Electric Mower Blade Unblocking via Reverse Rotation
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Solution Overview
Problem
Electric lawn mowers face issues with blade jamming due to clumps of plants, which can slow down or block the cutting blades, requiring user intervention that is time-consuming and dangerous, especially since electric mowers lack a manual launcher to dislodge clumps.
Innovation Solution
An electric mower with a brushless motor and an electronic control unit that measures current in the motor windings to initiate a blade launch phase in the opposite direction of rotation to disengage the blade, allowing it to acquire speed and overcome blockages, and includes a method for automatic detection and unblocking of jammed blades.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If electric motor starting torque is used to overcome vegetation blockage, then blade rotation can be initiated, but the torque is insufficient to dislodge clumps of vegetation
Solution Approach 1:
The patent applies reverse rotation of the cutting blade to dislodge vegetation clumps. Instead of only rotating the blade in the forward cutting direction, the control unit commands the motor to rotate the blade in reverse direction for a predetermined time period when blockage is detected, creating opposing force that loosens and removes the clumps blocking the blade rotation.
Solution Approach 2:
The patent implements periodic alternating rotation of the cutting blade between forward and reverse directions. The control unit cycles the motor between forward rotation (for cutting) and reverse rotation (for unblocking), creating a periodic action that maintains continuous operation by intermittently clearing vegetation buildups that would otherwise cause sustained blockage.
2Productivity
If manual intervention is used to unblock blades, then vegetation clumps can be removed, but user safety is compromised and time is lost
Solution Approach 1:
The patent enables the lawnmower to automatically unblock its own cutting blade without user intervention. The control unit detects blade blockage through current sensing, automatically commands reverse rotation to dislodge clumps, and resumes forward rotation when unblocked, making the system self-servicing and eliminating the need for users to manually reach near rotating blades.
Solution Approach 2:
The patent replaces the mechanical manual unblocking system (where users physically remove clumps by hand) with an automated electromechanical system. The control unit uses electrical current sensing to detect blockage and automatically activates reverse motor rotation, substituting manual mechanical intervention with an automated sensor-actuator system that eliminates safety risks.
3Reliability
If cutting height is adjusted to avoid blade overload, then blade blockage can be prevented, but cutting uniformity deteriorates and additional passes are required
Solution Approach 1:
The patent dynamically adjusts the blade rotation direction based on real-time operating conditions rather than using a fixed cutting height. The control unit continuously monitors motor current to detect blockage conditions and dynamically switches between forward and reverse rotation, allowing the system to adapt to varying vegetation densities and maintain high cutting efficiency without compromising blade operation reliability.
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
Enables the electric mower to automatically release blades from clumps without user intervention, ensuring continuous operation and reducing the risk of accidents by using the motor's angular momentum to overcome blockages and maintain mowing efficiency.
Implementation Method 1
allowing it to acquire speed and overcome blockages, and includes a method for automatic detection and unblocking of jammed blades
Data Source
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AI summary
The invention concerns an electric mower comprising an electric motor driving at least one rotary cutting blade, and a method for controlling the mower comprising: - a rest phase (100) during which the electric motor is not powered; - a mowing phase (102) during which the electric motor is controlled to rotate in a first direction of rotation, corresponding to the rotation of the cutting blade in a plant cutting direction; - a temporary blade start phase (108), in which the electric motor is temporarily controlled to rotate in a second direction opposite the first direction of rotation. Applicable to mowers and brushcutter mowers.