Ruggedized Detector Cooler Assembly for Expander Vibration Control
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Solution Overview
Problem
Conventional Stirling engine-based infrared camera systems are vulnerable to damaging vibrations in field applications, leading to potential damage of the expander and loss of vacuum, as well as stress on electrical wires connecting the IR sensor to the CPU.
Innovation Solution
A ruggedized integrated detector cooler assembly is designed with a support tube that increases the stiffness and natural frequency of the expander, and includes additional electrical pathways and shock absorbers to mitigate the effects of vibrations, while minimizing heat transfer and allowing for differential thermal expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the expander is made more rigid to withstand vibrations, then the reliability under shock loads improves, but the ability to accommodate differential thermal expansion deteriorates
Solution Approach 1:
The patent employs a flexible membrane or diaphragm at the cold finger to provide structural flexibility that accommodates differential thermal expansion between the warm and cold ends, while the overall expander structure maintains sufficient rigidity to withstand vibration and shock loads. This flexible element allows controlled deformation without compromising the integrity of critical components.
Solution Approach 2:
The patent incorporates features specifically designed to handle thermal expansion, such as expansion joints, flexible connections, or compliant mounting structures at the cold finger. These features allow the cold end to expand and contract independently from the warm end during temperature cycling, preventing stress buildup that would compromise vibration resistance.
2Reliability
If the support tube increases the stiffness of the expander, then the natural frequency increases and vibration resistance improves, but the device complexity increases
Solution Approach 1:
The support tube serves multiple functions simultaneously: it provides structural support to increase stiffness and natural frequency, acts as a thermal barrier between the warm and cold ends, and serves as a mounting structure for the expander. By consolidating these functions into a single component, the patent avoids adding excessive complexity while achieving the desired vibration resistance.
Solution Approach 2:
The support tube is positioned concentrically around the cold finger, creating a nested structure where the support tube encloses the cold finger. This nested arrangement maximizes the stiffness enhancement while minimizing the increase in overall device volume and structural complexity. The support tube essentially reinforces the existing cold finger structure without requiring separate mounting brackets or additional support elements.
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
The solution effectively reduces the impact of vibrations on the expander and electrical wires, enhancing the system's ability to withstand field conditions and maintain operational integrity by increasing the natural frequency of the expander and reducing stress on electrical connections.
Implementation Method 1
The support member provides additional stiffness to the expander to reduce movements at the distal end of the expander. The support member also increases the natural frequency of the expander.
Implementation Method 2
The compressor, also known as a pressure wave generator, is attached to the warm end of the expander and delivers acoustic power (compressor PV work) into the expander warm end inlet.
Implementation Method 3
The expander recovers this work at the cold end by causing the gas to expand and thus absorb heat from external power source such as an IR sensor.
Implementation Method 4
heat is absorbed from the load and very low temperatures are achieved due to efficient thermal isolation between the warm and cold end of the expander unit.
Implementation Method 5
Furthermore, shock absorber and/or shock diverters are provided on the rigid pins that connect the electrical wires to the CPU.
Data Source
AI summary
Provided for an embodiment is a support member for a cryogenic cooler's expander. The support member provides stiffness to the expander to reduce movements at the expander's distal end and may increase the natural frequency of the expander. The support member may increase the natural frequency of the expander at least about two times in the bending and/or twisting sense. The bending natural frequency of the expander and support sub-assembly may be at least about two times greater or lower than the natural frequency of the electrical wires that connect an infrared sensor to a control processing unit to reduce the maximum stress applied to the electrical wires during use. In another embodiment, additional or redundant electrical pathways are provided for connections between the infrared sensor and the CPU. Furthermore, shock absorber and/or shock diverters are provided on rigid pins that connect the electrical wires to the CPU.