Bi-level Lawnmower Blade Mulching and Vibration Control
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Solution Overview
Problem
Existing bi-level lawnmower blades suffer from reduced mulching efficiency due to small upper cutting edges, static balancing issues leading to vibrations and resonances, and compromised air flow, which requires frequent lawn cleaning and increased noise.
Innovation Solution
A bi-level blade design with a central portion keyed onto a vertical motor axis, featuring upper and lower cutting edges with optimized vertical and transverse distances to enhance air flow and cutting surface, and a single-piece construction with ribs for improved stability and reduced inertia, allowing better mulching and reduced noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the upper blade comprises an outward portion with an upper cutting edge, then the blade can cut upper portion of grass, but the longitudinal length of the upper cutting edge is very reduced compromising mulching
Solution Approach 1:
The upper cutting edge is extended not only in longitudinal direction but also in transverse direction by creating an L-shaped configuration. The upper cutting edge comprises a first portion extending in longitudinal direction and a second portion extending in transverse direction perpendicular to the longitudinal axis, thereby increasing the total cutting surface area without increasing the longitudinal length alone.
2Adaptability or versatility
If two separate blades are used in bi-level design, then cutting at two levels is achieved, but static balancing problems occur triggering vibrations and resonances
Solution Approach 1:
The upper blade and lower blade are merged into a single monoblock piece constructed from one continuous material. This integration eliminates the separate parts that caused static unbalancing, while maintaining the bi-level cutting capability through the vertical offset between the upper and lower cutting edges.
3Quantity of substance
If air flow passage is created between upper and lower blades, then air circulation is enabled, but the space required reduces the cutting surface area
Solution Approach 1:
The vertical distance between the upper cutting edge and lower cutting edge is optimized to provide sufficient air flow passage in the critical radial direction where air circulation is needed for mulching, while the transverse extension of the upper cutting edge compensates for any reduction in overall cutting surface area.
4Strength
If fixing tabs are used to connect upper and lower blades, then structural connection is achieved, but the tabs limit the transverse length of cutting edges and destabilize static balancing
Solution Approach 1:
The upper blade and lower blade are formed as a single monoblock piece, eliminating the need for separate fixing tabs. This integration removes the constraints that tabs impose on transverse length while providing inherent structural strength through the continuous material construction.
Data Source
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AI summary
A bi-level blade (1) of a lawnmower is described, which comprises a central portion (2), an upper outward portion (6) comprises an upper cutting edge (61), a lower outward portion (7) comprises a lower cutting edge (71), which are spaced apart by a vertical separation distance (300) and which extend over the entire length of the respective outward portions (6, 7), said central portion (2) comprises a central cutting edge (21), a frontal median connection portion (3) comprises an upper median cutting edge (31). (Figure 1).