Inboard Pivot Axis for Compact Rotor Blade Folding

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Solution Overview

Problem

Current rotor blade folding systems for rotorcraft and tiltrotor aircraft cannot accommodate reduced storage space requirements, necessitating a tighter grouping of rotor blades that is not feasible with existing systems.

Innovation Solution

A folding rotor blade assembly design that includes a yoke connected to a hub spring assembly, inboard and outboard bearing assemblies, and a pivotal connection of the rotor blade to the grip positioned inboard of the outboard centrifugal force bearing, allowing for a more compact folding configuration by rotating the rotor blade about a pivot axis inboard of the outboard bearing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If the pivot point is positioned outboard of the bearings to allow rotor blade folding, then the rotor blade can be folded for reduced storage space, but the distance between the inboard and outboard bearings must be increased to preserve optimal bearing distances, which increases the overall profile and reduces storage density

Engineering Contradiction:

Improvestorage spaceVSAvoiddistance between bearings

Core Design Contradiction:

Volume of moving objectVSLength of stationary object

Solution Approach 1:

The patent inverts the conventional arrangement by positioning the pivot point inboard of the outboard bearing instead of outboard. This reversal allows the pivot axis to be located between the inboard and outboard bearings, enabling tighter blade grouping during storage while maintaining optimal bearing distances for structural integrity and load distribution.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent repositions the pivot axis from a location outside the bearing assembly to a location between the bearings, effectively changing the spatial dimension of the folding mechanism. This dimensional reconfiguration allows the rotor blade to fold closer to the hub without compromising the optimal distance between inboard and outboard bearings, thereby reducing the overall profile and increasing storage density.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Quantity of substance

If the pivot point is positioned closer to the hub to achieve tighter blade grouping, then storage density increases, but the optimal distance between inboard and outboard bearings is compromised, affecting structural integrity

Engineering Contradiction:

Improvenumber of aircraft storedVSAvoiddistance between bearings

Core Design Contradiction:

Quantity of substanceVSLength of stationary object

Solution Approach 1:

By inverting the conventional pivot point location from outboard to inboard relative to the outboard bearing, the patent enables tighter blade grouping that increases the number of aircraft that can be stored, while simultaneously preserving the optimal distance between inboard and outboard bearings through the new pivot axis positioning between the bearings.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent applies the bearing distance configuration from conventional designs to the new inboard pivot configuration, copying the optimal inboard-to-outboard bearing spacing to ensure structural integrity is maintained even as the pivot point location changes to enable tighter storage.

Inventive Principle:

Principle #26Copying

3Device complexity

If the pivot point is positioned outboard of the bearings in conventional designs, then the rotor blade folding mechanism is simple, but the overall profile is larger, reducing the number of aircraft that can be accommodated in limited storage space

Engineering Contradiction:

Improvefolding mechanismVSAvoidoverall profile

Core Design Contradiction:

Device complexityVSVolume of moving object

Solution Approach 1:

The patent inverts the pivot point position from outboard to inboard of the outboard bearing, which maintains the simplicity of the folding mechanism while significantly reducing the overall profile. This inversion allows the rotor blade to fold closer to the hub, decreasing the volume occupied and increasing the number of aircraft that can be stored.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

By changing the dimensional location of the pivot axis to between the inboard and outboard bearings, the patent achieves a more compact overall profile without complicating the folding mechanism. This dimensional shift enables tighter blade grouping while preserving the straightforward mechanical folding action.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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

Enables a more compact folding of rotor blades, allowing for increased storage density of aircraft in limited spaces without interfering with the optimal bearing distances, facilitating efficient storage and transport of multiple rotorcraft.

Implementation Method 1

an outboard bearing assembly, including an outboard centrifugal force ("CF") bearing, connected to the yoke

Methodology Applied

Scientific EffectCentrifugal force: Centrifugal Force

Data Source

PatentUS10640205B2Outboard centrifugal force bearing with inboard blade fold axis in a folding rotor blade assembly

Publication Date: 2020.05.05 TEXTRON INNOVATIONS INC

AI summary

A rotor blade assembly for a tiltrotor aircraft comprising a rotor blade pivotally connected to a yoke with dual concentric blade bolts having a common central axis providing a pivotal axis inboard of an outboard CF bearing and the yoke tip. In use, the compact folded arrangement of the rotor blades reduces folded aircraft dimensions in response to ever increasing restricted storage space parameters.