SMA Actuator Electrical Switching Device Reliability

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Solution Overview

Problem

Electrical switching devices, such as vacuum tube relays, suffer from reliability issues due to the failure of electromechanical actuators or solenoids, leading to high maintenance costs and downtime, especially in complex avionic equipment where multiple devices are required, and the failure of a single relay can result in costly aircraft grounding.

Innovation Solution

Employing an actuator mechanism formed of a shape memory alloy (SMA) that changes shape upon the application of an electric current to engage or disengage electrical contacts, thereby improving reliability and reducing costs by eliminating the need for complex assembly and replacement procedures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If electromechanical actuators or solenoids are used in vacuum tube electrical switching devices, then the devices can achieve reliable contact switching, but the actuators are prone to failure leading to high maintenance costs and downtime

Engineering Contradiction:

Improveactuator reliabilityVSAvoidassembly complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent replaces electromechanical actuators and solenoids with a shape memory alloy (SMA) actuator that uses thermal actuation instead of electromagnetic fields. The SMA actuator changes its shape in response to temperature changes, directly actuating the contacts without complex mechanical or electromagnetic components, thereby improving reliability while reducing assembly complexity

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The invention utilizes the temperature-dependent martensitic phase transformation of shape memory alloys to change the actuator's shape. By controlling the temperature parameter (heating or cooling the SMA), the actuator transitions between different shapes to open or close contacts, providing a simple and reliable switching mechanism without complex electromechanical components

Inventive Principle:

Principle #35Parameter changes

2Reliability

If multiple vacuum relays are used in HF antenna couplers, then the equipment can achieve proper impedance matching, but the failure of any relay requires costly replacement and aircraft grounding

Engineering Contradiction:

Improvesystem reliabilityVSAvoidassembly ease

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The SMA actuator replaces complex electromechanical relay mechanisms with a simpler thermal actuation system. The entire relay assembly can be manufactured as a more integrated unit with the SMA actuator directly coupled to the contacts, reducing the number of components that require careful hand soldering and assembly, thereby improving ease of manufacture while maintaining system reliability

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Ease of operation

If complex electromechanical actuators are used, then contact switching can be achieved, but the actuators require careful hand soldering and testing during manufacture

Engineering Contradiction:

Improveswitching operationVSAvoidassembly ease

Core Design Contradiction:

Ease of operationVSEase of manufacture

Solution Approach 1:

The SMA actuator eliminates complex electromechanical components that require precise assembly and soldering. The SMA element can be directly integrated into the contact assembly with simpler manufacturing processes, reducing the need for careful hand soldering and extensive testing while maintaining reliable contact switching operation

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The shape memory alloy actuator is self-actuating through thermal response. It automatically changes shape in response to temperature changes without requiring external electromagnetic fields or complex control mechanisms, simplifying both operation and manufacturing processes

Inventive Principle:

Principle #25Self-service

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 SMA actuator mechanism enhances the reliability of electrical switching devices by allowing for efficient engagement and disengagement of contacts with reduced maintenance needs, minimizing downtime and costs associated with relay failures in critical systems.

Implementation Method 1

Application of a first electrical current to the actuator causes the actuator to move the movable contact

Methodology Applied

Scientific EffectResistive heating: Joule Heating

Implementation Method 2

This capability results from a temperature-dependent martensitic phase transformation from a low-symmetry martensite structure to a highly symmetric crystallographic austennite structure

Methodology Applied

Scientific EffectMartensitic phase transformation: Phase Change

Data Source

PatentUS7928826B1Electrical switching devices using a shape memory alloy (SMA) actuation mechanism

Publication Date: 2011.04.19 ROCKWELL COLLINS INC

AI summary

An electrical switching device employs an actuator mechanism formed of a shape memory alloy (SMA). The electrical switching device includes a housing, at least one non-actuated electrical contact supported in the housing, and an actuator assembly contained within the housing. The actuator assembly includes a movable contact for engaging the non-actuated electrical contact and an actuator formed of a shape memory alloy (SMA). Application of a first electrical current to the actuator causes the actuator to move the movable contact to either engage or disengage the non-actuated electrical contact.