Bellows Drive Shaft Fusible Section for Aircraft Overtorque Protection

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Solution Overview

Problem

Turbomachines with reduction gearboxes face challenges in protecting drive shafts from overtorque due to sudden seizures, which can lead to transmission line breakage, and existing solutions increase the machine's dimensions and mass.

Innovation Solution

A drive shaft design with a fusible section in the connecting means, featuring a through orifice that breaks when the torque exceeds a threshold, providing both overtorque protection and oil drainage without increasing overall dimensions or manufacturing costs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a fusible section is integrated in the transmission line downstream of the reduction gearbox, then overtorque protection is improved, but the device complexity increases

Engineering Contradiction:

Improveover torque protectionVSAvoiddevice complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The fusible section is integrated directly into the bellows structure of the drive shaft, merging the overtorque protection function with the existing flexible coupling component. This eliminates the need for separate protection devices and reduces overall device complexity while maintaining reliability.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The bellows structure serves multiple functions: providing flexibility for vibratory isolation and simultaneously acting as the fusible section for overtorque protection. This multi-functionality reduces the number of components needed and simplifies the overall device architecture.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Stability of the object's composition

If the drive shaft is separated into two portions connected by bellows to achieve suppleness, then vibratory isolation is improved, but the device complexity increases

Engineering Contradiction:

Improvevibratory isolationVSAvoiddevice complexity

Core Design Contradiction:

Stability of the object's compositionVSDevice complexity

Solution Approach 1:

The bellows structure is integrated directly into the drive shaft, merging the flexible coupling function with the drive shaft itself. This eliminates the need for separate flexible coupling components and reduces device complexity while maintaining vibratory isolation performance.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The bellows provides flexibility through its corrugated structure, allowing the drive shaft to accommodate vibratory movements and misalignments. This flexible shell design enables suppleness without requiring complex mechanical joints or multiple separate components.

Inventive Principle:

Principle #30Flexible shells and thin films

3Reliability

If a decoupling means is integrated in the transmission line, then overtorque protection is improved, but the manufacturing cost increases

Engineering Contradiction:

Improveover torque protectionVSAvoidmanufacturing cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The fusible section is integrated into the existing bellows manufacturing process, merging two functions into a single component. This eliminates the need for separate protection devices and reduces overall manufacturing cost while maintaining overtorque protection capability.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The fusible section utilizes the existing bellows material and geometry, changing only local parameters (such as wall thickness or material properties in specific zones) to create the fusible characteristic. This approach is more cost-effective than introducing entirely new components or materials.

Inventive Principle:

Principle #35Parameter changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The solution effectively decouples the drive shaft portions during overtorque, protecting the transmission line while maintaining the turbomachine's compactness and reducing the risk of oil imbalance.

Implementation Method 1

the first section comprises at least one fusible section configured to break when a value of a torque applied to the first portion exceeds a predetermined threshold value

Methodology Applied

Scientific EffectFracture Mechanics: Fracture Mechanics

Implementation Method 2

the first section comprises at least one fusible section comprising at least one through orifice configured to break when a value of a torque applied to the first portion exceeds a predetermined threshold value

Methodology Applied

Scientific EffectGravity-driven flow: Gravitation

Data Source

PatentUS11808212B2Drive shaft comprising a fusible section and method for protecting such a drive shaft against an overtorque

Publication Date: 2023.11.07 SAFRAN AIRCRAFT ENGINES SAS

AI summary

A drive shaft of an aircraft turbine engine includes a first portion and a second portion, and connecting means connecting the first and second portions and being configured to transmit a torque from the second portion to the first portion. The connecting means has at least one bellows with a first section having a diameter greater than the diameters of the first and second portions and second sections flanking the first section. The first section includes at least one fusible section with at least one through-hole and being configured to break when the value of a torque applied to the first portion exceeds a predetermined threshold value.