Mid-Wheel Drive Wheelchair Swing Arm Assembly

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Solution Overview

Problem

Mid-wheel drive wheelchairs face challenges in maintaining traction and comfort due to the direct vibration input from drive wheels beneath the user's center of gravity, and existing suspension systems compromise between stability and comfort by requiring a stiff setup.

Innovation Solution

A swing arm assembly with a resilient member connecting the rear swing arm and drive assembly swing arm allows for force transfer, enabling independent suspension and improved comfort, while a linkage member maintains stability and traction by transmitting forces between the front and rear swing arms.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If a stiff suspension setup is used to maintain stability and prevent tipping, then stability is improved, but user comfort deteriorates due to increased vibrations and impacts transferred to the user

Engineering Contradiction:

ImprovestabilityVSAvoidvibrations transferred to user

Core Design Contradiction:

Stability of the object's compositionVSObject-affected harmful factors

Solution Approach 1:

The suspension system is divided into independent swing arms for each wheel (front swing arm, drive assembly swing arm, rear swing arm) that can move independently. This segmentation allows each wheel to absorb vibrations separately, improving comfort while maintaining overall stability through the resilient member connection.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent changes the stiffness parameter of the suspension by introducing a resilient member (spring) between the drive assembly swing arm and rear swing arm. This allows the system to be softer where needed (for comfort) while maintaining stability through the linkage member connection between front and rear swing arms.

Inventive Principle:

Principle #35Parameter changes

2Object-affected harmful factors

If a fully independent suspension is used where one wheel movement does not affect any other, then user comfort is improved, but the ability to maintain traction deteriorates

Engineering Contradiction:

Improvevibrations transferred to userVSAvoidtraction maintenance

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The resilient member acts as an intermediary element that connects the drive assembly swing arm and rear swing arm. It allows controlled force transfer between these components, enabling the system to maintain traction through force distribution while still providing independent wheel movement for comfort.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Ease of operation

If drive wheels are positioned directly beneath the user's centre of gravity for better manoeuvrability, then turning radius is improved, but user comfort deteriorates due to direct vibration input

Engineering Contradiction:

ImprovemanoeuvrabilityVSAvoidvibration input to user

Core Design Contradiction:

Ease of operationVSObject-affected harmful factors

Solution Approach 1:

The patent extracts the drive wheels from the direct path to the user's center of gravity by positioning them on swing arms that are pivotally connected to the frame at points spaced apart from the center of gravity. This extraction removes the source of direct vibration input while preserving the mid-wheel drive manoeuvrability benefits.

Inventive Principle:

Principle #2Taking out (Extraction)

4Reliability

If swing arms are connected to each other to improve traction, then traction is improved, but independence of suspension deteriorates

Engineering Contradiction:

ImprovetractionVSAvoidvibration transfer

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies different connection qualities to different parts of the suspension system. The linkage member provides a stiff connection between front and rear swing arms for stability and traction, while the resilient member provides a flexible connection between drive assembly and rear swing arms for vibration isolation. This local differentiation of connection qualities allows the system to achieve both traction and comfort.

Inventive Principle:

Principle #3Local quality

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

The swing arm assembly enhances user comfort by allowing independent wheel movement, maintains wheel contact with the ground, and provides increased traction on uneven surfaces, particularly at larger ditch angles.

Implementation Method 1

a resilient member configured to be connected to the resilient member first mounting point and to the resilient member second mounting point to enable force transfer between the drive assembly swing arm and the rear swing arm

Methodology Applied

Scientific EffectElasticity: Elasticity

Data Source

PatentUS10667970B2Swing arm assembly for a mid-wheel drive wheelchair

Publication Date: 2020.06.02 PERMOBIL

AI summary

The present disclosure relates to a swing arm assembly (1) for a mid-wheel drive wheelchair (21), comprising: a front swing arm (3) having a front swing arm pivot point (3a), a drive assembly swing arm (5) having a drive assembly swing arm pivot point (5a) and a resilient member first mounting point (5b), a rear swing arm (7) having a rear swing arm pivot point (7a) and a resilient member second mounting point (7b), and a resilient member (9) configured to be connected to the resilient member first mounting point (5a) and to the resilient member second mounting point (7a) to enable force transfer between the drive assembly swing arm (5) and the rear swing arm (7).