Cam Locking Fastener Assembly for Vibration Loosening Resistance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing bolted joints are prone to loosening due to vibration and cyclic loading, which can lead to rotary loosening of threaded fasteners, as conventional cam locking mechanisms have limitations in load capacity and displacement relative to each other during tightening and loosening.
Innovation Solution
The implementation of cam locking components with inter-engageable surface configurations featuring ramps and shoulders, where the axial rise of each shoulder is greater than the thread pitch and the slope angle of each ramp is equal to or greater than the thread lead angle, counteracting rotary loosening by forming a holding force that resists loosening forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional cam locking mechanisms with inter-engageable inclined surfaces are used, then loosening resistance is improved, but load capacity is limited due to the acute angle configuration and rotational displacement requirements
Solution Approach 1:
The patent changes the geometric parameters of the cam interface by using a rounded shoulder with axial thickness greater than thread pitch and a ramp slope angle equal to or greater than the thread lead angle. This parameter optimization allows the cam mechanism to achieve both high loosening resistance and high load capacity simultaneously, resolving the contradiction between reliability and strength.
2Reliability
If the cam surfaces have continuous undulating contour with numerous shallow saw tooth serrations, then loosening direction override is improved, but the configuration limits load capacity and requires rotational displacement
Solution Approach 1:
The patent applies curvature by rounding the shoulder inwardly near the base and outwardly near the crest, creating a smooth cam interface without sharp angles or serrations. This curved configuration eliminates the need for rotational displacement while maintaining superior loosening resistance and significantly increasing load capacity compared to conventional serrated cam surfaces.
3Reliability
If axial thickness of shoulder is greater than thread pitch with slope angle equal to or greater than thread lead angle, then holding force against loosening is improved, but device complexity increases
Solution Approach 1:
The patent merges the cam locking function with the fastener structure itself by integrating the rounded shoulder and ramp directly into the fastener body. This integration achieves high holding force through optimized geometric parameters while avoiding the complexity of separate cam mechanisms or multiple component assemblies.
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 solution effectively increases preload and load capacity, maintaining the fastener's integrity by resisting rotary loosening and accommodating elongation, while visual indicators of loosening allow for timely corrective action.
Implementation Method 1
The ramp inclines between the base and the crest at a slope angle to the plane. The slope angle is equal to or greater than the thread lead angle.
Data Source
AI summary
A fastener includes a shank and an annular body. The shank is arranged about an axis of rotation and includes an external thread having a thread pitch and a thread lead angle to a plane normal to the axis of rotation. The annular body includes an annular face and a cam annular face. The annular body is received about the shank and arranged about the axis of rotation. The cam annular face includes a ramp and a shoulder. The shoulder includes a base, a crest, and an axial thickness extending from the base to the crest. The axial thickness is greater than the thread pitch. The ramp inclines between the base and the crest at a slope angle to the plane. The slope angle is equal to or greater than the thread lead angle.