Propeller Blade Retention via Tapered Roller Bearing Preload
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Solution Overview
Problem
Conventional propeller blade retention systems face challenges in maintaining preload over time due to stress concentrations and complex maintenance requirements, especially with the use of composite materials that reduce weight and moment capacity.
Innovation Solution
A propeller blade retention assembly utilizing a tapered roller bearing set with a floating race and end cap, applying preload along the blade axis through springs or constant load devices, allowing for stiff retention while enabling pitch changes and simplifying maintenance by minimizing stress concentrations and tool dependency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional threaded hub retention components are used to provide preload, then moment capacity is improved, but stress concentrations are introduced in the hub structure
Solution Approach 1:
The invention extracts the threaded attachment from the hub structure and relocates it to a separate retention component. The retention component with threaded attachment is positioned away from the hub, allowing the hub to be free of stress concentrations while still achieving the required moment capacity through the retention assembly.
Solution Approach 2:
The retention component serves as an intermediary element between the hub and the blade. It introduces the threaded attachment and preload mechanism while isolating the hub from direct stress concentrations, thereby protecting the hub structure while maintaining structural integrity.
2Strength
If large threaded hub retention components are used to apply preload, then moment capacity is improved, but maintenance complexity increases due to special tool requirements
Solution Approach 1:
The retention component is designed to be self-contained with integrated preload application mechanisms. Standard tools can be used to access and adjust the preload through the retention component itself, eliminating the need for special hub-specific tools and enabling maintenance personnel to service the assembly independently.
Solution Approach 2:
The retention system is segmented into a separate retainable component that can be independently accessed and maintained. This modular approach allows maintenance personnel to work on the retention component without needing to access or special工具 for the hub structure, simplifying the maintenance process.
3Weight of moving object
If non-preloaded retention systems are used with composite blades, then blade weight is reduced, but moment capacity decreases
Solution Approach 1:
The retention system applies preliminary preload to the blade root before operation. This pre-compression increases the moment capacity of the retention assembly, allowing the use of lighter composite blades while maintaining the structural strength required to handle operational loads.
Solution Approach 2:
The invention changes the preload parameter of the retention system by introducing adjustable preload mechanisms. This allows optimization of the balance between blade weight and moment capacity, enabling lighter blades to achieve sufficient moment capacity through controlled preload application rather than increasing blade mass.
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 increases moment capacity for a given pitch diameter while reducing maintenance complexity and stress concentrations, facilitating routine maintenance and repair in field environments.
Implementation Method 1
The movement along the axis of the roller elements is possible due to a combination of a low rolling coefficient of friction and a slightly tipped roller element that precesses inward in a helical path. Once the preload process is completed, the tapered roller bearing set is retained by a higher static coefficient of friction.
Implementation Method 2
The preload condition is established by a multiple of preload springs or some other relatively constant load device which apply a load on the end of the tapered rollers through the end cap
Data Source
AI summary
A propeller blade mounted with a preload adjacent a propeller blade root retention that increases the moment capacity of the retention for a given pitch diameter, yet permits pitching of the propeller blade about a blade axis in response to a propeller pitch change actuation system. During assembly, the preload condition is established by preload springs which apply a load on the end of a tapered roller bearing set as a floating race is rotated which allows the tapered roller bearing set to progressively push the propeller blade root outboard and the floating race inboard to generate the preloaded condition.