Patent Description:
Milk is usually foamed by means of steam or via mechanical means, such as e.g. coiled stirrers. In the hotel, restaurant and catering trade, steam is the method used most often. A steam generator produces steam, which is blown into a jug filled with milk via a steam pipe. Producing foamed milk of the correct texture, temperature and consistency requires extensive experience and expertise of the barista.

Devices are known attempting to partly emulate the knowledge and expertise of the barista. It is known from e.g. <CIT>, to incorporate a temperature probe in the steam pipe. A control unit, connected to the temperature probe, controls the supply of steam on the basis of the desired type of foam and stops the supply when the desired final temperature is reached. Since the temperature probe protrudes from the steam pipe, such a device is more difficult to clean.

<CIT> describes a device in which the steam pipe is arranged so as to be moveable. The device may be provided with a programme containing a movement path for the steam pipe which depends of the desired milk foam. A temperature sensor may be provided in order to select an optimum movement programme for the steam pipe on the basis of the temperature of the milk to be foamed. <CIT> provides a float on the steam pipe in order to ensure a constant distance between the end of the steam pipe and the liquid level. Such a float not only results in a complicated construction, because the steam pipe has to be arranged in a sprung manner. The float also forms an obstacle when cleaning the appliance. On the other hand, <CIT> provides an active movement element for actuating a movement of the steam pipe which element is connected to a sensor for detecting the liquid level, in which the movement of the steam pipe is actuated depending on the measured values of this sensor. Other milk frothers with moveable steam pipes are described in <CIT>, <CIT>, <CIT> and <CIT>.

In order to obtain milk foam of good quality using the abovementioned devices, it is important to correctly determine the liquid level. However, air bubbles or other contaminants are often present on the liquid surface of milk and prevent accurate measurement, as a result of which an appliance cannot function properly and cannot deliver foam of consistent quality.

It is an aim of the present invention to provide a device allowing improved treatment of the liquids. An aim of the invention is e.g. to produce better milk foam, irrespective of who is operating the device. Better milk foam could mean foam with smaller air bubbles, such as microbubbles.

It is an aim of the invention to provide an abovementioned device which is able to correctly determine the liquid level of the food liquid to be treated.

According to the invention, a device and an assembly for treating food liquids, including milk, is therefore provided, as set out in the attached claims.

Embodiments with additional advantages are described in the dependent claims.

Aspects of the invention will be explained below with reference to the following figures.

In the present description, reference is made to milk as a food liquid. It should be noted that devices according to the invention are not limited in their use to only milk, but that other food liquids, in particular drinks, may also be treated. These food liquids are preferably liquids, emulsions or suspensions comprising milk, such as drinking chocolate, but this is by no means limiting. Soya milk or other drinks can also be treated using devices according to the invention.

With reference to <FIG>, the device <NUM> comprises a housing formed by a base part <NUM> and a tower part <NUM>. The device <NUM> rests on a surface by means of the base part <NUM>. To this end, base part <NUM> has an underside <NUM> which is provided with supporting feet <NUM>. The tower part <NUM> is arranged at one end of the base part <NUM> and preferably projects vertically from the base part <NUM>. A front side <NUM> of the tower part is turned towards the base part <NUM>.

The base part has a top side <NUM>, on which a platform <NUM> is provided. Platform <NUM> forms a support on which a receptacle <NUM> (see <FIG>) containing the liquid to be treated (milk) is placed.

In the housing of the tower part <NUM>, a preferably vertically extending recess <NUM> is arranged at its front side <NUM>. A steam pipe <NUM>, better known as a 'steam lance', protrudes from the recess <NUM>. A hole <NUM> is also provided in the housing, preferably below the recess <NUM>. A temperature sensor <NUM> (<FIG>) is provided in the hole <NUM>.

The device <NUM> furthermore preferably comprises a user interface <NUM> which makes it possible to operate the device. User interface <NUM> may comprise, e.g. a screen, such as a touch screen, or a number of operating buttons, or a combination of both. Alternatively, the user interface <NUM> may be provided on an (external) apparatus separate from the device <NUM>, such as a smart phone provided with a suitable application. In such a case, the external apparatus and the device <NUM> will be configured to communicate with one another.

Referring to <FIG>, the device <NUM> comprises a driving device <NUM>, such as e.g. a linear slide, which is arranged in the housing at the location of the recess <NUM>. The steam pipe <NUM> is attached to the driving device <NUM>. The driving device <NUM> enables a movement of the steam pipe along the recess <NUM>. As is illustrated in the figures, this movement is preferably, but not necessarily, a linear, preferably vertical, movement.

Driving device <NUM> ensures that the steam pipe <NUM> can preferably move up and down with respect to the platform <NUM>. If a milk jug <NUM> is placed on the platform <NUM>, the driving device makes it possible to move the end <NUM> (the pipe nozzle) of the steam pipe <NUM> into the milk jug <NUM>.

A control unit <NUM>, which is connected to driving device <NUM>, takes care of the control thereof, as will be described below.

The steam pipe <NUM> is internally (inside the housing) connected to a steam conduit <NUM> which is able to follow the upward and downward movement of the pipe <NUM>. A valve <NUM> is preferably provided in the steam conduit in order to start and stop the supply of steam. If desired, valve <NUM> may regulate the flow of the steam. Steam conduit <NUM> is provided with a connecting port <NUM> for connecting to a steam generator. The steam generator, which is not shown in the figures, may be an external generator and consequently not be part of device <NUM>. Alternatively, the steam generator may be incorporated in the device <NUM>.

The valve <NUM> is preferably connected to the control unit <NUM>, so that it can be actuated by the control unit.

According to the invention, liquids present in the jug <NUM> are treated by blowing steam through the liquid via steam pipe <NUM>. Under certain circumstances, blowing steam through the liquid may result in air being added to the liquid. For example in the case of milk, the steam which is blown into the milk will, under suitable circumstances, generate a foam on the liquid surface. The steam may cause the liquid to be heated up, optionally in combination with foaming.

According to aspects of the invention, the initial position of the pipe nozzle <NUM> in the liquid has to be determined accurately in order to ensure good foaming (or the absence thereof). The inventors noticed that an optical measurement of the liquid level in the milk jug <NUM> does not yield reliable results. The milk surface often contains air bubbles or may be contaminated, frequently resulting in incorrect measurements.

According to aspects of the invention, the liquid level in the milk jug <NUM> is determined by measuring the mass (weight) of the liquid in the milk jug <NUM>. On the basis of the specific weight of the liquid, the geometry of the milk jug <NUM>, and optionally the temperature of the liquid, the liquid level can easily be determined based on the mass. Such a calculation results in a determination of the level which is independent from the state of the liquid surface and is consequently always reliable.

To this end, the device comprises means for determining the liquid mass. These means, which are preferably formed by a weighing device <NUM>, are preferably coupled to the platform <NUM>, and configured to determine the mass, which rests on platform <NUM>. Weighing device <NUM> is also connected to the control unit <NUM>. Determining the liquid level from the weight is carried out by control unit <NUM>. To this end, the control unit <NUM> advantageously comprises a readable memory, containing e.g. a list with corresponding values between liquid weight and liquid level. Alternatively, the control unit <NUM> may be provided with parameters in order to determine the liquid level from the weight on the basis of the specific weight of the liquid, the geometry of the milk jug <NUM> (e.g. a diameter), and optionally the temperature of the liquid.

Advantageously, the milk jug <NUM> is supplied with the device <NUM>, so that the calibration of the weighing device <NUM> can be carried out in the factory.

The temperature sensor <NUM> is preferably arranged in the hole <NUM>, so that it faces the milk jug <NUM>. The temperature sensor is preferably an infra-red sensor, and is configured to measure the temperature of the wall of the milk jug <NUM>. A suitable sensor is a sensor from the PyroCouple™ series, available from Calex Electronics Limited, United Kingdom. If the milk jug <NUM> is made from a highly thermally conductive material, such as a metal, preferably stainless steel, then the temperature of the wall, which is preferably a single wall, forms a good approximation of the temperature of the liquid (milk) in the jug <NUM>.

Advantageously, it is ensured that the milk jug <NUM> on the platform <NUM> always assumes the same orientation with respect to the device <NUM>. This can be achieved by means of the holder <NUM>. Referring to <FIG>, the holder <NUM> comprises an upright wall <NUM> and a bottom <NUM>. The wall <NUM> and bottom <NUM> delimit an internal space which is configured to accommodate the jug <NUM>, so that the jug can be placed in the holder <NUM>. Holder <NUM> is advantageously configured to be arranged on the platform <NUM> in a removable manner. This facilitates cleaning.

The underside <NUM> of the holder <NUM> on one side and the device <NUM>, preferably the platform <NUM>, on the other side are advantageously provided with corresponding means to place the holder on the platform <NUM> at a well-defined orientation. These means may, for example, be formed by a tooth and groove or a click-fit connection. These means are able to ensure that the jug <NUM> is placed in a correct position and/or orientation with respect to the device.

The term orientation refers to an angular orientation about a vertical axis.

Additionally or alternatively, holder <NUM> is advantageously provided with means to arrange the milk jug <NUM> at a well-defined orientation with respect to the holder. For example, the holder <NUM> may have a recess <NUM> in the wall <NUM> which is configured to cooperate with the milk jug <NUM>, in particular the handle <NUM>, so that the milk jug <NUM> only fits into the holder <NUM> when the handle <NUM> is introduced into recess <NUM>. Other ways, for example by using jugs <NUM> having a specific design, so that the holder and the jug comprise corresponding cooperating means are also possible.

Positioning the milk jug <NUM> at a well-defined orientation offers the advantage that the temperature sensor <NUM> will always measure the jug <NUM> at the same location on the wall of the jug <NUM>, thus producing repeatable results. Advantageously, the milk jug is provided with a surface finish desired for measurement, at least at the location of temperature measurement, such as e.g. a matt surface, which may be obtained by sand-blasting. Advantageously, the surface of the milk jug <NUM> is not reflective.

The milk jug <NUM> preferably comprises a pouring spout <NUM>. When determining the orientation of the milk jug <NUM> with respect to the device, the pouring spout <NUM> is advantageously arranged in such a manner that it is turned towards the steam pipe <NUM>. Such an arrangement allows the steam pipe <NUM> to be inserted deeper into the jug <NUM>.

The holder <NUM> may be configured to receive jugs <NUM> of different sizes and/or shapes. In this case, detection of the type may be effected manually, through input via the user interface <NUM>, or automatically, via suitable sensors, such as e.g. an RFID tag or RFID chip incorporated in the jug <NUM>, which can be read by a receiver connected to the control unit <NUM>, or even via the weighing device <NUM> by determining the empty weight.

Advantageously, the control unit <NUM> is provided with a programme code for performing one or more treatment programmes for treating the liquids, e.g. for obtaining different grades of milk foam, or for treating different types of liquids. Advantageously, these programmes can be selected via the user interface <NUM>.

For at least one of these programmes, the control unit <NUM> advantageously comprises a minimum and/or a maximum threshold value for the liquid level in the jug <NUM> as a prerequisite for starting the programme. If the liquid level determined by the weighing device <NUM> is lower than the minimum and/or higher than the maximum, the control unit <NUM> will not start the desired programme. This ensures that the correct liquid mass is used for the selected programme.

For at least one of these programmes, the control unit <NUM> advantageously comprises a minimum and/or maximum threshold value for the temperature of the liquid as a prerequisite for starting the programme (starting temperature). If the temperature of the milk is, for example, too hot, it is not possible to obtain good foam and the control unit <NUM> will not start the desired programme. It is possible to carry out a check for the sake of food safety by providing a maximum threshold value for the starting temperature. According to food safety guidelines, dairy products have to be kept refrigerated and selecting a maximum threshold value for the starting temperature may ensure that the appliance does not start if the milk is too warm.

For at least one of these programmes, the control unit <NUM> advantageously comprises a final temperature of the liquid which is to be reached. Once this final temperature is reached, the programme will be stopped. The final temperature should not be excessively high in order to prevent the risk of the user burning himself. A suitable final temperature may be between <NUM> and <NUM>. <NUM> is a suitable final temperature.

The driving device <NUM> and/or the control unit <NUM> may advantageously be configured to perform the relative movement between steam pipe <NUM> and jug <NUM> at a well-defined speed.

A treatment programme for the liquid may comprise a preprogrammed movement path for the steam pipe <NUM>. This movement path is advantageously parameterised on the basis of the liquid level, and optionally also on the basis of the (starting) temperature of the liquid in the jug <NUM>. Advantageously, the movement path starts from an initial position. This initial position depends on the liquid level and may be parameterised as a predetermined distance below the liquid level, as determined after weighing the jug <NUM> by weighing device <NUM>. The initial position may relate to the position of the pipe end <NUM>. The predetermined distance may be stored, e.g. in the readable memory of the control unit. Thus, it is ensured that the starting position for the movement path is always coherent with the amount of liquid in the small jug <NUM>, thus making it possible to obtain more consistent results.

The movement path advantageously comprises an upward path (upward movement) of the steam pipe <NUM> with respect to the platform <NUM>, during the supply of steam. This upward movement is advantageously carried out at a predetermined speed. The upward movement is carried out while the valve <NUM> is open. Advantageously, the control unit is configured to start the upward path from the initial position, as described above. Advantageously, the upward path is defined in the control unit by a distance to be travelled, e.g. a distance starting from the initial position. Advantageously, this distance to be travelled is smaller than the difference in height between the liquid level and the initial position of the pipe end <NUM>. The control unit may be configured to control the driving device <NUM> in such a way that the distance to be travelled is covered in a predetermined time span, as a result of which a speed of movement is set. An upward movement is useful for frothing up, because the supply of steam will suck air into the milk as a result of the Venturi effect. As a result of the upward movement, the Venturi effect will continue when the liquid level is increased due to foaming. It is also useful to perform this upward movement at a controlled speed, because this may lead to better foaming. The upward speed is advantageously determined empirically on the basis of the applied steam flow, temperature and pressure, the desired end product (e.g. type of foam) and the dimensions of the milk jug. The upward speed is advantageously selected in such a way that the pipe end <NUM> follows the amount of foam formed (level increase).

Advantageously, the speed of the relative movement between steam pipe <NUM> and the platform <NUM> is between <NUM>/s and <NUM>/s. This speed is advantageously <NUM>/s or lower, advantageously <NUM>/s or lower, advantageously <NUM>/s or lower, advantageously <NUM>/s or lower.

The movement path may additionally, or alternatively, comprise a stationary position of the steam pipe <NUM> (stationary with respect to the platform <NUM>), while the pipe nozzle <NUM> is submerged in the liquid and steam is supplied. The time span during which the steam pipe <NUM> is to remain stationary may be input in the control unit <NUM> as a parameter. The movement path may additionally, or alternatively, comprise a downward movement of the steam pipe <NUM> with respect to the platform <NUM> during the supply of steam. This downward movement is advantageously carried out at a predetermined speed.

Upward and downward movement paths and standstill of the steam pipe can be combined with each other to achieve an optimum treatment of the liquid. To this end, a movement path may comprise several sub-paths, in which case each sub-path may be an upward movement, downward movement or a standstill. The movements within each sub-path may be carried out at a constant speed. The transition between two sub-paths may be determined on the basis of the liquid temperature. All these data can be stored in the programmes of the control unit <NUM> as parameters.

Referring to <FIG>, the steam valve <NUM> may be replaced by a more extensive valve system <NUM>, which makes it possible to flush condensation water out of the steam conduit and/or to adjust the steam flow to steam pipe <NUM>. Valve system <NUM> comprises a steam inlet <NUM> which may be connected to connecting port <NUM> and furthermore with an external or incorporated steam generator <NUM>. Furthermore, the valve system <NUM> comprises a number of outlets. At least one outlet, but advantageously several outlets <NUM> and <NUM>, are connected to the steam conduit <NUM> leading to the steam pipe <NUM>. An additional outlet <NUM> is advantageously connected to a discharge <NUM> of the device <NUM>. Each of the outlets <NUM>, <NUM>, <NUM> is connected to the inlet <NUM> in a closeable manner. To this end, the valve system <NUM> comprises one or advantageously several valves which can close off the passage between inlet <NUM> and each of the outlets. There are several possible embodiments of valves that may be used, such as for example multi-way valves. In the example of <FIG>, a separate (one-way) valve <NUM>, <NUM>, <NUM>, is used to close off each outlet <NUM>, <NUM>, <NUM>, respectively. Each of these valves is connected to the inlet <NUM> via a common steam conduit <NUM>.

Each of these valves is advantageously operationally connected to control unit <NUM>, which provides the individual control for the valves <NUM>, <NUM>, <NUM>. The control unit <NUM> may provide different switch positions for the valves. In a first switch position, valves <NUM> and <NUM> are kept closed and valve <NUM> is opened (as can be seen in <FIG>), in which case steam is passed to the discharge <NUM>. In this case, the condensation water is flushed along and this condensation water is prevented from ending up, via steam pipe <NUM>, in the liquid to be treated. In a second switch position, valve <NUM> is closed and valve <NUM> is opened while valve <NUM> remains closed. In this case, steam is passed to steam pipe <NUM> via steam conduit <NUM>. Valve <NUM> advantageously makes a third switch position possible, in which valve <NUM> is opened simultaneously with valve <NUM>, as a result of which, via a common connection of both outlets <NUM> and <NUM> to steam conduit <NUM>, a greater flow of steam is passed to steam pipe <NUM>. The shown arrangement consequently makes it possible to work with two different steam flows. By extension, it is even possible to provide several steam flows. This is useful if e.g. jugs <NUM> of different sizes are used. Obviously, the valve system <NUM> makes a fourth switch position possible, in which all valves are closed.

Advantageously, the control unit <NUM> is configured to actuate the valve system <NUM> in such a way that, through suitable selection of the switch positions, a rinse is performed (first switch position) before a new treatment operation is started on a liquid in the jug <NUM> (second or third switch position). In order not to waste any time, the rinse may take place while actuating the driving device <NUM> to return the end <NUM> of steam pipe <NUM> to the initial position.

A method for treating - in particular frothing up - a food liquid - in particular milk, may comprise the steps illustrated in <FIG>. The method is advantageously performed using the above-described devices <NUM>. Beforehand, a user of the device <NUM> pours the liquid into a jug <NUM> and correctly places this jug on the platform <NUM>, as explained above. In a first step <NUM>, the jug containing the liquid is weighed on platform <NUM>, in particular by means of weighing device <NUM>. Subsequently, in step <NUM>, the liquid level in the jug <NUM> is determined on the basis of the weight, in particular in a manner as explained above. The liquid level is advantageously determined taking into account the type of liquid and/or a size of the jug. The determination of the liquid level may comprise an identification of the jug, e.g. in order for the control unit <NUM> to retrieve the correct data in relation to the jug <NUM> (e.g. selection of the correct look-up table). The liquid level defines a reference plane, on the basis of which the initial position of the end <NUM> of steam pipe <NUM> is determined, which position is preferably situated below the liquid level. In step <NUM>, whether or not the determined liquid level (or the reference plane) exceeds a predetermined (minimum and/or maximum) threshold value is checked. If, for example, too little liquid has been poured into the jug, the control unit may be configured to indicate this via e.g. user interface <NUM>, and no treatment programme will be started. Advantageously, the temperature of the liquid in the jug <NUM> is measured. In such a case, it is advantageously possible to verify whether the temperature does not exceed a predetermined threshold value. Following positive verification, the method continues with step <NUM>, in which the control unit sends instructions to drive the driving device to move steam pipe <NUM>. In this case, the end <NUM> of the steam pipe <NUM> is positioned on the reference plane. This is the initial position for performing a treatment programme. Simultaneously with this positioning, or possibly before or after, the steam conduit is advantageously rinsed in order to discharge any condensation water which may have formed, e.g. by moving valve system <NUM> into the first switch position. In step <NUM>, the steam supply through steam pipe <NUM> is opened, e.g. by moving valve system <NUM> into the second or third switch position. Finally, in step <NUM>, a movement path is carried out, as explained above. Steps <NUM> and <NUM> may take place simultaneously.

An example of a recipe to froth milk up may be as follows. A milk jug <NUM> filled with an arbitrary amount of milk is placed in the holder <NUM> on the platform <NUM>. On the touch screen <NUM>, the operator selects the programme corresponding to the desired milk foam. By means of the weight, a reference plane is calculated, corresponding to the determined liquid level of the milk in jug <NUM>. The control unit checks if sufficient milk is present (lower and upper limit for liquid level) and if the temperature is sufficiently low (via sensor <NUM>). If these criteria are met, a treatment cycle starts according to the selected programme. The control unit <NUM> actuates the driving device <NUM> to move the steam pipe <NUM> to a depth determined by parameters, below the reference plane , e.g. <NUM> to <NUM> below the liquid level. Once the steam pipe <NUM> is in the desired position, the control unit actuates the valve <NUM> to an open position. Steaming starts. At the same time, control unit <NUM> actuates the driving device <NUM> to perform an upward movement of steam pipe <NUM>. This upward movement may be determined by a predetermined speed, e.g. by causing a linear slide to travel a certain upward distance (e.g. <NUM>) in a certain time (e.g. <NUM>). After travelling this distance, the control unit keeps the driving device <NUM> in a stationary position, as a result of which the steam pipe will stand still. During this stationary standstill, the valve <NUM> may remain open, so that steaming continues until a predetermined final temperature (= process parameter of the programme) is reached. The control unit <NUM> then closes the valve <NUM> and actuates the driving device <NUM> to a starting position (limit position above), so that the steam pipe <NUM> is completely removed from the milk jug. The touch screen shows that the programme is completed and the operator can remove the jug with finished product.

The abovementioned example shows that the steam pipe is being actuated, while the platform is stationary. Obviously, it is also possible for the steam pipe to remain stationary and for the platform to move, or even a combination of both.

Claim 1:
Assembly, comprising a vessel (<NUM>) for holding a food liquid and a device (<NUM>) for treating food liquids by means of steam, wherein the device comprises:
- a platform (<NUM>) for placing the vessel (<NUM>) containing the liquid,
- a pipe (<NUM>) with an open end (<NUM>), configured to supply steam to the vessel (<NUM>),
- a driving device (<NUM>) configured to drive a relative movement between the end (<NUM>) of the pipe and the platform (<NUM>),
- a means (<NUM>) for determining a liquid level of the liquid in the vessel (<NUM>) when the vessel is arranged on the platform (<NUM>), and
- a control unit (<NUM>) operationally connected to the means (<NUM>) for determining the liquid level and to the driving device (<NUM>),
wherein the control unit (<NUM>) is configured to actuate the driving device (<NUM>) such that a relative initial position between the end (<NUM>) of the pipe and the platform (<NUM>) is assumed which is based on the liquid level,
characterised in that the means (<NUM>) for determining the liquid level comprise means for determining the weight of a liquid in the vessel, wherein the control unit is configured to determine the liquid level from the weight,
and in that the vessel (<NUM>) comprises a sensor and the device (<NUM>) comprises a receiver connected to the control unit (<NUM>) and configured to read the sensor for automatically detecting a type of the vessel.