Progressive Thread Fastener for Even Clamp Load Distribution
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Solution Overview
Problem
Threaded fasteners experience loosening and fatigue due to ambient temperature fluctuations, vibration, and load variations, leading to a decrease in clamping force over time, which affects the retention of clamp load in assembled joints.
Innovation Solution
A novel threaded fastener with an asymmetrical helical thread profile, featuring progressively increasing axial displacement of the pressure flank and decreasing axial displacement of the non-pressure flank, ensuring even clamping force distribution along its axis, achieved through a progressive relief relationship that maintains uniform load distribution and constant thread volume.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional symmetrical helical thread profile is used, then the fastener can be easily manufactured with standard threading processes, but the clamping force becomes unevenly distributed along the thread length, leading to loosening and fatigue under vibration and temperature fluctuations
Solution Approach 1:
The patent applies asymmetry by modifying the conventional symmetrical helical thread profile to create an asymmetrical thread form with different flank angles. The pressure flank (load-bearing side) has a different angle than the non-pressure flank, allowing the thread to distribute clamping force more evenly along its length while resisting loosening under vibration and temperature variations
Solution Approach 2:
The patent applies local quality by varying the thread profile parameters (flank angles, pitch, depth) at different locations along the thread length. The pressure flank angle is optimized in specific regions to control load distribution, with the thread geometry changing progressively from the root to the tip of the fastener to maintain even stress distribution
2Reliability
If the thread profile is modified to achieve even load distribution, then clamp load retention improves, but the manufacturing process becomes more complex and difficult to produce
Solution Approach 1:
The patent applies parameter changes by systematically varying thread geometry parameters (flank angles, pitch, depth) along the length of the fastener. The pressure flank angle is progressively modified from the root to the tip, with specific angular values defined at different positions to achieve even load distribution while maintaining manufacturability through controlled parameter transitions
Data Source
AI summary
A novel threaded fastener is provided having an elongated shank portion with a first end and a second end opposed to the first end, and a helical thread in the form of a continuous helical ridge that is arranged on an external surface of the shank portion. The helical thread includes an asymmetrical threaded portion that has a progressively increasing axial displacement of a pressure flank of the helical thread between the first end and the second end of the shank portion, and a progressively decreasing axial displacement of a non-pressure flank of the helical thread between the first end and the second end of the shank portion. When assembled, the novel threaded fastener has a clamping force distribution that is evenly distributed on the helical threads along its axis in the direction of force transmission reducing the risk of self-loosening and increasing fatigue resistance.