Planetary Gear Assembly with Integral Frusto-Conical Clutch
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Solution Overview
Problem
High-end hedgecutters require a slipping clutch to protect against catastrophic damage from sudden motor stoppages due to high rotational energy, but existing separate clutch elements add weight and size, necessitating a more integrated solution.
Innovation Solution
A planetary gear assembly with an integral slipping clutch featuring axially overlapping frusto-conical ring gears made of bronze, a biasing spring, and a single component planet carrier and sun gear, which provides torque limiting and reduces the need for a separate clutch.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a separate slipping clutch is provided to protect against catastrophic damage, then reliability is improved, but device complexity and weight increase
Solution Approach 1:
The patent combines the slipping clutch function directly into the planetary gear assembly by forming frusto-conical surfaces on the ring gears, eliminating the need for a separate clutch element. The first and second ring gears are formed with matching frusto-conical surfaces that create an integral protection mechanism within the gear assembly itself.
2Reliability
If a separate slipping clutch is provided to protect against catastrophic damage, then reliability is improved, but weight increases
Solution Approach 1:
The protection mechanism is merged with the existing ring gears of the planetary assembly. The frusto-conical surfaces are formed directly on the ring gears, which are already present components in the power tool, thereby avoiding the addition of separate clutch parts that would increase weight.
3Reliability
If a separate slipping clutch is provided to protect against catastrophic damage, then reliability is improved, but size increases
Solution Approach 1:
The slipping clutch functionality is integrated into the existing planetary gear assembly structure. The frusto-conical surfaces are formed on the ring gears that are already part of the compact planetary arrangement, eliminating the need for additional space that a separate clutch would require.
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 reduces the risk of damage by allowing controlled slip during sudden load peaks, maintaining tool integrity while minimizing weight and size, and is applicable to other high-inertia cutting tools like lawnmowers and shredders.
Implementation Method 1
the first and second stage ring gears are formed with an axial overlap provided by matching or making frusto-conical surfaces
Implementation Method 2
the assembly further comprises a biasing element biasing the first and second ring gears into contact. Preferably, the biasing element is a spring
Data Source
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AI summary
The present invention relates to a protection clutch, in particular a slipping protection clutch, more particularly a clutch for a planetary gearbox (10), especially a planetary gearbox (10) for an electric hand tool such as a hedgecutter. We describe a planetary or epicylic gear assembly (10) comprising first and second stages, each stage comprising a respective sun gear (13, 24); one or more planet gears (15, 22) mounted within a respective ring gear (14, 25) and mounted to a respective planet carrier (20, 23). The first and second stage ring gears (14, 25) are formed with an axial overlap provided by mating frusto-conical surfaces (32, 33). Advantageously, the frusto-conical surfaces are bronze.