Integral Multistage Ring Gear Structure for Compact Aircraft Gearboxes

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Solution Overview

Problem

Current multistage planetary gear systems for aerospace applications are heavy, space-consuming, and prone to joint failure due to the use of structurally separate ring gears bolted to a housing, which increases weight and space penalties and the risk of joint failure under radial loads.

Innovation Solution

An integral multistage ring gear system with a flanged end and a cantilevered end is monolithically formed from a homogeneous material, jointlessly connecting multiple stages and using a spacer ring and tuning stiffener to decouple flexibilities, reducing the number of flanges and joints, and incorporating flex walls to absorb radial loads.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If structurally separate ring gears are bolted to a housing, then the gear system can be assembled from discrete parts, but the weight and space increase due to multiple flanges and bolted joints

Engineering Contradiction:

Improveassembly from discrete partsVSAvoidweight of ring gear system

Core Design Contradiction:

Ease of manufactureVSWeight of moving object

Solution Approach 1:

The patent merges multiple separate ring gears and flanges into a single integral multistage ring gear system. The first and second ring gears are formed as one monolithic structure, eliminating the need for separate flanges and bolted connections, thereby reducing weight while maintaining structural integrity

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The integral ring gear system performs multiple functions: it supports both the first and second ring gears, provides structural housing integration, and eliminates the need for separate fastening components. This multi-functionality reduces the overall component count and weight

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Reliability

If multiple flanges are used to support ring gears, then the ring gears can be securely mounted, but the space penalty increases

Engineering Contradiction:

Improvemounting security of ring gearsVSAvoidspace occupied by flanges

Core Design Contradiction:

ReliabilityVSVolume of moving object

Solution Approach 1:

Multiple flange structures are merged into a single integrated housing structure that supports both ring gears. The integral design consolidates the mounting function into one compact structure, reducing the overall volume required while maintaining secure mounting

Inventive Principle:

Principle #5Merging (Combining)

3Ease of manufacture

If bolted joints are used at each ring gear, then the ring gears can be attached to the housing, but the risk of joint failure increases due to radial loads

Engineering Contradiction:

Improveattachment methodVSAvoidjoint failure risk

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent eliminates bolted joints by merging the ring gears directly into the integral housing structure. The monolithic construction removes all intermediate fastening joints, eliminating the failure points that would otherwise exist at bolted connections under radial loads

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent extracts and removes the bolted joint elements entirely from the design. By taking out the fastening components and using direct integral construction, the design eliminates the source of joint failure while maintaining the attachment function

Inventive Principle:

Principle #2Taking out (Extraction)

4Ease of manufacture

If structurally separate ring gears are used, then each ring gear can be independently manufactured, but the overall system weight increases

Engineering Contradiction:

Improveindependent manufacturing of ring gearsVSAvoidweight of ring gear system

Core Design Contradiction:

Ease of manufactureVSWeight of stationary object

Solution Approach 1:

The patent combines multiple separately manufacturable ring gears into one integral structure. While this changes the manufacturing approach from multiple independent parts to a single monolithic component, the weight reduction from eliminating flanges and fasteners outweighs the manufacturing complexity increase

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS11186381B2Integral multistage ring gear systems for aircraft

Publication Date: 2021.11.30 TEXTRON INNOVATIONS INC

AI summary

A drivetrain for an aircraft includes an engine, a driveshaft to receive rotational energy from the engine and a gearbox including a multistage planetary gear system to receive rotational energy from the driveshaft. The multistage planetary gear system includes an integral multistage ring gear system having flanged and cantilevered ends. The integral multistage ring gear system forms a first stage ring gear at the cantilevered end and a second stage ring gear interposed between the flanged end and the first stage ring gear. The multistage planetary gear system includes a first stage sun gear, first stage planet gears and a first stage carrier. The first stage planet gears mate with the first stage ring gear. The multistage planetary gear system includes a second stage sun gear, second stage planet gears and a second stage carrier. The second stage planet gears mate with the second stage ring gear.