Self-Tapping Screw with Opposite Pitch Tip for Wood Splitting
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Solution Overview
Problem
Existing screws face challenges in minimizing wood splitting during screwing, especially when used near the edge of wood, where the enlarging tip of the screw can cause the wood fibers to split, preventing thorough tightening.
Innovation Solution
A self-tapping screw design featuring an opposite pitch thread that covers only the tip, with a cutting thread arranged to prevent splitting, where the thread height and pitch can vary to optimize engagement with wood, and the cutting thread can be symmetrical or asymmetrical relative to the screw thread, ensuring minimal wood damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the screw tip is enlarged to facilitate threading into wood, then the threading capability is improved, but the wood fibers split open preventing thorough tightening
Solution Approach 1:
The screw thread is segmented into two distinct parts: a cutting thread at the tip with opposite pitch to the main screw thread. This segmentation allows the cutting thread to perform the function of enlarging the hole and separating wood fibers without causing splitting, while the main screw thread provides the tightening function. The cutting thread acts as a separate functional element that prepares the path for the main thread.
Solution Approach 2:
The cutting thread at the tip has an opposite pitch compared to the main screw thread. This inversion of the thread pitch direction allows the cutting edge to function differently from conventional screws - instead of the thread pulling material inward, the opposite pitch creates a cutting action that separates fibers cleanly without causing the splitting that would occur with traditional enlarging tips.
2Ease of operation
If serrations are arranged longitudinally on the screw tip, then threading into wood is facilitated, but the risk of splits or splintering increases
Solution Approach 1:
Instead of using conventional longitudinal serrations that push wood fibers aside and cause splitting, the invention uses a cutting thread with opposite pitch that creates a controlled cutting action. This inverted approach transforms the mechanism from displacement-based (serrations pushing fibers) to cutting-based (opposite pitch thread separating fibers cleanly), thereby reducing splits and splintering while maintaining threading ease.
3Object-affected harmful factors
If the cutting thread covers only the tip area, then the splitting effect is minimized, but the threading function must be optimized in this limited area
Solution Approach 1:
The screw features locally differentiated thread properties: the cutting thread at the tip has opposite pitch and specific geometric characteristics optimized for hole enlargement and fiber separation, while the main screw thread has standard pitch optimized for tightening. This local quality differentiation allows each section to perform its specific function optimally without compromising the other, resolving the complexity challenge by making the thread geometry adaptive to local functional requirements.
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 effectively reduces the risk of wood splitting, allowing for complete tightening without fiber damage, and can be used in various materials including wood and sheet metal, with optimized threading characteristics achieved through cold rolling.
Implementation Method 1
the cutting thread arranged in the front area of the screw shaft (1) in a tip region of the screw (6, 7) with an opposite pitch compared to the screw thread (6)
Implementation Method 2
As concerns the manufacture of the screw by reshaping, the optimum structure is achieved by cold rolling
Data Source
AI summary
The invention concerns a screw, in particular a self-tapping screw, with a screw thread which reaches to the front end of the screw formed as a drilling tip. In the front area, starting with a distance from the front end of the screw, there is an opposite thread showing the same pitch as the screw thread, however, its thread height is lower than the thread height of the screw thread. This second, opposite single-thread, double-thread or triple-thread/multi-thread only reaches over the tapered drilling tip and leaves the shank of the screw free. It forms a cutting edge with its thread edge which is used to cut fibers in order to reduce wedge effect during screwing in the screw. The screw is particularly suitable for wood or wood-like materials in the edge areas of structural elements.