Press molding apparatus and press molding method

Abstract

A press molding apparatus includes upper and lower mother molds 102 and 104. Each of the mother molds 102 and 104 has four molding surfaces arranged in a single line and satisfies the relationship given by L×α×ΔT / t<0.0008, where L represents the length, t, the thickness, α, the thermal expansion coefficient, and ΔT, the temperature difference between both ends in the thickness direction during induction heating. The press molding apparatus may include a pressing mold set including upper mother molds 102a and 102b attached to a common fixed shaft 118 through upper supporting shafts 110a and 110b and lower mother molds 104a and 104b driven by a common drive shaft 120 through lower supporting shafts 112a and 112b. The upper mother molds 102a and 102b and the lower mother molds 104a and 104b are collectively heated by induction heating coils 122 and 124, respectively.

Description

BACKGROUND OF THE INVENTION [0001] This invention relates to a press molding apparatus and a press molding method for use in precision pressing in which an optical element is obtained by press molding a material, such as a preformed glass material in a heated and softened state and, in particular, to precision pressing in which no polishing is required after molding. [0002] Recently, in a field of production .of an optical element such as an optical lens, it is desired to obtain a high-accuracy lens shape without carrying out surface polishing. To this end, proposal is made of a method comprising the steps of preparing a pre-shaped glass material (preform), heating and softening the preform, and pressing the preform by a high-accuracy pressing surface (Japanese Unexamined Patent Publication JP 2001-10829 A). In particular, use is recently made of a mother mold having an elongated shape with a plurality of molding surfaces arranged in a single line so as to simultaneously press form ...

AI Technical Summary

Benefits of technology

This solution effectively suppresses mold warping, enhancing the dimensional accuracy and thickness uniformity of optical elements, allowing for high-accuracy production without the need for polishing, even when producing multiple elements simultaneously.

Problems solved by technology

However, such design of the mother mold is disadvantageous in the following respects.

This results in occurrence of tilt in molded products, such as optical lenses, and thickness deviation of the formed products.

Recently, the problem of warp of the mother mold becomes more and more serious.

If press molding is performed in the state where the upper and the lower molds are warped, defective molding may be caused and the upper or the lower mother mold 502 or 504 may be damaged.

If the required product specification is strict, a desired performance may not be achieved.

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