Helical Thread Insert Nut Locking for Reusable Torque Retention
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Solution Overview
Problem
Existing locking fasteners, particularly those using resilient inserts like Vespel™, are expensive, difficult to install, prone to damage, and have limited reuse and torque consistency, especially in environments with varying temperatures and vibrations, and they do not provide sufficient strength or reliability for applications like aircraft components.
Innovation Solution
A new type of nut featuring a helical thread insert and a retained clasp, such as the Lockone clasp, which is integrated with the nut body and can be secured by retainers, providing a positive locking mechanism that enhances the strength and torque consistency of the fastener system without the limitations of traditional resilient inserts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If resilient inserts like Vespel™ are used in locking fasteners, then locking capability is achieved, but cost increases and installation becomes difficult
Solution Approach 1:
The patent replaces expensive resilient inserts with a simple metal cap and cotter pin system that is cheaper, easier to install, and can be reused. The cap and pin are standard hardware components rather than proprietary resilient materials, eliminating the need for expensive Vespel™ inserts while maintaining locking functionality.
Solution Approach 2:
The locking function is divided into separate components: the cap that covers the castellated nut and the cotter pin that secures the fastener. This segmentation allows each component to be optimized independently and simplifies installation compared to a single integrated resilient insert.
2Reliability
If resilient inserts are used for locking, then torque retention is achieved, but torque consistency deteriorates over multiple cycles
Solution Approach 1:
The metal cap and cotter pin system maintains consistent torque retention across multiple cycles without the degradation seen in resilient inserts. The rigid metal components do not soften or deform over time like resilient materials, ensuring consistent torque values throughout the fastener's service life.
3Reliability
If proprietary resilient materials are used, then locking performance is improved, but cost increases
Solution Approach 1:
The patent eliminates expensive proprietary resilient materials and uses standard, inexpensive metal components (cap and cotter pin) to achieve the same locking performance. This substitution dramatically reduces material costs while maintaining or improving locking reliability.
4Reliability
If resilient inserts are used, then initial locking is achieved, but reuse capability is limited
Solution Approach 1:
The metal cap and cotter pin system can be easily removed, inspected, and reused multiple times without degradation. Unlike resilient inserts that can be damaged during installation and cannot be reused, these simple metal components maintain their locking capability across multiple installation cycles.
Data Source
AI summary
A fastener system including a nut body and a helical thread insert. The nut body having an internally threaded bore containing a plurality of bore threads, and at least one bore obstruction. The helical thread insert formed to create a plurality of internal HTI threads and a plurality of external HTI threads, with the helical thread insert received in the internally threaded bore and not occupying all of the plurality of bore threads, and having its movement limited by the bore obstruction. The helical thread insert having threads with both circular end profiles and a non-circular end profile. The non-circular end profile including at least three straight segments, and located between circular threads.