Captive Bushing for Aircraft Tie Bar Vibration Decoupling

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Solution Overview

Problem

The existing tie rod attachments for overhead compartments in aircraft require numerous individual parts, leading to complex and time-consuming installation processes, with a high risk of parts being lost during assembly and difficult de-installation for refurbishment or repair.

Innovation Solution

The use of captive bushings with a combination of press and form fits in the fork head holes of the tie bar, reducing the number of parts and ensuring secure, reliable installation by eliminating the need for separate spacer rings and washers, and allowing for angular displacement to simplify integration into the aircraft cabin.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If numerous individual parts (spacer rings, washers, bushings) are used for tie rod attachments, then sound and vibration decoupling is achieved, but the number of parts increases leading to complex installation and high risk of losing parts

Engineering Contradiction:

Improvesound and vibration decouplingVSAvoidnumber of individual parts

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The invention combines multiple separate components (bushing, spacer ring, washer) into a single integrated bushing component. The bushing incorporates the decoupling function, positioning function, and load distribution function that were previously separated into multiple parts, thereby reducing part count while maintaining the required sound and vibration decoupling performance

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The integrated bushing performs multiple functions simultaneously: it provides sound and vibration decoupling between the overhead compartment and aircraft structure, positions the tie rod attachment point, distributes mechanical loads, and prevents direct metal-to-metal contact. This multi-functional design eliminates the need for separate spacer rings and washers

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Reliability

If numerous individual parts are used for tie rod attachments, then functional requirements are met, but installation time increases due to manual assembly in awkward locations

Engineering Contradiction:

Improveattachment functionalityVSAvoidinstallation time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

By merging the bushing, spacer ring, and washer into a single pre-assembled bushing component, the installation process is simplified from multiple separate assembly steps to a single insertion operation. The bushing is designed to be inserted as one piece into the fork head hole, significantly reducing the time required for installation in the confined aircraft cabin environment

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The bushing is pre-assembled and pre-positioned during manufacturing, so that during aircraft installation, only the final insertion into the fork head hole is required. This preliminary preparation of the attachment component eliminates the need for on-site assembly of multiple parts, reducing installation time and complexity

Inventive Principle:

Principle #10Preliminary action

3Reliability

If numerous individual parts are used for tie rod attachments, then decoupling function is achieved, but de-installation becomes more difficult for refurbishment or repair

Engineering Contradiction:

Improvesound and vibration decouplingVSAvoidde-installation difficulty

Core Design Contradiction:

ReliabilityVSEase of repair

Solution Approach 1:

The integrated bushing design allows for straightforward removal as a single component during refurbishment or repair operations. Unlike the previous multi-part system where multiple small parts needed to be disassembled and tracked, the single bushing can be removed in one piece, simplifying the de-installation process while maintaining the decoupling function during service life

Inventive Principle:

Principle #5Merging (Combining)

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 solution significantly reduces installation time, minimizes the risk of lost parts, and simplifies the installation process, enhancing safety and efficiency by forming a functional unit between the tie bar and bushings, while maintaining effective sound and vibration decoupling.

Implementation Method 1

captive bushings for purposes of sound and vibration decoupling

Methodology Applied

Scientific EffectVibration damping: Damping

Implementation Method 2

The preferably rectangular-shaped axial slots, i.e., longitudinal slots, support an inwardly directed radial deformation of the bushing as the latter is inserted into the fork head holes

Methodology Applied

Scientific EffectElastic deformation: Deformation

Data Source

PatentUS9212680B2Tie bar for purposes of connecting equipment fitting of an equipment module, in particular an overhead compartment, to a structure fitting of a fuselage cell structure of an aeronautical vehicle

Publication Date: 2015.12.15 AIRBUS OPERATIONS GMBH

AI summary

A tie bar for connecting an equipment fitting of an equipment module to a structure fitting of a fuselage cell structure. At each end the tie bar has a fork head each with a fork head hole for a bolt. The spacing between the fork heads can be continuously adjusted. A captive bushing is utilized for sound and vibration decoupling. The bushings which are a press fit in the fork head holes can no longer fall out during the handling of the tie bars 10. The dimensions of the bushings made of plastic are adapted to the respective application scenario by a tolerance calculation and guarantee an effective sound and vibration decoupling between the structure fitting and the equipment fitting.