Double-Thread Screw Tip Geometry for Chip-Free Metal Fastening
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Solution Overview
Problem
Existing screws for attaching metal sheets to wooden substructures and for overlapping metal components are complex to manufacture and generate metal chips during use, leading to corrosion issues and increased storage and operational costs.
Innovation Solution
A double-threaded screw design with a tapered tip area featuring varying flank angles and thread heights, allowing for secure penetration and gripping without chip formation, and suitable for both wood and metal applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a drill bit is used to penetrate metal sheets for fastening, then the screw can be attached directly without pre-drilling, but metal chips are ejected requiring subsequent cleaning to avoid corrosion problems
Solution Approach 1:
The patent changes the geometric parameters of the thread in the tip area, specifically varying the flank angle along the thread length. The flank angle transitions from a smaller angle near the tip to a larger angle toward the shank, which modifies the cutting action to prevent chip ejection while maintaining direct penetration capability
Solution Approach 2:
The patent applies different thread characteristics to different sections of the screw. The tip area has a specific thread design with varying flank angles optimized for chip-free penetration, while the shank area has a different thread design optimized for gripping the wood or metal substrate
2Productivity
If a drill bit is used for fastening metal sheets, then direct attachment is enabled, but the drill bits are more complex to manufacture than threaded bits
Solution Approach 1:
The patent designs a screw that combines both drilling and threading functions in a single component. The threaded tip serves dual purposes: cutting through the metal sheet like a drill bit and simultaneously forming threads for fastening, eliminating the need for separate drill bit and screw components
Solution Approach 2:
The varying flank angle parameter along the thread length enables the threaded tip to perform both cutting and threading functions. The smaller flank angle portion facilitates material removal and penetration, while the larger flank angle portion facilitates thread formation and gripping
3Reliability
If specialized screws are used for plate-to-plate and plate-to-wood fastening combinations, then each application has optimized performance, but storage costs increase and operational reliability decreases
Solution Approach 1:
The patent creates a universal screw design that can be used for both metal-to-metal and metal-to-wood fastening applications. The threaded tip configuration enables the screw to function effectively in both overlapping metal sheet scenarios and metal sheet to wood substructure scenarios, eliminating the need for separate specialized screws
Data Source
Figure 1~2
Figure 3
AI summary
A screw (10), which can be used both as a fastener for sheet metal panels on wooden substructures and as an overlap fastener, has a screw head (11) with an adjoining, essentially cylindrical screw shank (12). This shank transitions into a tapered tip section (13) with a point (15) and is provided with a first thread (21) that begins near or directly at the point (15) and extends to the screw shank (12). A second, further thread (22), which begins near or directly at the point (15) and extends over the tip section (13), is arranged between the threads of the first thread (21) and terminates at the transition between the tip section (13) and the screw shank (12). According to the invention, the flank angle ϕ of the first thread (21) in the tip region (13) is between 90° +/-5° in a front section (25) of the tip region (13) near the tip (15).This decreases continuously in a subsequent transition area (26) to a value of 60° +/-5° in a rear section (27) of the peak area (13) .