Coaxial Planetary Gear Assembly for Precision Rotational Control

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Solution Overview

Problem

Current rotational control devices, such as stepper motors and worm gears, are expensive, require maintenance, and introduce inaccuracies due to tolerances, limiting their precision and adaptability for various installation configurations.

Innovation Solution

A coaxially arranged reduction gear assembly with a planetary gear configuration that converts high rotational speed and low torque input into high torque and low rotational speed output, featuring a stationary gear section, planetary gear assembly, and output rotational gear section, allowing for precise rotational control with adaptable installation options and reduced maintenance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If stepper motors are used for precision rotational positioning, then rotational accuracy is improved, but cost and maintenance requirements increase

Engineering Contradiction:

Improverotational accuracyVSAvoidcost

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

The patent replaces the stepper motor's electromagnetic pulse-driven mechanical system with a continuous rotation motor coupled to a gear train. The gear train (including planetary gears and worm gear) mechanically achieves the precision positioning that the stepper motor achieved through controlled pulsing, thereby eliminating the need for expensive stepper motors while maintaining rotational accuracy

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces an intermediary gear train system between the continuous rotation motor and the load. This intermediary mechanism (comprising multiple gear stages including planetary and worm gears) translates the high-speed rotation into precise, controlled rotational movement, serving as a mediator that achieves positioning accuracy without requiring a expensive stepper motor

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of repair

If worm gears are used for rotational control, then maintenance requirements are reduced, but efficiency is limited by design

Engineering Contradiction:

Improvemaintenance requirementsVSAvoidefficiency

Core Design Contradiction:

Ease of repairVSLoss of energy

Solution Approach 1:

The patent segments the gear train into multiple stages, placing the worm gear only at the final output stage rather than using it for the entire reduction. The earlier stages use planetary gears and other efficient gear mechanisms, reserving the worm gear's self-locking and maintenance-free properties for the final stage where its efficiency limitations have minimal impact on overall system performance

Inventive Principle:

Principle #1Segmentation

3Force

If traditional gear arrangements are used for rotational reduction, then torque is increased, but positional accuracy is reduced due to tolerances

Engineering Contradiction:

ImprovetorqueVSAvoidpositional accuracy

Core Design Contradiction:

ForceVSMeasurement precision

Solution Approach 1:

The patent divides the torque multiplication into multiple gear stages rather than using a single large reduction ratio. Each stage uses precision gears with manageable tooth counts, and the cumulative effect of multiple precise stages achieves both high torque multiplication and maintained positional accuracy, as errors do not compound as significantly as in a single-stage system

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent employs planetary gears that utilize radial and axial dimensions simultaneously to achieve torque multiplication. The planetary arrangement distributes load across multiple tooth contacts in three-dimensional space, maintaining precision while multiplying torque through the geometric arrangement rather than relying solely on large gear size differences

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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 coaxial reduction gear assembly provides precise rotational control with high gear ratios, reducing power requirements, increasing motor longevity, and offering a cost-effective solution with lower maintenance needs compared to traditional systems, while being adaptable to various motor placements and configurations.

Implementation Method 1

The planetary gear arrangement in conjunction with an offset gear configuration resulting in a high torque, highly accurate rotational motion

Methodology Applied

Scientific EffectMechanical Advantage: Mechanical Advantage

Data Source

PatentUS9127752B2Method of reducing a rotational output rate from a coaxially arranged rotating input

Publication Date: 2015.09.08 AB SKF SKF PATENT DEPARTMENT

AI summary

A method of rotating an output gear at a rotational rate that is slower than an input rotational rate. The input rotation moves a planetary gear in a circular motion about a central axis. A first stage external gear configuration of the planetary gear engages with an internal gear configuration of a stationary gear. The engagement rotates the planetary gear about a concentrically located planetary gear rotational axis. A second stage external gear configuration is rotated by and at a same rate the first stage external gear configuration. The first stage diameter and/or number of teeth differs from the second stage diameter and/or number of teeth. The planetary gear rotation in conjunction with the difference between the first and second stages causes the output gear to rotate respective to the stationary gear. Rotational positioning of the output gear can be monitoring and adjusted by controlling the input rotational rate.