Planetary Gear Chainsaw Drive for Compact One-Handed Tools
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Solution Overview
Problem
Hand-held power tools with electric drives, such as chainsaws, tend to be bulky due to the voluminous drive unit consisting of an electric motor and gearbox, making them unwieldy and less compact than desired.
Innovation Solution
A compact design is achieved by integrating a motor-gear unit with a planetary gear system inside the housing, where the planetary gear has a rotationally fixed ring gear, sun gear, and planet gears mounted on a planet carrier, which is mounted on the housing with a bearing, allowing for axial and tilting movements to compensate for tolerances and reduce friction, and a central shaft connected to the sun gear and rotor, supporting the compact structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a traditional electric motor and gearbox are used as separate components, then the drive unit provides sufficient power and speed control, but the overall size and volume of the hand-held power tool becomes large and bulky
Solution Approach 1:
The patent merges the electric motor and gearbox into a single integrated drive unit where the motor rotor is directly coupled with the planetary gear system. The motor housing serves as part of the gear housing structure, eliminating the need for separate motor mounting and reducing overall volume while maintaining full power transmission capability through the integrated design.
Solution Approach 2:
The planetary gear system is nested within the motor housing structure. The sun gear is mounted on the motor rotor, planet gears orbit around it, and the ring gear is positioned within the motor housing boundaries. This nested arrangement allows the gearbox to be contained within the motor's spatial envelope, dramatically reducing the overall drive unit volume.
2Reliability
If the ring gear is fixed in position to provide stable power transmission, then transmission reliability improves, but the system cannot compensate for manufacturing tolerances and friction
Solution Approach 1:
The ring gear is designed with controlled mobility, allowing it to perform small settling movements and axial displacement within the housing. This dynamic capability enables the system to automatically compensate for manufacturing tolerances and reduce friction during operation, while the gear remains functionally fixed for reliable power transmission. The bearing arrangement permits these minor movements without compromising transmission stability.
3Ease of operation
If the output element is subjected to one-sided load from the saw chain, then cutting function is achieved, but additional bearings are required to support the asymmetric load
Solution Approach 1:
The planet carrier bearing is designed to perform multiple functions simultaneously: it supports the planet carrier rotation, accommodates the one-sided load from the output element, and provides tolerance compensation. This multi-functional bearing arrangement eliminates the need for additional dedicated load-bearing components, maintaining cutting functionality while reducing overall system complexity.
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 configuration results in a more compact and stable hand-held power tool, enabling efficient operation with reduced size and weight, while maintaining stability and efficiency, particularly when the output element is loaded on one side, such as with a saw chain.
Implementation Method 1
The planetary gear comprises at least one non-rotatable ring gear, a sun gear driven by the electric motor, and at least one planet gear mounted on a planet carrier
Implementation Method 2
A planet carrier is mounted on the housing by a planet carrier bearing, in particular, rotatably mounted. This can, for example, compensate for tolerances, enable settling movements, and/or achieve low-force and low-friction mounting or rolling of the planets and/or the planet carrier
Data Source
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AI summary
The invention relates to a hand-held power tool (1), in particular a chainsaw (2), and advantageously a one-handed chainsaw. The hand-held power tool (1) comprises a motor-gearbox unit (10) and a housing (3). The motor-gearbox unit (10) is arranged at least partially within the housing (3). The motor-gearbox unit (10) comprises an electric motor (20) and a planetary gear set (30). The planetary gear set (30) comprises at least one non-rotating ring gear (32), a sun gear (31) driven by the electric motor (20), and at least one planet gear (37) mounted on a planet carrier (34). An output element (40) of the motor-gearbox unit (30), in particular a sprocket (41) for driving a saw chain (42), is connected to the planet carrier (34). The planet carrier (34) is mounted on the housing (3) by a planet carrier bearing (35).