Mismatched Thread Fastener for Low-Torque Vibration Locking
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Solution Overview
Problem
Existing fastening systems fail to provide effective vibration resistance while minimizing material weight and cost, as they require significant material and torque for lock formation.
Innovation Solution
A vibration-resistant fastening system is achieved by incorporating a mismatched thread pitch between the bolt and nut, with the nut thread being either shorter or longer than the bolt thread, and utilizing a hardness gradient in the nut to concentrate clamp load and prevent dilation, allowing for lock formation at lower torque and material usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional matching thread pitch is used between bolt and nut, then proper thread engagement is achieved, but significant material and torque are required for lock formation
Solution Approach 1:
The patent applies local quality by creating a hardness gradient within the nut material, where the outer surface layer has different hardness properties than the core. This allows the nut to provide vibration resistance at the thread engagement interface while using less overall material. The selective hardness distribution optimizes lock formation characteristics without requiring uniform material throughout the entire nut structure.
Solution Approach 2:
The patent changes the pitch parameter of the nut threads to be different from the bolt threads. This pitch mismatch alters the thread engagement characteristics, enabling lock formation with reduced torque and material usage. The parameter change in thread pitch creates the desired vibration resistance while reducing the quantity of material needed compared to conventional matching pitch designs.
2Reliability
If conventional matching thread pitch is used between bolt and nut, then proper thread engagement is achieved, but higher torque is required for lock formation
Solution Approach 1:
The hardness gradient in the nut creates localized zones with optimized mechanical properties for thread engagement. The outer layer has hardness specifically tailored for lock formation, reducing the torque required while maintaining vibration resistance. This local quality optimization eliminates the need for high torque applied uniformly across the entire fastening system.
Solution Approach 2:
By changing the nut thread pitch to be mismatched with the bolt thread pitch, the patent reduces the torque required for lock formation. The pitch difference alters the engagement mechanics, allowing vibration resistance to be achieved with lower applied torque compared to conventional matching pitch systems.
3Ease of manufacture
If uniform hardness material is used for the nut, then manufacturing is simplified, but clamp load cannot be concentrated at specific points
Solution Approach 1:
The patent implements a hardness gradient where the nut material has varying hardness from the core to the outer surface. This local quality variation allows clamp load to be concentrated at specific regions, particularly at the thread engagement interface, while the manufacturing process remains relatively simple through controlled heat treatment or material selection. The gradient structure provides both manufacturing feasibility and optimized load distribution.
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 provides enhanced vibration resistance and reduced material usage by concentrating clamp load at specific points, achieving lock formation at lower torque and allowing for a more efficient and cost-effective fastening solution.
Implementation Method 1
The lock is formed by allowing the bolt thread to embed into the relatively softer nut thread
Data Source
AI summary
A fastener including a bolt having an elongated shank having a first end, a second end opposite the first end, and a threaded portion having an external bolt thread, the bolt thread including a bolt pitch. The fastener includes a nut having a first end, a second end opposite the first end of the nut, and an internal nut thread extending between the first and second ends of the nut and adapted to engage threadedly the bolt thread of the bolt. The nut thread includes a nut pitch and a hardness that changes gradationally between the first and second ends of the nut. The bolt pitch of the bolt thread of the bolt is mismatched with the nut pitch of the nut thread of the nut.