String Trimmer Arm Rest and Airflow Layout for Wear and Heat

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Solution Overview

Problem

Existing string trimmers cause user fatigue due to weight and require lifting to a certain height, leading to the trimmer head touching the ground, which accelerates wear and affects heat dissipation efficiency.

Innovation Solution

The string trimmer features an arm rest with a deformable pad for user comfort, an automatic line release mechanism, and improved heat dissipation through a dedicated air path and air inlet, along with an anti-wear cover to prevent ground contact.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the string trimmer head is lifted to a certain height to achieve effective trimming, then the trimming effectiveness is improved, but the user experiences increased fatigue during long-term operation

Engineering Contradiction:
Improvetrimming effectivenessVSAvoiduser fatigue
Core Design Contradiction:
ProductivityVSEase of operation

Solution Approach 1:

The patent introduces an arm rest structure that provides counterbalancing support to offset the weight of the string trimmer. The arm rest is positioned to leverage the user's arm as a fulcrum, creating a counterweight effect that reduces the effort required to hold and operate the trimmer at the required height, thereby reducing user fatigue while maintaining trimming effectiveness

Inventive Principle:
Principle #8Anti-weight (Counterweight)

2Ease of operation

If the string trimmer head touches the ground during operation, then the feeling of fatigue is reduced, but the wear of the string trimmer head is aggravated

Engineering Contradiction:
Improveuser fatigue reductionVSAvoidservice life of string trimmer
Core Design Contradiction:
Ease of operationVSReliability

Solution Approach 1:

The patent introduces an anti-wear cover as an intermediary component between the string trimmer head and the ground. This cover is made of wear-resistant material and is specifically positioned at the contact point with the ground, allowing the trimmer to be rested on the ground without the main trimmer head components experiencing direct wear, thus extending service life while maintaining ease of operation

Inventive Principle:
Principle #24Intermediary (Mediator)

3Productivity

If the string trimmer operates for extended periods, then productivity is improved, but heat dissipation efficiency becomes insufficient

Engineering Contradiction:
Improveworking efficiencyVSAvoidheat dissipation efficiency
Core Design Contradiction:
ProductivityVSTemperature

Solution Approach 1:

The patent segments the housing structure to create dedicated heat dissipation air paths. The housing is divided into regions that channel air flow specifically through areas where heat-generating components are located, ensuring efficient heat removal during extended operation periods and maintaining working efficiency without thermal overload

Inventive Principle:
Principle #1Segmentation

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

Reduces user fatigue, minimizes trimmer head wear, and enhances heat dissipation efficiency, allowing for more comfortable and efficient operation.

Implementation Method 1

a pad (136) that is squeezable to deform and restore

Methodology Applied
Scientific EffectCompression: Compression

Implementation Method 2

the pad (136) is squeezable to deform and restore

Methodology Applied
Scientific EffectElasticity: Elasticity

Implementation Method 3

improved heat dissipation through a dedicated air path and air inlet

Methodology Applied
Scientific EffectConvection: Convection

Data Source

PatentEP4282246B1Grass trimmer
Publication Date: 2026.02.04 NANJING CHERVON IND
  • EP4282246B1 patent drawingFigure 1
  • EP4282246B1 patent drawingFigure 2
  • EP4282246B1 patent drawingFigure 3

AI summary

Provided is a string trimmer including a string trimmer head; a drive device including a motor for driving the string trimmer head to rotate about a first axis; an operating device including a first housing for connecting a power supply device to supply power to the motor; and a connecting device for connecting the drive device to the operating device. The first housing is formed with an arm rest portion to be rested on, a coupling portion for coupling the power supply device, and a connecting portion connected to the connecting device; where the arm rest portion is disposed behind the connecting portion and configured to be squeezable by an arm when the string trimmer is operated; and an air inlet is disposed between the coupling portion and the connecting portion, where the air inlet communicates with the inside of the first housing. The string trimmer is comfortable to operate and has a long service life.