Spherical Lined Bearings for Tail Rotor Yoke Arms

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Solution Overview

Problem

Conventional tail rotary systems face failure due to feathering stresses on yoke arms from rigidly attached rotor blades, which restrict movement and lead to undesired yaw control in rotary aircraft.

Innovation Solution

The implementation of spherical lined bearings aligned linearly on yoke arms to allow feathering movement while restricting longitudinal and transverse movements, with cutouts in the bearing housing to enhance pivoting capability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If rotor blades rigidly attach to the yoke arms, then rotor blade feathering movement is restricted, but the system becomes prone to failure due to feathering stresses on the yoke arm

Engineering Contradiction:

Improvesystem reliabilityVSAvoidyoke arm stress resistance

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent introduces spherical lined bearings as an intermediary component between the rotor blade and yoke arm. These bearings allow controlled feathering movement while supporting the blade weight, mediating between the need for movement restriction and stress reduction. The bearing housing with cutouts provides the intermediate structure that enables both functions simultaneously.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent transitions from a static rigid connection to a dynamic articulated connection. The spherical bearings enable the rotor blade to dynamically adjust its angle during operation, allowing feathering movement when needed while maintaining structural support. This dynamic capability resolves the contradiction by making the connection adaptable rather than fixed.

Inventive Principle:

Principle #15Dynamics

2Strength

If rotor blades are rigidly attached to the yoke arms, then structural strength is maintained, but feathering stresses cause undesired yaw control and potential failure

Engineering Contradiction:

Improvestructural strengthVSAvoidyaw control precision

Core Design Contradiction:

StrengthVSEase of operation

Solution Approach 1:

The patent segments the rigid connection into multiple functional components: the bearing assembly, the spherical element, and the lined housing with cutouts. This segmentation allows each component to handle specific functions - the spherical element permits feathering, the lined housing provides structural support, and the cutouts enable controlled movement - collectively achieving both strength and control precision.

Inventive Principle:

Principle #1Segmentation

3Reliability

If spherical lined bearings with cutouts are implemented, then feathering movement is allowed and stress is reduced, but device complexity increases

Engineering Contradiction:

Improvetail rotor durabilityVSAvoidbearing structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent employs spherical geometry for the bearing element, which inherently provides the needed rotational freedom for feathering movement. The spherical shape naturally accommodates angular adjustments without requiring complex mechanical linkages, reducing overall system complexity while maintaining the desired movement capability and stress reduction.

Inventive Principle:

Principle #14Spheroidality (Curvature)

Data Source

PatentUS10502262B2Increased capacity spherical lined bearings

Publication Date: 2019.12.10 TEXTRON INNOVATIONS INC

AI summary

A rotary system and method to control feathering movement of a rotor blade. The system having a yoke arm configured to rotate a rotor blade. A first bearing and a second bearing are utilized to secure the rotor blade to the yoke arm and are configured to restrict longitudinal and transverse movement, while allowing feathering movement of the rotor blade relative to yoke arm.