Elastic Nonwoven Sheet Stretching With Wrinkle and Curl Control
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Solution Overview
Problem
Existing methods for imparting elasticity to webs, such as those used in disposable diapers, result in irregularities and wrinkles during stretching, leading to instability in transporting and processing the stretched web, including issues with curling and attachment.
Innovation Solution
A method involving a stretching apparatus with specific roll designs and a combination of heating and compressing processes to uniformly stretch and stabilize nonwoven fabrics, using a tooth/groove roll configuration and applying controlled tensile forces to prevent meandering and achieve uniform width and thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If incremental stretching is applied to impart elasticity to the web, then elasticity is achieved, but irregularities and wrinkles remain in the machine direction
Solution Approach 1:
The patent applies preliminary action by restraining peripheral edge portions before the stretching process begins. The restraining means (freely elastic deformable disks or continuous belts) are positioned and configured to prevent web contraction and sliding during the subsequent incremental stretching operation, thereby preventing wrinkle formation before it occurs
Solution Approach 2:
The patent applies local quality by applying different functions to different parts of the web. The peripheral edge portions are restrained by specialized means (disks or belts) while the central portion is stretched. This localized restraint approach ensures uniform stretching without causing irregularities in the restrained areas
2Strength
If the web is stretched to impart elasticity, then elasticized waist bands and leg bands are formed, but the stretched web curls up and becomes difficult to attach
Solution Approach 1:
The patent prevents curling by implementing restraint of peripheral edge portions before stretching. The freely elastic deformable disks or continuous belts are pre-positioned to maintain web flatness and prevent the stretched sections from curling up during subsequent transport and processing operations
Solution Approach 2:
The patent changes the physical state and mechanical properties of the web by applying controlled incremental stretching. The stretching process modifies the web's elasticity parameters while the restraining means control the geometric parameters (flatness, width) to prevent curling and maintain processability
3Manufacturing precision
If peripheral edge portions are restrained during stretching, then sliding and contraction are prevented, but the device complexity increases
Solution Approach 1:
The patent applies self-service through the use of freely elastic deformable disks that automatically adjust and restrain the web edges based on their own elastic properties. The continuous belts also self-adjust to maintain restraint during the stretching process, eliminating the need for complex external control mechanisms
Solution Approach 2:
The patent employs relatively simple restraining components (disks or belts) that can be easily replaced or adjusted. These components are designed to be simple in structure compared to complex mechanical restraint systems, reducing overall device complexity while maintaining effective control
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
The method ensures stable transportation and processing of the stretched nonwoven fabric by minimizing wrinkles and curling, allowing for consistent width, thickness, and strength, thereby facilitating subsequent steps like folding, cutting, and attachment.
Implementation Method 1
heating and compressing processes
Implementation Method 2
heating and compressing processes
Data Source
Figure 1~2(b)
Figure 3(a)~3(b)
Figure 4(a)~4(b)
AI summary
There is provided a method for producing a stretchable sheet that can uniform the shape, such as the width and thickness, and the strength, of a stretched nonwoven fabric. The method for producing a stretchable sheet according to the invention comprises a step of stretching a nonwoven fabric 7 in the cross-machine direction perpendicular to the machine direction in which the nonwoven fabric 7 is transported (3, 4) and a step of compressing the nonwoven fabric 7 stretched in the step of stretching the nonwoven fabric 7 (3, 4), in the thickness direction of the nonwoven fabric 7 (5, 6).