Double-Thread Nail Screw for High Pullout Without Wood Splitting
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing nail screws tend to split wood when driven in, leading to undesirable splitting and reduced pullout force, and are not easily unscrewed from connected components.
Innovation Solution
A nail screw design featuring a double thread with specific angle configurations, a blunt conical tip, and self-cutting thread flanks, allowing for increased pullout force, reduced splitting, and easier unscrewing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a single threaded nail screw is used, then the insertion force is sufficient, but the pullout force is reduced and wood splitting occurs
Solution Approach 1:
The thread is divided into two separate threads (first thread and second thread) with different flank angles. The first thread has a first grip flank angle optimized for pullout resistance, while the second thread has a second grip flank angle that reduces wood splitting. This segmentation allows each thread to specialize in different functional requirements.
Solution Approach 2:
Different portions of the thread structure have different local properties. The first thread portion has specific insertion flank and grip flank angles optimized for one function, while the second thread portion has different angles optimized for another function. This local quality variation allows the nail screw to simultaneously achieve high pullout force and prevent wood splitting.
2Ease of operation
If a standard thread design is used, then the nail screw can be driven in quickly, but it cannot be easily unscrewed from connected components
Solution Approach 1:
The nail screw design allows for dynamic adjustment of the connection. The specific thread geometry with different grip flank angles creates a connection that is stable during service but can be easily loosened when needed. The self-cutting thread flanks enable the threads to cut into the material during installation for secure binding, but allow easy backout during removal.
3Productivity
If a sharp conical tip is used, then the nail screw can be driven in easily, but the wood splits undesirably
Solution Approach 1:
The tip angle parameter is specifically optimized to a range of 80-120 degrees. This parameter change from sharper tips balances the competing requirements of easy driving (which requires sharpness) and wood splitting prevention (which requires bluntness). The specific angle range achieves both objectives simultaneously.
Data Source
AI summary
A nail screw, in particular for connecting facade boards or terrace planks made of wood, especially real wood, has a shaft, a conical tip formed at the front end region of the shaft and a head formed at the rear end region of the shaft. A thread has a forward facing insertion flank and a rearward facing grip flank between the conical tip and the head. The thread is a double thread, wherein a grip flank angle (α) measured between the grip flank and a plane perpendicular to the longitudinal axis of the nail screw is between 25 and 35 degrees, more preferably between 28 and 32 degrees, most preferably 30 degrees. The conical tip has a tip angle (ε) between 80 and 120 degrees, more preferably between 90 and 110 degrees, most preferably of 80, 90 or 100 degrees.