Blade-root bearing preload and geometry optimization

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Solution Overview

Problem

Existing blade root bearings in aircraft propellers face challenges with effective sealing and assembly, leading to risks of incorrect preload and premature failures due to complex architectures and user-assembled components.

Innovation Solution

A redesigned blade root bearing with a loading system using an annular plate and screws to maintain axial preload, combined with specific geometric configurations of rolling bodies and raceways, optimizing the distance and angle of rolling bodies to enhance axial load transfer and minimize bulk.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If a complex bearing architecture with numerous assembled parts is used, then the bearing can support the required loads, but effective sealing becomes difficult and assembly risks increase

Engineering Contradiction:

Improveload bearing capacityVSAvoidsealing effectiveness

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The patent merges multiple bearing components into a more integrated structure. The bearing assembly includes a housing, blade root, and rolling elements that work together as a unified system, reducing the number of separate parts that need sealing interfaces while maintaining load bearing capacity.

Inventive Principle:

Principle #5Merging (Combining)

2Strength

If a complex bearing architecture with numerous assembled parts is used, then the bearing can support the required loads, but assembly complexity and risk of incorrect assembly increase

Engineering Contradiction:

Improveload bearing capacityVSAvoidassembly complexity

Core Design Contradiction:

StrengthVSDevice complexity

Solution Approach 1:

The bearing is pre-assembled as a complete unit at the factory with proper preload applied to the rolling elements. This preliminary assembly ensures correct configuration and eliminates the need for end-user assembly operations that could introduce errors, while still providing the required load bearing capacity.

Inventive Principle:

Principle #10Preliminary action

3Reliability

If the bearing is pre-assembled with preload at the factory, then assembly reliability improves, but the user cannot adjust the preload themselves

Engineering Contradiction:

Improveassembly reliabilityVSAvoidadjustability

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The bearing is designed to be self-contained with factory-applied preload that requires no user adjustment. The system serves itself by maintaining proper preload through its integrated design, eliminating the need for user intervention while ensuring reliable operation.

Inventive Principle:

Principle #25Self-service

4Volume of stationary object

If the bearing volume is reduced to minimize bulk, then space efficiency improves, but the bearing may not withstand the required forces

Engineering Contradiction:

Improvebearing volumeVSAvoidforce withstanding capacity

Core Design Contradiction:

Volume of stationary objectVSStrength

Solution Approach 1:

The patent optimizes the bearing geometry and material properties to achieve high strength-to-volume ratio. By carefully selecting parameters such as rolling element size, raceway geometry, and material characteristics, the bearing maintains force withstanding capacity while minimizing overall volume for space efficiency.

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 ensures reliable axial load transfer and reduced bulk, minimizing the risk of premature failures while allowing for efficient assembly and operation under centrifugal forces.

Implementation Method 1

provision is made to preload the bearings, that is to say to create and maintain compression of their rolling bodies between their raceways

Methodology Applied

Scientific EffectAxial preload: Mechanical Force

Implementation Method 2

First and second rows of rolling bodies, with oblique contact, are mounted between a skirt encircling the foot, and a respective cup and outer ring

Methodology Applied

Scientific EffectRolling contact: Friction

Implementation Method 3

When the propeller turns, the blade undergoes two actions: a centrifugal or axial force for the blade and the bearing, depending on its speed of rotation and its mass

Methodology Applied

Scientific EffectCentrifugal force: Centrifugal Force

Implementation Method 4

a bending moment at the root of the blade due to a radial force on the blade resulting from the interaction of the blade and the air she brews

Methodology Applied

Scientific EffectBending moment: Mechanical Force

Data Source

PatentEP3153730B1Blade-root bearing, oscillating system and rotating system

Publication Date: 2019.12.04 NTN SNR ROULEMENTS

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AI summary

A blade root extends along a longitudinal direction (B) between a proximal end and a distal end. The bearing allows the root to oscillate about an axis (B) extending along the longitudinal direction relative to a housing. The bearing comprises a single outer ring (13), a first inner ring (11) having a distal seat (16), and a second inner ring (12) pressed onto the seat (16) and axially held against the first inner ring (11). The inner surface (14) of the first inner ring (11) includes a shoulder (20) for mounting to a blade root. The outer surface (34) of the single outer ring (13) includes a shoulder (39) for mounting to a housing.