Clinch-In Fastener Tooling for Very Thin Sheets Without Surface Marks
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Solution Overview
Problem
Existing self-clinching fasteners are ineffective for very thin sheets as they require significant material thickness and cannot be installed without causing blemishes, making them unsuitable for applications like consumer electronics where material needs to be machined down and cosmetic appearance is crucial.
Innovation Solution
The development of clinch-in fasteners with a chamfered lead installation shank and a tooling system that uses wedge-shaped displacers to deform workpiece material radially onto the fastener, reducing the need for deep holes and minimizing axial force, allowing for secure fastening in very thin sheets without visible marks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional self-clinching fasteners are used, then secure fastening is achieved, but significant material thickness is required and blemishes are caused on the surface
Solution Approach 1:
The fastener design transitions from traditional axial clinching to a system where the displacer rotates around the fastener axis, moving the deformation action from the surface dimension to a rotational path that distributes stress and avoids surface marking. The displacer follows a circular trajectory around the fastener body, enabling material displacement without direct axial pressure on the cosmetic surface.
Solution Approach 2:
The displacer acts as an intermediary tool that mediates between the installation tool and the workpiece material. It captures and redirects the installation force through rotational motion, transforming direct axial compression into circumferential material flow that wraps around the fastener without marking the visible surface.
2Strength
If traditional self-clinching fasteners are used, then material is securely deformed, but deep holes are required exceeding the thin sheet thickness
Solution Approach 1:
The installation process transitions from purely axial deformation to a rotational-dimential process. The displacer rotates around the fastener, distributing the material deformation action along a circular path rather than concentrating it axially, enabling effective fastening in shallower holes appropriate for thin sheets.
Solution Approach 2:
The displacer is designed to rotate dynamically during installation rather than remaining stationary. This rotational motion transforms the static axial pressing action into a dynamic circumferential deformation process, allowing material to be redistributed around the fastener body without requiring deep hole penetration.
3Reliability
If axial force is applied to install fasteners, then fastening is achieved, but visible marks are created on the cosmetic surface
Solution Approach 1:
The force application transitions from direct axial compression to rotational torque. The displacer rotates around the fastener, converting the installation force into a tangential action that moves material along the fastener body rather than pressing it axially against the cosmetic surface, thereby preventing visible marks.
Solution Approach 2:
Instead of pressing material axially from the cosmetic surface side, the system inverts the approach by rotating the displacer around the fastener to draw material up the sides and around the body, achieving fastening through circumferential material flow rather than direct surface compression.
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
This solution enables the secure fastening of very thin sheets with minimal material deformation and no visible blemishes, reducing installation costs and improving the aesthetic appeal of consumer electronics by allowing fasteners to be clinched in shallow holes, thus addressing the limitations of traditional self-clinching fasteners.
Implementation Method 1
the force is applied by a spring-loaded plate within an installation tool
Implementation Method 2
the installation tool rotationally presses material surrounding the hole and deforms it onto a top surface of the shank to clinch the fastener
Implementation Method 3
preferred embodiments of the fastener have a lead installation shank that has a chamfered lead surface and an outer diameter that interferes slightly with the side of the hole
Data Source
Figure 1~3
Figure 4~5c
Figure 6~8
AI summary
A clinch-in fastener (11) with a cylindrical body (13) having a top (13a), a bottom (13c), sides and an axial internal bore (12). The fastener has a single shank (15) at the bottom end of the body having a top surface (17) orthogonal to the bore and a chamfer tapering to the bottom of the body. The top surface of the shank is adapted for receiving the cold flow of material surrounding a receiving hole (23) of a workpiece (21). A fastener installation tool (20) has a tip (40) with a distal end face (24c) with at least one arcuate displacer (27) adapted for deforming a workpiece as the tool rotates and is pressed against the workpiece. A bore (30) within the tip holds a fastener (11) installed by the tool. The displacer is vertically and radially tapered along an arcuate ridge centered about the axial bore.