Manual Wheelchair Push Rim Decoupling for Biomechanics

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Solution Overview

Problem

Conventional manual wheelchairs face stability and shoulder biomechanics issues due to the direct mechanical coupling of push rims and drive wheels, which limits optimal positioning for propulsion and transfer, leading to reduced stability and increased shoulder strain.

Innovation Solution

A manual wheelchair system that decouples push rims from drive wheels using a belt or chain drive, allowing for independent positioning and the inclusion of multispeed fixed-gear hubs, with removable or rotatable push rims for improved stability and easier transfers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If the push rim and drive wheel are directly coupled together, then the structure is simple, but the positioning flexibility is reduced leading to shoulder biomechanics problems and stability issues

Engineering Contradiction:

Improvestructural simplicityVSAvoidpositioning flexibility

Core Design Contradiction:

Device complexityVSAdaptability or versatility

Solution Approach 1:

The direct mechanical coupling between push rim and drive wheel is segmented into separate components. The push rim is now independently positionable on the drive wheel assembly, allowing separate optimization of push rim position for shoulder biomechanics and drive wheel position for stability. This segmentation resolves the contradiction by enabling positioning flexibility without requiring complete structural redesign.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The push rim positioning system is made dynamic and adjustable rather than fixed. The push rim can be positioned at multiple locations along the drive wheel assembly and locked in place, providing adaptability for different user needs while maintaining structural simplicity through a standardized adjustment mechanism.

Inventive Principle:

Principle #15Dynamics

2Ease of operation

If the push rim is positioned forward to improve shoulder biomechanics, then propulsion efficiency is improved, but wheelchair stability is reduced

Engineering Contradiction:

Improvepropulsion efficiencyVSAvoidwheelchair stability

Core Design Contradiction:

Ease of operationVSStability of the object's composition

Solution Approach 1:

The coupling between push rim position and drive wheel position is segmented, allowing independent optimization. The push rim can be positioned forward on the drive wheel assembly to improve shoulder biomechanics and propulsion efficiency, while the drive wheel itself remains positioned backward relative to the center of gravity to maintain stability. This resolves the contradiction by decoupling the positional constraints.

Inventive Principle:

Principle #1Segmentation

3Stability of the object's composition

If the push rim is fixed in position, then the structure is stable, but transfers become difficult requiring elevated body position

Engineering Contradiction:

Improvestructural stabilityVSAvoidtransfer ease

Core Design Contradiction:

Stability of the object's compositionVSEase of operation

Solution Approach 1:

The push rim positioning system is made dynamically adjustable to accommodate different operational modes. During transfers, the push rim can be repositioned to a location that clears the user's body path, making transfers easier. During propulsion, the push rim is positioned optimally for shoulder biomechanics. The system maintains structural stability through secure locking mechanisms while providing the flexibility needed for transfers.

Inventive Principle:

Principle #15Dynamics

4Adaptability or versatility

If a belt or chain drive is used to decouple push rims from drive wheels, then positioning flexibility is improved, but device complexity increases

Engineering Contradiction:

Improvepositioning flexibilityVSAvoidtransmission complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

A belt or chain drive is introduced as an intermediary mechanism between the push rim and drive wheel. This intermediary allows the push rim to be positioned independently on the drive wheel assembly while still transmitting propulsion force effectively. The belt/chain drive provides the necessary flexibility for independent positioning while maintaining a relatively simple overall structure compared to direct mechanical coupling with multiple constraints.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS10588795B2Manual wheelchair system for improved propulsion and transfers

Publication Date: 2020.03.17 REGENTS OF THE UNIVERSITY OF MINNESOTA

AI summary

A manual wheelchair including a collapsible frame having a first lateral member that is connected to first and second braces at their respective first ends. A drive wheel axel extends along a first axis of rotation and engages a drive wheel, the first brace, and a portion of a transmission. A push rim axel extends along a second axis of rotation and engages a push rim wheel, the second brace, and a portion of the transmission, which transmits rotation of the push rim to rotation of the drive wheel. The collapsible frame additionally includes a second lateral member that is connected to the first and second braces as their respective second ends. The first and second braces are configured to release the second lateral member to collapse the manual wheelchair.