| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a deciding unit which detects suitable casting timing. SOLUTION: Metallic material is held into the inner part of a vessel 4 for casting and this vessel 4 for casting is heated by a high frequency induction heating coil 10 through an inverter 10 with high frequency signal modulated through a low frequency signal generated by a low frequency oscillator 24. Light beam emitted from the metallic material in the vessel 2 for casting, is received by a light receiver 30 and a received light signal is generated. A high frequency component based on the sudden change of the received light signal caused by the molten metal 8, is extracted by a low frequency cut-off filter 34. When the output signal in the low frequency cut-off filter 34 exceeds a reference signal, a voltage comparator 40 generates an output signal, and when this output signal is continuously output for a fixed time, the casting instruction signal is generated through a timer 43.</p> |
