Molding arrangement to achieve short mold cycle time

Details Molding arrangement to achieve short mold cycle time Molding arrangement to achieve short mold cycle time

1995-09-29

1997-12-30

Davis, Robert

Plastic article or earthenware shaping or treating: apparatus

Female mold and charger to supply fluent stock under...

With means to heat or cool

2491141, 249116, 264 25, 264225, 425552, 425556, 425588, 425808, B29C 3338, B29C 4573

Patent

active

057027358

ABSTRACT:
An apparatus for molding polystyrene mold halves which are used, for subsequent molding of a soft contact lens. The apparatus is designed with superior heat conduction capacity so as to minimize the molding cycle time, while simultaneously producing uniformly precise and accurate optical quality surfaces. Molten polystyrene is provided via a hot runner system to a plurality of mold cavities. In a specific variation, the convex surface provides the optical quality surface to the concave surface of the mold half produced thereby. The structural element which defines the convex surface includes a hollow cylindrical bushing and a removable power insert mounted therein, which may be changed so that the prescription strength of the contact lens to be formed by the mold may be varied. In a first embodiment, the power insert includes only a convex surface at its operational end. In a second embodiment, the power insert includes an annular flat surface surrounding the convex surface, defining at the junction therebetween a discontinuity of curvature, which imparts a sharp edge to the mold half formed thereby. The power insert may be constructed of pure steel, or alternatively, it may be made of brass, copper chromium, or cobalt-nickel alloyed martensitic steel. The power insert may be coated with a surface layer of nickel phosphor or silicone oxide, or chrome nitride. These layers may be turned to their proper thicknesses and dimensions by diamond cutters, and they may be thermally hardened.

REFERENCES:
patent: 4540534 (1985-09-01), Grendol
patent: 4681295 (1987-07-01), Haardt et al.
patent: 5376317 (1994-12-01), Maus et al.
patent: 5388803 (1995-02-01), Baumgartner et al.
patent: 5541678 (1996-07-01), Awanohara et al.
patent: 5545366 (1996-08-01), Lust et al.
Abstract of Japanese reference 63-290231, Feb. 1989.

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