Abstract:
The present invention provides a cooking stove that prevents a burner from being ignited when a touch switch shifts from a non-sensing state to a sensing state owing to a factor different from a user&#39;s operation. A cooking stove includes an operation portion  6  having a touch switch provided on a glass top plate  2  covering a top surface of a cooking stove main body  1  accommodating burners  4   a  and  4   b , the touch switch allowing a user to give an instruction on actuation and stoppage of the burners  4   a  and  4   b , the touch switch sensing an object that contacts or approaches the top surface of the glass top plate  2 , and heating control means for determining whether the touch switch is on (a sensing state) or off (a non-sensing state) to control actuation of the heating means in accordance with a result of the determination. While the burner  4   a  or  4   b  is at a stop, when the touch switch is turned on and then off again, the heating control means ignites the burner  4   a  or  4   b . While the burner  4   a  or  4   b  is in operation, when the touch switch is turned on, the heating control means extinguishes the burner  4   a  or  4   b.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a cooking stove comprising heating means, and in particular, to a cooking stove comprising an operation section that indicates an operation of heating means on a top surface of a top plate.  
         [0003]     2. Description of the Related Art  
         [0004]     A drop-in type cooking stove is conventionally known in which a cooking stove main body  101  is buried in an opening formed in a counter top of a system kitchen as shown in  FIG. 10 . Operation knobs  103   a  and  103   b  are provided on a glass top plate  102  to ignite and extinguish gas burners  100   a  and  100   b  and to adjust thermal power; the glass top plate  102  covers a top surface of the cooking stove main body  101  in which gas burners  100   a  and  100   b  are accommodated (see, for example, Japanese Utility Model Laid-Open No. 58-186302 (1983)).  
         [0005]     Such a cooking stove eliminates the need to form an opening through which an operation section is viewed, in a front surface of the counter top as in the case in which a cooking stove comprising an operation section in a front surface is installed. The cooking stove can be easily installed in the counter top. Further, the gas burners can be ignited and extinguished and thermal power adjusted using the operation knobs  103   a  and  103   b , provided on the top plate  102  and which are thus easy to see. Consequently, a user can operate the cooking stove more easily and effectively.  
         [0006]     In accordance with the cooking stove shown in  FIG. 10 , however, the operation knobs  103   a  and  103   b  are arranged so as to project from the top surface of the glass top plate  102 . Accordingly, the operation knobs  103   a  and  103   b  may obstruct cooking. Thus, for example, a detecting section of an electrical-capacitance sensor may be provided on a back surface of the glass top plate  102  as means for operating the gas burners  100   a  and  100   b . On the other hand, a touch switch comprising an operation section may be constructed on a front surface of the glass top plate  102 . Further, the top surface of the glass top plate  102  may be made flat.  
         [0007]     However, if the touch switches are provided as described above, any of them may be turned on when covered with a cooked material boiling over from a pan or the like placed on trivets  104   a  and  104   b  or with an object falling onto the glass top plate  102 . Further, a child may tamper with any of the touch switches or a user may unconsciously touch any of the touch switches.  
         [0008]     Thus, for example, while cooking is being carried out using only the right burner  100   b , a lighting switch for the left burner  100   a  may be turned on by a cooked material boiling over from a pan placed on the trivet  104   b  of the right burner  100   b . In this case, the left burner  100   a  is ignited.  
         [0009]     It is thus an object of the present invention to eliminate these disadvantages to provide a cooking stove that prevents a burner from being ignited when a touch switch shifts from a non-sensing state to a sensing state contrary to a user&#39;s expectations owing to, for example, a factor different from the user&#39;s operation.  
       SUMMARY OF THE INVENTION  
       [0010]     To accomplish the above object, the present invention relates to improvements in a cooking stove comprising a touch switch provided on a top plate covering a top surface of a cooking stove main body accommodating heating means, allowing a user to give an instruction on actuation and stoppage of the heating means, the touch switch sensing an object contacting with or approaching the top surface of the top plate, and heating control means for determining whether the touch switch is in a sensing state or a non-sensing state to control actuation of the heating means in accordance with a result of the determination.  
         [0011]     The present invention is characterized in that while the heating means is at a stop, when the touch switch shifts from the non-sensing state to the sensing state and then back to the non-sensing state, the heating control means starts actuating the heating means, and in that while the heating means is in operation, when the touch switch shifts from the non-sensing state to the sensing state, the heating control means stops actuating the heating means.  
         [0012]     According to the present invention, when the touch switch shifts from the non-sensing state to the sensing state and then back to the non-sensing state, the heating control means starts actuating the heating means. Thus, even if the touch switch shifts to the sensing state when covered with a boiling-over cooked material or a fallen object (cloth or the like) falling onto the top plate, the heating control means does not start actuating the heating means because the touch switch has not returned to the non-sensing state.  
         [0013]     Moreover, while the heating means is in operation, when the touch switch shifts from the non-sensing state to the sensing state, the heating control means stops actuating the heating means. To start actuating the heating means, the user must touch the touch switch with his or her finger and then take off the finger. However, to stop the heating means, the user can stop the operation of the heating simply by touching the touch switch with his or her finger. The cooking stove is thus convenient.  
         [0014]     The present invention is also characterized by further comprising a plurality of the touch switches, and in that while the heating means is at a stop, when at least pre-selected two of the plurality of switches shift from the non-sensing state to the sensing state, the heating control means starts actuating the heating means.  
         [0015]     According to the present invention, when at least pre-selected two of the plurality of switches shift from the non-sensing state to the sensing state, the heating control means starts actuating the heating means. Thus, when the user unconsciously touches one of the touch switches or only one of the touch switches shifts from the non-sensing state to the sensing state owing to a child&#39;s tampering or a boiling-over cooked material, the heating means is not activated. This makes it possible to prevent the heating means from being activated contrary to the user&#39;s expectations.  
         [0016]     Further, the present invention is characterized in that while the heating means is at a stop, when at least pre-selected two of the plurality of switches shift from the non-sensing state to the sensing state in a preset order, the heating control means starts actuating the heating means.  
         [0017]     According to the present invention, when a plurality of pre-selected switches shift from the non-sensing state to the sensing state and then back to the non-sensing state in a preset order, the heating control means starts actuating the heating means. It is assumed that the plurality of touch switches are very unlikely to shift from the sensing state to the non-sensing state and then back to the sensing state in the above order because of a boiling-over cooked material or a fallen object. This makes it possible to inhibit the heating means from being actuated when the touch switch mistakenly senses a boiling-over cooked material or a fallen object.  
         [0018]     Furthermore, the present invention is characterized by further comprising heat quantity changing means for changing the heat quantity of the heating means, and in that the plurality of touch switches include an actuation ready switch used to allow the heating means to be activated and a heat quantity up switch used to instruct the heat quantity changing means to increase the heat quantity of the heating means, and in that when the actuation ready switch shifts from the non-sensing state to the sensing state and then the heat quantity up switch shifts from the non-sensing state to the sensing state, in accordance with the preset order, the heating control means starts actuating the heating means.  
         [0019]     According to the present invention, the heat quantity up switch is also used to give an instruction on actuation of the heating means. This enables a reduction in the number of touch switches to be prepared. Further, an operation of starting actuating the heating means is conceptually contained in an “instruction on an increase in heat quantity”. Accordingly, the user does not have an incongruous feeling when operating the heat quantity up switch to give an instruction on actuation of the heating means. Therefore, the user can conveniently use the cooking stove.  
         [0020]     The present invention is characterized by further comprising at least two heating means, and in that one of the plurality of switches is an operation switch used to shift between an operation state in which the user can operate the other touch switches and a standby switch in which the user cannot operate the other touch switches, and in the operation state, when the at least two of the plurality of touch switches shift from the non-sensing state to the sensing state, the two touch switches being pre-selected for the respective heating means and being different from the operation switch, the heating control means start actuating the heating means corresponding to the at least two touch switches.  
         [0021]     According to the present invention, if in the standby state, an instruction is given on actuation of any of the heating means, the user first operates the operation switch to switch the standby state to the operation state. Thus, even if the process of starting actuating the heating means is executed when any one of the other touch switches shifts from the non-sensing state to the sensing state, two touch switches must be operated in order to give an instruction on actuation of the heating means.  
         [0022]     It is assumed that in the operation state, while one of the at least two heating means is in operation, an instruction is given on actuation of a second heating means. Then, if a process of starting actuating the second heating means is executed when a touch switch different from the operation switch shifts from the non-sensing state to the sensing state, the operation of the one touch switch starts actuating the second heating means. In this case, when one touch switch shifts from the non-sensing state to the sensing state owing to the user&#39;s unconscious operation, a child&#39;s tampering, or the like, the second heating means starts to be activated.  
         [0023]     Thus, according to the present invention, when at least two touch switches different from the operation switch shift from the non-sensing state to the sensing state, the heating means starts to be actuated. This makes it possible to prevent one of the at least two heating means from starting to be actuated contrary to the user&#39;s expectations.  
         [0024]     Moreover, the present invention is characterized by further comprising heat quantity changing means provided individually for the at least two heating means, and in that the plurality of touch switches include actuation ready switches provided individually for the at least two heating means to allow each heating means to be activated and heat quantity up switches used to instruct the heat quantity changing means to increase the heat quantities of the respective heating means, and in that in the operation state, when the actuation ready switch provided for one of the heating means shifts from the non-sensing state to the sensing state and then the heat quantity up switch provided for the heating means shifts from the non-sensing state to the sensing state, the heating control means starts actuating the heating means.  
         [0025]     According to the present invention, if at least two of the heating means are provided and the actuation ready switch and the heat quantity up switch are provided individually for each heating means, the heat quantity up switch is also used to given an instruction on actuation of the heating means. This eliminates the need for providing exclusive switches each used to give an instruction on actuation of the corresponding heating means. This enables a reduction in the number of touch switches to be prepared.  
         [0026]     Further, the present invention is characterized in that when the heating means is in operation and one of the pre-selected touch switches shifts from the non-sensing state to the sensing state, the heating control means stops actuating the heating means.  
         [0027]     According to the present invention, when the heating means is in operation, the heating control means knows that an instruction on actuation of the heating means has shifted all the preset switches from the sensing state to the non-sensing state. Thus, all the pre-selected touch switches were not in a failure state in which they cannot be shifted from the non-sensing state to the sensing state.  
         [0028]     Thus, by stopping the operation of the heating means when any of the pre-selected touch switches shifts from the non-sensing state to the sensing state, it is possible to reduce the possibility that a failure in any touch switch prevents the operation of the heating means from being stopped.  
         [0029]     Moreover, the present invention is characterized by further comprising lighting means provided on the top plate; and lighting control means for, while the heating means is in operation, lighting the lighting means, and while the heating means is in suspension, when the touch switch shifts from the non-sensing state to the sensing state, lighting the lighting means before the heating control means starts actuating the heating means.  
         [0030]     According to the present invention, when the user touches the touch switch with his or her finger to give an instruction on actuation of the heating means, the heating control means actually starts actuating the heating means when the user takes his or her finger off the touch switch. Thus, if there is a long time interval after the user has touched the touch switch and before the user takes his or her finger off, then nothing changes in spite of the touch with the touch switch. Consequently, the user may have an incongruous feeling.  
         [0031]     Thus, when the touch switch shifts from the non-sensing state to the sensing state, the lighting control means lights the lighting means before the heating control means starts actuating the heating means. The user can thus be noticed that an instruction on actuation of the heating means has been accepted. This inhibits the user from having an incongruous feeling. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0032]      FIG. 1  is a diagram showing the appearance of a cooking stove according to the present invention;  
         [0033]      FIG. 2  is a detailed diagram of an operation section shown in  FIG. 1 ;  
         [0034]      FIG. 3  is a control block diagram of the cooking stove;  
         [0035]      FIG. 4  is a flowchart of a process of igniting a burner;  
         [0036]      FIG. 5  is a flowchart of a process of igniting a burner;  
         [0037]      FIG. 6  is a flowchart of a process of igniting a burner;  
         [0038]      FIG. 7  is a flowchart of child lock and child unlock;  
         [0039]      FIG. 8  is a flowchart of a burner extinguishing process;  
         [0040]      FIG. 9  is a flowchart of a burner extinguishing process; and  
         [0041]      FIG. 10  is a diagram showing the appliance of a conventional cooking stove. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0042]     An embodiment of the present invention will be described with reference to FIGS.  1  to  9 .  FIG. 1  is a diagram showing the appearance of a cooking stove according to the present invention.  FIG. 2  is a detailed diagram of an operation section shown in  FIG. 1 .  FIG. 3  is a control block diagram of the cooking stove. FIGS.  4  to  6  are flowcharts of a process of turning on a burner.  FIG. 7  is a flowchart of child lock and child unlock processes.  FIGS. 8 and 9  are flowcharts of burner extinguishing processes.  
         [0043]      FIG. 1  shows a drop-in type cooking stove in which a glass top plate  2  formed of crystallized glass, which has an excellent heat resistance, is installed on a top surface of a cooking stove main body  1 . A lateral pair of cooking stove openings  3   a  and  3   b  is formed in the glass top plate  2 . With reference to  FIG. 1A , a left burner  4   a  and a right burner  4   b  (corresponding to heating means according to the present invention) are provided in the cooking stove main body  1  so as to be viewed through the cooking stove openings  3   a  and  3   b . Further, trivets  5   a  and  5   b  are arranged in the cooking stove openings  3   a  and  3   b ; cooking containers are placed on the trivets  5   a  and  5   b . An operation section  6  is provided in the front of a top surface of the glass top plate  2  to give an instruction for activating the left burner  4   a  and the right burner  4   b.    
         [0044]     With reference to  FIG. 2 , the operation section  6  comprises an operation switch  10  that switches between an “operation state” in which the left burner  4   a  and the right burner  4   b  can be instructed on actuation while the cooking stove remains powered on and a “standby state” in which the burners cannot be instructed on actuation. In the “operation state”, all the switches except the operation switch  10  can be operated. In the “standby state”, no switches other than the operation switch  10  can be operated.  
         [0045]     Further, in order to give an instruction on actuation of the left burner  4   a , the operation portion  6  has an ignition ready switch  11   a  (corresponding to an actuation ready switch according to the present invention) that establishes an ignition ready state in which the left burner  4   a  is allowed to be ignited, a thermal power down switch  12   a  and a thermal power up switch  13   a  (corresponding to a heat quantity up switch according to the present invention) which switch the thermal power of the left burner  4   a  among five levels (levels  1  to  5 ), an ignition ready display portion  14   a  lighted while the left burner  4   a  is in the ignition ready state and while the left burner  4   a  is in operation, and a thermal power level display portion  15   a  that displays a thermal power setting for the left burner  4   a.    
         [0046]     While the left burner  4   a  is ready for ignition, when the thermal power up switch  13   a  is operated, the left burner  4   a  is ignited. On the other hand, while the left burner  4   a  is in operation, when the ignition ready switch  11   a  or the operation switch  10  is operated, the left burner  4   a  is turned off.  
         [0047]     Similarly, to instruct the right burner  4   b  on actuation, the operation section  6  is provided with an ignition ready switch  11   b  (corresponding to an actuation ready switch according to the present invention) that allows the right burner  4   b  to get ready for, and to permit, ignition, a thermal power down switch  12   b  and a thermal power up switch  13   b  (corresponding to a heat quantity up switch according to the present invention) which switch the thermal power of the right burner  4   b  among five levels (levels  1  to  5 ), an ignition ready display section  14   b  that is lighted while the right burner  4   b  is ready for ignition or is in operation, and thermal power level display section  15   b  that displays a setting for the thermal power of the right burner  4   b.    
         [0048]     While the right burner  4   b  is ready for ignition, when the thermal power up switch  13   b  is operated, the right burner  4   b  is ignited. On the other hand, while the right burner  4   b  is in operation, when the ignition ready switch  11   b  or the operation switch  10  is operated, the right burner  4   b  is turned off.  
         [0049]     Moreover, the operation section  6  comprises an unlock display section  16  that is lighted in the “operation state” and a lock display section  17  that is lighted when the operations of all the switches are disabled, that is, the appliance is brought into a child lock state, after the operation switch  10  has been continuously operated for more than a predetermined time (for example 4 seconds).  
         [0050]     Each of the switches of the operation section  6  is a non-contact type touch switch composed of an electrical-capacitance sensor provided on a back surface of the glass top plate  2  and a print portion printed on a part of the front surface of the glass top plate  2  which is opposite the electrical-capacitance sensor, the print portion showing a touch point of the switch. When an electrostatic object is placed on the print portion (part of the front surface of the glass top plate  2  which is opposite the electrical-capacitance sensor), the electrical-capacitance sensor detects the electrostatic object to turn on the touch switch (this corresponds to a sensing state according to the present invention). When the electrostatic object is not placed on the print portion, the electrical-capacitance sensor does not detect the electrostatic object, the touch switch remains off (this corresponds to a non-sensing state according to the present invention).  
         [0051]     Further, each of the display sections of the operation section  6  is composed of a LED provided on the back surface of the glass top plate  2  and a print portion printed on a part of the front surface of the glass top plate  2  which is opposite the LED. When the LED is turned on, the display section is lighted. When the LED is turned off, the display section is extinguished. The display portion may be composed only of lighting means such as a LED provided on the back surface of the glass top plate  2  instead of the print portion provided on the front surface of the glass top plate  2 .  
         [0052]     The thermal power level display section  15   a  indicates the thermal power level (levels  1  to  5 ) of the left burner  4   a  using the number of lighting portions lighted, the lighting portions being provided in a bar display consisting of five lighting portions; the lighting starts with the leftmost lighting portion and the number of lighting portions lighted increments as the thermal power increases. For example, when the thermal power level of the left burner  4   a  is 1, the only the leftmost lighting portion of the bar display is lighted. When the thermal power level of the left burner  4   a  is 5, the five lighting portions of the bar display are all lighted. Similarly, the thermal power level display section  15   b  indicates the thermal power level (levels  1  to  5 ) of the right burner  4   b  using the number of lighting portions lighted, the lighting portion being provided in a bar display consisting of five lighting portions; the lighting starts with the leftmost lighting portion and the number of lighting portions lighted increments as the thermal power increases.  
         [0053]     Now, with reference to  FIG. 3 , the cooking stove main body  1  internally comprises a controller  30  that controls the general actuation of the cooking stove. A sensing signal for the operational state of each of the switches (operation switch  10 , ignition ready switches  11   a  and  11   b , thermal power down switches  12   a  and  12   b , and thermal power up switches  13   a  and  13   b ) of the operation section  6  is input to the controller  30 .  
         [0054]     Control signals output by the controller  30  controls the actuation of a gas source valve  40  that switches between the supply of fuel gas to the cooking stove main body  1  and the blockage of the supply, a left burner open and close valve  41   a  that switches between the supply of fuel gas to the left burner  4   a  and the blockage of the supply, a left burner thermal power adjusting valve  42   a  that varies the flow rate of fuel gas supplied to the left burner  4   a , a left burner igniter  43   a  that applies a high voltage to an ignition electrode (not shown) of the left burner  4   a  to cause spark discharge, a right burner open and close valve  41   b  that switches between the supply of fuel gas to the right burner  4   b  and the blockage of the supply, a right burner thermal power adjusting valve  42   b  that varies the flow rate of fuel gas supplied to the right burner  4   b , and a right burner igniter  43   b  that applies a high voltage to an ignition electrode (not shown) of the right burner  4   b  to cause spark discharge.  
         [0055]     Moreover, control signals from the controller  30  control lighting/extinction of the display sections provided in the operation section  6  (ignition ready display sections  14   a  and  14   b , thermal power level display sections  15   a  and  15   b , unlock display section  16 , and lock display section  17 ) and turn-on and off of a buzzer  18 .  
         [0056]     The controller  30  also comprises heating control means  31  for controlling the actuation of the left burner  4   a  and right burner  4   b , and lighting control means  32  for controlling the lighting/extinction of the display sections provided in the operation section  6  and reporting by the buzzer  18 .  
         [0057]     As described above, the touch switches provided in the operation section  6  sense whether or not an electrostatic object is present on the top surface of the glass top plate  2 . Thus, even though the user does not touch any touch switches with his or her finger, any of the touch switches may be turned on as follows. While the user is using only the left burner  4   a  to heat a cooked material in a pan  20 , as shown in  FIG. 1 ( b ) the cooked material may boil over from the pan and the boiling-over cooked material  21  reaches the operation section  6  to turn any of the touch switches for the right burner  4   b  from an off state to on state.  
         [0058]     The touch switch may also be turned on if the user unconsciously touches it during cooking or if a child tampers with it, or if the operation portion  6  is covered with an object (cloth or cooked material) having fallen onto the glass top plate  2  or with a cooking container placed on the glass top plate  2 .  
         [0059]     Thus, the heating control means  31 , provided in the controller  30 , executes a process required to prevent the left burner  4   a  or right burner  4   b  from being inadvertently ignited when the touch switch is turned off contrary to the user&#39;s expectations owing to, for example, a factor different from the user&#39;s operation. This process will be described in accordance with the flow chart in FIGS.  4  to  9 . The flowchart in FIGS.  4  to  9  corresponds to a process for the left burner  4   a . However, this also applies to a process for the right burner  4   b.    
         [0060]     First, STEP  1  to STEP  6  correspond to a process required to allow the user to recognize that the operation switch  10  has been turned on and then off again. When the cooking stove is powered on to start actuating the controller  30 , the cooking stove enters the “standby state”. Then, the heating control means  31  waits for the operation switch  10  to be turned on in STEP  1  in  FIG. 4 .  
         [0061]     Then, when the operation switch  10  is turned on, the process advances to STEP  2 . The heating control means  31  then starts a 2-second timer and a 4-second timer. In the subsequent loop of STEP  3  and STEP  30 , the heating control means  31  waits for the 2-second timer to time up in STEP  3 , while confirming in STEP  30  that the operation switch  10  is kept on.  
         [0062]     In STEP  3 , when the 2-second timer times up, that is, the operation switch  10  is kept on for at least 2 seconds, the process advances to STEP  4 . STEP  4  and STEP  5  are processing executed by the lighting control means  32 . The lighting control means  32  lights the unlock display portion  16  and activates the buzzer  18 . The user is thus noticed that the operation of the operation switch  10  has been accepted.  
         [0063]     In STEP  30 , when the operation switch  10  is turned off, the heating control means  31  can determine that the operation switch  10  was instantaneously turned on by noise or the like. Thus, in this case, the process returns to STEP  1 . The heating control means  31  then waits for the operation switch  10  to be turned on again.  
         [0064]     In the subsequent loop of STEP  6  and STEP  35 , the heating control means  31  waits for the operation switch to be turned off in STEP  6 , while confirming in STEP  35  that the 4-second timer has timed up.  
         [0065]     In STEP  6 , when the operation switch  10  is turned off, that is, the operation switch  10  is turned off within 4 seconds after the turn-on of the operation switch  10  in STEP  1 , the process advances to STEP  7 . The heating control means  31  then starts a 15-minute timer.  
         [0066]     In STEP  35 , when the 4-second timer times up, that is, the operation switch  10  is kept on for at least 4 seconds, the process advances to STEP  80  in  FIG. 7 .  FIG. 7  shows a child lock process. The lighting control means  32  extinguishes the unlock display portion  16  in STEP  80 , lights the lock display portion  17  in STEP  81 , and activates the buzzer  18  in STEP  82 .  
         [0067]     Then, in STEP  83 , the heating control means  31  waits for the operation switch  10  to be turned on. This keeps the cooking stove in a child lock state in which no switches can be operated until the operation switch  10  is operated to cancel the child lock state. When in the child lock state, the user touches the operation switch  10  to turn it on, the process proceeds from STEP  83  to STEP  84 . The heating control means  31  then starts the 4-second timer.  
         [0068]     Subsequently, in the subsequent loop of STEP  85  and STEP  90 , the heating control means  31  waits for the 4-second timer to time up in STEP  85 , while confirming in STEP  90  that the operation switch  10  is kept on. In STEP  85 , when the 4-second timer times up, that is, in the child lock state, the user continuously touches and keeps the operation switch  10  on for at least 4 seconds. The process then advances to STEP  86 . The lighting control means  32  extinguishes the lock display portion  17  in STEP  86  and activates the buzzer  18  in STEP  87 . The process advances to STEP  1  in  FIG. 4 . This cancels the child lock state.  
         [0069]     In STEP  6  in  FIG. 4 , when the operation switch  10  is turned off, that is, the operation switch  10  is turned off within 4 seconds after the turn-on of the operation switch  10  in STEP  1 , the process advances to STEP  7 . The controller  30  then starts a 15-minute timer.  
         [0070]     STEP  8  to STEP  14  in  FIG. 5  are processing required to determine that the ignition ready switch  11   a  has been turned on and then off again. In a loop of STEP  8  and STEP  40 , the heating control means  31  waits for the ignition ready switch  11   a  to be turned on in STEP  8 , while checking in STEP  40  whether or not the 15-minute timer has timed up. In STEP  8 , when the ignition ready switch  11   a  is turned on, the process advances to STEP  9  in  FIG. 5 .  
         [0071]     In STEP  40 , when the 15-minute timer times up, that is, the operation switch  10  is not turned on within 15 minutes after the turn-off of the operation switch  10  in STEP  6 , the process advances to STEP  41 . The controller  30  then extinguishes the unlock display portion  16  in STEP  41 , activates the buzzer  18  in STEP  42 , and returns to STEP  1  to enter the “standby state”. This allows the cooking stove to return to the “standby state” when an operation of igniting the left burner  4   a  is not performed within 15 minutes after the user has operated the operation switch  10 .  
         [0072]     In STEP  9  in  FIG. 5 , the heating control means  31  starts the 1-minute timer. Then, in the subsequent loop of STEP  10  and STEP  50 , the heating control means  31  waits for the 1-second timer to time up in STEP  10 , while checking in STEP  50  whether or not the ignition ready switch  11   a  is on. Then, in STEP  10 , when the 1-second timer times up, that is, the ignition ready switch  11   a  is kept on for at least 1 second, the process advances to STEP  11 .  
         [0073]     In STEP  50 , when the 1-second timer times up, that is, the ignition ready switch  11   a  is turned on for less than 1 second, the heating control means  31  can determine that the ignition ready switch  11   a  was instantaneously turned on by noise or the like. Thus, in this case, the process returns to STEP  7  in  FIG. 4 . The heating control means  31  then waits for the ignition ready switch  11   a  to be turned on.  
         [0074]     STEP  11  and STEP  12  are processing executed by the lighting control means  32 . The lighting control means  32  lights the ignition ready display portion  14   a  in STEP  11  and activates the buzzer  18  in STEP  12 . Then, in STEP  13 , the heating control means  31  starts a 2-second timer. In the subsequent loop of STEP  14  and STEP  55 , the heating control means  31  waits for the ignition ready switch  11   a  to be turned off in STEP  14 , while checking in STEP  55  whether or not the 2-second timer has timed up.  
         [0075]     In STEP  14 , when the ignition ready switch  11   a  is turned off, that is, the ignition ready switch  11   a  is turned off within 2 seconds after the ignition ready switch  11   a  has been kept on for 1 second, the process advances to STEP  15 . The heating control means  31  then starts a 10-second timer.  
         [0076]     In STEP  55 , when the 2-second timer times up, that is, the ignition ready switch  11   a  is kept on for 1 second and further for 2 seconds, the process advances to STEP  56 . Then, the controller  30  extinguishes the ignition ready display portion  14   a  in STEP  56  and activates the buzzer  18  in STEP  57 . The process then returns to STEP  7  in  FIG. 4 . Thus, when a boiling-over cooked material or the like causes the ignition ready switch  11   a  to remain on, the processing in and after STEP  15  is prohibited. The ignition of the left burner  4   a  is not carried out.  
         [0077]     Then, STEP  15  to STEP  19  in  FIG. 6  are processing required to determine that the thermal power up switch  13   a  has been turned on and then off again. In STEP  15 , the heating control means  31  starts a 10-second timer. The process then advances to STEP  16 . In a loop of STEP  16  and STEP  60 , the heating control means  31  waits for the thermal power switch  13   a  to be turned on in STEP  16 , while checking in STEP  60  whether or not the 10-second timer has timed up.  
         [0078]     In STEP  16 , when the thermal power up switch  13   a  is turned on, that is, the thermal power up switch  13   a  is turned on within 10 seconds after the ignition ready switch  11   a  has been turned off, the process advances to STEP  17 . STEP  17  and STEP  18  are processing executed by the lighting control means  32 . The lighting control means  32  lights the thermal power level display portion  15   a  at the level  4  in STEP  17  and activates the buzzer  18  in STEP  18 . The process advances to STEP  19 .  
         [0079]     In STEP  16 , when the thermal power up switch  13   a  is turned on, the thermal power level display portion  15   a  is lighted in STEP  17  before the left burner  4   a  is ignited in STEP  20  as described later. This notices the user that the ignition instruction has been accepted.  
         [0080]     In STEP  60 , when the 10-second timer times up, that is, the thermal power up switch  13   a  is not turned on within 10 seconds after the ignition ready switch  11   a  has been turned off, the process advances to STEP  61 . STEP  61  and STEP  62  are processing executed by the lighting control means  32 . The lighting control means  32  extinguishes the ignition ready display portion  14   a  in STEP  61  and activates the buzzer  18  in STEP  62 . The process returns to STEP  7  in  FIG. 4 . Thus, the heating control means  31  waits for the ignition ready switch  11   a  to be turned on again.  
         [0081]     In a loop of STEP  19  and STEP  65 , the heating control means  31  waits for the thermal power switch  13   a  to be turned off in STEP  19 , while checking in STEP  65  whether or not the 10-second timer has timed up. In STEP  19 , when the thermal power up switch  13   a  is turned off, the process advances to STEP  20 . The heating control means  31  actuates an igniter  43   a  to cause an ignition electrode to generate spark discharge. The heating control means  31  then opens the gas source valve  40  and the left burner open and close valve  41   a . The heating control means  31  further sets the left burner thermal power adjusting valve  42   a  to the thermal power level  4  to ignite the left burner  4   a.    
         [0082]     In STEP  65 , when the 10-second timer times up, that is, the turn-on and subsequent turn-off of the thermal power up switch  13   a  is not carried out within 10 seconds after the ignition ready switch  11   a  has been turned on, the process advances to STEP  66 . STEP  66  to STEP  68  are processing executed by the lighting control means  32 . The lighting control means  32  extinguishes the ignition ready display portion  14   a  in STEP  66 , extinguishes the thermal power level display portion  15   a , and activates the buzzer  18  in STEP  68 . The process returns to STEP  7  in  FIG. 4 .  
         [0083]     As described above, after the operation switch  10  has been turned on and then off again, the ignition ready switch  11   a  is turned on and then off again, and then the thermal power up switch  13   a  is turned on and then off again. Then, the heating control means  31  executes ignition of the left burner  4   a  (corresponding to the start of actuation of the heating means according to the present invention).  
         [0084]     This prevents the left burner  4   a  from being ignited even if a boiling-over cooked material or the like turns on the operation switch  10 , the ignition ready switch  11   a , and the thermal power up switch  13   a . Further, the left burner  4   a  is ignited only if these three switches are turned on and then off again in order of the operation switch  10 , the ignition ready switch  11   a , and the thermal power up switch  13   a.    
         [0085]     It seems unlikely that a boiling-over cooked material or the like turns these switches on and then off again in the above order. Accordingly, it is possible to reliably prevent ignition of the left burner  4   a  from being carried out owing to a factor different from the user&#39;s operation.  
         [0086]     Further, the left burner  4   a  is not ignited if the user unconsciously touches the operation portion  6  or if a child tampers with the operation portion  6  or if a boiling-over cooked material or the like turns on or further turns off again only one of the operation switch  10 , ignition ready switch  11   a , and thermal power up switch  13   a.    
         [0087]     Furthermore, even in the “operation state”, the left burner  4   a  is not ignited when only one of the ignition ready switch  11   a  and thermal power up switch  13   a  is turned on or further turned off again.  
         [0088]      FIGS. 8 and 9  are flowcharts of an operation of extinguishing a burner.  FIG. 8  is a flowchart showing the case in which the operation switch  10  is turned on while the burner is in operation.  FIG. 9  is a flowchart showing the case in which the ignition ready switch  11   a  is turned on while the burner is in operation.  
         [0089]     First, with reference to  FIG. 8 , when the operation switch  10  is turned on while the left burner  4   a  is in operation, the process advances from STEP  100  to STEP  101 . The heating control means  31  then starts a 1-second timer. Then, in a loop of STEP  102  and STEP  110 , the heating control means  31  waits for the 1-second timer to time up in STEP  102 , while checking in STEP  110  whether or not the operation switch  10  is on.  
         [0090]     In STEP  102 , when the 1-second timer times up, that is, the operation switch  10  is kept on for at least 1 second, the process advances to STEP  103 . STEP  103  to STEP  105  and STEP  107  are processing executed by the lighting control means  32 . In STEP  103  to STEP  105 , the lighting control means  32  extinguishes the ignition ready display portion  14   a , the thermal power level display portion  15   a , and the unlock display portion  16 .  
         [0091]     In STEP  106 , the heating control means  31  closes the left burner open and close valve  41   a  and gas source valve  40  to extinguish the left burner  4   a . In STEP  107 , the lighting control means  32  activates the buzzer  18  to notice the user that the burner  4   a  has been extinguished. The process then returns to STEP  1  in  FIG. 4 .  
         [0092]     With reference to  FIG. 9 , when the ignition ready switch  11   a  is turned on while the left burner  4   a  is in operation, the process advances from STEP  120  to STEP  121 . The controller  30  then starts a 1-second timer. Then, in a loop of STEP  122  and STEP  130 , the controller  30  waits for the 1-second timer to time up in STEP  122 , while checking in STEP  130  whether or not the ignition ready switch  11   a  is on.  
         [0093]     In STEP  122 , when the 1-second timer times up, that is, the ignition ready switch  11   a  is kept on for at least 1 second, the process advances to STEP  123 . STEP  123 , STEP  124 , and STEP  126  are processing executed by the lighting control means  32 . In STEP  123  and STEP  124 , the lighting control means  32  extinguishes the ignition ready display portion  14   a  and the thermal power level display portion  15   a.    
         [0094]     In STEP  125 , the heating control means  31  closes the left burner open and close valve  41   a  to extinguish the left burner  4   a . In STEP  126 , the lighting control means  32  activates the buzzer  18  to notice the user that the burner  4   a  has been extinguished. The process then returns to STEP  7  in  FIG. 4 .  
         [0095]     As described above, the left burner  4   a  is ignited when the operation switch  10 , the ignition ready switch  11   a , and the thermal power up switch  13   a  are turned on and then off again. This means that when the user performed an operation of igniting the left burner  4   a , the heating control means  31  had determined that none of the operation switch  10 , ignition ready switch  11   a , and thermal power up switch  13   a  were in an off failure (a failure that prevents the switch from being turned on) state.  
         [0096]     As shown in  FIGS. 8 and 9 , by executing a process of extinguishing the left burner  4   a  after the operation switch  10  and the ignition ready switch  11   a , which were not in the off failure state when an ignition operation was performed, have been turned on, it is possible to inhibit the extinction of the left burner  4   a  from being disabled by an off failure in the switches.  
         [0097]     In the present embodiment, the cooking stove comprising the gas burners  4   a  and  4   b  are shown as heating means according to the present invention. The present invention is applicable to a cooking stove comprising another type of heating means such as an electric heater.  
         [0098]     In the present embodiment, the illustrated cooking stove comprises the glass top plate  2 , composed of heat-resistant glass, as a top plate according to the present invention. However, the present invention is applicable to a cooking stove comprising a top plate composed of a different material such as stainless steel.  
         [0099]     In the present embodiment, the illustrated cooking stove employs the electrical capacitance touch switches as touch switches according to the present invention. However, the type of the touch switches is not limited to this. The present invention is applicable to a cooking stove employing photo switches comprising an infrared emitting/receiving section or mechanical point type touch switches such as tact switches.  
         [0100]     In the present embodiment, the illustrated cooking stove comprises two burners as heating means. However, the present invention is applicable to a cooking stove comprising one or at least three heating means.  
         [0101]     In the present embodiment, the illustrated cooking stove comprises the operation switch. However, the effects of the present invention can be produced even if the cooking stove has no operation switch.  
         [0102]     In the present embodiment, the thermal power up switches  13   a  and  13   b  are also used to give instructions on ignition of the left burner  4   a  and the right burner  4   b , respectively, thus reducing the number of touch switches in the operation portion  6 . However, it is possible to provide switches used to give instructions on ignition of the left burner  4   a  and the right burner  4   b , separately from the thermal power up switches  13   a  and  13   b.