Sealant Flow Cap Structure for Fastener Leakage Control
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Solution Overview
Problem
Existing spark containment caps for fasteners on aircraft fail to effectively manage sealant flow and prevent leakage during lightning strikes, leading to potential electrical hazards due to high electrical resistance differences between composite materials and metallic fasteners.
Innovation Solution
A cap design featuring an annular base with a protuberance and offset skirt rim, which guides sealant flow annularly and allows controlled air escape, preventing upward cap displacement and leakage by ensuring even sealant distribution and intimate cap engagement with the structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sealant is injected into the annular pocket to seal the cavity and adhere the cap, then sealing effectiveness is improved, but upward force on the cap increases causing potential displacement
Solution Approach 1:
The patent introduces a protuberance in the annular base that creates a localized flow restriction region within the annular pocket. This local structural modification directs sealant flow in a specific annular pattern, concentrating sealing action at the critical interface between the cap base and structure while preventing excessive sealant from generating upward displacement force on the cap body.
2Object-affected harmful factors
If the cap is designed to seal the cavity around the fastener end, then electrical hazard prevention is improved, but sealant leakage control becomes difficult
Solution Approach 1:
The patent incorporates an outlet hole in the skirt portion of the cap, positioned to allow excess sealant and trapped air to escape during the sealing process. This preliminary egress path prevents sealant from being forced backward into the sealed cavity or leaking uncontrollably, ensuring that sealant remains contained within the annular pocket where it can properly adhere the cap to the structure without compromising the seal integrity.
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 cap design enhances sealant flow control, limits cap displacement, and prevents leakage, ensuring a secure seal around fasteners even during lightning strikes, thereby enhancing safety and reliability in aircraft structures.
Implementation Method 1
a protuberance protruding in the annular pocket and facing the inlet hole to promote a flow of sealant injected through the inlet hole to flow annularly around the annular pocket
Implementation Method 2
The sealing material forms a bead which seals the central cavity and adheres the cap to a structure
Data Source
AI summary
A cap for forming a sealed cavity around an end of a fastener is disclosed. The cap has a cap body with an annular base terminating at a base rim which surrounds an opening into a central cavity. The cap also has an annular skirt providing an annular pocket between the skirt and the base. An inlet hole is provided in the skirt which is in fluid communication with the annular pocket. A protuberance protrudes in the annular pocket and faces the inlet hole to promote a flow of sealant injected through the inlet hole to flow annularly around the annular pocket.