Wood Screw Thread Protrusions for Low Torque and Split Resistance
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Solution Overview
Problem
Conventional wood screws face issues with high screwing torque, material splitting, and reduced unscrewing torque due to the cutting of wood fibers during screwing, which increases the effort required and can damage the component.
Innovation Solution
The wood screw design features alternately formed protrusions on its threaded revolutions, which cause reversible material displacement, increasing the thread extract force without significantly increasing pressure or material displacement in the radial direction, and includes beveled leading flanks to reduce screwing torque and sharp trailing edges to enhance unscrewing torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional wood screws cut wood fibers during screwing, then the threaded extractor is improved, but the screwing torque is increased and the material may split
Solution Approach 1:
The threaded portion is segmented into multiple threaded revolutions with alternating protrusions. These protrusions divide the material displacement into separate stages, allowing fibers to be compressed and displaced alternately rather than cut continuously, reducing screwing torque while maintaining threaded extractor
Solution Approach 2:
The protrusions extend in the longitudinal direction between threaded revolutions, creating material displacement in the longitudinal dimension rather than purely radial cutting. This dimensional change allows fibers to be compressed and displaced along the screw axis, reducing resistance and screwing torque
2Strength
If conventional wood screws cut wood fibers during screwing, then the threaded extractor is improved, but material splitting occurs
Solution Approach 1:
The protrusions convert the harmful cutting action into a beneficial compression and displacement action. By pressing material to the outside between threaded revolutions rather than cutting it, the protrusions eliminate chip formation and fiber damage that cause material splitting, while still providing adequate threaded extractor
Solution Approach 2:
The alternating protrusions segment the material interaction into compression zones and displacement zones. This segmentation prevents continuous fiber cutting and chip formation, eliminating the harmful effect of material splitting while maintaining the necessary threaded extractor through the threaded revolutions
3Reliability
If conventional wood screws are screwed in, then the component is connected, but the unscrewing torque is reduced due to chip formation
Solution Approach 1:
The protrusions eliminate chip formation that normally reduces unscrewing torque. By compressing and displacing fibers rather than cutting them, the protrusions keep the counter thread clean and intact, maintaining high unscrewing torque while still providing reliable connection strength through the threaded extractor
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
This design reduces the screwing torque, minimizes material splitting, and increases the unscrewing torque while maintaining a high thread extract force, thereby improving the overall performance of the wood screw.
Implementation Method 1
This displacement causes a reversible deformation of the material in the passage of one of the protrusions when screwing in the screw, whereby the material can then return to the initial state again
Data Source
Figure 1~1a
Figure 2~2a
Figure 3~3a
AI summary
Wood screw (1), comprising a cylindrical screw shank (2), at one end of which a tip (3) is formed, a screw head (4), which is formed at the other end of the screw shank (2), and also at least one threaded portion (5), which extends from the tip (3) in the direction of the screw head (4), wherein the threaded portion (5) has a thread core (6) and a thread helix, which extends around the thread core (6) and has a number of thread turns (7), wherein a number of successive thread turns (7) have projections (8a, 8b), which are alternately formed substantially in the direction of the screw head (4) and substantially in the direction of the tip (3).