Segmented Ferrule Coupling to Prevent Duct Cracking

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Solution Overview

Problem

Current ferrule couplings for joining inner and outer ducts are susceptible to cracking and separation due to temperature changes and stress, and require welding, which makes them prone to rework and reduces their service life.

Innovation Solution

A multi-piece ferrule coupling system using an inner ferrule, an intermediate ferrule, and an outer ferrule, where the ferrules are mechanically joined without welding, forming an electrostatic bond path that is resistant to temperature-based stresses and maintains reliability over time.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If welding is used to join ferrules together, then the coupling strength is improved, but the reliability deteriorates due to susceptibility to cracking and separation from temperature changes and stress

Engineering Contradiction:

Improvecoupling strengthVSAvoidresistance to cracking and separation

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The patent replaces the welding (thermal/chemical joining) system with a mechanical joining system using engagement sections. The ferrules are joined through mechanical interlocking features such as threads, ridges, or interlocking geometries that physically engage without heat application, thereby eliminating thermal stress and cracking while maintaining coupling strength.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent divides the ferrule coupling into multiple discrete engagement sections rather than a continuous welded joint. These segmented engagement sections can independently accommodate stress and thermal expansion, preventing the propagation of cracks that would occur in a continuous welded structure.

Inventive Principle:

Principle #1Segmentation

2Reliability

If welding is used to join ferrules, then permanent joining is achieved, but the ease of repair deteriorates due to inability to disassemble components

Engineering Contradiction:

Improvepermanent joiningVSAvoiddisassembly capability

Core Design Contradiction:

ReliabilityVSEase of repair

Solution Approach 1:

The patent employs dynamic mechanical engagement sections that can be assembled and disassembled through controlled mechanical actions. The engagement sections allow for reversible joining, enabling components to be separated and reassembled as needed, thus providing both permanent joining during operation and ease of repair when required.

Inventive Principle:

Principle #15Dynamics

3Ease of manufacture

If welding is used to join ferrules, then the manufacturing process is simplified, but the manufacturing precision deteriorates due to heat-affected zones and distortion

Engineering Contradiction:

Improvejoining process simplicityVSAvoiddimensional accuracy after joining

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent substitutes mechanical engagement sections for welding, eliminating heat-affected zones and thermal distortion. The mechanical joining process allows for precise control of engagement geometry and positioning, maintaining high manufacturing precision while keeping the manufacturing process simple and free from thermal management requirements.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS11287067B2Ferrule coupling for joining ducts together

Publication Date: 2022.03.29 THE BOEING CO

AI summary

An apparatus comprising an inner ferrule and an outer ferrule. The inner ferrule comprises a plurality of engagement sections that define a plurality of gaps between the plurality of engagement sections. The outer ferrule is disposed around at least a portion of the inner ferrule. The outer ferrule comprises an engagement area mechanically joined to the plurality of engagement sections to join the inner ferrule to the outer ferrule.