Method for forming a container with corrugated wall and rolled lip

Abstract

A method of forming a paper container uses a three-ply corrugated material having at an outer sheet of paper that may be stretched circumferentially to permit subsequent rolling of the corrugated material about a mandrel and an inner sheet of paper that can be stretched circumferentially to assist in rolling the lip of the cup and / or attaching the bottom to the cup. An extensible paper having two axes of extension of over four percent can be used for one or both of the paper layers.

Description

CROSS REFERENCE TO RELATED APPLICATIONS Field of the Invention Cross-Reference to Related Applications [0001] The invention relates generally to paper containers and in particular to a container having an insulating wall of corrugated paper. BACKGROUND OF THE INVENTION [0002] Disposable cups for holding hot beverages may be constructed of expanded polystyrene which provides a cup of relatively low cost with walls having good thermal insulation. The insulating properties of the outer walls of the cup allow the cup to be comfortably held despite the high temperature of its contents. The disadvantages of polystyrene are that it is not biodegradable, readily recycled or microwavable. [0003] In contrast, paper cups are both recyclable and biodegradable, but such cups, using a single sheet of paper for their outer walls, provide little thermal insulation. It has therefore been proposed to construct the outer wall of a paper cup of multi-ply corrugated paper material. The air trapped betwe...

AI Technical Summary

Benefits of technology

[0011] The present inventor has determined that the use of a paper with a high degree of extension in machine direction on the inside of the cup reduces tearing in the rim even though the rim is rolled along the cross direction. This solution appears to work because the dominant factor in tearing is not the stretching the paper in a radial direction about the rim, as one might expect, but the stretching of the paper along the circumference of the rim. Use of an expandable material for the center corrugated layer appears to provide additional benefits in this regard. A combination of an outer creped ply and an inner ply of extensible Kraft appears to be particularly advantageous.

[0013] Thus, it is one object of at least one embodiment of the invention to provide a corrugated paperboard for the manufacture of containers that allows for the improved formation of a rolled lip.

[0015] It is yet another object of least one embodiment of the invention to provide a material that can be used on standard cup making equipment while resisting tearing of the lip.

[0020] The center corrugated paper layer may also provides at least four percent extensibility along a machine direction aligned with the machine directions of the first outer paper layer and second outer paper layer.

[0021] It is an object of at least one embodiment of the invention to provide an extensible intermediate layer between the outer paper plies that is believed to moderate stress between the plies to provide tear resistance.

[0024] One or more of the paper layers may also provide at least four percent extensibility along a cross direction.

Problems solved by technology

The disadvantages of polystyrene are that it is not biodegradable, readily recycled or microwavable.

In contrast, paper cups are both recyclable and biodegradable, but such cups, using a single sheet of paper for their outer walls, provide little thermal insulation.

Separately cutting and handling the multiple plies needed to form a multi-ply cup with a corrugated inner layer and assembling the plies into a single corrugated container requires specialized machinery, limiting the commercial feasibility of this approach.

The rubber belt is compacted lengthwise (in the machine direction), which affects the web between it and the cylinder in the same way thus causing compacting and crimping of the fibers in the web longitudinally.

Despite the generally high extensibility of standard paper in the cross direction, small tears can form in the rim of the cup when the cup is formed on standard cup machinery.

Images