Method for cold-forming plastic sheet
US4071598A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Feb 23, 1977 |
| Grant date | Jan 31, 1978 |
| Priority date | — |
| Expiry date | Feb 23, 1997 |
Classification
- Technology area (CPC B)Performing Operations; Transporting
- CPC primaryB29C66/1122
- WIPO fieldOther special machines
- WIPO sectorMechanical engineering
Abstract
A method of cold-forming a thermoplastic sheet to provide a circular container part such as a lid or dish comprising the steps of engaging a sheet of thermoplastic material between opposing concentric die members, drawing the sheet around the circular edge of one of the die members to provide a concentric central portion and a concentric annular depending skirt having a proximal edge adjacent the central portion, an intermediate portion, and a distal free edge, provide an annular void in the die members adjacent the skirt, then moving the free edge toward the proximal edge while holding the proximal edge to buckle the said intermediate portion into the void. In the apparatus, the void has a tapered surface inclining radially outwardly and axially toward the proximal edge to hold the free edge radially inwardly, thereby to permit the intermediate portion to buckle outwardly into the void.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.