Screw Jack Thrust Reverser Actuator Buckling

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Solution Overview

Problem

Conventional thrust reverser jacks for aircraft propulsion units are prone to buckling due to mechanical stresses, which increases the risk of failure and requires additional reinforcement, thereby increasing mass and manufacturing costs.

Innovation Solution

The thrust reverser system incorporates an actuator with a screw and nut configuration where the distance between the connecting elements is minimized when the actuator is in its initial position, reducing the risk of buckling and eliminating the need for an extension tube, thus reducing mass and manufacturing costs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Length of moving object

If the distance between the nut and the connecting end of the screw is increased to accommodate the stroke of the actuator, then the actuator can achieve the required displacement, but the screw becomes susceptible to mechanical stresses and buckling

Engineering Contradiction:

Improvedistance between connecting elementsVSAvoidrisk of buckling

Core Design Contradiction:

Length of moving objectVSReliability

Solution Approach 1:

Instead of connecting the screw to the fixed portion and the nut to the movable portion (conventional arrangement), the invention inverts this by connecting the screw to the movable portion and the nut to the fixed portion. This inversion allows the screw to be shorter and more stable while still achieving the required stroke through the cooperative displacement mechanism between the screw and nut

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The invention changes the parameter of distance between connecting elements by positioning it such that the distance is less than the stroke of the actuator. This parameter optimization reduces the screw length and eliminates buckling risk while maintaining full actuator functionality through the screw-nut cooperative mechanism

Inventive Principle:

Principle #35Parameter changes

2Strength

If an extension tube is added to house the screw and provide structural support, then the mechanical stability is improved, but the mass and manufacturing cost of the thrust reverser increase

Engineering Contradiction:

Improvemechanical stabilityVSAvoidmass of thrust reverser

Core Design Contradiction:

StrengthVSWeight of moving object

Solution Approach 1:

The invention extracts and eliminates the extension tube from the actuator assembly. By optimizing the connection arrangement between the screw and nut, the patent achieves mechanical stability without requiring the additional structural support of an extension tube, thereby reducing mass and manufacturing complexity

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The inverted connection arrangement (screw to movable portion, nut to fixed portion) inherently provides the necessary structural support and stability, making the extension tube redundant. This inversion allows the system to achieve strength requirements through the optimized mechanical arrangement rather than additional structural components

Inventive Principle:

Principle #13The other way round (Inversion)

3Ease of operation

If conventional mechanical jacks with long screws are used to achieve the required stroke, then the actuator can displace the movable portion between direct thrust and thrust reversal positions, but the screw is subjected to high mechanical stresses

Engineering Contradiction:

Improvedisplacement capabilityVSAvoidmechanical stress on screw

Core Design Contradiction:

Ease of operationVSStress or pressure

Solution Approach 1:

By inverting the conventional connection arrangement, the invention allows the screw to remain shorter and more stable while the nut travels the full stroke distance. The screw still achieves the required displacement capability through its cooperative mechanism with the nut, but experiences significantly reduced mechanical stress due to its shorter, more stable configuration

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The nut acts as an intermediary that transfers the rotational motion of the screw into linear displacement over the full stroke distance. This allows the screw to maintain a short, stable configuration while still achieving the required displacement through the mediating action of the nut-screw helical connection

Inventive Principle:

Principle #24Intermediary (Mediator)

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 configuration significantly reduces the risk of buckling and allows for a more compact and lightweight actuator, enhancing the aerodynamic performance of the propulsion unit while lowering manufacturing costs.

Implementation Method 1

A mechanical thrust reverser jack typically comprises a screw and a nut which cooperate with each other via balls so as to form a helical connection. A rotation of the screw relative to the nut thus causes a translation of the screw relative to the nut, and vice versa.

Methodology Applied

Scientific EffectHelical connection: Screw

Data Source

PatentUS12331699B2Actuating system for a cascade thrust reverser

Publication Date: 2025.06.17 SAFRAN NACELLES

AI summary

A thrust reverser includes a jack for translational actuation of a movable part, the jack being a screw jack without an extension tube.