Abstract:
A steam exhaust system of an electric pressurizing device which can control the pressure in a cooking vessel and simultaneously can prevent the pressure in the cooking vessel from excessively increasing during the cooking operation. In the steam exhaust system, a steam exhaust pipe penetrates a lid of the electric pressurizing device, and has a steam exhaust channel formed therein. A valve assembly is provided which includes a frame and a pressurizing plate. The valve assembly opens and closes the steam exhaust channel of the steam exhaust pipe by the pivoting of the pressurizing plate. A pressure control device actuates the valve assembly by way of a magnetic force to control the blocking pressure in the steam exhaust pipe.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an electric pressurizing rice cooker, and more particularly to a steam exhaust system of an electric pressurizing rice cooker, which can control the pressure in a cooking vessel and simultaneously can prevent the pressure in the cooking vessel from excessively elevating during the cooking process. 
     2. Description of the Related Art 
     An electric rice cooker is an appliance for cooking rice which utilizes electricity as a heating source. Especially in an electric pressurizing rice cooker, the interior of a cooking vessel is maintained at a relatively high pressure, higher than that of the atmosphere, so that the cooking in the cooking vessel can be rapidly performed. 
     As shown in FIG. 1, a conventional electric pressurizing rice cooker includes a cooking vessel  10 , a cooker housing  12  in which the cooking vessel  10  is accommodated, a lid  14  for opening and closing the cooker housing  12 , an electric system for heating/warming the cooking vessel  10 , and a steam exhaust system for controlling the pressure in the cooking vessel  10  during the course of cooking. 
     Referring to FIG. 2, the electric system includes a working coil  16  and a heater  18  disposed in the cooker housing  12 . The working coil  16  generates induced currents for cooking, and the heater  18  functions to generate relatively less heat for warming rice in a so-called warming mode. 
     Meanwhile, the steam exhaust system includes a solenoid valve  20  and a poise valve  30 . The solenoid valve  20  is automatically opened to lower the pressure in the cooking vessel  10  when a predetermined amount of time has passed after the cooking is initiated. The poise valve  30  is opened when the pressure in the cooking vessel  10  exceeds a predetermined value during the course of cooking to prevent the pressure in the cooking vessel from excessively elevating, and simultaneously to maintain the pressure constant. 
     As shown in FIG. 3, the solenoid valve  20  is disposed at a top plate  141  of the lid  14 , and includes a first steam exhaust pipe  22  interconnected to the exterior of a top cover  142 , a diaphragm  24  for opening and closing a steam hole  22   a  in the first steam exhaust pipe  22 , a plunger  26  assembled with the diaphragm  24 , and a solenoid coil  28  for actuating the plunger  26 . 
     The poise valve  30  as described above includes a second steam exhaust pipe  32  penetrating through the lid  14 , and a pressurizing weight  34  disposed at the upper end of the second steam exhaust pipe  32  outside of the lid  14 . 
     The pressurizing weight  34  supports a valve pin  35  received through the top of the pressurizing weight  34 , in such a manner that the valve pin  35  can open and close the upper end of a steam exhaust channel  32   a  of the second steam exhaust pipe  32 . The pressurizing weight  34  has an exhaust port  34   a  formed through the bottom of the pressurizing weight  34 , through which steam can be exhausted. 
     Hereinafter, will be described the cooking operation by the electric pressurizing rice cooker having the construction as described above. 
     At first, the working coil  16  induces eddy current at the cooking vessel  10 , which slowly heats the cooking vessel  10 , so as to promote a so-called soaking process during which water is absorbed in each grain of rice. After the soaking process is performed for a predetermined period, the cooking vessel is heated at a high temperature, so that the temperature of the water in which the rice is immersed is rapidly elevated to the boiling point. 
     In this case, the upper end of the cooking vessel  10  is firmly coupled to the lower surface of the top plate  141  by an assembling device (not shown), and the solenoid valve  20  and the poise valve  30 , which are parts of the steam exhaust device, are maintained in a closed position. Accordingly, when the boiling process is initiated and the water begins to boil, steam is generated to make the pressure in the cooking vessel  10  higher than that in the atmosphere. 
     Due to the increase of the pressure in the cooking vessel  10 , the temperature in the cooking vessel  10  elevates beyond the boiling point of 100° C. at the normal atmospheric pressure, so that the rice is cooked faster than at normal atmospheric pressure. 
     When the boiling process during a predetermined period is completed, a steaming process is initiated in the state where the heating is stopped. In the steaming process, the rice is steamed, without being separately heated, by the steam remaining in the cooking vessel after the boiling process, usually after the water is completely boiled away. 
     After the steaming process is completed for a predetermined amount of time, the steam in the cooking vessel  10  is exhausted by the operation of the solenoid valve  20 , so that the pressure in the cooking vessel  10  is lowered. In this state, a warming process is initiated in which the cooking vessel  10  is heated by a relatively low degree of heat, at a relatively low, constant temperature by means by the heater  18 . 
     In this case, when the solenoid valve  20  is operated, electric power is first applied to the solenoid coil  28  by a control section (not shown). Then, magnetic force generated by the solenoid coil  28  actuates the plunger  26 , which elastically deforms the diaphragm  24  to open the steam hole  22   a . Then, the steam in the cooking vessel  10  is exhausted through the opened steam hole  22   a  and steam channel of the first steam exhaust pipe  22  interconnected to the steam hole  22   a.    
     Further, when the pressure in the cooking vessel  10  becomes higher than a predetermined reference value during the course of the cooking operation, the poise valve  30  is operated to exhaust a desired amount of steam in the cooking vessel  10 , thereby preventing an excessive elevation of pressure. 
     Hereinafter will be described, in detail, the operation of the poise valve  30  as described above. 
     First, before the pressure in the cooking vessel  10  reaches a predetermined reference value, the steam exhaust channel  32   a  of the second steam exhaust pipe  32  is maintained closed by the valve pin  35 . This is because the valve pin  35  is forced downward due to the weight of the pressurizing weight  34  so as to block off the steam exhaust channel  32   a . When the pressure in the cooking vessel  10  exceeds the reference value, that is, the weight of the pressurizing weight  34 , the valve pin  35  is pushed upward causing the pressurizing weight  34  to vibrate and become cooked. The steam exhaust channel  32   a  is then opened, whereby the steam in the cooking vessel  10  is exhausted through the exhaust port  34   a  of the pressurizing weight  34 . The pressure in the cooking vessel  10  is then lowered below the reference value. 
     When the pressure in the cooking vessel  10  is lowered below the reference value, the pressurizing weight  34  recovers its balance due to its construction, so that the valve pin  35  again blocks off the steam exhaust channel  32   a , thereby preventing an excessive pressure reduction. The repetition of the above process maintains the pressure in the cooking vessel  10  in a predetermined range during the cooking process. 
     In the conventional electric pressurizing rice cooker as described above, effective cooking is achieved through the safe operation of and the pressure control of the steam exhaust system. 
     However, according to the conventional technique as described above, since the poise valve  30  maintains the pressure in the cooking vessel  10  at a predetermined level by means of the operation of the pressurizing weight  34  during the cooking operation, only pressurized cooking at a single predetermined pressure can be performed. Accordingly, there is a restriction in the conventional electric pressurizing rice cooker, in that it is impossible to cook food into various states according to the user&#39;s tastes by controlling the pressure in the cooking vessel  10 . 
     Further, the conventional electric pressurizing rice cooker is also problematic, in that its manufacturing cost is relatively high, since the solenoid valve  20  having a complicated construction and requiring a relatively large number of parts is necessary in addition to the poise valve  30  in the conventional cooker. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention has been made in an effort to solve the problems occurring in the related art, and thus it is an object of the present invention to provide a steam exhaust system for an electric pressurizing rice cooker, which can control the pressure in the cooking vessel and simultaneously can prevent the pressure in the cooking vessel from excessively elevating during the cooking operation. 
     In order to achieve the above object, the present invention provides a steam exhaust system of an electric pressurizing rice cooker, the steam exhaust system comprising a steam exhaust pipe which penetrates the lid of the electric pressurizing rice cooker, the steam exhaust pipe having a steam exhaust channel formed therein; a valve assembly including a frame and a pressurizing plate, the frame being assembled with the steam exhaust pipe, the pressurizing plate having a first end pivotally assembled with an upper end of the frame and a second end detachably fitted into an upper end of the steam exhaust pipe, the valve assembly opening and closing the steam exhaust channel of the steam exhaust pipe by the pivoting of the pressurizing plate. A pressure control means is provided for actuating the valve assembly by means of magnetic force, to control the blocking pressure in the steam exhaust pipe. 
     Preferably, the pressure control means includes an electromagnet for applying an attraction to the pressurizing plate, and a control section for controlling an electric power applied to the magnetic coil of the electromagnet. The electromagnet includes a bobbin and a magnetic coil. The bobbin is mounted to the frame and disposed under the pressurizing plate of the valve assembly. The magnetic coil surrounds the bobbin. 
     In accordance with another aspect of the present invention, instead of the above valve assembly, the steam exhaust system may have another valve assembly, which comprises: a valve cap having the shape of a tripod, the valve cap being disposed above the steam exhaust pipe, the valve cap being capable of moving up and down to thereby open and close the steam exhaust channel of the steam exhaust pipe; and a stand for supporting the valve cap, the valve cap being attached to the stand by means of a magnetic force. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above objects and other features and advantages of the present invention will become more apparent after the following detailed description when taken in conjunction with the drawings, wherein 
     FIG. 1 is a perspective view of a conventional electric pressurizing rice cooker; 
     FIG. 2 is a sectional view of the conventional electric pressurizing rice cooker shown in FIG. 1; 
     FIG. 3 is a sectional view of a solenoid valve employed in a conventional steam exhaust system of the conventional electric pressurizing rice cooker; 
     FIG. 4 is a sectional view of a poise valve employed in a conventional steam exhaust system of the conventional electric pressurizing rice cooker; 
     FIGS. 5 a  and  5   b  are sectional views of steam exhaust systems of an electric pressurizing rice cooker according to the present invention, showing the constructions and the operations thereof; and 
     FIG. 6 is a sectional view of a steam exhaust system of an electric pressurizing rice cooker according to another embodiment of the present invention, showing its construction and operation. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The above and other objects, characteristics, and advantages of the present invention will become apparent from the following description taken with the accompanying drawings, in which the same elements will be designated by the same reference numerals throughout the various figures. 
     Referring to FIGS. 5 a  and  5   b , the steam exhaust systems of an electric pressurizing rice cooker according to the various embodiments of the present invention include a steam exhaust pipe  40 , a valve assembly, and pressure control means. The steam exhaust pipe  40  is disposed penetrating the top plate  141  of the lid  14  and has a steam exhaust channel  40   a  formed in the steam exhaust pipe  40 . The valve assembly opens and closes the steam exhaust channel  40   a  of the steam exhaust pipe  40 . The pressure control means actuates the valve assembly by means of magnetic force, so as to control the blocking pressure in the steam exhaust pipe  40 . 
     The valve assembly includes a frame  42  and a pressurizing plate  44 . The frame  42  is assembled with the steam exhaust pipe  40 . One end of the pressurizing plate  44  is hingedly and pivotally assembled with the upper end of the frame  42 , and the other end of the pressurizing plate  44  is detachably fitted into an upper end of the steam exhaust pipe  40 . In this case, the pressurizing plate  44  has a sufficiently light weight which can not have a large influence on the pressure formation in the cooking vessel. 
     Moreover, a nozzle cap  441  having a conical shape is provided at a lower surface of the pressurizing plate  44  so that the opening and closing of the steam exhaust channel  40   a  can be performed more effectively. 
     In the meantime, the pressure control means includes an electromagnet  50  and a control section. The electromagnet  50  includes a bobbin  52  mounted to the frame  42  and disposed under the pressurizing plate  44  of the valve assembly, and a magnetic coil  54  surrounding the bobbin  52 . The electromagnet  50  applies an attraction to the pressurizing plate  44 , and the control section controls the electric power applied to the magnetic coil  54  of the electromagnet  50 . 
     The steam exhaust system having the construction as described above is classified into an integrated type and a separated type, according to the position of the electromagnet  50 . In the integrated type as shown in FIG. 5 a , the steam exhaust pipe  40  is inserted in the electromagnet  50 . In the separated type as shown in FIG. 5 b , the electromagnet  50  is distanced away from the steam exhaust pipe  40 . 
     By the steam exhaust systems according to the embodiments of the present invention as described above, the cooking can be performed selectively in a non-pressurizing mode and in a changeable-pressure mode, and an excessive pressure prevention function for preventing the pressure in the cooking vessel from excessively elevating can be performed. All of these advantageous functions and characteristics by the steam exhaust systems will be described in turn hereinafter. 
     First, in the non-pressurizing mode, even in the case where the pressure in the cooking vessel is elevated slightly over the atmospheric pressure, the pressurizing plate  44  is lifted up due to the light weight of the pressurizing plate  44 , so that the steam can be exhausted. Therefore, the pressure in the cooking vessel is always maintained at substantially atmospheric pressure. 
     Accordingly, the temperature of the water in the cooking vessel cannot be elevated above the boiling point of 100° C. under atmospheric pressure, no matter how much heat is applied thereto, and no matter how long the heat is applied thereto. This means that the rice can be cooked under atmospheric pressure by a cooker having the steam exhaust system of the present invention. 
     Further, in the changeable-pressure mode, the pressurizing plate  44  and the electromagnet  50  are assembled together by the magnetic force of the electromagnet  50  with a force stronger than atmospheric pressure. 
     Therefore, in the case where the blocking pressure formed by the pressurizing plate  44  assembled with the magnetic force of the electromagnet  50  is higher than the atmospheric pressure, the water contained in the cooking vessel has a boiling temperature which is higher than that experienced under atmospheric pressure, because of the pressure increase in the cooking vessel due to the steam being generated in the boiling process. 
     In the changeable-pressure mode as described above, by controlling the electric power applied to the electromagnet  50  by the control section, the assembling force between the electromagnet  50  and the pressurizing plate  44  is controlled, and accordingly the blocking pressure in the steam exhaust pipe  40  is controlled. According to this mode, in the case where the pressure in the cooking vessel exceeds the blocking pressure applied to the pressurizing plate  44 , the pressurizing plate  44  is pivoted about a hinge shaft and is lifted up as shown by the phantom lines in the drawings, so that the steam exhaust channel  40   a  can be opened. Thus, a predetermined amount of the steam in the cooking vessel is exhausted through the steam exhaust channel  40   a , so that the pressure is prevented from elevating above a predetermined value. Accordingly, the excessive pressure prevention function as described above is effectively performed. 
     After the pressure in the cooking vessel is decreased by the excessive pressure prevention function, the pressurizing plate  44  is assembled again with the electromagnet  50  to block off the steam exhaust channel  40   a , so that the pressure is again increased. 
     In the changeable-pressure mode, which is especially proper for heating food to a relatively high temperature, it is possible to cook at various temperatures according to the user&#39;s taste by controlling the electric power applied to the electromagnet  50  by means of the control section. 
     FIG. 6 show a steam exhaust system according to another embodiment of the present invention, wherein a valve assembly of the system includes a valve cap  60  having the shape of a tripod and a stand  62  having a semicircular section. The valve cap  60  is disposed above the steam exhaust pipe  40  in such a manner that the valve cap  60  can move up and down. The valve cap  60  is attached to and supported by the stand  62  a magnetic force. 
     According to this embodiment of the present invention, the valve cap  60  maintains its balance in the state of being loaded on the steam exhaust pipe  40  by its own weight, during the cooking in the non-pressurizing mode. On the other hand, during the cooking in the changeable-pressure mode, the valve cap  60  is attracted downward by the magnetic force generated by the electromagnet  50 , so as to block off the steam exhaust channel  40   a , thereby controlling the pressure in the cooking vessel. 
     When the excessive pressure prevention function is performed, the entire valve cap  60  is held at a predetermined distance above the stand  62  as shown by the phantom line in FIG. 6, so as to open the steam exhaust channel  40   a.    
     As described above, by utilizing the steam exhaust systems according to the embodiments of the present invention as described above, cooking can be performed selectively in a non-pressurizing mode and in a changeable-pressure mode, according to the user&#39;s taste. Further, even in the case of cooking in a so-called pressurizing mode, in which the interior of the cooking vessel is maintained pressurized while the cooking is performed, there is another advantage in that the state of the cooked rice can be selected in a variety of ranges by controlling the magnitude of the pressure in the cooking vessel. 
     The steam exhaust system according to the present invention can be employed, not only in a pressurized rice cooker, but also in other various cookers, such as all-purpose cookers, which use pressure control during cooking. 
     The steam exhaust system according to the present invention can perform the cooking selectively in the non-pressurizing mode and in the changeable-pressure mode, and can control the pressure in the cooking vessel  10  in the so-called pressurizing mode, as described above. Therefore, the cooking can be performed in various manners, according to the user&#39;s taste. This improves the marketability of the cooker. 
     Furthermore, the present invention makes the construction of the rice cooker simpler, since a separate safety member such as the poise valve  30  is not necessary in the steam exhaust system of the present invention. As a result, the marketability of the cooker is further improved. 
     While there have been illustrated and described what are considered to be the preferred specific embodiments of the present invention, it will be understood by those skilled in the art that the present invention is not limited to the specific embodiments thereof, and thus various changes and modifications and equivalents may be substituted for elements thereof without departing from the true spirit and scope of the present invention.