Actuator Piston Fail-Fix Assembly for Last-Position Holding
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Solution Overview
Problem
Actuator assemblies in turbo machines experience undesired movement and operational failures due to loss of input signal or pressure, leading to uncommanded changes in vane angle, which can cause stalls or surges, and existing fail-fix systems are heavy and complex.
Innovation Solution
An actuator assembly with a fail-fix system that includes a piston assembly with a spring and friction mechanism, coupled with a control valve assembly to maintain or disable motive fluid flow, preventing undesired movement by engaging the piston with the input drive assembly via a friction mechanism when the signal is lost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fail-fix system is implemented to prevent undesired movement after actuator failure, then reliability is improved, but device complexity increases
Solution Approach 1:
The fail-fix mechanism is merged with the piston assembly by integrating the friction mechanism directly into the piston structure. The piston body incorporates friction surfaces that engage with the input drive assembly, eliminating the need for separate fail-fix components and reducing overall system complexity while maintaining reliability.
Solution Approach 2:
The piston assembly is designed to perform multiple functions: it serves as both the actuating element for normal operation and as the fail-fix mechanism through its integrated friction surfaces. This multi-functionality allows a single component to provide both operational movement and failure protection, reducing the need for additional dedicated fail-safe components.
2Reliability
If multiple separate components are used for fail-fix system, then reliability is improved, but weight increases
Solution Approach 1:
The fail-fix function is combined with the existing piston assembly rather than using separate components. The friction mechanism is integrated into the piston body structure, meaning the same mass that provides actuation functionality also provides fail-fix capability, eliminating the need for additional dedicated components that would increase weight.
3Device complexity
If friction mechanism is integrated into piston assembly, then device complexity is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The friction surfaces are localized to specific areas of the piston assembly where precise control is most critical. By concentrating the friction mechanism at defined interfaces between the piston and input drive assembly, the precision requirements are focused on specific local regions rather than requiring high precision throughout the entire component, making manufacturing more feasible.
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 system effectively mitigates undesired movement and maintains the last commanded position of the output shaft, reducing the risk of stalls and surges in turbo machines by engaging the piston with the input drive assembly through a friction mechanism after loss of signal, while also reducing system weight and complexity.
Implementation Method 1
The piston assembly includes a spring disposed at the first end between the body and the piston
Implementation Method 2
The piston assembly includes a friction mechanism disposed at the second end of the piston opposite of the first end
Data Source
AI summary
An actuator assembly including a fail-fix system is provided. The actuator assembly includes an output shaft, an input drive assembly, and a piston assembly. The piston assembly includes a body surrounding a piston moveable within the body. The body defines a first end and a second end opposite thereof between which the piston is moveable within the body. The piston assembly includes a spring disposed at the first end between the body and the piston. The piston assembly includes a friction mechanism disposed at the second end of the piston opposite of the first end. An adjustable area is defined within the body between the second end of the piston and the input drive assembly.