Beverage vending machine

Abstract

A beverage vending machine (1 ) comprising a main water tank (12) having a volume V 1; a water heater (3); a water pump (16) to supply the water heater (3) with water from the main tank (12); a. beverage dispensing unit (4) designed to receive hot water from the water heater (3) in order to prepare and dispense beverages; a hydraulic circuit (7) to fluidly connect the main water tank (12), the water pump (16), the water heater (3) and the beverage dispensing unit (4) to each other and comprising a water recirculation branch (11) to recirculate the hot water flowing out of the water heater (3) back into the hydraulic circuit (7) and recirculate it through the water heater (3); a recirculation valve device (28) arranged downstream of an outlet of the water heater (3) to selectively supply hot water to either the recirculation branch (11) or the beverage dispensing unit (4); wherein the water recirculation branch (11) extends between the recirculation valve device (28) and an emanation point (32) of the hydraulic circuit (7) arranged downstream of the main water tank (12), in a water flowing direction along the hydraulic circuit (7), so as to form a closed water recirculation loop; and the hydraulic circuit (7) further comprises a water recirculation tank (31) having a volume V2 less than the volume VI and arranged downstream of said emanation point (32).

Description

[0001] BEVERAGE VENDING MACHINE

[0002] Cross Reference to Correlated Patent Applications

[0003] This patent application claims priority to European patent applications No. 24152644.1 filed on January 18, 2024 and No. 24172966.4 filed on April 29, 2024 and Italian patent application No. 102025000000810 filed on January 17, 2025, the entire disclosures of which is incorporated herein by reference.

[0004] Technical Field of the Invention

[0005] The invention relates to a beverage vending machine.

[0006] State of the Art

[0007] In beverage vending machines, flow-through or continuous-flow water heaters, also known as instantaneous water heaters, are used to heal water to be supplied to a beverage dispensing unit. An instantaneous water heater is part of a hydraulic circuit, which normally comprises a water storage tank supplied with cold waler coming from a water supply network and a water pump, which draws water from the water storage tank and supplies it to the instantaneous water healer.

[0008] The advantages arising from the use of instantaneous water heaters compared to traditional water storage boilers are well known and mainly consist in energy savings deriving from not having to keep a large volume of water hot, in smaller sizes and in the possibility of customising the outlet water temperature on demand depending on the selected beverage.

[0009] Although they are undoubtedly effective, instantaneous water heaters nevertheless have some operating limits deriving from the fact that instantaneous heating of water needed, with a certain flow' rate, for producing a large part of the beverages, in particular beverages produced from soluble substances, would require an instantaneous electrical power that is greater than that normally used in systems with water storage boilers, thus introducing greater limits to the electrical power available on site. On the other hand, the use of instantaneous water heaters with very high powers would lead to difficulties in controlling the dispensing temperature and to greater limits to the management of electrical disturbances (flickers).

[0010] In order to overcome these limits, it is known to provide the hydraulic circuit, between the instantaneous water heater and the beverage dispensing unit, with a valve device designed to supply water flowing out of the instantaneous water heater to a water recirculation branch in case the temperature of the water at the outlet of the instantaneous water heaters is not at a predetermined temperature, so that water does not reach the beverage dispensing unit, but returns to the water storage tank, where it is mixed with colder water, thus increasing temperature thereof. In this way, water is recirculated through the instantaneous water heater several times until the temperature of the water at the outlet thereof reaches the predetermined temperature and hot water can be supplied to the beverage di spensing unit.

[0011] A hydraulic circuit with a recirculation branch of the type described above is known, for example, from EP 2 642 906 B l and EP 2 895 039 Bl.

[0012] However, these circuits suffer from the drawback of requiring the temperature of the entire volume of water in the storage tank to be raised in order to reduce the temperature differential between the inlet and outlet of the instantaneous water heater, with consequent energy waste, increased dispensing times and problems related to a greater formation of lime scale inside the storage tank.

[0013] In order to overcome this drawback, EP 1 097663 B 1 discloses a water recirculation branch, which does not flow' into the storage tank, but into an emanation point of the hydraulic circuit downstream of the storage tank. The Applicant has however found that this solution is scarcely effective, as the volume of water heated in the water recirculation branch is significantly smaller than the amount of water needed for preparing a beverage.

[0014] Subject-matter and Summary of the Invention

[0015] The object of the invention is to provide a beverage vending machine, which uses an instantaneous water heater which allows the aforementioned drawbacks to be overcome.

[0016] According to the invention, a beverage vending machine is provided, as claimed in the appended claims.

[0017] Brief Description of the Drawings

[0018] Figure 1 schematically show's a beverage vending machine according to a first embodiment of the invention;

[0019] Figure 2 schematically shows a beverage vending machine according to a second embodiment of the invention; and

[0020] Figure 3 schematically shows a beverage vending machine according to a third embodiment of the invention.

[0021] Figure 4 schematically show's a beverage vending machine according to a fourth embodiment of the invention. Detailed Description of Preferred Embodiments of the Invention

[0022] The invention is described in detail with reference to the accompanying Figures, so as to allow a person skilled in the art to carry it out and to use it. Possible changes to the embodiments described herein will be immediately evident to skilled people and the generic principles described herein can be applied to other embodiments and applications without for this reason going beyond the scope of protection of the invention set forth in the appended claims. Therefore, the invention cannot be considered as limited to the embodiments described and shown herein, but it has to be associated with the widest scope of protection possible in accordance with the principles and the features described and claimed herein.

[0023] In Figure 1, reference numeral 1 schematically indicates, as a whole, a beverage vending machine.

[0024] The beverage vending machine 1 comprises a water inlet connected to a water supply network through a measuring solenoid valve 2; a water heater 3; and a beverage dispensing unit 4.

[0025] The water heater 3 belongs to the category of flow-through or continuous-flow heaters, also known as instantaneous heaters, namely heaters without a tank and designed to raise a temperature of the water while it flows through the heater itself.

[0026] The water heater 3 can be manufactured according to any one of the known types of instantaneous heaters, such as, for example, induction heaters, thick film heaters, thermoblock heaters, in which water to be heated is caused to flow' along a duct formed in, or integral to, a metal block heated by one or more electrical resistors embedded in the metal block.

[0027] In the example shown herein, the beverage dispensing unit 4 comprises a plurality of known beverage dispensing devices designed to dispense respective types of hot beverages, for example coffee, hot chocolate, tea or the like, into a beverage container 6.

[0028] Conveniently, the beverage dispensing devices comprise mixing devices 5a (known per se), each of which is designed to receive water from the water heater 3, to mix water with a powder product fed into the mixing device 5a and to dispense a relative hot beverage, and a brewing unit 5b (known per se) designed to produce beverages bybrewing an amount of powder or leaf material with pressurised hot water.

[0029] The beverage vending machine 1 further comprises a hydraulic circuit 7 with a plurality of devices and pipes and comprising a first circuit section 8, which fluidly connects the solenoid valve 2 to the water heater 3, a second circuit section 9, which fluidly connects the water heater 3 to the beverage dispensing unit 4, a third circuit section 10, which connects the beverage dispensing unit 4 to the beverage container 6, and a fourth circuit section, which defines a water recirculation branch 11 having the function, as described more in detail below, of recirculating water one or more times through the water heater 3 until the desired temperature of the water is reached.

[0030] The first circuit section 8 comprises a water storage tank 12 having a given volume VI, a water supply duct 13 coming from the solenoid valve 2 and a water overflow duct 14 extending between the water storage tank 12 and the solenoid valve 2.

[0031] Conveniently, the water storage tank 12 defines a so-called “air break” tank of a known type and commonly used in beverage vending machines to prevent water supplied to the water heater 3 from backflowing into the water supply network. The “air break” tank is also used as a water reserve to ensure that, in the event of a sudden interruption of the supply of water from the water supply network, the beverage vending machine 1 has the necessary autonomy to complete a beverage production cycle and, if necessary, carry out other cycles using the volume of water V I inside the “air break” tank.

[0032] To keep the water volume VI constant, the water storage tank 12 is normally provided with a water level maintenance device (not shown), for example a float with a microswitch, which is connected to an electronic control unit 15 of the beverage vending machine 1 configured to selectively control operation of the solenoid valve 2 based on an output of the level maintenance device.

[0033] The first circuit section 8 further comprises a water supply pump 16 connected to the water storage tank 12 through a suction duct 17 and to the water heater 3 through a delivery duct 18. Along the suction duct 17 a volumetric flow meter 19 is arranged to measure the amount of water that the water pump 16 supplies to the water heater 3 and, hence, to the beverage dispensing unit 4.

[0034] The first circuit section 8 further comprises an overpressure duct 20 for recirculating water in the suction duct 17, when the water pressure at the outlet of the water pump 16 is greater than a given threshold value.

[0035] The second circuit section 9, which fluidly connects the water heater 3 to the beverage dispensing unit 4, comprises a valve unit 21 comprising a plurality of solenoid valves 22 arranged to selectively receive pressurised hot water from a supply duct 24 connected to the outlet of the water heater 3 in order to supply it to a respective device 5a or 5b through a respective supply duct 23.

[0036] Preferably, the solenoid valves 22 are arranged adjacent to one another to result in the valve unit 21 forming a single compact assembly, wherein inlets of the solenoid valves 22 are connected, in parallel to one another, to a supply manifold (not shown), which, from the functional point of view, can be considered as an extension of the supply duct 24, and outlets of the solenoid valves 21 are each connected to the respective device 5a or 5b via the respective supply duct 23.

[0037] Conveniently, the valve unit 21, more precisely the manifold, is also fluidly connected to a waste water collecting container 25 via a respective discharge duct 26.

[0038] For more details on this embodiment of the valve unit 21, reference can be made to WO 2018 / 220552 Al in the name of the Applicant.

[0039] The third circuit section 10, which connects the beverage dispensing unit 4 to the beverage container 6, comprises, for each device 5a, 5b, a respective dispensing duct 27 extending between the beverage container 6 and the device 5a, 5b itself.

[0040] The fourth circuit section, namely the aforementioned water recirculation branch 11, extends between the second circuit section 9 and the suction duct 17 so as to allow the water flowing out of the water heater 3 not to flow into the third circuit section 10, when it is supplied to the water recirculation branch 11 , but to flow again into the first circuit section 8, downstream of the tank 12.

[0041] The supply of pressurised hot water to the recirculation branch 11 is controlled by a recirculation solenoid valve 28 connected to the electronic control unit 15 to selectively establish a fluid communication between the supply duct 24 and the recirculation branch

[0042] Preferably, the recirculation solenoid valve 28 is part of the compact valve unit 21 and is arranged adjacent, and in parallel, to the solenoid valves 22 at an end of the manifold, in the water flow direction. In this embodiment, the solenoid valve 28 is a two- way valve, whose inlet fluidly communicates with the manifold, namely with the supply duct 24, and whose outlet fluidly communicates with the recirculation branch 11.

[0043] The particular compact configuration of the valve unit 21 described above, together with the position of the recirculation solenoid valve 28 in the valve unit 21, has the advantage of allowing the entire valve unit 21 to be heated, when the temperature at the outlet of the water heater 3 does not reach the predetermined value and water recirculation is activated.

[0044] Indeed, in this case, when the electronic control unit 15 causes the solenoid valves 22 to close and the recirculation solenoid valve 28 to open so as to cause the hot water coming from the water heater 3 not to flow to the beverage dispensing unit 4, but to the water recirculation branch 11, the water, before reaching the recirculation solenoid valve 28 and flowing into the recirculation branch 11, flows through the entire manifold, thus heating the latter and the group of solenoid valves 22. In a variant not shown, the recirculation solenoid valve 28 is a three-way valve arranged upstream of the valve unit 21, along the supply duct 24.

[0045] In order to measure water temperature, the water heater 3 is provided with at least one temperature probe 29, conveniently an NTC thermistor, arranged at the water outlet of the water heater 3 and connected to the electronic control unit 15.

[0046] Preferably, the water heater 3 is provided with a further temperature probe 30, conveniently an NTC thermistor, arranged at the water inlet of the water heater 3 and connected to the electronic control unit 15.

[0047] As shown in Figure 1, the hydraulic circuit 7 further comprises a second water tank 31 having a volume V2 smaller than the volume VI of the water storage tank 12 and arranged downstream thereof and of an emanation point 32, where the recirculation branch 11 ends and opens into the suction duct 17. Therefore, the water tank 31 is arranged so as to be included in a closed recirculation loop formed by the recirculation branch 11, the first circuit section 8 and the second circuit section 9, so as to allow the water that flows out of the water heater 3 and does not reach the predetermined temperature to be pumped by the water pump 16 to flow again through the heater 3 for number of times necessary to reach the predetermined temperature.

[0048] Hence, the water tank 31 defines a “flow-through” water tank, which is filled with water flowing in the closed recirculation loop when water recirculation is activated.

[0049] A “flow'-through” water tank with a reduced volume, such as the waler tank 31, allows numerous advantages to be achieved compared to known solutions, in which the recirculation branch flows into a “storage” water tank with a significantly greater capacity than the water tank 31, such as, for example, the water tank 12.

[0050] Indeed, the reduced volume V2 of the water tank 31 results in a smaller volume of water that needs to be heated during the recirculation to achieve the required increase in the temperature of the hot water and this greatly reduces the preheating time needed by the water heater 3 to be ready to dispense and, therefore, the waiting time of a user for the preparation of a beverage.

[0051] Furthermore, the “flow -through” arrangement of the water tank 31 significantly mitigates the effects of thermal stratification, which would otherwise occur inside a larger water storage tank and which would further lengthen the water preheating time and make the outlet temperature less precise.

[0052] Furthermore, given the need for adequate thermal insulation of the water tank into which the water to be preheated is supplied, the water tank 31 is significantly more advantageous both from the cost-related point of view and from the thermal dispersion point of view, given its small size, compared to a larger water storage tank, such as the water tank 12.

[0053] Preferably, the water tank 31 has a volume V2 commensurate with the water requirement for preparing a beverage.

[0054] Conveniently, the volume V2 is in the order of 100 cc, namely three times smaller than the volume of the water tank 12, which normally in of the order of 300 cc.

[0055] In the embodiment shown in Figure 1, the water tank 31 is arranged between the emanation point 32 and the water pump 16. Preferably, the water tank 31 is arranged between the emanation point 32 and the volumetric flowmeter 19.

[0056] According to other embodiments which are not shown herein, the water tank 31 can be arranged in any other point of the recirculation loop.

[0057] In the embodiments shown in Figures 2 and 3, the water tank 31 is integrated in the water heater 3. In particular, in this embodiments, the water heater 3 comprises a tubular insert 33 having, on its outer surface, a helical crest 34 and a cylindrical sleeve 35 coaxial to the tubular insert 33 and fitted thereon in contact with the helical crest 34 so as to delimit, with the tubular insert 33, a helical channel 36 for the passage of water.

[0058] The sleeve 35 defines the support for a heating element. Conveniently, the heating element is of the known thick film type and, hence, it will not be further described.

[0059] The tubular insert 33 has an internal cavity, which is closed, at one end, by a cap 37 and, at an opposite end, by a transverse wall 38, preferably formed as one single piece together with the tubular insert 33, in which two holes are formed, which define a water inlet 39 and a water outlet 40 of the water heater 3. Two seats are formed in the transverse wall 38 at the water outlet 40 and at the water inlet 39 to accommodate the temperature probe 29, which measures the temperature of the hot water flowing out of the water heater 3, and the temperature probe 30, which measures the temperature of the hot water flowing into the water heater 3, respectively.

[0060] The internal cavity of the tubular' insert 33 defines the water tank 31 and fluidly communicates with the helical channel 36 in a series arrangement.

[0061] In particular, in the embodiment shown in Figure 2, the tubular insert 34 has, in the transverse wall 38, a duct 41 , which establishes a fluid communication between the water inlet 39 and the water tank 31, and a duct 42, which establishes a fluid communication between the helical channel 36 and the water outlet 40 of the water heater 3.

[0062] At the end opposite the transverse wall 38, the tubular insert 34 has a through hole 43, which establishes a fluid communication between the water tank 31 and the helical channel 36. In use, the water flowing into the water heater 3 through the water inlet 39 first flows into the water tank 31 through the duct 41, then flows out of the water tank 31 and flows into the helical channel 36 through the hole 43 and finally flow's out of the helical channel 36 through the duct 42 and flows out of the water heater 3 through the water outlet 40.

[0063] In this configuration, therefore, the water tank 31 is arranged in series and upstream of the water heater 3, in the flowing direction of the water supplied by the water pump 16. As a result, in this configuration, the water contained in the water tank 31 is preheated only to the extent to which it helps reduce the temperature difference to a value compatible with the power available from the thick film heating element and the required dispensing temperature. This type of configuration focuses on energy efficiency, but requires a more complicated HW and SW control to manage outlet temperatures at low flow rates.

[0064] In the embodiment of Figure 3, the duct 41 establishes a fluid communication between the water inlet 39 of the water heater 3 and the helical channel 36 and the duct 42 establishes a fluid communication between the water tank 31 and the water outlet 40 of the water heater 3.

[0065] At the end opposite the transverse wall 38, the hole 43 establishes a fluid communication between the water tank 31 and the helical channel 36.

[0066] In use, the water flowing into the water heater 3 through the water inlet 39 first flows into the helical channel 36 through the duct 41, then flow's out of the helical channel 36 and flows into the water tank 31 through the hole 43 and finally flow's into the duct 42 and flows out of the water heater 3 through the water outlet 40.

[0067] In this configuration, therefore, the water tank 31 is arranged in series and downstream of the water heater 3. As a result, in this configuration, the water contained in the water tank 31 is brought all to the dispensing temperature before supplying the hot water to the beverage dispensing unit 4, thus improving the accuracy of the outlet temperature at low' flow rates or for low quantities to the detriment of a possible lower efficiency due to greater dispersion and a longer preheating time.

[0068] Both embodiments of Figures 2 and 3 lead to significant advantages deriving both from the integration of the water tank 31 in the w'ater heater 3, which entails a simplification of the hydraulic circuit 7 and a reduction in the overall dimensions, and from the structure of the water heater 3 itself and the use of a thick film heating element. Indeed, the water heater 3 of Figures 2 and 3 not only benefits from all the advantages typical of thick film elements, such as the reduced mass of the power element and the rapidity of response to heating and cooling, but also exceeds the limits of serviceability normally connected to water heaters using such heating elements, since the water heater 3 is fully inspectable.

[0069] Furthermore, the arrangement of the water tank 31 inside the helical heating channel 36 reduces part of the dispersion of the residual energy because, by recirculating the water for a few seconds at the end of the dispensing, this energy is recovered in the water tank 31 located on the inside of the heating element.

[0070] Figure 4 shows an alternative embodiment, in which the water tank 12 is absent and the pump 16 is directly supplied with the water coming from the water supply network.

[0071] In this embodiment, the water tank 31 is arranged on the delivery side of the water pump 16.

[0072] The beverage vending machine 1 finally comprises an anti-scale device configured to counter the formation of limescale inside the instantaneous water heater 3 and in the other components and ducts forming the hydraulic circuit 7.

[0073] The harmful action of limescale deposits is, as it is known, particularly burdensome in the event of use of an instantaneous water heater, since the high concentrated power and the small dimensions of the water passages can quickly lead to a reduction in the efficiency of the water heater, up to the complete obstruction of the water passages and to the consequent shutdown of the water heater.

[0074] The anti-scale device according to the present invention consists of a magnetic antiscale device 44, namely a device, known per se, which, through an induced magnetic field, has the effect of ionising the water in such a way that the calcium carbonate molecules dissolved in the water cannot aggregate into crystals and form the limestone, but remain suspended in smaller crystals in the form of aragonite.

[0075] Compared to a traditional softener filter of a known type, a magnetic anti-scale device has several advantages:

[0076] • it is economically advantageous because it does not get exhausted with use and, therefore, does not require a periodic replacement like traditional softener filters;

[0077] ® it does not alter the pH of the water, as is the case with traditional softener filters when the hardness of the water is reduced too much;

[0078] • it does not alter the taste of the drinks, as is the case with traditional softener filters.

[0079] The magnetic anti-scale device 44 can be arranged in any point of the hydraulic circuit 7, but it is conveniently arranged in a point of the closed water recirculation loop. This arrangement helps overcome some application limits connected to magnetic antiscale devices and lying in the fact that the ‘"magnetic conditioning” usually works well only in a narrow range of flow rates and could lose its effectiveness in case of low flow' rates (such as, for example, the typical flow rates of espresso drinks) and, above all, it tends to fade over time, allowing calcium carbonate molecules to aggregate and form limescale, if water is not caused to flow' through the magnetic filter again, as can be the case, for example, in the event that the beverage vending machine does not dispense beverages a given amount of time.

[0080] The positioning of the magnetic anti-scale device 44 inside the recirculation loop helps overcome these limits that w'ould arise, instead, if the magnetic anti-scale device 44 were arranged upstream of the solenoid valve 2 that controls the flow of water into the water tank 12. In fact, if the magnetic anti-scale device 44 is arranged along the recirculation loop, the water is conditioned every time a selection is made and not only upon activation of the water inlet solenoid valve 2; besides, the water is treated at its maximum useful flow rate and the effect of the magnetic conditioning is multiplied because water flow's through the magnetic anti-scale device 44 several times.

[0081] Furthermore, the positioning of the magnetic anti-scale device 44 in the water recirculation loop makes it possible to treat the water periodically even during the inactivity phases of the beverage vending machine in order to compensate for the loss of ionization over time by means of a periodic reactivation of the water recirculation, without activating the heating elements of the w'ater heater 3.

[0082] Advantageously, the reactivation of the recirculation, without heating, can also be carried out at the end of each dispensing phase so as to reduce the temperature inside the helical channel 36 of the water heater 3 thanks to the redistribution of the residual hot water over the entire recirculation loop and the water tank 31. The reactivation of the recirculation, without heating, at the end of each dispensing phase entails, therefore, a further improvement in the reduction of limescale, both because the lower temperatures inside the helical channel 36 of the water heater 3 forbid the formation and precipitation of limescale and because the reactivation of the recirculation causes the water to flow through the magnetic anti-scale device 44 again.

Claims

CLAIMS1. A beverage vending machine (1 ) comprising: a main water tank (12) having a volume VI; a water heater (3) in the form of an instantaneous flow heater; a water pump (16) to supply the water heater (3) with water from the main tank (12); a beverage dispensing unit (4) to receive hot water from the water heater (3) and prepare and dispense beverages; a hydraulic circuit (7) to fluidically connect the main water tank (12), the water pump (16), the water heater (3) and the beverage dispensing unit (4) to each other, and comprising a water recirculation branch (11) to recirculate the hot water flowing out of the water heater (3) back into the hydraulic circuit (7) and recirculate it through the water heater (3); a water recirculation valve device (28) arranged downstream of an outlet of the water heater (3) to selectively supply hot water to either the water recirculation branch (11) or the beverage dispensing unit (4); characterised in that the water recirculation branch (11) extends between the water recirculation valve device (28) and a water emanation point (32) of the hydraulic circuit (7) arranged downstream of the main water tank (12), so as to form a closed water recirculation loop; and in that the hydraulic circuit (7) further comprises a water recirculation tank (31) having a volume V2 less than the volume V 1 and arranged downstream of the water emanation point (32), along the closed water recirculation loop.

2. A beverage vending machine (1) comprising: a water inlet (2); a water heater (3) in the form of an instantaneous flow heater; a water pump (16) to supply the water heater (3) with water from the water inlet (2); a beverage dispensing unit (4) to receive hot water from the water heater (3) and prepare and dispense beverages: a hydraulic circuit (7) to fluidically connect the water inlet (2), the water pump (16), the water heater (3) and the beverage delivery unit (4) to each other, and comprising a water recirculation branch (11) to re-circulate the hot water flowing out of the water heater (3) back into the hydraulic circuit (7) and re-circulate it through the water heater (3);a water recirculation valve de vice (28) arranged downstream of an outlet of the water heater (3) to selectively supply hot water to either the recirculation branch (11) or the beverage dispensing unit (4); characterised in that the water recirculation branch (11) extends between the water recirculation valve device (28) and a water emanation point (32) of the hydraulic circuit (7), so as to form a closed water recirculation loop; and in that the hydraulic circuit (7) further comprises a water recirculation tank (31 ) arranged between the water pump (16) and the water emanation point (32).

3. The beverage vending machine (1) of claim 1, wherein the water recirculation tank (31) is arranged along a water suction conduit (17) connecting the main water tank (12) to a suction side of the water pump (16).

4. The beverage vending machine (1) of any one of the preceding claims, wherein the hydraulic circuit (7) comprises a magnetic anti-scale device (44) arranged downstream of the water emanation point (32), along the closed water recirculation loop.

5. The beverage vending machine (1) of any one of the preceding claims, wherein the water recirculation tank (31) is integrated in the water heater (3).

6. The beverage vending machine ( 1) of claim 5, wherein the water heater (3) comprises a tubular insert (33) having, on an outer surface thereof, a helical crest (34), and a cylindrical sleeve (35) which is coaxial to the tubular insert (33), bears a heating element, and is fitted onto the tubular insert (33) in contact with the helical crest (34) so as to delimit, with the tubular insert (33), a helical channel (36) for the flow' of water; wherein the tubular insert (33) is closed at its ends and delimits an internal cavity defining the water recirculation reservoir (31) and fluidically communicating with the helical channel (36), according to a series arrangement.

7. The beverage vending machine (1 ) of claim 6, wherein the water recirculation tank (31) fluidically communicates with a water inlet (39) of the water heater (3), and the helical channel (36) fluidically communicates with a water outlet (40) of the water heater (3); the water inlet (39) and the water outlet (40) are formed at one and the same end of the tubular insert (33), and the tubular insert (33) has, at an opposite end thereof, a through-hole (43) fluidically communicating the water recirculation tank (31) with thehelical channel (36) in such a way that the water recirculation tank (31 ) is arranged in series and upstream from the helical channel (36).

8. The beverage vending machine (1) of claim 6, wherein the helical channel (36) fluidically communicates with a water inlet (39) of the water heater (3), and the water recirculation tank (31) fluidically communicates with a water outlet (40) of the water heater (3); the water inlet (39) and the water outlet (40) are formed at one and the same end of the tubular insert (33), and the tubular insert (33) has, at an opposite end thereof, a through-hole (43) which fluidically connects the water recirculation reservoir (31) with the helical channel (36) in such a way that the water recirculation reservoir (31) is arranged in series with and downstream of the helical channel (36), in a direction of water flow along the hydraulic circuit (7).

9. The beverage vending machine (1) of any one of claims 6 to 8, wherein the heating element is of a thick film type.

10. The beverage vending machine (1) of any one of the preceding claims, wherein the water recirculating valve device (28) is part of a compact valve assembly (21) further comprising a plurality of water dispensing valve devices (22) to control hot water flow' to respective beverage preparation devices (5a, 5b), and a water supply manifold designed to receive hot water from the outlet of the water heater (3) and selectively supply it to the water recirculation valve device (28) and the water delivery valve devices (22); wherein the water recirculation valve device (28) and the water dispensing valve devices (22) are arranged in parallel to each other, with respect to the direction of the water flow along the hydraulic circuit (7), and the water recirculation valve device (28) is arranged at an end of the water supply manifold so that, when hot water is supplied to the water recirculation branch (11), the hot water flows through the water supply manifold and heats the entire compact valve unit (21).

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