Push-Push Latch With Shape Memory Alloy Actuator

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Solution Overview

Problem

Existing push-push latch mechanisms in applications such as fuel filler doors require complex motor systems for locking and unlocking, which are costly and bulky, and lack efficient control over access.

Innovation Solution

The integration of a Shape Memory Alloy (SMA) actuator that selectively locks or enables the push-push latch operation, allowing for an electrically controlled, compact, and lower-mass alternative by using SMA wires to control the latch's motion through temperature changes, eliminating the need for large motors and providing controlled access.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a motor system is used for locking and unlocking the push-push latch, then the locking function is achieved, but the device becomes bulky and costly

Engineering Contradiction:

Improvelocking functionVSAvoidmotor system complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent replaces the motor system with a Shape Memory Alloy (SMA) actuator that uses thermal-mechanical properties to achieve locking and unlocking functions. The SMA wire transforms from martensite to austenite phase when heated, generating mechanical force to move the interference member and control latch operation, thereby eliminating bulky motors while maintaining reliable locking functionality

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The invention utilizes phase transformation temperature changes in Shape Memory Alloy as the controlling parameter. By heating the SMA wire to its transformation temperature, the material changes from soft martensite phase to rigid austenite phase, generating sufficient mechanical force to actuate the latch mechanism. This parameter-based control replaces complex motor systems with a simpler thermal-actuation approach

Inventive Principle:

Principle #35Parameter changes

2Reliability

If a motor system is used for locking and unlocking the push-push latch, then the locking function is achieved, but the mass increases

Engineering Contradiction:

Improvelocking functionVSAvoidlatch system mass

Core Design Contradiction:

ReliabilityVSWeight of moving object

Solution Approach 1:

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The invention employs Shape Memory Alloy, a composite material with unique thermomechanical properties, to create a compact actuator. The SMA wire's ability to undergo reversible phase transformation and generate high force per unit mass enables significant weight reduction compared to traditional motor systems while maintaining the required locking reliability

Inventive Principle:

Principle #40Composite materials

3Device complexity

If traditional latch mechanisms are used, then the structure is simple, but control over access is inefficient

Engineering Contradiction:

Improvelatch structureVSAvoidaccess control efficiency

Core Design Contradiction:

Device complexityVSEase of operation

Solution Approach 1:

The patent introduces an interference member as an intermediary element controlled by the SMA actuator. This interference member selectively blocks or permits engagement between the pin member and cam-track, providing efficient access control. The intermediary mechanism maintains relatively simple latch structure while enabling controlled access through the SMA-actuated interference member that can prevent or allow pin engagement based on thermal activation

Inventive Principle:

Principle #24Intermediary (Mediator)

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 actuated push-push latch enables efficient, compact, and cost-effective operation by allowing controlled access and reducing the complexity of locking mechanisms, while maintaining ease of use and reliability.

Implementation Method 1

A shape memory alloy actuator is to selectively cause the interference member to selectively prevent the pin member from engaging the closed course

Methodology Applied

Scientific EffectShape Memory Alloy: Shape Memory Alloy

Implementation Method 2

A resilient element is to urge the slider toward an extended state

Methodology Applied

Scientific EffectElasticity: Elasticity

Data Source

PatentUS9895969B2Push-push latch

Publication Date: 2018.02.20 GM GLOBAL TECHNOLOGY OPERATIONS LLC

AI summary

A push-push latch includes a slider slidably disposed on a frame. A resilient element is to urge the slider toward an extended state. The slider or the frame defines a cam-track. A pin member is connected to the frame or the slider. The pin member selectably engages a closed course in the cam-track to cause the slider to alternate between a retracted state and the extended state in response to alternating application and removal of an actuating force on the slider. An interference member is on the frame to selectively prevent the pin member from engaging the closed course thereby locking the slider in the retracted state. A pivotable catch is rotatably on the slider to open in the extended state and to close in the retracted state. A shape memory alloy actuator selectively causes the interference member to selectively prevent the pin member from engaging the closed course.