Patent ID: 8806893
Filing Date: 2014-08-19
Classification: C03B,C03C,G11B

Abstract:
1. A manufacturing method of a glass blank for a magnetic disk including a pair of principal surfaces, the method comprising: a dropping process for dropping a lump of molten glass by cutting molten glass with cutting blades so that the lump of molten glass is separated from the molten glass and is out of contact with the molten glass as the lump falls along a dropping path; a pressing process for forming a sheet glass material by sandwiching the lump from both sides of the dropping path of the lump, at substantially the same time, with surfaces of the pair of dies facing together to catch the lump as the lump is falling along the dropping path, and performing press forming to the lump; and a temperature adjusting process for adjusting temperature of the lump during a period of time beginning at a time when the lump is dropped and ending at a time that the pair of dies press the lump in the pressing process such that the temperature adjusting process occurs while the lump is falling vertically along the dropping path and viscosity variation of the lump is reduced with respect to positions over the entirety of the lump in the pressing process.