Fastener Interference Fit for Spark Containment
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Solution Overview
Problem
Aircraft manufacturing faces challenges in achieving fault-tolerant spark protection in flammable zones due to manufacturing faults like oversized holes, contamination, and inconsistencies, which can lead to sparking and particle ejection, requiring additional steps and time for cap seal application.
Innovation Solution
A fastener system comprising a sleeve, a washer, and a bolt, where the washer is positioned between the sleeve and the aircraft structure, forming an interference fit to seal the hole and prevent particle ejection, eliminating the need for cap seals and enhancing fault tolerance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a cap seal is applied over the fastener head to achieve fault tolerance, then spark protection reliability is improved, but installation time and process complexity increase
Solution Approach 1:
The invention extracts the sealing function from the cap seal and relocates it to the fastener system itself through the interference fit between the sleeve and fastener, eliminating the need for separate cap seal application while maintaining fault tolerance
Solution Approach 2:
The sealing function is merged with the fastening function by designing the sleeve-fastener interference fit to simultaneously provide both mechanical fastening and spark containment, consolidating multiple functions into a single integrated system
2Reliability
If a cap seal is applied over the fastener head to achieve fault tolerance, then spark protection reliability is improved, but device complexity increases
Solution Approach 1:
The invention removes the cap seal component entirely and extracts its sealing function, reducing the number of parts and simplifying the overall fastener system while maintaining fault tolerance through the interference fit design
3Reliability
If an interference fit is formed between the sleeve and aircraft structure to prevent sparking, then electrical connection is improved, but manufacturing precision requirements increase due to faults like oversized holes
Solution Approach 1:
The invention designs the interference fit with built-in tolerance compensation that cushions against manufacturing variations, allowing the system to maintain reliable electrical connection even when holes are oversized or have other manufacturing inconsistencies
Solution Approach 2:
The interference fit parameters are specifically designed to accommodate a range of hole dimensions, transforming the rigid precision requirement into a more flexible parameter range that still ensures adequate electrical connection and spark containment
4Reliability
If cap seals are applied to each fastener to ensure consistent coverage, then spark protection consistency is improved, but productivity decreases
Solution Approach 1:
The invention eliminates the cap seal application step entirely, removing the productivity bottleneck while maintaining consistent spark protection through the pre-designed interference fit that requires no additional operations
Solution Approach 2:
The fastener system provides its own spark containment function through the interference fit between sleeve and fastener, making the system self-sufficient and eliminating the need for separate cap seal application operations
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 provides efficient and consistent spark containment in flammable zones, reducing installation time and costs by eliminating the need for cap seals and ensuring reliable particle containment even with manufacturing faults.
Implementation Method 1
the sleeve expands to form an interference fit with the washer
Data Source
AI summary
A method and apparatus for forming a seal over a hole in a structure. The apparatus comprises a washer, a sleeve, and a fastener. The washer has a first channel. The sleeve has a second channel and an expandable section. The sleeve is positioned inside the first channel in the washer. The fastener has an elongate portion positioned inside the second channel of the sleeve to cause at least a portion of the expandable section of the sleeve to form a first interference fit with the washer.