Brushcutter Cutting Head Snap Connection Design

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Solution Overview

Problem

Existing cutting heads for brush cutters have complex assembly processes due to multiple parts, making them difficult to assemble and disassemble, and prone to accidental separation during operation.

Innovation Solution

A cutting head design featuring a divided base body with a snap connection between the upper and lower base body parts, allowing for easy attachment to the brush cutter's output shaft and preventing accidental disassembly, utilizing a screw element for secure fastening and a snap connection that engages radially close to the axis of rotation to maintain alignment and stability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If multiple individual parts are used in the cutting head assembly, then the cutting head can be securely attached to the brushcutter, but the assembly and disassembly process becomes significantly more complex

Engineering Contradiction:
Improvesecure attachmentVSAvoidassembly complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The base body is divided into an upper base body part and a lower base body part that can be easily separated and reconnected via snap connection, simplifying the assembly process while maintaining secure attachment through the screw element

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The cutting tool is integrated between the upper and lower base body parts, forming a unified assembly that attaches to the brushcutter as a single unit, reducing the number of separate assembly steps required

Inventive Principle:
Principle #5Merging (Combining)

2Ease of operation

If a releasable snap connection is used to hold the base body parts together, then easy assembly and disassembly is enabled, but the connection might accidentally separate during operation

Engineering Contradiction:
Improveassembly easeVSAvoidconnection stability
Core Design Contradiction:
Ease of operationVSReliability

Solution Approach 1:

The snap connection provides easy assembly through a simple snap-fit mechanism, while the screw element adds a dynamic locking feature that prevents accidental separation during operation, allowing the connection to be both easy to assemble and reliable during use

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The snap connection is designed to preliminarily hold the base body parts together in the correct position, preparing the assembly for final secure fastening with the screw element, ensuring proper alignment before final attachment

Inventive Principle:
Principle #10Preliminary action

3Adaptability or versatility

If the snap connection is positioned close to the axis of rotation, then the cutting tool can pivot freely without interference, but the snap connection must withstand higher centrifugal forces

Engineering Contradiction:
Improvecutting tool pivoting rangeVSAvoidcentrifugal force on snap connection
Core Design Contradiction:
Adaptability or versatilityVSForce

Solution Approach 1:

The snap connection is designed to dynamically withstand centrifugal forces through its resilient gripping hook that can deflect and engage securely, while the screw element provides additional dynamic fastening that prevents separation under high centrifugal load

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The base body parts are made from plastic material that combines flexibility for snap connection engagement with sufficient strength to withstand centrifugal forces, creating a composite structure that balances pivoting freedom with connection durability

Inventive Principle:
Principle #40Composite materials

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

Simplifies the assembly and disassembly of the cutting head, ensures secure attachment to the brush cutter, and prevents accidental separation of parts during operation, while allowing for effective cutting of vegetation without interference from the snap connection.

Implementation Method 1

the gripping hook is preferably flexible in the direction radial to the axis of rotation. Once the upper and lower base body parts are sufficiently pushed together, the gripping hook of the snap connection engages behind the retaining contour

Methodology Applied
Scientific EffectElasticity: Elasticity

Implementation Method 2

During operation of the brushcutter, the gripping hook is pressed outwards against the retaining contour by centrifugal forces. As a result, the shape of the gripping hook, or rather its preload against the retaining contour, is maintained even over extended periods of use

Methodology Applied
Scientific EffectCentrifugal force: Centrifugal Force

Data Source

PatentEP3925427B1Cutting head for a motor strimmer
Publication Date: 2025.01.15 ANDREAS STIHL AG & CO KG
  • EP3925427B1 patent drawingFigure 1
  • EP3925427B1 patent drawingFigure 2~4
  • EP3925427B1 patent drawingFigure 5~7

AI summary

The invention relates to a cutting head for a brushcutter, wherein the cutting head comprises a split base body (11) with an upper base body part (12) and a lower base body part (13). A screw element (19) is arranged on the lower base body part (13). The screw element (19) serves for attachment to an output shaft (18) of a brushcutter. At least one receptacle (15) for attaching a cutting tool (14) is provided between the upper base body part (12) and the lower base body part (13). The base body (11) can be driven to rotate about its axis of rotation (17) during operation of a brushcutter. The upper base body part (12) and the lower base body part (13) are held relative to each other by means of a releasable snap connection (1).