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.

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.

Abstract: In the fabrication of a resistance heater for a carton for packaging a pizza, an aluminum metallized sheet is adhered to a paperboard panel, a generally U-shaped strip of arc-sprayed zinc is applied to three edge portions of the upwardly facing electrically conductive metal layer of the metallized sheet, the interconnecting portion of the U-shaped strip and the immediately underlying metal layer are severed, and the metal layer is severed along a line extending adjacent the same interconnecting portion to the side thereof enclosed by the U-shaped strip, so that each of the severed sections of the interconnecting portion serves as a terminal for a corresponding leg portion of the U-shaped strip comprising the electrodes for the intermediate region of the metallized sheet.