| 摘要 |
PURPOSE:To make it possible to positively detect the existence or absence of flame by detecting a draft air current of a draft pipe heated by flame. CONSTITUTION:A gas flows into the device through an inlet 5, passing through a manual gas cock 6 and a safety valve 7 and burning in the burner 8. A flame 9 heats the upper end 11 of the draft pipe 10 to generate a draft air current within the pipe 10. Reference numeral 12 designates an air speed sensor provided in the lower end of the drive pipe. The air speed sensor 12 guides a signal indicating the existence or absense of the draft air current to a controller 13. Although the temperature of the sensor 12 rises up by a electric current (i), the sensor 12 is cooled by the draft air current if there is a flame 9 in the burner 8 upon this occasion. Accordingly, since the sensor 12 does not exceed a predetermined temperature, an electromagnetic valve 9 continues to open. When the burner 8 is not ignited yet, the draft air current is not generated. Hence, the temperature of the sensor 12 continues to rise up, whereby a comparator 20 produces a low output and a transistor 21 is turned OFF. Therefore, the electromagnetic valve 7 is closed to prevent the flow of the gas. |
