Anvil Roll Protrusion Area Rate Control for Ultrasonic Welding
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Solution Overview
Problem
Ultrasonic welding of elastic film stretchable structures in absorbent articles often results in welding defects due to thermal expansion differences in regions with varying area rates of protrusions on the anvil roll, leading to inconsistent clearance and bonding issues.
Innovation Solution
The method involves controlling the area rate changes of protrusions on the anvil roll to maintain a difference of 4.5% or less in the circumferential direction and 1.5% or less in the length direction, ensuring consistent thermal expansion and preventing welding defects by using multiple ultrasonic horns for each anvil roll and optimizing the melting points of the sheet layers and elastic film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If ultrasonic welding is used to bond sheet layers in regions with varying area rates of protrusions, then bonding efficiency is improved, but welding defects occur due to thermal expansion differences
Solution Approach 1:
The anvil roll is designed with regions having different area rates of protrusions to match the varying bonding requirements of different regions of the elastic film stretchable structure. This local differentiation allows optimized bonding in each region while controlling thermal expansion differences to prevent welding defects
Solution Approach 2:
The area rate of protrusions is controlled within specific ranges (30-70% in the first region, 10-50% in the second region) to balance bonding efficiency and thermal expansion. By adjusting these parameters, the patent achieves both high productivity and reliable welding quality
2Manufacturing precision
If the area rate of protrusions varies extensively to optimize bonding in different regions, then bonding performance is improved, but thermal expansion differences cause inconsistent clearance and bonding issues
Solution Approach 1:
The anvil roll is divided into multiple regions with different protrusion area rates, where the first region (30-70% area rate) provides strong bonding and the second region (10-50% area rate) allows elastic recovery. This local differentiation optimizes bonding performance while maintaining overall stability
Solution Approach 2:
The patent explicitly controls the area rates of protrusions to manage thermal expansion differences during ultrasonic welding. By keeping area rates within specific ranges and creating a gradual transition between regions, the patent minimizes clearance inconsistency and bonding defects caused by thermal expansion
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 prevents welding defects by minimizing thermal expansion differences, ensuring uniform bonding and maintaining the structural homogeneity and flexibility of the elastic film stretchable structure, particularly in absorbent articles like underpants-type disposable diapers.
Implementation Method 1
a bonding step of passing the first sheet layer, the second sheet layer, and the elastic film interposed therebetween in the stretched state, between an anvil roll having a plurality of protrusions arranged at intervals in a predetermined pattern on an outer peripheral surface, and at least one ultrasonic horn facing the outer peripheral surface of the anvil roll, and forming sheet bonded portions by welding the first sheet layer and the second sheet layer only at portions interposed between the plurality of protrusions and the ultrasonic horn
Implementation Method 2
Ultrasonic welding of elastic film stretchable structures in absorbent articles often results in welding defects due to thermal expansion differences in regions with varying area rates of protrusions on the anvil roll
Data Source
AI summary
Ultrasonic welding is performed by passing a first sheet layer, a second sheet layer, and an elastic film interposed therebetween in a stretched state in a machine direction between an anvil roll having a large number of protrusions and an ultrasonic horn. The anvil roll includes a region having the protrusions and in the region. A site, in which welding is performed by one ultrasonic horn, has a portion in which an area rate of the protrusions changes in a roll circumferential direction and a roll length direction. A difference between a maximum value and a minimum value in a change of the area rate of the protrusions in the roll circumferential direction is 4.5% or less, and a difference between a maximum value and a minimum value in a change of the area rate of the protrusions in the roll length direction is 1.5% or less.