Shock Strut Latch Linkage for Over-Center Anti-Jamming

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Solution Overview

Problem

Existing latch assemblies for shock struts in aircraft landing gear can jam, preventing the strut from extending properly, especially when the landing gear transitions from the up to the down position, leading to safety issues and operational inefficiencies.

Innovation Solution

A latch assembly comprising a first linkage with a tang and a second linkage in the form of a clevis, which rotates to translate the tang between over-center and under-center positions, preventing the strut from unshrinking when in the wheel well and allowing it to extend when outside, thereby preventing jamming and ensuring smooth operation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a safety latch is used to prevent the strut from unshrinking in the wheel well, then the safety of the landing gear is improved, but the latch may jam and prevent the strut from extending properly when the gear is down

Engineering Contradiction:

Improvesafety of landing gearVSAvoidsmooth extension of strut

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The latch assembly uses dynamic linkage geometry that changes with strut position. The clevis rotates about a pivot point, and the tang moves between over-center and under-center positions depending on whether the gear is up or down, allowing the latch to be engaged during retraction but disengaged during extension

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The latch assembly is divided into separate functional components: the clevis (second linkage) that rotates independently, the tang (part of first linkage) that translates between positions, and the pivot joints that allow relative motion. This segmentation allows each component to perform its specific function without interfering with others

Inventive Principle:

Principle #1Segmentation

2Device complexity

If the latch assembly uses a simple linkage mechanism, then the device complexity is reduced, but the mechanism may inadvertently hold the strut in the shrunk position

Engineering Contradiction:

Improvesimplicity of latch mechanismVSAvoidprevention of inadvertent latching

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The over-center/under-center positioning creates a dynamic system where the latch state changes automatically with strut position. When the gear is down, the tang moves to the under-center position where the clevis cannot block extension, preventing inadvertent latching while maintaining simplicity

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The linkage geometry is designed so that the clevis and tang positions are predetermined to prevent latching in the extended position. The outboard and inboard lugs are positioned to limit tang translation only when needed, creating a built-in anti-latching mechanism

Inventive Principle:

Principle #9Preliminary anti-action

Data Source

PatentUS10974819B2Latch assembly for shock strut

Publication Date: 2021.04.13 GOODRICH CORP

AI summary

A latch assembly for a shock strut may comprise a first linkage coupled to a strut cylinder and a shrink piston of the shock strut. A second linkage may be coupled to the strut cylinder. The second linkage may be configured to rotate the first linkage in response to the shock strut translating between a landing gear up position and a landing gear down position.