Abstract: The invention provides a continuous paperboard sheet adapted to be slit longitudinally into a plurality of continuous paperboard plies, and to improved paperboard plies for forming single-layer, paperboard tubes. The paperboard sheet has a substantially constant width and includes a plurality of thick longitudinal sections and a plurality of thin longitudinal sections. The thick and thin sections are arranged in alternating relation across the width of the paperboard sheet. The sheet is slit longitudinally along the thin sections to provide a plurality of tube-forming paperboard plies.

Abstract: A single-ply wound paperboard tube is disclosed as is its forming method. The method comprises applying an adhesive to a paperboard ply having relatively thin longitudinal edges and a relatively thick central portion therebetween, then spirally winding the ply about a mandrel in edge-overlapping relation. Preferably, the thinned edges and the thick central portion of the ply share a common face, and the ply is preferably steam-conditioned to raise its temperature and its moisture content prior to the application of the adhesive.

Abstract: The invention provides a continuous paperboard sheet adapted to be slit longitudinally into a plurality of continuous paperboard plies, and to improved paperboard plies for forming single-layer, paperboard tubes. The paperboard sheet has a substantially constant width and includes a plurality of thick longitudinal sections and a plurality of thin longitudinal sections. The thick and thin sections are arranged in alternating relation across the width of the paperboard sheet. The sheet is slit longitudinally along the thin sections to provide a plurality of tube-forming paperboard plies.

Abstract: The invention provides a method and apparatus for the manufacture of helically wound paperboard tubes having a highly uniform outside diameter. The method of the invention involves the application of controlled compressive force to at least one of the paperboard plies fed to a helical winding operation in order to control the thickness of the ply or plies and thereby control the outside diameter of the helically wound tube. In one preferred apparatus embodiment of the invention, the compressive force applied to the paperboard ply is applied via a pair of cooperating compression rolls. The nip between the two cooperating rolls is controllably varied by mounting one of the rolls for rotation about a shaft which is rotatable about an eccentric axis which is parallel to and offset from the axis of rotation of the roll. The rotation of the shaft thus causes the roll to move toward or away from the other cooperating roll and thereby varies the nip spacing between the rolls.