Thermal Switch with Passive Actuator for Thermal Link
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Solution Overview
Problem
Existing thermal switches with passive actuators face challenges in maintaining high surface contact pressure and efficient thermal contact between elements, particularly in applications with variable temperature conditions, where traditional solutions like shape memory alloys and bimetallic elements are costly, difficult to integrate, and have unpredictable property changes, and bimetallic switches have high thermal resistance.
Innovation Solution
A thermal switch design featuring concentric crowns with contact pressure application means, such as compression springs and heat-sensitive materials, that maintain contact below a threshold temperature and disconnect above it, utilizing Phase Change Materials or materials with altered mechanical properties to ensure consistent and efficient thermal connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If shape memory alloys are used for thermal switch, then the thermal connection can be controlled passively, but the cost is very high and integration is difficult
Solution Approach 1:
The device segments the thermal switch function into separate components: bimetallic elements for thermal sensing and actuation, compression springs for contact pressure, and crown structures for thermal conduction. This segmentation allows each component to be optimized independently and assembled into a functional thermal switch without requiring complex shape memory alloy integration
Solution Approach 2:
The invention uses composite material structures combining bimetallic strips (for thermal response), compression springs (for elastic force), and crown geometries (for thermal conduction). This composite approach replaces the single-material shape memory alloy solution with a multi-material system that achieves passive thermal switching with easier manufacturing and integration
2Ease of manufacture
If bimetallic elements are used for thermal switch, then the structure is simple and cost-effective, but the thermal resistance is high
Solution Approach 1:
The invention employs crown-shaped (curved) contact surfaces instead of flat bimetallic element surfaces. The crown geometry increases the contact surface area between thermal elements, reducing contact resistance while maintaining the simple bimetallic structure. The curved surface ensures better conformal contact and distributes contact pressure more evenly
Solution Approach 2:
Compression springs are pre-loaded to apply contact pressure before thermal actuation occurs. This preliminary mechanical force ensures optimal thermal contact is established in advance, compensating for any gaps or irregularities in the bimetallic element surfaces, thereby reducing thermal resistance while keeping the structure simple
3Measurement precision
If active actuator thermal switch is used, then the thermal link can be controlled precisely, but the device complexity increases due to motor, sensor and energy supply
Solution Approach 1:
The thermal switch uses bimetallic elements that automatically respond to temperature changes through inherent thermal expansion differences, eliminating the need for external sensors, motors, or control systems. The compression springs self-adjust contact pressure based on thermal actuation, providing precise thermal control through passive self-regulating mechanisms without additional components
Solution Approach 2:
The invention exploits thermal expansion principles through bimetallic elements that bend or deform in response to temperature changes. This thermal-driven mechanical actuation provides precise control of the thermal link status (open/closed) based on temperature thresholds, replacing complex active control systems with a simple thermal-responsive mechanism
4Reliability
If high contact pressure is applied to ensure good thermal contact, then the thermal resistance decreases, but the means to apply pressure becomes complex
Solution Approach 1:
The invention uses simple compression springs as disposable-like components that provide consistent contact pressure throughout their elastic range. These inexpensive springs replace complex active pressure control systems, maintaining reliable thermal contact through passive elastic force without requiring sensors, actuators, or control electronics
Solution Approach 2:
The compression springs utilize changes in their elastic parameters (force-displacement characteristics) to maintain optimal contact pressure. As the thermal elements expand or contract, the springs automatically adjust their compression level, providing consistent contact pressure that ensures low thermal resistance without complex pressure regulation mechanisms
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 provides a simple, effective, and robust method for establishing and interrupting thermal connections with high surface contact pressure, reducing thermal resistance and maintaining efficient thermal paths without the need for energy or complex measurement systems, suitable for reversible or irreversible operation.
Implementation Method 1
one or more means for applying contact pressure, the means being activated when they are below a threshold temperature, to maintain the first and second crowns in contact
Implementation Method 2
at least one part made of heat-sensitive material whose mechanical properties are modified above the threshold temperature
Implementation Method 3
at least one part made of heat-sensitive material whose mechanical properties are modified above the threshold temperature
Implementation Method 4
establishing or interrupting a thermal connection between two elements
Data Source
Figure 1~2B
Figure 3A~4A
Figure 4B~5B
AI summary
The invention relates to a thermal switch, which can be configured reversible or irreversible, consisting of two concentric rings each attached to an element (cold source or heat source), in surface contact (plane-to-plane support), preferably along a continuous annular area, by means of contact pressure, in order to establish the thermal link between the two elements, this thermal link being interrupted by the thermal deactivation above a threshold temperature of the mechanical means of applying the pressure.