Shape-Memory Dead-Facing Switches for Resettable Cable Disconnection
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Solution Overview
Problem
Existing pyrotechnically-activated dead-facing mechanisms for severing electrical connections are complex, require special handling, cannot be tested or reset, and can cause debris and short-circuits, making them unsuitable for applications like flight vehicles where safe and reliable disconnection of umbilical cables is necessary.
Innovation Solution
Shape-memory-based dead-facing mechanisms using a shape-memory actuator to reposition a movable electrical contact and a shutter member to physically separate stationary contacts, allowing for quick and safe severing of electrical connections without explosive residues or debris, and enabling easy reset and testing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If pyrotechnically-activated dead-facing mechanisms are used to sever electrical connections, then the electrical connections can be severed quickly, but the mechanisms become complex and require special handling
Solution Approach 1:
The patent replaces the pyrotechnic system with a shape memory alloy (SMA) actuator system. The SMA actuator uses thermal-mechanical properties to drive the dead-facing mechanism, eliminating the need for complex pyrotechnic components while maintaining the ability to quickly sever electrical connections. The SMA element transforms thermal energy into mechanical motion to actuate the contacts.
Solution Approach 2:
The patent utilizes the temperature-dependent shape memory effect of SMA materials. By changing the temperature parameter (through resistive heating or external heat sources), the SMA actuator transitions between different shapes, thereby controlling the opening and closing of electrical contacts. This parameter-based control simplifies the mechanism compared to pyrotechnic systems.
2Reliability
If pyrotechnically-activated dead-facing mechanisms are used, then electrical connections can be severed, but the mechanisms cannot be tested or reset and produce debris and short-circuits
Solution Approach 1:
The patent enables recovery and resetting of the dead-facing mechanism. After the SMA actuator has driven the contacts apart to sever the electrical connection, the system can be reset by cooling the SMA element (allowing it to return to its original shape) and manually or automatically repositioning the contacts. This eliminates the single-use nature of pyrotechnic mechanisms.
Solution Approach 2:
The SMA actuator provides self-contained actuation without requiring external pyrotechnic triggers. The mechanism can be controlled through electrical heating of the SMA element, integrated control systems, or other actuation methods, making it easier to test and integrate into existing systems.
3Productivity
If pyrotechnic charges are used in dead-facing mechanisms, then cable severing can be achieved, but special triggering circuitry and safety circuitry are required
Solution Approach 1:
The patent replaces the pyrotechnic charging system with an SMA actuator system that can be controlled through simple electrical heating or integrated control signals. This eliminates the need for complex pyrotechnic triggering circuitry, safety interlocks, and special handling procedures while maintaining the ability to quickly sever cables.
4Ease of repair
If shape-memory actuators are used to reposition electrical contacts, then the mechanisms can be reset and tested easily, but the response time may be slower compared to pyrotechnic systems
Solution Approach 1:
The patent optimizes the SMA actuator response time by controlling the heating rate and temperature differential. By applying sufficient heating power and designing the SMA element with appropriate geometry and mass, the actuator can achieve rapid shape transformation. The reset process can also be accelerated through controlled cooling methods.
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 shape-memory-based mechanisms provide reliable and safe disconnection of electrical connections, preventing destructive electrical currents, reducing the risk of arcs, and allowing for easy scaling and maintenance, making them suitable for applications like flight vehicles and secure data facilities.
Implementation Method 1
a shape-memory actuator configured to change shape in response to a triggering event and thereby reposition the movable electrical contact so that the movable electrical contact no longer bridges the stationary electrical contacts
Implementation Method 2
When the movable electrical contact bridges the stationary electrical contacts, the electrical switch is closed and an electrical circuit is completed
Data Source
Figure 1A~1B
Figure 2A
Figure 2B
AI summary
An apparatus includes an electrical switch (202) that includes (i) multiple first electrical contacts (206, 208) and (ii) a second electrical contact (210) configured to bridge the first electrical contacts in order to form at least one electrical connection. The apparatus also includes a shape-memory actuator (204) configured to move the second electrical contact in order to selectively open the electrical switch and break the at least one electrical connection. The shape-memory actuator may be configured to be returned to an original shape and the second electrical contact may be configured to be returned to a bridging position in order to reset the apparatus. The apparatus may further include a shutter member (216) configured to be moved between the first electrical contacts in order to prevent re-bridging of the first electrical contacts and to extend an arc-gap between the first electrical contacts.