Dual-Threaded Double-Nut Fastening With Spring Washer Against Vibration
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Solution Overview
Problem
Existing fastening structures with double nuts and dual-threaded screws face loosening issues under vibrational loads, particularly in applications like railway bridges, where periodic inspections are necessary to prevent loosening, and existing solutions do not effectively address strong fastening requirements in large-scale structures.
Innovation Solution
A fastening structure with dual-threaded screws that includes a spring-shaped or dish spring washer between the nuts, where the second thread has a lead that is an integer number of times the pitch of the first thread, ensuring that the axial force is maintained and the fastening is not loosened by external vibrations by tightening only the outer nut.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If double nuts are used with dual-threaded screw for fastening, then fastening operation is simplified and only tightening with metric coarse thread nut is necessary, but nuts may loosen under severe vibrational loads
Solution Approach 1:
A spring washer is introduced as an intermediary component between the inner nut and outer nut. The spring washer deforms elastically under compression to generate a reactive force that prevents the inner nut from loosening under vibrational loads, while allowing the outer nut to remain easily tightenable without requiring complex tightening-back operations.
Solution Approach 2:
The spring washer is pre-compressed between the inner nut and outer nut during assembly, storing elastic energy beforehand. This pre-compression creates a cushioning effect that counteracts vibrational forces before they can cause loosening, ensuring the inner nut remains securely positioned without requiring periodic inspections or adjustments.
2Reliability
If spring washer is used to prevent loosening, then loosening resistance is improved, but axial force is lowered to a remarkable extent causing nut to loosen under vibrational load
Solution Approach 1:
The spring washer and dual-threaded screw structure are merged into a unified fastening system. The spring washer's elastic reaction force works in conjunction with the dual-threaded screw's mechanical advantage to maintain both sufficient axial force for secure fastening and enhanced loosening resistance under vibrational loads.
Solution Approach 2:
The spring washer's elastic properties are utilized to dynamically adjust the force distribution. Under static conditions, the spring washer maintains adequate axial force; under vibrational conditions, the spring washer's elastic deformation absorbs shock loads, preventing the axial force from dropping to levels that would cause loosening.
3Reliability
If periodic inspections are conducted to prevent loosening, then loosening prevention is achieved, but maintenance time and operational disruption increase
Solution Approach 1:
The spring washer creates a self-service fastening system that automatically maintains its own tightness through elastic recovery. When the inner nut experiences any tendency to loosen under vibration, the compressed spring washer generates a reactive force that pushes the inner nut back into its proper position, eliminating the need for periodic manual inspections or adjustments.
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 proposed structure securely maintains axial force between the nuts and the fastened body under vibrational loads, preventing loosening and eliminating the need for periodic inspections, as the spring washer stores elastic energy to maintain the clamping force.
Implementation Method 1
the spring washer stores elastic energy to maintain the clamping force
Data Source
AI summary
Fastening art with double nuts for a dual-threaded screw structure is provided, in which loosening is not created even if the structure is subjected to vibration. A spring washer is caused to intervene between the nuts, when double nuts of an inner nut and an outer nut are screwed onto a thread portion on which dual-threaded screw is formed. Only by tightening the outer nut, also the inner nut is tightened and the spring washer is compressed. Both axial force for clamping the fastened member and axial force between the nuts can be secured with the spring washer, so that loosening does not occur easily.