Curved-Wall Fastener Head for High-Torque Wrench Engagement
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Solution Overview
Problem
Conventional flanged hexagon screws suffer from edge wear leading to reduced torque transmission and increased likelihood of wrench slippage due to sharp edges, resulting in inadequate fastening and potential failure.
Innovation Solution
A fastener design with a driven protrusion featuring alternating curved and straight wall sections, along with a driving tool having corresponding wall configurations, ensures stable engagement and enhanced torque transmission, reducing slippage and wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a hexagonal protrusion with sharp edges is used for wrench engagement, then the fastener can be driven by conventional wrenches, but the sharp edges wear easily and cause wrench slippage
Solution Approach 1:
The patent replaces the conventional sharp-edged hexagonal protrusion with curved wall portions that have rounded contours. This curvature eliminates stress concentration points, prevents edge wear and chipping, while maintaining adequate wrench engagement through the curved geometry that provides sufficient contact area for torque transmission.
2Power
If sharp edges are used on the hexagonal protrusion, then initial torque transmission is effective, but the contact area decreases when edges wear, reducing torque transmission
Solution Approach 1:
The curved wall portions maintain a consistent contact area with the wrench throughout the fastener's service life. The rounded geometry prevents the contact area from decreasing due to wear, as there are no sharp edges to wear down. This ensures sustained torque transmission capability over extended periods.
Solution Approach 2:
The patent modifies the geometric parameters of the protrusion by introducing curvature radius and rounded contours instead of sharp edges. This parameter change transforms the wear characteristics, converting from edge wear to surface contact that maintains adequate torque transmission throughout the fastener's operational life.
3Ease of manufacture
If conventional hexagonal protrusions are used, then manufacturing is simple, but the fastener cannot withstand high torques without slippage
Solution Approach 1:
The curved wall portions can be formed using standard molding or machining processes, maintaining manufacturing simplicity. The curvature distributes contact stresses more evenly during wrench engagement, enabling the fastener to withstand higher torques without slippage or edge damage while remaining compatible with conventional manufacturing methods.
Data Source
Figure 1
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Figure 4~5
AI summary
A fastener (1) includes a screw head (11) that includes a driven protrusion (112) having four driven wall portions (113) and four guiding wall portions (114) which are disposed about a central axis of the fastener (1) in an alternating arrangement. The driven wall portions (113) are equiangularly spaced apart from each other. Each of the guiding wall portions (114) is straight, and has two opposite ends that are respectively connected to two of the driven wall portions (113) adjacent to the guiding wall portion (114). A ratio of a longest distance (B) between two of the driven wall portions (113) that are non-adjacent to each other to a longest distance (A) between two of the driven wall portions (113) that are adjacent to each other is greater than 1.16. Each of the driven wall portions (113) has a curved section (115) and two straight sections (116).