Stepped Screw Thread Geometry for Low-Torque Conductive Fastening
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Solution Overview
Problem
Existing screw threads with recessed portions for coating film removal struggle to maintain conductivity and workability with thick film coatings, as they require increased screwing torque and are prone to coating film interference during screwing.
Innovation Solution
A screw thread design featuring recessed portions with stepped portions and a bulging ridge-shape, where the stepped portions overhang to contact the internal screw thread, reducing screwing torque and stabilizing conductivity by preventing coating film interference, and the bulging ridge-shape enhances contact pressure for low axial forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a recessed portion is provided on the pressure-side flank surface to remove coating film, then coating film removability is improved, but screwing torque increases
Solution Approach 1:
The screw thread ridge is divided into multiple sections along the screwing direction, with recessed portions provided at specific intervals. This segmentation allows the coating removal function to be distributed across multiple locations rather than requiring a single large recessed portion, thereby reducing the overall impact on screwing torque while maintaining effective coating film removability.
Solution Approach 2:
The recessed portions are strategically positioned only on the pressure-side flank surface where coating film removal is most needed for conductivity, while other portions of the screw thread maintain their original structure. This localized modification optimizes coating removal effectiveness while minimizing the increase in screwing torque that would result from more extensive modifications.
2Force
If the ridge height in the distal end portion is reduced, then screwing torque is reduced, but coating film removal effectiveness deteriorates
Solution Approach 1:
The recessed portions are positioned specifically in the rear end portion of the screw thread ridge where coating film removal is most critical for establishing conductivity. The distal end portion maintains sufficient ridge height to ensure effective coating removal at the coating-thickest location, while the overall reduced ridge height profile minimizes screwing torque throughout the fastening process.
Data Source
AI summary
To provide a screw thread which achieves a further reduction in screwing torque while securing removability of a coating film or the like and which is capable of stabilizing conductivity. In a screw thread in which a recessed portion (7) is partially provided on a flank surface (131) of a screw thread ridge provided on a screw thread shaft main body (5), a screw thread ridge (13) in a section where the recessed portion (7) is formed is smaller than a regular screw thread ridge (3), and a ridge height (H12) in a distal end portion in a screwing direction is lower than a ridge height (H11) in a rear end portion in the screwing direction W.