Lock Nut With Helical Wire Insert for Consistent Torque Control
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Solution Overview
Problem
Current locking fasteners in the aircraft industry are expensive, difficult to install, prone to damage, and have limited reuse and torque consistency, with existing resilient inserts like Vespel being costly and inefficient in varying temperatures and vibration.
Innovation Solution
A torque control fastener system featuring a serrated nut with a helical wire insert that provides improved torque control and locking, using a serrated cap and nut combination with a helical thread insert that expands to resist reverse torque, allowing for precise torque application and consistent performance across cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If resilient inserts like Vespel are used for locking fasteners, then locking torque is provided, but the inserts are expensive and difficult to install
Solution Approach 1:
The patent replaces expensive resilient inserts with a disposable serrated cap that is crimped onto the nut. The cap is designed to be installed once and discarded after a limited number of reuse cycles, eliminating the need for expensive proprietary materials while maintaining locking functionality.
Solution Approach 2:
The patent removes the resilient insert component entirely from the fastening system. Instead of using an insert that requires insertion into the nut, the solution uses a serrated cap that crimps over the external surfaces of the nut, eliminating the complex installation process of inserting and securing resilient materials.
2Reliability
If resilient inserts are used, then locking is provided, but the inserts are easily damaged during installation
Solution Approach 1:
The serrated cap is designed as a disposable component that absorbs installation damage. Rather than protecting a valuable resilient insert, the cap itself is made from durable but replaceable material that can withstand installation stresses and be discarded if damaged, eliminating the risk of damaging expensive inserts.
Solution Approach 2:
The locking function is segmented into the serrated cap that provides the locking interface and the nut that provides the threading. This separation allows the cap to be optimized for locking durability while being replaceable if damaged, rather than requiring the entire fastening system to be replaced.
3Reliability
If resilient inserts are used, then locking torque is achieved, but reuse is limited
Solution Approach 1:
The serrated cap is designed for limited reuse cycles (e.g., 3-5 times) and then discarded. This disposable approach eliminates the degradation issues of resilient inserts over many cycles, as each new cap provides fresh locking surfaces. The low cost of the cap enables replacement rather than reuse, maintaining consistent locking performance.
Solution Approach 2:
The patent implements a discard-after-use strategy where the serrated cap is removed and discarded after a predetermined number of reuse cycles. This prevents the accumulation of wear and damage that limits resilient insert reuse, while the low cost of the cap makes frequent replacement economically viable.
4Reliability
If resilient inserts are used, then locking is provided, but torque consistency varies with temperature and vibration
Solution Approach 1:
The patent changes the material parameters from temperature-sensitive resilient polymers to temperature-stable metals or metal alloys. The serrated cap and nut are made from materials whose mechanical properties remain consistent across a wide temperature range and under vibration, eliminating the torque variability inherent in resilient insert systems.
Solution Approach 2:
The patent uses composite or dissimilar material constructions, such as an aluminum nut with a stainless steel serrated cap, or a polymer nut with a metal insert. This combination provides the stability of metal materials for the locking interface while allowing the base material to be optimized for other properties like weight or corrosion resistance.
5Reliability
If proprietary Vespel material is used, then locking torque is provided, but cost is high due to OEM approval requirements
Solution Approach 1:
The patent replaces proprietary expensive materials with inexpensive disposable serrated caps made from common metals or alloys. These caps do not require expensive OEM approval processes because they are discarded after limited use and can be manufactured by any supplier meeting basic specifications, dramatically reducing material and certification costs.
Solution Approach 2:
Instead of using a single proprietary material specification, the patent allows multiple material compositions to achieve the same locking function. Any metal or alloy that can be formed into a serrated cap geometry provides the required locking torque, enabling competition and cost reduction without sacrificing performance.
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 system reduces costs, improves assembly efficiency, enhances maintainability, and provides consistent torque values over multiple cycles, exceeding traditional fastener performance in strength and durability.
Implementation Method 1
a helical wire insert that expands to resist reverse torque
Implementation Method 2
serrated nut with a helical wire insert that provides improved torque control and locking
Data Source
AI summary
A torque control fastener system having a fastener nut, a helical wire insert, and a shaft, where the nut and helical wire insert have unique hardness and coefficient of thermal expansion relationships that produce improved performance.