Gas Turbine Hinge Arm Repair Using Keyed Bushing
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Solution Overview
Problem
The existing methods for repairing worn hinge arms in gas turbine engine access door hinge assemblies are impractical due to the lack of sufficient material thickness for effective staking or anti-rotation features, especially when using thin-walled bushings, as they require structural thickness that is often not present in lightweight hinge assemblies.
Innovation Solution
The method involves drilling a new hole with a larger diameter and machining a keyway in the hinge arm to accommodate a keyed bushing, which provides a press-fit and anti-rotation through a staking pin or retaining compound, ensuring the bushing remains secure without weakening the hinge arm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional staking methods are used to prevent bushing rotation, then anti-rotation is achieved, but sufficient material thickness is required which is not available in lightweight hinge assemblies
Solution Approach 1:
A key is introduced as an intermediary element between the bushing and the hinge arm. The key fits into a keyway in the hinge arm and has flats that engage with corresponding features in the bushing, providing anti-rotation without requiring thick material for staking. This intermediary component enables the connection with sufficient anti-rotation capability in thin-walled structures.
Solution Approach 2:
The anti-rotation function is segmented into two parts: the keyway in the hinge arm and the key with flats in the bushing. This segmentation allows the anti-rotation feature to be distributed across multiple components rather than requiring a single thick component, enabling effective anti-rotation in lightweight assemblies.
2Reliability
If the hinge pin hole is overbored to accommodate a bushing, then the worn hole is replaced, but sufficient structural thickness must remain for effective staking
Solution Approach 1:
The key acts as an intermediary that provides anti-rotation without requiring the hinge arm to have excessive thickness. The keyway can be machined to appropriate depth and the key provides the necessary mechanical engagement, allowing the bushing to be securely installed even when material thickness is limited.
Solution Approach 2:
The keyway is created locally in the hinge arm at the specific location where the bushing is installed. This localized feature provides the necessary anti-rotation capability only where needed, rather than requiring the entire hinge arm to have increased thickness throughout, thus maintaining overall structural efficiency.
3Weight of moving object
If thin-walled bushings are used in lightweight hinge assemblies, then weight is minimized, but effective staking for anti-rotation cannot be achieved
Solution Approach 1:
The key serves as an intermediary mechanism that provides anti-rotation capability without requiring thick-walled bushings. The key with flats engages with corresponding features in both the bushing and the hinge arm, enabling reliable anti-rotation in thin-walled, lightweight assemblies.
Solution Approach 2:
The anti-rotation function is segmented between the keyway in the hinge arm and the key features in the bushing. This allows the bushing to remain thin-walled and lightweight while still achieving effective anti-rotation through the distributed key engagement mechanism.
Data Source
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AI summary
A hinge arm (232) having a hinge pin hole (33) having a worn bore, for example a hinge arm of a hinge assembly of an access door on a gas turbine engine, is repaired by forming in the worn hinge arm (232) a new hole (233) with a keyway (235) extending outwardly from the new hole (235). A keyed bushing (260) is provided having a cylindrical body (262) having a central bore (265) extending axially therethrough and a key (267) extending outwardly from the cylindrical hole body (262). The keyed bushing (260) is inserted into the new hole (233) and keyway (235) formed in the hinge arm (232) thereby preventing rotation of the bushing (260) relative to the hinge arm (232).