Air Turbine Starter Gear Cage Alignment Feature
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Solution Overview
Problem
Conventional air turbine starter systems face challenges in securely retaining a planetary gear system due to continuous force transmission to the same angular portion of planet shafts, leading to potential misalignment and instability, which can affect the efficient starting of gas turbine engines, especially in weight-sensitive applications like aircraft propulsion.
Innovation Solution
A gear cage assembly comprising a main plate with legs and a back plate, featuring shallow openings and bearing holes, along with a biasing mechanism and alignment features, is designed to securely mount and align planet gears, ensuring proper retention and alignment through a pin and bushing system, and fasteners, thereby stabilizing the planetary gear system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional planetary gear systems are used with stationary shafts, then the structure is simple, but continuous force transmission to the same angular portion causes misalignment and instability
Solution Approach 1:
The planet shafts are made rotatable within the gear cage assembly, allowing them to dynamically adjust their angular position. This dynamic capability enables the shafts to rotate and realign themselves, distributing continuous forces to different angular portions and preventing misalignment instability while maintaining structural simplicity
Solution Approach 2:
Alignment features are pre-configured on the planet shafts and gear cage assembly to guide proper alignment during assembly. The biasing mechanism is pre-installed to automatically apply aligning forces, ensuring correct positioning before operational loads are applied, thereby preventing misalignment from the outset
2Productivity
If force is continuously transmitted to the same angular portion of planet shafts, then power transmission is efficient, but misalignment and instability occur
Solution Approach 1:
The rotatable planet shafts enable the system to dynamically redistribute continuous forces to varying angular portions during operation. This maintains efficient power transmission by keeping the planetary gears engaged while preventing misalignment through continuous angular adjustment, resolving the contradiction between efficiency and stability
Solution Approach 2:
As the planet shafts rotate within the gear cage assembly, the force transmission point periodically shifts to different angular portions. This periodic redistribution prevents continuous loading of the same angular portion, maintaining transmission efficiency while eliminating misalignment issues through cyclic realignment
Data Source
AI summary
A gear cage assembly configured to support a plurality of planet gear in an air turbine starter is provided including a main plate and a back plate. The main plate includes a plurality of legs that extend from a first surface. A pin protrudes from a one of the plurality of legs. A plurality of shallow openings formed in the first surface extends over only a portion of a depth of the main plate. The back plate includes a plurality of bearing holes substantially identical to the plurality of shallow openings. A biasing mechanism and at least one alignment feature protrude from the back plate. The at least one alignment feature and the biasing mechanism are configured to contact at least one of the plurality of legs. A bushing mounted within the back plate is configured to receive the pin.