Importance

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Abstract

A system for curling turned-in lips about the open mouths of thin walled, stacked, thermoplastic containers, having brims which extend in a return direction axially, utilizes a plurality of externally helically grooved, tubular, thermally conductive, synchronously rotated rollers equiradially spaced from a common central axis to define an annular passageway between them through which a stack of the containers pass with the brim of the containers simultaneously engaged in the grooves of the rollers. While the brims are being heated radiantly and via conduction substantially to the critical forming temperature, the brims are engaged in the transport portions of the grooves, but the peripheral side wall portions of the container are not contacted. Then the peripheral side wall portions of the containers are engaged by land portions on the rollers which maintain a controlled radial spacing between the side wall portions of the containers and the brims, and axial pressure is exerted on the brims to turn them radially inwardly in a progressive manner. Thereafter, the formed brims remain engaged in the roller grooves, with the peripheral side wall portions of the containers remaining engaged with land portions of the rollers while heat is removed from the side wall portions of the containers and the brims during continued axial transport of the containers through a cooling zone.

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First Claim