Grass Trimmer Axial Offset Cutting Head Ergonomics

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Solution Overview

Problem

Existing hand tools like grass trimmers and brush cutters often have a central cutting head alignment that limits versatility and comfort during horizontal cutting, as the cutting head is positioned directly in front of the user, making it difficult to cut along walls or hedges without straining.

Innovation Solution

The design features an axial offset between the central longitudinal axis and the rotational axis of the cutting tool, allowing the cutting head to be positioned laterally offset from the user. This is achieved by angling the main tube and spacer unit relative to the cutting head, enabling comfortable cutting along walls or hedges while maintaining a balanced and ergonomic grip.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If the cutting head is positioned directly in front of the user (central alignment), then the tool structure is simple and straightforward, but the user experiences strain and discomfort when cutting along walls or hedges

Engineering Contradiction:
Improveuser comfortVSAvoidtool structure
Core Design Contradiction:
Ease of operationVSDevice complexity

Solution Approach 1:

The cutting head is deliberately positioned asymmetrically relative to the user's body centerline, creating a lateral offset that enables comfortable cutting along walls and hedges. This asymmetric configuration resolves the contradiction by prioritizing operational comfort over symmetric simplicity.

Inventive Principle:
Principle #4Asymmetry

Solution Approach 2:

The invention introduces a lateral dimension (offset distance) to the traditional central alignment configuration. By positioning the cutting head at a lateral offset from the user's body centerline in addition to the longitudinal distance, the tool enables new cutting positions along vertical surfaces without increasing structural complexity.

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

2Adaptability or versatility

If the cutting head is positioned laterally offset from the user, then cutting along walls or hedges becomes comfortable, but the tool structure becomes more complex

Engineering Contradiction:
Improvecutting versatilityVSAvoidtool structure
Core Design Contradiction:
Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The asymmetric lateral offset configuration enables the cutting head to reach positions that are inaccessible with central alignment, significantly improving adaptability for cutting along walls, hedges, and other vertical surfaces.

Inventive Principle:
Principle #4Asymmetry

3Ease of operation

If the main tube is held transversely to the cutting direction, then cutting along walls becomes convenient, but the center of gravity shifts away from the user's body center

Engineering Contradiction:
Improvecutting convenienceVSAvoidcenter of gravity position
Core Design Contradiction:
Ease of operationVSStability of the object's composition

Solution Approach 1:

A counterweight is integrated into the tool structure to compensate for the lateral offset of the cutting head. This counterweight balances the center of gravity, ensuring that it remains positioned between the user's hands even when the main tube is held transversely, thereby maintaining both cutting convenience and operational stability.

Inventive Principle:
Principle #8Anti-weight (Counterweight)

Data Source

PatentEP3784017B1Hand-held power tool in the form of a grass trimmer or brushcutter
Publication Date: 2025.06.11 ROBERT BOSCH GMBH
  • EP3784017B1 patent drawingFigure 1
  • EP3784017B1 patent drawingFigure 2
  • EP3784017B1 patent drawingFigure 3

AI summary

The invention relates to a grass trimmer (10) or brushcutter, comprising a handle unit (12) and a treatment unit (38), connected to and mutually spaced relative to one another via a distance unit (32), the distance unit (32) having a center axis or longitudinal axis (100), and the treatment unit (38) having an axis of rotation (60) about which an insertion tool, in particular a cutting line (44) or a cutting blade can rotate. According to the invention, the center or longitudinal axis (100) and the axis of rotation (60) have an axial offset (93) in relation to each other and/or do not intersect, in at least a horizontal cross-sectional configuration (58, 400) of the grass trimmer (10) or brushcutter. Said center axis or longitudinal axis (100) extends at least substantially along a center line or center axis of the distance unit (32).