Thruster Skirt Casing Connection via Elastomer Injection

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Solution Overview

Problem

Achieving a reliable and defect-free assembly between the casing and skirts of a thruster body, particularly for large diameter thrusters with inevitable shape irregularities, is challenging due to the difficulty in aligning and securing the skirts effectively.

Innovation Solution

A method involving positioning a prefabricated skirt around the thruster body's end wall, creating an annular space, injecting elastomer into this space to compensate for irregularities, and curing it, which allows for precise alignment and secure attachment without creases or over-winding, using tooling for injection and potential vacuum assistance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a prefabricated elastomer spacer is used to connect the skirt to the casing, then the assembly process is simplified, but the irregularities of shape in the casing or skirt cannot be compensated, resulting in poor assembly quality

Engineering Contradiction:

Improveassembly processVSAvoidassembly quality

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The skirt is positioned and secured in place before the elastomer injection process begins. The terminal portion of the skirt is positioned with circumferential clearance around the casing, and tooling is used to secure the skirt in the desired position, ensuring proper alignment before the elastomer is injected to fill and compensate for shape irregularities.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

Elastomer is injected into the annular space between the skirt and casing to act as a flexible intermediary material. This elastomer filler compensates for shape irregularities in both the casing and skirt, providing a reliable connection while accommodating dimensional variations that would otherwise compromise assembly quality.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Loss of time

If the skirt is made separately from the casing, then the manufacturing time for the casing installation is reduced, but achieving good assembly between the casing and skirts becomes more difficult

Engineering Contradiction:

Improvecasing installation timeVSAvoidassembly alignment

Core Design Contradiction:

Loss of timeVSManufacturing precision

Solution Approach 1:

The skirt is pre-formed and prepared as a separate component before assembly. The terminal portion of the skirt is positioned with circumferential clearance around the casing, and tooling is used to secure the skirt in the desired position, ensuring proper alignment before the elastomer is injected to fill and compensate for shape irregularities.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

Inventive Principle:

Principle #24Intermediary (Mediator)

3Manufacturing precision

If draping preimpregnated plies on the wound casing is used to make the skirt in situ, then the skirt can be formed to fit the casing, but the skirt develops creases or other defects from sticking to prefabricated elastomer spacer or tooling

Engineering Contradiction:

Improveskirt fitVSAvoidskirt defect-free quality

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The skirt is divided into a terminal portion that is separately fabricated and positioned, and a free portion that surrounds the end wall. This segmentation allows the terminal portion to be pre-formed without defects, then securely attached to the casing using the elastomer injection method, eliminating the creases and defects associated with draping the entire skirt in situ.

Inventive Principle:

Principle #1Segmentation

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 method ensures a high-quality, centered assembly that compensates for shape irregularities, reduces assembly time, and eliminates defects, providing a strong and reliable connection between the skirt and casing, even in the presence of geometrical defects.

Implementation Method 1

injecting elastomer into said annular space; and curing the elastomer

Methodology Applied

Scientific EffectElasticity: Elasticity

Implementation Method 2

depositing adhesive on facing faces of the terminal portion of the skirt and of the casing of the thruster body, prior to injecting the elastomer

Methodology Applied

Scientific EffectAdhesion: Adhesive

Implementation Method 3

When a rise in temperature is necessary or desirable for curing the elastomer, this may be obtained by means of a heater element arranged on the outside of the terminal portion of the skirt

Methodology Applied

Scientific EffectHeating: Heating

Implementation Method 4

The elastomer may be injected through tooling closing an end of said annular space and/or through the terminal portion of the skirt

Methodology Applied

Scientific EffectVacuum: Vacuum

Data Source

PatentUS10576671B2Method of connecting a skirt to a thruster body casing

Publication Date: 2020.03.03 ARIANEGRP SAS

AI summary

The terminal portion of a prefabricated skirt is connected to a casing of a thruster body in the vicinity of an end wall thereof using a method including positioning the terminal portion of the skirt with circumferential clearance around the casing of the thruster body in the vicinity of the end wall; keeping the skirt in position relative to the casing of the thruster body; closing both ends of an annular space between the terminal portion of the skirt and the casing of the thruster body; injecting elastomer into the annular space; and curing the elastomer.