Long-Pitch Threaded Wooden Plug for Stronger Panel Joints
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Solution Overview
Problem
Existing wooden connecting plugs face issues with ease of use, reliability, and tensile strength, particularly due to short pitch threading and dependence on humidity, which limits their length and connection strength, and often require high insertion forces or pre-forming of wooden elements.
Innovation Solution
A threaded wooden plug with a long pitch threading, occupying a small portion of the outer surface, and a frustoconical body, allowing easier insertion and improved grip through a self-tapping action, combined with a complementary tool for optimal insertion and connection strength, enabling longer plug lengths without material damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a short pitch threading is used on the wooden plug, then the insertion process is simplified, but the connection strength and reliability are reduced
Solution Approach 1:
The patent changes the pitch parameter from short to long (at least 0.5 times the outer diameter), which fundamentally alters the threading characteristics. This parameter change enables the threads to engage more wood material along the insertion path, providing both easier insertion through reduced resistance and superior connection strength through increased engagement area.
2Strength
If the pitch between adjacent threads is increased to at least 0.5 times the outer diameter of the plug, then the connection strength is improved, but the number of screwing turns required for insertion increases
Solution Approach 1:
The patent applies different threading characteristics to different regions of the plug. The threading is designed with long pitch for optimal connection strength, while the selective engagement of threads during insertion (rather than requiring all threads to engage simultaneously) locally optimizes the insertion process, reducing the effective number of turns needed.
3Ease of operation
If a threadless wooden plug is used, then the insertion process is simple, but the resistance to tensile forces is limited and dependent on humidity
Solution Approach 1:
The patent introduces threading as an intermediary mechanism between the plug and the hole wall. This threading structure acts as a mediator that actively engages the wood material, providing mechanical interlocking that supplements the passive friction-based holding of threadless plugs. The threads serve as an intermediate structure that converts simple insertion into active mechanical engagement, dramatically improving tensile resistance.
4Strength
If the threading occupies a large portion of the outer surface of the plug, then the biting action on the wood is improved, but the insertion force required increases
Solution Approach 1:
The patent applies the principle of partial action by having only the necessary portion of the plug surface engage the wood material. The long pitch threading ensures that not all threads engage simultaneously during insertion, but rather progressively along the insertion path. This partial engagement at any given moment reduces the instantaneous insertion force required, while the cumulative engagement along the entire threaded length provides sufficient biting action for strong connection.
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 solution enables easier and more reliable insertion of longer plugs with enhanced connection strength, reducing insertion force and maintaining panel flatness without subsequent trimming, while being easy and inexpensive to produce and assemble.
Implementation Method 1
the plug absorbs moisture, expanding, and therefore grips merely by means of friction
Data Source
Figure 1~9
Figure 10~14
AI summary
Wooden plug having a rear operating head (T) and a cylindrical or frustoconical body (10) extending in a longitudinal direction (X-X) and a transverse direction (Y-Y), a threading (20) being formed on the outer side surface of the cylindrical or frustoconical body (10), the plug being made of wood with a relative density >600kg/m3, preferably hardwood, wherein the threading (20) has a long pitch (P) of size comprised between 30% and 300% of the outer diameter (D) of the plug and such that the bottom surface of the threading comprised between opposite flanks of the adjacent threads is formed by the outer side surface of the cylindrical or frustoconical body (10) and occupies most of the threaded surface of the plug body.