US Patent 7293430 Press molding apparatus and press molding method of optical element

A press molding apparatus includes upper and lower molding dies each having a molding surface facing each other, and a driving device which moves at least one of the upper and lower molding dies in a vertical direction so that the upper and lower molding dies are opened and closed. The driving device includes a main shaft which supports the at least one of the upper and lower molding dies, an ascending and descending member which, while supporting the main shaft, ascends and descends, a plurality of screw shafts which is located eccentrically from an axis line of the main shaft, and engages a plurality of screws formed in the ascending and descending member in order to move up and down the ascending and descending member, a driver which synchronously rotates each of the screw shafts, and a controller which controls the driver.