Structured Forming Fabric Deep Pockets Papermaking
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Solution Overview
Problem
Conventional papermaking fabrics have shallow depth pockets, limiting the bulk that can be built into the sheet and resulting in a non-uniform finish due to inconsistent dewatering, especially when using high-tension press nips and permeable belts.
Innovation Solution
A structured forming fabric with deep pockets defined by warp and weft yarns, where each pocket is formed by four sides, with two sides defined by warp knuckles passing over three consecutive weft yarns and the other two sides by weft knuckles passing over three consecutive warp yarns, allowing for effective dewatering and maintaining sheet quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If conventional papermaking fabrics with shallow depth pockets are used, then the fabric structure is simple and easy to manufacture, but the bulk and absorbency capacity of the paper sheet are limited
Solution Approach 1:
The patent transitions from conventional two-dimensional flat fabric structures to three-dimensional structured fabrics with deep pockets and peaks. The weave pattern creates vertical dimensionality with pockets extending downward from the surface, enabling the fabric to accommodate and retain bulk within the paper sheet while maintaining a relatively simple woven construction.
Solution Approach 2:
The fabric employs localized structural variations where specific regions have deep pockets while other regions have peaks. This local differentiation allows different areas of the fabric to perform specialized functions - pockets for bulk retention and absorbency, peaks for structural support and dewatering - without requiring the entire fabric to be complex.
2Manufacturing precision
If conventional fabrics with shallow pockets are used, then the manufacturing process is simple, but the dewatering consistency and sheet finish uniformity are poor
Solution Approach 1:
The fabric surface is segmented into repeating patterns of pockets and peaks through the weave structure. This segmentation creates multiple localized zones that work together to ensure uniform dewatering across the entire fabric surface, as each pocket region contributes to consistent moisture removal while maintaining uniform sheet finish.
Solution Approach 2:
The patent modifies the geometric parameters of the fabric structure, specifically increasing pocket depth and adjusting the ratio between pocket depth and peak height. These parameter changes optimize the fabric's ability to maintain consistent dewatering performance and uniform sheet finish while remaining manufacturable through standard weaving processes.
3Productivity
If high-tension press nips and permeable belts are used, then moisture removal efficiency is improved, but sheet quality and integrity are compromised
Solution Approach 1:
The fabric structure provides beforehand cushioning through its peak regions that protect the sheet from excessive compression during high-tension pressing. The peaks act as cushioning elements that distribute pressure evenly, preventing localized damage to sheet integrity while allowing efficient moisture removal through the pocket regions.
Solution Approach 2:
The fabric creates local quality differentiation where pocket regions facilitate moisture removal while peak regions protect sheet integrity. This local functional separation allows the fabric to simultaneously support high-tension pressing for productivity while maintaining sheet quality through the protective peak structures.
4Quantity of substance
If deep pockets are introduced into the fabric structure, then bulk and absorbency capacity increase, but the fabric complexity and manufacturing difficulty increase
Solution Approach 1:
The patent optimizes the parameter of pocket depth to achieve significant absorbency capacity improvements. By increasing pocket depth to specific ratios relative to peak height and adjusting the spacing between pockets, the fabric achieves enhanced bulk and absorbency while keeping the overall structure manufacturable through conventional weaving techniques.
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 structured fabric enhances the caliper and absorbency capacity of the paper sheet by 30% compared to conventional methods, maintaining sheet quality and integrity during high-tension processing, and allows for efficient moisture removal without compacting the sheet.
Implementation Method 1
The belt, often referred to as a 'forming fabric,' provides a papermaking surface on the upper surface of its upper run which operates as a filter to separate the cellulosic fibers of the paper stock from the aqueous medium
Implementation Method 2
The aqueous medium drains through mesh openings of the forming fabric, known as drainage holes, by gravity or vacuum
Implementation Method 3
Pressure from the rollers removes additional moisture from the web; the moisture removal is often enhanced by the presence of a 'batt' layer of the press felt
Implementation Method 4
The structured fabric enhances the caliper and absorbency capacity of the paper sheet by 30% compared to conventional methods
Data Source
AI summary
A fabric for a papermaking machine that includes a machine facing side and a web facing side comprising pockets formed by warp and weft yarns is provided. Each pocket is defined by four sides on the web facing side, each of the four sides is formed by a knuckle of a single yarn that passes over only two consecutive yarns to define the knuckle.