HK1240050B - Device for preparing frothy milk - Google Patents

Description

Equipment for preparing frothed milk

Technical Field

The present invention relates to an apparatus and a method for producing frothed milk, as well as to a coffee machine comprising such an apparatus and enabling such a method. More particularly, the present invention relates to an apparatus for frothing milk when preparing beverages containing frothed milk, such as cappuccino, latte, or the like.

Background Art

The present invention is generally applicable to liquid foods suitable for foaming, wherein foaming refers to the process of mixing air into a liquid, i.e. forming an emulsion of air in the liquid, resulting in a fine dispersion of air bubbles in the foaming liquid.

Devices for frothing and heating milk are commercially known; in fact, to produce frothed milk, the milk is usually heated by means of a steam injection.

According to a known technique, milk is placed in a container and a tube for delivering steam, called a "steam wand", is immersed in the milk held in the container, thereby forming foamed milk; this method is commonly used in commercial machines and HoReCa (short for Hotel, Restaurant, Coffee Shop) machines.

Furthermore, devices for frothing and heating milk are commercially known which mix steam with air in order to improve the foam obtained.

EP 1501398 describes a coffee machine equipped with a frothing device comprising a steam input line and an air input line, both of which enter a T-shaped manifold. The T-shaped manifold has a delivery line extending therefrom to deliver a mixture of air and steam. The air input line is connected to a compressed air source, in this case a compressor for regulating the air flow rate. The compressor must operate at a delivery pressure greater than the steam pressure to function properly. The air and steam mixture obtained from the collector is delivered directly to a container, where the milk held therein is heated and frothed.

EP 2534986 describes a coffee machine provided with a frothing device, wherein compressed air is fed to a service boiler, i.e. a boiler that generates steam and heats the water required to produce the beverage. The air-steam mixture is then conveyed to a delivery tube immersed in milk in a corresponding container.

The above solutions have the disadvantage of not providing consistent foaming results during the operation of the machine.

Summary of the Invention

Therefore, there is a need for a frothing device for frothing beverages, in particular milk, which can overcome the above-mentioned problems.

Another object of the present invention is to provide a device for heating and frothing milk that allows precise adjustment of the degree of frothing of the milk while maintaining maximum efficiency whatever the desired degree of frothing of the milk.

A further object of the invention is to provide a simple device for heating and frothing milk, which device can be easily cleaned.

Such objects are achieved by the present invention, which relates to a frothing device for frothing a beverage, in particular milk, comprising: a steam generating device; a compressed air generating device; an air-steam delivery device for delivering air and steam to the beverage; characterised in that the steam generating device and the compressed air generating device are connected to a tank for supplying steam and air, respectively, to the tank, and in that the tank is connected to the air-steam delivery device for delivering air and steam to the beverage, that is to a device for frothing milk.

Preferably, the tank is provided with a pressure sensor, which is preferably a pressure transmitter and/or a pressure switch.

However, according to other possible embodiments, other methods of detecting the pressure in the tank may be used. For example, the pressure may be detected by measuring the velocity and/or flow rate of the air and/or steam, and/or by the rotation speed of the air generating pump, etc.

In particular, it should be noted that "detected pressure" in this context refers to a pressure measurement, for example, by means of a sensor and/or a pressure estimate based on measuring other operating parameters, such as the velocity, flow rate (or a combination thereof) of the air and/or steam flow.

According to an aspect of the invention, the compressed air generating device comprises a pump connected to a tank via a pipe, the pipe being provided with at least one intercepting device to intercept the air flow, the intercepting device preferably being a flow regulator and/or a non-return valve.

In a preferred embodiment of the invention, a temperature sensor or other detection means is present for detecting the temperature of the beverage during frothing of the beverage.

According to another aspect of the invention, the device comprises interception means arranged on the connection pipe connecting the steam generating device to the tank, and on the connection pipe connecting the tank to the delivery device for delivering air and steam to the milk (or other beverage). In a preferred embodiment, the interception means is an electric valve, possibly a three-way electric valve; advantageously, at least the electric valve located on the pipe connecting the steam generating boiler to the mixing tank is a three-way electric valve provided with a drain for removing condensed water formed when the circuit is idle.

Preferably, the apparatus of the present invention further comprises a device for intercepting the air flow arranged between the air pump and the air-vapor mixing tank; such a device may comprise at least one of a flow regulator and a check valve, or both.

According to a preferred aspect of the present invention, the device comprises a control unit connected to both a compressed air generating pump and an interception device, preferably an electrovalve, both on a pipe that feeds the vapor to the tank. In one embodiment, the control unit is also connected to both a pressure sensor and the electrovalve, or to another interception device placed on a pipe that feeds the air-vapor to a delivery device for delivering the air and vapor to the milk or other beverage.

More specifically, in machines equipped with a pressure switch, the pressure switch is set to a preset pressure value, at which a "pressure reached" signal is generated. In an embodiment of the present invention, the pressure switch is connected to a control unit (CPU), and when the target pressure is reached, a signal generated thereby is sent to the control unit. This signal may be generated by switch contacts, and the control unit, typically the CPU, receives the signal and opens the electric valve.

In another embodiment of the present invention, a pressure switch is connected in series with an electrovalve for delivering the mixture to the tank; when the operating pressure of the mixing tank is reached, the pressure switch closes the switch contacts and the electrovalve is thereby electrically activated. Such an electrovalve is placed on the pipe connecting the mixing tank to the delivery device (also called a "wand") to deliver steam and air to the milk or other beverage.

According to another aspect of the invention, at least one of the tank, the steam interception device and the interception device for intercepting the air-steam flow is provided with a drain for removing condensed water. Preferably, such a drain is located in a valve placed on the pipe feeding the steam to the tank.

Another object of the present invention is to provide a machine for preparing beverages, in particular coffee beverages, comprising a frothing device as described above.

The invention also relates to a method for frothing a beverage, in particular a milk, by means of the above-mentioned device, comprising the following steps:

Steam and air are supplied to the mixing tank separately; the pressure in the tank is detected; when a preset pressure in the mixing tank has been reached, an interception device is activated to connect the tank with the above-mentioned air-steam delivery device to deliver air and steam to the beverage.

In a possible embodiment of the invention, the pressure sensor directly activates the valve, thereby delivering air and steam to the milk. When a preset pressure P1 is reached in the tank, the contacts of a pressure switch connected in series with the control of the electrovalve close, thereby opening the electrovalve and allowing the tank to be connected to the above-mentioned delivery device to deliver air and steam to the beverage.

According to a preferred aspect, the preset pressure value in the tank is comprised between 0.6 bar and 1.8 bar, preferably between 0.7 bar and 1.4 bar, more preferably between 1.1 and 1.2 bar. When the pressure switch or transmitter detects this value, the valve is opened (directly or via a control unit), thereby allowing the air-steam mixture to reach the frothing device, that is, allowing the delivery device to deliver the air-steam mixture to the milk or other beverage.

The tank size is selected based on the desired volume; preferably, the tank has a volume of at least 120 cc (cubic centimeters), and preferably between 120 cc and 260 cc. In certain embodiments, the tank has a volume between 190 and 210 cc, preferably 200 cc. It has been found that these volumes allow the air-vapor mixture to be at an optimal temperature under normal operating conditions of the machine and the foaming equipment.

As mentioned above, the device also includes a milk temperature sensor, preferably positioned alongside the air-steam delivery wand. This sensor detects the temperature of the milk near the delivery wand and transmits the detected data to a control unit, which stops delivering the frothing mixture, i.e., the air-steam mixture, to the milk once a preset temperature is reached. In a preferred embodiment, the delivery of the air-steam mixture to the milk via the corresponding device, referred to as the wand or nozzle, is stopped when the milk reaches a temperature comprised between 50°C and 80°C, preferably between 55°C and 65°C.

According to another aspect of the invention, the method provides a step of stopping the delivery of vapor to the canister while maintaining the delivery of air; for example, this step can be performed at the end of the foaming step in order to clean the tubes of the device that delivers the air-vapor mixture. In an embodiment of the invention, only air is delivered for a limited time, typically comprised between 0.1 seconds and 3 seconds.

In further aspects, the invention also relates to a data medium according to claim 18 .

The present invention provides numerous advantages over the prior art.

In fact, the air-steam mixing is significantly improved by the canister, which also allows the quantities of the two fluids to be controlled, resulting in a better quality of the frothed milk and a better homogeneity of the microbubbles forming the foam.

Furthermore, the mixing tank allows operation at a constant pressure; even if the steam boiler's operating pressure fluctuates within a range of 0.5-0.7 to 1.2-1.4 bar due to the high volume of work being performed, the pressure achieved in the mixing tank is always the set pressure. This means that even if the boiler pressure drops, the resulting foam produced by the apparatus of the present invention maintains a constant quality. Indeed, if the temperature of the steam leaving the boiler and entering the mixing tank is below 100°C and the pressure is below 1 bar, the required pressure is achieved by compensating with compressed air, and the desired milk temperature is achieved by feeding the air-steam mixture for a longer period than would be the case with high-temperature steam.

The condensate formed in the hydraulic circuit during the idle step can be completely removed, thereby providing an additional advantage.In fact, the three-way electric valve located between the boiler and the tank allows the water formed between the mixer and the boiler to be completely drained.

Compared to the previously described solution in which air is fed directly into the boiler, the device according to the invention has the advantage of being able to feed only steam when needed. In fact, several steam outlets are typically connected to the steam boiler; if a frothing circuit is provided, one of the outlets is dedicated to this purpose, while another outlet can be used to heat the beverage solely with steam, without frothing. If air is injected directly into the steam boiler, as is done in the prior art, only a mixture of steam and air is obtained from the boiler, making it impossible to heat milk without frothing it, nor to heat another beverage without frothing it.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other advantages will become apparent from the following description made with reference to the accompanying drawings, which are included for illustrative purposes and not for limitation, in which:

FIG1 is a schematic diagram of an apparatus according to the present invention.

DETAILED DESCRIPTION

1 , a frothing device 1 for frothing beverages, in particular milk, comprises a steam generating device and a compressed air generating device 3. The steam generating device is, for example, a boiler 2. In the embodiment shown, the compressed air generating device 3 comprises a pump 11 and preferably also a flow restrictor 19 upstream of the pump.

The boiler 2 is connected to the tank 6 by a pipe 5 on which is arranged a steam interception device, in the embodiment shown, a three-way electric valve 9. The valve 9 is preferably provided with a drain passage 20 to drain water formed by condensation of the steam when the device is idle.

Compressed air generating device 3, namely pump 11, is connected to tank 6 via pipe 12. A blocking device may be provided on pipe 12. In one embodiment of the present invention, the blocking device comprises a flow regulator 13 for controlling the flow rate of air to the tank. To prevent vapor from flowing along pipe 12 toward pump 11, a check valve 14 may be provided.

As shown in FIG. 1 , the present invention provides for separate feeds of air and steam to the tank 6 ; in this way, the composition of the air-steam mixture in the tank 6 and, therefore, the composition of the air-steam mixture delivered to the milk 18 to be frothed in the container 10 can be adjusted.

The tank 6 is connected to a delivery device 4 by a tube 7 for delivering the air-steam mixture to the milk 18 (or other beverage) held in the container 10. Delivery devices, also called "steam wands", are known per se in the art and comprise a tube provided with a nozzle at the end thereof; as shown in the figure, this end is immersed in the milk 18 held in the container 10.

As is known, in the coffee machine according to the illustrated embodiment, the frothed milk is at least partially removed from the container 10 to be fed to the user's cup; however, the present invention is not limited to the illustrated application, and any type of delivery device can deliver the mixture obtained in the tank 6. For example, the steam-air mixture can be fed to a frothing device including a frothing chamber (not shown) as part of the beverage production machine. An example of a frothing chamber is described in EP 2534986 with reference to Figures 4 and 5.

On the pipe 7 there is an interception device for intercepting the air-steam flow, for example a valve 8, preferably a three-way electric valve. The valve 8 is preferably provided with a discharge passage 17 which functions to discharge water formed by condensation of steam when the device is idle.

Tank 6 is preferably provided with at least one pressure sensor 10. Pressure sensor 10 can be a pressure transmitter or a pressure switch. In both cases, depending on the embodiment, the sensor generates a signal that is sent to a control unit 16, typically a CPU, to control the operation of device 1. Alternatively, the pressure switch can be electrically connected in series to electrovalve 8, preferably via its switching contacts; in this solution, the electrovalve is actuated directly by the pressure switch.

The device 1 also preferably comprises a sensor 15 for detecting the temperature of the milk 18 (or other beverage) during its frothing step. A corresponding signal is generated in a known manner and sent to a control unit 16. Temperature sensors of this type are known, commercially available and used on certain models of coffee machines.

The control unit 16 is preferably connected to at least the valve 9 and the air pump 11; in the embodiment shown, the control unit or CPU 16 is also connected to the valve 8, thereby controlling the feeding of the steam-air mixture from the tank 6 to the frothing device 4, the pressure sensor 10 and the beverage temperature sensor 15.

The control unit may also be connected to the flow regulator 13 in order to set the latter at a desired value depending on the beverage obtained.

The method according to the invention provides for feeding air and steam separately to the mixing tank 6 in order to obtain an air-steam mixture therein; at the same time, the sensor 10 detects the pressure inside the tank 6 and sends a corresponding signal to the control unit 16 or the valve 8. If the pressure has reached the desired value, the CPU 16 can operate the interception device 8, i.e., open the valve 8, to connect the tank 6 with the delivery device 4, thereby delivering the air and steam to the milk 18 in the container 10. Alternatively, as can be seen, the switching contacts of a pressure switch can be connected to the valve 8 in order to control its opening or closing.

In FIG. 1 , the line connecting the pressure switch 10 and the valve 8 is denoted by numeral 22 ; in a possible embodiment, this line preferably replaces the connection between the pressure switch 10 —CPU 16 —valve 8 .

If sensor 10 is a transmitter, the pressure value signal generated by the transmitter is compared with the pressure value stored in control unit 16; when the pressure value is within an appropriate range of pressure values, control unit 16 actuates valve 8. As can be seen, in an embodiment, sensor 10 may be a pressure switch that sends a switching signal when an appropriate preset pressure value is reached. As a result, CPU 16 can actuate valve 8.

Preferably, the preset pressure value is comprised between 0.6 bar and 1.8 bar, preferably between 0.7 bar and 1.4 bar, more preferably in the range of about 1.1-1.2 bar.

The control unit then stops the air-steam delivery at the appropriate time, or after a preset time, or when a preset temperature is reached. As described above, in an embodiment, the air pump 11 can continue to feed air even after the steam delivery is completed. In another embodiment of the present invention, air is delivered in a step other than frothing, at which time the delivery device has been pulled out of the milk in order to clean the delivery device tube by removing any milk (or beverage) and any condensation from the delivery device tube.

In a preferred embodiment, the operator interface 21 connected to the CPU includes a cycle start button. By pressing the cycle start button, the CPU 16 preferably starts both the steam electric valve 9 and the air pump 11 at the same time. When the pressure in the mixing tank 6 reaches the planned pressure P1, or when the pressure switch gives a switch signal that the pressure P1 has been reached, the control unit 16 operates the valve 8 to open, thereby allowing the mixed air and steam flow to reach the delivery device 4, the end of which is immersed in the container 10 of milk 18. In this way, milk foaming can be achieved.

In another preferred embodiment, by pressing the cycle start button on the operator interface 21, the CPU 16 preferably simultaneously activates both the steam electrovalve 9 and the air pump 11. Since the contacts of the pressure switch 10 are arranged in series with the control of the electrovalve 8, the electrovalve 8 is not activated by the CPU; when the pressure in the mixing tank 6 reaches the planned pressure P1, the pressure switch provides a switching signal indicating the pressure has been reached, thereby activating the valve 8 and allowing the mixed air and steam flow to reach the delivery device 4, the end of which is immersed in the container 10 of milk 18, to foam the milk.

The milk heating and frothing steps then take place. Next to the steam wand, a temperature probe with a transmitter connected to the CPU detects the milk temperature; upon reaching a target temperature within a range comprised between 50°C and 80°C, preferably between 55°C and 65°C, the CPU 16 closes valve 9 and electrovalve 8. In other words, the air and steam feeds are generally interdependent. In an embodiment, to allow for cleaning of the hydraulic circuit from the mixing tank 6 to the delivery device 4 at the end of the cycle, the control unit CPU can keep the air pump active and the electrovalve 8 open for a few seconds.

It should be noted that although reference has been made to exemplary embodiments in the foregoing description, the present invention may be implemented according to numerous variations. Indeed, the described embodiments are merely illustrative and are not intended to limit the scope, configuration, or application of the present invention in any way. Rather, the foregoing description should be considered as a guide for implementing at least one embodiment of the present invention; numerous modifications may be made to those described in the exemplary embodiments without departing from the scope of the present invention.

Claims (25)

1. A foaming device (1) for foaming a beverage, comprising: a steam generating device (2); a compressed air generating device (3); and an air-steam delivery device (4) for delivering air and steam to the beverage; characterized in that the steam generating device (2) and the compressed air generating device (3) are connected to a tank (6) for feeding steam and air to the tank (6) respectively, and wherein the tank is connected to the air-steam delivery device (4) for delivering air and steam to the beverage, wherein the tank is provided with a pressure sensor (10). 2. The device according to claim 1, wherein the pressure sensor (10) is selected from a pressure transmitter and a pressure switch or a combination thereof. 3. The device according to claim 1, wherein the volume of the tank is at least 120 cubic centimeters. 4. The device according to claim 1, wherein the volume of the tank is between 120 and 250 cubic centimeters. 5. The device according to any one of claims 1 to 4, characterized in that the compressed air generating device (3) includes a pump (11) connected to the tank (6) via a pipe (12), the pipe being provided with at least one of an air-vapor interception device (8) and a vapor interception device (9). 6. The device according to claim 5, wherein the air-vapor interception device (8) or vapor interception device (9) is selected from the flow regulator (13) and the check valve (14) or a combination thereof. 7. The device according to any one of claims 1 to 4, characterized in that it further comprises a temperature sensor (15) for detecting the temperature of the beverage during foaming. 8. The device according to claim 5, characterized in that it further comprises: a connecting pipe (5) for connecting the steam generating device (2) to the tank (6); another connecting pipe (7) for connecting the tank (6) to the air-steam delivery device (4), wherein the air-steam interception device (8) is arranged on the other connecting pipe (7), and the steam interception device (9) is arranged on the connecting pipe (5). 9. The device according to claim 5, characterized in that it further comprises a temperature sensor (15) for detecting the temperature of the beverage during foaming and a control unit (16) connected at least to the steam interception device (9), the pump (11) and the temperature sensor (15) of the beverage. 10. The device according to claim 9, wherein the control unit is connected to the pressure sensor (10) of the tank (6). 11. The device according to claim 5, wherein the pressure sensor (10) is connected in series with the air-vapor interception device (8) for intercepting the air-vapor mixture in order to operate the start of the air-vapor interception device (8). 12. The device according to claim 5, wherein at least one of the tank (6), the vapor interception device (9) and the air-vapor interception device (8) for intercepting the air-vapor flow is provided with a condensate drain passage (17). 13. The device according to claim 1, wherein the beverage is milk. 14. A machine for preparing beverages, characterized in that it includes a foaming device according to any one of claims 1 to 13. 15. A method for frothing a beverage using the apparatus according to any one of claims 1 to 13, the apparatus comprising: a steam generating device (2) and a compressed air generating device (3) connected to a can (6); a tube for connecting the can to an air-steam delivery device (4) to deliver air and steam to the beverage; a pressure sensor (10) or other pressure detection device for detecting pressure on the can (6); a steam interception device (9) for intercepting steam flow from the can and an air-steam interception device (8) for intercepting air-steam flow from the can, characterized in that it comprises the following steps: Steam and air are fed to the tank (6) respectively; the pressure in the tank (6) is detected; when the preset pressure in the tank (6) has been reached, the interception device is activated to connect the tank (6) to the air-steam delivery device (4) so as to deliver air and steam to the beverage (18); the delivery of steam and air is stopped. 16. The method according to claim 15, wherein the preset pressure is in the range of 0.6 bar to 1.8 bar. 17. The method according to claim 15, wherein the preset pressure is in the range of 0.7 bar to 1.4 bar. 18. The method according to claim 15, wherein the preset pressure is in the range of 1.1-1.2 bar. 19. The method according to any one of claims 15 to 18, characterized in that it includes the step of comparing a pressure value signal generated by the pressure sensor (10) with a pressure value stored in the control unit (16). 20. The method according to any one of claims 15 to 18, characterized in that it includes the following steps: when a preset temperature has been reached, detecting the temperature of the beverage (18) and stopping at least the steam delivery. 21. The method according to claim 20, wherein the preset temperature is within the range of 50°C to 80°C. 22. The method according to claim 20, wherein the preset temperature is within the range of 55°C to 65°C. 23. The method according to any one of claims 15 to 18, characterized in that it includes the step of: delivering only air at least at the end of the bubbling process in order to clean the air-vapor delivery device (4). 24. The method according to any one of claims 15 to 18, wherein the beverage is milk. 25. A non-transient data medium suitable for reading by a computer and/or logic unit (16), the medium comprising instructions that, once read by a control unit of the device according to any one of claims 1 to 13, cause the device (1) to perform the following steps: comparing a signal value with a pressure value stored in the control unit; activating the air-vapor interception device (8) and the vapor interception device (9) when a preset pressure in the can (6) has been reached to connect the can (6) to the air-vapor delivery device (4) to deliver air and vapor to the beverage (18); stopping the delivery of vapor and air.