Method for molding a plastic article of varied density
US5437823A · kind A · utility
Inventors
Key dates
| Filing date | Jun 23, 1993 |
| Grant date | Aug 1, 1995 |
| Priority date | — |
| Expiry date | Jun 23, 2013 |
Classification
- Technology area (CPC B)Performing Operations; Transporting
- CPC primaryB29C44/0407
- WIPO fieldOther special machines
- WIPO sectorMechanical engineering
Abstract
A method of molding a plastic part with a controlled density whereby a blowing agent is added to a plastic material and the material is injected into a mold cavity of a mold unit. The interior walls of the mold cavity are maintained at a temperature sufficient to prevent the outer skin of the forming plastic article from producing gas bubbles. The volume of the mold cavity is increased to allow bubbles to produce and uniformly distribute themselves throughout the mold cavity and then a recompression phase is instituted whereby the desired density of the finished plastic article is achieved without voids or aberrations appearing in the surface of the plastic article.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.