Self-Drilling Fastener Structure for Multi-Layer Gap 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 design featuring a shank with distinct portions, including a transition area and flutes, where the thread formation does not engage the outermost layer until the flutes fully drill through the innermost layer, ensuring complete drilling before threading, made from low carbon steel with case hardening and a suitable coating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the thread formation engages the outermost layer early during drilling, then the fastener can secure layers together, but the outermost layer separates undesirably and the drill tip may break
Solution Approach 1:
The shank is divided into four distinct portions (first, second, third, and fourth shank portions) with different functions. The thread formation is applied only to the second shank portion, while the fourth shank portion contains the drill tip and flutes for drilling through all layers first. This segmentation allows the drilling and threading functions to be separated in sequence, preventing layer separation and drill tip breakage.
Solution Approach 2:
The drill tip and flutes on the fourth shank portion perform the drilling action first to create holes through all layers before the thread formation on the second shank portion engages the outermost layer. This preliminary drilling action ensures that all layers are penetrated completely before threading begins, preventing the harmful effects of premature thread engagement.
2Strength
If the fastener is designed for enhanced pull-out strength and shear strength in multiple layers, then connection reliability improves, but the structural complexity of the shank increases
Solution Approach 1:
The shank is segmented into four portions with distinct functions: the first shank portion transitions from the head, the second shank portion carries the thread formation for engagement, the third shank portion is a transition area, and the fourth shank portion contains the drill tip and flutes. This segmentation allows each portion to be optimized for its specific function while contributing to overall strength enhancement.
Solution Approach 2:
Different portions of the shank have different properties optimized for their specific functions. The second shank portion has thread formation for engagement and strength, while the fourth shank portion has drill tip and flutes for drilling. The third shank portion serves as a transition area. This local differentiation of properties allows the fastener to achieve enhanced pull-out and shear strength without unnecessary overall complexity.
Data Source
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AI summary
A self-drilling self-tapping fastener for connecting more than two objects such as more than two layers of panels.