Positive Locking Fastener Cap for Vibration Loosening Control
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Solution Overview
Problem
Existing mechanical fasteners with positive locking mechanisms, such as those using locking wires or star-shaped polygonal cross-sections, face issues like limited engagement positions, frequent disassembly needs, and reduced lifespan due to swaging and damage during disassembly, which lead to inadequate prevention of loosening under vibration.
Innovation Solution
A cap design for a fastener system that includes a screw with a blind hole and a nut with a tubular tightening portion, where the cap allows relative rotational movement and features anti-rotation elements with specific angular periods, enabling secure engagement and limiting loosening by maximizing the number of correct positioning options without requiring plastic deformation or frequent disassembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the number of cap engagement positions is limited to increase loosening prevention, then loosening prevention is improved, but the fastener can only be used a limited number of times
Solution Approach 1:
The angular period parameters θ and β of the anti-rotation elements are specifically designed to create multiple valid engagement positions. By optimizing these angular parameters, the system achieves both limited positions for loosening prevention and sufficient positions for multiple assembly-disassembly cycles, extending fastener usage life while maintaining reliability.
2Reliability
If angular clearances are minimized to reduce loosening, then loosening prevention is improved, but the number of common multiples of M and N increases
Solution Approach 1:
The anti-rotation elements act as intermediary features between the cap, screw, and nut. Instead of directly minimizing angular clearances between all components, the anti-rotation elements mediate the engagement by providing discrete engagement points that naturally limit rotation while allowing for practical manufacturing tolerances and assembly variations.
3Reliability
If swaging of the cap into the groove of the nut is used for locking, then positive locking is achieved, but the cap is damaged during disassembly by hub breaker
Solution Approach 1:
The anti-rotation elements are pre-configured on the cap before assembly. These elements engage with corresponding features on the screw and nut during initial assembly, establishing the locking mechanism in advance. This preliminary configuration allows for controlled engagement and disengagement without requiring forceful hub breaking that would damage the cap, thus preserving cap integrity while achieving positive locking.
Data Source
AI summary
The invention relates to a positive locking fastener comprising: a screw (1), a threaded portion (11) of which has a blind hole (110) and a groove (111); a nut (2) having a tightening portion (21); a cap (3); and a pin (4). The cap (3) has an immobilizing portion (31) intended to engage with the tightening portion (21) and a locking portion (32) intended to cooperate with the blind hole (110) to prevent said cap from rotating relative to the screw (1). The locking portion (32) also comprises openings (322) suitable for allowing the pin (4) to be inserted into said openings and into the groove (111) in order to hold the screw (1) and the cap (3) together.