Patent Publication Number: US-2010107891-A1

Title: Domestic appliance

Description:
The present invention relates to a coffee machine, and to apparatus for foaming milk. 
     Coffee machines are generally required to have the versatility to produce both “black” coffee beverages, such as espresso, and mixed milk and coffee beverages, such as cappuccino and macchiato. These mixed beverages are formed by adding foamed milk to espresso coffee. Therefore, it is becoming usual for coffee machines to include an apparatus for foaming milk for use in producing these mixed beverages. 
     A known coffee machine includes an apparatus for foaming milk which generates a flow of steam which is conveyed along a channel. The steam is generated from water supplied from a water container for storing water used in brewing espresso coffee within the coffee machine. The channel has a constricted portion leading to a mixing chamber. The mixing chamber is connected to an air supply conduit communicating with the ambient atmosphere, and to a milk supply conduit comprising a nozzle for immersion into milk located within a milk container. The steam increases in velocity, and thus reduces in pressure, as it passes along the constricted portion of the channel. As the steam enters the mixing chamber, a reduced pressure, or partial vacuum, is generated within the mixing chamber. The low pressure within the mixing chamber causes air and milk to be sucked into the mixing chamber from the air supply conduit and the milk supply conduit respectively. Within the mixing chamber, the milk and air are heated by, and mixed with, the steam to produce foamed milk. The foamed milk is conveyed from the mixing chamber to a milk outlet conduit, which may lead either to a dispensing spout from which the foamed milk can be dispensed into a black coffee beverage, or to a second nozzle from which the foamed milk is returned to the milk container. 
     The present invention provides apparatus for foaming milk, comprising a body defining a foaming chamber, a nozzle insertable into milk located in a milk container, a conduit arrangement for conveying milk to the foaming chamber from the nozzle, means for drawing milk through the conduit arrangement to the foaming chamber, a foamed milk outlet configured to return foamed milk to the container, a temperature sensor for monitoring the temperature of milk being supplied to the foaming chamber, and a controller arranged to terminate the drawing of milk along the nozzle depending on the monitored temperature. 
     By monitoring the temperature of the milk being supplied to the foaming chamber and terminating the drawing of milk along the nozzle depending on the monitored temperature, a foaming operation can be terminated when the milk within the container has reached a desired consistency irrespective of the volume of milk within the container. 
     The temperature sensor is preferably arranged to contact milk being drawn through the conduit arrangement so that it is highly responsive to a change in the temperature of the milk. The temperature sensor preferably comprises a thermistor located within the body. 
     The controller is configured to terminate the drawing of milk through the conduit arrangement when the monitored temperature is in the range from 50 to 70° C., more preferably when the monitored temperature is in the range from 60 to 70° C. 
     The use of a second nozzle to return foamed milk to the container can increase detrimentally the size of the apparatus, and can restrict the size and shape of the container to one which is able to accommodate both nozzles. In the preferred embodiment the foamed milk outlet is preferably substantially co-axial with the nozzle, and is preferably configured to return foamed milk to the container over the external periphery of the nozzle. Therefore the present invention also provides apparatus for foaming milk, comprising a body defining a foaming chamber, a nozzle insertable into milk located in a milk container, a conduit arrangement for conveying milk to the foaming chamber from the nozzle, means for drawing milk through the conduit arrangement to the foaming chamber, and a foamed milk outlet for returning foamed milk to the container over the external periphery of the nozzle. 
     By returning foamed milk to the container over the external periphery of the nozzle, only a single nozzle is required to be inserted into the milk to both convey milk to the foaming chamber and return foamed milk to the container. This can enable the foaming apparatus to be relatively compact. Furthermore, the return of milk to the container over the external periphery of the nozzle can be visually appealing, as during use the external surface of the nozzle will be “masked” by a stream of foamed milk returning to the milk container. 
     In the preferred embodiment the foamed milk outlet comprises a plurality of channels radially spaced from and extending along the conduit arrangement. These channels are preferably aligned parallel to each other, and parallel with the longitudinal axis of the nozzle so that a smooth flow of milk is returned to the container. The foamed milk outlet may comprise between three and eight channels located about the conduit arrangement. The channels preferably terminate at the lower surface of the body, and thus may be conveniently formed by machining or otherwise forming a plurality of slots extending from the lower surface of the body. In the preferred embodiment the foamed milk outlet comprises an annular channel for receiving foamed milk from the foaming chamber. 
     The body preferably comprises an upper portion, and a lower portion releasably retained by the upper portion and comprising the foamed milk outlet. This can enable the foamed milk outlet to be easily cleaned by removing the lower portion of the body, and running the lower portion of the body under a tap. A milk supply conduit of the conduit arrangement is preferably releasably retained by the lower portion of the body, preferably in a bore formed in the lower portion. The plurality of channels may thus be formed as a plurality of slots extending along the surface of this bore. The lower portion of the body is preferably formed from flexible material. The foaming chamber may be delimited by the upper portion and the lower portion of the body, and so may be readily cleaned by removing the lower portion of the body and wiping clean the surfaces of the two portions of the body. 
     The milk may be drawn from the milk container by a pump, but in the preferred embodiment the means for drawing milk along the milk supply conduit to the foaming chamber comprises a steam supply conduit for supplying steam to the foaming chamber. The steam supply conduit and the foaming chamber are preferably shaped so that milk is drawn into the foaming chamber by the Venturi effect as the steam enters the foaming chamber. 
     The body is preferably moveable between a stowed position and a deployed position for inserting the nozzle within milk located in a milk container. 
     A separate air supply conduit may be provided for supplying air to the foaming chamber, but in the preferred embodiment an air inlet for supplying air to the apparatus is preferably located in the conduit arrangement, preferably beneath the foamed milk outlet. As the inlet to the air supply conduit may become blocked, for example by dirt and solidified milk, in the preferred embodiment the apparatus comprises means for dislodging matter from the air inlet. The apparatus preferably comprises means for activating the cleaning device as the foaming device moves between the stowed position and the deployed position. As a result the dislodging means can be activated automatically each time the foaming device is moved from the stowed position to the deployed position when foamed milk is to be produced by the apparatus, and each time the foaming device is subsequently moved back to the stowed position for storage. This can enable the air inlet to be sufficiently clear from unwanted matter, such as dirt, solidified milk and other deposits, during the supply of air and milk to the foaming chamber that foamed milk of a repeatable, high quality can be produced by the apparatus. Therefore the present invention further provides apparatus for foaming milk, comprising:
         a housing;   a foaming device movable relative to the housing between a stowed position and a deployed position, the foaming device comprising a foaming chamber, a steam supply conduit for supplying steam to the foaming chamber, a fluid supply conduit for supplying air and milk to the foaming chamber, and an air inlet from which air is supplied to the fluid supply conduit;   means for dislodging matter from the air inlet; and   means for activating the cleaning device as the foaming device moves between the stowed position and the deployed position.       

     The dislodging means is preferably mounted on the foaming device. 
     The dislodging means may be arranged to direct a pressurised stream of fluid, for example air or water, towards or on to the air inlet to dislodge matter therefrom. However in the preferred embodiment the dislodging means comprises a moveable cleaning member for dislodging matter from the air inlet. For example, the dislodging means may comprise a flexible member, such as a diaphragm, comprising an aperture defining the air inlet. In this case, the activating means may be arranged to engage the flexible member as the foaming device moves between the stowed position and the deployed position. This can cause the flexible member to flex, thereby dislodging matter from the air inlet. In the preferred embodiment, the dislodging means comprises a cleaning member which is moveable relative to the air inlet to dislodge matter therefrom. The cleaning member is preferably located partially within the air inlet during use of the apparatus. Consequently, dirt can accumulate within a substantially annular aperture located between the outer periphery of the moveable cleaning member and the inner periphery of the air inlet. This dirt can be dislodged from this aperture by the movement of the cleaning member relative to the air inlet. The activating means is preferably arranged to urge the cleaning member in a direction extending towards the air inlet to cause the matter to be dislodged from the air inlet. However, the activating means may be arranged to vibrate the cleaning member within the air inlet, or to move cleaning member in a curved or circular path within the air inlet, to dislodge matter from the air inlet. 
     The use of a cleaning member for dislodging matter from the air inlet can thus provide a relatively cheap and simple arrangement for unblocking the air inlet, and so the present invention also provides apparatus for foaming milk, comprising:
         a housing; and   a foaming device movable relative to the housing between a stowed position and a deployed position, the foaming device comprising a foaming chamber, a steam supply conduit for supplying steam to the foaming chamber, a fluid supply conduit for supplying air and milk to the foaming chamber, an air inlet from which air is supplied to the fluid supply conduit, and an air inlet cleaning member;   the housing comprising means for moving the air inlet cleaning member as the foaming device moves between the stowed position and the deployed position to dislodge matter from the air inlet.       

     The cleaning member may be moved as the foaming device moves between the stowed position and the deployed position using one of a number of different techniques. For instance, a magnet or electromagnet may be located on the housing to move the cleaning member. In the preferred embodiment the means for moving the cleaning member comprises an abutment member for engaging the cleaning member as the foaming device moves between the stowed position and the deployed position. The foaming device is preferably slidably moveable relative to the housing, but alternatively it may be rotatable or pivotable relative to the housing. 
     The abutment member may be rigidly attached to the housing, or it may be integral therewith. At least one of the abutment member and the cleaning member may comprise a curved, angled or otherwise profiled surface for engaging the other of the abutment surface and the cleaning member so that the cleaning member moves smoothly relative to the air inlet. 
     The cleaning member is preferably pushed by the abutment member from a first position to a second position relative to the air inlet. A resilient member, preferably in the form of a spring, may be provided for biasing the cleaning member in a direction extending away from the air inlet, that is, towards the first position, so that the cleaning member is returned automatically to the first position once the cleaning member has become spaced from the abutment member. 
     The cleaning member may take any suitable form for dislodging matter from the air inlet. For example, the cleaning member may comprise a brush having flexible bristles. In the preferred embodiment, the cleaning member comprises a pin. 
     The present invention also provides a domestic appliance comprising apparatus as aforementioned, and which is preferably in the form of a coffee machine. 
     The present invention further provides a method of foaming milk, comprising inserting a nozzle of a milk supply conduit into milk located in a milk container, drawing milk from the container and conveying the drawn milk to a foaming chamber, returning foamed milk to the container from the foaming chamber, monitoring the temperature of milk being supplied to the foaming chamber, and terminating the drawing of milk along the milk supply conduit depending on the monitored temperature. 
     Features described above in connection with apparatus aspects of the invention are equally applicable to the method aspect of the invention, and vice versa. 
    
    
     
       An embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: 
         FIG. 1  is a perspective view of a domestic appliance, with apparatus for foaming milk in a stowed position; 
         FIG. 2  is a schematic illustration of various components of the domestic appliance of  FIG. 1 ; 
         FIG. 3  is a perspective view of the domestic appliance of  FIG. 1  with the apparatus for foaming milk in a deployed position; 
         FIG. 4  is a side view of the apparatus for foaming milk, with a foaming device of the appliance in a deployed position; 
         FIG. 5  is a cross-sectional view of the apparatus of  FIG. 4 ; and 
         FIG. 6  is a cross-sectional view of part of the foaming device of  FIG. 5 . 
     
    
    
       FIG. 1  illustrates a domestic appliance. In this embodiment the domestic appliance is in the form of a coffee machine  10  that is suitable for domestic use in, for example, a kitchen environment. The coffee machine  10  has a substantially cuboid outer casing  12 . The outer casing has an upper surface  14  and a front surface  16 . A spout  18  is located in the front surface  16  of the outer casing  12 . The spout  18  is moveable relative to the casing  12  between a stowed position, illustrated in  FIG. 1 , in which the spout  18  is stored within the casing  12  and a deployed position in which the spout  18  dispenses coffee from the coffee machine  10 . A more detailed description of the spout  18  can be found in co-pending application PCT/GB2008/001228. 
     An access door  20  is formed in the outer casing  12 . The access door  20  forms a part of the front surface  16  of the casing  12  and is slidably openable between a stowed position, in which the access door  20  is flush with the front surface  16  of the casing  12 , and a deployed position. The access door  20  is attached to an ingredient drawer which moves therewith for receiving a beverage ingredient (for example, coffee beans or pre-ground coffee) when the access door  20  is in its deployed position. 
     The coffee machine  10  comprises a user-operable control panel  22  located on the upper surface  14  of the casing  12 . The control panel  22  may comprise a touch-sensitive screen or a plurality of buttons to enable the user to control the operation of the coffee machine  10 . For example, the movement of the access door  20  and the spout  18  relative to the casing can be actuated using the control panel  22 . 
     A water reservoir  24  is located adjacent the outer casing  12  and is attached thereto by a base portion  26 . The water reservoir  24  has a substantially cuboid body  28  which may be formed from a transparent material such as a plastics material, or from an opaque plastics material. In this latter alternative the body  28  may be provided with a window to enable the user to see the volume of water within the water reservoir  24 . An aperture  30  is formed in the upper end of the body  28  to enable the user to introduce water to the water reservoir  24 . The aperture  30  is closed by a hinged lid  32  which is openable by a user. The lid  32  is shown in the closed position in  FIG. 1 . The operation of the lid  32  is described in more detail in co-pending application GB 0723823.1 and will not be discussed any further here. 
       FIG. 2  illustrates schematically various components of the coffee machine  10 . A valve unit  34  connects the water reservoir  24  to the base portion  26 . The valve unit  34  has a first portion located in the body  28  of the water reservoir  24  and a second portion located on the base portion  26 . The water reservoir  24  is removable from the base portion  26  to enable the water reservoir  24  to be placed under a domestic water tap for filling. The water reservoir  24  can be released from the base portion  26  by pulling the water reservoir  24  upwardly away from the base portion  26 . When this occurs, the first and second portions of the valve unit  34  are separated. This action automatically closes the valve unit  34 , preventing leakage of water from the water reservoir  24 . 
     A reservoir conduit  36  located in the base portion  26  connects the water reservoir  24  to a pump  38 . The pump  38  is located within the outer casing  12  of the coffee machine  10 . In this embodiment, the pump  38  is a solenoid pump. An inline heater element  40  is located downstream of the pump  38  for heating water drawn from the water reservoir  24  by the pump  38 . The heater element  40  is arranged to heat the water passing therethrough to one of two different temperatures, a first temperature of around boiling point, and a second temperature in the range from 120 to 140° C. to generate steam. A supply conduit  42  is located downstream of the heater element  40  and is arranged to supply the water, when heated to the first temperature, to a brewing assembly  44 . A three-way valve  46  is located within the supply conduit  42  to selectively divert water, when heated to the second temperature, away from the brewing assembly  44  to apparatus  50  for foaming milk supplied thereto from a milk container  52  located alongside the coffee machine  10 . 
     Ground coffee is supplied to the brewing assembly  44  by an ingredient dispenser  54 . The ingredient dispenser  54  is located within the ingredient drawer so that beverage ingredients can be placed therein when the access door  20  is in the open position. The brewing assembly  44  is arranged to prepare a coffee beverage from the ground coffee and water at the first temperature which are supplied thereto by the ingredient dispenser  54  and the supply conduit  42  respectively. 
     A dispensing conduit  56  connects the brewing assembly to the spout  18  to supply the spout  18  with a prepared coffee beverage for dispense to a user. A waste grounds container  58  is provided below the brew chamber assembly  44 . Waste coffee grounds are deposited into the waste grounds container  58  from the brewing assembly  44  following the completion of a beverage preparation by the coffee machine  10 . The waste grounds container  58  may be located in, or form part of, a drawer of the outer casing  12  of the coffee machine  10  to allow the waste grounds container  58  to be accessed readily by the user for emptying. 
     A controller  60  is provided for controlling the operation of the coffee machine  10 . The controller  60  is arranged to receive signals from the control panel  22 , and to actuate the operation of the pump  36 , heater element  38 , three-way valve  40 , brew chamber assembly  44 , apparatus  50  and ingredient dispenser  54  in response thereto. 
     The apparatus  50  for foaming milk is illustrated in more detail in  FIGS. 3 to 6 . The apparatus  50  comprises a housing  70  which is moveable relative to the casing  12  between a stowed position, as illustrated in  FIG. 1 , and a deployed position, as illustrated in  FIG. 3 . The housing  70  has a front cover  72  which is flush with the front surface  16  of the casing  12  when the housing  70  is in its stowed position. The movement of the housing  70  from the stowed position to the deployed position may be affected by a solenoid mechanism which is actuated by pressing an appropriate button on the control panel  22 . To return the housing  70  to the stowed position the user may simply push the front cover  72  of the housing  70  towards the casing  12  until the front cover  72  is flush with the front surface  16  of the casing  12 . 
     The apparatus  50  comprises a foaming device  74  for forming foamed milk from milk, air and steam. The foaming device  74  is slidably moveable relative to the housing  70  between a stowed position in which the foaming device  74  is located substantially entirely within the housing  70 , and a deployed position, as illustrated in  FIG. 3 , in which part of the foaming device  74  protrudes from the lower surface  76  of the housing  70 . A button  78  of a manually-operable sliding mechanism may be provided on one side of the housing  70  for allowing the user to slide the foaming device  74  between the stowed position and the deployed position when the housing  70  is in a deployed position. In this example the foaming device  74  is moveable substantially vertically relative to the housing  70 . 
     The foaming device  74  is illustrated in more detail in  FIGS. 5 and 6 . The foaming device  74  comprises a body  80  having an upper portion  82  formed from a rigid material, preferably a plastics material, and a lower portion  84  formed from a flexible material, preferably rubber. The lower portion  84  is releasably retained by the upper portion  82  so that the user can remove the lower portion  84  from the upper portion  82  for cleaning. The upper portion  82  and the lower portion  84  of the body  80  together define a foaming chamber  86  within which steam heats milk and air to form heated, foamed milk. The upper portion  82  of the body  80  comprises a steam supply conduit  88  for supplying steam to the foaming chamber  86 . With reference to  FIG. 6 , the steam supply conduit  88  has a constricted portion  90  from which steam enters the foaming chamber  86 . The steam supply conduit  88  is arranged to receive steam from a tube (not shown) extending within chamber  92  located within the housing  70 . This tube is connected at one end to a steam inlet conduit  94  for conveying steam from the three-way valve  46  to the housing  70  and at the other end to the steam supply conduit  88 . 
     The upper portion  82  and the lower portion  84  of the body  80  together define a fluid supply conduit  100  for supplying milk and air to the foaming chamber  86 . The fluid supply conduit  100  has an outlet  102  for conveying milk and air into the foaming chamber  86 . The outlet  102  is located about the constricted portion  90  of the steam supply conduit  88 . The fluid supply conduit  100  is in fluid communication with a milk supply conduit  104  which is received in a bore formed in the lower portion  84  of the body  80 . The fluid supply conduit  100  and the milk supply conduit  104  together form a conduit arrangement for conveying milk and air to the foaming chamber  86 . The milk supply conduit  104  has a milk inlet  106  for receiving milk, an air inlet  108  for receiving air for the external environment, and a fluid outlet  110  for supplying a mixture of air and milk to the fluid supply conduit  100 . The fluid inlet  106  and the fluid outlet  110  are located at opposite ends of the milk supply conduit  104 , with the air inlet  108  being located in the wall of the milk supply conduit  104 , preferably around midway between the fluid inlet  106  and the fluid outlet  110 . 
     The foaming device  74  also comprises a milk supply nozzle  112  located about the lower portion of the milk supply conduit  104 . The nozzle  112  extends downwardly from the body  80  for insertion into milk located in a milk container  52  positioned beneath the foaming device  74 . The upper portion of the milk supply conduit  104  is preferably shaped so as to be substantially flush with the outer surface of the nozzle  112 . The nozzle  112  is preferably formed from stainless steel. 
     The lower portion  84  of the body  80  comprises a foamed milk outlet  114  from which foamed milk is returned to the milk container  52 . The foamed milk outlet  114  is located about the milk supply conduit  104 , and is preferably substantially co-axial with the milk supply conduit  104  and the nozzle  112 . The foamed milk outlet  114  comprises an annular upper portion  116  for receiving foamed milk from a foamed milk supply conduit  118  extending downwardly from the foaming chamber  86  and a lower portion  120 . In this example, the lower portion  120  comprises a plurality of channels or slots spaced about and extending along the outer surface of part of the milk supply conduit  104 . Each of the channels extends downwardly from the upper portion  116  to the bottom surface  122  of the lower portion  84  of the body  80 . 
     The temperature of the milk entering the foaming chamber  86  is monitored by a temperature sensor  124 . In this example the temperature sensor  124  may be located at the lower end of a bore  126  extending downwardly through the upper portion  82  of the body  80  and which terminates just above fluid supply conduit  100 . Alternatively, this bore  126  may extend into the fluid supply conduit  100  so that the temperature sensor  124  is in contact with the milk passing through the fluid supply conduit  100 . 
     The apparatus  50  further comprises a cleaning device  130  for cleaning the air inlet  108 . The cleaning device  130  comprises a cleaning member in the form of a pin  132  which is moveable relative to the air inlet  108 . The pin  132  has a relatively wide head  134 , and a relatively narrow tip  136  which is partially located within the air inlet  108 . The outer periphery of the tip  136  defines with the inner periphery of the air inlet  108  a narrow annular aperture through which air enters the milk supply conduit  104 . The distance between the tip  136  and the air inlet  108  is exaggerated in  FIG. 6 ; in this example the diameter of the external periphery of the tip  136  of the pin  132  is around 2 mm whereas the diameter of the internal periphery of the air inlet  108  is around 2.1 mm. 
     The pin  132  is located within a cylindrical air duct  138  extending substantially orthogonally to the milk supply conduit  104 . The pin  132  is shaped so that the head  134  of the pin  132  protrudes from the end of the duct  138  which is remote from the air inlet  108 . The pin  132  is biased in direction extending away from the air inlet  108  by a resilient member  140  located within the air duct  138 . The resilient member  140  is preferably in the form of a compression spring extending about the pin  132 , and having one end engaging a flanged surface  142  extending partially about the base of the head  134  and another end engaging the wall  144  of the air duct  138  in which the air inlet  108  is located. 
     The housing  70  comprises means for moving the pin  132  relative to the air inlet  108  to dislodge matter, such as dirt or solidified milk, which may have accumulated within the annular aperture. In this example, the housing  70  comprises an abutment member  150  for engaging the head  134  of the pin  132  as the foaming device  74  is moved between the stowed position and the deployed position. The abutment member  150  preferably extends towards the front cover  72  of the housing  70 , and is preferably aligned parallel with the pin  132 . As illustrated in  FIGS. 5 and 6 , the abutment member  150  has a curved outer surface  152  for engaging a curved outer surface  154  of the head  134  of the pin  132  so that the pin  132  moves axially, that is along the longitudinal axis X-X of the pin  132 , relative to the air inlet  108 . The outer surfaces  152 ,  154  need not be curved, for example the surfaces may be angled, or wedge-shaped so that the head  134  of the pin  132  and the abutment member  150  are both either triangular or trapezoidal in cross-section. 
     In use, when the user requires milk to be foamed the user presses the appropriate button on the control panel  22  to cause the housing  70  to be moved from the stowed position to the deployed position. The user positions a milk container, containing milk to be foamed, beneath the foaming device  74  and, using the button  78 , slides the foaming device  74  from its stowed position to its deployed position so that the end of the nozzle  112  is immersed within the milk in the container. 
     As the foaming device  74  is lowered towards its deployed position, the head  134  of the pin  132  contacts the abutment member  150 . With further lowering of the foaming device  74 , the curved outer surface  154  of the head  134  of the pin  132  slides over the curved outer surface  152  of the abutment member  150 , which pushes the head  134  of the pin  132  from the position illustrated in  FIG. 6  gradually towards the air inlet  108  against the force of the resilient member  140 . The tip  136  of the pin  132  thus moves relative to the air inlet  108  so as to cause deposits and other matter to be dislodged from the annular aperture located between the outer periphery of the tip  136  and the inner periphery of the air inlet  108 . The extent of the movement of the pin  132  relative to the air inlet  108  is determined by the distance x along axis X-X between the end of the head  134  of the pin  132  and the end of the abutment member  150 . In this example the distance x is in the range from 1 to 5 mm. Once the end of the head  134  of the pin  132  has been lowered beyond the end of the abutment member  150 , the force of the resilient member  140  urges the pin  132  back towards the position illustrated in  FIG. 6 . Again, the curved outer surfaces  152 ,  154  ensure that the pin  132  moves gradually back to the position illustrated in  FIG. 6  as the foaming device  74  is lowered. 
     Following the lowering of the foaming device  74  to the deployed position, the user presses an appropriate button of the control panel  22  to commence the milk foaming process. The controller  60  activates the heating element  40  so that the heating element  40  rises to a temperature at which it is able to heat water received from the water reservoir  24  to the second temperature, that is, to a temperature in the range from 120 to 140° C., to generate steam. The controller  60  may also issue a signal to the three-way valve  46  to cause the three-way valve  46  to move to a position at which water is diverted away from the brewing assembly  44  and into the steam inlet conduit  94 . However, if this position is the default position of the three-way valve  46  then no such signal needs to be issued by the controller  60 . 
     Once the heating element  40  has reached the required temperature, the controller  60  activates the pump  38  to draw water from the water reservoir  24 . The water is pumped through the heater element  40 , wherein it is converted into steam. The pressurised steam is diverted into the steam inlet conduit  94  by the three-way valve  46 , and is conveyed thereby into the tube located within the chamber  92  of the housing  70 . The pressurised steam is forced into the steam supply conduit  88 , wherein it passes through the constricted portion  90  of the steam supply conduit  88  and is ejected into the foaming chamber  86 . The increase in the velocity of the steam as it passes through the constricted portion  90  of the steam supply conduit  88  generates a reduced pressure, or partial vacuum, within the foaming chamber  86  due to the steam collapsing and forming vapour as it enters the foaming chamber  86 . This reduced pressure causes milk to be drawn up the nozzle  112  from the milk container, and air to be sucked through the air inlet  108  from the external environment. The milk and air mixes within the milk supply conduit  104 , resulting in a mixture of milk and air being drawn along the fluid supply conduit  100  from the milk supply conduit  104  and entering the foaming chamber  86 , wherein the steam heats the air and milk to form heated, foamed milk having a temperature in the range from 50 to 70° C. 
     The foamed milk is forced from the foaming chamber  86  and into the foamed milk supply conduit  118 , which conveys the foamed milk to the annular upper portion  116  of the foamed milk outlet  114 . The foamed milk enters the plurality of slots forming the lower portion  120  of the foamed milk outlet  114 , within which the foamed milk flows downward along the external periphery of the milk supply conduit  104 . The foamed milk leaves the foaming device  74  from the ends of the slots, and continues to flow downward along the outer surface of the nozzle  112  to the milk container. 
     The slots thus produce a relatively smooth flow of foamed milk which passes downward along the outer surface of the nozzle  112  to the milk container. 
     As a consequence of the, relatively warm, foamed milk returning to the milk container from which, relatively cold, milk is supplied to the foaming chamber  86 , the temperature of the milk within the milk container, and thus the temperature of the milk entering the foaming chamber  86 , will increase as the foaming process continues. During the foaming process, the controller  60  receives signals from the thermistor  124  located within the fluid supply conduit  100  which are indicative of the temperature of the milk passing through the fluid supply conduit  100 . When the temperature of milk passing through the fluid supply conduit  100  reaches a set value, which may be in the range from 50 to 70° C., the controller  60  stops the pump  38 . This terminates the supply of steam to the foaming device  74 , which in turn terminates the drawing of milk from the milk container to the foaming device  74 . 
     Using the button  78 , the user slides the foaming device  74  back to its stowed position in the housing  70 . As the foaming device  74  moves upward relative to the housing  70 , the head  134  of the pin  132  again contacts the abutment member  150 . With further raising of the foaming device  74 , the curved outer surface  154  of the head  134  of the pin  132  slides over the curved outer surface  152  of the abutment member  150 , which pushes the head  134  of the pin  132  from the position illustrated in  FIG. 6  gradually towards the air inlet  108  against the force of the resilient member  140 . The tip  136  of the pin  132  thus moves relative to the air inlet  108  so as to dislodge deposits, such as solidified milk and airborne dirt particles drawn into the air duct  138  during the foaming process, from the annular aperture located between the outer periphery of the tip  136  and the inner periphery of the air inlet  108 . Once the end of the head  134  of the pin  132  has been raised beyond the end of the abutment member  150 , the force of the resilient member  140  urges the pin  132  back towards the position illustrated in  FIG. 6 . Again, the curved outer surfaces  152 ,  154  ensure that the pin  132  moves gradually back to the position illustrated in  FIG. 6  as the foaming device  74  is raised. Once the foaming device  74  has been raised to the stowed position, the user may push the housing  70  back to its stowed position within the casing  12  for storage.