Brush Cutter String Locking Head Ratchet Mechanism

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Solution Overview

Problem

Existing locking elements for cutting strings in spinning-string implements, such as mowers and trimmers, are costly and difficult to use due to the need for gloves to replace strings, and they fail to effectively lock toothed cutting strings.

Innovation Solution

A cutting head with a ratchet wheel and cam pin mechanism that allows easy string insertion and secure locking, using a toothed wheel with complementary teeth shapes and a return spring to maintain the string in place, accommodating both smooth and toothed strings.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a moving locking element with teeth is used to anchor the cutting string, then the locking effect is improved for smooth strings, but it becomes inoperative for toothed cutting strings

Engineering Contradiction:

Improvelocking effectVSAvoidcompatibility with different string types

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

Instead of using protruding teeth on the locking element to engage with the string (conventional approach), the invention uses recesses in the locking element that receive protrusions on the string. This inversion allows the locking mechanism to effectively engage with both smooth and toothed strings by adapting to their respective geometries.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The locking element features multiple recesses with varying geometries and orientations arranged in a circular pattern. By changing the parameters of these recesses (shape, size, orientation), the system can accommodate different string types and configurations, achieving both reliability and versatility.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If metallic eyelets with passageways are used to hold the cutting string, then the string can be secured to the head, but the production cost increases and string replacement becomes difficult when wearing gloves

Engineering Contradiction:

Improvestring retentionVSAvoidproduction cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The invention extracts the complex metallic eyelet component and replaces it with a simplified locking element made of plastic or composite material. This extraction eliminates the need for expensive metallic components while maintaining the essential function of string retention through the recess-based locking mechanism.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The locking element is designed as a low-cost, disposable component that can be easily manufactured from plastic or composite materials. Instead of using expensive metallic eyelets that require precision machining, the invention employs inexpensive molded parts that achieve the same functional outcome at lower production cost.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Reliability

If a cam with spring and teeth is used as a locking element, then the locking effect is improved, but the device complexity increases

Engineering Contradiction:

Improvelocking effectVSAvoidlocking mechanism complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The invention merges the functions of the cam, spring, and teeth into a single integrated locking element. Instead of having separate components that work together, the recess-based locking mechanism combines these functions into one piece, reducing device complexity while maintaining the locking effect through the geometric design of the recesses.

Inventive Principle:

Principle #5Merging (Combining)

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

The solution provides a cost-effective and user-friendly locking system that securely holds both smooth and toothed cutting strings, improving usability and reducing production costs.

Implementation Method 1

The ratchet further cooperates with a return spring of the cam pin to maintain the cam pin between two successive teeth of the toothed wheel

Methodology Applied

Scientific EffectElasticity: Elasticity

Implementation Method 2

The locking element includes at least one ratchet wheel including a toothed wheel mounted in rotation around an axis in such a manner that said teeth project in the passageway

Methodology Applied

Scientific EffectRatchet mechanism: Ratchet

Data Source

PatentUS8028424B2Cutting head for a brush cutter, edge trimmer or similar

Publication Date: 2011.10.04 SPEED FRANCE SAS

AI summary

The invention relates to a cutting head for a brush cutter, edge trimmer or similar, the head being of the type including at least a passageway for a cutting string and a locking element of the cutting string. The cutting head is characterized in that the locking elements include at least one ratchet wheel, including a toothed wheel mounted in rotation around an axis in such a manner that said teeth project in the passageway. The ratchet can be arranged in such a way that the toothed wheel can turn in a given direction to allow the introduction of the cutting string in the passageway and cannot turn in the opposite direction, thereby locking the cutting string in the passageway.