Serrated Locking Nut Assembly for Aircraft Turbine Retention
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Solution Overview
Problem
Existing fastener systems for aircraft turbines lack a reliable and efficient mechanism to securely retain and axially load spline adapters and shaft bearings, leading to potential loosening under operational conditions such as vibrations.
Innovation Solution
A locking nut assembly comprising a bearing nut, a shaft nut, and a locking collar with serrated surfaces that engage in an interference fit, providing a secure axial load and retention through a saw-tooth pattern of teeth and notches, along with a retaining ring for additional stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional fastener systems are used to retain spline adapters and shaft bearings, then the structure is simple, but the reliability is insufficient due to potential loosening under vibrations
Solution Approach 1:
The fastening system is divided into multiple functional components: a bearing nut with external serrations, a shaft nut with external serrations, and a locking collar with internal serrations. Each component performs a specific function, collectively providing secure retention while distributing mechanical stresses.
Solution Approach 2:
The serrated surfaces feature asymmetric saw-tooth patterns with teeth and notches designed to engage in specific directions. The teeth point toward the notches of mating components, creating a mechanical interlock that prevents loosening under vibrational loads while allowing controlled assembly.
2Reliability
If a secure retention mechanism is implemented using multiple nuts and locking collars, then the reliability improves, but the ease of operation deteriorates due to complex installation and alignment
Solution Approach 1:
The serrated surfaces are designed with asymmetric tooth and notch patterns that naturally guide alignment during installation. The teeth of one component fit into the notches of the mating component, providing self-aligning features that simplify the installation process while ensuring reliable engagement.
Solution Approach 2:
The interference fit between the serrated surfaces creates self-locking behavior during installation. As the components are assembled, the serrations automatically engage and lock together through the interference fit, reducing the need for additional locking mechanisms or complex installation procedures.
3Strength
If serrated surfaces with interference fit are used to distribute axial loads, then the strength improves, but the manufacturing precision requirements worsen due to tight tolerance needs
Solution Approach 1:
The saw-tooth serration pattern with asymmetric teeth and notches provides a tolerance buffer. The directional engagement of teeth into notches allows for some variation in manufacturing dimensions while maintaining effective load distribution, reducing the stringency of precision requirements compared to symmetric mating surfaces.
Solution Approach 2:
The serrated surfaces are designed with curved tooth profiles and rounded notch geometries that facilitate gradual engagement during assembly. The curved surfaces allow for self-adjustment and stress distribution, accommodating manufacturing variations while maintaining structural integrity under axial loads.
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 locking nut assembly effectively secures spline adapters and shaft bearings by distributing axial loads and preventing loosening due to vibrations, ensuring reliable operation in aircraft turbines.
Implementation Method 1
a first plurality of serrations on an exterior surface of the bearing nut, a second plurality of serrations on an exterior surface of the shaft nut, and a third plurality of serrations on an interior surface of the locking collar
Implementation Method 2
The engagement of the first plurality of serrations of the bearing nut and the second plurality of serrations of the shaft nut with the third plurality of serrations of the locking collar is an interference fit
Data Source
AI summary
A locking nut assembly including a bearing nut having a plurality of external serrations, a shaft nut having a plurality of external serrations, and a locking collar having a plurality of internal serrations. The bearing nut and the shaft nut are threadedly installed on a shaft assembly having an impeller, a bearing, and a spline adapter installed within the impeller. The plurality of serrations of the bearing nut align with the plurality of serrations of the shaft nut when they are installed on the impeller. The locking collar is installed on the bearing nut and the shaft nut so that the aligned plurality of serrations of the bearing nut and the plurality of serrations of the shaft nut engage the plurality of serrations of the locking collar. The locking collar is retained on the bearing nut and shaft nut by a retaining ring.