Caster Wheel Suspension Damping Vertical and Torsional Shock

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Solution Overview

Problem

Existing lawn mowers with freewheeling caster wheels experience excessive jarring due to compressive and torsional forces from rough terrain, limiting mowing speed and traction, especially for professional landscape lawnmowers with near zero turn radius capabilities.

Innovation Solution

A compression and torsion damping wheel suspension system incorporating elastomeric rubber elements and a torsional spring, integrated into the offset shaft connecting the front caster wheels to the pivot axis, absorbs both compressive and torsional shocks, allowing the mower to maintain traction and speed over uneven terrain.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If a torsion resistance mechanism is used to prevent lateral movement of caster wheels, then lateral stability is improved, but vertical shock absorption capability deteriorates

Engineering Contradiction:

Improvelateral stabilityVSAvoidvertical shock

Core Design Contradiction:

Stability of the object's compositionVSObject-affected harmful factors

Solution Approach 1:

The suspension system divides the shock absorption function into separate components: elastomeric elements handle vertical compression while torsion bars manage lateral stability. This segmentation allows each component to specialize in one type of shock without compromising the other function.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The suspension assembly performs multiple functions simultaneously: the elastomeric elements provide vertical shock absorption while the torsion bars provide lateral stability. This multi-functionality resolves the contradiction by making the system capable of handling both vertical and lateral shocks through different mechanisms working in parallel.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Stability of the object's composition

If caster wheels are made rigid to maintain orientation on rough terrain, then orientation stability is improved, but operator comfort deteriorates due to excessive jarring

Engineering Contradiction:

Improveorientation stabilityVSAvoidoperator jarring

Core Design Contradiction:

Stability of the object's compositionVSObject-affected harmful factors

Solution Approach 1:

The suspension system applies different mechanical properties to different parts of the wheel assembly: elastomeric elements at compression points provide vertical compliance to reduce jarring, while torsion bars at lateral connection points maintain orientation stability. This local differentiation of mechanical properties resolves the contradiction between rigidity and comfort.

Inventive Principle:

Principle #3Local quality

3Object-affected harmful factors

If shock absorption elements are added to caster wheel suspension, then operator comfort is improved, but device complexity increases

Engineering Contradiction:

Improveoperator comfortVSAvoidsuspension system complexity

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The elastomeric elements are nested within the caster wheel assembly structure, with the torsion bars integrated into the same assembly. This nesting approach consolidates multiple shock absorption functions into a compact integrated unit, minimizing the increase in overall device complexity while providing comprehensive shock protection.

Inventive Principle:

Principle #7Nested doll (Nesting)

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 system provides a comfortable ride for operators while enabling professional landscape lawnmowers to mow at nearly twice the speed without losing traction, even when encountering bumps or rocks, by effectively absorbing shock and maintaining wheel orientation.

Implementation Method 1

a plurality of elastomeric elements disposed within said spaces and surrounding said second tube, said elastomeric elements absorbing compressive vertical forces

Methodology Applied

Scientific EffectElasticity: Elasticity

Implementation Method 2

a torsional spring absorbing torsional loads

Methodology Applied

Scientific EffectTorsion spring: Torsion Spring

Data Source

PatentUS8210552B2Compression and torsion damping wheel suspension system

Publication Date: 2012.07.03 NANCE JOHN D

AI summary

A compression and torsion damping wheel suspension system is useful for damping compressive and torsional shock encountered by freewheeling front caster wheels of a professional landscape lawn mower. The freewheeling caster wheels are mounted with an offset from a vertical pivot axis attached to the lawn mower frame. The compression and torsion damping wheel suspension system comprises two tubes one having internal extending projections and the other having external extending projections The smaller tube is turned within the larger tube, leaving behind several spaces within which are contained four elastomeric elements. When the caster wheel rides over a rock or bump, the elastomeric elements are compressed, damping compression shock. Caster wheel resistance is felt; the elastomeric elements experience torsion and are damped, providing a smooth ride for the operator.