Patent Publication Number: US-2007114222-A1

Title: Steam cooking apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
      This application claims the benefit of Korean Patent Applications Nos. 2005-0113166 and 2005-0113169, filed on Nov. 24, 2005 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.  
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a steam cooking apparatus, and, more particularly, to a steam cooking apparatus having a steam generating unit using a plate-shaped heater.  
      2. Description of the Related Art  
      Generally, examples of conventional food cooking methods include a method for cooking food contained in a gas oven or electric oven by directly applying heat to the food, a method for heating a steam container containing food to cook the food indirectly, and a method for cooking food using high-frequency waves from a microwave oven.  
      When cooking food by directly heating the food using a gas oven or electric oven, there is a problem of food oxidization because the food comes into contact with oxygen contained in the air and this results in deterioration in the taste of the food. When cooking food using a steam container, the food contains an excessive amount of moisture and suffers from a reduction in peculiar flavor thereof. Also, when cooking food using a microwave oven, there is a problem in that high-frequency waves may fail to evenly irradiate the food, resulting in localized over or under cooking of the food.  
      To solve the above described problems of conventional cooking methods, a cooking apparatus for cooking food by supplying superheated steam to the food was developed, and many technologies have been published in relation with the cooking apparatus using superheated steam. It has been found that, when cooking food using the cooking apparatus using superheated steam, high-temperature superheated steam is directly delivered to an overall surface of the food and this has the effects of preventing over or under cooking of the food and keeping an appropriate amount of moisture in the overall food suitable to guarantee good taste of food. An example of a cooking apparatus using superheated steam is disclosed in Japanese Patent Laid-Open Publication No. 2005-0061816.  
      A steam cooking apparatus disclosed in the above mentioned Japanese Patent Laid-Open Publication No. 2005-0061816 includes a water tank, a steam generating unit, a steam heater, and a blowing device, and is adapted to supply superheated steam into a cooking compartment, so as to cook food by heat contained in the superheated steam. The disclosed steam generating unit includes an annular sheath heater, which is configured to surround an outer surface of a pot, so as to generate steam by heating water stored in the pot. Specifically, the sheath heater is formed by inserting an electric heating coil into a metal protective tube and filling magnesium oxide powder as insulating powder in the metal protective tube. The sheath heater has advantages in that it can be easily processed to have a variety of shapes and has high heat efficiency.  
      However, the steam generating unit having the above described sheath heater has a need for storing a predetermined amount of water in the pot. In the case of the sheath heater disclosed in the above mentioned Japanese Patent Laid-Open Publication, it is configured to surround the pot, and thus, requires a predetermined time to generate steam by heating the water stored in the pot. Accordingly, the disclosed sheath heater has difficulty to rapidly generating steam.  
      Furthermore, since the sheath heater has a single output capacity, the generation speed and generation amount of steam cannot be regulated separately.  
      Other examples of the cooking apparatus using superheated steam are disclosed in Japanese Patent Laid-Open Publications Nos. 2004-0205130 and 2004-0162936. In the disclosed conventional cooking apparatuses using superheated steam, if water stored in a steam generating container of a steam generating device is exhausted, new water has to be supplied from a water tank into the steam generating container. Therefore, to inform a user of a need to add water, the conventional cooking apparatuses must have a water level sensing device for sensing the level of water received in the steam generating container. A representative example of the water level sensing device is a water level sensor for sensing a position of a float, which is disposed in the steam generating container and adapted to move up and down based on a variation in the level of water.  
      However, in the above described superheated steam cooking apparatuses, while the water received in the steam generating container is heated and boiled by a heater, the water level exhibits excessive fluctuation, causing the level of the float to fluctuate. Since the fluctuation of the level of the float, consequently, causes the water level sensor to generate a false sensing signal, it is impossible to accurately sense the level of water received in the steam generating container.  
     SUMMARY OF THE INVENTION  
      The present invention has been made in order to solve the above problems. It is an aspect of the invention to provide a steam cooking apparatus having a steam generating unit, which can generate steam rapidly and regulate the generation speed and generation amount of steam.  
      It is a further aspect of the invention to provide a steam cooking apparatus having a configuration to accurately sense the amount of water stored in a steam generating unit.  
      Consistent with one aspect, an exemplary embodiment of the present invention provides a steam cooking apparatus including a cooking compartment and a steam generating unit disposed at the outside of the cooking compartment and adapted to generate steam to be supplied into the cooking compartment, where the steam generating unit includes: a steam generating container to receive water therein, the steam generating container having a partitioned steam generating space; and a plate-shaped heater to heat the water received in the steam generating container.  
      The plate-shaped heater may include a plurality of heating elements.  
      The plurality of heating elements may have different outputs from one another.  
      The plurality of heating elements may be operated independently.  
      The plate-shaped heater may further include a single common power output terminal and a plurality of power input terminals.  
      The steam generating unit may further include a water level sensing device to sense the level of water received in the steam generating container.  
      The steam generating container may have a water level sensing chamber provided with the water level sensing device, and a steam generating chamber provided with the plate-shaped heater, and the steam generating container may include an intercepting member to divide the water level sensing chamber from the steam generating chamber.  
      The intercepting member may have an end spaced apart from the steam generating container, to guarantee intercommunication of water between the water level sensing chamber and the steam generating chamber.  
      The water level sensing device may include: a float disposed in the steam generating container and adapted to move up and down depending on a variation in the level of water; and a water level sensor to sense a position of the float to thereby sense the level of water.  
      The intercepting member may be formed with communication holes serving as passages of air, to keep the water level sensing chamber and the steam generating chamber at the same pressure as each other.  
      The water level sensor may include a stopper to prevent the float from being separated from the water level sensor.  
      Additional aspects and/or advantages of the invention will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the invention.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      These and/or other aspects and advantages of the exemplary embodiments of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings, of which:  
       FIG. 1  is a perspective view showing the configuration of a steam cooking apparatus consistent with an exemplary embodiment of the present invention;  
       FIG. 2  is a front view showing the outer appearance of the steam cooking apparatus of  FIG. 1 ;  
       FIG. 3  is a sectional view of the steam cooking apparatus of  FIG. 1 ;  
       FIG. 4  is an exploded perspective view showing the configuration of a steam generating unit included in the steam cooking apparatus of  FIG. 1 ;  
       FIG. 5  is a perspective view showing the configuration of a steam cooking apparatus consistent with another exemplary embodiment of the present invention;  
       FIG. 6  is an exploded perspective view showing the configuration of a steam generating unit shown in  FIG. 5 ; and  
       FIG. 7  is a sectional view taken along the line A-A′ of  FIG. 5 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      Reference will now be made in detail to exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. The embodiments are described below to explain the present invention by referring to the figures.  
       FIG. 1  is a perspective view showing the configuration of a steam cooking apparatus consistent with an exemplary embodiment of the present invention.  FIG. 2  is a front view showing the outer appearance of the steam cooking apparatus of  FIG. 1 .  FIG. 3  is a sectional view of the steam cooking apparatus of  FIG. 1 .  FIG. 4  is an exploded perspective view showing the configuration of a steam generating unit included in the steam cooking apparatus of  FIG. 1 .  
      The steam cooking apparatus consistent with the exemplary embodiment of the present invention, as shown in  FIGS. 1 and 2 , includes a housing  1  forming the outer appearance of the apparatus, a cooking compartment  10  defined in the housing  1  to have a predetermined space within the housing  1 , a door  2  to open and close an open front surface of the cooking compartment  10 , and a control panel  3  installed on the cooking compartment  10 . The steam cooking apparatus of the present invention further includes a water supply unit  20 , a steam generating unit  30 , and a pair of superheated steam supply units  40 , which are disposed in the space between the housing  1  and the cooking compartment  10  to supply steam into the cooking compartment  10 .  
      The cooking compartment  10  is constructed by a top plate  11 , bottom plate  12 , opposite lateral plates  13 , and a rear plate  14 , and has an inner space having a predetermined volume required to cook food. An insulating member (not shown) encloses the cooking compartment  10  to prevent leakage of heat from the cooking compartment  10  (See  FIG. 2 ). Also, a magnetron  4  for generating microwaves and a cross-flow fan  5  for cooling the magnetron  4 , steam generating unit  30 , other electric elements, etc. are provided at an outer surface of the top plate  11  of the cooking compartment  10 .  
      A plurality of small-diameter inlet holes  15  are arranged at the center of the respective lateral plates  13 , and a plurality of small-diameter outlet holes  16  are arranged around the inlet holes  15 , more particularly, along the periphery of the respective lateral plates  13 . The plurality of outlet holes  16  may be symmetrically arranged at front and rear sides and upper and lower sides of the plurality of inlet holes  15 . With the configuration of the lateral plates  13  of the cooking compartment  10 , steam inside the cooking compartment  10  is introduced into the superheated steam supply units  40  through the inlet holes  15 , and again returned into the cooking compartment  10  through the outlet holes  16  after being superheated to a high temperature.  
      The water supply unit  20  is mounted on an outer surface of the top plate  11  at a front location of the top plate  11 . The water supply unit  20  includes a water supply case  21 , a water supply container  22  slidable in the water supply case  21  to be inserted into or taken out of the water supply case  21 , a water supply pipe  23  to connect the water supply container  22  to the steam generating unit  30 , and a pump  24  provided on the water supply pipe  23  to supply water into the steam generating unit  30 .  
      In the water supply unit  20  having the above described configuration, if water is filled in the water supply container  22 , the water is pumped by the pump  24 , to be supplied into the steam generating unit  30  through the water supply pipe  23 .  
      The steam generating unit  30 , as shown in  FIGS. 1 and 4 , has an approximately box shape, and is mounted on the outer surface of the top plate  11  at a lateral portion of the top plate  11 . The steam generating unit  30  includes a steam generating container  31  that is connected to the water supply pipe  23  and adapted to receive the water introduced thereinto through the water supply pipe  23 , and a plate-shaped heater  50  that forms a bottom wall of the steam generating container  31  and is adapted to heat the water received in the steam generating container  31 , so as to generate steam.  
      The steam generating container  31  is perforated in a top wall thereof with a water supply hole  32  for the connection of the water supply pipe  23 , and in an upper portion of a front wall thereof with a steam outlet opening  33  for supplying steam generated in the steam generating container  31  to the cooking compartment  10 . A steam supply duct  34  is connected to the steam outlet opening  33  to communicate with a steam inlet opening  17  of the cooking compartment  10 . With this configuration, if steam is generated in the steam generating container  31 , the steam is supplied into the cooking compartment  10  through the steam supply duct  34 . The steam generating container  31  is further perforated, in a lower portion of a lateral wall thereof, with a drain hole  35  so that a drain pipe  36  is connected to the drain hole  35 , to drain water remaining in the steam generating container  31  after a cooking operation of the steam cooking apparatus is completed.  
      The superheated steam supply units  40 , as shown in  FIG. 3 , are provided at outer surfaces of both the lateral plates  13  of the cooking compartment  10 , respectively. Each of the superheated steam supply units  40  includes a circulating fan  41  to forcibly circulate the interior air of the cooking compartment  10  into the superheated steam supply unit  40  through the inlet holes  15  and again into the cooking compartment  10  through the outlet holes  16 , a superheating heater  42  to heat the circulating air, so as to change steam included in the air into superheated steam, a case  43  coupled to the associated lateral plate  13  to encase the circulating fan  41  and superheating heater  42 , and a motor  44  mounted to an outer surface of the case  43  and used to operate the circulating fan  41 . With this configuration, a superheated steam duct  45  is defined between an outer surface of the lateral plate  13  and the case  43 , and the circulating fan  41  and superheating heater  42  are located in the superheated steam duct  45 . The interior air of the cooking compartment  10  is introduced into the superheated steam duct  45  through the inlet holes  15 , and again returned into the cooking compartment  10  through the outlet holes  16  after being changed to the superheated steam by the superheating heater  42 .  
      The plate-shaped heater  50 , which is included in the steam generating unit  30  of the steam cooking apparatus consistent with the present invention, forms the bottom wall of the steam generating container  31 . The plate-shaped heater  50  is provided with resistors, which are patterned into a ladder shape, to obtain a maximum electric heating area.  
      The plate-shaped heater  50  is a heater designed by pattern printing a resistor on an insulating substrate by a printed circuit board (PCB) technique to allow the substrate to emit heat by itself. The plate-shaped heater  50  has an advantage of enabling rapid heating. In the steam cooking apparatus of the present invention, especially, the plate-shaped heater  50  forms the bottom wall of the steam generating container  31 . Therefore, even when only a small amount of water exists in the steam generating container  31 , instantaneous steam generation by the plate-shaped heater  50  is possible.  
      The plate-shaped heater  50  forming the bottom wall of the steam generating container  31  includes an insulating substrate  51 , a plurality of heating elements  52  and  53  to generate a preset amount of heat by use of the resistors pattern-printed on a surface of the insulating substrate  51  if power is applied thereto, and power input/output terminals  54 ,  55 , and  56  formed at ends of the pattern-printed resistors for supplying power to the heating elements  52  and  53 .  
      The insulating substrate  51  takes the form of an approximately rectangular thin plate, and has a size corresponding to the bottom area of the steam generating container  31 .  
      The heating elements  52  and  53  are formed of the pattern-printed resistors. The resistors are pattern-printed on the insulating substrate  51  based on the fact that the resistance is proportional to the intrinsic resistance value and length of a resistor. Accordingly, even when constant power is supplied, the heating elements  52  and  53  can achieve a variety of desired outputs by changing the resistance of the heating resistors.  
      Depending on the pattern-printed shape of the resistors, two or more heating elements  52  and  53  may be provided, and these heating elements  52  and  53  are operable independently. For the convenience of explanation, in the present invention, it is assumed that the heating elements  52  and  53  include a first heating element  52  and a second heating element  53 , which have different outputs from each other.  
      Also, although the outputs of the heating elements  52  and  53  may be determined differently in consideration of the size of the cooking compartment, the supply amount of steam, and the like, in the exemplary embodiment of the present invention, it is assumed that a maximum output of the first heating element  52  is 600 W and a maximum output of the second heating element  53  is 400 W.  
      The first heating element  52  is formed of the pattern-printed resistor having an approximately ladder shape. One end of the resistor is connected to a first power input terminal  54  and the other end of the resistor is connected to a common power output terminal  55 .  
      The second heating element  53  has approximately the same shape as that of the first heating element  52 , and is located adjacent to the first heating element  52 . One end of the resistor forming the second heating element  53  is connected to a second power input terminal  56 , and the other end of the resistor is connected to the common power output terminal  55 .  
      Although the heating elements  52  and  53  may have power output terminals, respectively, in the present invention, only the single common power output terminal  55  is used, to achieve a reduction in the number of power output terminals as well as a simplified pattern of the resistors.  
      With the above described configuration, if the first power input terminal  54  and common power output terminal  55  are connected to each other, the first heating element  52  is operated. In this case, the plate-shaped heater  50  acts to heat the water received in the steam generating container  31  with an output of 400 W. If the second power input terminal  56  and common power output terminal  55  are connected to each other, the second heating element  53  is operated. In this case, the plate-shaped heater  50  exhibits an output of 600 W. Also, if both the first and second power input terminals  54  and  56  are simultaneously connected to the common power output terminal  55 , the plate-shaped heater  50  is able to heat the water received in the steam generating container  31  with an output of 1000 W, thereby achieving more rapid generation of an increased amount of steam.  
      At least one temperature sensor  57  may be provided at the center of the insulating substrate  51 , or at the center of each heating element  52  or  53 , to measure a temperature of the plate-shaped heater  50 .  
      Hereinafter, the operation of the steam cooking apparatus having the above described configuration consistent with the present invention will be explained with reference to the drawings.  
      If a user puts food into the cooking compartment  10  and inputs a cooking command by operating the control panel  3 , the pump  24  is operated, to supply water from the water supply unit  20  into the steam generating container  31  of the steam generating unit  30 .  
      To generate steam depending on different cooking commands, it is preset whether the plurality of heating elements  52  and  53  are simultaneously operated or independently operated. For example, for a cooking command to cook food rapidly with a great amount of steam, the first and second heating elements  52  and  53  are operated simultaneously, to heat the water received in the steam generating container  31  with a total output of 1000 W, so as to generate an increased amount of steam more rapidly. If a cooking command requiring an intermediate level of quickness is input, only the second heating element  53  is operated, and if a cooking command requiring a low level of quickness is input, the first heating element  52  is operated, so as to generate steam based on the preset conditions.  
      Accordingly, if the water is supplied into the steam generating container  31  based on the input cooking command, the first heating element  52  and/or second heating element  53  of the plate-shaped heater  50  are operated to exhibit the preset output, so as to generate a predetermined amount of steam in response to the input cooking command.  
      In this case, if no water is supplied into the steam generating container  31  or the previously supplied water is wholly changed into steam and thus, no water exists in the steam generating container  31 , the steam generating container  31  may suffer from a rapid increase in temperature. The temperature sensor  57  provided in the plate-shaped heater  50  senses the increase in the temperature of the steam generating container  31 , so as to intercept power if the temperature of the plate-shaped heater  50  increases beyond a predetermined temperature.  
      The steam, which is generated in the steam generating unit  30  by the heating operation of the plate-shaped heater  50 , is introduced into the cooking compartment  10  through the steam supply duct  34 , and in turn, is delivered into the superheated steam duct  45  through the inlet holes  15  in accordance with operation of the circulating fans  41  of the superheated steam supply units  40 . Thereby, the steam is changed into superheated steam having a higher temperature by operation of the circulating fans  41  and superheating heaters  42  disposed in the superheated steam ducts  45 . Then, the superheated steam is supplied into the cooking compartment  10  through the plurality of outlet holes  16  perforated in the lateral plates  13  of the cooking compartment  10 .  
      With the above described procedure, a forcible circulating operation for continuously changing the interior air of the cooking compartment  10  into the superheated steam by operation of the circulating fans  41  and superheating heaters  42  and returning the resulting superheated steam into the cooking compartment  10  can be achieved.  
      Thereafter, if food is completely cooked, one-cycle of cooking ends, and the water remaining in the steam generating container  31  is discharged to the bottom plate  12  of the cooking compartment  10  through the drain pipe  36 .  
      Now, a steam cooking apparatus consistent with another embodiment of the present invention will be explained. The same constituent elements as those of the above described embodiment of the present invention will be designated as the same reference numerals, and detailed description thereof will be omitted.  
       FIG. 5  is a perspective view showing the configuration of a steam cooking apparatus consistent with another exemplary embodiment of the present invention.  FIG. 6  is an exploded perspective view showing the configuration of a steam generating unit shown in  FIG. 5 .  FIG. 7  is a sectional view taken along the line A-A′ of  FIG. 5 .  
      The steam generating unit consistent with another embodiment of the present invention, as shown in  FIGS. 5 and 6 , includes the steam generating unit  31  installed on the cooking compartment  10  and used to receive water therein, a plate-shaped heater  80  mounted to the steam generating container  31  and adapted to heat the water received in the steam generating container  31  so as to generate steam, and a water level sensing device  60  to sense the level of water in order to inform a user of a need to add water when the water in the steam generating container  31  is exhausted.  
      The plate-shaped heater  80  is mounted to the bottom of the steam generating container  31  at the outside of the container  31 , to heat the water received in the steam generating container  31 . Although the plate-shaped heater  80  may have a plurality of heating elements similar to the above described embodiment of the present invention, in the present embodiment, the plate-shaped heater  80  may include a single heating element, and may be installed at an outer lower surface of the steam generating container  31 .  
      The water level sensing device  60 , as shown in  FIG. 6 , includes a float  62  disposed in the steam generating container  31  and adapted to move up and down depending on a variation in the level of water, and a water level sensor  61  to sense a position of the float  62  to thereby sense the level of water.  
      The water level sensor  61  has a rod shape having a predetermined length so that it is inserted into a sensor insertion hole  37  perforated in the top of the steam generating container  31  to be spaced apart from the bottom of the steam generating container  31  by a predetermined distance. The float  62  has a centrally opened doughnut shape. Accordingly, the float  62  is inserted around the water level sensor  61  so that it is movable up and down while surrounding an outer circumference of the water level sensor  61 . The doughnut shaped float  62  is formed, at an inner circumference thereof, with a magnet.  
      The water level sensor  61  is circumferentially formed with a flange portion  61   a  at a position near an upper end thereof. The flange portion  61   a  is configured to be seated on an outer upper surface of the steam generating container  31 . A rubber packing  63  is interposed between a lower surface of the flange portion  61   a  and the upper surface of the steam generating container  31 , to prevent leakage of steam.  
      The water level sensor  61  is further circumferentially formed with a stopper  61   b  at a position near a lower end thereof. The stopper  61   b  serves to allow the float  62  to move up and down without the risk of unintentional separation from the water level sensor  61 . The stopper  61   b  is formed at an upper surface thereof with contact switches  61   c.  With this configuration, if the float  62  moves downward and comes into contact with the contact switches  61   c , the water level sensor  61  sends a float sensing signal to a controller (not shown), to cause water to be supplied into the steam generating container  31  until the level of water in the steam generating container  31  reaches a predetermined value.  
      The steam generating container  31  is provided therein with an intercepting member  70 . The intercepting member  70  is used to divide the interior of the steam generating container  31  into a water level sensing chamber  39 , in which the water level sensing device  60  is located, and a steam generating chamber  38 , to which the plate-shaped heater  80  is mounted. While the water received in the steam generating container  31  is heated and boiled by the plate-shaped heater  80  mounted to the outer lower surface of the steam generating container  31 , accordingly, the intercepting member  70  serves to prevent the fluctuation of the level of the boiling water from being transmitted to the float  62  of the water level sensing device  60 . The intercepting member  70  is positioned to divide the steam generating container  31  into two regions such that the steam generating chamber  38  has the same area as that of the plate-shaped heater  80  and the water level sensing chamber  39  for receiving the water level sensing device  60  is defined in the remaining region of the steam generating container  31 .  
      The intercepting member  70  takes the form of a plate-shaped partition. The plate-shaped intercepting member  70  has an upper end and opposite lateral ends attached to a top surface and opposite sidewall surfaces of the steam generating container  31  and a lower end spaced apart from a bottom surface of the steam generating container  31  to define an opening  72 . Accordingly, if water is supplied into the steam generating chamber  38  of the steam generating container  31 , a part of the supplied water is introduced into the water level sensing chamber  39  through the opening  72 , to thereby be stored in both the steam generating chamber  38  and water level sensing chamber  39 .  
      The intercepting member  70  has a plurality of communicating holes  71  perforated in an upper portion thereof. The communicating holes  71  serve as air passages between the water level sensing chamber  39  and the steam generating chamber  38 , thereby keeping both the water level sensing chamber  39  and the steam generating chamber  38  at the same pressure as each other and consequently, at the same water level as each other. This allows the water level sensing device  60  to accurately sense the level of water throughout the steam generating container  31 .  
      The operation and effects of the steam cooking apparatus having the above described configuration will be explained with reference to  FIGS. 5 and 7 .  
      If a user puts food into the cooking compartment  10  and inputs a cooking command by operating the control panel  3 , the pump  24  is operated, to supply water from the water supply unit  20  into the steam generating container  31  of the steam generating unit  30 . A part of the supplied water is introduced into the water level sensing chamber  39  through the opening  72 . Since the interior of the steam generating container  31  is kept at an even pressure by virtue of the communication holes  71  perforated in the upper portion of the intercepting member  70 , the water level sensing chamber  39  and steam generating chamber  38  have the same water level as each other.  
      If the level of water received in the steam generating container  31  reaches a predetermined value, the water level sensor  61  senses the upward movement of the float  62 , and sends a signal to a controller (not shown). Thereby, in a state wherein a water supply valve is switched off by the controller, the water received in the steam generating container  31  is heated by the plate-shaped heater  80 , to generate steam.  
      In this case, since the water stored in the steam generating chamber  38  of the steam generating container  31  is directly heated by the plate-shaped heater  80 , the steam generating chamber  38  experiences significant fluctuation of water level while the water is heated and boiled. However, in the present invention, the intercepting member  70  intercepts the fluctuation of water level generated in the steam generating chamber  38 , and therefore, no fluctuation of water level is transmitted to the water level sensing chamber  39 .  
      Accordingly, the water level sensing chamber  39  is not affected by the fluctuation of water level caused when the water is boiled in the steam generating chamber  38 , and can keep a stable water level. This consequently prevents the float  72  from moving up and down along the level of the boiling water, and the water level sensing device  60  from generating a false sensing signal. In this way, the water level sensing device  60  of the present invention can more stably and accurately sense the water level as compared to the prior art.  
      As apparent from the above description, the present invention provides a steam cooking apparatus in which a plate-shaped heater is mounted to a steam generating unit, thereby achieving more rapid generation of steam.  
      The plate-shaped heater included in the steam cooking apparatus of the present invention has a plurality of heating elements capable of realizing a variety of outputs. Accordingly, when it is desired to cook a variety of foods, the plate-shaped heater can achieve a proper steam supply function for providing each food with a desired amount of steam.  
      Further, according to the present invention, the heating elements have a single common power output terminal to thereby achieve a reduction in the number of output terminals. This also has the effect of simplifying the pattern printing of resistors, resulting in a reduction in manufacturing costs.  
      Furthermore, a steam generating container consistent with the present invention is provided with an intercepting member to divide the interior of the steam generating container into a water level sensing chamber and a steam generating chamber. The intercepting member serves to prevent fluctuation of water level in the water level sensing chamber, thereby enabling more accurate sensing of the water level.  
      Although embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in this embodiment without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.