Mixing device for the application of a surface action agent by steam

Abstract

A mixing device (100) comprises a body (1), a steam supply system (3) connected to the body to supply steam (V) into the body, an injector (2) mounted in the body (1), an agent supply system (4) connected to the injector (2) to supply a agent (D) into the injector, and a delivery system (5) connected to the body (1) to deliver a mix (M) of steam (V) and agent (D); the body (1) of the mixing device comprises a first chamber (C1), a second chamber (C2), a third chamber (C3) and a fourth chamber (C4) communicating with each other and arranged axially.

Description

[0001] MIXING DEVICE FOR THE APPLICATION OF A SURFACE ACTION AGENT BY STEAM

[0002] DESCRIPTION

[0003] The present invention relates to a mixing device for the application of a surface action agent by means of steam, wherein the agent may be a disinfectant agent, a plant protection agent, a pesticidal agent, or the like, and the mixing device may be used for the cleaning, disinfection, and disinfestation of surfaces.

[0004] As it is well known, a widely used method for cleaning surfaces that cannot be treated directly with jets of water for various reasons provides for using steam obtained by heating water in a special boiler to the boiling point. Due to the heat and solvent action of the steam, as well as to its mechanical action, such a method ensures that the treated surface is cleaned, but not disinfected.

[0005] In order to solve such a problem, mixing devices suitable for mixing an agent with steam and delivering steam containing the agent are known.

[0006] W020051 07966A1 discloses such a type of mixing device comprising a single constant-volume mixing chamber wherein the steam and the agent are mixed. A calming zone is formed in the mixing chamber where the countercurrent mixing between the steam and the agent takes place. The mixing chamber is arranged in a jacket filled with a heat transfer fluid heated by an electric resistance.

[0007] The mixing device described in W02005107966A1 is impaired by some drawbacks due to the presence of the jacket, the heat transfer fluid, and the heating element, which increase the complexity, cost, and size of the device. Furthermore, precisely because a calming zone is created in the mixing chamber, the calming zone does not contribute to efficiently mixing the steam and the agent.

[0008] US2008 / 062813A1 describes a mixer for high-purity chemicals, such as water, various chemicals, solutions, suspensions of solids, sludge, or other similar materials. Such a document refers to liquid or pasty products at room temperature and does not describe gaseous products, such as steam, at a temperature of 130°-150°C. Such a mixer has an injector arranged in a first cylindrical chamber. Since the use of steam at a temperature of 130°-150°C is not envisaged, the injector obviously cannot be preheated by steam. Furthermore, the injector has a cylindrical tip with a single outlet hole and the tip of the injector does not reach a second truncated conical chamber.

[0009] US2024 / 225081 A1 describes a mixer for mixing fumes in a solvent. The mixer has an injector with a conical tip having a single axial outlet. The mixer has a first cylindrical chamber and a second truncated conical chamber. However, the tip of the injector is located only in the first cylindrical chamber and is not located in the second truncated conical chamber, so that no annular cavity is formed between the tip of the injector and the second truncated conical chamber.

[0010] EP2060318A1 discloses a system for injecting a gas into a liquid in order to create bubbles. In such a system, the steam is injected by means of an injector into a conduit wherein a liquid agent flows. Therefore, no injector is provided for injecting the liquid agent.

[0011] The purpose of the present invention is to eliminate the drawbacks of the prior art by providing a mixing device for applying a surface action agent by means of steam, which is compact, space-saving, economical, and simple to manufacture.

[0012] Another purpose is to provide such a mixing device that is efficient, effective, and reliable.

[0013] Yet another purpose is to provide such a mixing device that is versatile and easy to use.

[0014] These purposes are achieved in accordance with the invention with the characteristics of the attached independent claim 1 .

[0015] Advantageous embodiments of the invention are apparent from the dependent claims. Further features of the invention will become clearer from the detailed description below, which refers to a purely exemplary and therefore non-limiting embodiment illustrated in the accompanying drawings, wherein:

[0016] Fig. 1 is a sectional view of the mixing device according to the invention;

[0017] Fig. 2 is an exploded sectional view illustrating the body and injector of the mixing device of Fig. 1 ;

[0018] Fig. 3 is an enlarged detail of the mixing chamber of the mixing device of Fig. 1 ;

[0019] Fig. 4 is a perspective view of the mixing device according to the invention;

[0020] Fig. 5 is a sectional view of the body and of the injector of the mixing device wherein the steam is schematically represented by dots, the agent is schematically represented by crosses, and the mix is schematically represented by triangles;

[0021] Fig. 6 is an axial sectional view showing an exploded view of a second embodiment of the mixer according to the invention.

[0022] With the aid of the figures, the mixing device according to the invention, which is comprehensively indicated with the reference numeral 100, is described.

[0023] With reference to Fig. 1 , the mixing device (100) comprises a body (1 ), an injector (2), a steam supply system (3), an agent supply system (4), and a delivery system (5).

[0024] With reference to Fig. 2, the body (1 ) has a substantially cylindrical shape with an axis (A), an upper wall (10), a lower wall (1 1 ), and a central wall (12).

[0025] Four chambers (C1 , C2, C3, C4) are formed in the body (1 ), communicating with each other and extending axially inside the body (1 ). The four chambers comprise a first chamber (C1 ), a second chamber (C2), a third chamber (C3), and a fourth chamber (C4). The four chambers (C1 , C2, C3, C4) have a different shape and axial symmetry with respect to the axis (A) of the body of the mixer. The first chamber (C1 ) has a cylindrical shape and operates as a heating chamber, as it will be explained below.

[0026] The second chamber (C2) has a truncated conical tapered shape with decreasing diameter from the first chamber (C1 ) to the third chamber (C3). The second chamber (C2) has an inlet section (13a) with a smaller diameter than the diameter of the first chamber (C1 ).

[0027] With reference to Fig. 3, the second chamber (C2) has a taper angle (a) that may be comprised in the range of 50°-70°, preferably 60°. The second chamber (C2) extends axially for a lower length (L2) than the length (L1 ) of the first chamber (C1 ). The second chamber (C2) has an outlet section (13b) that continues with a narrowing (16).

[0028] The second chamber (C2) operates as a mixing chamber, wherein the mixing of the steam and the agent begins, as it will be explained in detail hereinafter.

[0029] Going back to Fig. 2, the narrowing (16) communicates with the third chamber (C3). The third chamber (C3) is suitable for operating as an expansion chamber wherein the mix of agent and steam expands. The third chamber (C3) comprises two portions (15a, 15b) of different geometry. The two portions of the third chamber (C3) comprise a first portion (15a) and a second portion (15b).

[0030] The first portion (15a) of the third chamber has a tapered shape with increasing diameter starting from the narrowing. In such a case, the term “tapered” does not only refer to a truncated conical shape, but to any shape with a gradually increasing diameter. Preferably, the first portion (15a) of the third chamber is shaped like a dome or a segment of a sphere with the narrowing (16) located at a pole of the segment of a sphere.

[0031] The second portion (15b) of the third chamber has a cylindrical or rounded shape to connect the first portion (15a) of the third chamber with the fourth chamber (C4). The second portion (15b) of the third chamber has a diameter equal to the maximum diameter of the first portion (15a) of the third chamber. The fourth chamber (C4) operates as a turbulence chamber, wherein the turbulent and swirling motion of the mix ensures the perfect mixing between the agent and the steam.

[0032] The fourth chamber (C4) has a tapered shape with a decreasing diameter starting from the second portion (15b) of the third chamber.

[0033] With reference to Fig. 3, the fourth chamber (C4) has a truncated conical shape with a taper angle (8) comprised in the range of 20°-40°, preferably 30°.

[0034] In the axial direction, the first chamber (C1 ) has a length (L1 ), the second chamber (C2) has a length (L2), the third chamber (C3) has a length (L3), the fourth chamber (C4) has a length (L4), and the narrowing (16) has a length (L5). The first portion (15a) of the third chamber has a length (L3a) and the second portion (15b) of the third chamber has a length (L3b).

[0035] The length (L2) of the second chamber (C1 ) is lower than the length (L1 ) of the first chamber (C1 ). The ratio between the length (L2) of the second chamber (C2) and the length (L1 ) of the first chamber (C1 ) is comprised between 0.3 and 0.6.

[0036] The length (L3) of the third chamber (C3) is lower than or equal to the length (L2) of the second chamber (C2). The ratio between the length (L3) of the third chamber (C3) and the length (L2) of the second chamber (C2) is comprised between 0.6 and 1 .

[0037] The length (L4) of the fourth chamber (C4) is greater than the length (L3) of the third chamber (C3). The ratio between the length (L4) of the fourth chamber (C4) and the length (L3) of the third chamber (C3) is comprised between 2.4 and 3.

[0038] The length (L5) of the narrowing (16) is lower than the length (L3) of the third chamber (C3). The ratio between the length (L5) of the narrowing (16) and the length (L3) of the third chamber (C3) is comprised between 0.14 and 0.15.

[0039] The length (L3b) of the second portion (15b) of the third chamber is greater than the length (L3a) of the first portion (15a) of the third chamber. The ratio between the length (L3b) of the second portion (15b) of the third chamber and the length (L3a) of the first portion (15a) of the third chamber is comprised between 1 .2 and 1 .6. Going back to Fig. 2, in the upper wall (10) of the body there is an axial hole (17) communicating with the first chamber (C1 ). In the central wall (12) of the body there is a radial hole (18) communicating with the first chamber (C1 ).

[0040] In the lower wall (1 1 ) of the body there is an outlet hole (19) arranged axially and communicating with an outlet section of the third portion (15c) of the third chamber. The outlet hole (19) has a lower length (L6) than the length (L4) of the fourth chamber.

[0041] The injector (2) is suitable for injecting an agent, such as a disinfectant, plant protection agent, or pesticidal agent, which may be in liquid form.

[0042] The injector (2) has a cylindrical body (20) with a cylindrical axial channel (21 ) that is open at a rear end of the body (20). The body (20) of the injector has a tapered tip (22) with decreasing diameter. With reference to Fig. 3, the tip of the injector has a conical shape, with a taper angle (P) that is slightly lower than the taper angle (a) of the second chamber (C2). The taper angle (P) of the injector tip may be comprised in the range of 40°-60°, preferably 50°.

[0043] Advantageously, the ratio between the taper angle (a) of the second chamber (C2) and the taper angle (P) of the injector tip is between 1.1 and 1 .3.

[0044] The injector (2) comprises a plurality of outlet holes (23) communicating with the axial channel (21 ) of the injector and ending in the tip (22) of the injector. The outlet holes (23) of the injector are not radial, but have an axis that is inclined with respect to the axis of the injector by an angle (y) of less than 90°, preferably comprised in the range of 40°-60°.

[0045] The injector (2) is provided at the back with a collar (24) having a larger diameter than the body (20) of the injector.

[0046] With reference to Fig. 1 , the body (20) of the injector body is inserted axially into the axial hole (17) of the body of the mixer, so that the body (20) of the injector is located in the first chamber (C1 ) and the tip (22) of the injector is located in the second chamber (C2). The collar (24) of the injector abuts against the upper wall (10) of the body of the mixer and remains outside the body of the mixer. Although the figures show an injector with a collar (24) abutting against the upper wall (10) of the body of the mixer outside the first chamber (C1 ), the injector (2) may have a collar abutting against the upper wall (10) of the body of the mixer in the first chamber (C1 ), or the injector (2) may be made in a single body with the upper wall (10) of the body of the mixer.

[0047] With reference to Fig. 3, a cavity (G) is generated between the tip (22) of the injector and the wall of the second chamber (C2), said cavity (G) being provided with an annular section around the tip (22) of the injector.

[0048] Due to the different taper angle between the second chamber (C2) and the tip (22) of the injector, the cavity (G) has an inlet section with a width (D1 ) greater than the width (D2) of an outlet section. Otherwise said, the width of the cavity (G) decreases gradually from the inlet section toward the outlet section.

[0049] It should also be noted that the narrowing (16) has a diameter (D3) which is a minimum diameter. The second portion (15b) of the third chamber has a diameter (D4) much greater than the diameter (D3) of the narrowing (16), and the axial outlet hole (19) has a lower diameter (D5) than the diameter (D4) of the second portion (15b) of the third chamber.

[0050] The ratio between the diameter D4 of the second portion of the third chamber and the diameter D3 of the narrowing is comprised between 6-8.

[0051] The ratio between the diameter D4 of the second portion of the third chamber and the diameter D5 of the axial outlet hole is comprised between 3.5-5.5.

[0052] With reference to Figs. 1 and 4, the steam supply system (3) comprises a boiler (30) containing water that is heated to generate steam (V) at a temperature of approximately 130°-158 °C. A duct (31 ) connects the boiler (30) to the radial hole (18) of the body of the mixer, so that the steam (V) enters the first chamber (C1 ) and surrounds the body (20) of the injector in order to heat the injector (2). A solenoid valve (32) and a flow regulator (33) are arranged in the duct (31 ) of the steam supply system. By way of example, the flow rate of the steam (V) can be set so that the steam supply system (3) supplies steam at a pressure comprised between 2.5 and 6 bar.

[0053] The agent supply system (4) comprises a tank (40) containing an agent (D). The tank (40) is connected to the axial channel (21 ) of the injector by means of a conduit (41 ). A pump (42) and a solenoid valve (43) are located in the conduit (41 ) of the agent supply system (4).

[0054] The pump (42) is a peristaltic pump configured to self-regulate according to the pressure required for the injection of the agent. By way of example, during operation, the pump (42) operates at a pressure of 1 -2 bar.

[0055] The delivery system (5) comprises a dispensing lance (50) equipped with a dispensing nozzle (51 ) suitable for dispensing the mix of steam and agent. The dispensing nozzle (51 ) has a diameter of 1 .2-2 mm.

[0056] The dispensing lance (50) has a button (52) that can be operated by the user to dispense the mix of steam and agent. The dispensing lance (50) is connected to the axial outlet hole (19) of the body of the mixer by means of a delivery pipe (53). A solenoid valve (54) is located in the axial outlet hole (19) or downstream of the mixer in order to deposit the liquid that condenses when the dispensing is interrupted as much as possible outside the mixer.

[0057] The delivery pipe (53) is suitably dimensioned to limit the pressure drops and, above all, to allow a heat exchange between the steam and the agent, as the steam transfers part of its temperature to the agent. If the boiler is configured to have a steam flow rate with a pressure of 2.5-6 bar, the delivery pipe (53) has a length of 2-3 m and an internal diameter of 5-8 mm.

[0058] With particular reference to Figs. 1 and 5, the operation of the mixing device (100) is described.

[0059] In an initial configuration, all the solenoid valves (32, 43, 54) are closed and the chambers (C1 , C2, C3, C4) are empty.

[0060] Initially, the solenoid valve (32) of the steam supply system is opened. Therefore, the steam (V) (shown schematically in Fig. 5 with dots) enters the first chamber (C1 ) and surrounds the body (20) of the injector.

[0061] The steam (V) is at a temperature of 130°-158 °C. In such a way, the body (20) of the injector is heated by heat exchange with the steam contained in the first chamber (C1 ). For such a purpose, the body (20) of the injector is made of a heat-conducting metal, such as steel. A heating time of approximately 50-70 seconds is sufficient to heat the body (20) of the injector to a temperature of 130°-158°C that is equal to that of the steam. After the heating time has elapsed, the peristaltic pump (42) is activated and the solenoid valve (43) of the agent supply system is opened. In such a way, the agent (D) (shown in Fig. 5 with crosses) is fed into the axial channel (21 ) of the injector, where it is heated by heat exchange with the body (20) of the injector.

[0062] The agent (D) that has been heated in the body of the injector exits through the outlet holes (23) of the injector and begins to mix with the steam (V) in the cavity (G) between the tip (22) of the injector and the second chamber (C2), thus forming a mix (M) (shown schematically in Fig. 5 with triangles). The fact that the agent (D) has been heated in the injector (2) prevents a thermal shock between the agent (D) and the steam (V) and, above all, reduces the formation of condensation.

[0063] It should be noted that the steam (V) in the first chamber (C1 ) is at minimum speed and maximum pressure since the first chamber (C1 ) is the chamber with the largest diameter and volume.

[0064] When the steam (V) enters the cavity (G), the steam begins to increase its speed and decrease its pressure because the cavity (G) has a much smaller volume than the first chamber (C1 ).

[0065] The agent (D) mixes with the steam (V) in the cavity (G), wherein the mix (M) of steam (V) and agent (D) is generated.

[0066] The truncated conical shape of the tip (22) of the injector, the fact that the tip (22) of the injector is located in the second chamber (C2) forming the cavity (G), and the fact that the tip of the injector has a plurality of outlet holes (23) ending into the cavity, contribute to achieving a perfect mixing between the steam (V) and the agent (D).

[0067] The section of the cavity (G) gradually decreases until it reaches the narrowing (16) that operates as a bottle neck for the mix (M).

[0068] Therefore, the mix (M) in the narrowing (16) has the maximum speed and the minimum pressure.

[0069] Once past the narrowing (16), the mix (M) expands abruptly in the first portion (15a) and in the second portion (15b) of the third chamber, wherein the mix (M) has the minimum speed and the maximum pressure. In fact, the diameter D4 of the second portion (15b) of the third chamber is much greater than the diameter (D3) of the narrowing (16).

[0070] Subsequently, the mix (M) flows into the fourth chamber (C4) where the mix (M) undergoes a turbulent and swirling motion indicated by the arrows (F).

[0071] Such a swirling motion of the mix (M) contributes to a perfect mixing of the steam (V) and the agent (D). During the flow of the mix into the fourth chamber (C4), the pressure of the mix decreases gradually and the speed of the mix increases gradually.

[0072] Finally, the mix (M) reaches the axial outlet hole (19) with a minimum pressure and a maximum speed. In fact, the diameter D5 of the axial outlet hole is much smaller than the diameter D4 of the second portion (15b) of the third chamber.

[0073] It should be noted that there are many differences between the mixing device (100) and the one described in W02005107966A1 .

[0074] In fact, the mixing device (100) does not require any heating jacket with heat transfer fluid heated by a resistance.

[0075] In the mixing device (100), the mixing no longer takes place in countercurrent in a calming chamber, but takes place in the second chamber (C2), in the third chamber (C3) and in the fourth chamber (C4), which are chambers with different cross-sections and therefore dynamic chambers, as the steam (V) and the agent (D) are subjected to new specific dynamics originating from the continuous variations in pressure, speed, and temperature in a unidirectional flow.

[0076] The injector (2) is located in the body (1 ) of the mixer, so that the agent (D) is preheated in the injector (2) to limit its thermal stress when it comes into contact with the steam (V).

[0077] The dimensions of the chambers (C1 , C2, C3, and C4) and the material of the body (1 ) of the mixer are such as to maintain a stable operating temperature inside the body (1 ) of the mixer in order to prevent internal condensation of the mix. To further reduce the problem of condensation, the body (1 ) of the mixer can be made of polymer instead of steel. The two-phase mix (M) of steam (V) and agent (D) is produced by means of a new physical process that ensures a more homogeneous mixing through both a preheating of the agent (D) in the injector (2) and through a series of pressure and speed variations of the fluids in the chambers of the body of the mixer.

[0078] The mixing takes place in two phases.

[0079] In the first mixing phase, the steam (V) is conveyed into the cavity (G), wherein the steam passage section is significantly reduced, its speed increases considerably, and its pressure is reduced. Along this path of the steam (V) in the cavity (G), the agent (D) is injected into the steam (V) through the small outlet holes (23) of the injector. In this low-pressure phase, the first mixing of the steam with the agent takes place.

[0080] In the second mixing phase, the mix (M) of steam and agent is fed into the first portion (15a) and into the second portion (15b) of the third chamber, where it undergoes expansion. In contrast to what happens in the cavity (G) of the second chamber, when the mix (M) is in the first portion (15a) and in the second portion (15b) of the third chamber, the mix (M) undergoes a significant reduction in speed and a significant increase in pressure. These factors cause further atomization / fission of the particles of the agent (D), ensuring a perfect mixing of the agent (D) with the steam (V).

[0081] The two-phase mix (M) is then directed to the fourth chamber (C4), which has a truncated conical shape with a decreasing diameter toward the axial outlet hole (19) located at the end of the mixer. In such a way, the pressure and speed values of the mix (M) directed to the delivery pipe (53) tend to be substantially equal to the pressure and speed values of the steam (V) that has been fed into the body (1 ) of the mixer.

[0082] The mix (M) exits the nozzle (51 ) of the dispensing lance (50) at a temperature of 90°C and then reaches approximately 25°-40°C at the maximum application distance. Such an application temperature of the mix causes a decrease in the surface tension of the agent (D) contained in the mix (A), allowing the agent (A) to penetrate deeply into surfaces of any shape or material, enhancing its microbicidal efficacy. Such a condition makes it possible to reduce the use of excessive quantities of agent (D), especially in cases where the agent (D) is a chemical product that is harmful to the environment.

[0083] When the mix (M) dispensed by the dispensing lance (50) comes into contact with the surface of a product to be treated, a condensation effect is created by the hot two-phase mix in contact with the surface of the product to be treated, which is at a lower temperature than the mix. Such a condensation effect produces an effective, continuous, and homogeneous decontaminating film that guarantees a continuous disinfection treatment, i.e., without leaving any undisinfected micro-spaces.

[0084] The mix (M) exits the dispensing lance (50) with high kinetic energy that allows the mix to reach all surfaces to be treated, including inaccessible or hard-to-reach areas which, if not decontaminated, represent a potential microbial reservoir and limit the effectiveness of the disinfection treatment.

[0085] Fig. 6 illustrates a second embodiment of the mixer, wherein elements that are the same or correspond to those already described are indicated with the same reference numerals.

[0086] In this second embodiment, the upper wall (10) of the body of the mixer is separated from the body (1 ) of the mixer, and the nozzle (2) has a collar (24) that is fixed to the upper wall (10) in the first chamber (C1 ).

[0087] The first chamber (C1 ), the second chamber (C2), and the first portion (15a) of the third chamber are formed in an intermediate body (1 a). The second portion (15b) of the third chamber and the fourth chamber (C4) are formed in a lower body (1 b) that is fixed to the intermediate body (1 a).

[0088] In this embodiment, the taper angles (a, £, 8) of the second chamber (C2) of the tip (22) of the nozzle and of the fourth chamber (C4) are comprised in the range of 50°-70°, preferably 60°, and are equal to each other. Furthermore, the fourth chamber (C4) has a shorter length than the length of the fourth chamber of the first embodiment.

[0089] Numerous equivalent modifications may be made to the present embodiment of the invention, which are within the reach of an expert of the field and fall in any case within the scope of the invention as disclosed by the attached claims

Claims

CLAIMS1. Mixing device (100) comprising:- a body (1 ),- a steam supply system (3) connected to the body to supply steam (V) into the body,- an injector (2) mounted in the body (1 ),- an agent supply system (4) connected to the injector (2) to supply an agent (D) into the injector, and- a delivery system (5) connected to the body (1 ) to deliver a mix (M) of steam (V) and agent (D), said body (1 ) of the mixing device comprises a first chamber (C1 ), a second chamber (C2), a third chamber (C3) and a fourth chamber (C4) communicating with each other and arranged axially; wherein said steam supply system (3) is configured in such a way to supply steam (V) into the first chamber (C1 ) and said injector has a body (20) arranged in the first chamber (C1 ) in order to be heated by the steam; wherein said injector (2) is configured in such a way to inject the agent (D) into the second chamber (C2) wherein it is mixed with the steam (V) to obtain said mix (M) that flows into the third chamber (C3) and into the fourth chamber (C4) and is ejected from an outlet hole (19) toward said delivery system (5); wherein the second chamber (C2) is tapered with decreasing dimensions going toward the third chamber (C3), the third chamber (C3) has increasing dimensions going toward the fourth chamber (C4) so as to operate as an expansion chamber, and the fourth chamber (C4) is tapered with decreasing dimensions going toward the outlet hole (19) to operate as a turbulence chamber in which the mix makes a swirling motion, characterized in that said injector (2) has a conical tip (22) disposed in said second chamber (C2) so as to generate a cavity (G) with annular section between the tip of theinjector and the second chamber and a plurality of outlet holes (23) communicating with an axial channel (21 ) of the injector and ending into the tip (22) of the injector.

2. The mixing device (100) according to claim 1 , wherein the second chamber (C2) has a taper angle (a) and the injector (2) has a taper angle (£) lower than the taper angle (a) of the second chamber (C2) so that said cavity (G) between the tip of the injector and the second chamber has an inlet section with a width (D1 ) greater than a width (D2) of an outlet section.

3. The mixing device (100) according to claim 2, wherein the second chamber (C2) has a taper angle (a) comprised in the range of 50°-70° and the tip (22) of the injector has a taper angle (£) comprised in the range of 40°-60°.

4. The mixing device (100) according to any one of the preceding claims, wherein a narrowing (16) is provided between the second chamber (C2) and the third chamber (C3).

5. The mixing device (100) according to claim 4, wherein the third chamber (C3) has a first portion (15a) shaped like a dome or a segment of a sphere with the narrowing (16) disposed on a pole of the segment of a sphere.

6. The mixing device (100) according to claim 5, wherein the third chamber (C3) has a second portion (15b) with cylindrical or rounded shape.

7. The mixing device (100) according to any one of the preceding claims, wherein the fourth chamber (C4) has a truncated conical shape with a taper angle (8) comprised in the range 20°-40°, preferably 30°.

8. The mixing device (100) according to any one of the preceding claims, wherein the second chamber (C2) has a length (L2) lower than the length (L1 ) of the first chamber; the third chamber (C3) has a length lower than or equal to the length (L2) of the second chamber; and the fourth chamber (C4) has a length (L4) greater than the length of the third chamber (C3).

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