Patent Description:
This type of milk modules is used as stand-alone units or, more commonly, are used alongside, or integrated in, machines for preparing coffee-based beverages to form therewith a multi-product preparation unit.

A milk module of the type specified above normally comprises a milk line, which extends from a liquid milk container to a beverage dispensing nozzle and comprises: a milk pump to suck the milk from the container, an air inlet to allow air to be introduced in the milk line on the suction side of the pump, an frothing device arranged downstream of the milk pump, and a heating device arranged normally between the frothing device and the beverage dispensing nozzle.

In use, a given amount of air is introduced into the milk flow sucked from the container, and the resulting milk-air mixture is supplied under pressure to the frothing device to be frothed and then, if necessary, heated by the heating device.

Commonly, the frothing device comprises a flow restriction, for example formed by a fixed nozzle or by a fixed or adjustable throttle valve. The heating device normally comprises a through-flow heater, which may be an electric heater or a heat exchanger. In other cases, the milk or milk-air mixture is heated by injecting a steam flow into the milk line.

As is known to those skilled in the art, the amount of air introduced into the milk line represents an indispensable parameter for preparing frothed beverages having in the cups high requirements from both an organoleptic and an aesthetic point of view. For this reason, recent decades have seen an evolution of the traditional systems based on an ON/OFF air control, wherein the air inlet is opened or closed by means of a solenoid valve with a fixed flow rate, depending on whether a frothed beverage is to be obtained or not, toward more sophisticated systems capable of proportionally controlling introduction of air in the milk line so that variable amounts of air can be supplied according to the beverage to be prepared.

One of the most commonly used systems for proportionally controlling the amount of air consists in sucking air from the external environment by means of the action of the milk pump and, before introducing the sucked air into the milk line, electronically adjusting the air flow rate by means of a proportional solenoid valve. Normally, the solenoid valve is controlled by an electronic control unit of the milk module according to closed-loop or open-loop control algorithms widely known in the field, based on various operating parameters, such as the type of milk, the temperature of the cold milk or of the milk-air mixture, the milk pump speed, etc..

Some systems using a proportional solenoid valve for adjusting the air flow rate are exemplarily disclosed in the following pieces of prior art:.

The aim of the present invention is to provide a milk module for preparing beverages, in particular frothed or non-frothed milk, which allows the amount of air fed to the milk line to be accurately adjusted so as to improve the organoleptic and aesthetic qualities of the beverage with respect to the prior art systems.

According to the present invention, a milk module for preparing beverages, in particular frothed or non-frothed milk is provided, as claimed in the appended claims.

The attached Figure shows a hydraulic diagram of a preferred embodiment of a milk module of the present invention.

The present invention will now be described in detail with reference to the attached figures to allow a person skilled in the art to comprehend, make and use it. Various modifications to the described embodiments will be immediately apparent to the persons skilled in the art and the generic principles described can be applied to other embodiments and applications without departing from the protective scope of the present invention, as defined in the attached claims.

In the attached Figure, reference numeral <NUM> references, as a whole, a milk module <NUM> for producing hot or cold, frothed or non-frothed milk-based beverages, starting from liquid milk of animal or plant origin.

Depending on its application, the milk module <NUM> can be configured to operate as stand-alone milk module or can be connected to one or more automatic beverage preparation machines, for example coffee machines, to form an integrated multi-product production unit.

The milk module <NUM> comprises a milk line <NUM> extending from a milk container <NUM>, preferably housed in a cooler (not shown) designed to keep the milk at a temperature between <NUM>°G and <NUM>, up to a milk dispensing nozzle <NUM> arranged in a cup filling compartment (not shown).

The milk line <NUM> comprises, in succession, a milk pump <NUM> to suck milk from the milk container <NUM>, a flow restriction <NUM> arranged on a delivery side of the milk pump <NUM>, and a milk through-flow heater <NUM>.

In a different embodiment not shown, the flow restriction <NUM> could be arranged downstream of the milk heater <NUM>.

Conveniently, the milk pump <NUM> is a rotary displacement pump, preferably a gear pump.

The flow restriction <NUM> may be formed by a fixed nozzle or by a fixed or adjustable baffle or throttle valve.

Conveniently, the milk heater <NUM> is an electric heater, preferably an electromagnetic induction heater.

In a different embodiment not shown, the milk heater <NUM> could be a heat exchanger or a steam heater to inject a steam jet directly into the milk flow or indirectly by heating a milk duct.

The milk module <NUM> further comprises an air line <NUM> extending from an air source, typically an external environment, through an air filter <NUM> and opening into the milk line <NUM> in a point thereof on the suction side of the milk pump <NUM>, so that, in use, operation of the milk pump <NUM> causes, in addition to the suction of the milk from the milk container <NUM>, also the suction of an air flow into the milk line <NUM>.

In a different embodiment, the air line <NUM> could open into a point of the milk line <NUM> on the delivery side of the milk pump <NUM>, upstream of the flow restriction <NUM>, and supplied by an air compressor.

The flow restriction <NUM> defines a localized narrowing of the cross-section of the milk line <NUM> downstream of the milk pump <NUM> such that, in use, the milk-air mixture flowing therethrough undergoes a rapid compression and a subsequent rapid expansion that transforms, according to a principle well known to those skilled in the art, the milk-air mixture into frothed milk.

The milk module <NUM> further comprises a three-way solenoid valve <NUM> at an inlet of the milk line <NUM> to selectively put the milk line <NUM> in fluidic communication with the milk container <NUM>, in a normal beverage preparation configuration, and with a water line <NUM> in a washing configuration.

The milk module <NUM> further comprises a further three-way diverter solenoid valve <NUM> downstream of the through-flow heater <NUM> to selectively put the milk line <NUM> in fluidic communication with the milk dispensing nozzle <NUM> in the beverage preparation configuration and with a wastewater container <NUM> via a discharge duct <NUM> in the washing configuration.

In order to adjust the amount of air that is introduced into the milk line <NUM>, the milk module <NUM> further comprises:.

In a different embodiment not shown, the pressure sensor <NUM> could be arranged downstream of the flow restriction <NUM> or downstream of the milk heater <NUM>.

In a further embodiment not shown, the pressure sensor <NUM>, instead of being a physical sensor arranged along the milk line <NUM>, could be a virtual sensor implemented by the electronic control unit <NUM> to estimate the pressure of the milk-air mixture downstream of the milk pump <NUM> based on an electric current absorption of the milk pump <NUM>, which should therefore be measured for this purpose via known available technologies.

To control operation of the proportional air solenoid valve <NUM>, in one embodiment the electronic control unit <NUM> is programmed to:.

In one embodiment, the target pressure profile P is constant over time to cause the proportional air solenoid valve <NUM> to be controlled so as to maintain a constant pressure of the milk-air mixture in the milk line <NUM>, downstream of the milk pump <NUM>.

In a different embodiment, the pressure profile P has a time-varying development to cause the proportional air solenoid valve <NUM> to be controlled so that the pressure of the milk-air mixture in the milk line <NUM>, downstream of the milk pump <NUM>, has a time development similar to that of the target pressure profile P.

Exemplarily, a target pressure profile P with a time-varying development could have a trend according to a broken line, formed by a plurality of substantially straight segments comprising a first segment with a first duration, in which the target pressure increases from an initial value, for example <NUM> bar, to a final value, for example <NUM> bar, in a given time interval; a second segment with a second duration, in which the target pressure remains substantially constant for a given time interval; and a third segment with a third duration, in which the target pressure returns to the initial value in a given time interval.

In a different embodiment, the electronic control unit <NUM> is programmed to store data representative of different target pressure profiles P, each of which can be conveniently associated with a respective milk-based beverage that can be produced by the milk module <NUM> and that can be selected by a user through a graphical user interface (GUI) displayed on a display of an automatic beverage preparation machine with which the milk module <NUM> is associated or in which it is integrated.

In one embodiment, the electronic control unit <NUM> is programmed to output electrical commands for the proportional air solenoid valve <NUM> by implementing, for example, a Proportional-Derivative (PD) controller.

It is understood that controllers other than the one indicated, and which those skilled in the art may deem to be suitable for the purpose, can be implemented.

In order to control operation of the proportional air solenoid valve <NUM>, the electronic control unit <NUM> is programmed:.

To compare the electrical output of the pressure sensor <NUM> with the target pressure profile P, the electronic control unit <NUM> is programmed to sample the electrical output of the pressure sensor <NUM> at a given sampling frequency, e.g., every second, and compare the samples of the electrical output of the pressure sensor <NUM> with corresponding stored values of the target pressure profile P.

After each adjustment intervention of the proportional air solenoid valve <NUM>, the electronic control unit <NUM> is programmed to wait for a pressure transition interval before checking whether a further adjustment intervention of the proportional air solenoid valve <NUM> is to be performed.

Based on what has been described, the advantages that the present invention allows to obtain may be appreciated.

In particular, the present invention allows a pressure profile of the milk-air mixture downstream of the milk pump <NUM> to be to defined and set, which is reproduced throughout the dispensing of the beverage and that enables the milk module <NUM> to produce milk-based beverages that have a high quality both organoleptically and aesthetically, namely, that contain the correct amount of milk and that the top layer of milk foam has an appropriate height and consistency.

In addition, the present invention allows the absence of milk in the milk line <NUM> downstream of the milk pump <NUM> to be identified and signaled, thus indicating that the milk container <NUM> is empty.

In addition, the present invention allows any abnormalities in the milk module to be diagnosed and signaled, for example a failure of the milk pump.

Finally, it is clear that various modifications can be made to the embodiments described and shown without thereby departing from the scope of the present invention, as claimed in the appended claims.

For example, in a different embodiment not shown, air could be introduced into the air line <NUM> by a compressed air source, for example an air compressor, electronically controlled by the electronic control unit <NUM>. In this embodiment, the proportional air solenoid valve <NUM> could be omitted and the amount of air introduced into the milk line <NUM> could be adjusted by means of the appropriate control of the compressed air source, in the example considered the speed of the air compressor. Alternatively, the proportional air solenoid valve <NUM> could be maintained and arranged downstream of the compressed air source to finely adjust the amount of air introduced into the milk line <NUM>.

Claim 1:
A milk module (<NUM>) for preparing hot or cold, frothed or non-frothed milk-based beverages from liquid milk;
the milk module (<NUM>) comprises a milk line (<NUM>) extending from a milk container (<NUM>) up to a milk dispensing nozzle (<NUM>); and an air line (<NUM>) extending from an air source and opens into the milk line (<NUM>);
the milk line (<NUM>) comprises a milk pump (<NUM>) to suck the milk from the milk container (<NUM>), a flow restriction (<NUM>) arranged on a delivery side of the milk pump (<NUM>), and a milk heater (<NUM>);
the milk module (<NUM>) further comprises a proportional air solenoid valve (<NUM>) arranged along the air line (<NUM>); a pressure sensor (<NUM>) to measure and output an output indicative of a pressure of the milk-air mixture in the milk line (<NUM>) downstream of the milk pump (<NUM>); and an electronic control unit (<NUM>) in communication with the pressure sensor (<NUM>) to receive the output thereof and with the proportional air solenoid valve (<NUM>) to control operation thereof;
in order to control operation of the proportional air solenoid valve (<NUM>), the electronic control unit (<NUM>) is configured to:
- store data representative of at least one target pressure profile (P) indicative of a time development of a target pressure of the milk-air mixture that is desired to be obtained in the milk line (<NUM>), downstream of the milk pump (<NUM>); and
- closed-loop control the proportional air solenoid valve (<NUM>) based on the pressure of the milk-air mixture measured by the pressure sensor (<NUM>) and the target pressure profile (P).