Trimmer Head Centrifugal Line Feed Mechanism

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Solution Overview

Problem

Existing electric trimmer designs face challenges in feeding trimmer line automatically while maintaining a low cutting height and avoiding circular marks, as traditional push-button mechanisms protrude and require manual 'bumping', which is unsuitable for precise trimming and can cause unwanted marks.

Innovation Solution

The trimmer head incorporates a mechanism where the rotation speed of the trimmer head is controlled to cause a relative movement between the inner body and housing, using centrifugal force to feed the trimmer line automatically, allowing for automated line feeding without manual intervention and reducing the risk of circular marks.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Extent of automation

If a push button mechanism is used for feeding trimmer line, then automated line feeding is achieved, but the cutting height increases and circular marks are formed in the grass

Engineering Contradiction:

Improveautomated line feedingVSAvoidcutting height

Core Design Contradiction:

Extent of automationVSLength of stationary object

Solution Approach 1:

The patent removes the protruding push button from the trimmer head exterior and integrates the line feeding mechanism internally. The feed button is positioned on the upper side of the housing rather than protruding downward, eliminating the interference with low cutting height requirements while maintaining automated line feeding capability.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

Instead of having the push button protrude downward to contact the ground for bump-feeding, the patent inverts the approach by placing the feed button on the upper side of the housing. This allows the user to press the button from above without requiring the trimmer head to be bumped against the ground, thus preventing circular marks while achieving automated feeding.

Inventive Principle:

Principle #13The other way round (Inversion)

2Extent of automation

If a push button protrudes from the trimmer head for line feeding, then automated line feeding is enabled, but precise trimming is compromised due to increased cutting height

Engineering Contradiction:

Improveautomated line feedingVSAvoidtrimming precision

Core Design Contradiction:

Extent of automationVSManufacturing precision

Solution Approach 1:

The patent extracts the feed button from the lower protruding position and relocates it to the upper side of the housing. This repositioning eliminates the interference with precise trimming operations while preserving the automated line feeding function, allowing the trimmer head to maintain low cutting height for accurate edging and detailing work.

Inventive Principle:

Principle #2Taking out (Extraction)

3Ease of operation

If manual bumping action is used to feed trimmer line, then line feeding is achieved, but unwanted circular marks are formed in the grass

Engineering Contradiction:

Improveline feeding operationVSAvoidcircular marks in grass

Core Design Contradiction:

Ease of operationVSObject-generated harmful factors

Solution Approach 1:

The patent enables the trimmer to feed line automatically through an electronically controlled mechanism activated by a feed button on the upper housing. This self-service automated feeding system eliminates the need for manual bumping operations, thereby preventing circular marks from being imprinted on the grass while maintaining ease of operation through simple button activation.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The patent replaces the mechanical bump-feeding system with an electronic control system that actuates the line feeding mechanism through a button press. This substitution eliminates the need for physical contact between the trimmer head and ground, preventing circular marks while achieving automated line feeding through electronic actuation rather than mechanical impact.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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

This solution enables reduced cutting height and minimizes the formation of circular marks, providing an improved method for feeding trimmer line without the need for manual 'bumping', ensuring precise trimming and efficient line feeding.

Implementation Method 1

the rotation speed of the trimmer head is controlled to cause a relative movement between the inner body and housing, using centrifugal force to feed the trimmer line automatically

Methodology Applied

Scientific EffectCentrifugal force: Centrifugal Force

Data Source

PatentEP3358931B1Automatic line feed for trimmer

Publication Date: 2022.05.11 HUSQVARNA AB

Figure 1A~3
Figure 4A
Figure 4B~5

AI summary

A trimmer head (1) arranged to be driven to rotate a trimmer line (3), wherein the trimmer head comprises a housing (1a, 1b) and an inner body (1c) connected to a trimmer line spool (13, 39), the trimmer head being characterized in that the inner body is arranged to be movable relative the housing so that a trimmer line spooled around the trimmer line spool is released and to be pulled out by a centrifugal force caused by the rotation of the trimmer head, thereby allowing feed of the trimmer line. A trimmer (10) comprising a trimmer head according to above, wherein the trimmer further comprises drive means (2, 4) for driving the trimmer head to rotate and wherein the trimmer is arranged to cause a relative movement of the inner body relative the housing by changing the rotation speed of the trimmer head.