Thread Root Dented Profile for Anti-Loosening Fasteners
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Solution Overview
Problem
Existing fastening members with thread structures face issues such as insufficient loosening prevention, difficulty in applying thick plating like hot-dip galvanizing, and poor workability due to initial loosening, which affects the reliability and fatigue strength of bolts.
Innovation Solution
A fastening member with a thread structure featuring a pressure flank surface on the thread crest and a dented side surface on the thread root, allowing for elastic deformation and increased friction force, thereby preventing loosening and enabling thick plating without compromising the loosening prevention effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pressure flank surface is provided on the male thread to positively press the female thread, then loosening prevention is improved, but elastic deformation capability is insufficient and friction force is not large enough
Solution Approach 1:
The patent applies local quality by providing a dented portion specifically at the root of the screw thread, creating a localized region with different mechanical properties. This dented portion has reduced thickness compared to the basic profile, enabling it to elastically deform under load while the rest of the thread structure maintains its strength. The local modification allows the thread root to act as a spring element that generates friction force between mating threads.
Solution Approach 2:
The patent changes the geometric parameter of the thread root by creating a dented portion with reduced thickness. This parameter change transforms the rigid thread structure into one with elastic compliance at the root, allowing the thread to deform and generate friction force while maintaining the pressure flank surface for positive pressing action.
2Reliability
If a gap is provided between flank surfaces to permit elastic deformation, then loosening prevention is improved, but the gap is insufficient for sufficient elastic deformation
Solution Approach 1:
Rather than providing a gap throughout the thread structure, the patent applies local quality by creating a dented portion specifically at the thread root. This localized thinning creates the necessary elastic deformation capability without compromising the overall structural integrity and dimensional stability of the fastening member.
3Reliability
If flanks are elastically deformed by providing a slit in the thread crest, then loosening prevention is improved, but the deformation is limited to slit depth and friction force is not large
Solution Approach 1:
Instead of creating elasticity by removing material (slit) from the thread crest as in prior art, the patent inverts the approach by creating a dented portion at the thread root. This inverted location provides better leverage for elastic deformation and generates larger friction force between the mating threads while maintaining structural integrity.
4Reliability
If resin coating layer is formed on screw thread to prevent loosening, then loosening prevention is improved, but repeated coating is troublesome and torque management becomes complicated
Solution Approach 1:
The patent implements self-service by designing the fastening member with an inherent elastic deformation capability through the dented portion at the thread root. This structural feature automatically generates friction force to prevent loosening without requiring external coatings or additional tightening operations, making the fastening member self-sufficient for loosening prevention.
5Reliability
If male thread and female thread are hot-dip galvanized with thick plating, then corrosion resistance is improved, but the threads may become unable to fit each other
Solution Approach 1:
The patent applies preliminary action by pre-forming the dented portion at the thread root during manufacturing, before galvanizing. This预先 created elastic deformation capability ensures that even after thick plating is applied, the fastening member can still achieve proper engagement and elastic deformation, maintaining thread compatibility while gaining corrosion resistance.
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 design significantly enhances loosening prevention, improves workability by eliminating the need for additional tightening, and maintains the loosening prevention effect even after repeated use, while allowing for thick plating and improved fatigue strength.
Implementation Method 1
at least one side surface of the lower portion is provided inwardly of an extension line of a corresponding flank surface... allowing for elastic deformation and increased friction force
Implementation Method 2
pressure flank surface formed in the upper portion is provided on a side of a seat surface with respect to a pressure flank surface of a basic profile... increased friction force, thereby preventing loosening
Data Source
AI summary
To provide a fastener having a high anti-loosening effect. A fastener has a thread structure including an upper portion of the crest and a bottom portion at the groove. The upper portion has a load flank surface inclined from the standard load flank surface toward the fastener seat while the bottom has an undercut on at least one of the groove side lower than the extension of the corresponding flank surface.