Fastener Spark Prevention Cap With Controlled Sealant Flow
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Solution Overview
Problem
Existing spark containment caps for fasteners on aircraft surfaces are prone to leakage and incomplete sealing due to uncured sealing material flow, which can lead to air and sealant ingress, compromising the integrity of the sealed cavity during lightning strikes.
Innovation Solution
A cap design featuring an annular base with a biasing configuration, including protrusions and guide elements, that positively biases the base rim against the surface, minimizing leakage by ensuring a secure engagement and retention of the cap, and an annular skirt with an inlet and outlet for controlled sealant flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an annular pocket with sealant material is provided between the skirt and the annular base, then sealing capability is improved, but uncured sealant material may flow and cause leakage
Solution Approach 1:
The patent extracts the problematic flowing sealant material from the sealed cavity by providing a controlled flow path through the skirt. The flow path includes an inlet and outlet that allow excess sealant to be drained away from the sealed cavity, preventing leakage while maintaining the sealing function of the annular pocket.
Solution Approach 2:
The patent introduces a flow path as an intermediary system between the annular pocket and the external environment. This flow path acts as a mediator that controls sealant material movement, allowing uncured sealant to exit through the outlet without compromising the seal integrity of the main cavity.
2Reliability
If the base rim is engaged with the surface to prevent leakage, then sealing integrity is improved, but the cap may not be securely retained
Solution Approach 1:
The patent merges two separate functions into a unified design: the base rim simultaneously provides both sealing engagement with the surface and mechanical retention of the cap. The biasing configuration integrates both the sealing pressure and retention force into a single structural element, eliminating the need for separate retention mechanisms.
Solution Approach 2:
The base rim is designed with multi-functionality, serving both as a sealing element that prevents leakage and as a retention element that secures the cap to the fastener. The biasing configuration enables the base rim to perform multiple functions without requiring additional components.
3Reliability
If a biasing configuration is added to positively bias the base rim against the surface, then leakage is minimized, but device complexity increases
Solution Approach 1:
The biasing configuration utilizes the inherent flexibility of the cap body material to create a resilient base rim that can deform and apply continuous biasing force against the surface. This flexible membrane approach provides the necessary sealing pressure and retention force without requiring complex mechanical spring or actuation systems.
Data Source
AI summary
A cap for forming a sealed cavity around an end of a fastener protruding from a surface of a structure is disclosed. The disclosure relates to a spark prevention cap. The cap has an annular base with an annular base terminating at a base rim. The base rim surrounds an opening into a central cavity for receiving the end of the fastener. The base rim lies in a base rim plane around at least a majority of a circumference of the annular base. An annular skirt provides an annular pocket in which a sealant material is received. A biasing configuration is configured to positively bias the base rim against the surface of the structure.