WO2018073677A1

WO2018073677A1 - Milk frothing apparatus and beverage-making machine

Info

Publication number: WO2018073677A1
Application number: PCT/IB2017/055954
Authority: WO
Inventors: Maurizio DIAMANTI
Original assignee: Caffitaly System S.P.A.
Priority date: 2016-10-20
Filing date: 2017-09-28
Publication date: 2018-04-26
Also published as: BR112019006843B1; CN109922699A; CN109922699B; BR112019006843A2; IT201600105915A1

Abstract

This invention relates to a milk frothing apparatus (1 ) suitable for mixing milk with air and steam to obtain frothed milk. The milk frothing apparatus (1 ) comprises a frothing chamber (20) that is connected to an air feeding duct (23), to a milk feeding duct (25) and to a steam injecting nozzle (27). In use, a flow of steam in the steam injecting nozzle (27) creates a pressure drop that sucks milk and air into the frothing chamber (20), through the respective feeding ducts (23, 25), thereby mixing milk with air and steam. Positioned in the air feeding duct (23), which puts the frothing chamber (20) in communication with an air inlet opening (30), there is a non-return device (4) that is designed to allow a flow of air from the air inlet opening (30) towards the frothing chamber (20) and to stop a flow of air and/or milk towards the air inlet opening (30). The non-return device (4) comprises a sealing element (41 ), substantially disk-shaped, that has a central region (415) fixed to a support (43) and that has an annular peripheral region (417) that is intended to make contact with an annular contact element (47). The sealing element (41 ) is deformable between a first condition, in which the annular peripheral region (417) is in sealed contact with the annular contact element (47), completely closing the passage section of the air duct (23), and a second condition, in which the annular peripheral region (417) is at least partly at a distance from the annular contact element (47), leaving a passage for the air between the sealing element (41 ) and the annular contact element (47). The condition adopted by the sealing element (41 ) is linked to a difference between the pressure upstream and the pressure downstream of the sealing element (41 ).

Description

MILK FROTHING APPARATUS AND BEVERAGE-MAKING MACHINE

* * *

DESCRIPTION

This invention relates in general to the beverage-making sector. In particular, this invention relates to a milk frothing apparatus and to a beverage-making machine, for example for making a frothed milk or a cappuccino.

There are prior art milk frothing apparatuses suitable for mixing milk, steam and air to obtain a frothed milk.

According to one type of milk frothing apparatuses, which also covers this invention, a flow of steam is fed through a suitably shaped nozzle in such a way as to create a pressure drop that sucks milk and air into a frothing chamber.

A disadvantage common to many milk frothing apparatuses of that type is that, when the flow of steam is interrupted at the end of the milk frothing step, in the ducts of the apparatus a temporary step may occur with pressure imbalances such that some drops of milk are sucked up into the air feeding duct.

When they dry, the drops of milk produce deposits in the air feeding duct, in particular in the stretches that are winding or have the smallest cross- section. The build-up of such deposits over time may obstruct the air flow and therefore compromise correct operation of the milk frothing apparatus. Therefore, prior art milk frothing apparatuses require frequent cleaning to eliminate such deposits. However, it must be emphasised that, due to the small passage section of the air duct, such cleaning may be difficult or incomplete.

In this context the technical purpose which forms the basis of this invention is to provide a milk frothing apparatus that overcomes, or at least reduces, that disadvantage or that offers an alternative solution to the prior art apparatuses.

The technical purpose specified and the aims indicated are substantially achieved by a milk frothing apparatus according to claim 1 , and by a beverage-making machine according to claim 10. Particular embodiments of this invention are defined in the corresponding dependent claims.

According to one aspect of the solution proposed by this invention, the milk frothing apparatus comprises a non-return device positioned in a stretch of the air feeding duct. The non-return device is designed to allow a flow of air from the air inlet opening towards the frothing chamber and to stop a flow of air and/or milk towards the air inlet opening. That is useful for preventing milk from being sucked up at least into the parts of the air duct where deposits are most likely to form. In fact, the non-return device physically prevents the milk from going up into the air duct and may also prevent a pressure drop from occurring in the air duct relative to the regions where the milk is found at the end of the frothing step.

According to another aspect of the solution proposed by this invention, the non-return device comprises a flexible sealing element, substantially disk- shaped, having a central region fixed to a support and an annular peripheral region intended to make contact with an annular contact element. The sealing element is deformable between a first condition, in which it is in sealed contact with the annular contact element, completely closing the passage section of the air duct, and a second condition, in which its annular peripheral region is at least partly at a distance from the annular contact element, leaving a passage for the air between the sealing element and the annular contact element. Basically, the sealing element is a rigid and deformable membrane.

Specifically, the condition adopted by the sealing element is linked to a difference between the pressure acting on the first face and a pressure acting on the second face. Therefore, the sealing element spontaneously reacts to the pressure differences that are established in the air duct, in particular opening the duct for the inflow of air due to the pressure drop created by the flow of steam during the frothing step, closing at least the initial stretch of the air duct when that pressure drop is no longer present at the end of steam supplying.

The non-return device according to this invention is useful for making possible a short reaction time to the pressure variations, in this way effectively preventing milk from going up into the air duct. In fact, the pressure difference acts on substantially the whole surface of the faces of the sealing element and therefore the resulting force is proportional to the surface. In contrast, the contact between the sealing element and the annular contact element is on a small annular surface and therefore the adhesion force to be overcome in order to open the air passage is limited. Moreover, a suitable choice of materials, for example rubber (or another elastomeric material) for the sealing element and plastic for the annular contact element, is useful for reducing the possibility of the parts sticking together, as occurs in the case of non-return valves (for example of the "duckbill" type) with a rubber to rubber contact between the parts.

Furthermore, according to this invention, the region of contact between the sealing element and the annular contact element is not directly facing the emulsion chamber. Instead, it is protected by the sealing element. That is useful for substantially eliminating the risk of drops of milk being able to reach the contact region and stick together the sealing element and the annular contact element. Therefore, that configuration is advantageous for keeping the non-return device efficient and for minimising the need for maintenance.

In one embodiment, the sealing element and in particular the whole of the non-return device is part of a removable member, thereby facilitating cleaning operations.

Further features and the advantages of this invention are more apparent in the detailed description below, with reference to an example, non-limiting embodiment of a milk frothing apparatus. Reference will be made to the accompanying drawings, in which: - Figure 1 is a perspective view of a portion of a beverage-making machine comprising an apparatus according to this invention;

- Figure 2 is a first perspective cross-section view of the portion of machine of Figure 1 , in which the non-return device is not shown;

- Figure 3 is a second perspective cross-section view of the portion of machine in the figure;

- Figure 4 is a perspective view of the milk frothing apparatus of the machine of Figure 1 ;

- Figure 5 is a perspective cross-section view of the milk frothing apparatus of Figure 4, without the milk container;

- Figures 6, 7 and 8 are other cross-section views of the milk frothing apparatus of Figure 4, without the milk container;

- Figure 9 is an exploded perspective view of a removable member, including the non-return device, of the milk frothing apparatus of Figure 4; - Figure 10 is a cross-section view of the removable member of Figure 9, in which the non-return device is in a first condition;

- Figure 11 is a cross-section view of the removable member of Figure 9, in which the non-return device is in a second condition;

- Figure 12 is a bottom view of the removable member of Figure 9.

A milk frothing apparatuses according to this invention is labelled with the reference character 1 and is suitable for mixing milk with air and steam to obtain frothed milk. In Figures 1 to 3 the milk frothing apparatus 1 is shown mounted on a beverage-making machine 9, in particular for making a beverage containing milk, for example a frothed milk or a cappuccino. The whole of the machine 9 is not illustrated in the figures, since that is not considered necessary for the purposes of this description.

The machine 9 comprises a machine body, of which only a portion of an outer wall 91 is shown in the figures. The machine body houses or contains a boiler for producing steam, in particular pressurised steam. The boiler is schematically illustrated and is labelled 92 in Figure 2. In the embodiment illustrated, the machine 9 comprises the milk frothing apparatus 1 , which is housed in a seat made in the outer wall 91 of the machine 9.

The milk frothing device 1 comprises a system for mixing milk with air and steam in order to obtain frothed milk, that is to say, foamy milk incorporating air bubbles. That mixing system can be implemented according to embodiments that in themselves are already known in the sector.

Specifically, the milk frothing apparatus 1 has a box-shaped body 11 containing a milk frothing chamber 20. That frothing chamber 20 is made, for example, in a manifold 21 .

Inside the box-shaped body 11 , the milk frothing apparatus comprises an air feeding duct 23, a milk feeding duct 25, a steam injecting nozzle 27 connected to a steam feeding duct 28, a frothed milk outfeed duct 29.

The frothing chamber 20 is connected, directly or by means of stretches shared by multiple ducts, to the air feeding duct 23, to the milk feeding duct 25, to the steam injecting nozzle 27 and to the frothed milk outfeed duct 29. In use, the steam injecting nozzle 27 is in communication with the boiler 92 of the machine 9 (in particular by means of the steam feeding duct 28), to receive the steam required for operation of the milk frothing apparatus 1 . The boiler 92, which in use is a steam generator, is connected to a steam supplying element 95, which is fixed to the outer wall 91 and passes through it, projecting into the seat for the milk frothing apparatus 1 . When the milk frothing apparatus 1 is in the mounted condition in the seat, the steam feeding duct 28 is engaged on the steam supplying element 95.

The steam injecting nozzle 27 is interposed between the steam feeding duct 28 and the frothing chamber 20. The nozzle 27 has a converging cross- section which, when it receives a flow of pressurised steam, creates a local pressure drop such that it causes milk to be sucked from the milk feeding duct 25 and air from the outside environment through the air feeding duct 23. Therefore, in the chamber 20 the milk, air and steam are mixed, producing a frothed milk.

The air feeding duct 23 puts the frothing chamber 20 in communication with an air inlet opening 30, through which the outside air is drawn in so that it can be supplied to the frothing chamber 20. In particular, the air feeding duct 23 is a path composed of multiple stretches (not necessarily tubular in shape) having different shapes and arranged one after another.

In the embodiment illustrated, the air inlet opening 30 is made in a member 3 that also comprises a stretch of the air feeding duct 23. That member 3 is removable, being removably inserted in a respective housing made in the box-shaped body 11 . The air inlet opening 30 is a through hole made through the wall of the removable member 3 and draws air from the hollow space between the removable member 3 and the housing in which the latter is inserted. Further details about the air feeding duct 23 and the removable member 3 will be described below.

In the embodiment illustrated, the milk frothing apparatus 1 comprises a milk container 5 that is connected to the milk feeding duct 25. The milk container 5 has a box-shaped body 51 containing an inner space 50 intended to hold the milk to be frothed. A pickup pipe 55 extends in the inner space 50 and substantially reaches the bottom of the box-shaped body 51 . The opposite end of the pickup pipe 55 is equipped with a tubular connector 58 by means of which the pickup pipe is coupled to the milk feeding duct 25, thereby allowing the frothing chamber 20 to receive the milk to be frothed.

The milk container 5 is removably couplable to the box-shaped body 11 of the milk frothing apparatus 1 . In particular, in the coupled condition the box- shaped body 11 of the milk frothing apparatus 1 is at the top of the milk container 5. The removed milk container 5 may be placed in a refrigerator to preserve the milk contained in it during a period of time when it is not used. If necessary, the milk frothing apparatus 1 may also be removed and placed in a refrigerator. The components of the milk frothing apparatus 1 that are intended to make contact with the milk may be completely disassembled to make cleaning of them easier.

In the embodiment illustrated, the milk frothing apparatus 1 also comprises a dispensing spout 19 that is connected to the chamber 20 by means of the outfeed duct 29 and is, therefore, designed to dispense the frothed milk produced in the chamber 20. The dispensing spout 19 extends laterally from the box-shaped body 11 and in particular, during use, can dispense frothed milk directly into a cup below.

The milk frothing apparatus 1 also comprises a non-return device 4 positioned in a stretch of the air feeding duct 23. The non-return device 4 is designed to allow a flow of air from the air inlet opening 30 towards the frothing chamber 20 and to stop a flow of air and/or milk (for example, drops of milk mixed with air) towards the air inlet opening 30.

The non-return device 4 comprises a sealing element 41 that extends transversally in the respective stretch of the air feeding duct 23. The sealing element 41 , which is substantially disk-shaped, has a first face 411 towards the air inlet opening 30 and a second face 412 towards the frothing chamber 20. In other words, relative to the direction of flow of the air from the inlet 30 to the frothing chamber 20, the first face 411 faces upstream and the second face 412 faces downstream. Therefore, the first face 411 is struck by the flow of air entering, whilst the second face 412 would be struck by any flow of air and/or milk from the frothing chamber 20 (or directly from the milk duct 25) towards the air inlet opening 30.

In particular, the sealing element 41 is made of deformable material, more particularly of elastically deformable material such as rubber or another elastomeric material.

The non-return device also comprises a support 43, to which the sealing element 41 is constrained, and an annular contact element 47 facing the first face 411 of the sealing element 41 .

In particular, the annular contact element 47 is a collar, inside the duct, located at a change in the cross-section (specifically, a change in diameter) of the air feeding duct 23.

The support 43 and the annular contact element 47 are fixed relative to the air duct 23, whilst, as explained below, the sealing element 41 has a degree of deformation or of mobility relative to them.

The sealing element 41 is fixed to the support 43 at a central region 415 of the sealing element 41 . In particular, the support 43 has a mushroom- shaped head 431 , that is positioned substantially coaxial with the respective stretch of air feeding duct 23. The sealing element 41 is fixed with a snap-fit connection on the mushroom-shaped head 431 , which in particular passes through a hole 416 at the centre of the sealing element 41 and retains the latter thanks to radial projections. Therefore, the central region of the sealing element 41 is substantially fixed relative to the air feeding duct 23.

The sealing element 41 has an annular peripheral region 417 (which for illustration purposes only is shown delimited by a dashed line in Figure 9) that is flexible relative to the central region 415 and is intended to make contact with the annular contact element 47.

The sealing element 41 is deformable between a first condition (shown in Figure 10) and a second condition (shown in Figure 11 ). In both Figures 10 and 11 the deformation of the sealing element 41 is accentuated for greater clarity. In the first condition, the annular peripheral region 417 (in particular, the first face 411 in the annular peripheral region 417) is in sealed contact with the annular contact element 47, in such a way that the sealing element 41 completely closes the passage section of the air feeding duct 23. Basically, the annular peripheral region 417 is against the annular contact element 47 on the entire perimeter and therefore the two operating in conjunction with each other do not leave any passage for a flow of air and/or milk.

In the second condition, the annular peripheral region 417 is at least partly at a distance from the annular contact element 47, in such a way that a passage for the air is available between the sealing element 41 and the annular contact element 47. Basically, in at least one stretch along the perimeter the annular peripheral region 417 is not in contact with the annular contact element 47 because it is moved in the downstream direction. Thanks to the passage created in this way, a flow of air can move past the annular contact element and, by going around the edge of the sealing element 41 , can continue towards the frothing chamber 20. In Figure 11 , the path of the flow of air from the inlet opening 30 as far as the outfeed of the non-return device 4 is schematically indicated with dashed lines labelled 300.

In the embodiment illustrated, in the second condition, the annular peripheral region 417 is at a distance from the annular contact element 47 on its entire perimeter, so that the passage for the air is an annular passage that involves the whole edge of the sealing element 41 .

As shown in the figures, the deformed sealing element 41 has a conical shape, whose taper varies with the deformation. In use, although with the required proportions and structural differences, the sealing element deforms in a similar way to the canopy of an umbrella, in which between the closed condition and the open condition the peripheral edge moves axially relative to the centre and its diameter is reduced. Obviously, for the sealing element 41 that movement is not very accentuated because a small deformation is enough (and therefore a small distance from the annular contact element 47) to create a sufficient passage for the quantity of air to be used for frothing the milk.

The condition adopted by the sealing element 41 is linked to a difference between the pressure acting on the first face 411 (that is to say, the upstream pressure) and a pressure acting on the second face 412 (that is to say, the downstream pressure). Therefore, the sealing element 41 automatically responds to the pressure conditions upstream and downstream of it.

During the frothing step, the flow of steam in the nozzle 27 creates a pressure drop downstream of the sealing element 41 . For example, the nozzle 27 forms a device with Venturi effect, in itself known in the sector. The pressure acting on the second face 412 is less than the atmospheric pressure acting on the first face 411 , therefore acting on the sealing element 41 there is a resulting force (in the downstream direction) that deforms it, bringing it into the second condition and so allowing the inflow of air towards the frothing chamber 20. At the end of the frothing step, when the flow of steam is interrupted and the pressure downstream of the sealing element 41 is increased, the pressure difference is reduced (or even inverted, if the downstream pressure becomes greater than the upstream pressure), making the sealing element 41 return to the first condition, to prevent milk from being able to reach the region of the air inlet opening 30. It should be noticed that the higher the downstream pressure is compared with the upstream pressure (something that in the absence of the non-return device would cause a proportional flow of milk towards the air inlet opening 30), the greater the closing force is acting on the second face 412 and, therefore, the response speed of the non-return device 4, as well as the effectiveness of the seal.

In particular, as already mentioned above, the sealing element 41 is elastically deformable. Relative to the first condition, the sealing element 41 is deformed in the second condition when the difference between the upstream pressure and the downstream pressure is greater than a threshold value. The sealing element 41 has an elastic return towards the first condition when the pressure difference is zeroed. In use, the non-return device 4 is normally in a closed condition and it only opens during the frothing step, after the pressure drop produced by the steam nozzle 27.

It should also be noticed that in the first condition the sealing element 41 may be deformed relative to a home condition, although it is less deformed than in the second condition. In fact, it should be noticed that even in Figure 10, which shows the first condition, the sealing element 41 is not perfectly flat and is deformed, in other words, it is preloaded. That is useful for ensuring that the sealing element 41 presses with a predetermined force against the annular contact element 47, in order to guarantee a sealed contact.

In the embodiment illustrated, the sealing element 41 is mounted on the removable member 3. That is useful for allowing easy cleaning of the nonreturn device 4 without the need to disassemble parts of the apparatus 1 . In fact, in order to gain access to the sealing element 41 it is sufficient to pull the removable member 3 out of its housing.

In particular, the removable member 3 also comprises the support 43 and the annular contact element 47, therefore the removable member 3 includes the whole non-return device 4. That is useful for making possible complete cleaning of the non-return device 4, in order to eliminate all milk deposits in the air duct 23.

As shown in Figures 9 to 11 , the removable member 3 comprises a cylindrical shell 31 in which the air inlet opening 30 is made. The removable member 3 also comprises a body 32 that is inserted in the cylindrical shell 31 and has a cavity 33 for air transit, the cavity 33 communicating with the air inlet opening 30. Therefore, the cavity 33 is a stretch of the air feeding duct 23. In particular, the cavity 33 constitutes an initial stretch of the air duct 23. If necessary, the cylindrical shell 31 may have a further air inlet opening 30a.

The removable member 3 comprises a seat for the sealing element 41 , said seat being for example the bottom of the body 32 at the mouth of the cavity 33. The support 43 is part of the body 32 and extends in the cavity 33 as far as the seat.

The annular contact element 47 is made at the mouth of the cavity 33 that faces the seat for the sealing element 41 . In particular, the annular contact element 47 is a collar formed by the change in diameter between the seat and the cavity 33. In fact, as is obvious in the figures, the diameter of the seat (that is to say, the diameter of the bottom of the body 32) is greater than the diameter of the cavity 33.

The sealing element 41 is a circular disk having a diameter that is intermediate between the diameter of the cavity 33 and the diameter of the seat.

The removable member 3 also comprises a lever grip 35, that is fixed to the cylindrical shell 31 by means of a pin or screw 36.

When the removable member 3 is inserted in the respective housing made in the box-shaped body 11 , the lever grip 35 projects from the box-shaped body 11 and enables it to be gripped by a user, for example to remove the removable member 3.

In one embodiment, the removable member 3 may also have a control function for controlling the flow of air through the air duct 23. Specifically, the removable member 3 in the respective housing can be rotated about its own axis between a normal operating position, corresponding to a flow of air suitable for milk frothing, and a position for running a cleaning cycle. The removable member 3 can also be moved into a position in which it can be disengaged from the box-shaped body 11 , so that it can be pulled out and removed for cleaning by the user.

In one embodiment, the machine 9 also comprises an infusion chamber (not illustrated) for making a second beverage, in particular for making coffee, and a respective dispensing spout (also not illustrated) for dispensing the second beverage. The infusion chamber and the other parts necessary for making the second beverage (for example, a pump and a water heater) are housed in the machine body. This invention relates in particular to the aspects relating to making frothed milk, whilst the aspects relating to making a beverage by infusion may be implemented as in prior art apparatuses and, therefore, they are not described in further detail herein. In that embodiment, combined use of the milk frothing apparatus 1 and of the infusion chamber enables, for example, a cappuccino to be made. That is to say, a beverage containing coffee and frothed milk. Further details and variants may be found in Italian patent application No. 102015000084746 (filed on 17/12/2015 in the name of this Applicant) which is entirely incorporated here as a reference.

The invention described above may be modified and adapted in several ways without thereby departing from the scope of the inventive concept. For example, in alternative embodiments, the sealing element 41 could be a non-circular disk (for example elliptical) or even a disk with a polygonal shape. In this disclosure, "substantially disk-shaped" means that the sealing element has a mainly two-dimensional shape, approximately with radial symmetry relative to a central region, meaning that it has two opposite faces and a thickness that is small compared with the faces. The purpose of the shape of the sealing element 41 is substantially to adapt to the shape of the passage section of the respective stretch of air duct (in order to be able to close it operating in conjunction with the contact element 47) and to deform in the ways described above.

All details may be substituted with other technically equivalent elements and the materials used, as well as the shapes and dimensions of the various components, may vary according to requirements.

Claims

A milk frothing apparatus (1 ) suitable for mixing milk with air and steam to obtain frothed milk, comprising:

- an air feeding duct (23);

- a milk feeding duct (25);

- a steam injecting nozzle (27);

- a frothed milk outfeed duct (29);

- a frothing chamber (20) that is connected to the air feeding duct (23), to the milk feeding duct (25), to the steam injecting nozzle (27) and to the frothed milk outfeed duct (29);

wherein the air feeding duct (23) puts the frothing chamber (20) in communication with an air inlet opening (30);

wherein, in use, a flow of steam in the steam injecting nozzle (27) creates a vacuum that sucks milk and air into the frothing chamber (20), through the respective feeding ducts (23, 25), thereby mixing milk with air and steam;

the milk frothing apparatus (1 ) further comprising a non-return device (4) positioned in a stretch of the air feeding duct (23), the non-return device (4) being designed to allow a flow of air from the air inlet opening (30) towards the frothing chamber (20) and to stop a flow of air and/or milk towards the air inlet opening (30);

the non-return device (4) comprising a sealing element (41 ), substantially disk-shaped, that extends transversally in the air feeding duct (23) and has a first face (411 ) towards the air inlet opening (30) and a second face (412) towards the frothing chamber (20), the non-return device (4) further comprising a support (43) for the sealing element (41 ) and an annular contact element (47) facing the first face (411 ) of the sealing element (41 );

the sealing element (41 ) having a central region (415) that is fixed to the support (43) and an annular peripheral region (417) that is flexible relative to the central region (415) and is intended to make contact with the annular contact element (47);

the sealing element (41 ) being deformable between a first condition, in which the annular peripheral region (417) is in sealed contact with the annular contact element (47) so that the sealing element (41 ) completely closes the passage section of the air feeding duct (23), and a second condition, in which the annular peripheral region (417) is at least partly at a distance from the annular contact element (47) so that a passage for the air is available between the sealing element (41 ) and the annular contact element (47);

the condition adopted by the sealing element (41 ) being linked to a difference between the pressure acting on the first face (411 ) and a pressure acting on the second face (412).

The milk frothing apparatus (1 ) according to claim 1 , wherein the sealing element (41 ) is elastically deformable, the sealing element (41 ) being deformed in the second condition when said pressure difference is greater than a threshold value, the sealing element (41 ) having an elastic return towards the first condition.

The milk frothing apparatus (1 ) according to claim 1 or 2, wherein in the second condition the annular peripheral region (417) of the sealing element (41 ) is at a distance from the annular contact element (47) on its entire perimeter, so that the passage for the air is an annular passage. The milk frothing apparatus (1 ) according to any one of claims 1 to 3, wherein said support (43) comprises a mushroom-shaped head (431 ) on which the sealing element (41 ) is fixed with a snap-fit connection.

The milk frothing apparatus (1 ) according to any one of claims 1 to 4, wherein said annular contact element (47) is a collar at a change in cross-section of the air feeding duct (23).

The milk frothing apparatus (1 ) according to any one of claims 1 to 5, comprising a removable member (3) on which the sealing element (41 ) is mounted, the removable member (3) also comprising the air inlet opening (30) and a stretch (33) of the air feeding duct (23).

7. The milk frothing apparatus (1 ) according to any one of claims 1 to 6, comprising a removable member (3) that includes the non-return device (4), the removable member (3) comprising a seat for the sealing element (41 ) and a cavity (33) for air transit, the annular contact element (47) being made at the mouth of the cavity (33) that faces the seat.

8. The milk frothing apparatus (1 ) according to any one of claims 1 to 7, comprising a milk container (5) connected to the milk feeding duct (25). 9. The milk frothing apparatus (1 ) according to any one of claims 1 to 8, comprising a dispensing spout (19) for dispensing frothed milk, the dispensing spout (19) being connected to the frothing chamber (20) by the frothed milk outfeed duct (29).

10. A beverage-making machine (9), comprising a milk frothing apparatus (1 ) according to any one of claims 1 to 9 and a boiler (92) for producing steam, the steam injecting nozzle (27) of the milk frothing apparatus (1 ) being in communication with the boiler (92) to receive steam.