Positive-Locking Fastener Cap for Pin Alignment Without Retightening
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Solution Overview
Problem
Existing positive locking mechanisms for threaded fasteners, such as lock wires and cap-based systems, fail to adequately prevent loosening due to vibration, often requiring additional tightening that compromises the nominal torque of the nut.
Innovation Solution
A cap design that meshes with a nut, featuring a blocking portion and a locking portion with strategically arranged through openings, allowing for rotational alignment with the nut's star profile to ensure secure pin insertion without altering the nut's torque, thereby preventing loosening.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a cap with a limited number of teeth is used to engage with the nut, then the cap can be positioned at specific configurations, but aligning the radial hole with the cap's holes is not always possible without retightening the nut
Solution Approach 1:
The cap is divided into multiple identical opening pairs arranged at different angular positions around the main axis. Each opening pair can independently align with the radial hole, providing multiple alignment options without requiring retightening of the nut.
Solution Approach 2:
Multiple opening pairs serve the same function of receiving the pin, but are positioned at different angular locations. This allows any opening pair to potentially align with the radial hole regardless of the nut's final position, making the locking mechanism universally applicable to any nut orientation.
2Reliability
If locking wires are used to prevent fastener loosening, then some protection is provided, but the loosening is not sufficiently limited
Solution Approach 1:
The cap serves as an intermediary element between the nut and the pin. It provides a structured interface with multiple opening pairs that mediates the alignment between the radial hole and the pin, ensuring reliable locking without excessive complexity.
Solution Approach 2:
The solution moves from a single-point alignment problem to a multi-angular-position problem. By distributing opening pairs around the cap's circumference, the system adds an angular dimension to the alignment process, allowing alignment to succeed regardless of the nut's rotational position.
3Ease of operation
If the nut is retightened to allow pin insertion, then the locking mechanism can be installed, but the nut is no longer tightened to its nominal torque
Solution Approach 1:
The cap is designed with multiple opening pairs positioned in advance at different angular locations. This preliminary arrangement ensures that regardless of how the nut is tightened, at least one opening pair will align with the radial hole, eliminating the need for retightening and preserving the nominal torque.
4Adaptability or versatility
If multiple opening pairs are arranged around the cap, then alignment with the radial hole is always possible, but the angular sector coverage must be precisely calculated
Solution Approach 1:
The angular sector φ is precisely calculated based on the number of opening pairs N and the angular period θ of the nut's clamping portion. This parameter relationship (φ = θ/(2N)) ensures that the opening pairs provide adequate angular coverage while maintaining manufacturability and accounting for assembly tolerances.
Data Source
Figure 1A~1B
Figure 2~3
Figure 4
AI summary
The invention relates to a positive locking fastener comprising: - a screw (1) having a radial hole (120) at a threaded portion (12); - a nut (2) having a tightening portion (21); - a cap (3); and - a pin (4). The cap has a locking portion (31) intended to cover the threaded portion and an immobilising portion (30) intended to engage with a tightening portion of the nut. The locking portion comprises at least one pair of diametrically opposed openings (32) suitable for allowing a pair of openings to be aligned with the radial hole, in order to allow the pin to be inserted and thus lock the fastening regardless of the relative position of the nut with respect to the screw. The invention also relates to a method for implementing the fastener according to the invention.