Prosthetic Thumb Locking Mechanism for Dual-Axis Motion

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Solution Overview

Problem

Prosthetic thumbs in existing prosthetic hands have a limited range of motion, making it difficult for users to form desired positions such as a fist or pinch objects, and dual motor actuation systems increase weight and bulk, compromising watertightness.

Innovation Solution

A prosthetic hand design with a proximal and distal thumb part, each rotating about separate axes, using a single rotary actuator and a locking mechanism to switch between configurations, allowing sequential movement of the thumb parts through multiple positions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If dual motor actuation systems are used to rotate the prosthetic thumb about two different axes of rotation, then the range of motion of the prosthetic thumb is improved, but the weight and bulk of the prosthetic hand increase

Engineering Contradiction:

Improverange of motion of prosthetic thumbVSAvoidweight of prosthetic hand

Core Design Contradiction:

Adaptability or versatilityVSWeight of moving object

Solution Approach 1:

The patent combines two motor functions into a single rotary actuator by using a locking mechanism that sequentially engages different joints. The locking mechanism has two configurations: in the first configuration, it locks the distal thumb part relative to the proximal thumb part, allowing the actuator to rotate both parts about the first axis; in the second configuration, it locks the proximal thumb part relative to the palm part, allowing the actuator to rotate the distal thumb part about the second axis. This merging of functions reduces the number of motors from two to one, thereby reducing weight and bulk.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The locking mechanism dynamically switches between two configurations to enable the single rotary actuator to perform two different rotational functions. The mechanism is configured to switch between configurations based on the operational requirements, allowing the system to adapt its mechanical structure during operation. This dynamic reconfiguration enables one actuator to replace two motors while maintaining full range of motion capability.

Inventive Principle:

Principle #15Dynamics

2Adaptability or versatility

If dual motor actuation systems are used to rotate the prosthetic thumb about two different axes of rotation, then the range of motion of the prosthetic thumb is improved, but the bulk of the prosthetic hand increases

Engineering Contradiction:

Improverange of motion of prosthetic thumbVSAvoidbulk of prosthetic hand

Core Design Contradiction:

Adaptability or versatilityVSVolume of moving object

Solution Approach 1:

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

Inventive Principle:

Principle #15Dynamics

3Weight of moving object

If at least one of the dual motors is disposed adjacent to the user's wrist, then the bulk and weight of the prosthetic hand are reduced, but watertightness is compromised due to electrical cables being threaded through the prosthetic hand

Engineering Contradiction:

Improveweight of prosthetic handVSAvoidwatertightness of prosthetic hand

Core Design Contradiction:

Weight of moving objectVSReliability

Solution Approach 1:

Inventive Principle:

Principle #5Merging (Combining)

4Weight of moving object

If a single rotary actuator is used with a locking mechanism, then the weight and bulk of the prosthetic hand are reduced, but the complexity of the locking mechanism increases

Engineering Contradiction:

Improveweight of prosthetic handVSAvoidcomplexity of locking mechanism

Core Design Contradiction:

Weight of moving objectVSDevice complexity

Solution Approach 1:

The locking mechanism is segmented into two distinct configurations, each serving a specific function. The mechanism includes a movable locking element that can be positioned in two locations: a first location for locking the distal thumb part relative to the proximal thumb part, and a second location for locking the proximal thumb part relative to the palm part. This segmentation allows the complex function of dual-axis rotation to be broken down into two simpler, manageable locking states.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The locking mechanism employs different locking arrangements for different joints: a first locking arrangement for the first joint (proximal thumb part to palm part) and a second locking arrangement for the second joint (distal thumb part to proximal thumb part). Each locking arrangement is optimized for its specific joint, allowing the system to manage complexity through localized, specialized solutions rather than a single universal locking mechanism.

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS20260020968A1Prosthetic hand

Publication Date: 2026.01.22 OPEN BIONICS LTD

AI summary

A prosthetic hand comprises a palm part; a proximal thumb part coupled to the palm part to form a first joint with a first axis of rotation, wherein the proximal thumb part is configured to rotate about the first axis of rotation; a distal thumb part coupled to the proximal thumb part to form a second joint with a second axis of rotation, wherein the distal thumb part is configured to rotate about the second axis of rotation; a rotary actuator configured to rotate the proximal thumb part and distal thumb part about the first axis of rotation and the second axis of rotation respectively; and a locking mechanism having a first configuration and a second configuration.