Prolate-Shank Fastener for Low-Torque Flush Installation
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Solution Overview
Problem
Conventional fasteners require high torque for insertion and often leave a protruding head, compromising the flushness of the fastened surface.
Innovation Solution
A fastener design featuring a shank with prolate cross-section regions, which reduces torque requirements and allows for a flush surface integration by incorporating elliptical or lens-shaped cross-sections that facilitate easier insertion and minimize material resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional fasteners with cylindrical cross-sections are used, then structural simplicity is maintained, but high torque is required for insertion and flush surface integration is difficult
Solution Approach 1:
The fastener shank incorporates prolate cross-section regions with asymmetric geometry (elliptical or lens-shaped) that differ from conventional cylindrical sections. These asymmetric sections reduce material resistance during insertion and enable the head to embed flush with the surface, solving the torque and flushness problems while accepting increased geometric complexity
Solution Approach 2:
The fastener features localized prolate cross-section regions rather than a uniformly complex geometry. The shank transitions between cylindrical and prolate sections, applying the asymmetric shape only where needed to reduce insertion torque and improve embedment, while maintaining simpler cylindrical sections elsewhere to balance manufacturing complexity
2Productivity
If prolate cross-section regions are added to reduce torque requirements, then insertion ease is improved, but manufacturing complexity increases
Solution Approach 1:
The patent modifies the cross-sectional geometry parameters of the shank by introducing prolate sections with specific dimensional relationships (polar diameter greater than equatorial diameter). These parameter changes enable reduced insertion torque and improved productivity, while the changes are constrained to specific regions to limit manufacturing complexity increases
3Shape
If the fastener head is designed to embed into the material, then flush surface is achieved, but high insertion torque is required
Solution Approach 1:
The prolate cross-section regions with asymmetric geometry (non-circular) create favorable stress distributions and material displacement patterns during insertion. This asymmetric shape reduces the force required to embed the head flush with the surface, simultaneously achieving good surface flushness and reduced insertion torque
Data Source
Figure 1
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AI summary
A fastener (10) includes a shank (100) having a point (102) at a first end and a second head end (140). One or more prolate cross-section regions (210) is formed in the shank. Prolate cross-section regions may be formed in a threaded section and/or a thread free section of the fastener. Each prolate cross-section may have a polar diameter greater than the cylindrical diameter of the region in which it is formed and an equitorial diameter smaller than the corresponding cylindrical diameter of the region in which it is formed. Two generally adjacent prolate cross-section regions have cross-sections offset with respect to each other by an angle between zero and ninety-degrees.