Finger Motion Rail With Lateral Multi-Joint Hinge Kinematics

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Solution Overview

Problem

Existing finger motion rails and therapeutic devices restrict natural finger movement due to mechanical kinematics, fail to adapt to individual fingers, and are prone to wear and tear from axial and torsional forces.

Innovation Solution

A finger motion rail designed with a multi-joint hinge mechanism for metacarpophalangeal joint flexion, connected to proximal and distal interphalangeal joints via levers, providing anatomically natural movement and enhanced robustness against axial and torsional forces.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If a carriage/rail movement kinematics is used for automated finger movement, then the movement comes close to anatomically natural finger movement, but the carriage is susceptible to twisting or axial forces which negatively influence the automated finger movement

Engineering Contradiction:

Improveanatomically natural finger movementVSAvoidresistance to twisting and axial forces

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The device is divided into separate functional modules: a multi-joint hinge mechanism for generating natural finger movement, a connection lever system for transmitting motion, and a pivot lever system for controlling joint angles. This segmentation allows each component to be optimized for its specific function while reducing susceptibility to harmful forces.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The connection lever acts as an intermediary element between the multi-joint hinge and the pivot lever, transmitting motion while filtering out harmful axial forces and twisting moments. This intermediary mechanism protects the drive system from forces that would otherwise damage it.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Extent of automation

If mechanical motion kinematics resting on the fingers are used, then automated finger movement can be achieved, but the finger movement is restricted and fingers cannot be treated individually

Engineering Contradiction:

Improveautomated finger movementVSAvoidfreedom of movement

Core Design Contradiction:

Extent of automationVSEase of operation

Solution Approach 1:

Each finger is equipped with its own dedicated multi-joint hinge mechanism and connection lever system, allowing individualized treatment and movement control. The device can independently control each finger's metacarpophalangeal, proximal interphalangeal, and distal interphalangeal joints without restricting movement of other fingers.

Inventive Principle:

Principle #3Local quality

3Adaptability or versatility

If flexible rods are arranged directly above the fingers for passive and actively assisted movement, then simultaneous and/or selective flexion/extension can be achieved, but the rods restrict the freedom of movement

Engineering Contradiction:

Improvesimultaneous and selective flexion/extensionVSAvoidfreedom of movement

Core Design Contradiction:

Adaptability or versatilityVSEase of operation

Solution Approach 1:

The mechanical components (multi-joint hinge, connection levers, pivot levers) are extracted from direct contact with the fingers and repositioned laterally alongside them. This eliminates the restriction of movement while maintaining the ability to control finger motion through the lever systems.

Inventive Principle:

Principle #2Taking out (Extraction)

4Ease of operation

If a multi-joint hinge mechanism is used for metacarpophalangeal joint flexion connected to proximal and distal interphalangeal joints, then anatomically natural movement is achieved, but the device complexity increases

Engineering Contradiction:

Improveanatomically natural movementVSAvoidmechanism structure

Core Design Contradiction:

Ease of operationVSDevice complexity

Solution Approach 1:

The multi-joint hinge mechanism combines multiple functions into a single integrated component: it generates natural metacarpophalangeal joint movement while simultaneously controlling proximal and distal interphalangeal joints through connection levers. This merging reduces overall system complexity compared to separate mechanisms for each joint.

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS12485055B2Finger motion rail for carrying out a continuous, passive and/or actively assisted movement of a finger and/or a thumb of a patient, as well as a therapeutic device comprising a finger motion rail of this type

Publication Date: 2025.12.02 UNIVERSITATSMEDIZIN DER JOHANNES GUTENBERG UNIV MAINZ

AI summary

A finger motion rail, and a therapeutic device with a finger motion rail for carrying out a continuous, passive and/or actively assisted movement of a finger and/or thumb. A multi-joint hinge, arranged laterally alongside a finger and/or thumb, for flexion of a metacarpophalangeal joint. The multi-joint hinge is operatively connected via a first connection lever, at least one second connection lever and at least one connection joint, to a mechanism also arranged laterally alongside the respective finger and/or thumb, for flexion of a proximal interphalangeal joint and/or a distal interphalangeal joint. The finger motion rail and therapeutic device is configured as robust against the effect of compressive, tensile and torsional forces, with respect to a longitudinal axis of the finger motion rail, and it permits precise and interference-free execution of an anatomically natural, automated finger movement, for increased chance of successful therapy and the service life of the device.