Planetary Gear Self-Locking Mechanism Against Back-Driving
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Solution Overview
Problem
Existing gear sets lack a self-locking mechanism that prevents back-driving while allowing efficient forward-driving, leading to inefficiencies and increased power requirements, especially in applications like butterfly valves where system forces can cause unwanted movement.
Innovation Solution
A self-locking apparatus for gear sets utilizing differentiating connectors and unidirectional engage/disengage components, such as locking wedges or ratchet mechanisms, that allow forward rotation in both directions while preventing back rotation, ensuring the gear set remains locked against back-driving forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a low helix angle worm and gear set is used to achieve self-locking, then back-driving is prevented, but efficiency drops below 35%
Solution Approach 1:
The locking function is segmented from the power transmission function. Locking wedges are separate components that engage with planet gears independently, allowing the gear set to maintain high efficiency during forward operation while providing self-locking capability when needed, without requiring a low-efficiency worm and gear configuration
Solution Approach 2:
Locking wedges act as intermediary components between the planet gears and the planet carrier. These wedges provide the locking function by engaging with the planet gears, preventing back-driving forces from rotating the planet carrier, while allowing efficient power transmission during forward operation
2Reliability
If frictional forces are increased to prevent back-driving, then self-locking is achieved, but larger power sources are required
Solution Approach 1:
The locking wedges are positioned and configured in advance to engage with the planet gears before back-driving forces can cause unwanted movement. This preliminary locking action prevents back-driving without requiring increased friction or larger power sources, as the mechanical engagement occurs proactively
Solution Approach 2:
The locking mechanism is self-actuating through the motion of the planet gears themselves. As the planet gears rotate within the planet carrier slots, they automatically engage or disengage the locking wedges based on the direction of rotation, providing self-locking capability without requiring additional power input or friction-based mechanisms
3Reliability
If ratchet cams are used to lock the gear set, then back-driving is prevented, but the mechanism becomes complex and cannot be used with spur gears
Solution Approach 1:
The locking wedges and planet carrier slots provide a universal locking mechanism that can be used with various gear types including spur gears, planetary gears, and worm gears. The design does not require helical members or complex ratchet cam mechanisms, making it adaptable to different gear configurations while maintaining simplicity and effectiveness
Solution Approach 2:
Instead of using complex ratchet cams that engage with the gear teeth, the invention inverts the approach by having simple locking wedges engaged by the planet carrier slots. The planet carrier slots guide the planet pins and locking wedges, reversing the traditional ratchet mechanism and achieving locking with simpler, more versatile components
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 prevents back-driving while maintaining high efficiency (up to 99%), reducing power consumption and preventing unwanted movement in applications like butterfly valves and winches, by allowing forward driving in both rotational directions while locking against back-driving forces.
Implementation Method 1
first and second locking wedges... that allow rotation when being forward driven but prevent rotation when being back driven
Implementation Method 2
planet pins in the planet carrier slots... allowing the planet gears in the planet carrier to contact the locking wedges
Data Source
AI summary
A self-locking apparatus for a gear set permits forward-driving an input in clockwise or counterclockwise directions and substantially prevents an output from being driven in either or both of those directions. The device includes a gear set with planet gears arranged within a planet carrier within a fixed ring gear. Each of the planet gears is engaged with the planet carrier via a differentiating connector retained in an elongated slot in the planet carrier where it moves to the clockwise position when being forward driven in the clockwise direction and, when the planet carrier is back driven in the clockwise direction, the connector moves to the counter-clockwise position in the slot. This arrangement allows the gear set to be forward driven but not back driven. This differentiated action can engage/disengage with any form of unidirectional engage/disengage mechanism. The apparatus is useful in industrial applications requiring self-locking gear sets.