| 摘要 |
PURPOSE: A safety device is provided to improve safety of a heater by cutting off power supplied to the heater even if a magnetic switch is not operated when the heater is overheated. CONSTITUTION: A safety device of a heater comprises a magnetic switch(8) operated by the current applied through a first power supply line(4), a first safety device(10) installed in a part of the first power supply line to cut off the first power supply line upon overheating of a heater(106), and a second safety device(12) installed in a part of a second power supply line(6) to cut off the second power supply line upon overheating of the heater. The magnetic switch consists of an electromagnet(14), a contact point(16), and an elastic member(18). The first safety device is formed in the type of a thermostat. The second safety device is formed in the type of a fuse. In malfunction of the magnetic switch, the contact point is not separated from the second power supply line even if the first safety device is operated. Then, overcurrent is supplied to the heater and the heater is overheated. If overcurrent is applied to the heater through the second power supply line, a fuse of the second safety device is shorted to cut off the second power supply line. Then, power to the heater is cut off. Therefore, the heater is prevented from overheating. |
