Curved Mower Blade Aerodynamic Thrust for Variable Cutting Height
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Solution Overview
Problem
Current cordless electric lawn mowers face inefficiencies in cutting tall grass due to increased load resistance, leading to decreased blade RPM, poor cut quality, and motor stall, resulting in labor and equipment costs, as well as shortened component life.
Innovation Solution
The mower configuration utilizes thrust-based forces from aerodynamic mower blade surfaces to achieve continuously variable cutting height, with mechanical springs dampening the motion to maintain optimal RPM and prevent motor stall, allowing for top-down mulching and efficient grass cutting across varying terrain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the mower blade rotates at high RPM to cut tall grass efficiently, then cutting quality improves, but motor load increases causing overheating and stall
Solution Approach 1:
The blade pitch angle is made dynamically adjustable during operation. The system transitions from a fixed-pitch blade to one that can change its aerodynamic characteristics in real-time, allowing the blade to operate at optimal angles for different grass conditions while maintaining stable motor loads
Solution Approach 2:
The invention changes the aerodynamic parameters of the blade by adjusting pitch angle. This parameter change allows the blade to maintain efficient cutting performance across varying grass heights and densities without causing motor overload, as the adjustable pitch optimizes the load characteristics
2Reliability
If mechanical springs are added to dampen blade motion, then motor stall is prevented, but device complexity increases
Solution Approach 1:
Mechanical springs are introduced as counterbalancing elements that provide damping forces opposite to the blade's inertial and aerodynamic forces. These springs act as anti-weight mechanisms that prevent excessive downward motion and motor stall, while being integrated into the existing blade assembly structure
Solution Approach 2:
The mechanical springs provide beforehand cushioning by being pre-loaded and positioned to dampen blade motion before motor stall can occur. The springs are configured to engage and provide protective damping during normal operation, preventing the harmful effects of excessive blade descent
3Productivity
If battery power is increased to maintain RPM under load, then cutting performance is maintained, but battery weight and cost increase
Solution Approach 1:
The system uses itself to solve the power problem by harvesting aerodynamic energy from the blade motion. The variable pitch mechanism and mechanical springs work together to convert aerodynamic forces into useful work, reducing the burden on the battery and allowing smaller, lighter power sources to maintain cutting performance
Solution Approach 2:
The invention utilizes aerodynamic forces (a form of pneumatic energy) generated by the rotating blade to assist in the cutting process. By optimizing blade pitch to maximize aerodynamic efficiency, the system harvests energy from air flow to supplement battery power, reducing the required battery capacity and weight
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
This solution enables efficient cutting of tall grass with minimal strain on electrical components, reducing re-mowing needs, extending component life, and optimizing battery life, while providing stable and high-quality cutting performance across different grass heights and terrains.
Implementation Method 1
thrust derived from aerodynamic surfaces of curved mower blades that causes force vectors in the z-axis with resulting up and down motion of the motor/blade assembly
Implementation Method 2
mechanical springs (including spring washers, torsion springs, shock absorbers, elastic materials exhibiting spring-like behavior, etc.) to oppose the thrust-based force vectors as a dampener to limit motor/blade assembly vertical range of motion
Data Source
AI summary
A vegetation cutting device comprises at least one motor/blade assembly comprising a motor and a blade supported for rotational movement in relation to the motor. The blade is curved to provide airflow thrust to produce at least one of vertical or orbital motion of the blade.