Back-to-Back Spherical Bearing Assembly for Rotor Hub

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Solution Overview

Problem

Conventional rotary systems in aircraft face challenges in efficiently reacting centrifugal forces exerted by rotor blades, which can lead to increased weight and drag due to the use of solid metal bearing elements.

Innovation Solution

The implementation of a back-to-back spherical bearing assembly with a hollow spherical bearing member made of a chopped fiber composite or metal, bonded with elastomeric materials on both sides of the bearing focal point, and attached to both the rotor hub and rotor blade via inboard and outboard attachments.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Force

If solid metal bearing elements are used, then the bearing assembly can effectively react centrifugal forces, but the weight of the rotary aircraft increases

Engineering Contradiction:

Improvecentrifugal force reaction capabilityVSAvoidweight of bearing assembly

Core Design Contradiction:

ForceVSWeight of moving object

Solution Approach 1:

The bearing assembly uses a composite structure combining metal spherical bearing members with elastomeric materials. The metal components (inner and outer spherical bearing members) provide the necessary structural strength and centrifugal force reaction capability, while the elastomeric materials bonded to these surfaces provide damping and load distribution, reducing the need for excessive metal mass.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The bearing assembly is divided into distinct functional segments: inner spherical bearing member, outer spherical bearing member, and elastomeric materials. This segmentation allows each component to be optimized for its specific function - the metal spheres for structural integrity and force reaction, and the elastomeric portions for vibration damping and load distribution - thereby reducing overall weight while maintaining performance.

Inventive Principle:

Principle #1Segmentation

2Force

If traditional bearing assemblies are used, then the bearing can react blade forces, but the height of the bearing assembly increases causing increased drag

Engineering Contradiction:

Improveblade force reaction capabilityVSAvoidheight of bearing assembly

Core Design Contradiction:

ForceVSLength of moving object

Solution Approach 1:

The bearing assembly merges multiple functions into a compact configuration. The inner and outer spherical bearing members are positioned in close proximity, with elastomeric materials bonded between them, creating a compact assembly that reacts blade forces (lead/lag, coning, feathering) while minimizing the overall height and reducing aerodynamic drag.

Inventive Principle:

Principle #5Merging (Combining)

3Strength

If solid metal bearing elements are used, then the bearing assembly provides structural strength, but the weight of the rotary aircraft increases by more than three pounds

Engineering Contradiction:

Improvestructural strength of bearing assemblyVSAvoidweight of rotary aircraft

Core Design Contradiction:

StrengthVSWeight of moving object

Solution Approach 1:

The bearing assembly uses a composite structure combining metal spherical bearing members with elastomeric materials. The metal components provide the necessary structural strength to react centrifugal forces and blade loads, while the elastomeric materials contribute to load distribution and vibration damping, enabling weight reduction of more than three pounds compared to solid metal assemblies while maintaining required strength.

Inventive Principle:

Principle #40Composite materials

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

This solution reduces the weight of the rotary aircraft by more than three pounds compared to traditional solid metal bearing assemblies, while also reducing drag due to the reduced height of the bearing assembly.

Implementation Method 1

a first elastomeric and a second elastomeric bonded to the spherical bearing surface on opposite sides of the bearing focal point

Methodology Applied

Scientific EffectElasticity: Elasticity

Data Source

PatentUS12221207B2Inner member for main rotor centrifugal force bearing

Publication Date: 2025.02.11 TEXTRON INNOVATIONS INC

AI summary

A back-to-back spherical bearing assembly for a rotary system of a rotary aircraft includes a spherical bearing member having an interior cavity and a spherical bearing surface defining a bearing focal point, a first elastomeric and a second elastomeric bonded to the spherical bearing surface on opposite sides of the bearing focal point, an inboard attachment bonded to the first elastomeric and configured to be secured to a rotor hub of the rotary system, and an outboard attachment bonded to the second elastomeric and configured to be secured to a rotor blade of the rotary system.