Self-Clinching Fastener Geometry for Low-Force Panel Attachment
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Solution Overview
Problem
Conventional clinch nuts require high installation force and often fail due to the stress on reflective dies, leading to reduced tooling longevity and increased production costs, while also lacking sufficient rotational and pull-through resistance for secure attachment to modern lightweight metal panels.
Innovation Solution
A self-clinching fastener design featuring a body portion with an annular-shaped surface and a punch portion with lugs, which reduces the radial footprint and eliminates the need for a reflective die by allowing the metal panel to deform efficiently, providing enhanced attachment strength and longevity of tooling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a reflective die with a ridge is used to form the mechanical interlock, then the clinch nut achieves sufficient pull-through resistance and rotational resistance, but the die member fails between 100-1,000 uses due to repeated high force application
Solution Approach 1:
The patent removes the reflective die with ridge from the system entirely. Instead of using a reflective die to form the mechanical interlock, the invention uses a flat die that simply supports the metal panel while the clinch nut's own geometry (annular groove and deformed pilot portion) creates the mechanical interlock without requiring material separation or high-force deformation by the die.
Solution Approach 2:
Conventional designs use the die to actively deform the metal panel into the clinch nut. This invention inverts the approach: the clinch nut's pre-formed geometry and material properties enable it to self-clinch to the panel with minimal die intervention, eliminating the need for the die to apply repeated high forces that cause failure.
2Strength
If twelve tons of force or more is applied to connect the clinch nut and metal panel, then sufficient mechanical interlock is achieved, but the installation force requirement increases production costs and reduces efficiency
Solution Approach 1:
The clinch nut is designed to self-clinch to the metal panel through its own geometry and material properties. The annular groove and deformed pilot portion create the mechanical interlock automatically during installation without requiring external force application by the die, eliminating the need for twelve tons or more of installation force.
Solution Approach 2:
The invention changes the installation parameters by using a flat die instead of a reflective die with ridge, which fundamentally alters the force requirements. The new design enables attachment with significantly reduced force while maintaining or improving the mechanical interlock strength through the clinch nut's optimized geometry.
3Reliability
If a reflective die with ridge is used to separate metal panels, then the mechanical interlock is formed, but the die repeatedly fails at the ridge due to stress concentration
Solution Approach 1:
The patent extracts and removes the problematic reflective die with ridge from the system. The invention replaces it with a simple flat die that provides only supportive function, eliminating the stress concentration points and structural complexity of the original reflective die design.
Solution Approach 2:
Instead of using the die to actively separate and deform the metal panel (which caused failure at the ridge), the invention inverts the approach by using the clinch nut's own geometry to create the mechanical interlock, with the die serving only as a passive support surface.
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 new design reduces installation force by up to 50% and significantly increases tooling longevity, eliminating the need for a reflective die and ensuring secure attachment to modern metal panels with improved rotational and pull-through resistance.
Implementation Method 1
The self-clinching fastener is attached to the metal substrate by a die member which forms a mechanical interlock between the self-clinching fastener and the metal substrate
Data Source
AI summary
A self-clinching fastener for attachment to a plastically deformable metal substrate includes a body portion with a central axis, the body portion has an annular-shaped surface extending in a direction perpendicular to the central axis The annular-shaped surface includes a first annular face, a second annular face, and a third annular face. The third annular face lies on an imaginary horizontal plane. A punch portion extends from the body portion. A plurality of spaced apart lugs encircle the punch portion. The first annular face extends from an outer peripheral surface of the punch portion in a radially outwards direction, and the second annular face is radially disposed between the first annular face and the third annular face. One of the lugs declines to the second annular face.