Pyrotechnic Inflator Composite Overwrap Reduces Shell Thickness
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Solution Overview
Problem
The automotive industry seeks inflatable restraint systems that are smaller, lighter, and less expensive to manufacture, as existing pyrotechnic inflators are constrained by weight and size requirements.
Innovation Solution
A pyrotechnic inflator assembly with a metal shell member, end cap, and overwrap composed of a composite of fibers and resin matrix system, which includes a diffuser assembly with flow control features and a filter assembly, designed to withstand the pressure generated during pyrotechnic material reaction, allowing for reduced shell member thickness and improved manufacturing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional metal pressure vessel housings are used to withstand combustion pressures, then structural strength is sufficient, but weight and size increase
Solution Approach 1:
The patent applies composite materials by combining a thin-walled metal pressure vessel with an external composite overwrap made of fibrous reinforcement and resin matrix. The metal shell provides initial structural support while the composite overwrap reinforces the structure to withstand combustion pressures, enabling the metal shell to be made thinner and lighter while maintaining adequate strength.
Solution Approach 2:
The patent utilizes thin-walled metal pressure vessels with reduced thickness compared to traditional designs. The thin metal shell is made feasible by the added reinforcement from the composite overwrap, allowing the structure to be more flexible and lighter while still containing the combustion pressures generated during inflator operation.
2Strength
If traditional metal pressure vessel housings are used to withstand combustion pressures, then structural strength is sufficient, but manufacturing cost increases
Solution Approach 1:
The composite overwrap structure allows for more cost-effective manufacturing compared to traditional thick-walled metal pressure vessels. The composite materials can be applied in layers around the thin-walled shell, enabling modular construction and potentially reducing material costs and manufacturing complexity while achieving the required structural strength.
Solution Approach 2:
The pressure vessel structure is segmented into multiple functional layers: the thin-walled metal shell provides the primary containment structure, while the composite overwrap provides additional reinforcement. This segmentation allows each component to be optimized independently and manufactured separately before assembly, reducing overall manufacturing cost.
3Stress or pressure
If traditional thick-walled metal shells are used, then pressure containment is adequate, but inflator size increases
Solution Approach 1:
The composite overwrap enables the use of thin-walled metal pressure vessels by providing additional structural reinforcement where needed. This composite reinforcement allows the pressure containment capability to be maintained or enhanced while significantly reducing the wall thickness and overall size of the inflator housing compared to traditional thick-walled metal designs.
Solution Approach 2:
The composite overwrap can be applied selectively to specific regions of the pressure vessel where reinforcement is most needed, such as areas subject to highest stress during combustion. This localized reinforcement approach allows adequate pressure containment with minimal additional material, optimizing the size-weight-strength trade-off.
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 enables the production of smaller, lighter, and cost-effective pyrotechnic inflator assemblies capable of withstanding combustion chamber pressures, addressing industry constraints and improving manufacturing efficiency.
Implementation Method 1
gas used in the inflation of an associated inflatable element is derived from the combustion of a pyrotechnic gas generating material
Implementation Method 2
the inflator assembly can withstand the pressure generated within the combustion chamber upon reaction of the pyrotechnic material
Data Source
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AI summary
A pyrotechnic inflator assembly including a shell member and an end cap joinable with the shell member to form a subassembly. The subassembly contains a quantity of pyrotechnic material and at least in part defines a combustion chamber wherein at least a portion of the quantity of pyrotechnic material is reactable to form product gas for inflation of an associated airbag cushion and to generate pressure therewithin. A diffuser assembly can be disposed adjacent an end of the shell member and includes flow control features for controlling flow of product gas from the inflator assembly. The inflator assembly further includes a composite overwrap about at least a portion of the subassembly and the diffuser assembly such that the pyrotechnic inflator assembly can withstand the pressure generated within the combustion chamber upon reaction of the pyrotechnic material. Corresponding methods of making a pyrotechnic inflator assembly are also provided.