Reusable Threaded Fastener with Redundant Locking Features
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Solution Overview
Problem
Existing threaded fasteners in critical applications, such as aerospace, can loosen over time due to environmental factors like temperature cycling and vibration, necessitating redundant locking features to ensure joint integrity, but current methods like lockwire and deformed inserts are labor-intensive, costly, and prone to wear.
Innovation Solution
A reusable threaded fastener with multiple redundant locking features, comprising a threaded hollow lock bolt and a tapered lock stud that engage with a housing, providing frictional and taper-based locking mechanisms to prevent unintentional disengagement, including a 'jam nut' effect and radial hoop loading for enhanced security.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lockwire is used as a redundant locking feature, then the fastener is almost 100% effective in preventing inadvertent loosening, but the installation is extremely time consuming, tedious, and labor intensive
Solution Approach 1:
The locking insert is designed to automatically lock the fastener in place through deformation upon installation, eliminating the need for manual operations like lockwire installation. The insert self-activates the locking mechanism simply by being installed with the fastener, thereby reducing installation time while maintaining reliability.
Solution Approach 2:
The locking function is extracted from the fastener itself and implemented as a separate, pre-installed locking insert within the tapped aperture. This separation allows the locking mechanism to be independently optimized and installed once, rather than requiring repeated manual locking operations for each fastener installation.
2Reliability
If deformed inserts are used as a redundant locking method, then friction load inhibits the fastener from rotating, but repeated use causes the inserts to wear or yield to the point that they are no longer effective
Solution Approach 1:
The locking insert is designed with controlled deformation characteristics that create a cushioning effect, absorbing and distributing the locking forces to prevent excessive stress concentration. This prior cushioning design prevents the insert from yielding or wearing out prematurely, extending its service life while maintaining locking effectiveness.
3Reliability
If deformed inserts are used as a locking method, then the insert provides locking force, but the inserts are difficult to install properly and even more difficult to remove and replace
Solution Approach 1:
The locking insert utilizes dynamic deformation characteristics - it deforms elastically during installation to engage with the fastener, then maintains a stable locked state during service. This dynamic behavior allows for easy installation through simple fastener insertion, while providing robust locking force during operation, and facilitates removal when needed.
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 fastener effectively prevents unintentional loosening with multiple redundant locking features, ensuring the integrity of the fastened joint in high-value and safety-critical applications, while being easier to install and maintain compared to existing methods.
Implementation Method 1
The primary method of locking a threaded fastener is by torquing a fastener having external male thread into a component having matching female thread to a predetermined level. Torquing the fastener causes a threaded shank to load in tension which in turn causes the male and female treads to tightly engage at their interface and become fixed with respect to one another due to friction between the contact faces of the thread.
Implementation Method 2
A threaded lock stud having a tapered external wall is constructed to fit at least partially within the hollow lock bolt and threadingly engage the threaded aperture of the housing and engage the tapered wall of the hollow lock bolt
Implementation Method 3
A threaded hollow lock bolt having a tapered internal wall constructed to threadingly engage a threaded aperture in a housing. A threaded lock stud having a tapered external wall is constructed to fit at least partially within the hollow lock bolt
Data Source
AI summary
The present disclosure provides a multiple use threaded fastener having a plurality of redundant locking features. The fastener includes a threaded hollow lock bolt having a tapered internal wall constructed to threadingly engage a threaded aperture in a housing. A threaded lock stud having a tapered external wall is constructed to fit at least partially within the hollow lock bolt and threadingly engage the threaded aperture of the housing and engage the tapered wall of the hollow lock bolt.