PURPOSE: To improve the heat retaining properties, measuring accuracy of viscosity and operating economy of a heating furnace by fitting a plug having a loose fitting hole for a vibrating piece into an insertion port of a sample container of the heating furnace, and providing the loose fitting hole with a furnace lid.
CONSTITUTION: A though-hole 22 is formed in an up-and-down direction of a main body 21 of an electric furnace. A core pipe 23 is fitted in the hole 22. Moreover, a plug 26 is detachably fitted in the hole 22. The plug 26 has a square hole 26a allowing a vibrating piece 3 to pass therethrough at the center in a diametrical direction from an upper opening of the pipe 23. The upper opening of the plug 26 is closed by a furnace lid 27 which is freely opened. Even when the lid 27 is closed, there are secured a loose fitting hole into which a vibrating rod 4 is loosely fitted, and an insertion hole for inserting a protecting pipe having a wire of a thermocouple inserted. Therefore, while the temperature of a melt 1 in a crucible 2 is measured, the radiation from the melt 1 can be shut off by the plug 26 and lid 27, with improving the heat retaining properties. As a result, the temperature distribution of the melt 1 can be maintained good, so that the measuring accuracy of viscosity is improved. In addition, the power consumption is saved.
OGAWA KATSUMI
NIMURA YOSHITAKA
UMEDA NORIHIKO
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