Rigid paperboard container and method and apparatus for producing same
US4609140A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Aug 12, 1985 |
| Grant date | Sep 2, 1986 |
| Priority date | — |
| Expiry date | Aug 12, 2005 |
Classification
- Technology area (CPC B)Performing Operations; Transporting
- CPC primaryB31B50/592
- WIPO fieldHandling
- WIPO sectorMechanical engineering
Abstract
A pressed paperboard container (10) is formed having a bottom wall (11), an upturned side wall (12, and an overturned rim (13) extending from the side wall which is denser and thinner than the rest of the container. The container is formed by pressing a flat circular blank (27) between upper and lower dies (25, 26) having die surfaces (31, 32, 38, 39, 40) which shape the blank into proper form, and the surfaces of the dies (25, 26) at the rim area (13) of the container are shaped to exert extremely high compressive stresses on the rim, particularly at the folded areas (20) formed in the rim during initial shaping of the container. The high compressive stresses applied to the rim area, along with proper moisture levels maintained in the paperboard and the heating of the paperboard by the heated dies, causes the paperboard in the rim area to deform plastically, densify, and fill in voids created as the blank was pressed into the container form. The integral, dense rim is a rigid structure which provides resistance to bending to the entire container.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.