Hedgecutter Eccentric Rotor and Planetary Gear Design
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Solution Overview
Problem
Existing vegetation cutting tools, such as hedgecutters, face issues with high wear and energy losses due to high rubbing speeds, limited stroke, and increased production costs in single piece rotor and eccentrics construction, as well as limited gear ratios and radial load capacity in spur gear designs, leading to reduced cutting capability and efficiency.
Innovation Solution
A cutting apparatus with a demountable blade unit featuring a single piece eccentric rotor, planetary gear, and rolling element bearings that allow axial movement, minimizing preloading and frictional losses, and enabling higher torque and power output, suitable for both corded and cordless hedgecutters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If separate eccentric discs are used with a central rotor, then torque transmission is achieved, but the eccentric size must be large and rubbing speeds are high causing increased wear and energy losses
Solution Approach 1:
The patent merges the rotor and eccentrics into a single integrated component (single piece rotor and eccentrics construction). This eliminates the need for separate eccentric discs and reduces the number of interfaces, thereby reducing rubbing speeds and energy losses while maintaining torque transmission capability.
2Loss of energy
If single piece rotor and eccentrics construction is used, then eccentric diameters are reduced and losses are reduced, but production costs increase and blade stroke is limited
Solution Approach 1:
The patent segments the single piece rotor and eccentrics construction into demountable components. The blade assembly with eccentrics can be detached from the rotor, allowing for easier manufacturing, reduced production costs, and the ability to service or replace components independently while maintaining the low loss benefits of the integrated design.
3Speed
If spur gear construction is used, then motion transfer is achieved, but the pinion is overhung in cantilever fashion causing limited radial load capacity and limited gear ratios
Solution Approach 1:
The patent introduces axial movement capability to the pinion through the demountable blade unit design. This allows the pinion to move axially within the housing, converting the cantilevered radial load situation into a configuration where loads can be better distributed and managed, thereby increasing radial load capacity while maintaining motion transfer efficiency.
4Reliability
If blades are fixed in position on eccentrics, then cutting action is maintained, but wear occurs and serviceability is reduced
Solution Approach 1:
The patent makes the blade assembly dynamic by enabling it to be easily detached and reattached. The demountable design allows the blade unit to be removed when worn or damaged and replaced with a fresh assembly, maintaining reliable cutting action while dramatically improving serviceability and reducing downtime.
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 enhances cutting forces and extends run times per battery charge by reducing frictional losses and allowing for more powerful motor usage without side loading, effectively addressing the limitations of prior art designs.
Implementation Method 1
a planetary gear adapted to transfer motion to the eccentric rotor
Implementation Method 2
an eccentric rotor comprising an eccentric associated with each of said at least one reciprocatable blades
Implementation Method 3
the eccentric rotor includes a bearing on each of the upper and lower shaft portions
Data Source
Figure 1
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AI summary
The present invention relates to cutting tools, in particular to vegetation cutting tools such as hedgecutters or hedgetrimmers. We will describe a cutting apparatus (10) comprising a housing, a blade assembly comprising at least one reciprocatable blade (11, 12) and an eccentric rotor (60) comprising an eccentric (61, 62) associated with each blade (11, 12); and an electric motor (20) adapted to drive said eccentric rotor (60). The apparatus (10) further comprises a planetary gear adapted to transfer motion to the eccentric rotor (60). The eccentric rotor (60) comprises a shaft having upper and lower shaft portions (64, 65) carrying each of said eccentrics (61, 62) therebetween; and includes a bearing (70) on each of the upper and lower shaft portions (64, 65). In one aspect, the blades (11, 12), rotor (60) and bearings (70) are formed as a demountable blade unit. In a further aspect the housing is adapted to support the bearings (70) and permit axial movement of the eccentric rotor (60) within the housing.