Method for injection molding of weld line free thermoplastic articles such as ophthalmic lenses
US6576162B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Apr 30, 2001 |
| Grant date | Jun 10, 2003 |
| Priority date | — |
| Expiry date | Sep 6, 2021 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10S425/808
- WIPO fieldOther special machines
- WIPO sectorMechanical engineering
Abstract
Disclosed is an injection molding method. The method comprises injecting a melt of thermoplastic material at a temperature higher than the glass transition temperature (Tg) of the thermoplastic material in a molding cavity defined by a two-piece mold insert. The article is recovered after cooling and disassembling of the two piece mold insert. Each of the two pieces of the mold insert comprise at least one portion partly defining the mold cavity which is made of a material or combination of materials, other than glass, the thermal diffusivity &agr; of which fulfills the condition: 1<&agr;/&agr;g<11, wherein &agr;g is the thermal diffusivity of a borosilicate glass and is equal to 6.20×10−7 m2 s−1. The portion is at least 1 mm thick. The injection molding method can be used to form weld free minus lenses.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.