Headbox Flow Zone Design for Random Fiber Orientation in Foam Forming
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Solution Overview
Problem
Existing foam forming processes struggle with controlling fiber orientation in webs, resulting in fibers being predominantly oriented in the machine direction, leading to non-uniform physical properties between the machine and cross-machine directions.
Innovation Solution
A headbox design with specific flow zones, including a constriction zone, slice zone, expansion zone, and formation zone, combined with a process of depositing a slurry of fibers and superabsorbent particles, promotes turbulent flow and random fiber orientation, ensuring uniform distribution of fibers and solid components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If foam forming process is used to produce webs, then fiber suspension is conveyed downstream with plug flow characteristics, but fiber orientation becomes predominantly in the machine direction resulting in non-uniform physical properties
Solution Approach 1:
The headbox design incorporates a dynamic flow regime transition from plug flow to turbulent flow. The constriction zone creates high velocity flow that transitions to turbulent flow in the expansion zone, dynamically changing the flow characteristics to achieve random fiber orientation while maintaining high production efficiency
Solution Approach 2:
The patent changes the flow parameters by designing specific headbox geometry with constriction and expansion zones. This creates a transition from laminar/plug flow to turbulent flow regime, changing the Reynolds number and flow characteristics to achieve uniform fiber orientation distribution in both machine and cross-machine directions
2Device complexity
If conventional headbox design is used, then web formation is simplified, but fiber orientation cannot be controlled resulting in uniform machine direction alignment
Solution Approach 1:
The headbox is segmented into distinct functional zones: a constriction zone for velocity increase, a transition zone for flow regime change, and an expansion zone for turbulent mixing. This segmentation allows controlled fiber orientation without excessive overall complexity, with each zone performing a specific function in the flow transformation process
3Strength
If foam forming process is used, then web bulk and absorbency are improved, but fiber orientation uniformity between machine and cross-machine directions deteriorates
Solution Approach 1:
The patent uses hydraulic principles by designing the headbox to utilize fluid flow dynamics. The constriction and expansion zones create turbulent flow through hydraulic design, which randomly orients fibers while maintaining the foam structure that provides bulk and absorbency properties
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 system produces webs with uniform and random fiber orientation, enhancing the uniformity of physical properties and facilitating the distribution of superabsorbent particles, improving the quality and consistency of the substrate.
Implementation Method 1
The slice zone can have a slice height (ts) and slice length (ls) such that the slurry of fibers undergoes turbulent flow within the expansion zone
Implementation Method 2
Fluids can be drained from the slurry of fibers through the forming surface within the formation zone to form an embryonic web
Data Source
AI summary
Apparatuses and processes for producing a substrate are described. A headbox is also provided. The headbox can include at least one flow section. The at least one flow section can include a constriction zone; a slice zone; an expansion zone; and a formation zone. A process for producing a web is also provided. The process can include depositing a slurry of fibers into a constriction zone. The slurry of fibers can then be flowed from the constriction zone through a slice zone and into an expansion zone. The slurry of fibers can then be flowed from the expansion zone into a formation zone. The slurry can be conveyed on a moving forming surface. Fluids may be drained from the slurry of fibers through the forming surface within the formation zone to form an embryonic web. The embryonic web may be dried.