Offset Cutting Disc and Pivoting Guard for Border Mowing

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Solution Overview

Problem

Robotic lawn mowers have limited ability to cut grass close to objects and borders due to the cutting unit being hindered by the lawnmower body and wheels, resulting in uncut grass and potential safety hazards.

Innovation Solution

A robotic lawn mower with an offset rotatable grass cutting disc and a pivoting guard that adjusts its position based on the traveling direction, ensuring the cutting disc always faces the grass while maintaining protection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the cutting width is increased to improve mowing efficiency, then the productivity increases, but the maneuverability and ability to cut around obstacles deteriorates

Engineering Contradiction:
Improvemowing efficiencyVSAvoidmaneuverability
Core Design Contradiction:
ProductivityVSEase of operation

Solution Approach 1:

The cutting device is divided into multiple independently movable cutting units (first cutting unit, second cutting unit, third cutting unit) that can be positioned at different locations. This segmentation allows the mower to maintain a wide cutting width while maneuvering around obstacles by selectively positioning only the necessary cutting units in the cutting path, thus resolving the contradiction between productivity and maneuverability.

Inventive Principle:
Principle #1Segmentation

2Device complexity

If a fixed cutting width is used to simplify the device structure, then the device complexity is reduced, but the adaptability to different cutting widths and obstacles deteriorates

Engineering Contradiction:
Improvestructure simplicityVSAvoidcutting width adaptability
Core Design Contradiction:
Device complexityVSAdaptability or versatility

Solution Approach 1:

The cutting units are designed with movable positions along the traveling direction, allowing dynamic adjustment of the cutting width. The cutting units can be repositioned based on obstacle locations or desired cutting patterns, providing adaptability without requiring a completely complex reconfigurable structure. This resolves the contradiction by implementing minimal necessary complexity for maximum versatility.

Inventive Principle:
Principle #15Dynamics

3Productivity

If multiple cutting units are added to increase productivity, then the mowing efficiency improves, but the device complexity and cost increase

Engineering Contradiction:
Improvemowing efficiencyVSAvoidnumber of cutting units
Core Design Contradiction:
ProductivityVSDevice complexity

Solution Approach 1:

Multiple cutting units are designed with identical structures and functions, each capable of independent operation. This universality allows the system to maintain high productivity through parallel cutting while avoiding the complexity of designing and managing different types of cutting units. Each unit serves multiple purposes: cutting grass, being independently controllable, and contributing to overall system adaptability, thus resolving the contradiction between productivity and complexity.

Inventive Principle:
Principle #6Universality (Multi-functionality)

Data Source

PatentEP4451838B1A robotic lawn mower with enhanced cutting properties
Publication Date: 2026.04.29 HUSQVARNA AB
  • EP4451838B1 patent drawingFigure 1~2
  • EP4451838B1 patent drawingFigure 3
  • EP4451838B1 patent drawingFigure 4

AI summary

The present disclosure relates to a robotic lawn mower (1 ) comprising a body (3), at least two drive wheels (5a, 5b), a drive motor arrangement (7a, 7b) drivably connected to the drive wheels (5a, 5b), and at least one swivelable wheel (6) adapted to swivel around a swivel axis (ax1 ). The robotic lawn mower (1 ) further comprises a control unit (21 ), adapted to control the operation of the robotic lawn mower (1 ), and an offset rotatable grass cutting disc (12) having an offset rotation axis (ax2). The offset rotation axis (ax2) is arranged at a first distance (d1 ) from a longitudinal center plane (LCP) of the robotic lawnmower (1 ). The robotic lawnmower (1 ) comprises a guard (13) covering at least a portion of the offset rotatable grass cutting unit (12), where the guard (13) is attached to a pivot axle (ax3) and arranged to pivot with the pivot axle (ax3) in dependence of a travelling direction (D1, D2, D3) of the robotic lawn mower (1 ).