Splined Shaft Piloting Features for Seal Alignment Control
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Solution Overview
Problem
Misalignment between shafts in aircraft shaft assemblies leads to performance issues and wear in input seals and mating rings, particularly in the operational coupling of accessory gearboxes and generators in gas turbine engines.
Innovation Solution
A splined shaft assembly with piloting features, where the radial inner and outer facing splines and projections are designed to be equal in height and mesh perfectly, ensuring perpendicular alignment of mating ring assemblies and input seal assemblies, thereby preventing misalignment and maintaining optimal sealing performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If shafts are connected using conventional spline couplings without additional piloting features, then the structure is simpler, but misalignment occurs between the shafts leading to seal performance degradation and wear
Solution Approach 1:
The shaft assembly is segmented into multiple functional components: the drive shaft with outer splines, the driven shaft with inner splines, and additional piloting features including radial projections and seats. This segmentation allows each component to perform its specific function - torque transmission through splines and alignment through projections - thereby resolving the contradiction between structural simplicity and alignment precision.
Solution Approach 2:
Radial projections and seats are introduced as intermediary features between the drive shaft and driven shaft. These intermediaries provide additional piloting functions that ensure precise alignment and perpendicularity of the shafts, preventing misalignment issues while maintaining a relatively simple overall structure. The projections act as mediators that transmit alignment information and constrain relative position.
2Manufacturing precision
If shafts are aligned precisely using conventional alignment methods, then misalignment is reduced, but the manufacturing and assembly process becomes more complex and time-consuming
Solution Approach 1:
Alignment features (radial projections and seats) are built into the shaft assembly design during manufacturing, so that alignment is achieved automatically during assembly without requiring separate alignment operations. The projections are pre-positioned on the drive shaft and the seats are pre-formed on the driven shaft, ensuring precise perpendicularity and alignment is accomplished as a natural result of the assembly process rather than through complex adjustment procedures.
Data Source
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AI summary
A shaft assembly having: a first shaft (170) with an inner facing surface having: an inner facing spline (190) extending between spline ends; an inner facing projection, adjacent to one of the spline ends, extending to an inner facing projection surface; and an inner facing projection seat, adjacent to another of the spline ends; and a second shaft (250) having an outer facing surface having: an outer facing spline (270) extending between spline ends; an outer facing projection, adjacent to one of the spline ends of the outer facing spline (270), extending to an outer projection surface; and an outer facing projection seat, adjacent to another of the ends of the outer facing spline (270); the first shaft (170) at least partially surrounds the second shaft (250); the inner facing projection surface is disposed against the outer facing projection seat; and the outer facing projection surface disposed against the inner facing projection seat.