Composite Yoke Fitting for Rotor Blade Centrifugal Load Transfer

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Conventional rotor blade assemblies for helicopters often require additional metallic fittings and bolted joints to transfer centrifugal forces, which increase weight, complexity, and frontal cross-section, while also being less durable compared to the proposed solution.

Innovation Solution

A composite yoke fitting made from composite materials is integrated into the rotor blade, featuring an outboard portion, a flexure region, and an inboard portion with a cutout for attaching to a bearing in the rotor hub assembly, allowing the rotor blade to act as the primary load path for centrifugal forces without additional fittings.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If additional metallic fittings and bolted joints are used to transfer centrifugal forces, then the structural strength and reliability are improved, but the weight, complexity, and frontal cross-section increase

Engineering Contradiction:

Improvestructural strengthVSAvoidweight

Core Design Contradiction:

StrengthVSWeight of moving object

Solution Approach 1:

The yoke fitting is integrated directly into the rotor blade structure, merging two previously separate components (blade and yoke fitting) into a single monolithic composite structure. This eliminates the need for additional metallic fittings and bolted joints, thereby reducing weight while maintaining structural strength through the composite material's inherent properties and optimized load path design.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The invention uses composite materials for the yoke fitting integrated into the rotor blade, replacing traditional metallic fittings. The composite material provides high strength-to-weight ratio, enabling the structure to withstand centrifugal forces while significantly reducing the overall weight compared to metallic alternatives.

Inventive Principle:

Principle #40Composite materials

2Strength

If additional metallic fittings and bolted joints are used to transfer centrifugal forces, then the structural strength and reliability are improved, but the device complexity increases

Engineering Contradiction:

Improvestructural strengthVSAvoidcomplexity

Core Design Contradiction:

StrengthVSDevice complexity

Solution Approach 1:

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The invention extracts and eliminates the unnecessary metallic fittings and bolted joints from the rotor blade assembly. By removing these redundant components and relying on the integrated composite yoke fitting, the device complexity is reduced while the essential function of transferring centrifugal forces is maintained through the optimized composite structure.

Inventive Principle:

Principle #2Taking out (Extraction)

3Strength

If additional metallic fittings and bolted joints are used to transfer centrifugal forces, then the structural strength is improved, but the frontal cross-section increases

Engineering Contradiction:

Improvestructural strengthVSAvoidfrontal cross-section

Core Design Contradiction:

StrengthVSArea of moving object

Solution Approach 1:

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The composite yoke fitting is designed with locally optimized material distribution and fiber orientation to provide structural strength precisely where needed for transferring centrifugal forces. This localized reinforcement approach maintains strength while minimizing the overall frontal cross-section, as the composite material can be tailored to provide strength only in the necessary regions rather than requiring bulky metallic fittings throughout.

Inventive Principle:

Principle #3Local quality

4Strength

If additional metallic fittings and bolted joints are used to transfer centrifugal forces, then the structural strength is improved, but the durability decreases

Engineering Contradiction:

Improvestructural strengthVSAvoiddurability

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

Inventive Principle:

Principle #2Taking out (Extraction)

Data Source

PatentUS10654567B2Composite yoke fitting for bearing attachment to rotorcraft blade

Publication Date: 2020.05.19 BELL HELICOPTER TEXTRON INC

AI summary

A rotor blade assembly includes a rotor blade comprising an inboard end and an outboard end. A composite yoke fitting made from a composite material is attached to the rotor blade. The composite yoke fitting includes an outboard portion inserted into the inboard end of the rotor blade, an inboard portion, and a flexure region about which the rotor blade is configured to flex. The inboard portion and the flexure region are outside the rotor blade.