Self-Tapping Fastener with Flat Sections for Stucco
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Solution Overview
Problem
Self-tapping fasteners face issues with thread abrasion and dust accumulation during installation in stucco, gypsum, or hard board substrates, leading to reduced pull-out resistance and incomplete thread formation due to the abrasive nature of these materials.
Innovation Solution
A self-tapping fastener with a dual thread structure and diametrically opposed flat sections that form redundant cutting threads, accommodating dust and debris until the tip pierces the substrate, ensuring effective thread formation and discharge of debris.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a self-tapping fastener is installed in stucco, gypsum, or hard board substrates with closely matched root diameter to bore diameter to achieve desirable pull-out resistance, then pull-out resistance is improved, but dust and debris accumulate during the self-tapping process causing interference with thread formation
Solution Approach 1:
The thread structure is segmented into multiple leads (primary and secondary thread leads) with different pitches. This segmentation allows different portions of the threads to perform different functions during installation, with later-formed threads providing clearance space for debris accommodation while earlier threads establish initial engagement.
Solution Approach 2:
The invention introduces a temporal dimension to thread formation by using multiple thread leads with different pitches. Threads are formed sequentially rather than simultaneously, creating a time-based progression where earlier threads establish engagement and later threads provide clearance space for debris, effectively adding a time dimension to the spatial thread structure.
2Reliability
If the self-tapping process is performed in abrasive substrates like stucco, then thread formation is completed, but the forwardmost primary thread lead portions undergo abrasion reducing their effectiveness
Solution Approach 1:
The secondary thread leads are formed ahead of the primary thread leads during the self-tapping process. This preliminary action of forming secondary threads creates a protective pathway that reduces direct abrasion on the primary thread leads, allowing the primary threads to maintain their integrity while still achieving complete thread formation in the abrasive substrate.
Solution Approach 2:
The secondary thread leads act as a cushioning layer formed beforehand that protects the primary thread leads from direct contact with abrasive substrate particles. This prior cushioning effect reduces wear on the critical primary threads while still enabling effective thread formation in hard, abrasive materials.
3Strength
If no substantial clearance is provided between root diameter and bore internal peripheral wall surface to maintain thread engagement, then pull-out resistance is improved, but dust and debris generated during tapping cannot be discharged
Solution Approach 1:
The thread engagement process is segmented into multiple phases using different thread leads. Early phases with primary threads establish strong engagement, while later phases with secondary threads create clearance space for debris discharge, effectively segmenting the engagement and clearance functions across different thread leads.
Solution Approach 2:
The pitch parameter of the threads is changed between primary and secondary thread leads. The secondary threads have different pitch characteristics that allow them to create clearance space while maintaining engagement, effectively using parameter changes to resolve the contradiction between tight engagement and debris discharge.
Data Source
AI summary
A self-tapping fastener, which has been especially constructed for use in connection with the insertion and installation thereof into stucco, gypsum, wallboard, or other hard board substrates, wherein the forward end portion of the shank portion of the self-tapping fastener is provided with a pair of diametrically opposed flat sections which effectively form at least one pair of diametrically opposed tapping threads so as to effectively perform the thread tapping process despite exhibiting some abrasion of the forwardmost threads. In addition, the flat sections also effectively define recessed pockets for accommodating any dust, particles, debris, or the like, which will be generated during the thread tapping process.