Patent Publication Number: US-2022233018-A1

Title: Continuous-flow electromagnetic-induction fluid heater in a beverage vending machine

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS 
     This patent application is a U.S. national stage application under 35 U.S.C. § 371 of PCT Application No. PCT/IB2020/055727, filed on Jun. 18, 2020, which claims priority from Italian patent application no. 102019000009384 filed on Jun. 18, 2019. 
    
    
     TECHNICAL FIELD 
     The present invention relates in general to the field of beverage vending machines, and in particular to a continuous-flow electromagnetic-induction fluid heater for heating a fluid, in particular water, milk, air or the like, in a beverage vending machine, in order to prepare hot beverages from an anhydrous material, for instance coffee, tea, hot chocolate or the like. 
     BACKGROUND ART 
     Beverage vending machine, in particular for preparing beverages hot beverages from an anhydrous material, for instance coffee, tea, hot chocolate or the like, are known. 
     Such beverage vending machines are provided with one or more heaters configured to heat the water, for instance boilers or kettles. Known heaters generally comprise a heating element made of a resistive material and apt to heat the water held inside a tank or container of the machine. 
     More specifically, the heating element is permanently immersed in the water held in the container; a potential difference is applied to the ends of the heating element. An electric current is thus generated within the latter which, by the Joule effect, dissipates energy in the form of heat, thus heating the water by conduction. 
     It is thus necessary to maintain the water held in the container at a desired temperature so as to guarantee a rapid dispensing of the beverage. 
     It follows that, if the machine remains inactive for long periods, a considerable amount of energy will be consumed to maintain the water inside the container at the desired temperature (usually above 85° C.). 
     Moreover, the heaters mentioned above are of the accumulator type, i.e. of the type in which a given volume of water is held in the container and in which the water is heated and maintained at the desired temperature; when the dispensation of a certain volume of hot water is requested to prepare a corresponding beverage, the hot water drawn from the container is replenished with water at room temperature. The water in the container thus needs to be heated and raised again to the desired temperature so as to guarantee that the next dispensation occurs at the desired temperature. 
     In the latter case, a waiting period is thus necessary for re-heating the water, the duration of which depends on the quantity of hot water dispensed during one or more previous dispensations. 
     Besides temperature, an important specification to be met is the flow rate of the hot water dispensed, which depends above all on the type of beverage to be prepared; for instance, in the case of beverages produced by means of soluble substances, a considerable (at least 10 cc/s) flow rate of hot water is required. With a high flow rate of dispensed hot water, there will be a rapid drop in the temperature of the water held in the container, resulting in long waiting times for a subsequent dispensation or in an obtained beverage in which the soluble substance can form lumps. 
     FR-A-2855359, EP-A-1380243 and DE-A-102007034370 illustrate examples of continuous-flow water heaters for heating water by means of heat produced with electrical resistances. 
     The problems described above relating to the heating of the water in beverage vending machines stem from the thermal inertia with which a given mass of water heats up. 
     In order to remedy these technical drawbacks, solutions which exploit the phenomenon of electromagnetic induction for heating the water are known. 
     In particular, continuous-flow water heaters are known which exploit electromagnetic induction in order to generate parasitic currents within a duct made of an electrically conductive material inside which the water to be heated flows. The parasitic currents dissipate energy, by the Joule effect, in the form of heat, thus heating the duct and, consequently, the water that flows in contact with the same. 
     Electromagnetic induction heaters are known to be particularly advantageous inasmuch as they allow a rapid heating of the water. 
     EP-A-2868242, of the present Applicant, describes a heater comprising a metal duct wound in the shape of a spiral and housed in a cavity of a spool made of an electrically insulating material and on which a winding of electromagnetic induction is wound. 
     The winding is supplied with alternating electric current which generates, by electromagnetic induction, parasitic currents which heat, by the Joule effect, the spiral metal duct and thus the water which flows inside the same. 
     The spool is attached to the support structure of the machine, while the metal duct has no mechanical attachments with the spool, being simply supported by the hydraulic circuit to which it is connected by means of simple quick (push-in) fittings. 
     More specifically, the metal duct and the spool are separated radially by a free space (air gap). 
     This way, the maintenance of the heater and, in particular, the replacement of the metal duct is easier, more economical and simplified. 
     JP-A-2001284034 describes an example continuous-flow water heater by electromagnetic induction. 
     OBJECT AND SUMMARY OF THE INVENTION 
     Although the heater of the type described above represents a functionally viable solution for heating the water in beverage vending machines, the Applicant has had the opportunity to verify that the known heaters are capable of further improvement, in particular with respect to the efficiency of the heat exchange achievable by means of the heater. 
     The object of the present invention is to realize a continuous-flow electromagnetic-induction fluid heater, which is very reliable and of limited cost, and which makes it possible to satisfy the requirement specified above in connection with the known heaters. 
     According to the invention, this object is achieved by a continuous-flow electromagnetic-induction fluid heater and by a vending machine for preparing hot beverages comprising such a continuous-flow electromagnetic-induction fluid heater as claimed in the attached claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic perspective view, with parts removed for clarity, of a supply and heating assembly comprising a heater realized in accordance with a first preferred embodiment of the present invention; 
         FIG. 2  illustrates, on an enlarged scale and with parts removed for clarity, an axial section along the line II-II shown in  FIG. 1 ; 
         FIG. 3  illustrates a cross-section along the line shown in  FIG. 2 ; 
         FIG. 4  is analogous to  FIG. 2  and illustrates a corresponding axial section, on an enlarged scale and with parts removed for clarity, of a heater in accordance with a second preferred embodiment of the invention; 
         FIG. 5  is analogous to  FIG. 3  and illustrates a corresponding cross-section of the heater shown in  FIG. 4 ; 
         FIG. 6  is analogous to  FIG. 2  and illustrates a corresponding axial section, on an enlarged scale and with parts removed for clarity, of a heater in accordance with a third preferred embodiment of the invention; and 
         FIG. 7  is analogous to  FIG. 3  and illustrates a corresponding cross-section of the heater shown in  FIG. 6 . 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION 
     The present invention will be described in the following with reference to water heating without relinquishing any generality as a result, as it can also be used to heat other types of fluids utilized in beverage vending machines, in particular liquid milk or air used for emulsifying the liquid milk or fluids other than water. 
     With reference to  FIGS. 1 to 3 , a continuous-flow electromagnetic-induction fluid heater for heating a fluid, in particular water, in a beverage vending machine (not shown) in particular for preparing hot beverages from an anhydrous material, for instance coffee, tea, hot chocolate or the like, is indicated as a whole by 1. 
     In particular, the heater  1  is part of a supply and heating assembly  2  of the aforementioned beverage vending machine, which comprises:
         a hydraulic supply circuit  3  (shown schematically in  FIG. 1 ) provided with a container  4  containing water, preferably water at room temperature, and configured to conduct a flow of water from the container  4  towards the heating device  1  by means of a tube  5 ; and   an electric circuit  6  (shown schematically in  FIG. 1 ), the function of which will be clarified in the following.       

     In detail, the heater  1  is connected to the electric circuit  6  and fluidically connected to the hydraulic circuit  3 . 
     As shown in  FIG. 2 , the heater  1  comprises a tubular body  7  internally defining a flow channel  7   a  for the water. The tubular body  7  is thus hollow, has a longitudinal axis A and comprises an inlet opening  8  through which the water to be heated conveyed by the hydraulic circuit  3  is fed, in use, to the channel  7   a,  and an outlet opening  10  through which the heated water flows out, in use, from the channel  7   a.    
     According to this preferred and non-limiting embodiment, the tubular body  7  is substantially rectilinear, while the channel  7   a  is obtained coaxially to the axis A and has a substantially circular cross-section. 
     According to an alternative embodiment not shown, the tubular body  7  and/or the channel  7   a  may have a non-rectilinear configuration, for instance including one or more curved sections; moreover, the channel  7   a  may have a non-circular cross-section (for instance elliptical, oval, square, rectangular, polygonal, etc.). 
     The tubular body  7  is attached to an internal support structure (not shown) of the machine, in a known manner not described in detail. 
     In particular, the heater  1  comprises an upper end portion  14  and a lower end portion  15 , arranged on axially opposite sides of the tubular body  7 , fixed to the tubular body  7  and apt to be coupled (in particular mounted) to the internal support structure of the machine. 
     More particularly, the upper end portion  14  and the lower end portion  15  define respective axial closing elements of the tubular body  7 . 
     In one embodiment, the upper end portion  14  and the lower end portion  15  are coupled to the tubular body  7  in a removable manner, for instance by means of a threaded coupling. 
     As shown in  FIGS. 1 and 2 , the inlet opening  8  and the outlet opening  10  are defined by respective protuberances extending axially from the upper end portion  14  and from the lower end portion  15 , respectively. 
     In detail, the upper end portion  14  defines internally a passage  17  which connects the inlet opening  8  fluidically to the channel  7   a,  thus permitting the water to pass through the upper end portion  14  and flow into the channel  7   a.    
     Similarly, the lower end portion  15  defines internally a passage  18  which connects the channel  7   a  fluidically to the outlet opening  10 , thus permitting the water to pass through the lower end portion  15  and flow out of the tubular body  7 . 
     In light of the above, the inlet opening  8  and the outlet opening  10  are arranged at respective opposite axial ends of the tubular body  7 . 
     In the example shown, the outlet opening  10  is fluidically connected to an outlet tube  16  ( FIG. 1 ). This outlet tube  16  is configured to conduct the heated water from the heating device  1  to a beverage production chamber (not shown), where the heated water laps the anhydrous material generally contained in a capsule pierced beforehand. The thus obtained beverage is then conveyed from the production chamber to a dispenser (also not shown), by means of which it is discharged from the machine. 
     The heater  1  further comprises a winding  11  defined by a plurality of concentric spirals  11  a wound directly in contact around an external surface  12  of the tubular body  7 . 
     In detail, the winding  11  is configured to be supplied with an alternating electric current at a given oscillation frequency and to generate, in this manner, an electromagnetic induction field. 
     In greater detail, the electric circuit  6  applies, in use, an alternating voltage to respective ends  1  lb of the winding  11 , thus generating the aforementioned alternating electric current and the aforementioned electromagnetic induction field. 
     Preferably, the tubular body  7  is made of a material having zero magnetic susceptibility. 
     In this way, the tubular body  7  interacts with the electromagnetic induction field generated by the winding  11  to a minimal extent or essentially not at all, thus preventing a disturbance of the latter. 
     The heater  1  further comprises a heating element  13 , which is arranged inside the channel  7   a  so as to be lapped, in use, by the flow of water flowing inside said channel  7   a  and which can be activated, in use, by means of the electromagnetic induction field generated by the winding  11 . 
     Specifically, by supplying the winding  11  with alternating electric current, an alternating electromagnetic induction field is generated, the flux lines of which meet inside the channel  7   a  and, in particular, pass through the heating element  13 . According to Faraday&#39;s law, the variation in the resulting electromagnetic induction field flux generates parasitic currents inside the heating element  13 , which heat the heating element  13  by the Joule effect. 
     The heating element  13  is conveniently made of a ferromagnetic material. In this way, the lines of the electromagnetic induction field are closer together inside the heating element  13 , optimizing the generation of the parasitic currents, and are not dissipated inside the tubular body  7 . 
     In use, the water that flows inside the channel  7   a  laps the heating element  13  and is therefore heated by means of a heat exchange by conduction. 
     As shown in  FIG. 2 , the heating element  13  is radially spaced from the tubular body  7 , more precisely from an internal surface  19  of the channel  7   a,  by means of a gap  20  inside of which the water, in use, flows. 
     In detail, the heating element  13  extends axially inside the channel  7   a,  from the upper end portion  14  to the lower end portion  15  without ever contacting the internal surface  19  of the channel  7   a.  More specifically, the heating element  13  is fixed to the upper and lower end portions  14  and  15 . 
     According to this preferred and non-limiting embodiment, the heating element  13  has a substantially circular cross-section and is housed inside the channel  7   a  coaxially to the axis A. 
     Accordingly, the gap  20  has a substantially annular cross-section. According to an alternative embodiment not shown, the heating element  13  may have a non-circular cross-section, for instance elliptical, oval, square, rectangular, polygonal, etc. 
     In the example shown in  FIGS. 2 and 3 , the heating element  13  comprises, in particular is constituted by, a single bar element. 
     As shown in  FIGS. 1 and 2 , the supply and heating assembly  2  further comprises a temperature sensor  21  configured to measure the temperature of the water at the outlet opening  10 . 
     In particular, the sensor  21  is arranged, at least partially, inside the passage  18  of the lower end portion  15  of the heater  1  and is thus configured to measure, with an acceptable degree of approximation, the temperature of the water at the outlet opening  10 . 
     The assembly  2  further comprises a logic unit  22  configured to obtain the temperature values measured by the sensor  21 . 
     The logic unit  22  is also configured to control the activation and the deactivation of the electric circuit  6 , as well as to control the oscillation frequency of the alternating voltage applied by the electric circuit  6  to the winding  11 . 
     In use, based on the temperature value of the outgoing water measured by the sensor  21 , the logic unit  22  adjusts the oscillation frequency and thus the electric power output by the electric circuit  6 . It is indeed known that a greater temperature corresponds to a greater electric power, as a result of the greater heat produced by the Joule effect by the heating element  13 . 
     In this way, the logic unit  22  controls the variation of the temperature of the outgoing water. 
     Advantageously, the inlet opening  8  and the outlet opening  10  of the tubular body  7  are arranged in respective eccentric positions with respect to the axis A. 
     In particular, the inlet opening  8  and the outlet opening  10  are arranged in respective diametrically opposite positions with respect to the axis A. 
     In this way, the water flows, in use, inside the channel  7   a,  from the inlet opening  8  to the outlet opening  10 , according to a non-laminar motion regime. Indeed, as the two inlet and outlet openings  8  and  10  are situated on diametrically opposite sides with respect to the axis A, the water flows inside the gap  20  in a vortex motion around the heating element  13  in such a manner as to render the contact of the fluid with said heating element  13  uniform. 
     The operation of the heater  1  according to the present invention will be described in the following, with particular reference to an initial condition in which the water at room temperature is inside the container  4 . 
     In this condition, when a user orders the dispensing of a beverage, the logic unit  22  allows, by means of a system of valves and pumps of a known type (shown schematically in  FIG. 1 ), the flow of water to be heated through the inlet opening  8  and the passage  17  inside the tubular body  7 . 
     Simultaneously, the logic unit  22  controls the activation of the electric circuit  6 , which applies an alternating voltage at a given frequency to the ends  11   b  of the winding  11 , thus generating an alternating electric current, which in turn generates the aforementioned electromagnetic induction field. 
     As described above, this field causes the heating of the heating element  13 , which heats the water flowing inside the channel  7   a  and lapping said heating element  13 . 
     When the heated water flows through the passage  18 , the sensor  21  measures its temperature and sends the measured value to the logic unit  21 . This way, a closed-loop control of the measured temperature is achieved. 
     The heated water is then conveyed by means of the tube  16  to the chamber for producing the selected beverage. 
     With reference to  FIGS. 4 and 5 , a continuous-flow heater realized in accordance with an alternative preferred embodiment of the present invention is indicated as a whole by 1′. 
     Since the heater  1 ′ is similar by structure and operation to the heater  1 , only the structural and functional differences with respect to the latter will be described in the following. 
     The same references will be used to indicate similar or equivalent parts and/or features. 
     In particular, the heater  1 ′ differs from the heater  1  in that it is provided with a heating element  13 ′ which comprises, in particular is constituted by, a plurality of bar elements. 
     More specifically, the heating element  13 ′ is constituted by a bundle of bar elements having a smaller diameter than the diameter of the single bar element forming the heating element  13  of the heater  1 . 
     Specifically, each of the bar elements of the heating element  13 ′ extends axially inside the channel  7   a,  from the upper end portion  14  to the lower end portion  15 . 
     More specifically, the bar elements are fixed to these upper and lower ends portions  14  and  15 . 
     In use, the flow of water flowing inside the channel  7   a  laps each of the bar elements, running in the interstices of the channel  7   a  between the bar elements. The heat exchange is improved as a result, as the total transfer surface of the heating element  13 ′ is greater than that of the heating element  13 . 
     With reference to  FIGS. 6 and 7 , a continuous-flow heater realized in accordance with a further preferred embodiment of the present invention is indicated as a whole by 1″. 
     Since the heater  1 ″ is similar by structure and operation to the heater  1 , only the structural and functional differences with respect to the latter will be described in the following. 
     The same references will be used to indicate similar or equivalent parts and/or features. 
     In particular, the heater  1 ″ differs from the heater  1  in that it is provided with a heating element  13 ″ which comprises, in particular is constituted by, a plurality of thin wall sheets. 
     Specifically, each of the sheets of the heating element  13 ″ extends axially inside the channel  7   a,  from the upper end portion  14  to the lower end portion  15 . 
     More specifically, the sheets are fixed to these upper and lower ends portions  14  and  15 . 
     In use, the flow of water flowing inside the channel  7   a  laps each of the thin wall sheets, running in the interstices delimited between each pair of sheets. The heat exchange is improved as a result, as the total exchange surface of the heating element  13 ″ is even greater than that of the heating element  13 ′. 
     From an examination of the features of the heaters  1 ,  1 ′,  1 ″ realized in accordance with the present invention, the advantages rendered achievable by the same become evident. 
     In particular, as a result of the arrangement of the inlet and outlet openings  8  and  10 , it is possible to achieve a uniform flow of the water inside the channel  7   a  of the tubular body  7  so as to achieve a substantially vortex flow around the heating element  13 ,  13 ′,  13 ″ and thus an efficient and more uniform heat exchange with the latter. 
     Moreover, as a result of the shape of the heating element  13 ′, it is possible to achieve an improved heat exchange, since the exchange surface is greater than that of the heating element  13 . 
     Furthermore, as a result of the shape of the heating element  13 ″, this improvement is even more perceptible, since the ratio between the exchange surface and the volume of the heating element  13 ″ is greater in relation to the ratio between the exchange surface and the volume of the heating element  13 ,  13 ′. 
     It is evident that the described and shown heaters  1 ,  1 ′,  1 ″ can be modified and varied without leaving the scope of protection defined by the claims as a result.