Multi-zone Line Blade Drag Reduction for Cordless Trimmers
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Solution Overview
Problem
Current line blades for cordless trimmers suffer from high drag, flapping, twisting resonance, and energy inefficiencies, leading to poor cutting performance, noise, and reduced battery life, making them less effective compared to gas trimmers.
Innovation Solution
A multi-zone flexible line blade design with specific geometries for each zone, featuring a transition section with a blunt leading edge and a sharp trailing edge, and a cutting segment with a sharp leading edge, optimized to reduce drag, flapping, and twisting resonance, while creating an updraft for improved cutting efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional monofilament line or inefficient line blades are used, then cutting capability is limited, but drag and power consumption are high
Solution Approach 1:
The line blade is divided into multiple zones with different cross-sectional geometries: a leading zone with a first cross-section, a transition zone with a second cross-section, and a cutting zone with a third cross-section. This segmentation allows each zone to perform its specific function optimally while reducing overall drag
Solution Approach 2:
Different zones of the line blade are given different local geometries tailored to their specific functions. The leading zone has geometry optimized for aerodynamic entry, the transition zone for smooth flow transformation, and the cutting zone for sharp vegetation cutting. This local optimization reduces energy loss while maintaining cutting effectiveness
2Productivity
If line blade orientation is pitched to create lift-induced updraft for grass lift, then cutting assistance is improved, but drag increases
Solution Approach 1:
The pitch angle of the line blade is optimized to create beneficial lift-induced updraft that assists grass lift during cutting. The multi-zone geometry allows the blade to maintain this angle while reducing drag through the streamlined cross-sectional transitions, balancing cutting assistance with energy efficiency
3Productivity
If a sharper leading edge is used on the line blade, then cutting performance is improved, but aerodynamic stability deteriorates due to vulnerability to aerodynamic and aeroelastic forces
Solution Approach 1:
The line blade is divided into a leading zone with a more bluff cross-section that provides aerodynamic stability, a transition zone, and a cutting zone with the sharp edge needed for cutting performance. This segmentation allows the stable leading portion to handle aerodynamic forces while the cutting portion delivers sharp cutting action
Solution Approach 2:
The leading zone is given a cross-section with greater bluffness to resist aerodynamic and aeroelastic forces, while the cutting zone maintains a sharp edge geometry for high cutting performance. Each zone's local geometry is optimized for its specific functional requirement
4Duration of action of moving object
If conventional line blade designs are used in cordless trimmers, then battery life is reduced due to high drag, but cutting performance must be maintained
Solution Approach 1:
The multi-zone segmented design reduces drag through streamlined cross-sectional transitions while maintaining cutting effectiveness in the cutting zone. This allows cordless trimmers to operate longer on battery power without sacrificing cutting performance
Solution Approach 2:
The optimized cross-sectional geometries and their transitions reduce aerodynamic drag, allowing the line blade to cut effectively at lower speeds and reducing power consumption, thereby extending battery life in cordless trimmer applications
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 design results in significantly reduced drag, noise, and power consumption, enabling more efficient cutting with longer battery life, improved cutting quality, and increased cutting rates, making cordless trimmers more competitive with gas trimmers.
Implementation Method 1
the line blade orientation can be pitched to create lift-induced updraft that assists with grass lift in the rotary mowing process
Implementation Method 2
The improvements to the flexible line blade cutting system offered with the line blades according to the described embodiments will make both gas and electric grass trimmers more useful, energy-efficient, and productive cutting performers characterized by improved lower cost economies
Implementation Method 3
there are numerous tradeoff problems with existing line blades associated with high drag, flapping, twist resonance, and other grass cutting characteristics
Data Source
Figure 1
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Figure 4
AI summary
A line blade (10) for a rotating trimmer includes a loading section (14) securable for rotation on a cutting plane with a head of the rotating trimmer. A living hinge (16) extends from the loading section (14). A transition section (18) extends from the living hinge (16) and has a first cross-sectional shape. The first cross-sectional shape is configured and oriented to reduce drag. A cutting segment (24) extending from the transition section (18) has a second cross-sectional shape that is different from the first cross-sectional shape of the transition section (18), where the second cross-sectional shape is configured and oriented for cutting vegetation. The multi-zone line blade improves cutting at lower speeds, thereby requiring less power.