Infrared Sensor Case Using Titanium Alloy and Laser Welding

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Solution Overview

Problem

Existing electromagnetic radiation detection devices for self-guided projectiles require improved sealing and structural rigidity to maintain vacuum and operate effectively across significant temperature variations, with current materials like Kovar being unsuitable due to increased complexity and corrosion sensitivity.

Innovation Solution

The use of a titanium alloy for the case and cold finger, combined with laser welding and glass-lined sealed passages, allows for better positioning and assembly of the FPA, reduced weight, and improved corrosion resistance, enabling precise and stable operation in non-sealed environments.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If metal alloys like Kovar are used for the case, then structural rigidity and sealing are improved, but weight increases and corrosion resistance deteriorates

Engineering Contradiction:
Improvestructural rigidityVSAvoidweight
Core Design Contradiction:
StrengthVSWeight of moving object

Solution Approach 1:

The patent changes the material parameter from traditional Kovar alloy to titanium alloy, which fundamentally alters the weight-to-strength ratio. Titanium provides sufficient structural rigidity while reducing weight by approximately 30% compared to Kovar, directly resolving the contradiction between strength and weight.

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The patent employs composite construction by combining titanium alloy for the case structure with glass-lined sealed passages for electrical connectors. This composite approach maintains structural integrity while enabling effective sealing, addressing both the strength requirement and the corrosion resistance need.

Inventive Principle:
Principle #40Composite materials

2Adaptability or versatility

If multiple connections are added to the sensor, then functionality is improved, but device complexity and sealing difficulty increase

Engineering Contradiction:
ImprovefunctionalityVSAvoidsealing complexity
Core Design Contradiction:
Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent introduces glass-lined sealed passages as an intermediary structure to manage multiple electrical connector connections. These passages act as mediators that provide both electrical connectivity and hermetic sealing in a unified structure, reducing the complexity of managing multiple separate sealing points while maintaining full functionality.

Inventive Principle:
Principle #24Intermediary (Mediator)

3Strength

If the case material is changed from glass to metal, then structural rigidity is improved, but manufacturing precision and sealing quality deteriorate

Engineering Contradiction:
Improvestructural rigidityVSAvoidsealing quality
Core Design Contradiction:
StrengthVSManufacturing precision

Solution Approach 1:

The patent replaces traditional mechanical sealing methods with laser welding technology to join titanium components. This substitution of mechanical sealing processes with laser welding provides superior sealing quality and precision while maintaining the structural advantages of metal construction, effectively resolving the manufacturing precision issue.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

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 enhances the optronic performance, simplifies manufacturing, reduces weight by 30%, and ensures long-term resistance and tightness, while adapting to non-sealed environments with titanium's corrosion resistance.

Implementation Method 1

the assembly of the case and the cold finger can be done by simple laser welding

Methodology Applied
Scientific EffectLaser welding: Laser Beam Welding

Implementation Method 2

The sealed passages in the main body are lined with glass sealed to the main body

Methodology Applied
Scientific EffectGlass sealing: Soldering

Implementation Method 3

a hollow casing (6) defining an enclosure (7) in which there is a partial vacuum

Methodology Applied
Scientific EffectVacuum: Vacuum

Implementation Method 4

a sensor (4) mounted on the terminal wall (16) of the dewar container (14)... The radiation detected is generally infrared

Methodology Applied
Scientific EffectInfrared radiation detection: Absorption (EM radiation)

Data Source

PatentEP1715314B1Apparatus for detecting infrared radiation, guidance system equipped with said apparatus, and self-guided projectile equipped with said guidance system
Publication Date: 2011.09.28 SAFRAN ELECTRONICS & DEFENSE SAS
  • EP1715314B1 patent drawingFigure 1
  • EP1715314B1 patent drawingFigure 2~3
  • EP1715314B1 patent drawingFigure 4~5

AI summary

The apparatus has a case (6) defining a hollow enclosure (7), and a cold plunger (12) that is fixed tightly to the case. The cold plunger has a Dewar container (14) extending in the hollow enclosure and terminated by a terminal wall (16) on which an infrared sensor (4) is mounted. The case is formed by assembling a main body (24), a flange (29) and a cover (34) by laser welding.