Clinch Broach Fastener for Flush Metal Non-Metal Joints
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Solution Overview
Problem
Existing fastening methods, such as rivets and inserts, fail to provide a flush finish when joining two sheets of different materials and are limited by the need for materials capable of cold flow deformation, and they often leave protrusions or require messy bonding agents.
Innovation Solution
A clinch-type fastener with a displacer head, undercut groove, and broaching teeth that can be installed into both metal and non-metallic sheets, allowing for a flush joint without protrusions or bonding agents, and can be used in blind holes for a clean finish.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If rivets are used to fasten two sheets together, then the fastening strength is sufficient, but the aesthetic appearance deteriorates due to protrusions on the surface
Solution Approach 1:
The fastener is segmented into distinct functional zones: a head portion for flush surface contact, an undercut groove for material deformation, and broaching teeth for mechanical interlocking. This segmentation allows each zone to perform its specific function while achieving both strength and aesthetic appearance.
Solution Approach 2:
The fastener transitions from a two-dimensional surface attachment to a three-dimensional embedded structure. The broaching teeth extend axially into the sheet material, creating interlocking engagement that provides strength while the head remains flush with the surface for aesthetic appearance.
2Shape
If inserts are used to provide a flush finish, then the surface appearance is improved, but the material selection is limited to materials capable of cold flow deformation
Solution Approach 1:
The fastening mechanism changes from relying on material cold flow properties to using mechanical deformation through broaching teeth. This parameter change allows the fastener to work with materials that have varying degrees of cold flow capability, including plastics and composite materials that cannot be cold-formed.
Solution Approach 2:
The invention replaces the cold flow deformation mechanism with a mechanical broaching and interlocking system. The broaching teeth physically cut and interlock with the sheet material, eliminating the need for material plasticity and expanding compatibility to brittle and rigid materials.
3Shape
If bonding agents such as epoxies are used to join sheets, then the flush finish is achieved, but the process becomes messy and costly
Solution Approach 1:
The fastener creates its own locking mechanism through the broaching teeth that deform and interlock with the sheet material during installation. This self-service feature eliminates the need for separate bonding agents, simplifying the manufacturing process and reducing costs.
Solution Approach 2:
The invention extracts and eliminates the bonding agent from the fastening system, replacing it with a purely mechanical interlocking mechanism. This removal of chemical adhesives simplifies the process, eliminates messiness, and reduces material costs.
4Strength
If rivets are installed, then the fastening function is achieved, but anti-rotation capability is not provided
Solution Approach 1:
The broaching teeth are arranged asymmetrically around the fastener shaft, creating a non-uniform engagement pattern with the sheet material. This asymmetry provides mechanical keys that prevent rotational movement, adding anti-rotation capability to the fastening function.
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
Effectively locks two sheets together with a flush finish, providing anti-rotation and eliminating the need for rivet protrusions or messy bonding agents, suitable for various material combinations and installation configurations.
Implementation Method 1
the materials with which the Dupree insert may be used are limited to those capable of cold flow deformation when the insert is applied under high pressure
Implementation Method 2
the joinder to the fastener is accomplished by the deformation of the sheets
Data Source
AI summary
A connector insert is installed into two panels, one non-metallic and one metal, effectively locking them together and finishing flush with the surfaces of each panel. Both sheets have aligned apertures through which the connector is installed. The connector is a clinch-type fastener including a shank having a displacer head at one end and an endface at the opposite end, the head having a planar top surface and being the largest diameter of the fastener. An undercut groove is located on the shank immediately below the head and a plurality of axially-extending broaching teeth on the shank are located immediately below the undercut groove. The diameter of the broaching teeth is greater than the diameter of the undercut groove but less than the diameter of the head. At the end of the shank is a planar endface immediately below the broaching portion.