Two-Ply Press Felt Structure for Uniform Pressure and Dewatering
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Solution Overview
Problem
Existing basic structures for fiber web production, such as press felts, face challenges in achieving desired properties like storage volume, uniformity, and production complexity, with circular-woven fabrics being complex and flat-woven fabrics having weak connection points.
Innovation Solution
A basic structure comprising two plies with different CD yarn diameters and densities, where the first ply has smaller CD yarns and higher density, forming a laminate with the second ply, allowing independent adaptation to requirements and improving pressure distribution, anchoring, and permeability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If circular-woven fabrics are used for basic structures, then tensile strength and uniformity are improved, but production complexity increases
Solution Approach 1:
The basic structure is divided into multiple plies (first ply and second ply) with different yarn configurations. The first ply uses CD yarns with smaller diameter and higher yarn density, while the second ply uses CD yarns with larger diameter and lower yarn density. This segmentation allows each ply to be produced independently using simpler flat-woven processes while achieving the desired overall properties through layering.
Solution Approach 2:
Different regions of the basic structure have different local properties through the use of plies with varying yarn diameters and densities. The first ply provides uniformity and strength through its high CD yarn density, while the second ply provides permeability and reduces marking through its lower CD yarn density. This local differentiation resolves the contradiction by allowing simple production processes to create complex functional properties.
2Productivity
If flat-woven fabrics are used for basic structures, then production speed and cost are improved, but connection points create weak spots and marks
Solution Approach 1:
The basic structure is segmented into multiple plies where the first ply consists of continuous CD yarns without connection points, eliminating the weak spots and marks associated with flat-woven connection points. The second ply provides additional functionality while the first ply ensures uniformity and strength through its continuous yarn structure.
Solution Approach 2:
The basic structure combines different types of yarns (CD yarns with different diameters and densities) in multiple plies to create a composite material that achieves both the advantages of flat-woven fabrics (production speed, cost) and circular-woven fabrics (uniformity, strength without marks).
3Device complexity
If single ply basic structures are used, then production simplicity is improved, but storage volume properties cannot be achieved
Solution Approach 1:
The basic structure transitions from a single-ply two-dimensional structure to a multi-ply three-dimensional structure. By adding the second ply above the first ply, the basic structure achieves increased storage volume and complex functional properties while maintaining production simplicity through the use of standard flat-woven processes for each individual ply.
Data Source
AI summary
A basic structure for a covering, in particular a press felt for a machine for producing a fiber web, includes a first ply having first MD yarns and first CD yarns, and a second ply having second MD yarns and second CD yarns. The first ply is disposed above the second ply. The first CD yarns have a smaller diameter than the second CD yarns, and the yarn density of the first CD yarns is greater than the yarn density of the second CD yarns.