Sealed Blind Fastener Assembly Debris Removal
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Solution Overview
Problem
Existing blind fasteners with integrally formed closed ends face issues such as debris accumulation during thread machining, leading to stress concentration, premature fracturing, and increased friction, which can result in reduced fatigue life and improper bolt preload, especially in wet environments like airplane fuel tanks.
Innovation Solution
A sealed, blind fastener assembly comprising a receiving member with a collapsible portion and a cap that forms a secure fit, allowing for radial expansion and debris removal, reducing material usage and weight while enhancing sealing and quality inspection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If an integrally formed closed end is used in blind fasteners, then manufacturing simplicity is improved, but debris accumulation in the threaded region occurs leading to stress concentration and premature fracturing
Solution Approach 1:
The blind fastener is divided into two separate components: a receiving member with internal threads and a cap that forms the closed end. This segmentation allows the threaded region of the receiving member to be completely cleaned of debris during manufacturing, eliminating stress concentration sites, while the cap is separately formed and then attached to complete the blind fastener assembly
Solution Approach 2:
The closed end (cap) is extracted as a separate component from the threaded receiving member. This extraction allows the threaded region to be fully accessible for cleaning operations to remove all machining debris, eliminating the harmful factor of debris accumulation that would otherwise cause stress concentration and reduce fatigue life
2Strength
If an integrally formed closed end is used in blind fasteners, then structural integrity is improved, but weight increases and sealing performance deteriorates
Solution Approach 1:
The cap is designed with thin-walled construction optimized for its specific function of forming the closed end, rather than using excessive material throughout the entire fastener. This local optimization reduces overall weight while maintaining sufficient structural integrity for the cap's specific role, and allows the cap to be formed using processes like hydroforming that achieve high strength-to-weight ratios
3Ease of manufacture
If an integrally formed closed end is used in blind fasteners, then manufacturing process is simplified, but debris removal becomes difficult leading to increased friction
Solution Approach 1:
By segmenting the blind fastener into a receiving member and a cap, the threaded region of the receiving member becomes fully accessible for cleaning operations. All machining debris can be completely removed from the internal threads before the cap is attached, eliminating debris that would cause friction during bolt installation
Solution Approach 2:
The threaded region of the receiving member is completely cleaned of debris before the cap is attached. This preliminary cleaning action ensures that no machining debris remains to cause friction or interference when the accessory bolt is later threaded into the blind fastener
4Stability of the object's composition
If an integrally formed closed end is used in blind fasteners, then structural completeness is improved, but quality inspection becomes difficult
Solution Approach 1:
The blind fastener is segmented into separate components (receiving member and cap) that can be independently inspected for quality. This allows thorough examination of the threaded region, cap formation, and sealing surfaces before final assembly, making quality detection much easier than with an integrally formed closed end where internal regions are inaccessible
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 assembly provides a secure, leak-resistant, and lightweight solution that prevents debris accumulation, enhances fatigue life, and ensures proper bolt preload, making it suitable for wet environments with improved manufacturing efficiency and reduced costs.
Implementation Method 1
at least a portion of the body with at least a first outer perimeter being sufficiently malleable to undergo some amount of plastic, radial expansion
Implementation Method 2
at least a portion of the blind fastener can be radially and plastically expanded into the work piece during installation
Data Source
AI summary
A sealed attachment fastener assembly with a receiving member and a cap that can be inserted into an opening in a work piece and fixed therein from only one side of the work piece. A portion of the fastener assembly on the blind side of the work piece is collapsible into a flange. In addition, another portion of the fastener assembly is contemporaneously radially expandable within the opening of the work piece to at least rotationally secure the fastener assembly with respect to the work piece. The radial expansion will result in a high interference fit of the fastener in the work piece, which may enhance the fatigue of the installation. A cap completes the fastener assembly to substantially prevent fluid from leaking through the fastener assembly opening. The cap can be assembled with the receiving member after the internal threads within the receiving member have been machined.