Trimmer Head Spool Core Axial Decoupling

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Solution Overview

Problem

Existing trimmer devices face difficulties in quickly and easily loading trimmer line, which frustrates users and complicates the replenishment process, affecting user experience.

Innovation Solution

A trimmer head design featuring a spool fixed against axial movement but capable of rotational movement, coupled with a core that can be 'bumped' to release line, allowing the core to move axially while the spool remains stationary, facilitating easy line loading and replenishment without disassembly.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If the spool is made movable in the axial direction to enable line release by bumping, then the ease of operation is improved, but the reliability deteriorates due to potential unwanted movement or misalignment

Engineering Contradiction:

Improveease of line releaseVSAvoidreliability of line feeding

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The spool assembly is segmented into two independent components: the spool itself (which rotates) and the core (which moves axially). This segmentation allows the spool to remain stationary in the axial direction while the core moves independently to release line, resolving the contradiction between ease of operation and reliability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Instead of making the spool movable axially to release line (conventional approach), the patent inverts the approach by making the core movable axially while the spool remains stationary. The core's axial movement drives line release without compromising spool alignment or stability.

Inventive Principle:

Principle #13The other way round (Inversion)

2Reliability

If the spool is fixed to prevent axial movement, then the reliability of line feeding is improved, but the ease of operation worsens due to inability to easily release line

Engineering Contradiction:

Improvereliability of line feedingVSAvoidease of line release

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The system is divided into the fixed spool (ensuring reliable line feeding) and the movable core (enabling easy line release). The spool remains stationary in the axial direction while the core can move independently, allowing line release without compromising feeding reliability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The core acts as an intermediary between the operator's bumping action and the spool's line feeding function. The core's axial movement transfers the bumping force to release line while the spool remains stationary, maintaining reliable line feeding.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Ease of operation

If a long line channel is provided through the core, then the ease of operation is improved by facilitating line loading, but the device complexity increases

Engineering Contradiction:

Improveease of line loadingVSAvoidcomplexity of core structure

Core Design Contradiction:

Ease of operationVSDevice complexity

Solution Approach 1:

The core is pre-configured with a long line channel that guides the line from the spool to the discharge point. This preliminary structural arrangement simplifies the line loading operation by providing a ready-made pathway, while the channel is integrated into the existing core structure to minimize added complexity.

Inventive Principle:

Principle #10Preliminary action

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

Enables quick and easy loading of trimmer line, improving user experience by simplifying the replenishment process and reducing operational complexity.

Implementation Method 1

The trimmer line, which may be a monofilament line, is quite effective at cutting when rotated at high speed. Such a trimmer line is extended and held somewhat rigid by centrifugal forces while being rotated.

Methodology Applied

Scientific EffectCentrifugal force: Centrifugal Force

Implementation Method 2

the core may be bumped to release line from the spool in a manner that permits the core to move in the axial (or vertical) direction, while the spool releases line but does not substantially move in the axial (or vertical direction)

Methodology Applied

Scientific EffectImpact force: Impact Force

Data Source

PatentEP2923549B1Quick loading trimmer head

Publication Date: 2018.01.10 HUSQVARNA AB

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AI summary

A trimmer head (25) for a hand-held cutting device (10) may include a first housing portion (100), a line holding assembly (110, 110') to hold and selectively release trimmer line (70), and a second housing portion (120) operably coupled to the first housing portion (100) to house the line holding assembly (110, 110'). The line holding assembly (110, 110') may include a spool (130, 130') configured to hold the trimmer line (70) and a core (140, 140') operably coupled to the spool (130, 130'). The line holding assembly (110, 110') may be configured such that rotational movement of the core (140, 140') causes corresponding movement of the spool (130, 130'), but movement of the core (140, 140') in an axial direction does not cause corresponding movement of the spool (130, 130').