Pneumatic Actuator Self-Cleaning via Gas Flow Deflection

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Solution Overview

Problem

Pneumatic actuators used for ejecting payloads from aircraft face issues with maintenance due to the accumulation of pyrotechnic residues, which lead to increased adhesion, friction, and the risk of galvanic corrosion, requiring frequent cleaning and affecting mechanical performance.

Innovation Solution

The actuator incorporates deflection means that direct the flow of actuation gas to press solid residues against the sliding surface, utilizing scraping projections and guide strips made of solid lubricating materials to collect and evacuate residues, reducing the need for frequent cleaning and maintaining consistent ejection performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Weight of stationary object

If pyrotechnic sources are used to generate pressurized gas, then the system weight is reduced and pressure becomes independent of external temperature, but solid combustion residues are produced that accumulate on sliding surfaces and require frequent cleaning

Engineering Contradiction:

Improvesystem weightVSAvoidmaintenance frequency

Core Design Contradiction:

Weight of stationary objectVSEase of manufacture

Solution Approach 1:

The patent converts the harmful combustion residues into a beneficial cleaning mechanism by directing the gas flow to press the residues against the sliding surface, where scraping projections and guide strips made of solid lubricating materials collect and evacuate the residues, transforming the pollution problem into a self-cleaning function

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The actuator performs self-maintenance by using its own operating gas flow to transport and evacuate combustion residues through the deflection means, scraping projections, and guide strips, eliminating the need for external cleaning operations and extending maintenance intervals

Inventive Principle:

Principle #25Self-service

2Volume of moving object

If pyrotechnic sources are used to generate pressurized gas, then the system becomes more compact, but combustion residues increase adhesion and friction between sliding surfaces

Engineering Contradiction:

Improveactuator volumeVSAvoidfriction force

Core Design Contradiction:

Volume of moving objectVSForce

Solution Approach 1:

The patent converts the harmful friction-increasing effect of combustion residues into a beneficial self-cleaning mechanism where the gas flow presses residues against scraping projections and guide strips that evacuate them, preventing adhesion and friction buildup while maintaining the compact design

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Weight of stationary object

If pyrotechnic sources are used to generate pressurized gas, then the system is lighter, but combustion residues create risk of galvanic corrosion in humid environments

Engineering Contradiction:

Improvesystem weightVSAvoidcorrosion resistance

Core Design Contradiction:

Weight of stationary objectVSReliability

Solution Approach 1:

The patent converts the corrosive combustion residues into a benign byproduct by directing the gas flow to press residues against guide strips made of solid lubricating materials that collect and evacuate them, preventing contact between residues and metal surfaces, thus eliminating galvanic corrosion risk while maintaining the lightweight design

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 enables the pneumatic actuator to maintain consistent ejection properties over time with simplified maintenance, reducing the frequency of cleaning and preventing galvanic corrosion, allowing for reliable operation over a larger number of deployments without significant degradation.

Implementation Method 1

These sources include a pyrotechnic charge capable of decomposing thermochemically to very quickly generate a large quantity of gas

Methodology Applied

Scientific EffectThermochemical decomposition: Pyrolysis

Implementation Method 2

deflection means for deflecting at least part of the flow of gas from the inlet opening towards the sliding surface to press solids present in the gas flow against the sliding surface

Methodology Applied

Scientific EffectGas flow pressure: Pressure Gradient

Implementation Method 3

the first deployable member comprises a scraping projection, of section at least partly conjugate with the inner section of the liner, the scraping projection scraping the sliding surface when the first deployable member is lowered from its deployed position to its retracted position

Methodology Applied

Scientific EffectSolid lubrication: Lubrication

Data Source

PatentEP2444677B1Pneumatic actuator for ejecting a payload carried by an aircraft and related ejection method

Publication Date: 2013.07.10 DASSAULT AVIATION SA

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AI summary

The actuator (18) has a deployable unit (26A) slidingly mounted along a sliding axis (AA') on a sliding surface (56) defined in a guiding sleeve (24) between a retracted position and an extended position. A deflecting unit (28) deflects a part of gas flow issued from an input opening (37) toward the sliding surface for plating solids in the gas flow against the sliding surface. The deflecting unit is extended from upstream of an upstream end (85A) of the deployable unit in the extended position in a partly longitudinal manner. The deployable unit comprises a guiding annular strip (86A) that is made of solid lubrication material such as PTFE loaded with carbon or metal e.g. bronze. An independent claim is also included for a method for ejecting a load carried by an aircraft.