Three-Layer Board Web Forming via Gap Former
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Solution Overview
Problem
The production of three-layer board webs faces challenges such as low bonding strength between layers, energy-intensive fourdrinier forming units with low running speeds, and surface quality issues due to infiltration of impurities and fibers from the middle layer to the surface layers, particularly in folding box boards (FBB) and solid bleached sulfate (SBS) production.
Innovation Solution
A forming section comprising a multilayer headbox and a gap or combi twin-wire former, where pulp suspension is fed to a gap between wires or a short one-wire section followed by a twin-wire section, utilizing a non-pulsating forming shoe and an Aqua-headbox for controlled water removal and layer separation, ensuring gentle dewatering and maintaining layer purity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If separate web forming units are used for each layer of three-layer board web, then layer formation control is improved, but energy consumption increases and running speed decreases
Solution Approach 1:
The patent combines multiple layer formation functions into a single integrated forming unit with a multilayer headbox that deposits all three layers simultaneously onto one forming wire. This merging eliminates the need for multiple separate fourdrinier forming units, reducing energy consumption while maintaining the ability to control layer formation through the headbox design and deposition process.
2Manufacturing precision
If multiple separate web forming units are used for each layer, then layer formation control is improved, but device complexity increases
Solution Approach 1:
The invention merges the functionality of multiple separate forming units into a single integrated forming unit equipped with a multilayer headbox. This consolidation reduces device complexity by eliminating redundant components while preserving layer formation control capabilities through the specialized headbox design that manages multiple pulp suspensions.
Solution Approach 2:
The single forming unit is designed with multi-functionality to handle all three layers of the board web simultaneously. The forming unit universally processes multiple pulp suspensions from the multilayer headbox, performing the work of what would traditionally require three separate forming units, thus reducing overall system complexity.
3Productivity
If traditional forming units are used for three-layer board web, then water removal capacity is improved, but bonding strength between layers deteriorates
Solution Approach 1:
The patent applies preliminary action by depositing the middle layer first onto the forming wire, then subsequently depositing the surface layers onto the middle layer. This sequential deposition with controlled dewatering at each stage ensures proper bonding between layers while maintaining adequate water removal capacity. The forming unit is designed to handle the dewatering process in a controlled manner that preserves interlayer bonding.
4Productivity
If high water removal volume is achieved in forming section, then dewatering efficiency is improved, but surface quality deteriorates due to impurity infiltration
Solution Approach 1:
The patent uses preliminary action by first depositing the middle layer onto the forming wire and allowing initial dewatering to occur. Then the surface layers are deposited onto this pre-formed middle layer. This sequential approach enables controlled dewatering at each stage, achieving high overall water removal efficiency while preventing impurity infiltration into the surface layers, thus maintaining surface quality.
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 achieves strong bonding between layers, high layer purity, and increased running speeds, allowing for the use of cheaper pulp with desired bulkiness, reducing manufacturing costs and improving surface quality by minimizing impurity infiltration.
Implementation Method 1
The task of a forming unit is to remove water from fiber suspension fed by the headbox. When the web is manufactured of watery fiber stock, water in the stock is removed on the forming section through a forming wire or forming wires for starting the formation of the web.
Implementation Method 2
Fibers remain on the forming wire or between the forming wires moving together.
Data Source
AI summary
The invention relates to a method for forming a three-layer board web, preferably a folding box board (FBB) or a solid bleached (sulfate) board (SBS), in a forming section (300) comprising a multilayer headbox (100) and a forming unit (200). In the method the layers of the three-layer board web are first formed of pulp suspension in the multilayer headbox (100) and fed to only one forming unit (200), a gap former where the pulp suspension from the multilayer headbox is fed to a gap between lower and upper wires for water removal and for joining the layers of the three-layer board web and where water is first removed by a non-pulsating forming shoe (37, 39).