Lawn Mower Blade Mounting Structure Impact Absorption
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Solution Overview
Problem
Conventional lawn mower blade mounting structures face challenges in absorbing impact loads from obstacles while maintaining easy centering of the grass cutting blade, as they often restrict movement of the friction member, leading to bending loads on the output shaft and increased assembly time.
Innovation Solution
A blade mounting structure featuring a drive hub with curved surfaces for slidable engagement with a friction member, allowing horizontal and vertical movement, and an energy absorbing member that maintains shape during normal operation but deforms under impact loads to absorb and redirect forces, ensuring accurate positioning and protection of the output shaft.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the friction member is constructed to slide relative to the drive hub in the vertical direction to release bending load, then the output shaft is protected from bending loads, but it becomes difficult to position the friction member and blade holder, increasing assembly time and labor
Solution Approach 1:
The blade holder is segmented into an upper blade holder and a lower blade holder that can move relative to each other vertically. This segmentation allows the lower blade holder to move independently to absorb impact loads while the upper blade holder remains positioned for easy assembly and blade attachment.
Solution Approach 2:
A positioning pin acts as an intermediary component that guides the movement of the lower blade holder and maintains proper positioning during assembly. The positioning pin ensures that the friction member and blade holder are easily centered while still allowing necessary vertical movement for impact absorption.
2Power
If the frictional surfaces are formed in convex and concave truncated cone shapes, then driving force transmission is achieved, but the friction member cannot slide in the vertical direction, causing bending loads on the output shaft when hitting obstacles
Solution Approach 1:
The blade holder is designed with dynamic movement capability in the vertical direction, allowing it to transition from a fixed position during normal operation to a movable position during impact. The lower blade holder can move vertically to absorb impact loads while the curved surfaces maintain driving force transmission through friction.
Solution Approach 2:
Different parts of the blade holder have different movement characteristics. The lower blade holder is designed to move vertically to absorb impacts, while the upper blade holder maintains a fixed position for stable blade attachment. This local differentiation allows both driving force transmission and impact protection.
3Reliability
If the friction member is allowed to move freely in vertical and horizontal directions, then impact loads are absorbed effectively, but positioning and centering the grass cutting blade becomes difficult
Solution Approach 1:
The blade holder is divided into upper and lower segments with different freedom of movement. The lower blade holder can move freely in vertical and horizontal directions to absorb impacts, while the upper blade holder provides a stable reference for blade centering and attachment.
Solution Approach 2:
Complex mechanical centering mechanisms are replaced with simple positioning pins and guide structures that automatically center the blade during assembly. The positioning pin guides the lower blade holder into proper position without requiring complex adjustment mechanisms.
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
The solution effectively absorbs impact loads in both horizontal and vertical directions, protects the output shaft from bending loads, and simplifies the centering process of the grass cutting blade, enhancing operational efficiency and safety.
Implementation Method 1
the friction member is pressed via a coned disk spring
Implementation Method 2
the frictional surface of the friction member is brought into contact with the frictional surface of the drive hub, so that driving force of the power source is transmitted
Implementation Method 3
the energy absorbing member is constructed to maintain its shape during normal operating condition but deform when a load exceeding a predetermined value acts on the energy absorbing member
Data Source
AI summary
A blade mounting structure of a lawn mower includes: a drive hub mounted on an output shaft of a power source and protruding radially outward beyond an outer periphery of the output shaft; a friction member for transmitting driving force from the drive hub to a blade holder, the drive hub and the friction member having respective curved surfaces slidable on each other when the drive hub and the friction member are in abutting engagement with each other; a grass cutting blade attached to the blade holder; and an energy absorbing member disposed in a space defined by the blade holder and members peripheral to the blade holder, the energy absorbing member being constructed to maintain its shape during normal grass cutting condition but deform when a load exceeding a predetermined value acts on the energy absorbing member.