Abstract:
A method for heating and whipping milk, in particular for preparing cappuccino in coffee machines, in which the heating and whipping of the milk are carried out by the combined action of a flow of vapour, which is dispensed by a boiler which produces water vapour, and a flow of compressed air, which is dispensed by an associated source of compressed air, wherein the flow of compressed air is constituted by pulses which have a predetermined duration and which are intercalated in inactive periods.

Description:
TECHNICAL FIELD  
       [0001]     The present invention relates to a method for automatically heating and whipping milk, in particular for preparing cappuccino in coffee machines, in which the heating and whipping of the milk are carried out by the combined action of a flow of vapour, which is dispensed by a boiler which produces water vapour, and a flow of compressed air, which is dispensed by an associated source of compressed air; the present invention also relates to a device for heating and whipping milk with the heating temperature and the quantity of foam produced being controlled in a manner suitable for carrying out the method according to the invention.  
       BACKGROUND OF THE INVENTION  
       [0002]     The operations for heating and whipping the milk for producing cappuccino which, as is known, is a drink containing coffee and whipped milk, are generally carried out by directing a jet of vapour and compressed air into a container, for example, a jug, containing cold milk via a spout which is positioned at the end of a vapour pipe, which is generally provided with a cut-off valve for controlling the flow of vapour.  
         [0003]     Devices for heating and whipping milk, of the above-mentioned type, are known in the prior art because they offer the advantage of being able to carry out whipping of the milk with a quantity of foam and at a temperature desired.  
         [0004]     A known solution in the art provides for the use, as set out in WO 03/092458, of a device comprising a boiler which produces vapour, directing means which are provided with an open end which can be immersed in a jug containing the milk to be heated and whipped, a first pipe for supplying the vapour connected between the boiler and the directing means, a cut-off member positioned in the first pipe, a compressor for producing compressed air, a motor for actuating the compressor, a second pipe for supplying the compressed air connected between the compressed air compressor and the directing means, an element which is sensitive to temperature and which is associated with the immersible end of the directing means in order to detect the temperature of the milk in the container, and a control unit which is connected to the cut-off member, the compressor for producing compressed air and the element which is sensitive to temperature.  
         [0005]     In accordance with the above-illustrated technical solution, the flow of compressed air is adjusted by means of a throttle which is calibrated, or also adjustable, and which is positioned downstream of the compressor, in the pipe which connects the source of air to the directing means which are immersed in the milk contained in the jug.  
         [0006]     As is known, in circuits downstream of an air compressor, the humidity present in the air condenses as a result of the increase in the pressure to which the air is subjected.  
         [0007]     That phenomenon sometimes brings about poor operating conditions for the device because the condensed water tends to block the throttle. Since the throttle has dimensions for withstanding air resistance, it has a through-hole of small dimensions that is not suitable for the flow of a liquid having the viscosity of water.  
         [0008]     Under such conditions, consequently, the compressed air cannot be dispensed to the directing means, which in practice only the flow of vapour reaches, bringing about the lack of whipping of the milk and therefore the absence of foam.  
       SUMMARY OF THE INVENTION  
       [0009]     The object of the present invention is to carry out a method for heating and whipping the milk which can overcome the disadvantages indicated and set out above in relation to devices which make use of a compressor for supplying compressed air to the device for whipping the milk.  
         [0010]     The object is achieved by means of the method for automatically heating and whipping milk, in particular for preparing cappuccino in coffee machines, in which the heating and whipping of the milk are carried out by the combined action of a flow of vapour, which is dispensed by a boiler which produces water vapour, and a flow of compressed air, which is dispensed by an associated source of compressed air, wherein the flow of compressed air is constituted by pulses which have a predetermined duration and which are intercalated in inactive periods, and by means of a device for heating and whipping milk, in particular for preparing cappuccino in coffee machines, comprising: 
        a boiler which produces vapour,     directing means which are provided with an open end which can be immersed in a container containing milk,     a first pipe for supplying the vapour, which pipe is connected between the boiler and the directing means,     a cut-off member which is positioned in the first pipe,     a compressor for producing compressed air,     a motor for actuating the compressor,     a second pipe, for supplying the compressed air, which pipe is connected between the compressor for compressed air and the directing means,     an element which is sensitive to temperature and which is associated with the immersible end of the directing means in order to detect the temperature of the milk in the container,     a control unit which is connected to the cut-off member, the compressor which produces compressed air and the element which is sensitive to the temperature of the milk, the control unit being programmable in order to control the opening and closing of the cut-off member and to actuate the compressor for compressed air, in accordance with the desired temperature and/or whipping for the milk, wherein the control unit actuates the compressor for compressed air in an intermittent manner, producing pulses of compressed air for predetermined periods of time which are alternated with inactive periods.        
 
         [0020]     The invention will now be described in greater detail with reference to a device which can carry out the method which is schematically illustrated in the single FIGURE of the appended drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0021]      FIG. 1  is a schematic drawing of the circuit according to a preferred embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0022]     In the embodiment illustrated in  FIG. 1 , the device  1  for heating and whipping the milk comprises a boiler  2  which produces water vapour and a directing pipe  3  which is provided with an open end  4  which can be immersed in a jug  5  containing milk.  
         [0023]     The boiler  2  for producing vapour can be of the type conventionally provided in a machine for preparing coffee, in particular espresso coffee, whether of the manual type or the type with automatic operation.  
         [0024]     Furthermore, the device  1  includes a first pipe  6  for supplying the vapour, a cut-off valve  11  which is positioned in the first pipe  6 , a source  19  of compressed air and a second pipe  9  for supplying the compressed air.  
         [0025]     The source  19  of compressed air preferably, but not exclusively, comprises, as illustrated in the FIGURE, a compressor  7  which is actuated by an electric motor  8 . The source of compressed air allows the production and supply of compressed air.  
         [0026]     The directing pipe  3  directs a jet of vapour and compressed air through the open end  4 , from the first pipe  6  and the second pipe  9 , respectively, into the container  5 . The directing means  3 , in the construction illustrated, is preferably a pipe which can be orientated as desired, optionally a flexible pipe, so as to facilitate its insertion into the container  5 , for example, a jug, and to allow complete immersion of the open end  4  in the milk to be heated and whipped.  
         [0027]     The heating and whipping of the milk are controlled by a control unit  10  which is connected to the vapour cut-off valve  11 , the motor  8  of the pump  7  for the air and, in addition, a temperature transducer  12  which is connected to the immersible end  4  of the directing means  3  and which can detect the temperature of the milk when the end  4  is immersed in the milk.  
         [0028]     The temperature transducer  12  is advantageously an element which is sensitive to temperature, such as, for example, a thermocouple, a thermoresistor, and the like, whose output magnitude, at the input to the control unit  10 , is by nature electrical in a preferable but not exclusive manner.  
         [0029]     The control unit  10  comprises, in a simplified form thereof, a programmable CPU (not illustrated), a display  13  and a series of push-buttons  14  which are connected to the CPU. The unit  10  is supplied by a source of electrical power which is not shown in the Figures.  
         [0030]     The CPU associates a series of operations to be carried out with each push-button  14 . The operations to be carried out depend on the desired temperature and/or whipping of the milk.  
         [0031]     For the control unit  10 , in accordance with the push-button actuated, immediately detects the temperature of the milk by means of the transducer  12  in order to act both on the valve  11  for cutting off the vapour, advantageously a solenoid valve, and on the source  19  of compressed air, in the first case controlling the opening and closing of the valve  11  and, in the second case, actuating the source  19  of compressed air, one independently of the other, in accordance with the temperature of the milk. Alternatively, it is further possible to control the opening of the valve  11  and/or to actuate the source  19  of compressed air for a predetermined period of time.  
         [0032]     In accordance with the present invention, the pipe  9  for supplying the flow of compressed air is not provided with throttle members. The control of the necessary flow of air is brought about, in accordance with the invention, by the compressor  7  being actuated for short pulses which are determined by the electric motor  8  under the control of the control unit  10  and the adjustment of the flow is brought about by the durations of the intervals being varied.  
         [0033]     In practice, it has been found that, for example, in order to obtain a high level of whipping of the milk, for each unitary pulse of air, for example, equal to one second, the interval between one pulse and the next must be equal to the same unit, that is to say, equal to one second.  
         [0034]     Should it be desirable to obtain a medium/high level of whipping, with the unitary pulse for pumping the air still set at a level equal to one second, the intervals would have to be equal to two units, that is to say, 2 seconds each.  
         [0035]     For a medium/low level of whipping, however, still for a given duration of one second for the unitary pulse, the intervals must be sustained for a duration equal to three units of time, that is to say, 3 seconds each.  
         [0036]     Finally, for a low level of whipping, still for a given unitary duration for the pulses of air, the duration of the intervals between the pulses must be sustained for a duration equal to four units, that is to say,  4  seconds.  
         [0037]     In accordance with the invention, a better quality of whipping of the milk is obtained by causing the flow to start with pulses of compressed air when the milk in the jug  5  is already in a turbulent state owing to the vapour already having been introduced, still under the control and command of the control unit  10 .  
         [0038]     Advantageously, therefore, it is necessary to start the flow cycle with pulses of compressed air and a specific time delay with respect to the start of the cycle for admitting the vapour, which delay is determined by the milk reaching a specific temperature threshold, for example, 30° C.  
         [0039]     The invention is not restricted to the above-described embodiment alone, but instead comprises a number of embodiments, all falling within the spirit and the scope of the invention, as claimed hereinafter.