Abstract:
The invention relates to a docking station ( 10 ) for a skin treatment device ( 30 ) having a cooling member ( 32 ). According to the invention, the docking station comprises: an evacuator ( 18 ) for lowering a pressure inside the cooling member, and means ( 28 ) for connecting an interior of the cooling member to a sorbent ( 24 ). The sorbent preferably comprises a zeolite. The invention further relates to a skin treatment device ( 30 ), particularly an epilator, comprising a cooling member ( 32 ) for containing a cooling agent ( 34, 36 ). According to the invention, the skin treatment device comprises means ( 28 ) for connecting the cooling member to a docking station ( 10 ) as mentioned above. The cooling agent is preferably water or an aqueous solution.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates to a docking station for a skin treatment device having a cooling member for containing a cooling agent. 
         [0002]    The invention further relates to a skin treatment device, particularly an epilator, comprising a cooling member for containing a cooling agent. 
       BACKGROUND OF THE INVENTION 
       [0003]    Removal of hair (epilation) from various parts of the body for cosmetic, medical or other purposes is a routine practice. Hair on non-facial skin is usually removed by plucking, and various devices for such hair removal are known in the art. 
         [0004]    As plucking of hair can be very painful, EP 0 348 862 A2 proposes an auxiliary skin cooling device for a hair-removing apparatus. The skin cooling device is designed to cool the skin during the removal of hair and thereby achieves an anaesthetizing effect. The described cooling device preferably comprises a heat-accumulating cooling element, such as a small compartment filled with a phase-changing liquid having a large heat capacity. The cooling element needs to be cooled before use, which is typically done by placing the cooling element or the entire hair-removing apparatus in a cold environment, for example, a freezer, and by leaving it there at least until the phase-changing liquid has frozen, or until the cooling element has reached a thermal equilibrium with the cold environment. When brought into contact with the skin, the pre-cooled cooling element absorbs heat, thereby cooling the skin. 
         [0005]    However, the necessity of placing the cooling element in a cold environment before use involves a number of drawbacks. Placing the cooling element in a freezer reduces the space available for other items in the freezer. The cooling member must also be food-safe, which prevents a number of otherwise suitable substances from being used as cooling liquid. A major drawback is that the cooling member cannot be refrozen quickly when it defrosts during an extended epilation session. In fact, the cooling member must typically be stored in a freezer for several hours before it has reached a sufficiently low temperature. During a break of the epilation session, the cooling member has to be put back into a cold environment so as to prevent it from defrosting. Finally, a cold environment for cooling the cooling member is not always readily available to the user. 
         [0006]    It is an object of the invention to provide means and methods that overcome these drawbacks. 
         [0007]    This object is achieved by the features of the independent claims. Further specifications and preferred embodiments of the invention are stated in the dependent claims. 
       SUMMARY OF THE INVENTION 
       [0008]    According to the invention, the docking station comprises: an evacuator for lowering a pressure inside the cooling member of the skin treatment device, and means for connecting an interior of the cooling member for containing the cooling agent to a sorbent. The evacuator is preferably a vacuum pump. By pumping gas out of the cooling member, the pressure inside the cooling member may be lowered below the vapor pressure of the cooling agent inside the cooling member. When the inside of the cooling member is connected to the sorbent, the latter rapidly adsorbs vapor of the cooling agent, thereby causing a further evaporation of the cooling agent and lowering the cooling agent&#39;s temperature until it freezes. The cooling principle as such is known from U.S. Pat. No. 5,207,073. As has been pointed out in this document, the pressure of the cooling agent needs to be below the vapor pressure so as to ensure that the cooling agent freezes entirely and not only at its surface. It is therefore advantageous to provide a seal between the cooling member and the sorbent which is removed only when the pressure has reached a sufficiently low value. The vapor pressure is about 5 mbar for water at room temperature and less for aqueous solutions. 
         [0009]    The sorbent preferably comprises a water-adsorbing substance. This allows various aqueous solutions to be used as cooling agents. 
         [0010]    In accordance with a preferred embodiment, the sorbent comprises a zeolite. This porous mineral is known for its superb adsorption characteristics for water and is readily available. Zeolite cooling is certainly one of the most efficient ways of rapidly freezing small quantities of water. First tests indicate that 480 g of zeolite are saturated after twenty cooling applications, each application using 25 ml of water. The zeolite thus has to be either replaced or regenerated (dried). Regeneration is possible by heating the zeolite, e.g. by placing it in a thermal or microwave oven. 
         [0011]    The docking station may comprise a cartridge holder for receiving a replaceable cartridge containing the sorbent. A cartridge containing a saturated quantity of sorbent can thus be replaced by a cartridge containing an unsaturated quantity of sorbent. The cartridge preferably comprises a water-tight housing to prevent the sorbent from adsorbing water while not in use. In accordance with a preferred embodiment, the sorbent can be removed from the cartridge and put back into the cartridge by the user. This enables the user to regenerate the sorbent by placing it in, for example, a kitchen oven or a microwave oven. 
         [0012]    The docking station may comprise a heater for drying the sorbent. A saturated quantity of sorbent can thus be regenerated (dried, if the cooling agent is water), using the docking station. 
         [0013]    The docking station may comprise means for engaging the skin treatment device. The skin treatment device may thus be firmly kept in an advantageous position relative to the docking station, reducing mechanical strain in the contact area where the cooling member is connected to the sorbent. 
         [0014]    The docking station may comprise a contact for charging a battery of the skin treatment device. A battery of the skin treatment device can thus be charged while the device is docked to the docking station. 
         [0015]    The docking station may comprise a pressure sensor for sensing the pressure of gas inside the cooling member. The docking station preferably further comprises a control unit for controlling the evacuator as a function of information received from the pressure sensor. The pressure sensor is not essential if the system is tight and remains tight while the epilator is docked to the docking station. However, it may be used advantageously for detecting the presence of a leak in the system, or for regulating the power of the evacuator. 
         [0016]    According to the invention, the skin treatment device comprises means for connecting the interior of the cooling member to a docking station as described above. In accordance with a preferred embodiment, the means comprise a duct designed to engage with a complementary duct of the docking station. 
         [0017]    In accordance with a preferred embodiment, the cooling agent is water or an aqueous solution. Water is safe, readily available, has a large heat capacity and allows regeneration of the sorbent by heating. 
         [0018]    The connecting means are preferably designed to be open when the skin treatment device is coupled to the docking station, and closed otherwise. The cooling agent may thus flow from the cooling member to the docking station only when the skin treatment device is docked to the docking station. 
         [0019]    According to the invention, a method of cooling a cooling member of a skin treatment device comprises the steps of: 
         [0020]    the skin treatment device engaging with a docking station; 
         [0021]    the docking station lowering the pressure inside the cooling member; and 
         [0022]    the docking station establishing a connection from the interior of the cooling member to a sorbent. 
         [0023]    The docking station preferably lowers the pressure inside the cooling member by pumping out vapor. The docking station preferably establishes the connection between the interior of the cooling member and the sorbent when the pressure in the cooling member has dropped below a predetermined value, preferably below the vapor pressure of the agent. 
         [0024]    The method may further comprise a step of heating the sorbent. 
         [0025]    In accordance with a preferred embodiment, the method may further comprise a step of inserting a cartridge containing the sorbent into a cartridge holder of the docking station. 
         [0026]    The method may further comprise a step of detaching the skin treatment device from the docking station. The skin treatment device can thus be separated completely from the docking station for ease of handling during a skin treatment session. 
         [0027]    It is to be noted that the invention may be employed advantageously for various types of skin treatment for which a pain-reducing cooling effect is desired, including epilation, skin surgery, tattooing, and wellness applications. 
         [0028]    These and other aspects of the invention are apparent from and will be elucidated with reference to the embodiments described hereinafter. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0029]      FIG. 1  is a schematic view of a docking station and a skin treatment device according to the invention. 
           [0030]      FIG. 2  is a plot of the quantity of zeolite required for cooling 25 ml of water from 30° C. down to 0° C. as a function of the duration of the cooling process. 
           [0031]      FIG. 3  is a plot of the quantity of zeolite required for cooling water from 30° C. down to 0° C. within 60 seconds as a function of the quantity of water that is cooled. 
           [0032]      FIG. 4  is an oblique view of a docking station according to the invention, with an epilator docked to the docking station. 
           [0033]      FIG. 5  is a view from a different perspective of the docking station shown in  FIG. 4 . 
           [0034]      FIG. 6  is a flow chart of a method according to the invention. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0035]    Similar or analogous features appearing in different Figures are designated by the same reference numerals and are not necessarily described more than once. 
         [0036]      FIG. 1  shows diagrammatically a docking station  10  comprising a housing  12 , a sorbent  24 , a duct  26 , a vacuum pump  18 , an outlet  22 , a controller  16 , a button  14  referred to as the “ice” button, and a pressure sensor  20 . The sorbent  24  has an airtight protective seal cladding  38 . The sorbent preferably consists of zeolite, but any other suitable water-adsorbing material may be used instead. Removably attached (docked) to the docking station is an epilator  30  comprising a cooling member  32  containing water or an aqueous solution  34 , and possibly a certain quantity of vapor  36  or air. A portion of the outer surface of the cooling member  32  provides a skin contact surface  44  (not shown here but in  FIG. 4 ). The interior of the cooling member  32 , i.e. the volume containing the water  34  and the vapor (or air)  36 , is connected at a docking point  28  via the duct  26  to the docking station  10 . The interior of the cooling member  32  and the sorbent  24  thus communicate. The docking point  28  is designed in such a way that it effectively seals the duct  26  when the epilator  30  is removed (undocked) from the docking station  10  so as to prevent water from leaking out. This can be realized, for example, by means of a valve or a spring that automatically seals the duct  26  when the epilator is undocked. Similarly, the cooling member  32  is automatically sealed when undocked. The pump  18  is arranged between the duct  26  and the outlet  22 . The pressure sensor  20  measures the pressure in the duct  26  and transmits the measured values to the controller  16 . When a user presses the ice button  14 , the controller  16  triggers the pump  18  to pump gas out of the cooling member  32  (and possibly out of the sorbent  24 ), thereby reducing the pressure within the cooling member  32 . When the pressure drops below a certain critical value, typically about 5 mbar, the sorbent  24  starts adsorbing the water vapor  36  at a significant rate, causing more water  34  to evaporate and lowering the temperature of the water  34  until it freezes. The evaporation transfers thermal energy initially contained in the water  34  to the water vapor  32  which is adsorbed by the sorbent  24 , causing the latter to heat up. When the water  34  has frozen, no further significant quantity of water  34  evaporates, although some water molecules may still sublimate. The cooling then stops automatically. The pump preferably operates until the cooling stops because the vapor pressure to be attained decreases as the temperature decreases. Pumping until the cooling stops is also advantageous if the system is imperfectly sealed. It is noted that the Figure only shows some essential elements. The docking station may comprise additional elements for improving its efficiency. It may be particularly envisaged to arrange an additional pneumatic element, e.g. an electro-pneumatic valve, between the sorbent  24  and the duct  26  and to couple the additional pneumatic element to the controller  16  so as to prevent vapor  36  from being adsorbed by the sorbent  24  as long as the pressure measured by the pressure sensor  20  exceeds the vapor pressure of the water  34 . 
         [0037]    In the embodiment described above with reference to  FIG. 1 , the vacuum pump  18  is arranged parallel to the sorbent  24 . In accordance with an alternative embodiment (not shown), the pump  18  and the sorbent  24  are arranged in series so that the pump  18  is capable of pumping vapor  36  from the cooling member  32  through the sorbent  24 . Whereas arranging the pump  18  and the sorbent  24  in series may shorten the lifetime of the sorbent  24 , it may increase the freezing power and the reliability of the system  10 ,  30 . The pump may either precede or succeed the sorbent with respect to the flow direction of the vapor during the pumping process. The pump  18  preferably succeeds the sorbent  24  so that, during use, vapor first flows through the sorbent  24  and then through the pump  18 . 
         [0038]      FIG. 2  shows the estimated quantity of zeolite required for cooling 25 ml of water from 30° C. down to 0° C. as a function of the duration of the cooling process. Preliminary calculations predict that 25 ml of water may be cooled down from 30° C. to 0° C. within 45 seconds by using about 180 grams of zeolite. 
         [0039]    Plotted in  FIG. 3  is the quantity of zeolite required for cooling water from 30° C. down to 0° C. within 60 seconds, as a function of the quantity of water that is cooled. 
         [0040]      FIG. 4  shows a docking station  10  with an epilator  30  docked to it. The epilator  30  comprises a handpiece  40 , an epilating member  46  comprising clamping discs surrounded by a cap  42 , and a cooling member (ice accu)  32  having a skin contact surface  44 . The docking station comprises a housing  12  having a generally cuboidal shape. A front portion  54  and a top portion of the housing define a concave portion  48 ,  50  for receiving the epilator  32 . The concave portion  48 ,  50  is dimensioned in such a way that the epilator can be easily attached to and removed from the docking station  10 . The concave portion is composed of a generally horizontal lower concave portion  50  and a generally vertical upper concave portion  48 . The lower concave portion  52  has an oval opening  52  forming an entrance to a cavity having a cross-section that is slightly larger than a cross-section of the handpiece  40  of the epilator  30  so that a lower portion (not visible in the Figure) of the handpiece  40  fits into the opening  52 , such that the epilator  32  is secured to the housing  12 . The epilator  30  is thus docked to the docking station  10  in an upright position, with about two thirds of the outer surface of the handpiece  40  being freely accessible by a user, allowing easy docking and undocking. Also arranged on the front portion  54  of the housing  12  is the ice button  14 , described with reference to  FIG. 1 , and an indicator lamp  56  comprising a green and a red light-emitting diode (LED). The indicator lamp  56  is controlled by the controller  16  described with reference to  FIG. 1 . While the freezing is in process, the indicator lamp  56  emits red light. When the freezing process has stopped, the indicator lamp  56  emits green light, thereby indicating to the user that the cooling member  32  of the epilator  30  is operational. 
         [0041]      FIG. 5  shows the docking station  10  viewed from below at an oblique angle, with the epilator  30  of  FIG. 4  undocked. The epilator  30  is therefore not visible in the Figure. With the epilator  30  now being separated from the docking station  10 , it can be seen that the upper concave portion  48  is provided with a docking point  28  and a spring leaf  58  for ensuring a firm and watertight connection between the cooling member of the epilator and the sorbent  24  (see  FIG. 1 ) contained in the docking station  10 . A generally rectangular bottom plate  68  of the docking station  10  has a circular opening  70  forming an entrance to a cylindrical cavity within the docking station  10  for receiving a cylindrical cartridge  60 . The cartridge  60  has a watertight cartridge housing  38  containing a sorbent  24  (see  FIG. 1 ) consisting of zeolite. On a first of its two circular front sides, the cylindrical cartridge  60  is provided with a docking element  62  comprising a closeable inlet for receiving water vapor from the cooling member  32  when the latter is docked to the docking station as shown in  FIG. 4 . On the second of its two circular front sides, the cylindrical cartridge is sealed by a circular front plate  64  which is traversed by a grip  66  for facilitating insertion and removal of the cartridge  60  into and from the docking station  10  by turning the cartridge  60  around its axis of symmetry. When one zeolite cartridge is used, it is possible to freeze the cooling member approximately twenty times. The docking station  12  further comprises an electric power converter  74  having a plug  76  for plugging the power converter to a power socket. When plugged to a power socket, the power converter provides power for the docking station  10  itself, in particular for the pump  18  used for evacuating the cooling member, as well as for charging a battery of the epilator when the latter is docked to the docking station. To this end, the docking station is equipped with an electric contact for contacting a complementary contact of the epilator. The electric contact is preferably arranged at the bottom of the cavity situated below the opening  52  described with reference to  FIG. 3 . 
         [0042]      FIG. 6  is a flow chart of a method according to the invention. In a first step S 01 , an epilator is docked to a docking station. By pressing an “ice” button on the docking station (step S 02 ), a user actuates a vacuum pump within the docking station. The pump consequently starts evacuating a cooling member of the epilator (step S 03 ), while a pressure sensor measures the gas pressure inside the cooling member. In step S 04 , it is determined whether the measured pressure is below 5 mbar. If the pressure is found to be above 5 mbar, the method returns to step S 03  (the pump continues pumping); otherwise the pump is shut down. In step S 05 , a certain period of time, of the order of a few seconds to a few minutes, is left to elapse during which a sorbent situated inside the docking station adsorbs water vapor released from the cooling member of the epilator, thereby lowering the temperature of the water remaining in the cooling member. When the water in the cooling member has frozen, the docking station emits an acoustic or optical signal (step S 06 ), thereby informing the user that the cooling member has reached its operating temperature. The user then separates the epilator from the docking station (step S 07 ) and starts an epilation session (step S 08 ). In accordance with a preferred embodiment, the cooling member remains frozen for about twenty minutes. When the epilation session has been terminated, the user decides whether or not to re-dock the epilator to the station (step S 09 ). If the user decides to re-dock the epilator, the method returns to step S 01 ; otherwise the method is terminated. It is noted that the method may further comprise a step of replacing a cartridge containing sorbent. Alternatively, the method may further comprise a step of drying the sorbent, particularly by heating it, either by using a heater provided in the docking station or by placing it into an oven or a microwave heater. The method preferably further comprises a step of charging a battery of the epilator. 
         [0043]    While the invention has been illustrated and described in detail in the drawings and in the foregoing description, these drawings and description are to be considered as examples and are not restrictive. The invention is not limited to the disclosed embodiments. 
         [0044]    Use of the verb “comprise” and its conjugations does not exclude the presence of steps or elements other than those stated in the claims. Use of the indefinite article “a” or “an” preceding an element or step does not exclude the presence of a plurality of such elements or steps. It is also noted that a single unit may provide the functions of several means mentioned in the claims. The mere fact that certain features are recited in mutually different dependent claims does not indicate that a combination of these features cannot be used to advantage. Any reference signs in the claims shall not be construed as limiting their scope.