rod. The rod may serve to transfer kinetic energy of the drive unit to the frothing means, e.g. to rotate or translate the frothing means. The rod may for instance be detachably or non-detachably connected to the heating unit and/or the drive unit. It may coincide or be aligned with a drive axis of the drive unit.

According to an embodiment, the frothing means comprises at least one plate shaped member contributing to the total contact surface area.

The term "plate shaped" as used herein may refer to a member or portion of the frothing means, having a width extending in a first direction, a length extending in a second direction and a thickness extending in a third direction, wherein the width and length each are considerable larger than the thickness. For instance, the width and the length may each be at least two times larger than the thickness, more preferably at least five times larger, and most preferably at least ten times larger. The width and length may for instance span a surface to which the thickness may extend transversely or perpendicularly. The cross section of the plate shaped member may be angular, more particular rectangular. The plate shape does not necessarily have to be flat; it may for instance be curved, bent or angled, etc. The plate shaped member may for instance include a blade, a disc, a fin, or the like. With such plate shaped member, the total contact surface area may easily be maximized and/or adjusted, for instance by varying the length and/or width of the member. Further, such plate shaped member (or part thereof) may easily be curved, bent or otherwise deformed, to create turbulence in the liquid during use (e.g. similar to a propeller or the like). This may enhance the mixing of liquid and air and thus enhance the frothing process. Preferably, the frothing means are shaped in such way that little to no propulsion is generated when immersed and moved, e.g. rotated, in the liquid.

In an embodiment, the plate shaped member may comprise at least one slot or recess.

The slot or recess may for instance extend, at least partially, through a flat side of the plate shaped member. It may for instance have an open U-shape form, at an edge of the member, or be an enclosed recess. It may penetrate the member completely, like a through hole, or be formed as a pocket or blind hole.

Thus, the contact surface area of the frothing means may be further increased. Additionally, the slot or recess may enhance the turbulence generating properties of the frothing means, allowing better mixture of liquid and air.

According to an embodiment, the plate shaped member, or at least a portion thereof, may have an inclined orientation relative to a rotary axis of the frothing means. Such angled orientation may again help to create turbulence during frothing, which may help to get air mixed into the liquid.

According to an embodiment, the plate shaped member projects in radial direction from a rotary axis of the frothing means (<NUM>) such that at least three sides of the plate shaped member are exposed to contribute to the total contact surface area.

The plate shaped member may for instance with one side be coupled, connected or otherwise associated to aforementioned rod. Thus, the required total contact surface area of at least <NUM><NUM> can more readily be achieved, since at least three sides of the plate shaped member may be exposed to the liquid, in use, when immersed in said liquid and thus may contribute to the total contact surface area.

In an embodiment, the frothing means may comprise a number of plate shaped members. The members may for instance be shaped like fins.

The term "fin" as used herein may be understood as a kind of extended surface as for instance used in the field of heat transfer. The fin surface may extends from an axis (e.g. of the heating unit and/or the drive unit) to increase the contact surface area and with that the rate of heat transfer to or from the environment by increased convection.

For example, the number of members or fins may be <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, etc. These members or fins may extend radially from a rod that operably connects the members to the heating unit and/or the drive unit. The members or fins may extend at different positions along a circumference of the rod, to form for instance a propeller-like frothing means. Alternatively or additionally, the members of fins may extend at different positions along the length of the rod, to form several propeller layers. Thus, together the members or fins may form a propeller-like frothing means, with one or more propeller layers. Such propeller-like frothing means may have good frothing properties.

In addition, by providing more than one member or fin, the total contact surface area of the frothing means may be further increased, which may for instance allow the heat transfer rate to be increased and/or the heating time to be reduced. Alternatively, the dimensions of the individual members or fins may be reduced.

The member(s) or fin(s) may be made from a heat conductive material, e.g. from a metal material, such as steel, aluminum and/or a suitable alloy. They may have a uniform or varying cross-section. The required total contact surface area of the frothing means and/or required geometric parameters may be determined based on heat transfer requirements, assumptions, if needed, and using existing heat transfer calculation models. In an embodiment, the heating unit may comprise an induction heating unit adapted to inductively heat the frothing means.

For example, the induction heating unit may comprise an electromagnet and an electronic oscillator that passes a high-frequency alternating current (AC) through the electromagnet. The alternating magnetic field may penetrate e.g. the aforementioned rod and/or the frothing means, generating electric currents flowing through the parts, and due to resistance of the parts' material cause the parts to heat up. Alternatively, the heating means may comprise a cartridge heater or the like.

Cartridge heaters are known per se, so are not described in detail here. Such a cartridge heater may for instance be tube-shaped and may at least partially extend along or around a drive axis of the drive unit. It may, for example, contact aforementioned rod, be arranged and/or guided inside the rod, rotate with the rod, or be stationary with respect to the rod (via suitable bearings or the like), etc..

According to an embodiment, the frothing means may comprise a total heat transfer rate of at least <NUM> W, preferably of at least <NUM> W, further preferably of at least <NUM> W, and particularly preferably of at least <NUM> W.

This total heat transfer rate may be adjusted by varying, for example, the total contact surface area of the frothing means, the geometry of the frothing means, a heat transfer coefficient of the components involved in heat transfer, etc..

The required heat transfer rate may vary dependent on e.g. the volume and/or type of liquid to be heated, an initial temperature of the liquid, a desired end temperature of the liquid, material and other properties of the frothing means, etc. By way of example, the volume of liquid may be between about <NUM> and about <NUM>, preferably about <NUM>, the heat transfer coefficient may be between about <NUM> W/m<NUM> and about <NUM> W/m<NUM>, preferably about <NUM> W/m<NUM>. Thus, a desired volume of liquid may be heated to a desired temperature in a reasonable time.

According to another embodiment, the device may be configured as a handheld frothing device. The drive unit and the heating unit may be arranged in a housing that is at least partially configured as a handle, to be gripped by a user. The frothing means is connected to or connectable to the heating unit and the drive unit via a rod. The frothing means may be immersed by a user in a liquid container, such as a cup or mug, holding a beverage to be heated and/or frothed.

According to a further embodiment, the housing may be provided with attachment means, adapted for attachment to a container. The container may be provided with cooperating attachment means. For example, the housing and/or the container may comprise a threaded connection, a bayonet type connection, a clamp or snap-fit connection, a form-fit connection, or the like. In such case, the device may be placed in or at an opening of the container and held in position via said attachment means. Thus, operation of the device can be made even more comfortable, as the user will not need to keep the device in position during operation.

According to an embodiment, the device may be configured as a stand-alone frothing device. The device may comprise a container for receiving the liquid to be frothed, and a lid for closing the container. The drive unit may be arranged below the container or in the lid. Likewise, the heating unit may be arranged below the container or in the lid. The frothing means is operably connectable or connected to the heating unit and the drive unit, so as to extend within the container.

According to an embodiment, the device may be configured as a portable device. In such case, aforementioned container may function as a travel mug, in which a user may froth and/or heat his beverage on-the-go. The attachment between the container and the lid, or the container and the housing may in such case be liquid tight. The device may be battery operated.

According to claim <NUM>, there is provided a coffee machine, comprising means for making coffee and a device for frothing milk according to any embodiment of the first aspect.

These and other aspects of the present invention will become apparent from and elucidated with reference to the embodiments described hereinafter.

<FIG> show in schematic perspective view two exemplary embodiments of a device <NUM> for frothing a liquid, more particularly a beverage, e.g. milk. In these exemplary embodiments, device <NUM> is provided as a handheld frothing device. It comprises a housing <NUM> formed as a handle, to be held in the hand of a user. The device further comprises a drive unit <NUM> and a heating unit <NUM> that are both accommodated in the housing <NUM>, a frothing means <NUM> and a rod <NUM> that operably connects the frothing means <NUM> to the drive unit <NUM> and the heating unit <NUM>.

The drive unit <NUM> is arranged to rotate the frothing means <NUM>. In alternative embodiments (not shown), the drive unit <NUM> may be arranged to translate the frothing means, or to rotate and translate the frothing means. The drive unit <NUM> may for instance comprise an electric motor.

The heating unit <NUM> is arranged to convert electrical energy into thermal energy or heat. The heating unit <NUM> may for instance be a so-called cartridge heater, preferably comprising a heating coil, a sheath, and an electrical connection option. The device <NUM> may further comprise a power supply (not shown), such as a battery supply or a mains power supply, for powering the drive unit <NUM> and heating unit <NUM>. Suitable converters may be provided, e.g. a voltage converter or the like.

The device <NUM> further comprises at least one electrical switch, to switch on/off the power supply to the drive unit <NUM> and/or the heating unit <NUM>. In the illustrated embodiment, the switch is arranged at an upper side of the housing <NUM>. In alternative embodiments, the switch may be arranged at any other suitable location. The switch may be configured to switch on and/or off both units <NUM>, <NUM> simultaneously. Alternatively, one or more further switches may be provided, to allow independent switching of the drive unit <NUM> and the heating unit <NUM>. Alternatively, at least one of the two units <NUM>, <NUM> may be switched on and/or off with a time delay after actuation of the switch, e.g. via an interposed relay or the like, whereas the other unit <NUM>, <NUM> may switch on and/or off immediately.

The frothing means <NUM> is arranged to froth and heat a liquid. During operation, the frothing means <NUM> may be immersed in a volume of liquid to be frothed and/or heated. This liquid may be placed in a suitable container (not shown). The frothing means <NUM> has a total contact surface area of at least <NUM><NUM>. As will be explained below, with such total contact surface area sufficient heat can be transferred to heat a liquid volume between <NUM> and <NUM> to an acceptable temperature at an acceptable speed.

The frothing means <NUM> is operably connected or connectable to the drive unit <NUM> and the heating unit <NUM> via rod <NUM>. The rod <NUM> may, for example, be formed from a metal material, such as aluminum, steel, stainless steel, any alloy thereof, or the like. Optionally, rod <NUM> may be made of a material with comparatively good thermal conductivity. At a first longitudinal end, rod <NUM> may be detachably or non-detachably connected to drive unit <NUM>, wherein a detachable connection can be designed, for example, as a plug connection, screw connection, bayonet connection or the like. According to <FIG>, the first longitudinal end of rod <NUM> extends into housing <NUM> where it is connected to drive unit <NUM>. Further, in at least some embodiments, rod <NUM> may be a structural part of the heating unit <NUM>, wherein it may be heated directly. Alternatively, rod <NUM> may be hollow. In such case, the heating unit <NUM> may extend at least partly inside the rod <NUM>. Optionally, a movable section of rod <NUM> and/or heating unit <NUM> may rotate with drive unit <NUM> and may be connected to a stationary section of rod <NUM> and/or heating unit <NUM> via a suitable coupling, j oint, etc..

According to <FIG>, the frothing means <NUM> is arranged at a distance from the first longitudinal end of the rod <NUM>, between the first longitudinal end and a free second longitudinal end. The frothing means <NUM> extends away from an outer circumferential surface of the rod <NUM>. The frothing means <NUM> may be integrally formed with the rod <NUM> or be attached thereto via suitable attachment means, such as screws, a threaded connection, a snap-fit connection, or the like.

In the illustrated embodiment of <FIG>, the frothing means <NUM> has a plate shape. More particularly, the frothing means <NUM> comprises a fin-set with four fins <NUM>. In alternative embodiments, the number of fins <NUM> may differ, for example to increase the total contact surface area of the fin-set. The fins <NUM> comprise a recess <NUM>, which may also be referred to as a slot, aperture, or the like. The recess <NUM> extends at least partially through a flat side of the fin <NUM>. Further, the fins <NUM> have an inclined orientation with respect to a rotation axis of the frothing means <NUM>, i.e. the fins include an angle with a plane that extends perpendicular to the rotation axis of the frothing means <NUM>.

The dimensions of the individual fins <NUM> may vary. However, experiments have shown that with the following exemplary dimensions good results can be achieved for both frothing and heating. For example, the individual fin <NUM> may have a length, which may be measured from rod <NUM>, of about <NUM> to about <NUM>, preferably of about <NUM>. It may have a thickness of about <NUM> to about <NUM>, preferably of about <NUM>. It may have a minimum width, i.e. an inner diameter, measured at or near rod <NUM>, of about <NUM> to <NUM>, preferably of about <NUM>, and a maximum width, i.e. an outer diameter, measured at or near rod <NUM>, of about <NUM> to <NUM>, preferably of about <NUM>.

If the preferred ones of the above dimensions are used and, for example, four individual fins <NUM> are provided, the total contact surface area of the frothing means is about <NUM>,<NUM><NUM> resulting in a heat transfer rate of about <NUM> W. An exemplary rotation speed of drive unit <NUM> and/or rod <NUM> and/or the frothing means <NUM> may be set between about <NUM> rpm or <NUM>,<NUM><NUM>/s and about <NUM> rpm or <NUM><NUM>/s, preferably to about <NUM> rpm or <NUM>,<NUM><NUM>/s. An exemplary temperature of heating unit <NUM> may be set to <NUM>, and an exemplary heat transfer coefficient may be <NUM> W/m<NUM>. An exemplary thermal conductivity of the individual fin in case of aluminum may be <NUM> W/m. These exemplary dimensions and parameters may allow, for example, heating about <NUM> of milk from an initial temperature of about <NUM>° C to a final temperature of about <NUM>° C within a maximum frothing time of <NUM> minutes. Of course, the above dimensions and/or parameters may be changed if, for example, the above temperatures, the volume of the milk to be heated etc. have different values. <FIG> shows a further embodiment of a device <NUM> according to the invention. This device differs from the one shown in <FIG> in that the frothing means <NUM> has several fin-sets, more particularly four fin sets, with each fin set having four fins <NUM> (similar to the single fin-set illustrated in <FIG>). In the illustrated embodiment, the fin-sets are identical, and spaced apart along the length of the rod <NUM> with identical spacings. In alternative embodiments, the fin-sets and/or the spacings between individual fin-sets may vary. Since, according to this embodiment, the total contact surface area of the frothing means <NUM> can be increased by using more than one fin-sets, either the individual fins <NUM> can have smaller dimensions, or the heating time can be reduced, particularly compared to that described above.

<FIG> shows a further exemplary embodiment of a device <NUM>. In this embodiment, the device <NUM> is provided as a stand-alone frothing device. In this embodiment, the housing <NUM> is adapted to form a lid for a container <NUM>. The housing <NUM> is provided with attachment means <NUM>, here an outer thread <NUM> that may cooperate with an inner thread provided in the liquid container <NUM>. The liquid container <NUM> may for instance be formed from metal, or a suitable plastic material.

The frothing means <NUM> could be similar to those shown in <FIG>, but in the illustrated embodiment, comprises a set of disc shaped fins <NUM>, more particularly <NUM> disc shaped fins <NUM>, that are spaced apart along the length of the rod <NUM>. Portions of the discs <NUM> have been bend downward, to create recesses <NUM> and help generating turbulence during use. The dimensions of the discs <NUM> may be similar to those described above. Each disc <NUM> may have a contact surface area of at least <NUM><NUM> so that the total contact surface area is at least <NUM><NUM>.

It is noted that the individual frothing means <NUM> may be detachably attached to rod <NUM> and/or to an adjacent one of the frothing means <NUM>.

In functional terms, drive unit <NUM> and heating unit <NUM> as shown in <FIG> may at least largely correspond to that of the embodiments described with reference to <FIG>. Alternatively, in at least some embodiments, heating unit <NUM> may comprise an induction heating unit <NUM>, adapted to inductively heat at least e.g. rod <NUM> or any similar element suitable for holding frothing means <NUM>. For example, induction heating unit <NUM> may comprise an electromagnet and an electronic oscillator that passes a high-frequency alternating current through the electromagnet. The alternating magnetic field penetrates e.g. rod <NUM> generating electric currents inside. The electric currents flowing through the resistance of the material of e.g. rod <NUM>, which may preferably be a suitable metal material, heat it. By way of example, as indicated in <FIG>, rod <NUM> may be at least partially surrounded by induction heating unit <NUM> and/or may be guided through it.

In <FIG>, the drive unit <NUM> is illustrated to be arranged in the housing <NUM>, i.e. in the lid of the device. It is operably connected to the frothing means via the same rod <NUM> as the heating unit <NUM>. In alternative embodiments, the drive unit <NUM> may be operably connected to the frothing means <NUM> via a different mechanical connection. In yet other embodiments, the drive unit <NUM> may be operably connected to the frothing means <NUM> in a contactless way. Driving of the frothing means <NUM> may then for instance be done by having the drive unit <NUM> generate an alternating magnetic field, e.g. by rotating a magnet above or below the frothing means <NUM> and by providing the frothing means <NUM> with a ferromagnetic part. In such case, the drive unit <NUM> may be arranged inside the housing <NUM>, as shown, or outside the housing, e.g. below the bottom of the container <NUM>. The frothing means <NUM> may be rotatably mounted in the container <NUM>, e.g. on the rod <NUM> or any other suitable support structure.

In at least some embodiments, device <NUM> may further comprise an electronic unit <NUM>. Although the electronic unit <NUM> is described here only by reference to <FIG>, it may also be provided in the same or a similar way in the embodiments according to <FIG>. Further, the term "electronic" may include electromechanical components. The electronic unit <NUM> may be adapted to control at least one parameter that is selected from: heating power of heating unit <NUM>, duty cycle of heating unit <NUM>, speed of drive unit <NUM>, duty cycle of drive unit <NUM> etc. Some of the above parameters may be controlled based on a timer, an automatic switch-off function, or the like. In at least some embodiments, electronic unit <NUM> may comprise one or more of a power electronics, one or more sensors, such as a temperature sensor, speed sensor, or the like, one or more actuators, such as a switch, a relay, or the like, adapted to actuate e.g. drive unit <NUM>, heating unit <NUM> etc., control electronics, comprising e.g. a control program, means for obtaining input parameter of the sensors or the like, means to output control signals to e.g. drive unit <NUM>, heating unit <NUM>, a display, an indicator light, and a microprocessor or the like.

Further, in at least some embodiments, device <NUM> may further comprise a user interface <NUM>. Although user interface <NUM> is described here only by reference to <FIG>, it may also be provided in the same or a similar way in the embodiments according to <FIG>. For example, user interface <NUM> may be adapted, for example, to transfer user input to device <NUM>, e.g. chosen program, the desired temperature, rotation speed etc. Further, user interface <NUM> may comprise a display, adapted to display functional parameters, like program steps, warning message etc., wherein the term "display" may also include indicator lights. Preferably, user interface <NUM> is operatively connected to at least electronic unit <NUM> and/or drive unit <NUM> and/or heating unit <NUM>.

<FIG> shows in schematic view an exemplary coffee machine <NUM> and a device <NUM>, which may be an integral component of the coffee machine <NUM>. The latter may be any type of coffee machine, such as an espresso machine, a drip filter coffee maker, a capsule or pod coffee machine, or the like, and may be of a manual, semi-automatic or full-automatic type. It is noted that although <FIG> shows as an example the embodiment of device <NUM> according to <FIG>, the other embodiments according to <FIG> may also be implemented. Further, since coffee machines of different types are generally known, they are not described in detail here. An exemplary coffee machine <NUM> may comprise, for example, one or more of the following means of preparing coffee: a container or holding mechanism for coffee powder, coffee beans, coffee capsules, coffee pads or the like, a grinder, a water container, a water pump, etc. The coffee machine <NUM> may comprise an electronic unit, electronic control unit or the like, and/or a user interface, a power supply, which may at least partially replace the corresponding components of device <NUM> or interact with it. As indicated in <FIG>, device <NUM> may be arranged within a housing of the coffee machine <NUM> or be detachably connected thereto.

Claim 1:
A device (<NUM>) for frothing milk, comprising:
a drive unit (<NUM>),
a heating unit (<NUM>), and
a frothing means (<NUM>), wherein the frothing means (<NUM>) is operably connected or connectable to:
the drive unit (<NUM>) for being moved by said drive unit (<NUM>) to froth milk, and
the heating unit (<NUM>) to transfer thermal energy, e.g. heat, from said heating unit (<NUM>) to the frothing means (<NUM>) for transfer of thermal energy to the milk during frothing thereof, characterized in that the frothing means (<NUM>) comprises a total contact surface area of at least <NUM><NUM>.