Threaded Stud Locking Pawl Prevents Thread Intrusion
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Solution Overview
Problem
Existing fastening systems for critical applications, such as aircraft wings, face challenges in maintaining proper preload while preventing fastener threads from entering the work piece bore, which can cause damage and interfere with nearby structures, due to the difficulty in ensuring the correct thread extension and engagement without visible grip length observation during installation.
Innovation Solution
A spring-loaded detent pawl mechanism that engages a slot in the encapsulating nut, providing tactile and auditory feedback to ensure correct thread positioning, preventing thread intrusion into the bore and ensuring sufficient thread protrusion, allowing for manual installation without specialized tools and reducing capital requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If automated installation tools are used to apply specified preload, then proper preload is ensured, but fastener threads may enter the work piece bore causing damage
Solution Approach 1:
The pawl mechanism is pre-configured with a spring-loaded detent that engages with the nut at a predetermined position. This preliminary mechanical stop prevents the nut from being tightened beyond the safe threshold where threads would intrude into the bore, allowing the installer to apply preload without risking thread intrusion.
Solution Approach 2:
The pawl-nut engagement provides tactile feedback to the installer, indicating when the correct preload position is reached. The detent mechanism creates a noticeable mechanical stop or click that signals the installer to halt further tightening, preventing thread intrusion while ensuring adequate preload is achieved.
2Ease of operation
If grip length is not visible during installation, then installation process is simpler, but installer cannot determine correct thread extension
Solution Approach 1:
The fastener system is self-regulating through the pawl mechanism that automatically engages with the nut at the correct position. The spring-loaded detent self-adjusts during tightening to prevent over-compression, eliminating the need for the installer to visually monitor grip length or calculate precise thread extension.
Solution Approach 2:
The pawl acts as an intermediary mechanical element between the nut and the work piece. It mediates the tightening process by providing a physical stop that translates the invisible grip length requirement into a tangible mechanical constraint, allowing the installer to proceed without visual measurement.
3Reliability
If excess threads extend beyond the nut, then sufficient thread protrusion is ensured, but threads may interfere with nearby moving structures
Solution Approach 1:
The pawl mechanism is pre-positioned to engage the nut at the optimal point that ensures sufficient thread protrusion for reliable engagement. This preliminary mechanical constraint prevents the nut from being tightened too far, which would cause excess thread extension beyond what is necessary for secure fastening.
Solution Approach 2:
The spring-loaded detent mechanism dynamically adjusts the engagement parameters during installation. The spring force and pawl geometry are designed to create a precise stop point that optimizes the balance between thread protrusion length and avoidance of interference with surrounding structures.
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
The solution effectively prevents thread intrusion into the work piece bore, ensures proper preload, and provides feedback for correct engagement, simplifying the installation process and reducing the need for specialized tools, while maintaining the integrity of the fastening system.
Implementation Method 1
a spring loaded detent pawl that moves perpendicularly to the axis of the stud
Implementation Method 2
provides tactile and auditory feedback to indicate that the fastener is properly placed and engaged
Data Source
AI summary
A threaded fastener-nut combination for attaching two work pieces together has means for preventing the intrusion of the fastener threads into the bores of each work piece, thus preventing damage to the work piece which may result from such intrusion. The stud member has a pawl member which extends radially outward to engage an aperture in the nut member, which locks the nut member to the stud member. The engagement of the nut member to the threaded portion of the stud member produces both audible and tactile feedback to indicate that the fastener is properly placed and engaged. Tactile feedback is returned through the emergence of the pawl through the aperture in the nut, and by the rotation of the entire fastener assembly upon the provision of further tightening effort. Auditory feedback is provided through a “click” or similar sound produced when the pawls engages the aperture of the nut.