Segmented Self-Drilling Fastener for Multi-Layer Panel Joining
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Solution Overview
Problem
Existing self-drilling self-tapping fasteners face issues when connecting multiple layers of objects, particularly when there are gaps or insulations between them, leading to undesired separation of outer layers and potential drill tip breakage, with a need for enhanced pull-out strength and shear strength.
Innovation Solution
A self-drilling self-tapping fastener with a unique shank configuration, including a fourth shank portion with a drill tip and flutes, ensures that the thread formation does not engage the outermost layer until the flutes fully drill through the innermost layer, enhancing pull-out and shear strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the thread formation engages the outermost layer early during drilling, then thread engagement is achieved sooner, but the outermost layer separates undesirably and drill tip breakage occurs
Solution Approach 1:
The shank is divided into four distinct portions with different functional characteristics. The fourth portion (drill tip section) has no threads and is optimized for drilling, while the second portion has threads for engagement. This segmentation allows the drilling and threading functions to occur at different locations along the shank, preventing thread interference during the drilling phase and eliminating the contradiction between drill tip durability and thread engagement strength.
2Adaptability or versatility
If the fastener connects multiple layers with gaps or insulation, then connectivity is achieved, but layer separation and drill tip breakage occur
Solution Approach 1:
The shank is segmented into four portions with the fourth portion extending through all layers to provide continuous drilling capability. This allows the drill tip to penetrate multiple layers with gaps or insulation before thread engagement begins in the second portion, maintaining reliability while achieving multi-layer connectivity.
Solution Approach 2:
The third shank portion acts as a transition zone or intermediary between the drilling section (fourth portion) and the threaded engagement section (second portion). This transition area with reduced outer diameter allows smooth progression from drilling through multiple layers to thread engagement, preventing sudden stress transitions that could cause drill tip breakage while maintaining adaptability to various layer configurations.
3Strength
If enhanced pull-out strength and shear strength are desired, then fastener performance is improved, but the complexity of shank configuration increases
Solution Approach 1:
The shank is segmented into four portions, each optimized for specific functions. This segmentation allows enhancement of pull-out and shear strength through strategic thread placement in the second portion while maintaining drilling efficiency in the fourth portion, achieving enhanced strength without excessive complexity.
Solution Approach 2:
Different portions of the shank have different local qualities: the second portion has threads for engagement strength, the fourth portion has drill tip geometry for drilling efficiency, and the third portion has reduced diameter for transition. This local quality differentiation enhances overall fastener performance including pull-out and shear strength while keeping the overall design relatively simple.
Data Source
AI summary
A self-drilling self-tapping fastener for connecting more than two objects such as more than two layers of panels.