Planetary Gearbox Locking Elements for Garden Tool Torque Management
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Solution Overview
Problem
Existing gardening tools with belt-driven transmissions face difficulties in handling varying soil conditions due to high operating forces and risk of slipping, especially in heavy soils, which complicates gear selection and requires high drive power.
Innovation Solution
A multi-gear, switchable planetary transmission system with a transmission housing and at least two planetary stages, each with a ring gear and locking elements, allowing for selective engagement and disengagement to manage high torques and provide multiple gear ratios, including reverse gear, for improved handling and reduced wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If belt drives are used for transmission, then the gardening tool can be operated in different directions of rotation, but the clutch actuation becomes vulnerable and unreliable under high operating forces
Solution Approach 1:
The patent replaces the belt-driven friction clutch system with a planetary gear system featuring positive engagement locking elements. This substitution eliminates the slipping and vulnerability inherent in friction-based belt drives, providing reliable torque transmission through mechanical interlocking of locking elements with gear teeth.
Solution Approach 2:
The transmission system is segmented into multiple independent planetary stages, each capable of being locked or unlocked independently. This segmentation allows versatile operation modes (forward, reverse, neutral) while maintaining reliable positive engagement in each stage through dedicated locking elements that engage with gear teeth rather than relying on friction.
2Adaptability or versatility
If friction shoes are used to fix ring gears, then gear selection is possible, but high contact pressure makes actuation difficult and slipping risk increases
Solution Approach 1:
The patent replaces friction shoe-based locking with positive engagement locking elements that mechanically interlock with gear teeth. This substitution eliminates the need for high contact pressure, allowing easy actuation through simple engagement/disengagement of the locking elements without risking slips, while still enabling reliable gear selection across multiple planetary stages.
3Strength
If high drive power is provided for heavy soils, then soil loosening capability is improved, but the overall device size and power consumption increase
Solution Approach 1:
The patent implements a multi-stage planetary transmission system with variable reduction ratios that allows dynamic adaptation to different soil conditions. By selecting appropriate gear ratios, the system optimizes torque delivery to match soil resistance, enabling effective operation in heavy soils with lower motor power than would be required with a fixed-ratio transmission.
Solution Approach 2:
The transmission system allows changing the reduction ratio parameter according to soil conditions and tool requirements. This parameter adjustment capability enables the same motor to deliver appropriate torque across varying loads, reducing the peak power requirement while maintaining soil loosening capability in heavy soils through optimal gear selection.
Data Source
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AI summary
The implement has a drive motor (1) for rotatably driving a tool (2), and a gearbox arranged between the drive motor and the tool. The gearbox is a multi-gear, switchable planetary gearbox (3) with a gearbox housing (4) and planetary stages. Each planetary stage has an internal gear for selectively releasing fixing elements (13), where the fixing elements fix the respective internal gear with respect to the gearbox housing in a torque proof manner. The fixing elements are formed as rigid pivoting arms with locking projections.