Method and device for mould pressing glass products

Abstract

This method is composed of a stage for supplying molten glass on the forming faces of a lower die, a stage for controlling the glass temp. so that the temp. of the inside of glass is brought close to that of the peripheral part and a stage for pressing the glass by the forming faces of the upper die and lower die, when viscosity of the temp.-controlled glass is within 103.5-106.5 poise. Since the temp. of the inside of glass is brought close to that of the peripheral part and the glass is pressed with a relatively high viscosity, the heat contraction quantity of the pressed glass is made small, and the difference in heat contraction quantity between the inside and peripheral part of the glass is decreased. Consequently, the generation of shrinks on the glass surface is reduced.

Description

technical field [0001] The present invention relates to a method and apparatus for extrusion molding glass articles suitable for molding optical lens blanks, in particular a so-called direct extrusion system in which molten glass is fed into a mould. , extruded in the mold. Background technique [0002] As a method of molding unfinished glass products (hereinafter referred to as lens blanks), that is, before grinding or polishing into a state before finishing or final glass products such as optical lenses, people widely use productivity Very tall direct extrusion system. In this direct extrusion system, glass material is melted into molten glass in a furnace. An appropriate amount of molten glass is cut off with a cutting tool such as a shear and fed into the lower die (lower mold box). The molten glass fed into the lower die forms a generally marble-like gob of glass under the action of its surface tension. The lower mold with the glass gob thereon is conveyed to the po...

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Problems solved by technology

However, none of the disclosures is about a technology that effectively reduces the difference in temperature between the inside and outside of the molten glass that causes dents to occur.

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