Self-Retaining Bushing Assembly for Gas Turbine Engines
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Solution Overview
Problem
The existing bushing design in gas turbine engines is prone to cracking between the flange and the bushing, leading to improper operation or damage as the bushing can drop radially inward, causing it to become improperly located.
Innovation Solution
A self-retained bushing design featuring a reduced-diameter band and groove configuration that blocks movement relative to the housing, preventing radial inward movement even if the flange separates, ensuring the bushing remains securely in place.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a flange is used to locate the bushing against the housing, then the bushing is positioned correctly, but cracks can form between the flange and bushing causing the bushing to drop radially inward
Solution Approach 1:
The bushing is segmented into multiple sections along its length, with at least one section having a reduced diameter. This segmentation allows the bushing to be retained by multiple features along its length rather than relying on a single flange-bushing joint, distributing the retention function and eliminating the weak joint that was prone to cracking.
Solution Approach 2:
A reduced-diameter band is introduced as an intermediary feature between the bushing and the housing bore. This band creates a mechanical interlock through the groove configuration that prevents radial movement without requiring a fragile flange-bushing joint, serving as a mediator that provides retention through geometry rather than through a vulnerable connection.
2Reliability
If a barbed configuration is used at the inner end of the bushing, then extraction in the radially outward direction is prevented, but the design still allows radial inward movement if the flange separates
Solution Approach 1:
The bushing structure is segmented with reduced-diameter sections distributed along its length rather than concentrating all retention features at one end. This segmentation provides multiple retention points that work together to prevent both inward and outward movement, improving reliability without significantly increasing complexity.
Solution Approach 2:
The reduced-diameter groove configuration serves multiple functions simultaneously: it prevents radial inward movement, prevents radial outward movement, and provides location along the bore. This multi-functionality replaces the need for separate flange and barb features, reducing overall structural complexity while improving retention reliability.
3Reliability
If a flange is used to prevent radial inward movement, then positioning is maintained, but manufacturing requires undercuts which increase cost
Solution Approach 1:
Instead of using a flange that protrudes outward to provide retention, the design inverts the approach by using reduced-diameter sections that create retention through the groove configuration within the bore. This inversion eliminates the need for undercuts in the housing, simplifying manufacturing while maintaining reliable positioning.
Solution Approach 2:
The diameter parameter of the bushing is varied along its length to create reduced-diameter sections. This parameter change enables the groove configuration to provide mechanical interlock and retention without requiring complex housing features like undercuts, making the overall assembly easier to manufacture while maintaining reliable bushing positioning.
Data Source
AI summary
A bushing apparatus includes: a housing with first and second ends, the housing having an outer bore passing therethrough from the first end to the second end, wherein the bore includes a reduced-diameter band located between the first and second ends; and a bushing received in the outer bore, the bushing having first and second ends and an inner bore passing therethrough from the first end to the second end of the bushing, wherein the bushing includes an outer surface having a reduced-diameter groove located between the first and second ends, wherein the band is received in the groove in a radially overlapping relationship, so as to block movement of the bushing relative to the housing.