Thread-Cutting Screw Geometry for Higher Load-Bearing Threads
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Solution Overview
Problem
Existing screws for tapping threads in components often lack sufficient load-bearing capacity, leading to potential thread tearing during tightening.
Innovation Solution
A screw design featuring a shank with a grooving section and a holding section, where the holding section has a larger outer diameter and a round cross-section, and the grooving section has a polygonal cross-section with trilobular geometry, along with varying thread flank dimensions to enhance engagement and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the holding section has a larger outer diameter than the cutting section, then the load-bearing capacity is improved, but the device complexity increases
Solution Approach 1:
The screw shank is divided into distinct functional sections: a cutting section with smaller diameter for thread formation and a holding section with larger diameter for load-bearing engagement. This segmentation allows each section to be optimized for its specific function, resolving the contradiction between improved strength and increased complexity by making the complexity serve a clear functional purpose.
Solution Approach 2:
Different sections of the screw shank are given different local qualities: the cutting section has a smaller outer diameter and specific thread geometry optimized for cutting, while the holding section has a larger outer diameter and thread geometry optimized for load-bearing. This local differentiation resolves the contradiction by ensuring that the increased diameter (and associated complexity) is applied only where needed for strength.
2Reliability
If the holding section has a round cross-section, then the engagement with grooved thread is optimized, but the thread cutting performance deteriorates
Solution Approach 1:
The screw is segmented into a cutting section with polygonal cross-section for efficient thread cutting and a holding section with round cross-section for optimal engagement. This segmentation resolves the contradiction by assigning the round cross-section (better engagement) only to the holding section where it is needed, while the cutting section maintains the polygonal cross-section for manufacturing efficiency.
Solution Approach 2:
The cross-section shape is varied locally along the screw length: polygonal in the cutting section for ease of manufacture and thread cutting, and round in the holding section for optimized engagement with the grooved thread. This local quality variation resolves the contradiction between engagement quality and manufacturing ease.
3Reliability
If the thread flanks in the holding section are narrower, then the engagement with cut thread is improved, but the stability during thread cutting deteriorates
Solution Approach 1:
The thread flanks are segmented into different widths along the screw length: wider flanks in the cutting section for stability during thread formation, and narrower flanks in the holding section for improved engagement with the cut thread. This segmentation resolves the contradiction by ensuring that narrower flanks (better engagement) are applied only where stability is less critical.
Solution Approach 2:
The thread flank width is varied locally: wider flanks in the cutting section provide stability during the cutting process, while narrower flanks in the holding section optimize engagement with the formed thread. This local differentiation resolves the contradiction between engagement quality and cutting stability.
4Strength
If the holding section has a larger outer diameter, then the load-bearing capacity is improved, but the manufacturing complexity increases
Solution Approach 1:
The screw is manufactured as a segmented component with distinct diameter sections, allowing the larger diameter holding section to be produced using appropriate forming processes. The segmentation enables specialized manufacturing techniques for each section, resolving the contradiction between improved strength and manufacturing complexity.
Solution Approach 2:
The outer diameter is varied locally along the screw length, with the larger diameter applied only to the holding section where load-bearing capacity is critical. This local quality variation ensures that manufacturing complexity is concentrated only where it is needed to achieve the required strength, rather than affecting the entire screw.
Data Source
Figure 1~5
Figure 6~10
AI summary
The invention relates to a screw (10) for cutting a thread into a component, comprising a shaft, which is provided with a thread at least in some sections, and comprising a screw head (14) having a drive formation, which screw head is adjoined by the shaft, wherein, proceeding from an end of the shaft lying opposite the head, first a cutting section (20) and the a holding section (24) are arranged, wherein the cutting section and the holding section are provided with a thread, wherein the holding section has a greater outside diameter than the cutting section, characterized in that a cone-frustum-type intermediate section (22) provided with a thread is arranged between the holding section and the cutting section and that the cutting section has a cone-frustum-type application section (16).