Double-Shell Lightning Protection Cap With Angular Locking Assembly
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Solution Overview
Problem
Existing lightning protection caps for aircraft attachment elements face challenges in ensuring secure assembly without angular play and preventing deformation or breakage, particularly due to stress during assembly and the risk of fuel leaks from lightning strikes.
Innovation Solution
A double-shell lightning protection cap design featuring complementary attachment means, including a ramp and protuberance forming a housing, which allows the outer shell to slide and angularly lock onto the inner shell, preventing rotation and minimizing deformation risk, with localized contact points and progressive deformation access during assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the outer shell is snapped onto the inner shell vertically, then the assembly is simple and quick, but angular play occurs between the shells and stresses exceed the elastic limit causing breakage
Solution Approach 1:
The patent introduces a preliminary alignment phase where the outer shell is positioned at a predetermined angle (e.g., 45 degrees) relative to the inner shell before final engagement. This preliminary positioning ensures proper orientation of attachment means (such as ribs, grooves, or interlocking features) to prevent angular play during subsequent vertical snapping, while distributing assembly stresses to remain within elastic limits of the materials.
2Reliability
If welding or gluing is used to assemble the shells, then angular play is eliminated, but additional manufacturing steps and complexity are introduced
Solution Approach 1:
The patent designs self-aligning attachment means (such as complementary geometric features like tapered ribs, snap-fit mechanisms, or friction-fit interfaces) that automatically eliminate angular play between shells during assembly without requiring external welding or gluing operations. The geometry of the attachment means itself provides the alignment and securing function, making the system self-sufficient and eliminating the need for additional manufacturing steps.
3Reliability
If multiple contact zones are provided between shells, then friction resistance is maximized for secure assembly, but assembly difficulty and precision requirements increase
Solution Approach 1:
The patent divides the attachment interface into multiple discrete, segmented contact zones (such as separate ribs, lugs, or modular interlocking features) distributed around the circumference of the shells. Each segment provides localized friction resistance and alignment, collectively achieving high overall reliability while maintaining ease of assembly through modular, distributed engagement rather than requiring large continuous contact surfaces that would increase assembly difficulty.
Data Source
AI summary
A lightning protection cap is for sealing an attachment element attached to the structure of an aircraft. The lightning protection cap includes an inner shell defining an interior volume for receiving the attachment element and an outer shell configured to cover the inner shell. The inner and outer shells include complementary first and second attachment devices capable of cooperating to enable engagement of the outer shell on the inner shell. first and second attachment devices are configured to angularly lock the outer shell relative to the inner shell when the outer shell is rotated relative to the inner shell.