Sealed Fastener Cap With Channels Reducing Installation Force
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Solution Overview
Problem
Existing methods for installing caps with sealant around fasteners require unreasonably high installation forces, especially for larger diameters, due to the frictional resistance between the cap members, making manual installation impractical.
Innovation Solution
The cap design features inner and outer cap members with longitudinal channels and ridges that reduce friction and facilitate sealant flow, allowing for a reduced installation force by creating a path for the sealant to flow more freely, and the use of locating features for interference fit ensures secure adhesion without restricting out-gassing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a two-piece cap construction with sealant between inner and outer cap members is used, then spark suppression is provided, but installation force becomes unreasonably high for larger fastener diameters
Solution Approach 1:
The cap is divided into inner and outer cap members with sealant between them. The inner cap member fits over the fastener and the outer cap member fits over the inner cap member, creating a segmented structure that provides spark suppression while reducing installation force through the introduction of channels
Solution Approach 2:
Channels are introduced as intermediary pathways between the inner and outer cap members. These channels allow sealant to flow more freely during installation, reducing the frictional resistance that would otherwise require unreasonably high installation forces for larger fastener diameters
2Strength
If sealant is distributed between inner and outer cap members, then adhesion is achieved, but frictional resistance prevents free sealant flow
Solution Approach 1:
The space between inner and outer cap members is segmented into multiple channels rather than a single continuous space. This segmentation creates multiple pathways for sealant flow, reducing the overall frictional resistance while still achieving comprehensive adhesion when sealant fills the channels and exits at the base
Solution Approach 2:
Channels are introduced as a dimensional feature within the gap between cap members. Rather than relying on a simple radial gap, the channels provide a structured three-dimensional pathway that guides sealant flow from the top of the cap down to the base, facilitating easier operation during installation
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
This design significantly reduces the installation force required for caps of all fastener diameters, including larger ones, while ensuring even sealant distribution and adhesion, preventing voids and supporting spark suppression during lightning strikes.
Implementation Method 1
The plurality of channels form a path along which the sealant may flow more freely as compared to the nominal gap provided between the side walls of the inner and outer cap members. This is due to the reduced effect of friction of the sealant with the walls
Data Source
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AI summary
A cap for forming a sealed cavity around one end of a fastener, the cap having a two-piece construction comprising an outer cap member and an inner cap member. A quantity of sealant is provided between the inner and outer cap members which, upon installation of the cap, is urged to flow between the inner and outer cap members and collect at the base of the outer cap member, to form a bead of sealant around the circumference of the cap, sufficient to adhere the cap to the structure when the sealant cures. A plurality of channels are provided between the inner and outer cap members to facilitate the flow of sealant.