Abstract:
An apparatus and method for cooking at least one egg with an eggshell The apparatus comprises a housing provided with a device for providing microwave radiation in a confined space in the housing and a holder located in the confined space. The holder is provided with at least one cavity adapted to the shape of the egg with the eggshell. The apparatus further comprises means to insert a liquid into the holder for filling the cavity with the liquid to at least partly surround the eggshell of the egg located in the cavity. The apparatus comprises also means to control the amount of liquid in the holder during a cooking process of the at least one egg, wherein: —a first amount of liquid is inserted into the cavity before providing microwave radiation in the cavity, which first amount of liquid surrounds the eggshell of the egg located in the cavity; —a second amount of liquid is gradually inserted into the cavity.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates to apparatus for cooking at least one egg with an eggshell, which apparatus comprises a housing provided with a device for providing microwave radiation in a confined space in the housing and a holder located in the confined space, which holder being provided with at least one cavity adapted to the shape of the egg with the eggshell, which apparatus further comprises means to insert a liquid into the holder for filling the cavity with the liquid to at least partly surround the eggshell of the egg located in the cavity. 
         [0002]    The invention also relates to a method for cooking at least one egg with an eggshell in such an apparatus. 
       BACKGROUND OF THE INVENTION 
       [0003]    By such an apparatus, which is known from WO2012002814A1, liquid is inserted in the cavity to surround the eggshell of the egg, after which the device for providing microwave radiation is turned on, whereby the liquid as well as the egg is being heated. The liquid is in heat exchanging contact with the eggshell, whereby due to the layer of liquid around the eggshell a good cooking process of the egg by means of the microwave radiation is obtained. The egg can be cooked in less than two minutes. The apparatus of 
         [0004]    WO2012002814A1 is provided with an outlet being coupled to a drain for removal of the liquid from the holder after use. 
         [0005]    During the cooking process all liquid is maintained inside the cavity to maintain a desired layer of liquid around the egg. A disadvantage of the known apparatus is that a build up of the pressure inside the cavity will occur. Due to said pressure build up the holder needs to be relative strong to be able to withstand the relatively high pressure. Furthermore, at such a system with pressure build up, for example components such as seals and hoses are relatively heavy loaded, are relatively critical, and are relatively demanding and thus relatively expensive. The holder will need to be kept closed with a relatively large force. This limits the feasibility of manual or motorized actuated open-close mechanisms for the holder. 
       SUMMARY OF THE INVENTION 
       [0006]    It is an object of the apparatus according to the invention to maintain a desired layer of liquid around the egg, whilst reducing the pressure build up in the cavity. 
         [0007]    This object is achieved by the apparatus according to the invention in that the apparatus comprises means to control the amount of liquid in the holder during a cooking process of the at least one egg, wherein:
       a first amount of liquid is inserted into the cavity before providing microwave radiation in the cavity, which first amount of liquid at least partly surrounds the eggshell of the egg located in the cavity;   a second amount of liquid is gradually inserted into the cavity during providing microwave radiation to replenish the amount of liquid that has been evaporated and has left the cavity during providing microwave radiation in the cavity and to maintain a desired layer of liquid around the egg located in the cavity.       
 
         [0010]    By the apparatus according to the invention liquid is allowed to escape from the cavity when the pressure in the cavity rises, for example through a relief valve to limit the pressure build up or by having the cavity in open communication with the environment so that no pressure build up will occur. To maintain the desired layer of liquid around the egg, the second amount of liquid is gradually added, to replenish the amount of liquid that has been evaporated and has left the cavity during providing microwave radiation in the cavity. 
         [0011]    It has to be noted that US20089145491A1 discloses an apparatus for cooking at least one egg with an eggshell. However, this apparatus comprises a carrier plate with square openings with rounded corners that constitute holders for the vertical positioning of eggs. The carrier plate can be made from a wired structure in order to ensure adequate circulation of steam around the eggs. The square openings with rounded corners in the carrier plate do not form cavities which can be filled with a liquid to at least partly surround the eggshell of the egg located in the cavity so that a desired layer of liquid around the egg located in the cavity can be maintained. 
         [0012]    An embodiment of the apparatus according to the invention is characterized in that the second amount of liquid is gradually inserted into the cavity after a first predetermined period of time of providing microwave radiation and during a second predetermined period of time of providing microwave radiation. 
         [0013]    The first and second predetermined periods of time can be based on experiments or can theoretically be determined. Furthermore, adding liquid based on predetermined time periods can easily be controlled. 
         [0014]    Another embodiment of the apparatus according to the invention is characterized in that first predetermined period of time of providing microwave radiation is shorter for the cooking process of a soft-boiled egg than for a hard-boiled egg. 
         [0015]    By adding an additional amount of liquid relatively early in the process of cooking the egg, a soft-boiled egg will be obtained, whilst by adding the additional amount of liquid later in the process of cooking the egg, a hard-boiled egg will be obtained. In this manner a user can simply obtained the desired boiled egg by amending the first predetermined period of time. 
         [0016]    Another embodiment of the apparatus according to the invention is characterized in that the second amount of liquid is larger for the cooking process of a soft-boiled egg than for a hard-boiled egg. 
         [0017]    By adding a relatively large second amount of liquid, preferably during a longer second predetermined period of time of providing microwave radiation, a soft-boiled egg will be obtained, whilst by adding a smaller second amount of liquid, preferably during a smaller second predetermined period of time of providing microwave radiation, a hard-boiled egg will be obtained. In this manner a user can simply obtained the desired boiled egg by amending the second amount of liquid. 
         [0018]    Another embodiment of the apparatus according to the invention is characterized in that the second amount of liquid is added in pulses during the second predetermined period of time of providing microwave radiation. 
         [0019]    In this manner the amount and timing of the second amount of liquid into the cavity can easily be controlled. 
         [0020]    Another embodiment of the apparatus according to the invention is characterized in that a constant power of the microwave radiation is used during the cooking process of the at least one egg. 
         [0021]    By operating the device for proving microwave radiation at a constant power no irregular change in the microwave radiation will occur. 
         [0022]    Furthermore, such a device is relatively cheap and is readily available on the market, especially when a device operating at 2.45 GHz will be used. Relatively simple devices for proving microwave radiation have the disadvantage that amending the power of the microwave radiation in the cavity during operation means that the device will be switched on and off during several seconds. Furthermore, the on/off cycle is not very accurate and each time the device needs to start up again whereby an irregular change in the microwave radiation in the cavity will occur. Due to the irregular change in the microwave radiation the egg will not be cooked well and uniformly. 
         [0023]    Another embodiment of the apparatus according to the invention is characterized in that the sum of the first predetermined period of time of providing microwave radiation and the second predetermined period of time of providing microwave radiation is about the same for the cooking process of a soft-boiled egg and a hard-boiled egg. 
         [0024]    In this manner it is predictable and known in advance how long the cooking process of the egg will take. By simply shifting to a shorter first predetermined period of time and a longer second predetermined period of time a soft-boiled egg will be obtained, whilst by shifting to a longer first predetermined period of time and a shorter second predetermined period of time a hard-boiled egg will be obtained. 
         [0025]    Another embodiment of the apparatus according to the invention is characterized in that the first amount of liquid is between 30 and 60 millilitre, whilst the second amount of liquid is between 60 and 120 millilitre. 
         [0026]    In this manner the amount of liquid inside the cavity is relatively small, which relatively small amount of liquid can easily be heated up by the microwave radiation, whilst the amount can also easily be replenished. 
         [0027]    Another embodiment of the apparatus according to the invention is characterized in that at a power of 1000 Watt and 2.45 GHz of the device for providing microwave radiation, the first predetermined period of time is between 15 and 40 seconds, with a total period of time of providing microwave radiation between 90 and 120 seconds. 
         [0028]    With such power and frequency an egg can be well boiled in less than 2 minutes. 
         [0029]    Another embodiment of the apparatus according to the invention is characterized in that the liquid is an aqueous liquid with a dielectric constant with an imaginary part, ε″, between 20-500 at a temperature between 0° C.-100° C. at a microwave frequency of 2.45 GHz, preferably water with NaCl, more preferably 0.2M NaCl. 
         [0030]    With such an aqueous liquid it is found out that a good cooking process of an egg is obtained whereby both the egg yoke as well as the egg white get the desired properties. The advantages of the aqueous liquid with the described dielectric constant are described in WO2012002814A1. This document is incorporated by reference in this application. 
         [0031]    For example salt preferably NaCl can be added to the liquid, for example water, to obtain the desired aqueous liquid. The apparatus can use tab water to which salt preferably NaCl can be added to obtain the desired aqueous liquid. Water is easily available in every household or restaurant and also salt like NaCl can easily be obtained. Furthermore, a combination of water with such an amount of NaCl is not toxic for humans. 
         [0032]    Other kinds of liquid and components are also possible. Another embodiment of the apparatus according to the invention is characterized in that the apparatus comprises a conduit guiding liquid into the cavity, which conduit is at least partly located in the confined space, wherein the second amount of liquid is preheated in the conduit by the microwave radiation before the liquid is inserted into the holder. 
         [0033]    By preheating the second amount of liquid it can be realised that the temperature of the liquid in the cavity will not or nearly not drop during the insertion of the second amount of liquid in the cavity. By preheating the second amount of liquid by the microwave radiation no additional means for preheating the second amount of liquid to the desired temperature for entering the cavity is needed. 
         [0034]    Another embodiment of the apparatus according to the invention is characterized in that the part of the conduit located in the confined space is between 40 and 80 centimetres long. 
         [0035]    Such a length is long enough to heat up the liquid in the conduit from for example 20° C. when entering said part to about the same temperature as the liquid already present in the cavity, when leaving said part. 
         [0036]    Another embodiment of the apparatus according to the invention is characterized in that the liquid has an average layer thickness between the holder and the eggshell of the egg between 2 and 8 millimetres. 
         [0037]    With such an average layer thickness the amount of liquid needed for cooking the egg is limited while the layer is thick enough to provide a good cooking process of the egg. As the egg is preferably supported in the cavity by spacers inside the holder and is preferably being pressed against said spacers by a spring, there will be some direct contact between the egg and the holder. However, such contact is limited and nearly the whole eggshell is surrounded by the liquid at the beginning of the cooking process. 
         [0038]    Another embodiment of the apparatus according to the invention is characterized in that the means to insert a liquid into the holder comprises at least two pumps, wherein a first pump is connected by a first conduit to the liquid inlet, whilst a second pump is connected by a second conduit to the liquid outlet. 
         [0039]    By having two pumps, one for pumping liquid into the cavity through the liquid inlet and one for pumping the liquid out of the cavity through the liquid outlet, no valves are needed between the pumps and the cavity since by switching the pumps on or off, transport of liquid through each pump is being controlled. 
         [0040]    Another embodiment of the apparatus according to the invention is characterized in that the second holder part comprises an open outlet for at least a gaseous phase of the liquid formed in the cavity during the cooking process. 
         [0041]    When heating the egg and the liquid surrounding the eggshell of the egg, the liquid will be turned into a gaseous phase which gas or steam can escape through the open outlet to prevent a pressure build up in the cavity. Since no large pressure build up occurs in the cavity, the forces on the first and second holder part are relatively low so that a relatively light apparatus can be built. 
         [0042]    The invention also relates to a method for cooking at least one egg with an eggshell by means of an apparatus as described above. 
     
    
     
       A BRIEF DESCRIPTION OF THE DRAWINGS 
         [0043]      FIGS. 1 a  and 1 b    show a perspective front view and rear view of a first embodiment of an apparatus according to the invention in an open position of the housing parts. 
           [0044]      FIG. 1 c    shows a cross section of a part of the apparatus as shown in  FIGS. 1 a   - 1   b.    
           [0045]      FIGS. 2-4  show perspective views of parts of the apparatus as shown in  FIGS. 1 a   - 1   c.    
           [0046]      FIG. 5  shows a top view of the part as shown in  FIG. 4 . 
           [0047]      FIGS. 6 a  and 6 b    show a perspective front view and rear view of the apparatus as shown in  FIG. 1 a -1 b    in a closed position of the housing parts. 
           [0048]      FIG. 6 c    shows a cross section of the apparatus as shown in  FIGS. 6 a   - 6   b.    
           [0049]      FIG. 7  shows a perspective view of a part of the apparatus as shown in  FIGS. 6 a   - 6   c.    
           [0050]      FIGS. 8 a  and 8 b    show a front and rear perspective view of a second embodiment of the apparatus according to the invention in an open position of the housing parts. 
           [0051]      FIG. 9  shows a perspective front view and rear view of the apparatus as shown in  FIG. 8 a -8 b    in a closed position of the housing parts. 
           [0052]      FIGS. 10 a  and 10 b    show a front and rear perspective view of a third embodiment of the apparatus according to the invention in an open position of the housing parts. 
           [0053]      FIG. 11  shows a perspective front view and rear view of the apparatus as shown in figure boa and lob in a closed position of the housing parts. 
           [0054]      FIGS. 12 a  and 12 b    show a front and rear perspective view of a fourth embodiment of the apparatus according to the invention in an open position of the housing part. 
           [0055]      FIG. 13  shows a perspective front view and rear view of the apparatus as shown in  FIGS. 12 a  and 12 b    in a closed position of the housing parts. 
           [0056]      FIG. 14  shows a working scheme of the apparatus as shown in the  FIGS. 6 a   - 6   b,    9 ,  11 ,  13  during the filling of the cavity and the cooking of the egg. 
           [0057]      FIG. 15  shows a diagram disclosing the microwave radiation time versus the amount of liquid added to the cavity. 
           [0058]      FIG. 16  shows a working scheme of the apparatuses as shown in the  FIGS. 6 a   - 6   b,    9 ,  11 ,  13  during empting of the cavity after cooking of the egg. 
       
    
    
       [0059]    In the drawings like reference numerals refer to like elements. 
       DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0060]      FIG. 1 a   - 7  show different views of a first embodiment of an apparatus  1  according to the invention and specific parts thereof. From the apparatus  1  only relevant components are shown and other components like covers and mounting constructions for mounting elements in the apparatus are left out for reason of clarity. 
         [0061]    The apparatus  1  comprises a base  2  on which two containers  3  and  4  are located. Above the containers  3  and  4  a container  5  is located which container is provided with a dosing unit  6 . The dosing unit  6  is located above an opening  7  of the container  3 . The apparatus  1  further comprises a first housing part  8  with a first holder part  9  as well as a second housing part  10  with a second holder part  11 . The second housing part  10  is connected in the apparatus  1  to the base  2  and has a fixed relation thereto. The first housing part  8  is movable with respect to the second housing part  10  between a first open position as shown in  FIGS. 1 a -1 c    and a second closed position as shown in  FIGS. 6 a   - 6   c.  The first housing part  8  is movable with respect to the second housing part  10  by means of manually operated gearing mechanisms  12  located on each side of the first and second housing part  8 ,  10 . Each gearing mechanism  12  comprises a curved rod  13  which is provided with teeth  14  on a side directed to the base  2  and the containers  3 ,  4 . The curved rods  13  are connected on two opposite sides of the first housing part  8 . Each gearing mechanism  12  further comprises a first gear wheel  16  being pivotably about a pivot axis  17  and a second gear wheel  18  having a smaller diameter than the gear wheel  16 , which second gear wheel  18  being connected to the gear wheel  16  and being rotatable simultaneously therewith about the pivot axis  17 . The pivot axis  17  has a fixed position in the apparatus  1 . The first gear wheel  16  cooperates with the teeth  14  of the rod  13 . The second gear wheel  18  cooperates with teeth  19  on a disc  20 , which disc  20  is pivotable about a pivot axis  21 . The pivot axis  21  has a fixed position in the apparatus  1 . The disc  20  is connected on a side remote of the teeth  19  to a U-shaped handle  22 . The handle  22  comprises two legs  23  located on both sides of the second housing part  10  and connected to the discs  20 , which legs  23  are interconnected on sides remote of the discs  20  by means of a bridge shaped part  24 . By pivoting the handle  22  about the pivot axis  21  in a direction as indicated by arrow P1 the teeth  19  on the disc  20  will cooperate with the second gear  18  and will rotate the gear  18  in a clockwise direction as indicated by arrow P2. Since the second gear  18  is connected to the first gear  16 , the first gear  16  will also be rotated in clockwise direction. As the teeth of the gear  16  cooperate with the teeth  14  on the rod  13 , the rotation of the gear  16  will cause the rod  13  to move along the gear  16 , whereby due to the curved shape of the rods  13  the first housing part  8  will firstly be moved in a mainly horizontal direction towards the containers  3 ,  4 , after which the first housing part  8  will be moved simultaneously towards the containers  3 ,  4  as well as to the second housing part  10 , whereby in the final stage of movement of the first housing part  8 , the first housing part  8  will be moved vertically towards the second housing part  10  to the second closed position as shown in  FIGS. 6 a   - 6   c.  During the whole movement both housing parts  8 ,  10  remain horizontal. Especially the horizontal open position of the first housing part  8  being moved forwardly away form the containers  3 ,  4 , facilitates the placement and removal of the to eggs and easily prevents the egg from falling out of the first housing part. 
         [0062]    As can be seen in  FIGS. 1   c,    3 - 5 ,  6   c  and  7  the first housing part  8  comprises a square bottom wall  30  and four side walls  31  extending perpendicularly to the bottom wall  30 . On the bottom wall  30  a spirally conduit  32  is located which opens near the middle of the bottom wall  30  in a vertically extending tube  33 . The end  34  of the conduit  32  is in connection with the container  3 ,  4  as will be explained with reference to the  FIGS. 14 and 16 . The first housing part  8  is further provided with the first holder part  9 , which holder part  9  has a shape of half an egg and is provided with spacers  35  extending from the wall  36  of the first holder part  9 . The first holder part  9  is provided at its lowest part with a tube  37 , which fits into the tube  33  in the first housing part  8 . The tube  37  is provided with a sealing ring  38  on the outside thereof to provide a watertight sealing between the tubes  33  and  37 . The tube  37  is provided on a side near the wall  36  with a grid comprising a number of openings  39 . In case that a egg  40  located in the first holder part  9  will break, the grid will prevent parts of the egg shell and the egg to enter the tubes  37 ,  33  and the conduit  32 . As can be seen in  FIG. 1 c    the spacers  35  keep the eggshell of the egg  40  at a predetermined distance from the wall  36  of the first holder part  9 . The wall  36  of the first holder part  9  is provided with a conical part  41  at a side directed towards the second housing part  10 . 
         [0063]    The second housing part  10  is provided with a square top wall  45  and four side walls  46  extending downwardly therefrom. Inside the walls  45 ,  46  a device  47  for providing microwave radiation is located. Such an device is well known in the art and will not further be explained. Below the device  47  a square chamber  48  is located in which the second holder part  11  is mounted. The second holder part  11  is provided with an inner wall  49  having a shape of half an egg. The wall  49  of the second holder part  11  together with the wall  36  of the first holder part  9  define a cavity  50  having an egg shaped form wherein a first longitudinal end being relatively narrow is located near the bottom of the first holder part  9  whilst a second longitudinal end being relatively wide is located near a top of the wall  49 . Near the top of the wall  49  a spring  51  is provided, which spring  51  rests against the second end of the egg  40  when the housing parts  8 ,  10  are in their first closed position (see  FIGS. 6, 7 ), thereby pressing the egg  40  on the spacers  35  to maintain a fixed position of the egg  40  in the cavity  50 . 
         [0064]    The second holder part  11  is provided with a conical part  52 , which cooperates with the conical part  41  of the first holder part  9  to facilitate the correct positioning of the first housing part  8  with respect to the second housing part  10 . The second holder part  11  is further provided with a ring shaped seal  53  which rests against the first holder part  9  in the closed position, as shown in  FIG. 6 c    and provides a water tight seal between the first holder part  9  and the second holder part ii. The second holder part  11  is connected near the top thereof to a conduit  54 , which conduit  54  is in fluid communication with the container  4 , as will be further explained with reference to the  FIGS. 14 and 16 . In the closed position as show in the  FIGS. 6 a   - 6   c,  microwave radiation can be generated by the device  47  in the confined space  154 , which space  154  is bounded by the chamber  48  of the second housing part  10  and the walls  30 ,  31  of the first housing part  8 . The first holder part  9  and the second holder part  11  are made from materials being transparent to microwave radiation so that microwave radiation will also reach the cavity  50  in which an egg  40  is being positioned. Such materials are well known in the art, for example as described in the above mentioned initial patent application WO2012002814A1. Before explaining the operation of the apparatus  1 , other embodiments of apparatuses according to the invention will be described since the working principles of these apparatuses are mainly the same. 
         [0065]      FIG. 8 a   - 9  disclose a second embodiment of an apparatus  101  according to the invention which apparatus  101  differs from the apparatus  1  lo in that the gear  18  is driven by an electric motor  102  instead of by pivoting the handle  24  manually. 
         [0066]    The  FIGS. 10 a   - 11  disclose a third embodiment of an apparatus  201  according to the invention which differs from the apparatus  1 ,  101  in that the first housing part  8  is only pivotable with respect to the second housing part  10 . The first housing part  8  is provided at a side near the containers  3 ,  4  with two L-shaped brackets  202 , which L-shaped brackets  202  are pivotable with respect to the base  2  about pivot axis  203 . The pivot axis  203  has a fixed position in the apparatus  201 . At a side remote of the containers  3 ,  4  the first housing part  8  is provided with a handle  204 . By means by the handle  204  a user can manually move the first housing part  8  from the open position as shown in  FIGS. 10 a -10 b    to the closed position as shown in  FIG. 11  and vice versa. In the handle  204  a locking mechanism is provided to lock the handle  204  to the second housing part  10  in the closed position of the housing parts  8 ,  10 . Well known locking mechanisms can be used for such a lock. The base  2  of the apparatus  201  is provided with a slanted surface  205  on which the first housing part  8  rests in the open position thereof. 
         [0067]    To provide a smooth movement of the first housing part  8  from the closed position to the open position and to prevent that the first housing part  8  simply drops on the slanted surface  205 , the apparatus  201  is provided with a damping mechanism  206 . 
         [0068]    The damping mechanism  206  comprises on each L-shaped bracket  202  a disc  207  being provided with teeth  208 . The teeth  208  cooperate with a gear wheel  209 , which is rotatable about an axis which has an fixed position in the apparatus  201 . The gearwheel  209  is prevented against relatively fast rotation so that only by moving the teeth  208  relatively slowly in or opposite a direction as indicated by arrow P3 the first housing part  8  can be moved with respect to the second housing part  10 . 
         [0069]      FIGS. 12 a   - 13  disclose a fourth embodiment of an apparatus  301  according to the invention which differs from the apparatus  201  in that the gear wheel  209  is now electrically driven by a motor  302  which motor has a fixed position in the apparatus  301 . By operating the electric motor  302 , the gear wheel  209  is being driven. Since the gearwheel  209  cooperates with the teeth  208  on the disc  207 , the disc  207  as well as the L-shaped bracket  202  and the first housing part  8  will be moved in a direction as indicated by arrow P3 to move the first housing part  8  from the open position as shown in  FIG. 12 a -12 b    to the closed position as shown in  FIG. 13 . By rotating the gearwheel  209  in the opposite direction the first housing part  8  will be moved in a direction opposite to arrow P3 from the closed position to the open position. 
         [0070]      FIGS. 14 and 16  show a more schematic view of the apparatus  1 ,  101 ,  201 ,  301 . 
         [0071]    As can be seen the first container  3  is connected via a conduit  401  to a first peristaltic pump  402 . An outlet of the peristaltic pump  402  is connected via a conduit  403  to the end  34  of the spirally conduit  32  in the first housing part  8 . The apparatus  1 ,  101 ,  201 ,  301  is further provided with a second peristaltic pump  404 , which is connected by means of a conduit  405  to the end  34  of the spirally conduit  32  and is connected on another side of the pump  404  by means of a conduit  406  to the container  4 . The conduit  54 , which is connected to the cavity  50  in the second holder part  11  opens at an end remote of the cavity  50  into the container  4 . Both the containers  3 ,  4  are open at the top so that in the containers  3 ,  4  the atmospheric pressure exists. 
         [0072]    The first container  3  is provided at its lower part with a buffer unit  407 . The buffer unit  407  is connected by means of a conduit  408  to a heat exchanger, for example a Peltier heat exchanger  409  to preheat the liquid before it enters first housing part  8 . In the buffer  407  a temperature sensor may be present to check whether the liquid has the desired temperature. lo The peristaltic pumps  402 ,  404 , the device  47  for providing microwave radiation in the space  154 , the Peltier heat exchanger, the dose unit  6  as well as sensors to check for example the liquid level in the containers  3 ,  4  are all controlled by means of a computer  410 . 
         [0073]      FIG. 14  discloses a scheme of the filling of the cavity  50  as well as the process during the cooking process of the egg  40 . 
         [0074]    The operations of the apparatus  1 ,  101 ,  201 ,  301  are as follows. 
         [0075]    After placing an egg  40  in the cavity  50  and closing the first housing part  8  and the second housing part  10  the liquid in the buffer unit  407  will be heated to a predetermined temperature of for example 20 degrees Celsius. 
         [0076]    After the liquid has reached the desired temperature the liquid will be pumped by means of the first pump  402  through the conduit  401  and the conduit  403  in the direction as shown by the arrow P4 into the spirally conduit  32  and into the cavity  50 . The egg  40  will be nearly completely surrounded by the liquid except for the locations where the egg is in contact with the spacers  35  and the spring  51 . It is also possible that a small part of the egg  40  near the spring  51  is not completely covered with the liquid. The liquid can be water with an addition of NaCl, for example preferably 0.2M NaCl (about 12 gram/litre water), to obtain a liquid with a dielectric constant with an imaginary part, ε″, between 20-500 at a temperature between 0° C.-100° C. and at a microwave frequency of 2.45 GHz. 
         [0077]    With an egg of about 60-65 grams and a length of about 56-60 millimetres an amount of about 45 millilitre of liquid will be sufficient to fill the space between the eggshell of the egg  40  and the walls  36 ,  49  of the first holder part  9  and the second holder part  11 , whereby a layer of liquid around the eggshell is obtained having an average thickness of 2-8 millimetres. 
         [0078]    After the cavity  50  is initially filled with the desired amount the to device  47  operating at a common 2.45 GHz is switched on at a constant power of for example 1000 Watt, whereby microwave radiation is generated in the space  154  to heat the liquid as well as the egg  40  in the cavity  50 . As soon the liquid starts to boil, the generated steam can escape through the conduit  54  and will flow in the direction indicated by arrow P5 into the container  4 . To prevent that due to the evaporation of the liquid the egg  40  will no longer be surrounded with liquid, additional liquid is added to the cavity  50 . This liquid enters the first housing part  8  at a temperature of about 20 degrees in small pulses by activating the first pump  402  during a predetermined time. Since the conduit  32  is located inside the cavity  54 , also the liquid present in the conduit  32  will be heated by the microwave radiation. The conduit  32  might have a length of for example 40-80 centimetres being long enough to heat up the liquid in the conduit  32  at the end  34  from 20° C. so that the liquid when entering the cavity  50  will have about the same temperature as the liquid already present in the cavity  50 . Other lengths are also possible. 
         [0079]    As can be seen in  FIG. 15  a first amount V1 of liquid is added before the microwave radiation starts. After a period of time T11 of for example 25 seconds a small amount V2 of for example 5 millilitres is added to the cavity  50  which amount V2 is then added every 3.5 seconds. In the diagram, the pulses are shown by a line  501 . In the diagram also the average amount of liquid added to the cavity  50  is indicated by means of a line  502 . During the cooking process by means of the microwave radiation, the power of the device  47  is kept constant at 100 Watt. By operating the device at a constant power no irregular change in the microwave radiation will occur. After 95 seconds the microwave radiation will be stopped as can be seen in the diagram. As shown in  FIG. 15  almost 100 millilitres have been added to the cavity  50  after the initial first amount of 45 millilitres. By adding such a relatively large second amount of liquid starting after such a relatively short time T11, a soft-boiled egg will be obtained. 
         [0080]    By starting the insertion of additional liquid in the cavity  50  after a longer period of time T12, for example after 32 seconds of the start of the microwave radiation and by adding the same amount V2 in the same intervals of 3.5 seconds a middle-boiled egg will be obtained. The lines  503 ,  504  show respectively the pulses and the average amount of added liquid. The total second amount of liquid added to the cavity  50  for a middle-boiled egg is less than for a soft-boiled egg. 
         [0081]    If the insertion of additional liquid starts even later, for example after a longer period of time T13, for example after 39 seconds with the same amount V2 and the same interval, a hard-boiled egg will be obtained. The lines  505 ,  506  show respectively the pulses and the average amount of added liquid. The total second amount of liquid added to the cavity  50  for a hard-boiled egg is less than for a soft-boiled egg and a middle-boiled egg. 
         [0082]    After the microwave radiation has been switched off, the second pump  404  is switched on to pump  405  the liquid in the cavity  50  in a direction as indicated by arrow P6 through the conduit  32  into the conduit  404 , through the pump  405  into the conduit  406  into the container  4  for waste liquid. The conduit  32  as well as the tubes  33 ,  37  are used both as inlet for the liquid into the cavity  50  as well as an outlet of the liquid from the cavity  50 . 
         [0083]    It is also possible to use microwave radiation whereby the power thereof is changed, for example lowered during the cooking process. In such a case the amount of liquid added during the microwave radiation will be different from the amount as shown in  FIG. 15 . It is also possible that instead of adding the liquid in pulses with an amount of V2 to add the liquid in smaller or larger amounts with a interval being larger or smaller than described above. 
         [0084]    It is also possible to add the liquid at a constant rate or to vary the amount of added liquid in time. Also, smaller step sizes can be chosen, such that the flow is accurately controlled by means of pulse width modulation, resulting in the same egg preparation program with the same amounts of pumped liquids. 
         [0085]    It is also possible to have different holders for different sizes of eggs. It is also possible to have other amounts of NaCl in the water, for example between 10 and 14 gram/litre water. 
         [0086]    It is also possible to preheat the liquid to another temperature, for example about 30-35 degrees Celsius before entering the housing. 
         [0087]    It is also possible to start the addition of the second amount of liquid based on for example the temperature in the cavity or the amount of liquid that has been evaporated and has left the cavity. 
         [0088]    The person skilled in the art will realize that the present invention is by no means limited to the preferred embodiments. Other 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. 
         [0089]    In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the scope should not be construed as limiting the scope of the claims. 
       LIST OF REFERENCE SIGNS 
       [0090]      1  apparatus 
         [0091]      2  base 
         [0092]      3  container 
         [0093]      4  container 
         [0094]      5  container 
         [0095]      6  dosing unit 
         [0096]      7  opening 
         [0097]      8  first housing part 
         [0098]      9  first holder part 
         [0099]      10  second housing part 
         [0100]      11  second holder part 
         [0101]      12  gearing mechanism 
         [0102]      13  rod 
         [0103]      14  teeth 
         [0104]      16  gear wheel 
         [0105]      17  pivot axis 
         [0106]      18  gear wheel 
         [0107]      19  teeth 
         [0108]      20  disc 
         [0109]      21  pivot axis 
         [0110]      22  handle 
         [0111]      23  leg 
         [0112]      24  bridge shaped part 
         [0113]      30  bottom wall 
         [0114]      31  side wall 
         [0115]      32  conduit 
         [0116]      33  tube 
         [0117]      34  end 
         [0118]      35  spacer 
         [0119]      36  wall 
         [0120]      37  tube 
         [0121]      38  sealing ring 
         [0122]      39  opening 
         [0123]      40  egg 
         [0124]      41  conical part 
         [0125]      45  top wall 
         [0126]      46  side wall 
         [0127]      47  device 
         [0128]      48  chamber 
         [0129]      49  wall 
         [0130]      50  cavity 
         [0131]      51  spring 
         [0132]      52  conical part 
         [0133]      53  seal 
         [0134]      54  conduit 
         [0135]      101  apparatus 
         [0136]      154  space 
         [0137]      201  apparatus 
         [0138]      202  bracket 
         [0139]      203  pivot axis 
         [0140]      204  handle 
         [0141]      205  surface 
         [0142]      206  damping mechanism 
         [0143]      207  disc 
         [0144]      208  teeth 
         [0145]      209  gear wheel 
         [0146]      301  apparatus 
         [0147]      302  motor 
         [0148]      401  conduit 
         [0149]      402  peristaltic pump 
         [0150]      403  conduit 
         [0151]      404  peristaltic pump 
         [0152]      405  conduit 
         [0153]      406  conduit 
         [0154]      407  buffer 
         [0155]      409  heat exchanger 
         [0156]      410  computer 
         [0157]      501  line 
         [0158]      502  line 
         [0159]      503  line 
         [0160]      504  line 
         [0161]      505  line 
         [0162]      506  line 
         [0163]    P3 arrow 
         [0164]    P4 arrow 
         [0165]    P6 arrow 
         [0166]    V1 amount of liquid 
         [0167]    V2 amount of liquid 
         [0168]    T11 period of time 
         [0169]    T12 period of time 
         [0170]    T13 period of time