Countersunk Screw Head Recesses for Stronger Cutting and Locking
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Solution Overview
Problem
Existing self-tapping screw head structures face issues with insufficient cutting force and stability during the fastening process, particularly due to weak cutting ends and uneven workpiece surfaces caused by remnant wood crumbs.
Innovation Solution
The screw head features a cone portion with multiple recesses spaced circumferentially, each with distinct side edges and top edges designed for both radial and longitudinal cutting, allowing for efficient waste accommodation and enhanced countersinking, with recesses extending over 120 degrees to provide comprehensive cutting and locking stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a single cutting end is used at the screw head structure, then the structure is simple, but the cutting force on the workpiece is weak
Solution Approach 1:
The screw head structure is segmented into multiple cutting ends (first cutting end and second cutting end) instead of using a single cutting end. Each cutting end is formed by specific edges of the recesses (first side edges forming first cutting ends, second side edges forming second cutting ends), thereby distributing and enhancing the cutting force across multiple contact points with the workpiece.
2Reliability
If multiple recesses with large extension angles are used, then cutting force and locking stability are improved, but the screw head structure becomes more complex
Solution Approach 1:
The recesses are designed with non-uniform characteristics: first side edges have first recess depths while second side edges have second recess depths, with the maximum second recess depth being less than the maximum first recess depth. This local variation in depth creates differentiated cutting capabilities and locking characteristics at different locations, optimizing both cutting force and stability without requiring excessive complexity.
3Manufacturing precision
If the top edge is positioned close to the top portion, then the countersinking effect is enhanced, but the top edge may interfere with adjacent recesses
Solution Approach 1:
The top edge is positioned partially between the top portion and the first side edge of an adjacent recess, rather than extending fully to the first side edge or remaining too far from the top portion. This partial positioning provides sufficient countersinking effect while avoiding interference with adjacent recesses, achieving the optimal balance through controlled partial action.
Data Source
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AI summary
A screw (10) includes a head (12) and a shank (14) extending from the head (12) and defining a longitudinal axis (X). A thread (16) is provided on the shank (14). The head (12) includes a top portion (18) and a cone portion (20) located between the top portion (18) and the shank (14). A plurality of recesses (26) are provided in a peripheral surface (22) of the cone portion (20) and spaced in a circumferential direction of the cone portion (20). Each recess (26) includes first and second side edges (28, 30) opposite to each other in the circumferential direction and a top edge (32) connecting the first and second side edges (28, 30). The first side edge (28) features a maximum recess depth greater than a maximum recess depth of the second side edge (30). The top edge (32) extending in the circumferential direction of the cone portion (20) is partially arranged between the top portion (18) and the first side edge (28) of an adjacent recess (26) in the longitudinal axis direction.