Method for fluid compression of injection molded plastic material
US5344596A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Oct 15, 1992 |
| Grant date | Sep 6, 1994 |
| Priority date | — |
| Expiry date | Oct 15, 2012 |
Classification
- Technology area (CPC B)Performing Operations; Transporting
- CPC primaryB29C2045/1741
- WIPO fieldOther special machines
- WIPO sectorMechanical engineering
Abstract
A mold apparatus and method is used to form a solid injection molded plastic part having no internal voids, a Class A finish, a sink-free exterior appearance surface, and unevenly distributed structural detail extending from the opposite surface, the detail including free-standing reinforcement ribs, attachment bosses, and the like. In the method the mold portions of the mold apparatus are closed, charges of molten thermoplastic and pressurized gas are sequentially injected into a mold cavity defining the shape of the desired part, and the mold portions are sequentially separated and closed. The pressurized gas forces the hot plastic away from one mold half and against the other mold half, and separation of the mold portions ensures uniform distribution of the pressurized gas behind the hot plastic, which pressure is maintained during cooling. Depending on the application, the plastic completely packs the cavity, fills but does not pack the cavity, and the mating faces can be abutted or maintained partially separated when the mold portions reclosed. A gas seal is formed by the plastic to prevent gas in the mold cavity from reaching the finished exterior surface of the part during s…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.