Double Loop Seam for Papermaking Fabric Strength
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Solution Overview
Problem
Existing seam constructions in papermaking fabrics are weak, prone to hydraulic and topographical marking, and have low tensile strength due to excessive bending of MD-yarns and increased spacing between loops, which affects the integrity and performance of the fabric in papermaking machines.
Innovation Solution
A papermaking fabric with a single layer weave construction featuring multiple pairs of MD-yarns interwoven with CD-yarns in a repeat pattern, forming additional seaming loops at the widthwise edges to enhance seam strength and abrasion resistance, with increased material distribution in the seam area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If MD-yarns are woven back into the weave path of adjacent MD-yarns to form seam loops, then the seam can be formed to join fabric ends, but the extreme bending of MD-yarns causes increased strain, loop tilting, and increased spacing between loops which reduces tensile strength and increases marking
Solution Approach 1:
The invention divides the seam structure into multiple independent loops formed by separate MD-yarns instead of having yarns weave back into each other. Each loop is formed by its own MD-yarn passing beyond the adjacent yarn and forming a distinct loop, which then interdigitates with loops from the opposite fabric end. This segmentation eliminates the extreme bending and strain issues while maintaining seam integrity.
Solution Approach 2:
The invention changes the seam formation approach from a two-dimensional weaving-back pattern to a three-dimensional interdigitated loop structure. The loops extend beyond the fabric plane and intermesh with loops from the opposite end, creating a tubular passage that accommodates the pintle wire. This dimensional change allows loops to form without extreme bending while maintaining close spacing.
2Reliability
If MD-yarns are woven back into adjacent weave paths, then seam loops are formed, but loop tilting and increased spacing cause increased topographical and hydraulic marking
Solution Approach 1:
By creating multiple independent loops with distinct MD-yarns instead of having yarns weave back, the invention maintains uniform loop spacing and prevents the tilting that causes marking. Each segmented loop stands independently and interdigitates with its counterpart, creating a smooth seam surface that reduces both topographical and hydraulic marking.
Solution Approach 2:
The invention changes the geometric parameters of loop formation by having MD-yarns pass beyond adjacent yarns and form loops that interdigitate, rather than weaving back. This parameter change results in loops that remain in the fabric plane with consistent spacing, eliminating the tilting that causes marking while maintaining seam functionality.
3Reliability
If MD-yarns are woven back into the weave path, then seam loops are formed, but the back woven part can be pulled out easily resulting in weak tensile strength
Solution Approach 1:
The invention segments the seam structure into multiple independent loops formed by separate MD-yarns that pass beyond adjacent yarns. Each loop is formed by its own yarn rather than by weaving back, creating a structure where the loop formation is distinct from the fabric weave. This segmentation prevents the easy pull-out issue while maintaining reliable seam formation through interdigitated loop engagement.
4Device complexity
If loops are arranged along transverse ends with increased spacing, then seam construction is simplified, but air permeability increases causing increased hydraulic marking
Solution Approach 1:
The invention uses multiple segmented loops formed by separate MD-yarns that interdigitate to create a dense seam structure. This segmentation allows for close spacing of multiple loops along the transverse ends, reducing air permeability and hydraulic marking while maintaining manageable construction complexity through the systematic interdigitated pattern.
Data Source
AI summary
A seam for joining together the ends of woven fabric to form an endless belt is particularly suitable for joining the ends of woven synthetic dryer fabrics as used in the dryer section of paper making machines and is particularly applicable to joining the ends of those dryer fabrics in at least the machine direction of the fabric. A papermaking fabric comprising a woven fabric body having opposing ends, said fabric body having a system of MD-yarns interwoven with a system of CD yarns. The MD-yarns include first pairs of MD-yarns, second pairs of MD-yarns and third pairs of MD-yarns and the first and the second pairs of MD-yarns form two seam loops, while the third MD-yarns forms the binder. The loops are at identical length to each other over the whole fabric width. Such seam construction reduces marking and increases the seam strength and seam abrasion resistance.