Abstract:
A milk frothing appliance ( 1 ), comprising:—a water reservoir ( 160 );—a steam generator ( 200 );—a milk frothing device ( 180 ) that is fluidly connected to the steam generator ( 200 ); and—a hand pump ( 130 ) that is fluidly connected to both the water reservoir and the steam generator, comprising a manually operable actuator ( 220 ) that is moveable between a first actuator position and a second actuator  138  position, and that upon movement from the first actuator position into the second actuator position causes displacement of fluid from the water reservoir to the steam generator ( 200 ).

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to an apparatus for frothing a liquid food product. Since apparatus of this type are commonly used to froth milk, the apparatus is referred to as a milk frothing appliance in the text that follows. 
       BACKGROUND 
       [0002]    Milk frothing appliances are available in different types. Some milk frothing appliances, for instance, are integrated into coffee machines, while others are configured for stand-alone use. 
         [0003]    An example of an integrated milk frothing appliance is the ‘steam wand’ that is customarily built-in in espresso machines. To froth milk, a steam outlet of the steam wand is positioned in a cup of milk, at or just below the surface of the milk. Then the steam wand is turned on so as to effect the ejection of a jet of steam that, as it impacts the air-milk interface, causes the production of an milk-air-steam mixture which results in the desired froth. A disadvantage of the steam wand is that its operation requires skill on the part of the user, in particular since the optimal position of the steam outlet relative to the milk surface is rather sensitive. 
         [0004]    To simplify the production of milk froth, especially for home users, various dedicated stand-alone milk frothing devices have been developed. Some make use of an internal heatable tank for receiving a milk-based liquid, in which a rotatably drivable stirrer or whisk is positioned for whipping the liquid into a froth. Others mimic the operation of a steam wand, and include a modified, typically Venturi-based steam outlet nozzle that assists in the act of frothing by siphoning milk from a cup, mixing it with air and steam, and dispensing it back into the cup it came from. 
         [0005]    Known dedicated milk frothing devices are typically electrically powered devices that include plenty of electronics. Besides a heater, such electronics may include an electric motor to drive the stirrer, or alternatively, in the case of a steam wand-mimicking device, a solenoid pump and several valves as part of a water dosing system configured to deliver water successively to the electric heater and an outlet of the steam wand. In addition, the milk frothing device may include internal electronics such as a central controller that controls the operation of the entire device, and for example allows a user to set certain operating parameters e.g. heater temperature, whisking time, steam quantity, etc. in dependence of the liquid to be frothed and its volume. The device may further be fitted with a plurality of external controls to enable a user to input the desired parameters. 
         [0006]    The electronic components in known milk frothing devices make their manufacture rather costly, and their operation in generally humid kitchen environments susceptible to failure. The risk of moist-induced defects is particularly imminent for stirrer-type frothers, of which at least the internal liquid tank must be thoroughly cleaned after each use to maintain the hygiene of the device. Furthermore, the external user controls necessary to operate the full functionality of milk frothing device may normally be positioned on an outside of the device and, and may so mar an otherwise aesthetically pleasing, stylishly clean appearance. 
       SUMMARY OF THE INVENTION 
       [0007]    It is an object of the present invention to provide for a milk frothing device that overcomes or mitigates one or more of the aforementioned drawbacks associated with known milk frothers. More in particular, it is an object of the present invention to provide for a milk frothing device that is economically manufacturable, reliable, does not demand extensive cleaning after use and enables a design free of a plurality of external controls. 
         [0008]    To this end, a first aspect of the present invention is directed to a milk frothing appliance. The appliance may comprise a water reservoir for holding water, a steam generator for evaporating water, and a milk frothing device for frothing milk with the aid of steam, which device is fluidly connected to the steam generator. The appliance may further include a hand pump that is fluidly connected to both the water reservoir and the steam generator, and may comprise a manually operable actuator that is moveable between a first actuator position and a second actuator position, and that upon movement from the first actuator position into the second actuator position causes displacement of fluid from the water reservoir to the steam generator. 
         [0009]    The mechanical hand pump in the presently disclosed appliance eliminates the need for a complex electric pump, and thus renders the appliance relatively economic to manufacture. It also makes the appliance more reliable since the hand pump is less prone to (in particular moist-induced) defects than an electrical pump. In addition, it may instil a sense of workmanship into the user as he has to apply a little muscular strength to the actuator in order to force water from the water reservoir into the steam generator. The hand pump may preferably be configured such that one actuator or pump stroke displaces about 0.5-5 ml of water, enabling an amount of steam sufficient for a typical cup of milk froth to be generated through about one to three pump strokes. 
         [0010]    Importantly, the actuator of the hand pump may effectively be the only user control on the appliance and allow for a very clean, quiet design. 
         [0011]    The hand pump actuator&#39;s first and second positions may be defined differently in different embodiments. For instance, in one embodiment the hand pump may be a lever pump, and the actuator may take the form of a lever that is hingeable between a first and a second angular orientation. In another embodiment, the hand pump may for example be a screw pump, and the actuator may be connected to the rotatable screw such that its first and second positions may define different rotational positions relative to the screw&#39;s  axis spindle. In a preferred embodiment, the hand pump actuator functionality may be realized by configuring the actuator such that it is moveable between the first actuator position and the second actuator position by translation along a first, central or longitudinal axis of the appliance. The central or longitudinal axis of the appliance may typically extend vertically during normal use, such that in particular a manual push force exerted on the actuator to move it from the first actuator position to the second actuator position is automatically balanced by the surface that supports the appliance as a whole, e.g. a kitchen working top. 
         [0012]    Additional functionality, e.g. an electric on/off switch function for in particular the steam generator, may be integrated into the actuator by configuring it such that it is additionally moveable between a third actuator position and a fourth actuator position, preferably by rotation around the first axis. Such a configuration eliminates the need for an extra control switch on the outside of the appliance, and may thus contributes to the quiet design thereof. 
         [0013]    In one embodiment the above-mentioned two functions of the actuator may be coupled; after all, displacing water from the water reservoir to the heat generator makes sense only—and should therefore be allowed only when the appliance is electrically switched on and the steam generator is electrically powered. The actuator in the third actuator position, i.e. the electrical OFF-position, may therefore be locked against movement between the first actuator position and the second actuator position, while the actuator in the fourth actuator position, i.e. the electrical ON-position, may be moveable between the first actuator position and the second actuator position. 
         [0014]    The appliance may be used as a stand-alone appliance, or be integrated into a coffee machine, e.g. an espresso machine. 
         [0015]    These and other features and advantages of the invention will be more fully understood from the following detailed description of certain embodiments of the invention, taken together with the accompanying drawings, which are meant to illustrate and not to limit the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]      FIG. 1  is a schematic perspective view of an exemplary milk frothing appliance according to the present invention, comprising a body and an actuator disposed on top thereof; 
           [0017]      FIG. 2  is a schematic cross-sectional side view of the milk frothing appliance shown in  FIG. 1 ; 
           [0018]      FIG. 3  is a schematic top view of the body of the milk frothing appliance shown in  FIGS. 1 and 2 , wherein the actuator is removed from the top of the body so as to reveal the sink cover; 
           [0019]      FIG. 4  is a schematic perspective top view of the body of the milk frothing appliance shown in  FIGS. 1-4 , illustrating in particular the construction of the top end of the cylindrical shaft of the hand pump; 
           [0020]      FIG. 5  is a schematic perspective bottom view of the actuator of the milk frothing appliance shown in  FIG. 1-4 ; and 
           [0021]      FIG. 6  is a schematic perspective view of the milk frothing appliance shown in  FIGS. 1-5 , wherein the outer housing of the milk frothing device has been removed to make its internal tubing visible. 
       
    
    
     DETAILED DESCRIPTION 
       [0022]      FIGS. 1-6  schematically illustrate an exemplary embodiment of a milk frothing appliance  1  according to the present invention, whose construction and operation are discussed below. 
         [0023]    As can be seen best in  FIGS. 1 and 2 , the milk frothing appliance  1  may include a generally conical body  100  that accommodates a water reservoir  160 , a steam generator  200 , most of a hand pump  130  for transferring water from the water reservoir  160  to the steam generator  200 , and an electrical controller  112 . The appliance  1  may further include an actuator  220 , which may be disposed on top of the body  100  and be considered to form a part of the hand pump  130 , and a milk frothing device  180  that is connected to the body  100  and extends sideways therefrom in a slopingly downward direction. The water reservoir  160 , the hand pump  130 , the steam generator  200  and milk frothing device  180  may be fluidly connected in series, in that order. 
         [0024]    The water reservoir  160  may be defined by a bottom wall  162 , a generally conical side wall  164  fitting the contour of the body  100 , and a sink cover  166 . The sink cover  166  may be integrally formed with a cylindrical shaft  132  of the hand pump  130 , around which the water reservoir  160  may be centered. The cylindrical shaft  132  may extend downwards through both the sink cover  166  and the bottom wall  162  of the water reservoir  160 . Watertightness of the connection between the bottom wall  162  of the water reservoir  160  and the cylindrical shaft  132  of the hand pump  130  may be effected through an  0 -ring  150 . The sink cover  166  of the water reservoir  160 , so named because its appearance is reminiscent of a sink (see  FIGS. 3 and 4 ), may define a bottom wall  168  and an upstanding side wall  174 . The bottom wall may define at least one drain opening  170 ,  172  so as to enable water poured into the sink cover  166  to drain into the water reservoir  160  below it. In the depicted embodiment, as can be seen best in the top view of  FIG. 3 , the sink cover includes three drain opening: two slotted openings  170  that extend partially around the cylindrical shaft  132 , and one smaller opening  174  that extends up to the side wall  174  of the sink cover. The latter drain opening  174  may be configured for cooperation with an electronic switch portion  240  of the actuator  220  and define a rotational ON-position of the actuator, as will be described infra 
         [0025]    As mentioned, the hand pump  130  may include a cylindrical shaft  132  that extends downwardly through the water reservoir  160 , and along a central axis L of the body  100 . The cylindrical shaft  132  may define a fluid chamber  134  whose volume is determined by the axial position of a piston  136  that is movably arranged within the shaft  132 . The piston  136  may be axially moveable between an first or upper position (shown in  FIG. 2 ) and a second or lower position, and be biased towards the upper position by a mechanical spring  137 . A piston seal  140  may be provided in a recess in the circumferential wall of the piston  136  to ensure that (pressurized) water does not leak between the shaft  132  and the piston  136  when the latter is axially displaced. The fluid chamber  134  may be in selective fluid communication with the water reservoir  160  via a first one-way or check valve  144  that is disposed just above the bottom wall  162  of the water reservoir  160 , and with a water supply end  208  of a steam line  206  of the steam generator  200  via a second one-way valve  148  that is disposed at a lower end of the shaft  132 . The two one-way valves  144 ,  148  may be configured to operate alternately, such that water is sucked into the fluid chamber  134  from the water reservoir  160  when the piston  136  moves upwards in the shaft  132 , and water is forced out of the fluid chamber  134  into the steam line  206  of the steam generator  200  when the piston  136  moves downward. The hand pump  130  may preferably be configured such that during a down stroke of the piston about 0.5-5 ml of water is delivered to the steam generator  200 . This enables the generation of an amount of steam that is sufficient for a typical cup of milk froth through about one to three pump strokes. One skilled in the art will appreciate that hand pumps, in particular exclusively mechanical hand pumps, come in various types, and that the presently disclosed appliance  1  is not limited to use of the depicted hand pump construction, but may instead employ each of these various types. 
         [0026]    The steam generator  200  may comprise a thermal mass  202 , for example in the form of a block made of a metal with a relatively great specific heat and thermal conductivity, e.g. aluminum. The thermal mass  202  may accommodate two co-axially wound coils  204 ,  206 . An inner coil may be formed by an electrically resistive heating spiral that serves as a heating element  204 , while an outer coil may be formed by the hollow steam line  206 , which, for instance, may be made of stainless steel. In operation, water released into the water supply end  208  of the steam line  206  may be virtually instantly evaporated by heat withdrawn from the thermal mass  202 , which may have been heated by the heating coil  204  to a temperature well above 100° C., e.g. a temperature in the range of 130° C.-150° C., during a brief preceding heating up phase. The use of the thermal mass  202  may thus promote steady energy consumption from the mains, and consistent steam production. Since the water supply end  208  of the steam line  206  is normally closed by the second check valve  148 , water that is evaporated inside the steam line  206  is forced out of the steam line at its steam discharge end under its own pressure. The steam discharge end may be formed by a steam tube  210  that extends from the steam generator  200  is connected to the milk frothing device  180 . 
         [0027]    The milk frothing appliance  1  according to the present invention may be configured to enable ‘in-cup milk frothing’, that is milk frothing not within a large internal (milk (froth)) reservoir, but in an external cup. One form of in-cup milk frothing was already mentioned above and includes the steam wand; the milk frothing device according to the presently disclosed appliance may mimic such a steam wand, and, to that end, include little more than a steam outlet pipe. However, to facilitate the frothing process, the milk frothing device may implement a form of in-cup milk frothing in which milk is siphoned from a cup of milk, frothed by the device, and then discharged back into the cup. This is more user friendly as it does not require particular skill on the part of the user, and avoids the necessity to extensively clean an internal milk reservoir of the appliance  1  afterwards: only the steam frothing device needs to be cleaned, which may form a detachable, hand- or machine-washable part of the appliance  1 . 
         [0028]    Accordingly, the milk frothing device  180  used in the appliance according to the present invention may include two tubes: a milk suction tube  182 , and a frothing tube  184 . The milk suction tube  182  may be the longer of the two, and extend between a free lower end and an upper end. The frothing tube  184  may also extend between a free lower end and an upper end. In one embodiment (not illustrated), the frothing tube  184  may include two serially arranged Venturi&#39;s. A first Venturi may be disposed at the upper end of the frothing tube, and be configured for mixing steam with milk (so as to heat the latter). To this end, an upstream end of the first Venturi may be connected to the steam tube  210 , while the downstream end may be connected to the upstream end of the second Venturi. A constriction between the upstream and downstream ends of the first Venturi may be connected to the upper end of the milk suction tube  182 , such that, when steam is forced through the first Venturi, milk may be sucked into the steam flow via the milk suction tube to produce a steam-milk mixture. The second Venturi may be disposed just downstream of the first, and be configured for mixing the mixture of steam and milk with air and to thus create the desired heated milk froth; hence, a constriction in the second Venturi may be fluidly connected to the atmospheric environment of the device via an air suction tube. 
         [0029]    As one skilled in the art will appreciate, the milk frothing device  180  may be designed in various ways. In another embodiment, the two above-described Venturi&#39;s may for example be combined into one Venturi whose constriction is fluidly connected to both the upper end of the milk suction tube  182  and the air suction tube. In another, preferred embodiment, which is illustrated in  FIG. 6  by taking the outer housing off of the tubes  182 ,  184 , the second Venturi may be replaced by a mixing space  188  that is disposed downstream of the first Venturi  186 , and that has a relatively large upstream inlet opening spaced apart from the downstream end of the first Venturi  186 , in a concentric arrangement therewith, such that an air gap  190  exists between the first Venturi  186  and the mixing space  188 . Hence, when, during use, a jet of a mixture of steam and milk flows from the first Venturi  186 , it crosses the gap  190  between the first Venturi  186  and the mixing space  188 . Under the influence of the jet air is drawn into the air gap  190 , such that a mixture of steam, milk and air is received in the mixing space  188 . Within the mixing space  188  the steam quickly condenses into the milk, leaving the desired heated milk froth. This latter embodiment of the milk frothing device is described in more detail in International patent application no. incorporated by reference. 
         [0030]    The milk frothing appliance  1  according to the present invention may include relatively little electronics. Besides the (heating element  204  of the) steam generator  200 , the milk frothing appliance  1  may comprise a power cord  110 , a central controller  112 , and a user operable switch  114 . The power cord  110  may be connected to the body  100  of the appliance  1 , and extend between a plug (not shown) on the outside and the central controller  112  on the inside of the body  100 . The central controller  112 , in turn, may further be connected to the switch  114  by means of an electrical cable  120 , and to the heating element  204  by an electrical cable  122 . The controller  112  may be configured to power the heating element  204  when the switch  114  is in an ON-state, and to cut power to the heating element  204  when the switch  114  is in an OFF-state. 
         [0031]    The user operable switch  114  may be of any suitable type, and typically include two parts: a first part that is fixedly connected to the body  100 , and a second part that is integrated into the actuator  220 . The first part may for example include a magnetic sensor  116 , e.g. a reed sensor or a Hall sensor, while the second part may include a permanent magnet  118 , or vice versa. Just as in the depicted embodiment, the magnetic sensor  116  may be provided on/against an outside of the side wall  164  of the water reservoir  160 , near the drain opening  174  in the bottom wall  168  of the sink cover  166  that is configured for cooperation with an electronic switch portion  240  of the actuator  220 . The associated permanent magnet  118  may be accommodated in the electronic switch portion  240  of the actuator  220 , as will be clarified below. Accordingly, when the actuator  220  is oriented to bring the permanent magnet  118  inside the electronic switch portion  240  thereof to within the vicinity of the magnetic sensor  116 , the sensor  116  may detect the magnetic field of the magnet  118  and cause the switch to change from its default OFF-state to its ON-state. 
         [0032]    The actuator  220  of the milk frothing appliance  1 , which is shown in isolation in  FIG. 5 , may enable the apparatus&#39; operation. More particularly, the actuator  220  may serve as a lid for the sink cover  166 , as an actuator for the hand pump  130 , and/or as a control switch for the electronics of the appliance  1 , including in particular the steam generator  200 . In the depicted embodiment the actuator  220  fulfils all three functions, but in alternative embodiments it may merely fulfil one or two of them. 
         [0033]    The actuator  220  may include an outer shell  222  and an inner shell  228 . Both shells  222 ,  228  may be generally cup shaped, having a central wall portion  224 ,  230  and an upstanding side wall  226 ,  232  provided along the circumference of the central wall portion  224 ,  230 . The outer shell  222 , which may be visible from the outside of the appliance  1  (see  FIG. 1 ), may be provided with an aesthetically pleasing appearance, e.g. by manufacturing it from brushed metal. The inner shell  228 , which may be manufactured from plastic, for instance by means of injection molding, may define a hand pump interface portion  234  and an electronic switch portion  240 . The construction and operation of both portions  234 ,  240  will be elucidated in turn. 
         [0034]    The hand pump interface portion  234  may be configured to interface with the cylindrical shaft  132  and the piston  136  of the hand pump  130 . It may include a cylindrical shaft insert  236  that is centrally arranged on and protrudes perpendicularly from the central wall portion  230  of the inner shell  228 . An outer diameter of the shaft insert  236  may be slightly smaller than an inner diameter of an upper end the cylindrical shaft  132  of the hand pump  130 , such that the shaft insert  236  may be slid into the upper end of the cylindrical shaft  132  to connect to the piston  136 . The proper connection between the shaft insert  236  and the piston  136  may be facilitated by providing each with a half of a pair of mating male-female connectors. For instance, in the depicted embodiment, the piston  136  is provided with a central pin  138  while the shaft insert  236  is provided with a matching socket  238 . The overall axial length of the shaft insert  236  may be chosen such that, when the shaft insert  236  is inserted in the cylindrical shaft  132  of the hand pump  130  and rests upon the piston  136  in its upper position, the cup-shaped portions  222 ,  228  of the actuator  220  occupies a rest position from which it may be displaced downwards, effectively into the space defined by the sink cover  166 , so to force the piston  136  into its lower position and to effect a pump stroke that displaces water from the fluid chamber  134  of the hand pump  130  into the water supply end  208  of the steam line of the steam generator  200 . 
         [0035]    To enable the actuator  220  to be removably locked to the rest of the appliance  1 , the hand pump interface portion  234  of the actuator  220  on the one hand, and the upper end of the cylindrical shaft  132  and the piston  136  of the hand pump  130  on the other may define a bayonet mount. The shaft insert  236  of the hand pump interface portion  234  may for example be provided with one or more radially outwardly protruding pins  237 , while an inner wall of the upper end of the cylindrical shaft may be provided with one or more respective corresponding angular slots  133 , or vice versa. 
         [0036]    In the depicted embodiment (see in particular  FIGS. 4 and 5 ), the shaft insert  236  is provided with one pin  237  at a position diametrically opposite to the electronic switch portion  240 . The inner wall of the upper end of the cylindrical shaft  132  is complementarily provided with one matching angular slot  133  that includes three straight slot sections  133   a,b,c.  A first  133   a  and third  133   c  of the slot sections extend in parallel along the central axis L of the cylindrical shaft  132 , and a second  133   b  interconnects the two at right angles. The first and second slot sections  133   a,    133   b  form part of the lock of the bayonet mount: the actuator  220  may be positioned on top of the body  100  by inserting its shaft insert  236  into the upper end of the cylindrical shaft  132  of the hand pump  130 , such that the pin  237  on the shaft insert  236  slides downwards into the first (axially extending) slot section  133   a.  On its way down the shaft insert  236  may engage the spring biased piston  136 , such that further downward travel compresses the spring  137  slightly. Once the pin  237  encounters the lower end of the first slot section  133   a,  the actuator  220  may be turned clockwise through an angle of about 45° around the central axis L of the appliance  1 , so that the pin  237  slides tangentially through the second slot section  133   b  to a point halfway thereof. This point may define a rotational OFF-position of the actuator  220 . Due to the upward action of the spring biased piston  136  against the shaft insert  236 , the actuator  220  may be frictionally locked in place in this OFF-position. From the OFF-position, the actuator  220  may be turned in either an anti-clockwise direction, e.g. as a first step in executing the above steps in reverse to remove the actuator  220  from the body  100 , or a clockwise direction. The actuator  220  cannot be moved up or down, for instance because the pin  237  in the horizontally extending second slot section  133   b  prohibits such motion. When the actuator  220  is turned further in the clockwise direction, e.g. through a total angle of about 90°, the pin  237  encounters an end of the second slot section  133   b,  which may correspond to an upper end of the third slot section  133   c.  This position of the actuator  220  may define the rotational ON-position referred to above, and allow for movement for up and down movement of the actuator  220  along the axial direction L because (i) the pin  237  now resides in the axially extending third slot section  133   c,  and (ii) the electronic switch portion  240  of the actuator  220  is in axial registry the drain opening  172  that is configured for cooperation therewith. 
         [0037]    The electronic switch portion  240  of the actuator  220  may be formed by a peg that is provided on or partially incorporated into the upstanding side wall  232  of the inner shell  228  of the actuator  220 , and that axially protrudes beyond the lower or free edge thereof. At least the lower, protruding end of the peg may be dimensioned to be receivable into the drain opening  172  during axial up and down movement of the actuator  220  along the cylindrical shaft  132 . The peg may configured as the control for the user operable electronic switch  114 , and to that end include a cavity  242  that accommodates the permanent magnet  118  of the switch discussed above. 
         [0038]    The actuator  220  may thus be rotated around the central axis L between three different positions which, in clockwise order, include: a position in which the actuator  220  is detachable from the body  100  by pulling it upwards; an OFF-position in which the actuator  220  cannot be moved up- or downwards, and the magnet  118  of the electronic switch portion  240  is spatially separated from the magnetic sensor  116  sufficiently far to prevent the switch  114  from switching to the ON-position; and an ON-position in which the actuator  220  can be moved up- and downwards along the central axis L, and in which the magnet  118  of the electronic switch portion  240  resides within the vicinity of the magnetic sensor  116 , causing the switch  114  to be in the ON-state. 
         [0039]    Upon use, a user may first detach the actuator  220  from the body  100  to refill the water reservoir  160  by pouring water into the sink cover  166 , until the water does no longer drain therefrom indicating that the water reservoir  160  is full. To refill the reservoir  160 , the user may conveniently use the hollow, cup-shaped actuator  220  as a small water bucket to transfer water from a tap into the sink cover  166 . This mode of operation does away with the hassle of holding the appliance  1  in a sink to position the sink cover  166  under a tap, and overcomes the need for a split body design, in which the appliance would include a power base and jug that is detachably connectable thereto, as is common in conventional electric kettles. Once the reservoir is filled, the user may reattach the actuator  220 , and turn it around the central axis L through its OFF-position into its ON-position. This will cause the central controller  112  to power the heating element  204  of the steam generator  200  in order to heat up the thermal mass  202  thereof to a temperature well above 100° C. After a brief heating up phase, the user may displace the actuator  220  along the central axis L to feed liquid water from the water reservoir  160  into the steam line  208  extending through the heated thermal mass  202  of the steam generator  200 . This will cause the liquid water to be evaporated virtually instantly, and steam will be forced out of the steam generator  200  through the steam tube  210  that is connected to milk frothing device  180 . A cup of milk may be held at the lower end of the milk suction tube  182  of the milk frothing device, such that milk may be siphoned therefrom, frothed inside the frothing tube  184 , and subsequently discharged back into the cup. When the frothing process is completed, the user may rotate the actuator back from its ON-position to its OFF-position to cut off power to the heating element  204  of the steam generator  200 . 
         [0040]    Although illustrative embodiments of the present invention have been described above, in part with reference to the accompanying drawings, it is to be understood that the invention is not limited to these embodiments. Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, it is noted that particular features, structures, or characteristics of one or more embodiments may be combined in any suitable manner to form new, not explicitly described embodiments. 
       LIST OF ELEMENTS 
       [0000]    
       
           1  milk frothing appliance 
           100  body 
           110  power cord 
           112  central controller 
           114  user operable switch (switchable between ON/OFF-states) 
           116  magnetic sensor reed contact 
           118  permanent magnet 
           120  electric cable between controller and magnetic sensor 
           122  electric cable between controller and heating coil 
           130  hand pump 
           132  cylindrical shaft 
           133  slot for cooperation with radial pin on shaft insert of actuator 
           134  fluid chamber 
           136  piston 
           137  mechanical spring 
           138  piston center pin 
           140  O-ring around piston 
           142  water inlet 
           144  first or water inlet check valve 
           146  water outlet 
           148  second or water outlet check valve 
           150  O-ring between bottom wall of water reservoir and cylindrical shaft 
           160  water reservoir 
           162  bottom wall of water reservoir 
           164  (conical) side wall of water reservoir 
           166  sink cover 
           168  bottom wall of sink cover 
           170  slotted drain opening in bottom wall of sink cover 
           172  drain opening in bottom wall of sink cover configured to receive electronic switch portion of actuator 
           174  side wall of sink cover 
           180  milk frothing device 
           182  milk suction tube (long leg) 
           184  frothing tube (short leg) 
           186  Venturi 
           188  mixing chamber 
           190  air gap 
           200  steam generator 
           202  thermal mass 
           204  heating element 
           206  steam line for steam generation 
           208  water supply end of steam line 
           210  steam discharge end of steam line steam tube 
           220  actuator 
           222  cup-shaped outer shell of actuator (metal) 
           224  central wall of outer shell 
           226  side wall of outer shell 
           228  inner shell of actuator (plastic) 
           230  central wall of inner shell 
           232  side wall of inner shell 
           234  hand pump interface portion 
           236  shaft insert 
           237  radially extending pin on shaft insert 
           238  piston center pin reception recess 
           240  electronic switch portion 
           242  cavity for magnet 
         L central axis of body