Off-Axis Motor Bracket for Compact Robot Lawnmower

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Solution Overview

Problem

Existing robot lawnmowers with in-axis driving motors require a longer length or reduced cutting deck size to accommodate the motors, compromising cutting efficiency and increasing volume.

Innovation Solution

A robot lawnmower design featuring off-axis driving motors, where each motor is fixed to a bracket that allows the motor to be positioned above the base frame, enabling a centered cutting deck and optimal weight distribution without increasing the machine's volume.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If in-axis driving motors are used, then the motor can be directly coupled to the driving wheel, but the cutting deck must be moved forwards increasing the length of the robot lawnmower

Engineering Contradiction:
Improvemotor coupling complexityVSAvoidlength of robot lawnmower
Core Design Contradiction:
Device complexityVSLength of moving object

Solution Approach 1:

The motor is repositioned from an in-axis configuration to an off-axis configuration, utilizing the vertical dimension above the base frame. The motor is mounted on a bracket positioned above the base frame, with its rotation axis displaced laterally from the driving wheel's rotation axis, thereby eliminating the need to extend the cutting deck forward while maintaining direct coupling capability through the bracket structure

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

2Device complexity

If the robot lawnmower is widened to accommodate in-axis motors, then the motors can be mounted, but the cutting deck size must be reduced decreasing cutting efficiency

Engineering Contradiction:
Improvemotor mounting structureVSAvoidcutting efficiency
Core Design Contradiction:
Device complexityVSProductivity

Solution Approach 1:

Instead of widening the robot lawnmower horizontally to accommodate in-axis motors, the design utilizes the vertical dimension by mounting the motor above the base frame on a bracket. This vertical displacement allows the motor to be positioned off-axis laterally, maintaining full cutting deck size and cutting efficiency while providing adequate space for motor mounting and operation

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

3Length of moving object

If off-axis motors are used, then the longitudinal size is reduced and cutting deck can be centered, but the motor position relative to driving wheel is displaced

Engineering Contradiction:
Improvelongitudinal size of robot lawnmowerVSAvoidmotor positioning structure
Core Design Contradiction:
Length of moving objectVSDevice complexity

Solution Approach 1:

The bracket structure serves multiple functions simultaneously: it mounts the motor above the base frame, positions the motor's rotation axis laterally offset from the driving wheel's axis, and provides the mechanical connection between the motor and driving wheel. This merged structure eliminates the need for separate positioning components while achieving the off-axis configuration that reduces longitudinal size and centers the cutting deck

Inventive Principle:
Principle #5Merging (Combining)

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 off-axis motor configuration allows for a robot lawnmower with reduced longitudinal size, maintaining cutting deck size and efficiency while minimizing the overall volume, with simple and easily maintainable mechanical connections.

Implementation Method 1

Each driving wheel 3 is driven by a respective electric motor 5 by means of a pinion 51 which meshes with a crown gear 32 of the driving wheel 3

Methodology Applied
Scientific EffectGear mechanism: Gear

Data Source

PatentEP4260676B1Robot lawnmower with off-axis driving motor
Publication Date: 2025.04.23 STIGA S P A IN BREVE ANCHE ST SPA
  • EP4260676B1 patent drawingFigure 1~2
  • EP4260676B1 patent drawingFigure 3~5

AI summary

There is described a robot lawnmower (1) comprising a base frame (2), two driving wheels (3) and at least one directional idler wheel (4), wherein each driving wheel (3) is driven by a respective electric motor (5). Each motor (5) comprises a pinion (51) which engages a crown gear (32) of the driving wheel (3). The motor (5) is fixed to a bracket (7) to which the driving wheel (3) is rotatably fixed. The rotation axis (X1) of the pinion (51) is parallel to the rotation axis (X2) of the driving wheel (3) but distinct therefrom, the motor (5) being off-axis with respect to the driving wheel (3). (Fig. 1).