Bimodal Monolayer Pleated Filter Stiffness
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Solution Overview
Problem
Existing methods for manufacturing pleated filters often compromise on web or filter properties, such as requiring multiple layers for strength and efficiency, which increases cost and complexity, and makes recycling difficult, while single-layer filters may lack stiffness and durability for high-flow applications.
Innovation Solution
A monocomponent, monolayer nonwoven web with a bimodal mass fraction/fiber size mixture of intermingled larger and smaller size continuous polymeric fibers is formed into pleated filters, providing a self-supporting matrix with enhanced stiffness and filtration efficiency without the need for additional layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a multilayer filter construction is used to provide adequate strength and filtration efficiency, then the filter meets performance requirements, but the device complexity and manufacturing cost increase
Solution Approach 1:
The patent combines multiple filtration functions into a single monolayer web by incorporating a bimodal mixture of larger size fibers (providing structural strength and stiffness) and smaller size fibers (providing filtration efficiency). This merging eliminates the need for separate support layers and filtration layers, reducing device complexity while maintaining both strength and filtration performance.
Solution Approach 2:
The patent uses a composite fiber structure within a single layer, combining fibers of different sizes (bimodal distribution) but same polymeric composition. The larger fibers (5-50 micrometers) provide mechanical strength and pleat stability, while the smaller fibers (0.1-5 micrometers) provide high filtration efficiency, creating a composite material that delivers multiple functions simultaneously.
2Strength
If additional support layers are added to stiffen the filter construction, then pleat deformation is prevented, but the pressure drop increases without contributing to efficiency
Solution Approach 1:
The patent applies local quality by distributing different fiber sizes throughout the single layer to perform different functions at different locations within the same web. Larger fibers are distributed to provide structural support and prevent pleat collapse, while smaller fibers are distributed to provide filtration, with both functioning simultaneously within the same monolayer structure without adding extra layers that would increase pressure drop.
3Strength
If multiple layers are used in the filter construction, then adequate strength is achieved, but recycling becomes difficult or impractical
Solution Approach 1:
The patent uses fibers of the same polymeric composition throughout the entire web, creating a homogeneous material structure. Although the fibers differ in size, they are all made from the same polymer material, which allows the entire filter to be recycled as a single material type, eliminating the complexity of separating and recycling different materials that would be required for multilayer filters with different polymer compositions.
4Device complexity
If a single layer of meltblown fibers is used, then the filter can be made from simple material, but the web lacks sufficient stiffness for high-flow applications
Solution Approach 1:
The patent changes the parameter of fiber size distribution within the single layer, using a bimodal mixture where larger fibers (5-50 micrometers) provide the necessary stiffness and structural integrity for high-flow applications, while the same layer maintains simplicity by remaining a single monolayer without additional support structures. This parameter change in fiber size distribution within the single layer simultaneously achieves both simplicity and adequate stiffness.
Data Source
AI summary
A pleated filter is made from a monocomponent monolayer nonwoven web containing a bimodal mass fraction/fiber size mixture of intermingled larger size and smaller size continuous monocomponent polymeric fibers of the same polymeric composition. Rows of pleats are formed in the nonwoven web, and the pleated web is cut to a desired size and shape to provide a filter element containing a self-supporting porous monocomponent monolayer matrix of fibers bonded to one another at least some points of fiber intersection and having an average initial submicron efficiency of at least 15% at a 1.52 meters/sec face velocity. The filter element is deformation resistant without requiring stiffening layers, bicomponent fibers or other reinforcing measures in the filter media layer.