| 摘要 |
PURPOSE:To prevent trouble due to lack of oxygen by a method wherein the opening and closing of a shutter are detected by a limit switch to alarm by an alarm buzzer upon poor ventilation. CONSTITUTION:The lower part of a connecting plate 5, attached to the terminal parts of sutter plates 3 so as to be capable of moving the shutter plates 3 simultaneously, is bent into L-shape contacted with the operating plate 7 of the limit switch 6. A thermal timer 8, connected in parallel to a fan motor 2 through the contact of the limit switch 6, eliminates the malfunction of the alarm buzzer 9 due to the unstability of motion of the limit switch 6 caused by the flattering of the shutter plates 3. In case the shutter plates 3 are not opened upon starting of the fan motor 2, the limit switch 6 is in the same condition as the stopped condition thereof, therefore, the contact put ON the circuit of the thermal timer 8. At this time, the switch 10 of the ventilating fan is being put ON, therefore, the thermal timer 8 is conducted and the contact 12 is put ON after a set time, thereby sounding the alarm buzzer 9.
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