Absorbent Sheet Ply Bonding via Knurled Cylinders
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Solution Overview
Problem
Existing methods for combining cellulose wadding plies, such as knurling and embossing, face issues like delamination, reduced softness, increased rigidity, and wear of equipment, leading to inconsistent product quality and complexity in manufacturing.
Innovation Solution
A method involving cylindrical steel elements where one element is smooth and the other has relief elements, with a hardness difference, allowing for pressure association of plies under specific pressure, reducing wear and enabling high-speed production with varied and visible embossing patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If plies are associated by chemical bonding with glue, then bonding strength is improved, but device complexity and manufacturing cost increase due to additional equipment and glue application systems
Solution Approach 1:
The invention extracts and eliminates the glue application system from the manufacturing process. By using mechanical interlocking through knurling patterns directly on the cylindrical elements, the chemical bonding step is removed entirely, simplifying the device while maintaining bonding strength through physical interlocking of the plies.
Solution Approach 2:
The invention replaces the chemical bonding system (glue application equipment) with a mechanical interlocking system. The knurling patterns on cylindrical elements create physical interlocking structures that bond plies mechanically rather than chemically, eliminating the need for glue application equipment.
2Strength
If glue is used for bonding plies, then bonding strength is improved, but product softness deteriorates due to glue presence and rigidity increases undesirably
Solution Approach 1:
The invention extracts and removes glue from the final product. By using mechanical interlocking through knurling, the bonding is achieved without any chemical adhesive, thereby preserving the natural softness of the cellulose wadding plies and avoiding the unwanted rigidity that glue would introduce.
Solution Approach 2:
The invention substitutes chemical bonding with mechanical interlocking. The knurling patterns create physical interlocking structures that provide bonding strength without the need for glue, thereby maintaining the softness characteristics of the original plies.
3Device complexity
If knurling is used to associate plies, then equipment complexity is reduced, but manufacturing precision deteriorates due to delamination in non-knurled areas and limited pattern coverage
Solution Approach 1:
The invention makes the cylindrical elements universally applicable for bonding the entire width of the plies. By using a single continuous cylindrical element with knurling patterns that wrap around the entire circumference, the system achieves uniform bonding across the full width of the material, eliminating the limited coverage problem of segmented knurling wheels.
Solution Approach 2:
The invention uses cylindrical (curved) elements instead of flat or segmented wheels. The knurling patterns are formed on the curved surface of the cylinder and wrap continuously around it, ensuring uniform contact and bonding across the entire width of the plies as the cylinder rotates, thereby achieving consistent manufacturing precision.
4Shape
If embossing is performed on plies, then product aesthetics and thickness are improved, but strength deteriorates due to loosening of interfiber bonds
Solution Approach 1:
The invention merges the embossing function with the bonding function into a single operation. The knurling patterns on the cylindrical elements simultaneously create the embossed aesthetic patterns and provide the mechanical interlocking structures needed for bonding, eliminating the need for separate embossing steps that would weaken the fibers.
Solution Approach 2:
The invention performs the bonding action preliminarily during the embossing process itself. As the plies pass between the knurled cylindrical elements, the mechanical interlocking occurs at the same time as the embossing pattern is created, ensuring that the bonding strength is established before any subsequent processing that might further weaken the fibers.
Data Source
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AI summary
The invention relates to a process for manufacturing an absorbent sheet comprising at least two plies of cellulose wadding, consisting in combining said plies under pressure by passing between two steel cylindrical components, the first (1) being smooth on the outside and the second (2) being equipped with raised components on the outside and the hardness of the first cylindrical component being lower than that of the second cylindrical component. According to the invention, the first cylindrical component (1) has a treated hardened surface layer (11) and a deformable underlayer (12); the second cylindrical component has a hardened outer surface, and the sheet, when it passes between the two cylindrical components (1, 2), is compressed at a specific pressure between 40 and 250 N/mm2. Another subject of the invention is an assembly of steel cylindrical components (1, 2) intended for the manufacture of multiply absorbent sheets.