PURPOSE: To exactly measure total melt weight by connecting the lower end of a movable cylinder supported vertically movably on the inside of the inner cylinder with the mouth of a vessel during the descend by the self-weight.

CONSTITUTION: When a space 5a of a bellows 5 is depressurized and compressed with a pressurized air supply means 8, an inner cylinder 6 descends and a movable cylinder 7 also descends and an inside flange fitting part 6b where the lower end part 7b touches the mouth 3a of the vessel 3 separates from an outside flange fitting part 7a and stops in the middle position to the lower end 7b. A down flow nozzle 2 is heated with a high frequency coil 2a and so the fluidity of inside melt X is raised. The melt X flows down out of the nozzle 2, gradually fills the vessel 3 inside and the vessel is thermally expanded. By the elevation of the cylinder 7, thrust force is absorbed, which does not acts on a load cell 12 and thus exact measurement of the weight of the filled melt X is possible.