Offset Robotic Lawnmower Blade for Low-Cut, Low-Friction Mowing

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Solution Overview

Problem

Existing robotic lawnmowers face challenges such as high energy consumption, limited area coverage, and a tendency to get stuck in uneven terrain, particularly when cutting short grass.

Innovation Solution

A robotic lawnmower cutting arrangement that raises the blade carrier above the grass, reducing friction and power consumption, while allowing for cutting to a low height without a free-rotating lower plate, and incorporating an offset blade pivot axis to minimize sticking risks.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If a free-rotating lower plate is used between the grass surface and the rotating blade carrier disc, then friction against the grass is reduced, but the device complexity increases and the cutting height cannot be lowered sufficiently

Engineering Contradiction:

Improvepower consumptionVSAvoidcutting arrangement complexity

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The patent removes the free-rotating lower plate from the cutting arrangement, extracting the element that caused both energy loss through friction and device complexity. Instead, it uses a blade design with offset pivot axis that achieves low cutting height without requiring the lower plate, thereby reducing both complexity and energy consumption.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

Rather than using a lower plate to reduce friction, the invention inverts the approach by raising the blade carrier above the grass surface and using an offset blade pivot axis arrangement. This reversal eliminates the need for the lower plate while achieving the same friction reduction goal and enabling lower cutting heights.

Inventive Principle:

Principle #13The other way round (Inversion)

2Loss of energy

If the blade carrier is raised above the grass to reduce friction, then power consumption is reduced, but the ability to cut short grass is compromised

Engineering Contradiction:

Improvepower consumptionVSAvoidcutting height precision

Core Design Contradiction:

Loss of energyVSManufacturing precision

Solution Approach 1:

The patent introduces asymmetry through the offset blade pivot axis, where the pivot axis is positioned radially offset from the blade carrier rotation axis. This asymmetric arrangement allows the blade to achieve low cutting height while the blade carrier remains raised, simultaneously reducing friction and enabling precise short grass cutting.

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The invention adds a radial dimension to the blade positioning through the offset pivot axis. By offsetting the pivot axis radially from the rotation axis, the blade can reach lower cutting heights while the blade carrier operates at a higher position, effectively using a second dimension (radial offset) to solve the height conflict.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Manufacturing precision

If the robotic lawnmower operates on already-cut grass multiple times to achieve desired cutting quality, then cutting evenness is improved, but energy consumption increases

Engineering Contradiction:

Improvecutting qualityVSAvoidenergy consumption

Core Design Contradiction:

Manufacturing precisionVSUse of energy by moving object

Solution Approach 1:

The offset blade pivot axis arrangement performs preliminary action by pre-positioning the blade at an optimal cutting angle and height before contact with the grass. This preliminary geometric arrangement improves cutting efficiency in a single pass, reducing the need for multiple re-cuts and thereby lowering energy consumption while maintaining cutting quality.

Inventive Principle:

Principle #10Preliminary action

4Loss of energy

If the blade carrier disc's rotation axis is inclined forward to prevent blades from touching grass at the rear, then energy is saved, but the cutting arrangement cannot achieve low cutting heights

Engineering Contradiction:

Improveenergy consumptionVSAvoidcutting height

Core Design Contradiction:

Loss of energyVSManufacturing precision

Solution Approach 1:

The offset blade pivot axis arrangement acts as a counterbalancing mechanism that compensates for the blade carrier being raised above the grass. The radial offset creates a geometric counterweight effect that allows the blade to reach low cutting heights while the blade carrier remains elevated, eliminating the need for forward inclination and its associated energy savings.

Inventive Principle:

Principle #8Anti-weight (Counterweight)

Data Source

PatentEP3820272B1Robotic lawnmower cutting arrangement, robotic lawnmower, cutting blade, and methods

Publication Date: 2025.04.30 HUSQVARNA AB

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AI summary

A robotic lawnmower comprises a blade carrier (200) and a cutting blade (400) pivotally connected thereto, the blade comprising a substantially flat cutting portion (401) extending along a cutting portion plane (410), a blade carrier interface (404), and an offset portion (406) interconnecting the cutting portion (401) and the blade carrier interface (404). When operating the robotic lawnmower, the blade carrier interface (404) of the cutting blade (400) follows a circular path in a blade carrier interface rotation plane (415), and the cutting portion (401) follows a circular path in a cutting plane (402), offset from the blade carrier interface rotation plane (415) by a cutting plane offset distance (408).