Fusibly Breakable Bolt for Gearbox Mounting Link

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Conventional gearbox connections in aircraft gas turbine engines are unable to effectively absorb extreme loads from 'blade-off' events without causing damage or oil leakage, as they are designed to rigidly withstand all anticipated loads, leading to potential detachment and increased risk of damage.

Innovation Solution

A gearbox mounting link featuring a fusibly breakable bolt with a shear section and secondary retention annuli, which allows for increased mobility and absorption of extreme shocks by shearing under extreme loads, preventing detachment and destructive load transmission.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If conventional gearbox connections are designed to rigidly withstand all anticipated loads, then strength and reliability are improved, but the risk of damage and oil leakage increases under extreme loads

Engineering Contradiction:

ImprovestrengthVSAvoiddamage risk

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

The bolt is segmented into a shear section and outer sections, allowing different parts to have different functions. The shear section is designed to fail under extreme loads while the outer sections remain intact, protecting the gearbox from complete detachment and oil leakage.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention converts the harmful effect of extreme loads into a beneficial protective mechanism. When extreme loads are detected, the shear section fails in a controlled manner, sacrificing itself to protect the gearbox and prevent oil leakage, thus turning potential damage into a protective action.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

2Object-affected harmful factors

If a fusibly breakable bolt with shear section is used to absorb extreme loads, then damage risk is reduced, but device complexity increases

Engineering Contradiction:

Improvedamage riskVSAvoiddevice complexity

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The bolt is divided into functional segments (shear section and outer sections) with distinct roles. This segmentation allows the complex protective function to be achieved through a relatively simple structural modification rather than a completely complex system.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The shear section acts as a disposable protective element that sacrifices itself under extreme loads. This simple, replaceable component provides complex protective functionality at low cost and structural complexity, preventing damage to the expensive gearbox.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Reliability

If primary retention annuli tightly retain outer sections while secondary retention annuli loosely retain shear section, then reliability is improved, but manufacturing precision requirements increase

Engineering Contradiction:

ImprovereliabilityVSAvoidmanufacturing precision

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

Different retention characteristics are applied to different parts of the bolt. The primary retention annuli provide tight retention for the outer sections, while the secondary retention annuli provide loose retention for the shear section. This local differentiation of retention quality achieves high reliability without requiring uniform high precision throughout the entire assembly.

Inventive Principle:

Principle #3Local quality

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 enables the gearbox mounting link to absorb extreme shocks without detaching from the engine, reducing damage and preventing the transmission of destructive loads, thereby enhancing safety and reducing maintenance needs.

Implementation Method 1

The shear section mates with the gearbox arm... in the event of the shear section separating from the outer sections

Methodology Applied

Scientific EffectShear stress: Shear Stress

Data Source

PatentUS10215100B2One degree-of-constraint semi-fusible gearbox mounting link

Publication Date: 2019.02.26 HAMILTON SUNDSTRAND CORP

AI summary

A mounting link between a gas turbine engine and a gearbox comprises a gearbox arm, a fusibly breakable bolt, and two engine attachment brackets. The gearbox arm attaches to the gearbox, and extends along an axis defining a first dimension between the gas turbine engine structure and the gearbox. The fusibly breakable bolt extends through the gearbox arm, and has a central shear section that mates with the gearbox arm. The engine attachment brackets have primary and secondary retention annuli, and attachment flanges that attach to the gas turbine engine structure. The primary retention annuli are each concentric to an outer section of the fusibly breakable bolt, and have a radius selected to tightly retain those outer sections in the first dimension. The secondary retention annuli are each concentric to a portion of the shear section, and have a larger radius to loosely retain the shear section.