| 摘要 |
PURPOSE:To heat the raw material metal in the vicinity of the top portion of a needlelike member locally and efficiently by heightening the electric resistance of a part of the heater arranged in a reservior, the heater located in the lower portion of the reservoir. CONSTITUTION:When the electric source 10 is switched on the heating current flows to the reservoir 1 from the needlelike member 40 through the raw material metal 3 stored in the bottom of the reservoir 1, and in this circuit the sectional area of the heater portion 4d of the needlelike member 40 is made small so that the electric resistance of this portion becomes high. Therefore, the heat amount generated in the supporting portion 4c of the said member 40 or in the reservoir 1 is small and the most of the electric power supplied from the heating source 40 is transformed to the heat energy in the heater portion 4d. Thus the temperature of the vicinity of the top portion 4e of the needlelike member 40 can be made higher to improve the heating efficiency.
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