Lawn Mower Blade Holder Connecting Leg Impact Absorption
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Solution Overview
Problem
Conventional lawn mowers face issues with deformation and impact load transmission to the output shaft when the grass cutting blade hits obstacles, requiring the fracture of an impact absorbing member, which complicates maintenance.
Innovation Solution
A blade mounting structure with a connecting leg section that gradually decreases in wall thickness from the shaft-mounted section to the blade mounting section, acting as an impact absorbing member to distribute and absorb bending and twisting moments uniformly, preventing impact load transmission to the output shaft without fracturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a shear pin is used as an impact absorbing member, then the output shaft is protected from impact loads, but the shear pin fractures and drops to the ground requiring time-consuming retrieval
Solution Approach 1:
The invention extracts the impact absorption function from a separate shear pin component and integrates it into the connecting leg section of the blade holder structure. The connecting leg section itself is designed to deform under impact, eliminating the need for a separate fractureable component that would drop to the ground.
Solution Approach 2:
The invention merges the impact absorption function with the structural connecting leg section. The connecting leg section serves dual purposes: transmitting rotational force from the output shaft to the blade holder, and absorbing impact loads through controlled deformation, thereby eliminating the need for a separate shear pin component.
2Ease of manufacture
If the connecting leg section has uniform wall thickness, then manufacturing is simplified, but impact load causes concentrated stress leading to fracture
Solution Approach 1:
The connecting leg section features non-uniform wall thickness with local variations optimized for its function. The wall thickness is greater at the upper end portion near the output shaft where strength is needed, and gradually decreases toward the lower end portion, creating a stress distribution that prevents concentrated stress points and fracture while remaining manufacturable.
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 design allows for stable and efficient grass cutting by absorbing impact loads, preventing deformation and fracture, and facilitates easy disassembly and maintenance by maintaining a space for tool insertion.
Implementation Method 1
the connecting leg section having a wall thickness dimension gradually decreasing in a direction from the shaft-mounted section toward the blade mounting section... a yield point of the connecting leg section to the impact load (stress) can be made substantially uniform throughout an entire region from the upper end portion to the lower end portion
Data Source
AI summary
A blade mounting structure of a lawn mower includes a blade holder including a shaft-mounted section connected to an output shaft of an engine, and a blade mounting section having a grass cutting blade mounted thereto. The blade holder further includes a connecting leg section located between the shaft-mounted section and the blade mounting section and interconnecting the shaft-mounted section and the blade mounting section. The connecting leg section has a wall thickness dimension gradually decreasing in a direction from the shaft-mounted section toward the blade mounting section.