Pawl Actuator Using Shape-Memory Alloy for Large-Step Motion

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Solution Overview

Problem

Traditional actuators like motors and solenoids are unsuitable for small, cost-constrained applications due to their size and expense, and shape-memory alloys are limited in their ability to provide quick, large, or forceful displacements.

Innovation Solution

The design incorporates a Tooth Actuator with Advancement and Hold Pawls, utilizing shape-memory alloys to convert short distance actuation into larger motion through a mechanism of optimized tooth engagement and tensioners, allowing for compact, low-cost actuators that can achieve greater actuation capability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If traditional actuators (motors and solenoids) are used, then actuation capability is achieved, but size and cost increase

Engineering Contradiction:

Improveactuation capabilityVSAvoidactuator size

Core Design Contradiction:

PowerVSVolume of moving object

Solution Approach 1:

The actuator is segmented into multiple discrete teeth (e.g., 10 teeth) that can engage sequentially with pawls. Each tooth represents a discrete unit of motion, allowing the actuator to achieve large total displacement through multiple small steps rather than requiring a single large-motion component. This segmentation enables compact sizing while maintaining actuation capability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The actuator employs periodic engagement of advancement pawls and hold pawls with the teeth in a cyclic sequence. The advancement pawl engages a tooth, the shape-memory alloy contracts to advance the tooth, then the hold pawl engages to maintain position. This periodic action pattern allows continuous actuation through repeated small motions, achieving large overall displacement from compact components.

Inventive Principle:

Principle #19Periodic action

2Power

If traditional actuators (motors and solenoids) are used, then actuation capability is achieved, but cost increases

Engineering Contradiction:

Improveactuation capabilityVSAvoidmanufacturing cost

Core Design Contradiction:

PowerVSEase of manufacture

Solution Approach 1:

The patent replaces expensive motors and solenoids with inexpensive shape-memory alloy elements and simple mechanical pawls. The shape-memory alloy can be implemented as thin wires or small blocks that are far cheaper than traditional actuator components. The mechanical pawls and teeth are simple stamped or machined parts with no complex electronics, significantly reducing manufacturing cost while maintaining actuation capability.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The patent substitutes complex electromechanical systems (motors, solenoids, drivers, controllers) with a purely mechanical system based on shape-memory alloy deformation and pawl-tooth engagement. This eliminates expensive electronic components and simplifies manufacturing to basic mechanical fabrication processes, dramatically reducing cost while achieving the required actuation.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Volume of moving object

If shape-memory alloys are used for actuation, then cost and size are reduced, but displacement capability is limited

Engineering Contradiction:

Improveactuator sizeVSAvoiddisplacement distance

Core Design Contradiction:

Volume of moving objectVSLength of moving object

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The actuator maintains continuous useful action through the coordinated operation of advancement pawls and hold pawls. While one pawl is engaged with a tooth, the system is ready to immediately engage the next tooth. The hold pawl maintains position during transitions, ensuring continuous actuation capability without dead time. This continuity allows the compact shape-memory alloy to achieve large total displacement through uninterrupted sequential engagement of multiple teeth.

Inventive Principle:

Principle #20Continuity of useful 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

This solution enables the use of actuators in small spaces with reduced cost while providing flexible implementation options, overcoming the limitations of traditional actuators in terms of size and cost, and enabling wider application in smaller products.

Implementation Method 1

Shape-memory alloys, in the form of wire possess interesting capabilities, which when combined with novel mechanical structures enables cost effective fit-for-purpose actuators or actuator systems

Methodology Applied

Scientific EffectShape memory alloy: Shape Memory Alloy

Data Source

PatentUS11725715B1Advance and hold pawl actuator

Publication Date: 2023.08.15 OPSIS HEALTH INC

AI summary

In an actuator system having a toothed actuator and a tensioner to apply a tension force to the toothed actuator, a hold mechanism holds the tooth actuator stationary, through disengage-able contact with at least one tooth thereof, with respect to a direction of the tension force while allowing the tooth actuator to move freely in a direction opposite the direction of the tension force. An advancement pawl having at least two degrees of freedom engages with one or more teeth on the tooth actuator to displace the tooth actuator a distance in the direction opposite of the direction of the tension force.