Lawn Mower Post-Compression Blade Airflow

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Solution Overview

Problem

Existing lawn mower air circulating systems face challenges in maintaining optimal pressure differences to effectively collect grass clippings without causing excessive vibrations, noise, or dust emission, while avoiding clogging of channels.

Innovation Solution

A lawn mower design featuring a post-compression blade and a protection flange with radial vents, which creates a vorticose motion and optimal pressure differences to enhance airflow and collection efficiency, reducing vibrations and noise, and preventing dust emission.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If a toroidal channel and flange with vents are used to circulate air in the lawn mower, then grass clippings can be collected in the bag, but channel clogging occurs and vibrations and noise increase

Engineering Contradiction:
Improvegrass clipping collection efficiencyVSAvoidchannel clogging, vibrations, noise
Core Design Contradiction:
ProductivityVSObject-generated harmful factors

Solution Approach 1:

The patent changes the pressure parameter distribution by introducing a post-compression blade that creates a localized high-pressure zone. This modifies the airflow parameters to maintain stronger pressure gradients throughout the channel system, preventing clogging while controlling vibrations and noise through optimized pressure distribution

Inventive Principle:
Principle #35Parameter changes

2Productivity

If the pressure difference in the air circulating system is increased to improve grass clipping evacuation, then collection efficiency improves, but excessive vibrations and noise occur

Engineering Contradiction:
Improvegrass clipping evacuation efficiencyVSAvoidvibrations, noise
Core Design Contradiction:
ProductivityVSObject-generated harmful factors

Solution Approach 1:

The post-compression blade creates a localized high-pressure zone at specific positions in the airflow path rather than uniformly increasing pressure throughout the system. This localized approach maintains strong evacuation capability where needed while avoiding excessive pressure differences that cause vibrations and noise in other areas

Inventive Principle:
Principle #3Local quality

3Object-generated harmful factors

If the pressure difference is decreased to reduce vibrations and noise, then grass clipping collection is insufficient and channels clog

Engineering Contradiction:
Improvevibrations, noiseVSAvoidgrass clipping collection efficiency
Core Design Contradiction:
Object-generated harmful factorsVSProductivity

Solution Approach 1:

The system uses a rotating post-compression blade that dynamically creates moving high-pressure zones throughout the airflow path. This dynamic approach ensures continuous effective pressure gradients for grass clipping evacuation while allowing the pressure distribution to adapt and balance, preventing excessive vibrations and noise

Inventive Principle:
Principle #15Dynamics

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 design effectively collects grass clippings by creating higher pressure gradients, reducing channel clogging, vibrations, and noise, while maintaining cleanliness and protecting rotating components from debris.

Implementation Method 1

a post-compression blade (7) secured under blade (30) so that the base of post-compression blade (7) lays on the same cutting plane (V) as blade (30), said post-compression blade (7) providing a flat circular portion (70) which serves as base and completely covers the width of blade (30) for the entire diameter thereof

Methodology Applied
Scientific EffectCompression: Compression

Implementation Method 2

The air flow (80) which penetrates into space (86) from the vents (56), is already at a higher pressure than the atmospheric pressure since it passes through the narrowing of vent (56) caused by the radial fins (61)

Methodology Applied
Scientific EffectPressure gradient: Pressure Gradient

Implementation Method 3

A lawn mower design featuring a post-compression blade and a protection flange with radial vents, which creates a vorticose motion and optimal pressure differences to enhance airflow and collection efficiency

Methodology Applied
Scientific EffectVortex flow: Vortex Ring

Data Source

PatentEP2829169B1Lawn mower with post-compression blade
Publication Date: 2018.04.04 STIGA S P A IN BREVE ANCHE ST SPA
  • EP2829169B1 patent drawingFigure 1
  • EP2829169B1 patent drawingFigure 2
  • EP2829169B1 patent drawingFigure 3~4

AI summary

A lawn mower is described comprising a load-bearing body (10), a motor (20) supported by the load-bearing body (10), a cutting blade (30) connected to the motor (20), a bag (40) for containing the grass clippings applied to the rear of the load-bearing body (10), a flange (50) provided with a series of vents (56) and applied to the body (10) so as to separate a central chamber (13) from the cutting blade (30), comprising a post-compression blade (7) of air flow (80) coming from the vents (56) arranged in a space (86) between the blade (30) and the flange (50) and adapted to create pressure gradients of the air flow (80) during rotation.