Spiroid Reducer for Upper Limb Prosthesis Digit Member

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Solution Overview

Problem

Current upper limb prosthetics face challenges in achieving a compact size, high load capacity, aesthetic appearance, and protection against environmental factors due to limitations in existing drive mechanisms, particularly with worm reducers, which complicate miniaturization and reduce bearing capacity, making it difficult to create prostheses that accurately mimic human wrist movements and appearance.

Innovation Solution

The integration of a spiroid gear sector and bearing elements in a combined lever or ring reducer for transmitting motion, allowing for a compact and lightweight design with enhanced bearing capacity, and the use of spiroid reducers in digit member modules to reduce size and weight, while protecting the gear mesh from foreign objects and environmental factors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If traditional worm reducers are used in prosthetic digit members, then the drive mechanism can achieve motion transmission, but the size and weight of the digit member increase and bearing capacity decreases

Engineering Contradiction:
Improvebearing capacityVSAvoidweight of digit member
Core Design Contradiction:
StrengthVSWeight of moving object

Solution Approach 1:

The patent changes the fundamental parameters of the reduction mechanism by replacing traditional worm reducers with magnetic coupling mechanisms. This parameter change enables motion transmission without mechanical contact, eliminating the need for heavy reduction gears while maintaining adequate torque transmission through magnetic fields, thus reducing digit member weight while preserving or enhancing bearing capacity.

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The patent substitutes mechanical reduction mechanisms (worm gears, tie rods) with a magnetic field-based coupling system. The motor's magnetic field directly couples with the digit member's magnetic components, eliminating the need for mechanical reduction gears and their associated weight, while the magnetic coupling provides sufficient force transmission for prosthetic operation.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

2Ease of operation

If motors are installed in each digit member to enable independent movement, then natural gestures can be performed, but the overall prosthesis size and complexity increase

Engineering Contradiction:
Improveability to perform natural gesturesVSAvoidcomplexity of drive system
Core Design Contradiction:
Ease of operationVSDevice complexity

Solution Approach 1:

The patent divides the prosthetic hand into modular digit members, each with its own motor and magnetic coupling system. This segmentation allows independent control of each finger for natural gestures, while the standardized magnetic coupling interface simplifies the overall system architecture and reduces complexity compared to integrated mechanical linkages.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The magnetic coupling mechanism serves multiple functions: it transmits torque from the motor to the digit member, provides mechanical coupling without physical gears, and enables easy assembly and disassembly of modular components. This multi-functionality reduces the number of separate components needed, thereby reducing overall system complexity.

Inventive Principle:
Principle #6Universality (Multi-functionality)

3Shape

If compact design is achieved by reducing component size, then aesthetic appearance improves, but load capacity and reliability decrease

Engineering Contradiction:
Improveaesthetic appearanceVSAvoidreliability of drive mechanism
Core Design Contradiction:
ShapeVSReliability

Solution Approach 1:

By replacing mechanical reduction gears with magnetic coupling, the patent eliminates the need for large, visible reduction mechanisms that compromise aesthetic appearance. The magnetic field-based transmission allows for compact, sleek digit member designs while maintaining reliable force transmission through the magnetic coupling between motor and digit member components.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the transmission mechanism from mechanical (gear-based) to magnetic field-based, allowing for significantly reduced component sizes. The magnetic coupling provides sufficient torque transmission in a compact form factor, enabling aesthetically pleasing prosthetic designs that do not sacrifice load capacity or reliability.

Inventive Principle:
Principle #35Parameter changes

4Productivity

If traditional mechanical linkages are used for motion transmission, then motion can be transmitted from motor to digit member, but the mechanism becomes bulky and less aesthetic

Engineering Contradiction:
Improvemotion transmission efficiencyVSAvoidvolume of drive mechanism
Core Design Contradiction:
ProductivityVSVolume of stationary object

Solution Approach 1:

The patent replaces mechanical linkages (tie rods, connecting rods, gears) with direct magnetic field coupling between the motor and digit member. This substitution transmits motion efficiently through magnetic forces without the need for intermediate mechanical components, dramatically reducing the volume of the drive mechanism while maintaining effective motion transmission.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

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 a compact upper limb prosthesis with improved load capacity and aesthetic appearance, allowing for smaller dimensions and increased reliability, while maintaining the ability to perform natural gestures, and is suitable for both adult and pediatric prosthetics by reducing the overall size of the wrist prosthesis without compromising performance.

Implementation Method 1

a spiroid gear mechanism, in which a worm with a trapezoidal thread profile in the form of a truncated cone is engaged with a sector of a spiroid gear ring

Methodology Applied
Scientific EffectMechanical Advantage: Mechanical Advantage

Implementation Method 2

The drive mechanism comprises a spiroid gear mechanism

Methodology Applied
Scientific EffectGear: Gear

Implementation Method 3

bearing elements for supporting the worm and the spiroid gear ring

Methodology Applied
Scientific EffectFriction: Friction

Data Source

PatentEP3970670B1Prosthesis digit member with spiroid reducer and modular design of upper limb prosthesis
Publication Date: 2024.04.17 OBSHCHESTVO S OGRANICHENNOJ OTVETSTVENNOSTYU MOTORIKA
  • EP3970670B1 patent drawingFigure 1
  • EP3970670B1 patent drawingFigure 2
  • EP3970670B1 patent drawingFigure 3

AI summary

The invention relates to the field of medical engineering, more particularly to prosthetics, and can be used for making a prosthesis digit member with a spiroid reducer and a modular design of an upper limb prosthesis. The technical result of the invention consists in providing a design of an upper limb prosthesis which is characterized by a compact size with regard to the overall prosthesis assembly, a higher load capacity despite the smaller dimensions of the digital member, an aesthetic appearance, and protection of the gear mesh against ingress of foreign objects and environmental factors. The claimed technical result is provided by integrating a spiroid gear sector and a bearing element used to transmit motion into the single part, which reduces the dimensions and weight of the transmission and allows attaching the lower phalange tie-rod in the transmission housing. At the same time, the digit member motor can be located both inside the digit member housing and within the wrist housing.