Feedthrough Sleeve with Graded Thermal Conductivity for Sealing Control

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Solution Overview

Problem

Existing feedthroughs for submarine cables suffer from reliability issues such as pressure resistance, water tightness, and airtightness due to insufficient or uneven filling of sealing material, leading to increased optical loss and microbend occurrence in optical fibers.

Innovation Solution

The feedthrough design incorporates a sleeve with a lower thermal conductivity in the lower portion compared to the upper portion, which helps in controlling the solidification of the sealing material and preventing it from flowing downward excessively, ensuring a uniform and sufficient filling in the sealing groove.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If water cooling is applied to the sleeve upper portion to solidify sealing material from bottom to top, then sealing material solidification is controlled, but molten sealing material flows downward excessively causing insufficient filling

Engineering Contradiction:

Improvesealing material filling uniformityVSAvoidfeedthrough pressure resistance and water tightness

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The sleeve is designed with different thermal conductivities in different regions: the upper portion has higher thermal conductivity to facilitate controlled cooling and solidification of sealing material, while the lower portion has lower thermal conductivity to prevent excessive downward flow of molten sealing material. This local differentiation of thermal properties resolves the contradiction between achieving uniform filling and preventing material loss.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The thermal conductivity parameter of the sleeve is changed along its length, creating a gradient structure. By adjusting the thermal conductivity distribution (higher at top, lower at bottom), the patent controls the temperature field and molten sealing material behavior, ensuring proper solidification without excessive flow.

Inventive Principle:

Principle #35Parameter changes

2Quantity of substance

If heating temperature or heating time is increased to ensure sealing material melting, then complete melting is achieved, but molten sealing material flows downward more than necessary

Engineering Contradiction:

Improvesealing material melting completenessVSAvoidsealing material filling amount

Core Design Contradiction:

Quantity of substanceVSManufacturing precision

Solution Approach 1:

The sleeve structure implements local quality differentiation with the lower portion having reduced thermal conductivity. This prevents excessive heat transmission to the lower region, confining the molten sealing material within the sealing groove even when higher heating temperatures or longer heating times are applied to ensure complete melting.

Inventive Principle:

Principle #3Local quality

3Ease of manufacture

If uniform thermal conductivity is maintained throughout the sleeve, then manufacturing is simplified, but molten sealing material flows downward causing voids and insufficient filling

Engineering Contradiction:

Improvesleeve manufacturing simplicityVSAvoidsealing quality and optical fiber protection

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent deliberately introduces non-uniform thermal conductivity in the sleeve structure, with the lower portion having lower thermal conductivity than the upper portion. This design choice prioritizes sealing quality and reliability over manufacturing simplicity, as the differentiated structure is necessary to control molten sealing material behavior and prevent void formation.

Inventive Principle:

Principle #3Local quality

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 configuration enhances the reliability of the feedthrough by maintaining pressure resistance, water tightness, and airtightness while reducing optical loss and microbend occurrence in the optical fibers, thus improving the overall performance of the submarine repeater.

Implementation Method 1

the solder filled in the solder sealing portion is melted by a heating means (heating coil)

Methodology Applied

Scientific EffectMelting: Melting

Implementation Method 2

the molten sealing material (solder) is solidified from the sealing bottom side of the solder sealing portion beings a sealing groove to the sealing upper side of the solder sealing portion sequentially

Methodology Applied

Scientific EffectSolidification: Freezing

Implementation Method 3

In the sleeve, a thermal conductivity of the sleeve lower portion is lower than a thermal conductivity of the sleeve upper portion

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Data Source

PatentUS20250147262A1Feedthrough and method for manufacturing feedthrough

Publication Date: 2025.05.08 NEC CORP

AI summary

To provide a feedthrough and a method for manufacturing the feedthrough that make it possible to achieve high reliability and reduce optical loss of an optical fiber. The feedthrough includes: a sleeve including an upper sleeve portion, a sleeve central portion, and a sleeve lower portion; a guide fitted to at least an inner peripheral surface of the sleeve central portion; an optical fiber inserted through a through hole formed in the sleeve; and a sealing material being formed between the sleeve upper portion and the guide and hermetically sealing a part of the optical fiber to a sealing groove communicating with the through hole. In the sleeve, a thermal conductivity of the sleeve lower portion is lower than a thermal conductivity of the sleeve upper portion.