WO2011110870A1

WO2011110870A1 - Milk frothing device

Info

Publication number: WO2011110870A1
Application number: PCT/GB2011/050492
Authority: WO
Inventors: Rene Shum; Gary Lane
Original assignee: Green Lane Products Limited
Priority date: 2010-03-12
Filing date: 2011-03-14
Publication date: 2011-09-15
Also published as: GB201216957D0; GB201004136D0; GB2490856A

Abstract

A method of making frothed milk comprises subjecting warm milk to a first stage of whisking using a whisk operated at a first speed, followed by subjecting the warm milk to a second stage of whisking using the whisk operated at a second, slower, speed.

Description

MILK FROTHING DEVICE

The present invention relates to a device for frothing milk, and in particular to a milk frothing device which provides for an improved frothing process.

In recent times, warm beverages including coffee and hot chocolate have become more and more popular. Such beverages often include frothed milk. For this purpose, different types of milk frothing devices have been provided. Some have a whisk at the distal end of a rod or axle, at the proximal end of which is a housing adapted to be grasped by the user, and containing a motor and battery power source. Others provide a container for receiving the milk to be frothed as well as a drop-in whisk. It is generally warm milk which is frothed. Several of these devices also include a heater, in order to combine the heating and the frothing process.

An object of the invention is to provide an improved milk frothing apparatus and / or process; in particular a process which produces frothed milk of improved quality, especially compared with milk frothed in earlier mechanical (non-steam) methods. Improved quality may be indicated by one or more of the following indicators: smaller bubbles in the frothed milk; more even distribution of bubble sizes in the frothed milk; longer-lasting frothed milk; frothed milk which in consumer tests is generally regarded as "creamier" or "smoother".

In all apparatus to date, the characteristics of the frothing mechanism have been tuned for a very limited range of milk volume. The speed of rotation of whisks and the torque of the motors used are different for appliances using a large volume of milk from those aimed at frothing a smaller volume of milk. In attempting to invent a device which was capable of frothing a significantly variable quantity of milk, we found, unexpectedly, that a milk foaming operation in which the speed of whisking changes can offer benefits in milk froth quality.

In accordance with a first aspect of the present invention there is provided a method of making frothed milk, comprising subjecting warm milk to a first stage of whisking using a whisk operated at a first speed, followed by subjecting the warm milk to a second stage of whisking using the whisk operated at a second, slower, speed.

In accordance with a second aspect of the present invention there is provided apparatus for frothing milk, the apparatus comprising a whisk, and a driving mechanism which operates the whisk at a first speed of operation followed by a second, slower, speed of operation.

We use the words froth / frothed / frothing in this specification but the words foam / foamed / foaming can be substituted therefor. We use the word "milk" in this specification to denote pure milk and also milk-based liquids, preferably having a major weight proportion of pure milk.

A "whisk" in this specification means a device which can introduce sufficient air into milk to change the physical form of the milk. The term "whisk" does not imply any other limitation, for example a limitation to any particular physical construction.

The apparatus may be used to carry out the method. The method may be carried out using the apparatus.

The following definitions may be applied to both the method of the first aspect and the apparatus of the second aspect unless the context or an express statement demands otherwise. According to preferred embodiments of the invention the milk frothing apparatus comprises a housing including a container for receiving the milk to be frothed, and containing a whisk, wherein the container comprises a side wall and an inclined side wall portion, wherein the inclined side wall portion is inclined with respect to the side wall. Preferably the side wall and/or the whisk are asymmetrically located within the container.

The whisk may be driven by a driving mechanism at least partly outside the container, for example by a motor, suitably connected to the whisk by a rod or axle; or by or a magnetic drive inducer, the whisk being associated with a magnetic follower. Preferably there is a bottom wall portion and the inclined side wall portion is confined by the side wall and the bottom wall portion.

Thus, in such embodiments although the whisk may cause the milk or liquid in the container, the asymmetrical arrangement of the whisk and / or the container geometry may keep the maximum level of the milk or liquid low. Further, a sufficient mixing and distribution of the milk will take place so that every portion of the milk will pass the whisk. In particular by providing the inclined side wall portion, this wall portion will compensate the level increasing effect of the rotation by the whisk, as well as the oscillation of the milk level. The inclined side wall portion together with the side wall and the bottom portion provides for a surface which is easy to clean, since no further obstacles are necessary for suppressing the oscillation of the milk within the container.

It should be noted that an inclined side wall portion is inclined with respect to a vertical side wall and a horizontal plane as well, so that the inclined wall portion may be in form of a slope or ramp. It should also be noted, that the inclined wall portion can as an alternative also be provided between a lower side wall and an upper side wall, as well as the inclined wall portion can also constitute a fully inclined bottom, wherein a bottom portion then constitutes the lowest portion in the container.

In such "container" embodiments of the invention the whisk is preferably positioned in alignment with the inclined side wall portion (horizontal alignment, when the apparatus is in its use orientation. In such embodiments of the invention the whisk may be provided at the distal end of a rod, wherein the container comprises a wall having a duct, wherein the rod extends through the duct so that the whisk is provided within the container, and a motor is provided on the other side of the wall. Preferably the wall is a bottom wall of the container. Thus, the whisk can be driven by the rod (which functions as an axle).

Depending on the arrangement, there may be a rod with the motor at one end and the whisk at the other (direct motor drive); or the rod may be interrupted by gears (provided to raise or lower the speed of the whisk relative to the speed of the motor, and / or to allow the whisk, in the container, to be detached from the motor, in a base part, for example for pouring frothed milk, or cleaning).

Alternatively there may be a magnetic drive mechanism wherein the whisk is carried by or associated with a magnetic follower, driven by a magnetic drive inducer. The magnetic follower may be outside the container and connected to the whisk by a rod passing through a said duct. Preferably however a magnetic follower is located inside the container and so no said duct is present in the container wall.

The milk may be pre-warmed or may be warmed in-situ, as frothing takes place. According to "container" embodiments of the invention, the housing further includes a heating element. Preferably the heating element is attached to at least a wall of the container; preferably to the obverse face of the wall to the milk-receiving container volume.

Thus, the heating of the milk within the container can take place at the same time as the frothing process, so that both the heating and the frothing can take place in parallel in order to improve efficiency. According to "container" embodiments of the invention, the inclined wall portion is provided off- centre. The off-centre location of the inclined wall portion serves for an improved asymmetric geometry, which reduces the oscillation of the milk or liquid in the container. The inclined wall portion is preferably flat.

The wall portion may have an inclination of about 45° ± (plus/minus) 15° with respect to a virtual horizontal plane during normal operation. Thus, oscillation of the rotating milk can be significantly reduced. The size of the inclined surface may be for example 50 % of the size of a surface of the bottom portion of the container. In other words, the amount of the surface of the bottom portion and the amount of a surface of the inclined wall surface may be in a similar dimension or may deviated from each other of up to about 20 %. In particular, the amount of the inclined wall surface may be somewhat larger than the amount of the horizontal bottom surface.

According to an exemplary embodiment of the invention, the whisk is provided off-centre of the container.

According to an exemplary embodiment of the invention, the milk frothing device further comprises a separate base unit for releasably receiving the housing, wherein the base unit is provided with a driving mechanism, wherein the driving mechanism and the container are provided with respective coupling or driving elements, which may be magnetic or mechanical, and which are adapted to be drivingly coupled together when the base unit receives the housing.

For this purpose the complete electrical connections for a power supply can be provided in the base unit, so that for an easier handling, no wired connections remain, wherein all functional couplings, e.g. electrical coupling and mechanical coupling takes place when the base unit receiving the housing.

According to the "container" embodiments of the invention, the housing may typically include the container and sub-chamber or void, the heating element in the sub-chamber or void, and preferably a first electrical coupling element and a first mechanical coupling element, with the sub-chamber or void being sealed in a dishwasher-proof manner. There may be a base unit which contains the second, matching, electrical coupling element and the second, matching, mechanical coupling element. The base unit may contain power supply equipment including a transformer if required, and the driving mechanism, and any electrical control parts, for example a CPU or PCB. A casting, molding or other sealing method can be used to establish a seal between a bottom portion and an outer portion of the housing. This permits, for example, the housing including the container and the whisk, to be put into a dishwasher, but to maintain the main electrical components as a printed circuit board and the driving mechanism outside the dishwasher, since only the interior of the housing will be contaminated with milk during normal use.

According to "container" embodiments of the invention, the container comprises a filling volume of at least 75 ml, preferably at least 100 ml. Embodiments could have a filling volume of at least 185 ml.

According to "container" embodiments of the invention, the container comprises a filling volume of not greater than 400 ml, preferably not greater than 200 ml, preferably not greater than 150 ml. In "container" embodiments the container may have markings to show the minimum and maximum quantities of milk to be added to the container.

Due to the expanded volume of the milk froth the container requires an absolute volume considerably in excess of the volume of milk that may be added to it.

According to "container" embodiments of the invention, the container comprises an absolute volume of at least 220 ml, preferably at least 500 ml.

According to "container" embodiments of the invention, the container comprises an absolute volume of not greater than 750 ml, preferably not greater than 500 ml.

Thus, frothed milk can be prepared for a plurality of beverages simultaneously. It should be noted that the filling volume of the container is defined as the volume of milk which can be received without slopping during normal operation of the milk frothing apparatus. In other words, the filling volume may also be increased by only keeping low the liquid level in normal use. The absolute volume is the total volume of the container i.e. the maximum volume of liquid which the container can hold.

In all preferred embodiments of the invention the whisk is preferably of a filamentary form, preferably a metallic or plastics filamentary form sufficiently robust to withstand repeated whisking operations in warm milk. A preferred form of whisk is a toroidal body provided by taking a helix, bending it, and holding it in a toroidal shape, for example by joining it, end-to- end and/or using a retaining ring. Preferably such a whisk, when mounted to the rod or axle, is mounted centrally and perpendicularly so as to co-rotate with the rod, without giving rise to torsional forces or imbalance.

In all embodiments of the invention the whisk preferably has an overall plan area (footprint) not exceeding 20 cm², preferably not exceeding 10 cm², and most preferably in the range of from 3 to 8 cm².

In all embodiments of the invention the whisk may be removable, either with or without the rod, for separate cleaning.

In all embodiments of the invention the first stage of whisking is preferably effected for a period in the range 20 to 180 seconds, preferably 30 to 90 seconds

In all embodiments of the invention the second stage of whisking is preferably effected for a period in the range 5 to 80 seconds, preferably in the range 10 to 50 seconds.

Preferably the first stage takes longer than the second stage.

In all embodiments of the invention the second stage preferably operates the whisk at a speed which is less than 80% of the speed of the whisk in the first stage, preferably less than 60% of that speed. Most preferably the ratio of the speed of the whisk in the first and second stages is in the range 100 : 10-50, preferably 100 : 20-50.

The changes of speed may be brought about in various ways, familiar to the person skilled in the art. When a DC motor is used (as is preferred for the driving mechanism), the voltage may be reduced using a voltage controlling means, such as a circuit on a PCB. When an AC motor is used a rheostat may be employed, or the frequency of the AC signal may be changed. With any motor the speed may be reduced by gearing means, or by braking means. With a magnetic drive the speed may be changed by altering the magnetic field strength, in any way. These matters are within the competence of the skilled person and the invention is believed not to lie in the details of how the speed reduction is achieved, but primarily in the unexpected finding that a speed reduction an an intermediate stage in the frothing of milk gives a quality improvement. In the present invention the change of speed may be effected under the control of a user, who can judge when it is desirable to reduce the speed. In such embodiments there may be a user-operated speed selector means provided on the apparatus. In alternative embodiments the speed change may be effected under the control of the apparatus (that is, without intervention by the user). For example it may be under the control of a timer, or a temperature sensor. In a preferred embodiment employing an inbuilt heater the first stage may be carried out as the milk is being heated and the second stage is carried out on milk which is no longer being heated. Suitably the termination of heating is coincident with the change of speed; and preferably these events are commonly triggered, within control means.

Embodiments of the invention provide a creamy, long-lasting, satisfying milk froth.

It is believed, without being bound by theory, that the first, faster, stage incorporates air into the milk efficiently, but that the result can be a somewhat coarse, open froth; and that the second, slower stage "chops" the bubbles, reducing the bubble size, thus producing a froth of creamier texture, and longer duration.

The requirement for a faster speed followed by a slower speed does not preclude the provision of other speeds; so long as there is a faster speed preceding (not necessarily immediately preceding) a slower speed. Preferably, however, the method involves a faster speed shortly or immediately before said slower speed, with the transition between the two being immediate or graduated, for example in steps or a continuum of decreasing speed. Preferably the faster speed, slower speed and immediate or graduated transition therebetween takes up the entire whisking process. Preferably the whisking process does not involve the delivery of steam to the milk.

Preferably, the speed at which whisking is commenced is faster than the speed at which whisking is concluded. In accordance with alternative embodiments of the invention the milk frothing apparatus comprises a rod with the whisk at its distal end and a housing at its proximal end, the housing containing a driving mechanism and a battery power source. The housing is preferably designed to fit comfortably in the hand of a user. It should be noted that the above features may also be combined, even if not explicitly described in detail. All of the above device features described may be used in the method. All of the method features described may be carried out using the apparatus.

The invention will not be described with reference to the accompanying drawings, in which: Fig. 1 illustrates milk frothing apparatus according to an exemplary embodiment of the invention having a housing and a base unit, wherein the base unit received the housing of the milk frothing device.

Fig. 2 illustrates a milk frothing device according to the embodiment of Fig. 1 , wherein the housing portion is released from the base unit of the milk frothing device.

Fig. 3 is a cross-sectional view of the embodiment of Fig. 1.

Fig. 4 shows in perspective view a second exemplary embodiment of milk frothing apparatus of the invention.

Fig. 1 illustrates a milk frothing apparatus 1 with a housing 2 resting on a base unit 3 according to a exemplary embodiment of the invention. The milk frothing apparatus 1 comprises a housing portion 2 and a base unit 3, wherein the housing portion 2 can be released from the base unit 3. The housing portion may comprise a handle 4, which may provide for an easier handling of the housing portion of the milk frothing apparatus 1. In order to maintain the heat within a container of the milk frothing device, the milk frothing device 1 can be provided with a cover 16. The cover may be provided as a transparent cover in order to monitor the frothing process within the container of the milk frothing apparatus.

The frothing process may be started with an operating button 42, which may be provided at the base unit 3 of the milk frothing apparatus 1. When pushing the operating button, there is usually cold milk in the container, and the heating process will be started e.g. synchronously to a frothing process within the container. Operation begins at a high speed and when the heater switches off (an event which may be user-determined or pre-determined or sensor controlled) operation switches to a lower speed for a further period. At the end of this period the whisk stops.

It should be noted that also for the frothing process particular sensors 18 may be provided within the housing, in order to monitor the success of the frothing process, for example by a ultrasonic sensor, which can monitor the acoustic properties within the container depending on the foam development of the frothed milk, and terminate the frothing operation if necessary. In general, however, the operation is intended to involve, as an over-riding feature, a first, faster, stage of whisking and a second, slower, stage of whisking.

Fig. 2 illustrates a milk frothing apparatus 1 as already depicted in Fig. 1 , however, in a released situation, where the housing portion 2 of the milk frothing apparatus 1 is released from a base unit. When releasing the housing portion 2 from the base unit 3, a contact 31 on the housing portion side can be released from a contact 41 on the base unit side. When providing the plug/socket 31/41 at the edge of the housing portion 2 and the edge of the base unit 3, respectively, a user can easily monitor when putting the housing portion 2 onto the base unit and to receive the correct positioning thereof. It should be noted that the plug/socket 31/41 can also be provided as a separate unit and that a separate forming of the edge of the base unit corresponding to the edge of the housing portion may be provided for providing an easier fit of housing 2 and the base unit 3. When releasing the housing portion 2 from the base unit 3, a frothing process and a heating process may be stopped automatically. Electronic elements in the base unit may detect the releasing of the housing portion, in order to interrupt the circuit to provide the heater with electrical current. A base unit may be provided with an electric lead and connector plug (not shown) to permit connection to the mains electricity supply.

Fig. 3 illustrates the same milk frothing apparatus 1 having a housing portion 2 and a base unit 3. The housing portion 2 may be released from the base unit 3 in order to provide an easier handling of the housing portion during serving milk (or other frothed beverages) in the container 10. The container 10 in the illustrated embodiment comprises a cylindrical side wall portion 1 1 , an inclined wall portion 12 and a bottom portion 13. However, it should be noted that in particular the side wall portion 1 1 may also be of a different shape and does not have to be formed in a cylindrical shape. In the shown embodiment, a duct 14 is provided in the bottom portion 13 of the container 10 in order to provide a duct for a rod 22 of a frothing head 20. The frothing head 20 comprises a whisk 21 , which may be provided as a circular metal ring with a coil wounded around the ring in order to provide an improved frothing process. The whisk 21 is provided at one end of the rod 22, wherein on the other end of the rod 22 there is provided a mechanical coupling element 23, for example a gear part. The mechanical coupling element 23 may engage with a corresponding mechanical coupling element 53, which of course may be a meshing gear part, of the base unit 3, when the housing 2 is received on the base unit 3. When releasing the housing portion 2 from the base unit 3, the mechanical coupling element 23 will also be released from the mechanical coupling element 53. It should be noted that even if not shown, there may also be provided some spring or resilient members, which provide for a sufficient mechanical coupling between the mechanical coupling elements 23 and 53.

The base unit 3 comprises a drive means 50, which in the present embodiment further comprises a driving mechanism, a DC motor 51 in this embodiment, and a rod 52 connected to the motor. The second mechanical coupling element 53 is mounted to the end portion of the rod 52. The housing portion 2 further comprises a first electrical coupling element 31 which correspondingly engages into a second electrical coupling element 41 of the base unit 3. This connection between the electrical coupling elements 31 and 41 provides for an electrical contact between the base unit 3 and the housing portion 2 in order to provide a heating element 30 with electrical energy. It should be noted that the electrical connection between the first electrical coupling element 31 and the heating element 30 is not shown in Fig. 3. It should be noted that a heating element may be a conventional heating element as well as a heating film or a micro wave device. The heating element may be at least partially provided at the inclined wall portion of the container 10, in order to provide a heating impact to the milk or liquid contained in the container 10. The container may be fixed to the housing portion by a press fitting or welding or soldering process at the top portion of the housing 2. It should be noted that the space between the housing 2 and the container 10 may also be filled with an insulating material in order to avoid a heat loss from the inside of the container to the outside. The housing portion 2 may also comprise a cover 16, which may be sealed by a circumferential seal 17 to the container 10.

The base unit 3 may comprise a frame construction 72, which may be covered by an outer shell 71 , which may for example be provided as a design surface of the base unit.

Further, inside the base unit 3 there may also be provided a printed circuit board 60, which may include a control circuit for controlling the driving means as well as the heating element. Onto the printed circuit board, also electronics can be provided which control the two-stage speed of operation (fast, then slow), particular sensors (not shown) which may control a sufficient heating process to not overheat the milk to be foamed; and sensors 18 which may monitor a sufficient foaming process. Foaming sensors may for example be ultrasonic sensors measuring the acoustic properties of the foamed milk, which will substantially change between a foamed and an unfoamed condition, since foamed or frothed milk has a very much higher acoustic damping coefficient compared to unfrothed milk. However, as an alternative, also visual sensors may be provided in order to monitor the filling level of the container 10. Frothed milk has a larger volume than unfrothed milk, so that based on the filling level of the container, a frothing process may be monitored. Further, a frothing process can be stopped when filling too much milk into the container 10, so that the milk frothing device can also be operated with an open cover, without the risk that the foamed milk will slop out of the container 10. For connecting particular sensors to the container 10 for monitoring the frothing process, further contacts, plugs and sockets may be provided between the housing 2 and the base unit 3, although not shown.

However, the acoustic damping of the frothed milk in the container can also be measured from the base unit, since also the acoustic properties of the environment of the base unit will change, when the milk in the container 10 will change from an unfrothed to a frothed condition.

In an alternative embodiment the heater may be ring-shaped and mounted around the rod. In an alternative embodiment the duct for the rod may be provided through the inclined wall portion.

In an alternative embodiment the inclined wall portion may extend from one side of the container to the other, that is, there is no bottom portion 13.

Each such embodiment employs the principle of fast speed of whisking followed immediately by slow speed of whisking, achieved by reducing the voltage at which the motor is operated by 33% (for example from 15V to 10V).

A second embodiment of the invention is described with reference to Fig. 4. This embodiment has a rod 100 in the form of an axle. At the distal end of the rod is a toroidal whisk 102 (as described above for the first embodiment), and at the proximal end, a handle part 104 which contains a motor and a battery source. An operating button 106 has three positions: off, high speed and low speed. In this embodiment the operation is wholly under the control of the user who is advised in the operating instructions to commence frothing at high speed, and then, when he judges that sufficient air has been incorporated, to switch to low speed to order to improve the texture and creaminess of the froth.

It should be noted that the term "comprising" does not exclude other elements or steps and the "a" or "an" does not exclude a plurality. Also elements described in this association with different embodiments may be combined.

Claims

Claims:

1. A method of making frothed milk, comprising subjecting warm milk to a first stage of whisking using a whisk operated at a first speed, followed by subjecting the warm milk to a second stage of whisking using the whisk operated at a second, slower, speed.

2. A method according to claim 1 wherein the first stage of whisking is effected for a period in the range of from 20 to 180 seconds and the second stage of whisking is effected for a period in the range of from 5 to 80 seconds.

3. A method according to claim 1 or 2 wherein the second stage operates the whisk at a speed which is less than 80% of the speed of the whisk in the first stage.

4. A method as claimed in any preceding claim wherein the milk is heated during the first stage but not during the second stage.

5. Apparatus for frothing milk, the apparatus comprising a whisk, and driving mechanism which operates the whisk at a first speed of operation followed by a second, slower, speed of operation.

6. Apparatus according to claim 5, comprising a container for receiving milk to be frothed, the container having a whisk to froth milk in the container.

7. Apparatus according to claim 6, wherein the whisk is mounted for rotation at the bottom region of the container.

8. Apparatus according to claim 7, wherein the apparatus comprises a housing which comprises the container and a base unit beneath the container, the base unit containing a driving mechanism in the form of an electric motor or magnetic drive.

9. Apparatus according to any of claims 6 to 8 wherein the container comprises a side wall and an inclined side wall portion, wherein the inclined side wall portion is inclined with respect to the side wall.

10. Apparatus according to any of claims 6 to 9 wherein the side wall and/or the whisk are asymmetrically located within the container.

1 1. Apparatus according to claim 9 or 10, wherein the container has bottom wall portion and the inclined side wall portion is confined by the side wall and the bottom wall portion.

12. Apparatus according to any of claims 6 to 1 1 , comprising heater means located so as to warm milk in the container, preferably attached to a wall of the container; preferably to the obverse face of the wall to the milk-receiving container volume.

13. Apparatus according to any of claims 6 to 12, wherein the apparatus comprises a DC motor to drive the whisk, and the speed of the whisk is reduced by reducing the supply voltage using a voltage controlling means.

14. Apparatus according to claim 5, wherein the milk frothing apparatus comprises a rod with the whisk at its distal end and a housing at its proximal end, the housing containing a driving mechanism and a battery power source.

15. A method according to any of claims 1 to 5, carried out using apparatus according to any of claims 6 to 14.