Borescope Plug Offset Mounting Apertures
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Solution Overview
Problem
Borescope plugs in gas turbine engines face reduced lifespan due to high stresses at the shank, leading to decreased performance and increased maintenance costs.
Innovation Solution
The design of borescope plugs with a separable base and shank configuration, where the shank can move relative to the base, and anti-rotation elements prevent rotation, reducing stress and allowing for axial and tangential movement, along with offset mounting apertures for secure attachment to prevent upside-down installation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the borescope plug uses a fixed rigid connection between shank and base, then structural strength is improved, but stress concentration at the shank leads to reduced lifespan
Solution Approach 1:
The borescope plug is divided into separate components: a base, a shank, and a plug member, connected through a retainer system. This segmentation allows each component to independently absorb and distribute stresses, preventing stress concentration at any single location and thereby extending the overall lifespan of the plug while maintaining structural strength.
2Ease of operation
If the borescope plug uses symmetric mounting apertures, then ease of installation is improved, but incorrect orientation cannot be prevented
Solution Approach 1:
The mounting apertures in the base are positioned asymmetrically relative to the shank axis. This asymmetric arrangement ensures that the plug can only be installed in the correct orientation, as any other orientation would misalign the apertures with the mounting holes in the engine component, thereby preventing incorrect installation while maintaining ease of installation through clear alignment features.
3Adaptability or versatility
If the borescope plug allows rotational movement, then adaptability to misalignment is improved, but improper rotation cannot be prevented
Solution Approach 1:
Anti-rotation elements are pre-installed on both the shank and within the retainer before final assembly. These elements engage during installation to automatically prevent any rotational movement of the shank relative to the base, ensuring correct orientation is maintained without requiring additional adjustment or intervention during the installation process.
4Device complexity
If the borescope plug uses a unitary structure, then device complexity is reduced, but stress concentration reduces lifespan
Solution Approach 1:
The plug is segmented into multiple components (base, shank, plug member, retainer) that are assembled together. While this increases the number of parts, each component is simpler in design and can be manufactured more easily, with the overall assembly providing superior stress distribution and extended lifespan compared to a complex unitary structure.
Data Source
AI summary
Borescope plugs are described. The borescope plugs include a borescope plug base having a first side configured to support a shank and a second side having a centroid defined as the center of the borescope plug base, a first mounting aperture formed in the second side, and a second mounting aperture formed in the second side. The first and second mounting apertures are configured to each receive a fastener to mount the borescope plug base to a case, and an offset line drawn through the center of the first mounting aperture and through the center of the second mounting aperture does not pass through the centroid or does not include a point defined by the centroid.