SMA Actuator Latch with Bistable Flexure

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Solution Overview

Problem

Current hard drive actuators rely on magnetic bias pins for latching, which may not be suitable for new types of actuator drives that require more force or different configurations, necessitating a low-cost, clean mechanical latch solution.

Innovation Solution

An actuator latch utilizing shape memory alloys (SMAs) with a bistable flexure that switches between multiple stable positions, comprising an upper and lower SMA wire, a flexure, and a spring, where the SMA wires can be pre-loaded and thermally actuated to change positions, allowing for a mechanical latch that can handle varying forces.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Force

If magnetic bias pins are used for latching, then the actuator can be controlled, but the latching force is insufficient for new actuator drives requiring more force

Engineering Contradiction:

Improvelatching forceVSAvoidcompatibility with new actuator configurations

Core Design Contradiction:

ForceVSAdaptability or versatility

Solution Approach 1:

The patent replaces the magnetic bias pin system with a shape memory alloy (SMA) wire-based mechanical latching system. The SMA wires provide the necessary latching force through their superelastic and shape memory properties, eliminating the need for magnetic fields while providing sufficient mechanical force for new actuator configurations that require higher latching forces.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent utilizes the temperature-dependent properties of shape memory alloys to change the latching force parameter. By heating or cooling the SMA wires, the system can transition between different latching states, allowing the same mechanism to adapt to different force requirements and actuator configurations without changing the physical structure.

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If a mechanical latch solution is designed to handle varying forces, then it can be more versatile, but the device complexity increases

Engineering Contradiction:

Improveability to handle varying forcesVSAvoidlatch mechanism complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent combines multiple functions into the SMA wire itself, which provides both the latching force and the actuation mechanism. The single SMA wire structure performs what would traditionally require separate components (spring, actuator, latch mechanism), thereby reducing overall device complexity while maintaining the ability to handle varying forces through material property changes.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent employs shape memory alloy materials that combine multiple functional properties (superelasticity, shape memory effect, and controlled deformation) into a single material system. This composite material approach allows the latch to handle varying forces through material property modulation rather than through complex mechanical adjustments, simplifying the overall device structure.

Inventive Principle:

Principle #40Composite materials

3Ease of manufacture

If SMA wires are used for latching, then a clean mechanical solution is achieved, but the manufacturing precision requirements increase

Engineering Contradiction:

Improveclean mechanical solutionVSAvoidSMA wire attachment precision

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent incorporates pre-loaded spring elements that are assembled in a predetermined state before final installation. This preliminary action allows the SMA wires and flexure components to be attached with relaxed tolerance requirements, as the pre-loaded springs compensate for minor variations in attachment precision, thereby maintaining ease of manufacture while achieving the desired latching performance.

Inventive Principle:

Principle #10Preliminary action

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-based actuator latch provides a reliable, low-cost mechanical solution that can handle the forces required by new actuator drives, offering a flexible and efficient mechanism for latching and unlocking actuators.

Implementation Method 1

the SMA wires can be pre-loaded and thermally actuated to change positions

Methodology Applied

Scientific EffectShape memory alloy thermal actuation: Shape Memory Alloy

Implementation Method 2

SMA-based actuator latch provides a reliable, low-cost mechanical solution that can handle the forces required by new actuator drives

Methodology Applied

Scientific EffectThermal energy transformation: Thermal Expansion

Implementation Method 3

a flexure having an opening, and a spring configured within the flexure opening

Methodology Applied

Scientific EffectElastic energy storage: Spring

Data Source

PatentUS11783858B2Shape memory alloy based actuator latch

Publication Date: 2023.10.10 SEAGATE TECH LLC

AI summary

A device disclosed herein includes an upper shape memory alloy (SMA) wire, a lower SMA wire, a flexure having an opening, and a spring configured within the flexure opening, wherein the lower SMA wire, and the flexure are attached at one end to an anchor and at another end to a pin.