Blade Assembly with Inclined Slot and Torsion Spring for Impact Absorption
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Solution Overview
Problem
Existing grass cutting mobile robots face challenges in safely navigating around obstacles without damaging their blades or actuators, as they are prone to high impulse forces upon contact with non-mowable objects, leading to potential mechanical failure and inefficient cutting performance.
Innovation Solution
The blade assembly is designed with a torsion spring mechanism that allows blades to rotate and retract relative to the housing, reducing impulse forces through longer contact times and providing a biasing force against impact, along with a retention mechanism for easy attachment and detachment, enabling the robot to maneuver around objects by changing the blade's radius and height.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the blade assembly uses a fixed rigid blade structure, then the cutting performance is stable, but the impulse force upon contact with obstacles causes mechanical failure
Solution Approach 1:
The blade is designed to be movable relative to the housing, allowing it to dynamically adjust its position upon contact with obstacles. The blade can rotate about a mounting axis and move along an inclined slot, transforming from a static rigid structure to a dynamic system that absorbs impact forces through controlled motion rather than rigid resistance.
Solution Approach 2:
A spring mechanism is incorporated to provide beforehand cushioning for the blade. The spring absorbs and attenuates impact forces before they are transmitted to the housing and actuator, reducing peak impulse forces and preventing mechanical failure while maintaining reliable operation.
2Reliability
If the blade assembly allows blade movement to reduce impulse forces, then the reliability improves, but the device complexity increases
Solution Approach 1:
The blade assembly is segmented into independent functional components: the blade itself, the mounting mechanism allowing rotation about an axis, the inclined slot guiding blade movement, and the spring cushioning system. This segmentation allows each component to perform its specific function while maintaining overall system reliability without excessive complexity.
Solution Approach 2:
The system changes the operational parameters of the blade from fixed position to variable position along an inclined slot. The blade's radial position and height above ground can be adjusted through the slot mechanism, allowing the system to adapt to different cutting conditions and obstacle encounters without requiring a completely complex reconfigurable structure.
3Adaptability or versatility
If the blade tip radius is reduced upon impact, then the ability to maneuver around objects improves, but the cutting radius changes affecting cutting performance
Solution Approach 1:
The blade tip radius is made dynamic rather than fixed. Upon impact with obstacles, the blade automatically retracts along the inclined slot, reducing its effective radius and allowing the robot to maneuver around objects. Once the obstacle is cleared, the spring mechanism returns the blade to its original extended position, restoring the full cutting radius and efficiency.
Solution Approach 2:
The blade undergoes periodic cycles of extension for cutting and retraction for obstacle avoidance. This periodic action between extended cutting position and retracted navigation position allows the system to maintain both high cutting productivity during normal operation and adaptability when obstacles are encountered, with the blade automatically returning to its cutting position after each impact event.
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 reduces the risk of blade and actuator damage, enhances the robot's ability to navigate around objects of varying geometries, and improves cutting efficiency by distributing the force over a longer duration, allowing for more effective grass cutting while minimizing mechanical failure.
Implementation Method 1
The spring can be a torsion spring having a first end coupled to the housing and a second end coupled to the blade. The torsion spring can have a twist axis. The blade can be configured to rotate relative to the housing about a mounting axis coincident with the twist axis and non-parallel to the drive axis.
Implementation Method 2
In response to the impact and movement of the blade, the tip radius can be reduced toward a second radius. The second radius can be less than the first radius.
Data Source
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AI summary
A grass cutting mobile robot includes a body and a blade assembly connected to the body and rotatable about a drive axis. The blade assembly includes blades, a housing to hold the blades, and a spring that connects the blade to the housing. The housing includes a slot in which to mount a blade so that a portion of the blade is movable through the slot towards another blade in response to an impact. The slot slopes upwards in the housing towards the body, thereby enabling the blade to move upwards relative to a ground surface toward the body in response to the impact. The spring is for constraining movement of the blade relative to the housing.