Gas-infused water-based beverage preparation with pre-mixing

Abstract

The invention is directed to a system (2) for preparing a gas-infused water-based beverage, comprising: a dissolver (22) for dissolving gas, such as carbon dioxide, nitrogen or nitrogen contained in air, into water; a concentrate tank fluidly connected to a dosing pump (12); a mixing connector (10) with an inlet (10.1) for water, an inlet (10.2) for the concentrate and an outlet (10.3) for the water mixed with the concentrate; wherein the gas dissolver (22) is arranged downstream of the mixing connector (10) so as to dissolve gas into the water mixed with the concentrate.

Description

DescriptionGAS-INFUSED WATER-BASED BEVERAGE PREPARATION WITH PREMIXINGTechnical field

[0001] The invention is directed to the field of preparation of gas-infused waterbased beverages. The gas dissolved in the beverage can be carbon dioxide, nitrogen or nitrogen contained in air. The invention is directed to systems, devices and machines as well as to methods for the in-line preparation of gas-infused water-based beverages.Background art

[0002] Prior art patent document published CH 630246 A5 discloses a process for continuously producing a refreshing beverage, containing a sweetener, with a gaseous component, and a device for carrying out this process. The water is pre-chilled and mixed with a mixture of concentrates, like sweeteners, as well as with carbon dioxide in a venturi injector. The waterbased and CO2-infused beverage flows then to a static mixer intended to extend the contact time of the gas with the liquid. The different concentrates or sweeteners are injected by means of a dosing pump with four independent dosing heads. The water flow is controlled by means of a regulator upstream of the venturi injector, without using any dosing pump or the like. The carbon dioxide flow is measured by means of a flow meter. The concentration of the sweeteners in the water is measured by a refractometer arranged downstream of the static mixer and controlled by electrically adjusting the water regulator for adapting the water flow. Varying the water flow by adjusting the water regulator is however likely to cause variations of the pressure at the inlet of the venturi injector. Such variations might impair the quality of gas dissolving action in the venturi injector and static mixer. Further, the sweeteners concentration control by means of a refractometer limits the process and device to sweet beverages, whereas it is desirable to prepare other water-based beverage not necessarily containing sweeteners, like caffeine- and / or maltcontaining beverages.

[0003] Prior art patent document published US 10,752,484 B2 discloses a system and method for preparing a water-based beverage infused or infused with nitrogen. The beverage can be nitrogen infused chilled coffee. The nitrogen is produced locally by compressing ambient air and separating nitrogen from said compressed air. The beverage preparation system comprises a bag-in-box beverage concentrate container fluidly connected to a diaphragm pump. The water is stored in a container that can be cooled. The container is fed with compressed nitrogen for pressing the water to a diaphragm pump that urges the water through a nitrogen mixer being for instance a liquid / gas contactor membrane unit. The nitrogen infused and cooled water is then mixed with the beverage concentrate at a mixing point that is upstream of a serving faucet or spout. The control of concentration of the concentrate in the water is by means of the two diaphragm pumps, one for the concentrate and one for the water. While this system and method are relatively simple in construction, they show limitations in the ability of the diaphragm pumps to finely control the dosage, notably when the concentrate shows a certain viscosity. Also, the degree of nitrogen infusion or dissolving in the beverage can also be impaired in that the post-mixing with the beverage concentrate might release some of the infused or dissolved nitrogen.Summary of inventionTechnical Problem

[0004] The invention has for technical problem to overcome at least one drawback of the above-mentioned prior art. More specifically, the invention has for technical problem to provide a system and a method for in-line preparing a gas-infused water-based beverage with an accurate dosage and satisfactory degree of gas infusion of the beverage.Technical solution

[0005] The invention is directed to a system for preparing a gas-infused waterbased beverage, comprising: a gas dissolver for dissolving gas, such as carbon dioxide, nitrogen or nitrogen contained in air, into water; a concentrate tank fluidly connected to a dosing pump; a mixing connectorwith an inlet for water, an inlet for the concentrate and an outlet for the water mixed with the concentrate; wherein the gas dissolver is arranged downstream of the mixing connector so as to dissolve gas into the water mixed with the concentrate.

[0006] According to a preferred embodiment, the system further comprises a constant flow pump fluidly connected between the mixing connector and the gas dissolver.

[0007] According to a preferred embodiment, the constant flow pump is a volumetric pump, preferably selected among the list: gear pump, vane pump, screw pump.

[0008] According to a preferred embodiment, the dosing pump is a peristaltic pump.

[0009] According to a preferred embodiment, the mixing connector comprises a check-valve at the water inlet and a check-valve at the concentrate inlet.

[0010] According to a preferred embodiment, the mixing connector comprises a body comprising: a water inlet port at the water inlet, a concentrate inlet port at the concentrate inlet and an outlet port at the outlet; and an internal passage with three branches connected to the water inlet port, the concentrate inlet port and the outlet port, respectively, and connecting to each other at a mixing area; and wherein the water inlet check-valve is located in the branch connected to the water inlet port, between the water inlet port and the mixing area, and the concentrate inlet check-valve is located in the branch connected to the concentrate inlet port, between the concentrate inlet port and the mixing area.

[0011] According to a preferred embodiment, at least one or each of the water inlet check-valve and the concentrate inlet check-valve comprises: a circular hollow body with an inner seat, housed in a bore of the corresponding branch; a shutter movable inside the circular hollow body; and a spring urging the shutter towards the inner seat.

[0012] According to a preferred embodiment, the body is a bloc of stainless steel or nickel-plated brass.

[0013] According to a preferred embodiment, the system further comprises: a water pressure regulator and a flow meter connected in series to the water inlet of the mixing connector; and a control unit electrically connected tothe flow meter, the dosing pump, and configured to controlling the dosing pump depending on the water flow measured by the flow meter.

[0014] According to a preferred embodiment, the constant flow pump operates such that, during normal operation, the pressure downstream of the constant flow pump is of at least 2 bar and the pressure upstream of the constant flow pump is of not more than 0.5 bar.

[0015] According to a preferred embodiment, the dosing pump is a peristaltic pump that is operated by the control unit in Pulse Width Modulation at a nominal voltage.

[0016] According to a preferred embodiment, the control unit operates the dosing pump with a correction parameter, curve or look-up table that compensates a deviation of the effective flow rate from a theoretical flow rate, due to a viscosity of the concentrate and / or of a rigidity of a flexible tube fitted in the peristaltic pump.

[0017] According to a preferred embodiment, the dosing pump is operatively coupled to an encoder electrically connected to the control unit configured for regulating the dosing pump based on operation of the dosing pump measured by the encoder.

[0018] According to a preferred embodiment, the operation of the dosing pump measured by the encoder is proportional to a flow rate of the concentrate through the dosing pump.

[0019] According to a preferred embodiment, the dissolver is a venturi mixer with an inlet for the water mixed with the concentrate, a gas inlet connected to a gas source, and an outlet connected to a serving spout.

[0020] According to a preferred embodiment, the gas source is an air compressor, a cylinder of compressed carbon dioxide or a cylinder of compressed nitrogen.

[0021] The invention is also directed to a method for in-line preparing a gas- infused water-based beverage, comprising the steps of: dissolving gas, such as carbon dioxide, nitrogen or nitrogen contained in air, into the water; and mixing a concentrate with the water; wherein mixing the concentrate with the water is done upstream of dissolving the gas into the water.

[0022] According to a preferred embodiment, the method further comprises using a constant flow pump fluidly between mixing the concentrate with the water and dissolving the gas into the water, in order to stabilize the pressure at said mixing to a lower value than the pressure at said dissolving.

[0023] The above-mentioned features of the system apply to the above method and vice versa.Advantages of the invention

[0024] The invention is particularly interesting in that it provides a system and a corresponding method for in-line preparing a gas-infused water-based beverage that are accurate in the concentrate dosage and providing a satisfactory degree of gas infusion in the beverage, while remaining simple in construction. The invention provides a pre-mixing of the water with the concentrate, before cooling and gas infusion. The pre-mixing is advantageous in that it allows a better control of the gas infusion, because said gas infusion is achieved in the already mixed beverage, meaning that there is no post-mixing likely to modify the degree of gas infusion. This is particularly true for beverages infused with nitrogen or nitrogen contained in air, showing a foamy aspect participating in the perceived quality thereof.

[0025] Pre-mixing the beverage is also advantageous in that it provides a better control of the mass flow rate of the water and thereby of the concentrate dosage. Controlling the mass flow rate of gas infused water based on volumetric measures, as this is usually done in in-line preparation systems, is indeed more difficult because depending on the amount of gas infused therein. Pre-mixing the beverage upstream of the cooling and gas dissolver / infuser is further advantageous in that it allows the freshly mixed beverage to homogenise before gas infusion.

[0026] The use of a constant volume pump between the mixing connector and the gas dissolver is particularly advantageous for stabilizing the pressure in the mixing connector, at a low level, promoting a controlled concentrate dosage by avoiding potentially varying backpressures.

[0027] The control of the dosing pump by PWM, by taking in account deviation from nominal correlation between non-viscous fluid flow rate and PWM duty cycle, and / or by using a regulation loop from an encoder operatively coupled to the dosing pump, are measures which increase the dosage accuracy.

[0028] The construction of the mixing connector, notably integrating check-valves, also promotes a proper function of the system.Brief description of the drawings

[0029] Figure 1 is a layout of the system for preparing a gas-infused water-based beverage, according to the invention.

[0030] Figure 2 is schematic plan view of the dosing pump of the system of figure 1.

[0031] Figure 3 is a graph illustrating the nominal correlation between the PWM rate of the dosing pump and the liquid flow rate versus the effective correlation with a viscous beverage concentrate.

[0032] Figure 4 is a sectional view of the mixing connector of the system of figure 1.

[0033] Figure 5 is perspective view of a beverage dispenser into which the system of figure 1 can be implemented.Description of an embodiment

[0034] Figure 1 is a layout of the system for preparing a gas-infused water-based beverage, according to the invention.

[0035] The system 2 comprises a water inlet 4 that can be connected to a water source such as a water tap or a pressurized water tank. It further comprises a regulator 6 that reduces or at least regulates the pressure of the water at its outlet. Downstream of the regulator 6 is connected a flow meter 8 and further downstream a mixing connector 10. As this is apparent in figure 1, the regulator 6, the flow meter 8 and the mixing connector 10 are arranged in series. The mixing connector 10 comprises a water inlet 10.1 connected to the outlet of the flow meter 8. It further comprises a beverage concentrate inlet 10.2 connected to a concentrate dosing pump12. The latter is connected to a not represented concentrate tank that can be, for instance, a bag-in-box. The mixing connector 10 further comprises an outlet 10.3. The mixing connector 10 comprises an internal passage (not visible) with three branches connected to the water inlet 10.1, the concentrate inlet 10.2 and the outlet 10.3, respectively, and connecting to each other at a mixing area (also not visible). This internal passage can be considered as a T- or Y-shaped passage.

[0036] As this is apparent the flow meter 8 is electrically connected to a control unit 14 (comprising a PCB carrying an electronic circuit and electronic components). The control unit 14 is fed with electrical power by the power supply 16 being itself connectable to a local power grid. The dosing pump 12 is also connected to the control unit 14. The latter is configured for controlling the dosing using based on the water flow rate measured by the flow meter 8. The flow meter is advantageously for the volumetric type i.e. , with a rotating wheel defining with the housing a given volume of flowing water per rotation, and with a sensor detecting or counting the rotations of said wheel. The electric signal produced by the flow meter is representative of the volumetric flow of water. That signal can be a signal whose voltage is proportional to the volumetric flow of water or a pulsed signal whose frequency is proportional to said volumetric flow of water.

[0037] The outlet 10.3 of the mixing connector 10 can be connected to a constant flow pump 18 before passing through a cooling device 20. The purpose of that constant flow pump 18 is to stabilize the pressure in the mixing connector 10 at a level that is lower than the pressure downstream of said constant flow pump 18, necessary for ensuring a proper gas infusion that will be described here after. That lower pressure level is advantageously below 0.5 bar. This is particularly advantageous for ensuring a stable mixing of the water with the concentrate at a stable and fixed ratio. The pressure downstream of the constant flow pump 18 is advantageously comprised between 2 and 2.5 bar.

[0038] The constant flow pump 18 is advantageously a volumetric pump i.e., a pump whose fluid displaced volume per rotation or cycle is constant. It isadvantageously a gear pump, a vane pump, a membrane pump or a screw pump.

[0039] The constant flow pump 18 can be electrically connected to the control unit 14 or to a specific controller (not represented) which can be a pressure switch, having a response time potentially shorter than the one of the control unit 14.

[0040] After leaving the cooler 20, the water-based beverage reaches a gas dissolver 22 for dissolving or infusing gas into the water-based beverage. The gas dissolver 22 is for instance a venturi mixer with a water inlet 22.1 for the water mixed with the concentrate, a gas inlet 22.2 connected to a gas source, and an outlet 22.3 connected to a serving spout (not represented). Such a venturi mixer is further detailed in the patent applications published WO 2022 / 214568 A1 , WO 2015 / 124590 A1 and WO 2009 / 021960 A1, of the same applicant, whose contents are incorporated by reference in their entirety. It basically comprises a main passage for the water, where said passage shows a venturi profile, and at least one lateral passage for the gas feeding radially into the main passage at the most reduced section portion thereof. The at least one lateral passage can be two opposed lateral passages being off-set relative to the main passage for forming a vortex inside said main passage. That venturi profile can be followed by a relaxation or mixing chamber into which the rapidly flowing water into which gas has been added can decelerate for promoting dissolving of the gas into the water.

[0041] The above-mentioned serving spout or faucet (not represented) can comprise, past the valve as such, a serving nozzle with a restrictor plate or disk provided with several holes, preferably evenly distributed along a circle centred with said disk. The nozzle can also comprises a flow straightener located directly downstream of the restrictor plate or disk.

[0042] The gas is fed to the gas dissolver 22 through a connection line that can comprise an adjustable flow restrictor 24. The latter can be adjusted, for instance manually, for modifying the degree of gas dissolved or infused in the water-based beverage. The gas source is for instance compressed air which comprises about 80% of nitrogen. The air is for instancecompressed on demand by the compressor 26 whose operation can be controlled by the pressure switch 28. The latter can be fluidly connected to the fluid line connecting the compressor 26 to the gas dissolver 22, so that once the pressure in the line falls below a given lower limit e.g., 1.5 bar, the switch goes on and runs the compressor 26. Once the pressure in the fluid line reaches an upper limit e.g., 2.5-3.0 bar, the switch goes off and stops the compressor 26.

[0043] As this is apparent the system 2 can comprise a first outlet 30 for nitrogen infused mixed beverage and a second outlet 32 by-passing the gas dissolver 22, for mixed beverage that is not infused with nitrogen. Each of these two outlets 30 and 32 can be provided with a dispensing tap or faucet e.g. for the conical flow restrictor type that is commonly used for foamy drinks like beer.

[0044] As this is apparent the system 2 is provided with an AC power supply line e.g. of 115 or 230 Volt, supplying electrical power to the power supply 16 and to a cooling system 34 that is operatively connected (not represented) to the cooler 20.

[0045] The control unit 14 can be provided with a manual adjustment means of the dosage, for example a potentiometer, for finely adjusting the dosage. This manual adjustment means can be configured for adjusting by the predetermined dosage ratio within a range of ±10%.

[0046] The predetermined dosage ratio between the concentrate and the water can be comprised between 1 :5 to 1 :10, preferably of about 1 :7.

[0047] Figure 2 is a schematic plan view of the dosing pump 12 of the system 2 of figure 1. The dosing pump 12 is advantageously a peristaltic pump with a circular cavity 12.1 receiving a hose 12.2 depicting a circular shape in said cavity, and a rotor 12.3 in said cavity 12.1, carrying at least one roller 12.4 that presses the hose 12.2. against the cavity 12.1. Rotation of the rotor 12.3 causes a circular displacement of the roller(s) 12.4 against and along the hose 12.2, thereby forcing the fluid located in said hose to move in the same direction as the roller(s). The rotor 12.3 comprises advantageously at least two, more advantageously at least three rollers 12.4, distributedevenly around the rotor, for promoting a constant flow with limited flow irregularities or pulses inherent of peristaltic pumps. The hose 12.2 can comprise, at its two ends, connectors 12.5 that engage in the housing 12.6 of the peristaltic pump 12. Such a configuration is particularly advantageous when working with food concentrates that require regular cleaning and replacement of parts in contact therewith.

[0048] The dosing pump, being advantageously a peristaltic pump, can be driven and controlled by Pulse-Width Modulation (PWM) at a nominal voltage instead of by applying a variable voltage. PWM is useful for controlling the average power or amplitude delivered by an electrical signal. The average value of voltage (and current) fed to the load is controlled by switching the supply between 0 and 100% at a rate faster than it takes the load to change significantly. PWM is particularly suited for running inertial loads such as motors, which are not as easily affected by this discrete switching. It has been found that a switching frequency comprised between 5 and 100 Hz is particularly adapted for the instant application. Also, the duty cycle can be comprised 0 and 100%. It is advantageous to drive the dosing pump by PWM at a nominal voltage in that the torque generated by the electric motor of the dosing pump is at its nominal value and thereby known and better controlled. It allows the dosing pump to operate according to a linear correlation between the duty cycle of the PWM and the flow rate, at least for a non-viscous liquid like water. However, since the beverage concentrate to be mixed with water can in some instances be viscous i.e. , show a viscosity that is substantially higher than water, the effective correlation between the duty cycle and the flow rate might deviate from the one for non-viscous liquids.

[0049] Figure 3 is a graph illustrating the nominal correlation between the PWM duty cycle of the dosing pump and the liquid flow rate versus the effective correlation with a viscous beverage concentrate. The continuous line corresponds to the nominal correlation for non-viscous liquids like water, whereas the dashed line corresponds to the effective correlation for a beverage concentrate showing a viscosity of about 8 Pa s which is higher than the viscosity of water at 20°C, being of about 0.001 Pa s. Thedeviation between the effective correlation and the nominal one is essentially at partial loads i.e. with duty cycle comprised between 10 and 50%. It is however to be noted that the above-described graph and behaviour can be specific for each concentrate, depending essentially on its viscosity, and specific to the flexible tube operatively fitted in the peristaltic pump, through which the concentrate flows, featuring a specific rigidity. It has been found out to be particularly advantageous to proceed to such measures with one or several concentrates and / or several flexible tubes, and to record the measured deviations, for example by modelling and / or parametrizing with values, curves and / or look-up tables, and to take then into account in the determination of the duty cycle to apply to the dosing pump.

[0050] The control unit 14, as illustrated in figure 1, is programmed to control the dosing pump 12 in order to mix the concentrate at a predetermined ratio, based on the electrical signal provided by the flow meter 8, representative of the water flow rate. The control of the dosing pump consists in determining the frequency and the duty cycle of the electrical signal fed to the dosing pump 12, based on the electrical signal provided by the flow meter 8 and advantageously the above deviation model and / or parameters for the concentrate or at least the viscosity of the concentrate used. It has been found that this provides an accurate mixing ratio between the water and the concentrate.

[0051] However, since the mixing ratio accuracy is of utmost importance, it has been further investigated for further improving the accuracy. As a result, an encoder 12.1 can be operatively coupled to the dosing pump 12, for instance to the shaft of its electric motor or the shaft driving the moving part(s) driving the volumetric chamber of the dosing pump that moves the fluid. Such an encoder 12.1 is then electrically connected to the control unit 14 for providing an electric signal representative of the effective rotation or duty cycle of the dosing pump. The control unit 14 can thereby be configured, for instance programmed, for regulating the movement of the dosing pump, for instance its rotation, with a feedback loop from the encoder. The control unit 14, based on the signal received from the flowmeter 8, determines the concentrate flow rate to be outputted and thereby the speed of the dosing pump. Based on the above considerations, notably the correlation between the flow rate and the PWM duty cycle, the control unit 14 determines the theoretical PWM duty cycle to be fed to the dosing pump. The feedback loop from the encoder provides a signal representative of the speed of the dosing pump and allows the control unit 14 to correct the theoretically determined PWM duty cycle for achieving the desired speed and therefore the desired concentrate flow rate.

[0052] Figure 4 is a sectional view of the mixing connector 10 of the system of figure 1.

[0053] As this is apparent, the mixing connector 10 comprises a body 10.4 provided with the water inlet port 10.1, the concentrate inlet port 10.2 and the outlet port 10.3; and an internal passage 10.5 with three branches connected to the water inlet port 10.1, the concentrate inlet port 10.2 and the outlet port 10.3, respectively, and connecting to each other at a mixing area, located at the crossing area of the three branched. Also, a water inlet check-valve 10.6 can be located in the branch connected to the water inlet port 10.1, between the water inlet port 10.1 and the mixing area, and a concentrate inlet check-valve 10.7 can be located in the branch connected to the concentrate inlet port 10.2, between the concentrate inlet port 10.2 and the mixing area.

[0054] The presence of the water inlet check-valve 10.6 and of the concentrate inlet check-valve 10.7 is advantageous in that it prevents any backflow of fluid towards the flow meter 8 and the dosing pump 12 (figure 1). These check-valves 10.6 and 10.7 are advantageously located insider the body of the mixing connector i.e., downstream of the water inlet port 10.1 and concentrate inlet port 10.2, respectively, to avoid notably any bacterial contamination of the water line by the concentrate.

[0055] Each of the water inlet check-valve 10.6 and the concentrate inlet checkvalve 10.7 comprises a circular hollow body with an inner seat, housed in a bore of the corresponding branch, a shutter movable inside the circular hollow body, and a spring urging the shutter towards the inner seat, for instance towards the water inlet port 10.1 and the concentrate inlet port10.2, respectively. As this is also apparent, each shutter can comprise a central guiding pin slidingly extending through a bottom wall of the circular hollow body. The spring is located between said bottom wall and the main part of the shutter, around the guiding pin. The circular hollow body can be provided with an outer thread that engages with a corresponding inner thread formed in a corresponding bore in the corresponding branch of the internal passage 10.5. The circular hollow body can be provided with an outer circular groove receiving a gasket, such as an O-ring, that engages in a liquid tight fashion with said bore.

[0056] The body 10.4 of the mixing connector 10 is advantageously made of stainless steel or nickel-plated brass, notably to avoid contact between the concentrate a fixed plastic part of the system. The same applies to the concentrate check-valve 10.7. Such a contact with a plastic part of the system could, over time, contaminate the plastic part, requiring a thorough cleaning. The hose line connecting the concentrate source to the mixing connector 10 is to be cleaned and / or replaced regularly.

[0057] Figure 5 is perspective view of a beverage dispenser into which the system of figure 1 can be implemented.

[0058] The beverage dispenser 36 is of the cabinet type, for dispensing in-line mixed beverages, to be placed on a table or a bar counter. The cabinet houses the system 2 illustrated in figure 1. The concentrate tank, like a bag-in-box, can be located in the cabinet. The cabinet comprises, preferably at a rear area, a port for the water source, like a tap water line. The beverage dispenser 36 comprises for instance two serving faucets 38, preferably of the conical flow restrictor type such as those used for serving foamy drinks like beer. One of the serving faucets 38 can be connected to the first outlet 30 for nitrogen infused mixed beverage (figure 1) and the other serving faucet 38 can be connected to the second outlet 32 bypassing the dissolver 22, for mixed beverage that is not infused with nitrogen (figure 1 ).

Claims

Claims1. A system (2) for preparing a gas-infused water-based beverage, comprising:a gas dissolver (22) for dissolving gas, such as carbon dioxide, nitrogen or nitrogen contained in air, into water;a concentrate tank fluidly connected to a dosing pump (12);a mixing connector (10) with an inlet (10.1) for water, an inlet (10.2) for the concentrate and an outlet (10.3) for the water mixed with the concentrate;wherein the gas dissolver (22) is arranged downstream of the mixing connector (10) so as to dissolve gas into the water mixed with the concentrate;characterized in that the system (2) further comprises:a constant flow pump (18) fluidly connected between the mixing connector (10) and the gas dissolver (22).

2. The system (2) of claim 1, wherein the constant flow pump (18) is a volumetric pump, preferably selected among the list: gear pump, vane pump, membrane pump, screw pump.

3. The system (2) of any one of claims 1 and 2, wherein the dosing pump (12) is a peristaltic pump.

4. The system (2) of any one of claims 1 to 3, wherein the mixing connector (10) comprises a check-valve (10.6) at the water inlet (10.1) and a check-valve (10.7) at the concentrate inlet (10.2).

5. The system (2) of claim 4, wherein the mixing connector (10) comprises a body (10.4) comprising:a water inlet port, a concentrate inlet port and an outlet port; andan internal passage (10.5) with three branches connected to the water inlet port, the concentrate inlet port and the outlet port, respectively, and connecting to each other at a mixing area; andwherein the water inlet check-valve (10.6) is located in the branch connected to the water inlet port, between the water inlet port and the mixing area, and the concentrate inlet check-valve (10.7) is located in the branch connected to the concentrate inlet port, between the concentrate inlet port and the mixing area.

6. The system (2) of claim 5, wherein at least one or each of the water inlet check-valve (10.6) and the concentrate inlet check-valve (10.7) comprises:a circular hollow body with an inner seat, housed in a bore of the corresponding branch;a shutter movable inside the circular hollow body; anda spring urging the shutter towards the inner seat.

7. The system (2) of one of claims 5 and 6, wherein the body (10.4) is a bloc of stainless steel or nickel-plated brass.

8. The system (2) of any one of claims 1 to 7, further comprising:a water pressure regulator (6) and a flow meter (8) connected in series to the water inlet (10.1) of the mixing connector (10); anda control unit (14) electrically connected to the flow meter (8), the dosing pump (12), and configured for controlling the dosing pump (12) depending on the water flow measured by the flow meter (8).

9. The system (2) of one of claims 1-2, and of claim 8, wherein the constant flow pump (18) operates such that, in normal operation condition, the pressure downstream of the constant flow pump (18) is of at least 2 bar and the pressure upstream of the constant flow pump (18) is of not more than 0.5 bar.

10. The system (2) of one of claims 8 and 9, wherein the dosing pump (12) is a peristaltic pump that is operated by the control unit (14) in Pulse Width Modulation at a nominal voltage.

11. The system (2) of claim 10, wherein the control unit (14) operates the dosing pump (12) with a correction parameter, curve or look-up table that compensates a deviation of the effective flow rate from a theoretical flow rate, due to a viscosity of the concentrate and / or of a rigidity of a flexible tube fitted in the peristaltic pump (12).

12. The system (2) of any one of claims 8 to 11, wherein the dosing pump (12) is operatively coupled to an encoder (12.1) electrically connected to the control unit (14) configured for regulating the dosing pump (12) based on operation of the dosing pump (12) measured by the encoder.

13. The system (2) of claim 12, wherein the operation of the dosing pump (12) measured by the encoder (12.1) is proportional to a flow rate of the concentrate through the dosing pump (12).

14. The system (2) of any one of claims 1 to 13, wherein the gas dissolver (22) is a venturi mixer with an inlet (22.1) for the water mixed with the concentrate, a gas inlet (22.2) connected to a gas source, and an outlet (22.39 connected to a serving spout (38).

15. The system (2) of claim 14, wherein the gas source is an air compressor (26), a cylinder of compressed carbon dioxide or a cylinder of compressed nitrogen.

16. A method for in-line preparing a gas-infused water-based beverage, comprising the steps of:dissolving gas, such as carbon dioxide, nitrogen or nitrogen contained in air, into the water; andmixing a concentrate with the water upstream of dissolving the gas into the water;characterized in that the method further comprisesusing a constant flow pump (18) fluidly between mixing the concentrate with the water and dissolving the gas into the water, in order to stabilize the pressure at said mixing to a lower value than the pressure at said dissolving.

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