Variable-Flank Screw Thread for Self-Locking Fastening
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Solution Overview
Problem
Existing screws experience insufficient frictional connections that lead to loosening, compromising the stability of the screw joint.
Innovation Solution
A screw design featuring a shank with threads having different angles at the thread crest and valley, allowing for easy installation and a self-locking feature that prevents loosening through optimized stress distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional thread designs with uniform flank angles are used, then the screw can be manufactured simply, but the frictional connection is insufficient and the screw loosens
Solution Approach 1:
The patent applies local quality by varying the flank angles at different locations along the thread. Specifically, the thread has a first flank angle in the thread root region and a second flank angle in the thread crest region, where these angles differ from each other. This local variation optimizes the frictional connection and stress distribution in different thread zones, preventing loosening while maintaining manufacturability.
Solution Approach 2:
The patent changes the geometric parameters of the thread by introducing different flank angles at different positions. The thread profile transitions from a uniform angle design to a variable angle design, where the flank angle is modified in specific regions (root vs. crest) to enhance the frictional connection and prevent loosening without significantly complicating the manufacturing process.
2Strength
If standard thread profiles are used, then manufacturing is straightforward, but force transmission and connection stability are insufficient
Solution Approach 1:
The patent enhances force transmission by applying local quality to the thread geometry. Different flank angles are assigned to different thread regions: a first flank angle in the root region and a second flank angle in the crest region. This localized optimization improves stress distribution and force transmission efficiency without requiring complete redesign of the entire thread profile, thus maintaining ease of manufacture.
Solution Approach 2:
The patent implements partial action by modifying only specific portions of the thread profile rather than the entire thread. The flank angle variation is applied selectively in the thread root and crest regions, which are the critical zones for force transmission and stress concentration. This partial modification achieves improved strength while avoiding the complexity of redesigning the complete thread geometry.
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 screw achieves stable connections by enhancing force transmission and preventing loosening, with additional benefits including reduced manufacturing costs for mating parts and versatility in materials like plastic.
Implementation Method 1
Screwing in the screw creates a force N acting in the normal direction between the facing flank surfaces, and due to the friction between them, a frictional connection is created to prevent rotation.
Implementation Method 2
Screwing in the screw creates a force N acting in the normal direction between the facing flank surfaces
Data Source
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AI summary
A screw (1) is proposed having a shank (4) having a longitudinal axis (12), a first end (9) and a second end (17), the shank (4) having at least a partial thread (5), the thread (5) having a thread pitch (6) having a thread crest (7), a thread valley (8), a thread depth resulting from the thread crest (7) and the thread valley (8), a flank (10) facing the first end (9) of the shank (2) and a flank (11) facing away from the first end (9) of the shank (2),wherein a flank (10) facing the first end (9) of the shaft (2) has at least two different angles enclosed between the longitudinal axis (12) and the flank (10) from the thread valley to the thread crest (7) and/or a flank (11) facing away from the first end (9) of the shaft (2) has at least two different angles enclosed between the longitudinal axis (12) and the flank (11) from the thread valley (8) to the thread crest (7), wherein the angle (20) enclosed in the thread valley (8) of a flank (10) facing the first end (9) of the shaft (2) is shallower than the angle (21) enclosed at the thread crest (7) and/or the angle (22) enclosed in the thread valley (8) of a flank (11) facing away from the first end (9) of the shaft (2) is shallower than the angle (23) enclosed at the thread crest (7),which makes it possible to easily screw the screw (1) according to the invention into a counterpart and a self-locking mechanism prevents the screw (1) according to the invention from loosening.