Abstract:
A device is provided for producing milk foam, in particular in combination with an automatic coffee machine, which has a mixing chamber ( 13 ) to which milk, air, and rinsing medium can be supplied via various supply lines ( 11, 20, 21 ), wherein the supply of the rinsing medium to the mixing chamber takes place at least partially via the milk supply line ( 11 ). Here it is essential that the air supply line ( 20 ), at least with its end segment ( 20   a ) connected to the mixing chamber ( 13 ), can be selectively connected via a valve ( 22 ) to a line ( 23 ) having rinsing medium.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to a device for producing milk foam, in particular in connection with an automatic coffee machine, comprising a mixing chamber to which at least milk, air, and a rinsing medium can be supplied via various supply lines, wherein the supply of the rinsing medium to the mixing chamber takes place at least partially via the milk supply line.  
         [0002]     The foaming of milk is required primarily in the making of cappuccino, but is also necessary for other purposes. In this process, milk is mixed with air and steam. A problem here is that the line segments charged with milk, in particular foamed milk, become clogged over time, because the milk dries onto these segments. In addition to the functional disturbances caused by this, these deposits also result in adverse sensory effects due to the congealed albumen and the breakdown of casein.  
         [0003]     In order to avoid deposits of this sort, it is already known to regularly rinse the mixing chamber and the lines through which milk flows. Thus, for example in German patent application DE 199 55 195 A1 a coffee machine is described in which a rinsing medium (cold water or steam in the embodiment given there) is pumped both through the milk supply line and also directly into the mixing chamber. Here, the steam introduced directly into the mixing chamber can optionally be used to clean this chamber or to heat the milk during the preparation of drinks.  
         [0004]     This known apparatus has proven successful in practice. The present invention is intended to further improve it with respect to its rinsing and cleaning effect. At the same time, the present invention should be distinguished by a high degree of functionality and an economical design.  
       BRIEF SUMMARY OF THE INVENTION  
       [0005]     This object is achieved according to the present invention in that the air supply line can optionally be connected, at least with its end segment connected to the mixing chamber, via a valve to a line having rinsing medium. Thus, in the future it will be possible to rinse not only the line that is directly charged with milk, but also the air supply line. The background of this additional rinsing operation is the following: Examinations by applicant have shown that during the foaming of milk, particularly at high temperatures, the foam can penetrate into the air supply line from the mixing chamber. Consequently, the air supply line is surprisingly also a possible source of adverse sensory effects. This risk is eliminated by the rinsing of the air supply line according to the present invention.  
         [0006]     The mentioned valve, by which the air supply line can be connected to a rinsing medium, is usefully positioned at a clear distance from the mixing chamber, in particular at a higher level than this chamber. In this way, it is ensured that the region of the air line, into which the milk foam may possibly penetrate, is certain to be charged with rinsing medium.  
         [0007]     With respect to the constructive design of the mentioned valve, it is recommended to selectively connect the air line with a source of air or with the rinsing medium. In other words, the valve either creates a connection to the air source with simultaneous blocking of the rinsing medium, or it creates a connection to the rinsing medium with simultaneous blocking of the air source. In the simplest case, a double valve can be used for this purpose, which is connected to a common actuating element, in particular to a conventional electromagnet.  
         [0008]     As a rinsing medium for the air supply line, in principle all suitable agents in liquid form or gas form may be considered. Usefully, the medium already present for the rinsing of the milk supply line is also used for the air supply line. Here, it is particularly advantageous if cold water or a solution with chemical additives is first used as a rinsing medium, followed by steam or compressed air to clear the line.  
         [0009]     The triggering of the rinsing operation for the air supply line, and usefully also for the milk supply line, can take place via a time control device, that automatically carries out the rinsing after each drink preparation or after a predetermined number of preparations. Here, it is also recommended to make the triggering of the rinsing process dependent on there being no drink vessel underneath the spout of the coffee machine, which can be monitored using appropriate sensors.  
         [0010]     Finally, in an improvement of the basic concept of the invention, it is recommended that a check valve be arranged in the air supply line, downstream of the mentioned valve in the air supply line, in particular in the area of entry into the mixing chamber. This check valve reduces the penetration of milk, and consequently also reduces the required rinsing and cleaning expense. 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0011]     The foregoing summary, as well as the following detailed description of the invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there are shown in the drawings embodiments which are presently preferred. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown. In the drawings:  
         [0012]      FIG. 1  is a schematic flow diagram illustrating a coffee machine having a rinsing device according to the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0013]     In the drawing ( FIG. 1 ), at the right a large outlined rectangular area can be seen that indicates a coffee machine  1 . At its right lower side, it has a brewing assembly  2  having a coffee supply  3  and a hot water supply  4 , from which the brewed coffee is transported via a coffee line  5  to a spout  6 , and from there is supplied to a coffee cup  7  positioned under the spout.  
         [0014]     The milk is stored in a storage container  10  and is transported via a milk line  11 , using a pump  12 , to a mixing chamber  13 , which is likewise provided in the area of the spout of the coffee machine above the coffee cup. Milk line  11  is essentially divided into four sections, namely section  11   a  between the storage container  10  and the pump  12 , section  11   b  between pump  12  and a rinsing line connection  14  (described in more detail below), section  11   c  between rinsing line connection  14  and a cooling boundary (also described in more detail below), and section  11   d  between the cooling boundary and mixing chamber  13 .  
         [0015]     The mentioned rinsing line connection  14  connects milk line  11  with a rinsing line  15 , which is connected to a cold water supply  16  and to a steam supply  17 , so that cold water or steam serve as a rinsing medium. Rinsing line connection  14  is designed as a double-acting check valve having two spherical valve elements  14   a,    14   b  and a spring  14   c  that biases both valve elements against the inlets of the connected milk line and rinsing line.  
         [0016]     If milk pump  12  is actuated, valve element  14   a,  which seals the milk line, is pressed away against the force of the spring and opens the milk line, so that the milk can flow into mixing chamber  13  via sections  11   c  and  11   d.  Similarly, an opening of the cold water supply  16  or steam supply  17  results in a further check valve  18  opening the path of the water or the steam into rinsing line  15 , so that valve element  14   b,  which blocks the entry of the rinsing line into rinsing line connection  14 , is pressed inward against the spring force of spring element  14   c,  and the rinsing medium can flow into the mixing chamber via sections  11   c  and  11   d  of milk line  11 , and can rinse this mixing chamber. Moreover, cold water or steam can be conducted directly from check valve  18  into mixing chamber  13  via a water/steam line  21 , and can thus be used for the direct cleaning of the mixing chamber, the steam also being used to heat the milk.  
         [0017]     The cooling boundary mentioned above is indicated by the dashed-line rectangle  19  at the left, which represents a cooled area, in particular a refrigerator, which encloses and cools milk storage container  10 , line section  11   a,  pump  12 , line section  11   b,  rinsing line connection  14 , and line section  11   c.  Line sections  11   a,    11   b,  and  11   c  thus represent as a whole a cooled portion of milk supply line  11 . In this way, the milk in this cooled area is kept at a temperature low enough to prevent the formation of lactic acid or casein. Consequently, the cooled areas charged with milk also require little cleaning, so that a periodic rinsing with the aid of a milk cleaning agent introduced into the milk storage container is sufficient. The cooled and uncooled areas that are charged with milk and are connected downstream from the rinsing line connection, i.e., cooled section  11   c  and uncooled portion  11   d  of the milk line situated after the cooling boundary, can be easily rinsed by the steam or by the cold water at very short intervals. In a known manner a problem-free cleaning of all areas charged with milk is thereby ensured.  
         [0018]     An essential feature is the air supply line  20  connected to mixing chamber  13 . This line supplies the ambient air required for the foaming of the milk, and can at the same time be used to bleed air from the system. This air line  20 , together with its segment  20   a  opening into mixing chamber  13 , is connected to a rinsing medium via a valve  22  and a line  23 ; namely, it is connected to the already-mentioned cold water supply  16  or steam supply  17 . This makes it possible to rinse at any time not only the line sections charged with milk, but also segment  20   a  of air supply line  20 , which opens into the mixing chamber. If necessary, this rinsing operation can be followed by again blowing the line clear with air from a compressed air source, not shown in the drawing.  
         [0019]     In addition, it can be seen in the drawing that air supply line  20  has a separate valve  24 , and that this valve is combined with the above-mentioned valve  22  and is adjusted by an actuating element  25  that is common to both valves. The valves are connected together in such a way that either valve  22  is open and valve  24  is closed, or instead valve  22  is closed and valve  24  is open.  
         [0020]     While the introduction of water or steam via valves  16  or  17  takes place using pumps, not shown in the drawing, no pump is provided for the supply of air via line  20 ; instead, here the air is to be suctioned by reduced pressure (vacuum) in mixing chamber  13 , in particular by application of the Venturi principle. However, it will be understood to be within the scope of the invention to connect line  20  to a compressed air source, in particular if the line is again to be blown dry after rinsing with a liquid rinsing medium.  
         [0021]     Finally, the drawing shows that diaphragms are built into each of lines  15 ,  20 , and  23 , and act to control the flow quantities.  
         [0022]     In sum, the present invention thus offers the advantage that, by the rinsing of air supply line  20 , a further improvement of the hygienic and sensory conditions in the coffee machine is achieved, requiring no additional time expense, because the air supply line can be rinsed at the same time as the milk supply line.  
         [0023]     It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims.