Apertured Web Stretching via Segmented Rotary Knife Rolls
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Solution Overview
Problem
Existing methods struggle to produce apertured webs with closely-spaced, wider apertures in the cross-machine direction, leading to issues like tearing and low open area, and fail to create registered corrugated patterns with alternating ridges and grooves, which are essential for stronger and more functional web materials.
Innovation Solution
The use of intermeshing rolls with specific tooth geometries and configurations that apertures and stretch the web in a single process step, creating discrete, closely-spaced apertures with larger widths in the cross-machine direction and incorporating alternating ridges and grooves, ensuring apertures are located within the grooves, thereby enhancing web strength and functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If activation teeth with very small included angle are used to space aperture rows close together, then aperture row spacing is improved, but aperture width in cross-machine direction deteriorates
Solution Approach 1:
The activation tooth is divided into multiple segments or elements arranged in a specific pattern on the roll surface. This segmentation allows the tooth to create closely-spaced aperture rows while maintaining sufficient aperture width by distributing the deformation across multiple contact points rather than relying on a single narrow tooth geometry.
Solution Approach 2:
The activation teeth are designed with asymmetric geometry where the included angle varies across different portions of the tooth structure. This asymmetric design enables the tooth to produce different aperture dimensions in machine direction versus cross-machine direction, achieving close row spacing while preserving adequate aperture width through differential deformation control.
2Length of moving object
If activation teeth with very small included angle are used, then aperture row spacing is improved, but web strength deteriorates due to slit-like appearance and stress concentrations
Solution Approach 1:
By segmenting the activation tooth structure and arranging multiple tooth elements in specific patterns, the web material experiences distributed stress during aperturing rather than concentrated stress at single points. This segmentation prevents the formation of slit-like apertures that create stress concentrations, thereby maintaining web strength while achieving close aperture row spacing.
Solution Approach 2:
The activation teeth are designed with curved or rounded profiles rather than sharp angular geometries. This curvature in the tooth design produces rounded aperture shapes instead of slit-like openings, eliminating stress concentration points and improving web strength while still enabling closely-spaced aperture rows through proper tooth arrangement.
3Length of moving object
If post ring-rolling stretching is applied to apertured web, then web stretching is improved, but aperture alignment deteriorates creating alternating rows of aperture sizes
Solution Approach 1:
The aperturing and stretching functions are merged into a single integrated process step by combining activation teeth with ring roll stretching elements. This integration ensures that apertures are created and stretched simultaneously in a registered manner, preventing misalignment and alternating aperture size patterns that occur when these operations are performed separately.
Solution Approach 2:
The apertures are preliminarily formed with the correct geometry and positioning by the activation teeth before the web enters the ring roll stretching section. This preliminary action establishes proper aperture alignment that is maintained through the subsequent stretching process, preventing the development of alternating aperture size patterns.
4Length of moving object
If post ring-rolling stretching is applied, then web stretching is improved, but web strength deteriorates making web more prone to tearing
Solution Approach 1:
By merging aperturing and stretching into a single synchronized process, the web material undergoes controlled deformation where apertures are created and stretched simultaneously. This integrated approach distributes stress more evenly throughout the web structure compared to sequential processing, maintaining web strength while achieving the desired stretching effect and reducing susceptibility to tearing.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach results in apertured webs with higher open areas, lower aspect ratios, and improved strength in the cross-machine direction, along with a textured appearance that enhances fluid handling and breathability, while maintaining the web's integrity and reducing fluid retention.
Implementation Method 1
two intermeshing rolls... each having a plurality of circumferential ridges and grooves... wherein when the web is fed into the nip, the top of at least some of the ridges on the first roll extend inward toward the axis of the second roll to a depth beyond the top of at least some of the second ridges on the second roll
Implementation Method 2
The ridges and grooves extend around the circumference of the roll... apertured and stretched in the cross-machine direction by the intermeshing rolls
Data Source
AI summary
Apparatuses and processes for aperturing and stretching a web are disclosed. In one embodiment, the method involves feeding a web into a nip that is formed between at least one pair of intermeshing rolls. The first roll is a raised ridge rotary knife aperturing roll and the second roll is a ring roll; both rolls comprise ridges and grooves. The first roll comprises a plurality of spaced-apart teeth extending outwardly from the top surface of the ridges, said teeth having tips, wherein the top surface of said ridges are disposed between the tips of said teeth and the bottom surface of said grooves. These apparatuses and processes enable a web to be formed which comprises apertures having greater open area than previously achievable with traditional processes and apparatuses.