Variable-Width Screw Thread Geometry for Low-Friction Wood Fastening
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Solution Overview
Problem
Conventional screws require excessive force to drive into wooden work pieces due to high friction, leading to potential breakage and insufficient fastening, limiting their applications.
Innovation Solution
A screw design featuring a threaded section with oval cross-section threaded units and projections that reduce friction by creating gaps, allowing for easier driving and increased fastening effect through arch-shaped surfaces formed by rear wing portions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a conventional screw is driven into a wooden work piece, then the screw can fasten the work piece, but excessive force is required due to high friction between the screw surfaces and the work piece
Solution Approach 1:
The threaded section is divided into multiple threaded units with varying widths. Each threaded unit has a different width along its length, creating segments that interact differently with the work piece. This segmentation allows certain portions to engage while others create gaps, reducing overall friction
Solution Approach 2:
Different portions of the threaded units have different widths, creating local variations in contact quality. The narrower portions create gaps with the work piece to reduce friction, while the wider portions provide engagement. This local quality variation optimizes both fastening and friction reduction
2Productivity
If excessive force is applied to drive the screw into the work piece, then the screw can be driven in, but the screw may break due to the great force
Solution Approach 1:
The threaded section is divided into multiple threaded units with varying widths. This segmentation allows the screw to engage the work piece in a controlled manner, distributing the driving force across different sections and reducing peak stresses that could cause breakage
Solution Approach 2:
The width parameter of the threaded units is varied along the length of the shank. This parameter change creates a progressive engagement pattern that reduces the peak force required during driving, thereby reducing the risk of screw breakage while maintaining fastening efficiency
3Strength
If a conventional screw is used, then the screw can fasten the work piece, but the fastening effect is insufficient and limits applications requiring sufficient fastening
Solution Approach 1:
The threaded section is divided into multiple threaded units with varying widths. This segmentation creates a pattern of engagement and gaps that enhances the mechanical interlocking with the work piece, improving the fastening effect and enabling use in applications requiring stronger fastening
Solution Approach 2:
Different portions of the threaded units have different widths, creating local variations in engagement quality. The narrower portions create gaps to reduce friction during driving, while the wider portions provide enhanced engagement for stronger fastening effect, thereby expanding application range
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 design reduces labor required for fastening, decreases friction, and enhances the screw's holding power by spreading the work piece and creating gaps, making the fastening process more efficient and effective.
Implementation Method 1
There is friction between the surfaces of the shank 91 and the threaded section 93 and the work piece 90. Thus, an individual has to exert a great force (i.e., being labor intensive) in the fastening process.
Implementation Method 2
after the screw has driven into the work piece, an arch-shaped surface formed by rear portions of the wings, i.e., as a hook. The hook may increase the fastening effect produced by the screw.
Data Source
AI summary
A screw includes a shank and a threaded section spirally formed on the shank. The threaded section includes threaded units having a length greater than a pitch, each threaded unit including a closed curve having two opposing first curved sections and two opposing second curved sections. Each threaded unit is further provided with two opposing high points each formed between the first curved section and the adjacent second curved section and two opposing low points each formed between the first curved section and the adjacent second curved section. Width of the threaded unit at the high points is the greatest and width of the threaded unit at the low points is the least. The width of the threaded unit is decreased from the high point to the low point.