Double Flush Clinch Stud for Metal Sheet Joining
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Solution Overview
Problem
Existing methods for securing metal sheets face-to-face, such as rivets and spot welds, often result in an unacceptable aesthetic appearance, are not effective for thin or dissimilar materials, and lack the feature of providing a flush finish and rotation capability.
Innovation Solution
A clinch-type fastener with adjacent fastening means of differing diameters is used, allowing for a single pressing operation to secure two metal sheets with a flush attachment and pivot feature without the need for welding or adhesives, featuring a shank with undercuts and displacers to ensure a strong and flush joint.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If spot welds are used to fasten metal sheets, then the sheets are securely joined, but weld scale is left on the surface and the appearance is unacceptable
Solution Approach 1:
The patent replaces the thermal welding process with a mechanical clinching process. The clinch stud is inserted through both sheets and deformed to create interlocking undercuts that mechanically secure the sheets together, eliminating the need for heat and preventing weld scale formation.
Solution Approach 2:
The patent changes the fastening mechanism from thermal bonding to cold mechanical deformation. By using a pressing operation to deform the clinch stud and create undercuts, the process avoids the harmful thermal effects of welding while maintaining strong joint strength.
2Strength
If rivets are used to fasten metal sheets, then the sheets are securely joined, but the finish is not flush with the sheet surface
Solution Approach 1:
The clinch stud is divided into functional segments: a head portion that provides a flush finish on the first sheet, a shaft portion with undercuts that mechanically interlock with both sheets, and a tail portion that deforms to secure the second sheet. This segmentation allows the head to remain flush while the undercuts provide strong mechanical bonding.
3Strength
If adhesives or bonding agents are used to join metal sheets, then the sheets are joined together, but the process is messy and costly
Solution Approach 1:
The patent replaces chemical bonding with mechanical bonding. The clinch stud creates physical interlocks through its undercuts that deform the sheet material, providing a clean, mechanical alternative to messy adhesives while reducing cost by eliminating bonding agent materials.
4Productivity
If a single pressing operation is used to install the clinch stud, then installation efficiency is improved, but the fastener must accommodate different diameters for dual-sheet attachment
Solution Approach 1:
The clinch stud shaft is segmented into two distinct undercut regions with different diameters. The first undercut has a larger diameter to engage the first sheet, while the second undercut has a smaller diameter to engage the second sheet. This segmentation enables dual-sheet attachment in a single pressing operation despite the structural complexity.
5Adaptability or versatility
If the Dupree fastener is modified to permit rotation by removing a knurl, then rotation capability is added, but the fastener significantly weakens and fails after numerous cycles
Solution Approach 1:
The clinch stud maintains knurls or surface features in specific locations to provide rotation capability while preserving structural integrity. The undercuts are strategically positioned and sized to allow controlled rotation without compromising the mechanical interlock strength, enabling both adaptability and reliability.
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 provides a strong, flush attachment with high pushout strength and allows for rotation, while avoiding the drawbacks of weld scales and adhesive messes, enabling efficient installation in various patterns and with minimal sheet thickness requirements.
Implementation Method 1
double flush attachment is provided without the need for the heat of welding or the mess and expense of bonding adhesives, or deformation of the surface of the sheets being bonded
Data Source
AI summary
A double flush clinch stud includes adjacent clinch means of different diameters with planar end surfaces. The stud may be employed in forming an assembly wherein two metal sheets are joined in face-to-face contacting relationship. This assembly can provide a flush attachment on the outside surfaces of both sheets when the length of the stud is equal to the combined widths of the sheets. In an alternative embodiment, the top undercut groove can be adapted to be underfilled with the material of the top sheet. In this alternate configuration, the top sheet is effectively constrained between the head of the fastener and the second sheet while permitting the top sheet to pivot with respect to the second sheet.