Thermal Expansion Interference Fit for Optical Fiber Mounting

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing optical probe mounting structures in gas turbine engines fail to withstand extreme temperatures due to the susceptibility of epoxy adhesives, leading to potential failure and the need for a reliable high-temperature compatible mounting solution.

Innovation Solution

A probe assembly design featuring holders with different coefficients of thermal expansion, where an inner holder with a higher expansion rate is used to create an interference fit with the optical fiber, eliminating the need for epoxy by using thermal expansion differences to secure the sensor member within an outer holder, and optionally a lens within a lens housing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If epoxy is used to adhere optical fibers to probe housings, then the optical fiber can be mounted in the probe, but the epoxy is susceptible to failure due to exposure to extreme temperatures

Engineering Contradiction:

Improveoptical fiber mounting reliabilityVSAvoidextreme temperature exposure

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The patent removes the epoxy adhesive from the mounting system entirely. Instead of using chemical bonding, the invention employs a mechanical interference fit between the holder and optical fiber, where the holder's bore is sized to create friction-based retention without any temperature-sensitive adhesives.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent changes the bonding mechanism from chemical (epoxy) to mechanical (interference fit). The holder is designed with a specific bore diameter that creates radial interference with the optical fiber, generating friction forces sufficient to retain the fiber under thermal expansion and contraction without relying on adhesive properties.

Inventive Principle:

Principle #35Parameter changes

2Device complexity

If a simple single-holder structure is used, then the device complexity is reduced, but the ability to retain optical components under extreme thermal stress is compromised

Engineering Contradiction:

Improveholder structure complexityVSAvoidoptical fiber retention under thermal stress

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent divides the holder into two distinct components: an outer holder that provides structural support and mounting features, and an inner holder that directly interfaces with the optical fiber. This segmentation allows each component to be optimized for its specific function while working together to provide reliable retention under thermal stress.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The inner holder is positioned within the outer holder, creating a nested configuration. The inner holder's outer surface fits within the outer holder's inner bore, and this nested arrangement allows the differential thermal expansion between the two holders to be managed while maintaining secure optical fiber retention.

Inventive Principle:

Principle #7Nested doll (Nesting)

3Ease of manufacture

If holders with the same coefficient of thermal expansion are used, then manufacturing is simplified, but the interference fit cannot maintain proper orientation under temperature changes

Engineering Contradiction:

Improveholder manufacturingVSAvoidoptical fiber orientation precision

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent exploits differential thermal expansion between the inner and outer holders. The inner holder is made of a material with a higher coefficient of thermal expansion than the outer holder. During temperature changes, this differential expansion creates or maintains the interference fit between the inner holder and optical fiber, ensuring consistent orientation and position despite thermal cycling.

Inventive Principle:

Principle #37Thermal expansion

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 design ensures secure mounting of optical components without adhesives, maintaining orientation and stability under extreme temperatures, thereby enhancing the reliability and durability of optical probes in high-temperature environments.

Implementation Method 1

The inner holder includes a coefficient of thermal expansion greater than the outer holder

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS9952066B2Thermally constrained high temperature optical fiber holder

Publication Date: 2018.04.24 RTX CORP

AI summary

A disclosed probe assembly includes a sensor member and an outer holder including a main bore for the sensor member, the outer holder including a first coefficient of thermal expansion. The sensor member is held within a sensor bore of an inner holder. The inner holder is held within the main bore of the outer holder by an interference fit. The inner holder includes a second coefficient of thermal expansion greater than the first coefficient of thermal expansion. Expansion of the inner holder is constrained by the outer holder to maintain the sensor member within the probe bore of the inner holder at elevated temperatures.