Interrupted Scraping Rib Screw for High Pull-Out Wood Fastening
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Solution Overview
Problem
Conventional wood screws lack sufficient pull-out strength and manufacturability, with existing screws either requiring pre-drilling or relying solely on thread anchoring in wood substrates for holding power.
Innovation Solution
A screw design featuring axially extending shank sections with radial threads, a screw tip section, and strategically positioned scraping edges that extend radially to cut and widen holes in the substrate, allowing for self-tapping or self-drilling insertion without pre-drilling, while minimizing material removal to enhance pull-out forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional wood screws rely solely on thread anchoring in pre-drilled holes, then the screw can be easily inserted, but the pull-out strength is insufficient
Solution Approach 1:
The screw is divided into functionally distinct sections: a tip section with first scraping edges for initial material removal and hole formation, and a shank section with second scraping edges for additional material removal and enhanced anchoring. This segmentation allows each section to perform its specific function optimally, achieving both easy insertion and high pull-out strength.
Solution Approach 2:
Different scraping edges are positioned at specific locations along the screw length. The first scraping edges are located at the tip section to facilitate initial insertion, while the second scraping edges are positioned in the shank section to enhance anchoring. This local differentiation of scraping functions optimizes both insertion ease and pull-out resistance.
2Ease of operation
If scraping edges continuously remove material along the screw length, then insertion is facilitated, but excessive material removal reduces pull-out force
Solution Approach 1:
The continuous scraping action is segmented into discrete sections along the screw length. The first scraping edges operate in the tip section, and the second scraping edges operate in the shank section, with gaps between them where no material removal occurs. This segmentation controls the total amount of material removed while maintaining insertion facilitation.
Solution Approach 2:
Instead of continuous material removal along the entire screw length, material removal is applied partially at specific sections. The first and second scraping edges perform partial scraping actions at designated locations, removing just enough material to facilitate insertion without excessive removal that would compromise pull-out force.
3Strength
If wood screws are driven directly into solid wood without pre-drilling, then the anchoring effect is improved, but the setting force required increases
Solution Approach 1:
The first scraping edges at the screw tip perform preliminary material removal and hole formation before the threads engage the wood. This preliminary action creates a pathway for the screw, reducing the setting force required while maintaining strong anchoring as the threads cut into the pre-prepared hole.
Solution Approach 2:
The screw function is segmented into preliminary hole formation by the first scraping edges at the tip, followed by thread cutting and anchoring by the threads and second scraping edges in the shank section. This segmentation allows the screw to progressively engage the wood, reducing initial setting force while achieving strong anchoring.
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
The screw achieves high extraction forces with moderate setting forces and improved holding power by controlled material removal, preventing excessive loosening and enhancing anchoring through frictional engagement of intermediate thread sections, thereby increasing pull-out values without additional material or complex manufacturing processes.
Implementation Method 1
at least one first scraping edge on (for example, also on, in particular only on) the screw tip section (in particular projecting radially beyond the screw tip section), and at least one second scraping edge in (for example, also in, in particular only in) a region of the shank section adjacent to the screw tip section
Implementation Method 2
enhancing anchoring through frictional engagement of intermediate thread sections
Data Source
Figure 1~3
Figure 4~6
Figure 7~8
AI summary
Disclosed is a screw (100) comprising an axially extending shaft portion (102), a screw thread (104) that is located on the shaft portion (102) and has turns (110) extending radially from the shaft portion (102), a screw tip portion (106) adjoining the shaft portion (102), at least one first scraping edge (108) on the screw tip portion (106), and at least one second scraping edge (112) in a region of the shaft portion (102) that adjoins the shaft tip portion (106); the at least one first scraping edge (108) and the at least one second scraping edge (112) are located at a distance from each other and extend in the axial direction along different zones of the screw (100).