Lawn Mower Lever Interlock for Two-Handed Blade Startup
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Solution Overview
Problem
Conventional lawn mowers, despite having safety features like blade guards, still pose a risk of severe hand injuries due to the operator's hands getting past the guards when starting the cutting blades, highlighting the need for improved safety systems.
Innovation Solution
An electric lawn mower design featuring a pivoting lever and a start switch that requires both hands to be occupied simultaneously, ensuring the cutting blades are engaged only when both hands are engaged with the lever and switch, thereby reducing the risk of injury.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional lawn mower safety features (blade guards) are used, then operator protection is improved, but hand injury risk remains because hands can get past the guards
Solution Approach 1:
The system performs preliminary safety checks before allowing blade operation. The pivoting lever must be positioned to a specific angle and the start switch must be activated before the blades can start, ensuring the operator's hands are in safe positions beforehand. This preliminary verification prevents hands from being in dangerous positions when blades are engaged.
Solution Approach 2:
The system provides feedback through the pivoting lever mechanism that only allows blade startup when the lever is in the correct position. The lever's position is continuously monitored and provides feedback to the control system, which only permits blade operation when safety conditions are met. This feedback loop ensures ongoing safety during operation.
2Object-affected harmful factors
If a pivoting lever and start switch system is implemented, then operator safety is improved by requiring both hands occupied, but device complexity increases
Solution Approach 1:
The system merges the safety lever mechanism with the existing blade startup control system. The pivoting lever is integrated into the handle assembly and its position is combined with the start switch activation requirement. This merging creates a unified safety control system that reduces overall complexity compared to having separate independent safety systems.
Solution Approach 2:
The pivoting lever serves multiple functions: it acts as a safety switch, a position indicator, and part of the handle assembly structure. The start switch system also serves dual purposes by requiring both lever positioning and switch activation. This multi-functionality reduces the number of separate components needed, thereby reducing overall device complexity.
Data Source
AI summary
An electric lawn mower including a pivoting lever coupled to a stationary handle, a start switch, a cutting blade, electric wheel motors, and a controller in communication with the pivoting lever and the start switch. The controller is configured to keep the cutting blade and the electric wheel motors off when the pivoting lever is disposed anywhere from a fully disengaged position up to and including a first pivot angle and the start switch has not been activated, keep the electric wheel motors off and turn the cutting blade on when the pivoting lever is disposed at a second pivot angle and the start switch is activated, and turn the electric wheel motors on when the pivoting lever is transitioned from the second pivot angle to a third pivot angle after the cutting blade has been turned on.