Radially Nested Torque Limiter for Aircraft Shaft Accessories
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Solution Overview
Problem
Conventional torque limiting devices are unsuitable for propulsion systems of rotary wing aircraft due to size constraints, large operating temperature range, and small torque limits, making it difficult to implement them effectively in such applications.
Innovation Solution
A torque limiting device with a radially nested configuration, featuring a bushing with a flange and a cartridge assembly with pre-loaded axial springs, which applies a biasing force to selectively couple the drive shaft and rotor, preventing catastrophic failures by allowing relative rotation when excessive torque is applied.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional torque limiting devices (keyways, shaft section shearing) are used, then torque limiting function is provided, but size constraints and tight tolerances cannot be met
Solution Approach 1:
The torque limiting device is radially nested between the drive shaft and the rotor, with the cartridge assembly containing multiple axial springs arranged in parallel within a compact cylindrical structure. This nesting approach allows the torque limiting function to be integrated into the existing space without adding significant volume to the propulsion system.
2Reliability
If conventional torque limiting devices are used, then torque limiting function is provided, but they cannot operate reliably across large temperature ranges
Solution Approach 1:
The axial springs are pre-loaded to specific force values that account for thermal expansion and contraction across the operating temperature range. The biasing force generated by the springs changes with temperature, but the device is designed to maintain reliable torque limiting function throughout the large temperature range experienced in propulsion systems.
3Reliability
If conventional torque limiting devices are used, then torque limiting function is provided, but they are unsuitable for small torque limits
Solution Approach 1:
Multiple axial springs are distributed around the circumference of the cartridge assembly, each contributing to the overall biasing force. This distribution allows for precise control of the torque limit by adjusting the number, stiffness, and pre-load of individual springs, making the device suitable for applications with small torque limits and tight tolerances.
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 device provides reliable torque control within tight tolerances and a wide temperature range, preventing drive shaft shearing and allowing for factory testing to detect and remove foreign objects, thus ensuring system safety and efficiency.
Implementation Method 1
The second portion includes a plurality of pre-loaded axial springs and is coupled to a second rotatable component
Implementation Method 2
The second portion is configured to apply a biasing force to the flange to selectively couple the first rotatable component and the second rotatable component
Data Source
AI summary
A torque limiting device includes a first portion connected to a first rotatable component. The first portion has a flange extending radially outward therefrom. A second portion includes a plurality of pre-loaded axial springs and is coupled to a second rotatable component. The second portion is arranged adjacent opposing surfaces of the flange. The second portion is configured to apply a biasing force to the flange to selectively couple the first rotatable component and the second rotatable component.