Screw Anti-Rotation Structure With Deformable Interference Locking
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Solution Overview
Problem
Existing fastening structures using screws and nuts face issues with relative rotation prevention, leading to mechanical loosening and shaft fatigue, particularly when different lead angles and directions are involved, and existing solutions either require breaking a ratchet structure or cause permanent shear forces that can result in shaft breakage.
Innovation Solution
A relative-rotation prevention structure is implemented, featuring a screw-side deformation-capable section that presses a counterpart-side displacement section, allowing for elastic or plastic deformation, creating displacement sections that prevent relative rotation by interfering in both axial and radial directions, and includes features like tapered surfaces and stoppers to manage interference distances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a ratchet structure is used to prevent relative rotation of female threaded bodies, then relative rotation in the loosening direction is restricted, but the structure must be broken to loosen the fastening
Solution Approach 1:
The screw structure is divided into multiple functional sections: a deformation-capable section with reduced rigidity that can elastically deform, and a rigid section that maintains structural integrity. This segmentation allows the deformation section to temporarily yield during tightening to prevent over-tightening, while the rigid section ensures overall fastening reliability, and the entire structure can be easily loosened without damage.
Solution Approach 2:
The rigidity parameter of the screw is changed along its length, with the deformation-capable section having lower rigidity than the rigid section. This parameter variation allows the screw to exhibit different mechanical behaviors in different sections: elastic deformation in the flexible section for protection against over-tightening, and structural stability in the rigid section for maintaining fastening strength.
2Reliability
If female threaded bodies act shear force on the male screw shaft to prevent loosening, then anti-loosening effect is achieved, but the shaft portion becomes fatigued locally and may break
Solution Approach 1:
The deformation-capable section is designed in advance to absorb and cushion the shear forces and over-tightening loads before they can reach and damage the shaft portion. This pre-positioned protective element deforms elastically under excessive load, preventing force transmission to the critical shaft area and avoiding fatigue accumulation and potential breakage.
Solution Approach 2:
The deformation-capable section acts as an intermediary element between the female threaded bodies and the shaft portion. It mediates the force transmission by deforming under load, thereby protecting the shaft from direct exposure to harmful shear forces and preventing fatigue damage while still allowing the anti-loosening function to operate.
3Reliability
If interference action is used to prevent relative rotation, then mechanical loosening prevention is achieved, but the fastening members may be damaged and cannot be separated
Solution Approach 1:
The screw structure incorporates dynamic characteristics through the deformation-capable section that can elastically deform under load. This dynamic behavior allows the structure to adapt to varying fastening conditions, providing strong interference action for loosening prevention during operation, while maintaining the ability to be separated when needed by simply loosening the fastening without causing damage.
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
This solution provides a reliable anti-loosening effect while reducing shaft fatigue and preventing relative movement between screws and other members, allowing for secure fastening without damaging the fastening members and enabling easy separation.
Implementation Method 1
the screw-side deformation-capable section presses the counterpart-side displacement section using a fastening force and thus is deformed
Implementation Method 2
allowing for elastic or plastic deformation
Data Source
AI summary
A relative rotation prevention structure for preventing relative rotation of a screw having a threaded section with respect to a counterpart member, the relative rotation prevention structure being equipped with: a counterpart-side displacement section formed in advance on the counterpart member and capable of displacement in the axial direction or the radial direction; and a screw-side deformation-capable section that is formed on the screw and deforms when pressed into the counterpart-side deformation section by means of fastening force and, due to that deformation, produces a screw-side displacement section that is displaced in the axial direction or the radial direction.