Pivoting Spark Containment Cap for Inclined Fastener Sealing
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Solution Overview
Problem
Existing spark containment caps face challenges in efficiently sealing fasteners protruding at non-perpendicular angles from aircraft structures, leading to potential spark and plasma issues during lightning strikes due to misalignment and sealant leakage.
Innovation Solution
A spark containment cap design featuring a pivoting cap upper with a ball joint and deformable concertina configuration, allowing for alignment with inclined fasteners and minimizing sealant leakage through a controlled injection system, which includes a locating member for precise alignment and a sealing material that cures to secure the cap in place.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a traditional fixed spark containment cap is used, then the sealing structure is simple, but it cannot accommodate fasteners at non-perpendicular angles leading to misalignment and sealant leakage
Solution Approach 1:
The cap upper is made pivotable relative to the annular skirt through a ball joint mechanism, allowing the cap to dynamically adjust its orientation to accommodate fasteners at various angles. This dynamic capability enables the sealant injection system to align properly with inclined fasteners while maintaining a relatively simple overall cap structure.
Solution Approach 2:
The cap is divided into two main segments: a fixed annular skirt that provides the sealing interface with the structure, and a pivotable cap upper that contains the fastener and can be oriented independently. This segmentation allows each part to perform its specific function optimally - the skirt maintains sealing while the upper adapts to fastener angle.
2Manufacturing precision
If the cap is designed to accommodate inclined fasteners, then alignment is improved, but sealant leakage may occur during injection
Solution Approach 1:
The ball joint mechanism is pre-configured with a locating member that guides and constrains the pivot movement. This preliminary positioning ensures that when sealant is injected, the cap upper is already properly aligned with the fastener axis, preventing sealant leakage while maintaining precise alignment for inclined fasteners.
Solution Approach 2:
The ball joint acts as an intermediary mechanism between the fixed annular skirt and the movable cap upper. It mediates the transition from a fixed orientation to an aligned orientation, allowing the cap upper to pivot into the correct position for sealant injection while the annular skirt remains stationary and sealed.
3Ease of operation
If a pivotable cap upper is implemented, then alignment with inclined fasteners is achieved, but the joint complexity increases
Solution Approach 1:
The ball joint provides a simple yet effective pivot mechanism that allows the cap upper to rotate and align with inclined fasteners. This dynamic joint is mechanically straightforward, using a ball-and-socket type connection that enables multi-directional adjustment without complex actuators or control systems.
Solution Approach 2:
The ball joint mechanism is designed to be self-aligning through its geometric constraints and the locating member. When the cap is installed, gravity and the locating member guide the cap upper into the correct orientation automatically, eliminating the need for complex alignment procedures or additional adjustment mechanisms.
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 effectively seals fasteners at non-perpendicular angles, reducing the risk of spark and plasma formation during lightning strikes by ensuring a secure and leak-proof seal, even when the fastener axis is inclined, thereby enhancing the safety and reliability of aircraft structures.
Implementation Method 1
The cap upper is arranged to pivot relative to the annular skirt. The joint comprises the ball joint.
Implementation Method 2
The joint comprises the deformable portion. The deformable portion may comprise a concertina configuration.
Implementation Method 3
A volume of gas is enclosed in the sealed cavity around the fastener. The cap is sealed to the structure by a curable sealant provided around an opening to the sealed cavity.
Implementation Method 4
The locatable annular skirt may help ensure that the skirt is in abutment with the structure along all or substantially all of the skirt's rim.
Data Source
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AI summary
The present application relates to a spark containment cap. The cap forms a sealed cavity around an end of a fastener protruding from a structure. The cap has a cap body defining an air cavity arranged to enclose the end of the fastener. The cap body includes an annular base (210) terminating at a base rim (211) which surrounds an opening into the air cavity. An annular skirt (230) of the cap provides an annular sealing volume extending around the base rim (211) arranged to receive an annular bead of a curable sealing material around the opening into the cavity to provide a seal between the cap body and the structure to seal a volume of gas within the cavity. The cap body comprises a cap upper arranged to receive at least part of the end of the fastener. The cap upper (220) is positionable so that an axis of the cap upper (220) is offset from an axis of the annular skirt (230).