Compressed Wire Mesh Filter Hoop Strength
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Solution Overview
Problem
Airbag filters face challenges in maintaining hoop strength, filtering efficiency, and heat sink capacity while avoiding the use of expensive and potentially failing perforated or expanded metal bands, and ensuring uniform pressure drop and quality control in mass production.
Innovation Solution
A wire mesh filter with a compressed knitted mesh structure and an interlocked hoop wire around its outside, compression molded to enhance hoop strength and heat sink capacity without significant additional manufacturing costs or adverse effects on filtering and heat sink properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If perforated or expanded metal bands are used to increase hoop strength, then the filter can withstand higher pressures, but the cost increases and reliability decreases due to potential band failure
Solution Approach 1:
The patent combines the hoop wire and mesh filter into a single integrated structure where the hoop wire is interlocked with the mesh during compression molding. This eliminates the need for separate metal bands and creates a unified filter assembly that maintains structural integrity without additional failure points.
Solution Approach 2:
The patent uses a simple wire wrap structure instead of complex perforated or expanded metal bands. This simpler design reduces manufacturing cost and eliminates the reliability issues associated with complex metal band structures that can fail under pressure.
2Reliability
If denser and longer filter devices are used to filter particulates, then filtering efficiency improves, but the pressure drop increases and interferes with airbag inflation rate
Solution Approach 1:
The patent applies different wire densities to different regions of the filter. The upstream side has a coarser mesh that allows higher gas flow rates, while the downstream side has a finer mesh that provides effective particulate filtration. This gradient structure maintains both high inflation rate and good filtering efficiency.
3Reliability
If the filter is made tighter to improve filtering, then particulate removal efficiency increases, but the pressure drop across the filter increases
Solution Approach 1:
The patent creates a gradient in mesh density from upstream to downstream. The upstream region has larger openings for low resistance gas flow, while the downstream region has smaller openings for effective particulate capture. This local variation in quality resolves the contradiction between filtration efficiency and pressure drop.
4Reliability
If multiple layers of screens and fibrous material are used to improve filtering, then particulate removal improves, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent uses a composite structure combining wire mesh and fibrous material in a single layered filter element. The wire mesh provides structural support and primary filtration, while the fibrous material fills gaps and captures finer particulates. This composite approach achieves high particulate removal with a single integrated layer rather than multiple separate layers.
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 solution significantly increases hoop strength and filtering efficiency while maintaining the filter's space constraints, eliminating the need for perforated metal bands and ensuring uniform density and heat management, thus enhancing airbag deployment safety and reliability.
Implementation Method 1
a compressed wire mesh forming an annulus and having at least one hoop wire around the outside of the filter and interlocked with the wire mesh when the filter is compression molded
Implementation Method 2
The efficiency of this type of filter is dependent upon how tightly the material is packed; a tighter packing leads to more efficient filtering but also to a higher pressure drop
Data Source
AI summary
A compressed wire mesh filter for an airbag assembly has one or more wires wrapped around the outer perimeter of the filter prior to final compression of the mesh to increase the hoop strength of the filter.