Quick-Fastening Screw Thread Geometry for Lower Torque
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Solution Overview
Problem
Conventional screws experience high screwing resistance and torque due to inefficient cutting action and debris accumulation, leading to increased friction and potential workpiece cracking.
Innovation Solution
The screw design features non-circular shank sections with three flank, arc, and curved cutting portions, where the radian of the curved cutting portions is less than a quarter of the maximum thread radius, reducing friction and providing adequate debris space, resulting in a quick and efficient screwing operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the corners of the thread are curved to form three flanks and three corners, then the thread structure is complete, but the cutting action becomes inefficient and screwing resistance increases
Solution Approach 1:
The patent applies local quality by making different parts of the thread have different characteristics. Specifically, the cutting portion has a sharp corner with a small radius (0.1-0.5mm) to enable efficient cutting, while other portions of the thread maintain the conventional curved structure. This localized differentiation allows the cutting area to have optimal cutting properties without compromising the overall thread structure.
Solution Approach 2:
The patent changes the geometric parameters of the thread corner from the conventional large radius (≥1/3 of thread radius) to a small radius (0.1-0.5mm). This parameter change transforms the corner from a curved, friction-prone shape to a sharp, cutting-efficient shape, directly addressing the contradiction between structural completeness and cutting efficiency.
2Stability of the object's composition
If the flanks have a curved shape due to curved corners, then the thread structure is stable, but friction between flanks and workpiece increases
Solution Approach 1:
The patent applies local quality by restricting the curved shape to specific portions of the thread while maintaining straight or minimally curved flanks in the cutting region. This localized approach allows the thread to maintain structural stability in non-cutting areas while minimizing friction in the cutting area where straight flanks are critical.
3Strength
If the corners are curved with large radius, then the thread structure is robust, but debris-receiving space is insufficient
Solution Approach 1:
The patent applies local quality by concentrating the curved structure in specific portions of the thread that are not involved in cutting, while maintaining a sharp corner geometry at the cutting portion. This creates sufficient debris-receiving space in the curved portions without compromising the sharpness needed for effective cutting.
4Ease of manufacture
If conventional thread geometry is used, then manufacturing is standard, but cracks occur in the workpiece due to high torque
Solution Approach 1:
The patent changes the critical parameter of the corner radius from the conventional large value (≥1/3 of thread radius) to a small value (0.1-0.5mm). This parameter change reduces the torque required for screwing by improving cutting efficiency, thereby preventing workpiece cracking while still using standard manufacturing processes.
Data Source
AI summary
A quick fastening screw includes a head, a shank with spirally-disposed thread convolutions, and a drilling portion. Each thread convolution has at least three flank sections and at least three arc sections each formed between any two adjacent flank sections. Two ends of each arc section and the flank sections adjacent to the arc section are respectively intersected to thereby form two joints. Between the two joints is formed a curved cutting portion which forms a radian not more than a quarter of a maximum thread radius so that each curved cutting portion becomes sharp to cut quickly, speed up a screwing operation, decrease the friction between the thread convolutions and a workpiece, and reduce the resistance and torque. The non-circular thread convolutions also receive cut debris efficiently and prevent the cracking of the workpiece caused by the undue accumulation of the debris.