Ribbed Threaded Fastener Head for Over-Tightening Feedback
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Solution Overview
Problem
High-torque driving tools often cause threaded fasteners to fail due to excessive torsional stresses, leading to over-tightening and breakage of the fastener head from the shank.
Innovation Solution
The threaded fastener features a head with radially arranged ribs that create frictional resistance when engaging the substrate, providing feedback to the operator to prevent over-tightening, thereby reducing torsional stresses and the likelihood of failure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high-torque power driving tools are used to drive threaded fasteners, then the fastening strength is improved, but the threaded fastener is subjected to excessive torsional stresses causing head breakage
Solution Approach 1:
The frangible rib structure provides tactile feedback during the driving process. As the rib engages the substrate, it creates a noticeable resistance that signals to the operator when the fastener has reached proper engagement, preventing continued application of torque that would cause head breakage
Solution Approach 2:
The frangible rib acts as a predetermined weak point designed to fail before the critical fastener head-shank interface. This beforehand cushioning protects the main structural integrity by sacrificing a non-critical element first
2Force
If excessive torque is applied during fastener installation, then the fastening force is improved, but the threaded fastener fails due to over-tightening
Solution Approach 1:
The frangible rib provides operational feedback through tactile resistance during tightening. When the rib engages the substrate, it creates a noticeable increase in torque resistance that signals proper engagement, guiding the operator to stop applying force and preventing over-tightening
3Reliability
If the threaded fastener is designed with higher strength to resist torsional stresses, then the fastening reliability is improved, but the complexity of the fastener structure increases
Solution Approach 1:
The fastener head is segmented into distinct functional elements including the frangible rib, drive recess, and bearing surface. This segmentation allows each element to perform its specific function independently while maintaining overall structural simplicity
Solution Approach 2:
The frangible rib is extracted as a separate, sacrificial element from the main fastener structure. This allows the primary fastener body to remain simple while the rib provides the protective function against over-torquing
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 fastener failure by providing tactile feedback during tightening, ensuring the fastener is securely engaged without excessive torque, thus enhancing the reliability of the fastening process.
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
Figure 1
Figure 2
Figure 3A
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.