Process and apparatus for production of articles with selectively thinned portions using a multi-radius forming plug
US4883633A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Dec 24, 1987 |
| Grant date | Nov 28, 1989 |
| Priority date | — |
| Expiry date | Dec 24, 2007 |
Classification
- Technology area (CPC B)Performing Operations; Transporting
- CPC primaryB29C51/10
- WIPO fieldOther special machines
- WIPO sectorMechanical engineering
Abstract
This invention relates to a method and apparatus for making cupped articles from thermoplastic sheet or billets wherein the articles are formed with a bellows bottom which will displace inwardly when the internal pressure within the cup decreases. The invention specifically relates to an improvement upon the forming process which involves clamping a heated sheet or billet of a thermoplastic material in the solid phase state between a forming plug and a hollow mold having an end opening, moving the forming plug into the opening to carry the sheet into the mold, and introducing pressure fluid into the stressed portion of the sheet to form the article by making the sheet conformed to the shape of the hollow mold. The closed end of the hollow mold is improved by forming it with a flat central portion which has a tapered portion extending outwardly therefrom. The tapered portion tapers in the direction of the open end of the mold and ends in a ridge which extends away from the open end and vertically beyond the flat central portion. A second ridge extends beyond the first. The forming plug is improved in that it has inwardly tapering sides which terminate in a curved portion which itsel…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.