Zoned stretching of a web

Abstract

An apparatus and methods for stretching one or more zones of an anisotropic web and anisotropic webs including one or more stretched zones is provided. Each of the stretched zones in the web is stretched in the cross-web direction, i.e., the direction transverse to the down-web direction. The stretching can be performed continuously as the web is advancing through the apparatus in the down-web direction. The method for stretching an extensible web in the cross direction generally is practiced on a substantially continuous, extensible anisotropic web. The cross web stretching occurs in an orientation zone established by an orientation unit. The orientation unit moves the web out of the plane of the web where the web is under tension, but without any side restraints. The web moves over the orientation unit where the degree of orientation is proportional to the cross direction displacement of a portion of the web by the orientation unit. The anisotropic web has a tensile strength in the downweb direction greater than the cross direction such that the web is preferentially displaced in the cross web direction by the orientation unit. This can be a downweb direction tensile strength at least 50 percent greater than the cross web direction.

Description

FIELD OF THE INVENTION [0001] The present invention relates to the field of webs, web processing methods, and web processing apparatus. More particularly, the present invention provides apparatus and methods for stretching one or more zones of a web in the cross-web direction and webs so stretched. BACKGROUND [0002] It is desirable in many instances to stretch a web in the cross-web direction during processing. For example, webs including layers of inelastic materials, e.g., nonwoven webs, laminated or otherwise attached to elastic layers while the elastic is not extended typically require stretching to impart elasticity to the web. The web is stretched so that the inelastic layers, or bonds within the inelastic layer or layers, are broken or otherwise disrupted allowing the elastic to freely stretch which leaves the stretched web laminate elastic. Such stretching to impart elasticity to a web is commonly referred to as “activation” of the web (with the elasticity of the web being “...

AI Technical Summary

Benefits of technology

[0005] The present invention provides apparatus and methods for stretching one or more zones of an anisotropic web and anisotropic webs including one or more stretched zones. Each of the stretched zones in the web is stretched in the cross-web direction, i.e., the direction transverse to the down-web direction. The stretching can be performed continuously as the web is advancing through the apparatus in the down-web direction.

[0006] The method for stretching an extensible web in the cross direction generally is practiced on a substantially continuous, extensible anisotropic web. The web is traveling in a downweb direction at a first speed under tension in the web plane. The extensible anisotropic web has a width and substantially

Problems solved by technology

Although tentering does provide the ability to vary the amount of strain induced in the web, it also suffers from a number of disadvantages.

For example, the edges of the web must often be discarded after tentering due to damage or inconsistent strain in the web at the edges.

Another potential disadvantage is that it may be difficult or impossible to induce strain into selected portions or zones of a web using tentering.

Further, tentering equipment can be both costly, complex, and may require significant amounts of floor space to operate as the web expands in the cross direction during the process.

However ring rolling teeth grip the web and this contact of the web by the ring rolling apparatus can tear the web and undesirably affect the web's appearance.

The amount of strain that can be induced in a web using ring rolling is limited by the specific ring rolls used.

This is of course costly and inflexible.

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