Epicyclic Gear System Torque Release Mechanism

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Solution Overview

Problem

Traditional power tools face challenges in efficiently changing gear ratios and implementing a torque release mechanism without increasing the size and complexity of the transmission, leading to higher costs, weight, and mechanical strength demands.

Innovation Solution

A gear system that allows the planet carrier to be fixed or freely rotate, enabling shifting between configurations to change gear ratios and provide a torque release mechanism, reducing the torque on transmission components and simplifying the mechanical system.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a traditional key locks the output directly to the rotor to prevent rotor rotation, then the rotor can be reliably stopped, but the mechanical strength demands, costs, weight, and dimensions of the transmission and braking system increase

Engineering Contradiction:

Improverotor stopping reliabilityVSAvoidpower tool weight

Core Design Contradiction:

ReliabilityVSWeight of moving object

Solution Approach 1:

Instead of locking the output directly to the rotor as in traditional systems, the patent inverts the approach by locking the input shaft to the frame when braking is required. This inversion allows the full gear ratio to assist in stopping the rotor, reducing the torque burden on the braking system and thereby reducing weight, cost, and dimensions while maintaining stopping reliability

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent introduces the frame as an intermediary element in the braking mechanism. By connecting the input shaft to the frame during braking, the system uses the frame as a stable reference point to absorb and distribute braking forces, reducing the direct torque load on the rotor and transmission components

Inventive Principle:

Principle #24Intermediary (Mediator)

2Strength

If the input shaft is connected to the frame for braking in servo systems, then the braking system can be less strong, but the solution becomes complicated for power tools with separate transmission units and standard motors

Engineering Contradiction:

Improvebraking system strengthVSAvoidtransmission system complexity

Core Design Contradiction:

StrengthVSDevice complexity

Solution Approach 1:

The patent makes the planet carrier multi-functional by enabling it to perform both normal power transmission and braking functions. By selectively locking or releasing the planet carrier from the frame, the same mechanical structure serves dual purposes, eliminating the need for separate braking mechanisms and reducing overall system complexity while maintaining reduced braking system strength requirements

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Reliability

If traditional transmissions are designed to withstand full rotor torque, then reliability is maintained, but the weight, dimensions, and cost of the power tool increase

Engineering Contradiction:

Improvetransmission reliabilityVSAvoidpower tool volume

Core Design Contradiction:

ReliabilityVSVolume of moving object

Solution Approach 1:

The patent inverts the torque management approach by using the gear system to reduce torque on transmission components during braking. Instead of designing components to withstand full rotor torque, the system uses the input shaft connection to the frame and gear ratio advantage to reduce the torque burden, allowing for smaller, lighter components while maintaining reliability

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent changes the operational parameters of the transmission system by selectively engaging different configurations. During braking, the system changes from direct rotor drive to input shaft frame connection, altering the torque parameters transmitted through the gear system and allowing components to operate at reduced stress levels

Inventive Principle:

Principle #35Parameter changes

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 solution reduces the weight, complexity, and cost of power tools by allowing dynamic gear ratio changes and efficient rotor braking, optimizing the mechanical system with a simpler transmission design.

Implementation Method 1

each planet wheel can rotate epicyclically around the central axis

Methodology Applied

Scientific EffectEpicyclic gearing: Epicyclic Gearing

Implementation Method 2

provides changes in the mechanical advantage between an input and an output shaft

Methodology Applied

Scientific EffectMechanical advantage: Mechanical Advantage

Data Source

PatentUS10391623B2Power tool

Publication Date: 2019.08.27 HILTI AG

AI summary

A power tool with an epicyclically or so called planet gear system with two annulus gears, at least one solar gear with external toothing, and planet wheels having two toothed rings which each mesh with one of the annulus gears. A planet carrier holding the planet wheels. The gear is interchangeable between an at least first configuration and second configuration, wherein the planet carrier is interchangeable between being locked or partly locked rotationally to the frame or being unlocked rotationally from the frame.