Externally Threaded Fastener Root Geometry for Anti-Loosening
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Solution Overview
Problem
Existing threaded fasteners face issues with loosening due to load imbalance during tightening, leading to thread fracture and loosening, especially with JIS standard 6 g and 8 g accuracy fasteners, where the beveled sections on internally threaded fasteners often do not effectively engage with externally threaded fasteners, resulting in inadequate anti-loosening effectiveness.
Innovation Solution
An anti-loosening metallic externally threaded fastener with a planar section and a short beveled section on its root, where the beveled section is angled between 32 to 37 degrees, allowing the crest of the internally threaded fastener to pressure-contact the beveled section of the externally threaded fastener, distributing load more evenly across threads and preventing loosening.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If beveled sections are provided on internally threaded fasteners to prevent loosening, then anti-loosening effectiveness is improved, but the beveled sections often do not effectively engage with externally threaded fasteners of JIS standard 6 g and 8 g accuracy, resulting in inadequate anti-loosening performance
Solution Approach 1:
The invention provides a beveled section only on the compressing flank side of the root portion, not on the entire root. This localized beveled section at a specific angle (24.5° to 27°) creates effective engagement with the externally threaded fastener's crest while maintaining compatibility with JIS standard tolerances, resolving the contradiction between anti-loosening effectiveness and manufacturing precision
Solution Approach 2:
The invention specifies precise parameters for the beveled section including the angle (24.5° to 27°) and position (on the compressing flank side), which optimizes the engagement geometry to ensure reliable anti-loosening performance across standard manufacturing tolerances without requiring higher precision
2Reliability
If externally threaded fasteners are tightened with large force to prevent loosening, then anti-loosening effectiveness is improved, but the fasteners become stretched and fatiguing of the fastened objects occurs
Solution Approach 1:
The beveled section structure creates preliminary mechanical interference that generates radial binding force during normal tightening, preventing loosening before it occurs without requiring excessive tightening force that would cause stretching or fatigue
Solution Approach 2:
The beveled section creates a wedge-shaped geometric configuration that converts axial tightening force into radial binding force through mechanical interference, providing anti-loosening effect through geometry rather than excessive force
3Ease of manufacture
If standard threaded fasteners are used to simplify manufacturing, then ease of manufacture is improved, but load imbalance during tightening occurs with approximately 44% load on the first thread, 30% on the second, and 26% on the third, leading to thread fracture and loosening
Solution Approach 1:
The beveled section is provided only on the compressing flank side of the root portion rather than uniformly across all threads, creating localized load redistribution that improves thread load balance while maintaining manufacturing simplicity
Solution Approach 2:
The asymmetric placement of the beveled section on only the compressing flank side creates differential engagement that balances the load distribution across multiple threads, preventing the concentration of load on the first thread
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design ensures reliable anti-loosening performance by maintaining a high radially directed binding force, as demonstrated by tests meeting NAS 3350 and ISO 16130 standards, with unscrewing torque remaining above 13 N·m after 30,000 turns and retaining 80% of the initial axial force under shear-directed vibrations.
Implementation Method 1
the beveled section, and a thread-crest corner portion along the compressing flank of the internally threaded fastener, alone are brought into pressure-contact
Implementation Method 2
maintaining a high radially directed binding force, as demonstrated by tests meeting NAS 3350 and ISO 16130 standards, with unscrewing torque remaining above 13 N·m after 30,000 turns
Data Source
AI summary
[Problem] The purpose of the present invention is to provide an anti-loosening metallic male screw that can exhibit a sufficient anti-loosening effect by forming a flat part and a short slope in a part of the thread bottom of the male screw and thus ensuring pressure contact between a thread peak of a female screw and the slope at the thread bottom of the male screw. [Solution] An anti-loosening metallic male screw according to the present invention is to be engaged with a female screw for a metric screw, and is characterized in that the cross-sectional shape of the thread bottom of the metallic male screw is formed into a flat shape in which a non-pressurized flank side thereof is parallel to the axis of the male screw, is formed into a shape in which a pressurized flank side thereof is sloped toward the pressurized flank side with respect to an extension line of the flat part, and the outer diameter and the effective radial size of the metallic male screw are smaller than the reference sizes of the metric screw.