Spline Engagement Aid for Faster, Lower-Damage Shaft Assembly

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Solution Overview

Problem

Conventional spline assemblies in gas turbine engines face challenges in aligning shaft splines with hub splines due to low visibility, leading to potential damage and increased assembly time, especially under high thermal loads which shorten component life.

Innovation Solution

Incorporating a spline engagement aid with a softer material, such as plastic, featuring a tapered tip or chamfer, which is coupled to the shaft or hub via press fit, bonding, or snap-fit connection to facilitate alignment and reduce contact damage between the splines.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If conventional spline assemblies are used without alignment aids, then the structure remains simple, but alignment difficulty increases and damage risk rises

Engineering Contradiction:

Improvealignment easeVSAvoidassembly structure complexity

Core Design Contradiction:

Ease of operationVSDevice complexity

Solution Approach 1:

A separate alignment aid component is introduced as an intermediary element between the shaft and hub. This aid includes alignment features that engage with both components to guide proper positioning during assembly, reducing direct contact and damage risk between the spline elements themselves

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The alignment aid is designed to be attached beforehand to either the shaft or hub, establishing alignment references before the actual assembly operation begins. This preliminary positioning action prevents misalignment during the critical insertion phase

Inventive Principle:

Principle #10Preliminary action

2Reliability

If shaft and hub are assembled under high thermal loads, then operational conditions are met, but component life decreases due to shortened service time

Engineering Contradiction:

Improvecomponent service lifeVSAvoidthermal load conditions

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The alignment aid serves as a protective cushion during assembly, absorbing misalignment forces and reducing impact loads on the spline elements. This beforehand protection is particularly valuable when assembling under thermal conditions where material properties may be more sensitive to impact and misalignment

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Productivity

If direct shaft-to-hub assembly is performed without alignment features, then manufacturing remains simple, but assembly time increases due to alignment difficulties

Engineering Contradiction:

Improveassembly speedVSAvoidassembly feature complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The alignment aid acts as a mediator that speeds up the assembly process by providing pre-established alignment references. Rather than requiring time-consuming manual alignment of shaft and hub splines, the aid features guide proper positioning quickly and consistently

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The alignment aid replaces the need for complex mechanical alignment procedures or specialized alignment tools. The alignment features provide inherent mechanical guidance that eliminates the need for operator skill-based alignment techniques

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentEP3690253B1Spline insertion feature for assembly and damage improvement

Publication Date: 2022.11.16 RTX CORP

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AI summary

A spline assembly (100) includes a shaft (102) having an outer surface (108) with a shaft spline (110) extending along the outer surface (108). The spline assembly (100) may further include a hub (104) having an inner surface (112) with a hub spline (114) extending along the inner surface (112) and configured to mate with the shaft spline (110) of the shaft (102). The spline assembly (100) may further include a spline engagement aid (106) configured to be coupled to the shaft (102) and having an aid spline (116) configured to engage with the hub spline (114) to facilitate alignment of the shaft spline (110) relative to the hub spline (114).