Elastic Guide Device for Autonomous Lawn Mower Noise Reduction

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Solution Overview

Problem

Lawn mowers often generate noise due to radial play between the chassis and engine housing, leading to increased noise emissions and load on the cutting device, drive, height adjustment device, and chassis.

Innovation Solution

A guide device is designed to be elastically displaceable in the circumferential direction around the height adjustment axis, providing axial and rotational guidance to the sliding seat and rotating body, thereby damping torque forces and reducing noise and load on the components.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the guide device is made rigid to ensure precise guidance, then guidance precision is improved, but noise emissions and stress on components increase

Engineering Contradiction:
Improveguidance precisionVSAvoidnoise emissions
Core Design Contradiction:
Measurement precisionVSObject-generated harmful factors

Solution Approach 1:

The guide device incorporates elastic elements that allow dynamic displacement in the circumferential direction, enabling the structure to adapt to operational forces while maintaining guidance precision. This dynamic flexibility reduces noise by allowing controlled movement rather than rigid constraint.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

Elastic elements are introduced as intermediary components between the guide device and the components being guided. These intermediaries absorb and dampen forces, reducing stress transmission and noise emissions while preserving the guidance function.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Stability of the object's composition

If the guide device is made rigid to prevent radial play, then stability is improved, but stress on the cutting device and drive increases

Engineering Contradiction:
ImprovestabilityVSAvoidstress on cutting device and drive
Core Design Contradiction:
Stability of the object's compositionVSStress or pressure

Solution Approach 1:

The guide device uses elastic elements that provide dynamic compliance, allowing the structure to maintain stability through controlled flexibility rather than rigid fixation. This reduces stress on connected components by absorbing operational forces.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

Elastic elements are pre-installed in the guide device to provide beforehand cushioning against radial forces and moment forces. This pre-compliance structure absorbs shocks and reduces stress transmission to the cutting device and drive before forces are fully transmitted.

Inventive Principle:
Principle #11Beforehand cushioning (Prior cushioning)

3Object-generated harmful factors

If elastic displacement is allowed to reduce noise, then noise emissions are reduced, but guidance precision may be compromised

Engineering Contradiction:
Improvenoise emissionsVSAvoidguidance precision
Core Design Contradiction:
Object-generated harmful factorsVSMeasurement precision

Solution Approach 1:

The elastic elements are designed with specific displacement characteristics that allow noise-reducing movement while maintaining sufficient guidance precision through controlled compliance. The elasticity is tuned to provide necessary flexibility without excessive play.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The elastic properties of the guide device are optimized by adjusting parameters such as material selection, geometry, and pre-tension to achieve the right balance between noise reduction through elastic displacement and maintenance of guidance precision.

Inventive Principle:
Principle #35Parameter changes

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 solution effectively reduces noise emissions and load on the lawn mower components by damping torque and radial forces, enhancing the operational stability and reducing vibration transmission.

Implementation Method 1

the guide means(s) are designed to be elastically displaceable in the circumferential direction around the height adjustment axis

Methodology Applied
Scientific EffectElasticity: Elasticity

Implementation Method 2

moment forces from the motor or cutting device can be transmitted to the guide device and/or the chassis in a dampened manner

Methodology Applied
Scientific EffectDamping: Damping

Data Source

PatentEP3837950B1Lawn mower
Publication Date: 2024.02.07 ROBERT BOSCH GMBH
  • EP3837950B1 patent drawingFigure 1
  • EP3837950B1 patent drawingFigure 2
  • EP3837950B1 patent drawingFigure 3

AI summary

The invention relates to a lawnmower (11), in particular an autonomous lawnmower (11), comprising at least a chassis (45), a motor (15) for driving a cutting device (200) and a height adjustment device (16) for repositioning the cutting device (200) and the motor (15), in particular a motor housing (36) accommodating the motor (15), relative to the chassis (45), at least for adjusting a working height (h) of the cutting device (200) relative to the chassis (45), in particular for adjusting a cutting height (s) of a cutting tool (18) of the cutting device (200).It is proposed that the lawnmower (11) comprises a guide device (19) designed separately from the chassis (45) which has at least one guide element (20) which is designed with respect to a height adjustment axis (590) of the height adjustment device (16) for at least rotationally inhibiting axial guidance of a sliding seat (204) and for at least axially inhibiting rotational guidance of a rotating body (118) of the height adjustment device (16).