Segmented Threaded Fastener for Blind-Hole Back-Out Resistance
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Solution Overview
Problem
Existing threaded fastener retention methods are inadequate in withstanding cyclic loading variations, such as those caused by temperature changes and vibrations, leading to potential loosening issues, and existing solutions like lock wires, washers, and thread-locking compounds increase complexity, cost, and assembly time, while being limited in application, especially for threaded fasteners in blind holes.
Innovation Solution
A threaded fastener design with a segmented body that allows for increased tension between segments after installation in a blind hole, utilizing a mechanism like a blind rivet or inner threaded rod to distribute mechanical stresses and enhance retention, thereby addressing the limitations of prior methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lock wire is used to prevent fastener loosening, then fastener retention is improved, but the assembly complexity increases and requires external anchoring points
Solution Approach 1:
The patent combines the fastener and retention mechanism into a single integrated unit. The threaded fastener includes an integral retention mechanism (such as a deformed tail or locked collar) that is built into the fastener body itself, eliminating the need for separate lock wires or external anchoring structures. This merging resolves the contradiction by maintaining reliability while reducing assembly complexity.
Solution Approach 2:
The fastener incorporates a self-retaining mechanism that automatically engages after installation. The retention feature (e.g., deformed tail, locked collar, or interference fit elements) is designed to self-activate upon fastener installation, requiring no additional components or external anchoring points. This self-service approach improves retention while simplifying the overall assembly.
2Reliability
If lock washers are used to improve fastener retention, then resistance to loosening is enhanced, but the number of parts and assembly time increase
Solution Approach 1:
The retention mechanism is integrated directly into the fastener body, combining what would traditionally be separate components (fastener + lock washer) into a single unit. This eliminates the need for additional washers and reduces the number of assembly steps, thereby improving productivity while maintaining resistance to loosening.
Solution Approach 2:
The fastener includes built-in retention features (such as deformed tails, locked collars, or interference fit elements) that automatically engage upon installation without requiring separate lock washers. This self-retaining capability reduces assembly time while providing reliable resistance to loosening.
3Reliability
If thread-locking compounds are applied to prevent fastener loosening, then retention is improved, but disassembly difficulty increases and cost rises
Solution Approach 1:
The fastener is divided into distinct functional segments: the threaded body for engagement and the retention mechanism for preventing loosening. This segmentation allows the retention function to be achieved through mechanical means (deformed tail, locked collar, or interference fit) rather than chemical adhesives, enabling easy disassembly by simply unscrewing the fastener without dealing with cured compounds.
Solution Approach 2:
The fastener incorporates a mechanical self-retaining mechanism that provides retention through physical interference or locking geometry rather than chemical bonding. This allows the fastener to be easily disassembled by applying reverse torque, maintaining ease of repair while improving retention reliability.
4Reliability
If locking nuts or paired nuts are used in through-holes, then fastener retention is improved, but applicability to blind holes is limited
Solution Approach 1:
The fastener incorporates a self-retaining mechanism that functions independently of the hole type (through-hole or blind hole). The retention feature (deformed tail, locked collar, or interference fit elements) is designed to engage with the blind hole wall or fastener body itself, eliminating the need for paired nuts or external locking components. This provides universal applicability to both through-holes and blind holes while maintaining reliable retention.
Data Source
AI summary
A threaded fastener composed of separate upper and lower portions with a small axial freedom of movement relative to one another. After being threaded into a blind hole together, the portions are moved relative to one another and locked in place, creating a distribution of stresses which resists backing-out of the fastener without the various drawbacks which limit prior art solutions to this and similar threaded fastener applications.