Ribbed Threaded Fastener Head for Over-Tightening Feedback
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Solution Overview
Problem
Threaded fasteners fail due to excessive torsional stresses caused by high torque from improved power driving tools, leading to over-tightening and breakage of the shank, particularly at the head-shank junction.
Innovation Solution
The threaded fastener design includes a head with radially arranged ribs that create frictional torsional resistance, informing the operator when sufficient engagement is achieved, preventing further over-tightening and reducing the likelihood of shank failure by transferring torque back through the tool.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high torque power driving tools are used to drive threaded fasteners, then driving efficiency and tightening force are improved, but excessive torsional stresses cause shank breakage and fastener failure
Solution Approach 1:
The fastener is divided into functionally distinct zones: a head portion with ribs for torque management and engagement, a shank portion for thread engagement, and a transition zone with optimized geometry. This segmentation allows each portion to handle specific stress types, preventing catastrophic failure.
Solution Approach 2:
The head includes radially arranged ribs with specific geometric features (leading faces, trailing faces, apexes) that create localized frictional resistance. This local quality modification enables controlled torque transfer and prevents excessive stresses from propagating through the entire fastener.
2Reliability
If continuous tightening is applied to ensure secure attachment, then fastening reliability is improved, but over-tightening causes torsional failure at the head-shank junction
Solution Approach 1:
The ribs in the head portion provide tactile and mechanical feedback during tightening. As the ribs engage the substrate or workpiece, they create frictional resistance that signals adequate engagement, preventing operators from applying excessive torque that would cause shank failure.
Solution Approach 2:
The ribbed head structure preemptively counteracts excessive tightening forces through frictional resistance and torque redistribution. This preliminary anti-action prevents the shank from experiencing damaging torsional stresses before they can cause failure.
3Ease of manufacture
If the head design is simplified for ease of manufacture, then manufacturing cost is reduced, but torque management and over-tightening prevention capabilities are compromised
Solution Approach 1:
The rib geometry parameters (height, spacing, angle, thickness) can be adjusted based on fastener size and application requirements. This parametric approach allows the same basic ribbed head design to be manufactured across different fastener specifications while maintaining torque management functionality.
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 ribbed design effectively reduces the risk of torsional failure and over-tightening, ensuring secure attachment without breaking the fastener, thereby enhancing the reliability and durability of threaded fasteners.
Implementation Method 1
The ribs are shaped to frictionally engage a surface of a first object being attached to a second object such as a substrate
Data Source
AI summary
Various embodiments provide a fastener including a head, a shank connected to the head and having a tip, one or more helical thread formations extending outwardly from the shank, and wherein a bottom portion of the head includes a plurality of ribs that extend towards the tip of the shank and that are shaped to abruptly frictionally engage a surface of a first object being attached to a second object to create an immediate frictional torsional resistance of a desired force level to the tightening of the fastener. This frictional resistance is provided back to the tightening tool to inform the operator of the tightening tool that the head of the fastener has sufficiently engaged the first object and that further tightening or clockwise rotation of the fastener is unnecessary.