Multi-mode Trimmer Head with Dual Aperture Spool

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Solution Overview

Problem

Existing trimmer heads for string trimmers and brush cutters are typically limited to either a fixed-line or bump-feed operating mode, lacking a multi-mode capability that can seamlessly switch between these modes without disassembly or additional components.

Innovation Solution

A multi-mode trimmer head design featuring an upper and lower housing with a spool and bump head, allowing for both flexible and fixed-line trimmer line operation by utilizing separate sets of apertures and a spring mechanism to switch between modes without disassembly, enabling operation in either bump-feed or fixed-line mode, or both simultaneously.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a trimmer head is designed as a single-type (either fixed-line or bump-head), then the structure is simple and easy to manufacture, but the adaptability is limited and cannot switch between operating modes

Engineering Contradiction:

Improveoperating mode versatilityVSAvoidtrimmer head structure

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The spool is divided into distinct functional zones with separate aperture sets: a first set of apertures for bump-feed mode and a second set for fixed-line mode. This segmentation allows the single spool to support multiple operating modes by selecting which aperture set receives the trimmer line, thereby improving adaptability without requiring multiple separate trimmer heads

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The spool is designed with dual functionality by incorporating both a first set of apertures and a second set of apertures, enabling it to serve both bump-feed and fixed-line operating modes. This multi-functionality allows a single trimmer head design to replace what would traditionally require two separate trimmer heads, improving versatility while maintaining reasonable structural complexity

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Duration of action of stationary object

If a thicker, more rigid trimmer line is used for extended use, then the durability is improved, but the flexibility is reduced making it unsuitable for bump-feed mode

Engineering Contradiction:

Improvetrimmer line durabilityVSAvoidoperating mode compatibility

Core Design Contradiction:

Duration of action of stationary objectVSAdaptability or versatility

Solution Approach 1:

The trimmer line is selected to have different properties depending on the operating mode: for the first set of apertures (bump-feed mode), a thinner, more flexible trimmer line is used that can bend and feed properly; for the second set of apertures (fixed-line mode), a thicker, more rigid trimmer line is used that provides durability for extended use. This local quality differentiation allows the system to optimize line properties for each specific mode without compromising overall versatility

Inventive Principle:

Principle #3Local quality

3Adaptability or versatility

If a thinner, more flexible trimmer line is used for bump-feed mode, then the adaptability is improved, but the strength is reduced causing frequent breaks

Engineering Contradiction:

Improvebump-feed mode compatibilityVSAvoidtrimmer line strength

Core Design Contradiction:

Adaptability or versatilityVSStrength

Solution Approach 1:

The system applies local quality by matching trimmer line properties to specific operating modes: thinner, more flexible line for bump-feed mode (first set of apertures) where flexibility is critical, and thicker, stronger line for fixed-line mode (second set of apertures) where strength is critical. This resolves the contradiction by allowing each mode to use optimally suited line properties

Inventive Principle:

Principle #3Local quality

4Reliability

If separate trimmer heads are used for fixed-line and bump-feed modes, then the specialization is improved, but the device complexity and maintenance time increase

Engineering Contradiction:

Improvemode-specific performanceVSAvoidmaintenance time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The invention merges the functionality of separate fixed-line and bump-head trimmer heads into a single unified spool design. By incorporating both a first set of apertures for bump-feed mode and a second set of apertures for fixed-line mode within one spool, the system eliminates the need to own and switch between multiple specialized trimmer heads, thereby reducing maintenance time and operational complexity while maintaining mode-specific performance

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The spool is designed as a universal component that can accommodate both bump-feed and fixed-line operating modes through its dual aperture sets. This multi-functionality allows a single trimmer head to replace multiple specialized heads, reducing the time and effort required for maintenance and switching between modes

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS10517210B2Multi-mode trimmer head

Publication Date: 2019.12.31 MTD PRODUCTS INC

AI summary

A multi-mode trimmer head for use with an outdoor handheld tool such as a string trimmer, brush cutter, or the like is provided. The trimmer head includes an upper housing, lower housing, bump head, spool, and a spring. The spool includes a first pair of apertures configured to receive a pair of flexible trimmer lines to provide a bump-feed operating mode for the trimmer head. The spool also includes a separate, second pair of apertures configured to receive a single fixed-line trimmer line to provide a fixed-line operating mode for the trimmer head. The trimmer head is switchable between the fixed-line operating mode and the bump-feed operating mode without the need to disassemble the trimmer head.