PURPOSE: To shut off combustion at a specified decision level at a specified oxygen concentration time, by a method wherein, in a combustion device having a device for preventing oxygen deficiency, electrical insulation is effected between plural burners and a device body and between the burners, and a frame rod is attached to an arbitrary burner.
CONSTITUTION: A specified combustion amount burner 3 and a variable combustion amount burner 5 are electrically insulated from a device body and the specified combustion amount burner 3 by means of insulating materials 11 and 12, respectively, such as insulators. In which case, even if flames 9 and 10 interfere with each other, since minus ion generated to the flame 10 of the variable combustion amount burner 3 is completely insulated, the ion is prevented from movement to both the specified combustion amount burner 3 and the device body. Thus, a current detected by a frame rod 6 is decided through combustion of only the specified combustion amount burner 3, i.e., is specified. This enables operation of a combustion shut off device at a specified decision level at a specified oxygen concentration time throughout a whole combustion amount variable range.
ISHIKURA NAOKI
YAMADA NORIKAZU
OOHASHI NORIYOSHI
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