Screw Thread Closing Fold Relocation to Flank
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Solution Overview
Problem
Existing screw thread production methods via flat die rolling result in a closing fold at the thread apex, leading to material weakening and reduced wear resistance, especially in self-tapping screws.
Innovation Solution
The closing fold is relocated to the thread flank area, with an asymmetrical design where one profile forms an entire flank and part of the opposite flank, distributing the closing fold to a less stressed region, and adjusting thread flank angles for optimal load transfer and ease of screwing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the closing fold is arranged at the apex of the thread, then the production process is simple, but the wear resistance is reduced
Solution Approach 1:
The patent applies asymmetry by designing the thread profile such that the closing fold is positioned on one flank rather than at the apex. The first profiling forms a complete first flank, while the second profiling forms only a portion of the second flank, creating an asymmetric thread geometry that relocates the closing fold to a less critical position and improves wear resistance
2Ease of operation
If the closing fold is arranged at the thread apex, then the material beads can be pressed together evenly, but material weakening occurs at the highly stressed area
Solution Approach 1:
The patent applies local quality by differentiating the functional requirements of different thread regions. The first flank is designed with a complete profile formation to ensure strength, while the second flank accepts the closing fold in a less stressed area. This localized differentiation allows the closing fold to be positioned away from the apex, maintaining both ease of operation and thread strength
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 enhances wear resistance and resilience of the screw, particularly when screwing into hard surfaces, by minimizing material weakening at the thread crest and optimizing load transfer during screwing.
Implementation Method 1
the thread being composed of two material beads which are formed from the base body by cold forming during the rolling process
Data Source
Figure 1~2f
Figure 3a~3h
Figure 4
AI summary
In a screw with at least one thread (26) produced by a rolling process, in particular a flat die rolling process, wherein the thread (26) is composed of two material beads (28a, 28b) formed from the base body (12) by cold forming in the rolling process, such that the thread (26) has a closing fold (32) at which the material beads (28a, 28b) meet, it is provided that the closing fold (32) is arranged in the region of a thread flank (30a, 30b) of the thread (26).