Air Turbine Starter Decoupler to Prevent Back-Drive Re-Engagement
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Solution Overview
Problem
Conventional air-turbine starters (ATS) face reliability concerns due to mechanical clutch failures during back-drive events, leading to potential damage and the need for frequent replacement of decouplers, which increases maintenance costs and risks of unintentional re-engagement.
Innovation Solution
A reusable, manually reversible decoupler mechanism that disengages during back-drive scenarios without damaging components, featuring a locking shaft, connecting shaft, limiter cap, and dog clutch, ensuring the ATS and auxiliary gearbox remain disengaged and allowing for re-engagement without replacing parts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a mechanical clutch is used to engage the air turbine starter to the engine, then the starter can be engaged to start the engine, but the clutch may fail during back-drive events causing reliability issues and requiring frequent replacement
Solution Approach 1:
The patent replaces the traditional mechanical clutch system with a decoupler mechanism that uses a connecting shaft, locking shaft, and dog clutch arrangement. This new mechanical system eliminates the reliability issues of conventional clutches during back-drive events while maintaining the necessary engagement functionality. The decoupler uses a combination of shafts and clutch elements that prevent the failure modes associated with traditional mechanical clutches.
Solution Approach 2:
The patent introduces a decoupler mechanism as an intermediary component between the air turbine starter and the engine. This decoupler includes a connecting shaft, locking shaft, and dog clutch that act as a mediator to prevent direct engagement failures. The intermediary decoupler mechanism absorbs the back-drive forces and prevents them from damaging the starter or engine, thereby improving reliability without significantly increasing overall system complexity.
2Reliability
If the decoupler is replaced frequently due to wear and failure, then reliability is maintained, but maintenance costs increase and risk of unintentional re-engagement occurs
Solution Approach 1:
The decoupler mechanism is designed to be manually reversible, allowing operators to re-engage the system without requiring part replacement. The self-service design enables the decoupler to maintain its functional integrity through multiple engagement cycles, eliminating the need for frequent replacements and reducing maintenance time while preserving reliability.
Solution Approach 2:
The patent designs the decoupler components (connecting shaft, locking shaft, dog clutch) to be recoverable and reusable rather than disposable. The mechanism allows for manual disengagement and re-engagement without damaging the components, enabling them to be recovered and reused multiple times. This eliminates the need for frequent replacement while maintaining system reliability.
3Ease of manufacture
If a reusable decoupler mechanism is implemented, then maintenance costs reduce and component lifespan extends, but the device complexity increases
Solution Approach 1:
The decoupler mechanism is segmented into distinct functional components: a connecting shaft for power transmission, a locking shaft for engagement control, and a dog clutch for securing the connection. This segmentation allows each component to be manufactured separately using standard machining processes, reducing overall manufacturing cost while distributing the complexity across manageable individual parts rather than a single complex assembly.
Data Source
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AI summary
An air turbine starter (10) for starting an engine (14), comprising a housing (30) defining an inlet (32), an outlet (34), and a flow path (36) extending between the inlet (32) and the outlet (34) for communicating a flow of gas there through. A turbine member (38) is journaled within the housing (30) and disposed within the flow path (36) for rotatably extracting mechanical power from the flow of gas and a gear train (40) is drivingly coupled with the turbine member (38). A drive shaft (64) is operably coupled with the gear train (40), and a decoupler (70) is selectively coupled to the drive shaft (64) for decoupling the air turbine starter (10) from the engine (14).