fig1 - 6 schematically illustrate an exemplary embodiment of a milk frothing appliance 1 according to the present invention , whose construction and operation are discussed below . as can be seen best in fig1 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 . 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 fig3 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 fig3 , 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 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 fig2 ) 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 . 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 . 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 . 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 . 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 fig6 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 . 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 . 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 . the actuator 220 of the milk frothing appliance 1 , which is shown in isolation in fig5 , 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 . 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 fig1 ), 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 . 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 . 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 . in the depicted embodiment ( see in particular fig4 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 . 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 . 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 . 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 . 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 . 133 slot for cooperation with radial pin on shaft insert of actuator 150 o - ring between bottom wall of water reservoir and cylindrical shaft 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
a milk frothing appliance , comprising :— a water reservoir ;— a steam generator ;— a milk frothing device that is fluidly connected to the steam generator ; and — a hand pump that is fluidly connected to both the water reservoir and the steam generator , comprising a manually operable actuator 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 .