Wet Part Fiber Density Reduction via Vacuum Pulling
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Solution Overview
Problem
Existing pulp molding processes face challenges in efficiently forming articles with complex shapes and desired porosity levels, particularly in reducing fiber density to achieve optimal fluid flow characteristics while minimizing damage and ensuring smoothness.
Innovation Solution
The method involves using a forming tool with a forming screen and a transfer tool to apply vacuum pressure, gradually pulling the second surface of the wet part away from the first surface, allowing fibers to expand and decrease density, and using transfer screens with smaller pores to evenly distribute suction force, facilitating the removal of excess liquid and setting fibers at a reduced density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If vacuum force is applied to form the wet part on the wire mesh, then the material adheres to the forming surface and takes the desired shape, but the fiber density becomes too high which reduces fluid flow characteristics
Solution Approach 1:
The forming process is divided into two distinct stages: first forming the wet part on the wire mesh with high fiber density to achieve shape accuracy, then transferring it to the drum dryer where the outer surface is pulled away to create a porous structure with reduced fiber density. This segmentation allows both high shape accuracy and optimal fluid flow characteristics to be achieved at different stages.
Solution Approach 2:
The invention introduces a new dimension to the forming process by using a drum dryer with a cylindrical surface that allows the outer surface of the wet part to be pulled away from the inner surface. This dimensional change creates internal porosity and reduces fiber density without compromising the external shape integrity formed on the wire mesh.
2Quantity of substance
If the outer surface of the wet part is pulled away from the inner surface to decrease fiber density, then fluid flow characteristics improve, but the wet part may become damaged or lose structural integrity
Solution Approach 1:
The wet part is formed on a wire mesh that provides structural support during the entire process. The wire mesh acts as a cushioning framework that prevents the wet part from collapsing or becoming damaged when the outer surface is pulled away during drying, maintaining structural integrity while allowing fiber density reduction.
Solution Approach 2:
The drum dryer surface acts as an intermediary that gradually pulls the outer surface of the wet part away from the inner surface. This intermediary mechanism distributes the pulling force evenly throughout the wet part, preventing localized stress concentrations that could cause damage while effectively reducing fiber density.
3Manufacturing precision
If a vacuum force is applied through the wire mesh, then material is suctioned onto the forming surface, but the pores in the wire mesh are too small compared to the main body pores which limits liquid passage
Solution Approach 1:
The drying system uses two distinct surfaces with different pore characteristics: the wire mesh forming surface with small pores for smooth surface formation, and the drum dryer surface with larger pores for effective liquid passage. This segmentation allows each surface to optimize its specific function without compromise.
Solution Approach 2:
The invention transitions from a single-surface forming approach to a dual-surface approach with the drum dryer. The drum dryer surface provides a new dimension for liquid removal with larger effective pore sizes, compensating for the limited pore size of the wire mesh while maintaining the smooth surface quality achieved during forming.
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 enables the creation of articles with controlled porosity and fluid flow characteristics, such as filtering face masks that can filter out a high percentage of airborne particulates, while maintaining structural integrity and smoothness.
Implementation Method 1
a forming screen and a transfer screen to apply vacuum pressure, gradually pulling the second surface of the wet part away from the first surface
Implementation Method 2
using transfer screens with smaller pores to evenly distribute suction force, facilitating the removal of excess liquid
Data Source
AI summary
According to examples, a wet part composed of fibers may be removed from a slurry of the fibers on a forming screen having pores, the wet part having a first surface in contact with the forming screen. A second surface of the wet part may be pulled away from the first surface of the wet part while a suction force is applied onto the first surface through the pores in the forming screen to cause a density at which the fibers are arranged in the wet part to be decreased. In addition, following a predefined length of time after initiation of the pulling of the second surface away from the first surface, the wet part may be removed from the forming screen, in which an article formed from the wet part is to function as a filter following the wet part being dried.