Method for controlling skin thickness of plastic article made with controlled density
US6129870A · kind A · utility
Inventor
Key dates
| Filing date | Oct 16, 1997 |
| Grant date | Oct 10, 2000 |
| Priority date | — |
| Expiry date | Oct 16, 2017 |
Classification
- Technology area (CPC B)Performing Operations; Transporting
- CPC primaryB29C44/60
- WIPO fieldOther special machines
- WIPO sectorMechanical engineering
Abstract
A method of molding a plastic with a foamed interior and a dense outer skin of a desired thickness, whereby a blowing agent is mixed with a plastic material and the mixture is injected, under pressure, into a mold cavity of a mold unit. The mixture is allowed to cool along the molding surfaces of the mold cavity for a determined amount of time. The pressure is released and the mold cavity expanded to allow the blowing agent to foam the interior of the plastic article. The molding cavity is then compressed to achieve the desired dimensions for the plastic article, and to give the interior a uniform cellular structure. Control over the timing of the expansion of the mold cavity, the injection temperature, the rate of injection of the mixture, the rate at which the cavity is expanded and compressed, and the timing of the compression of the mold cavity allow a skin of desired thickness to be formed on the plastic article.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.