Rotary Lock Assembly With Planetary Gear Unlocking Under High Load
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Solution Overview
Problem
Conventional linear actuators face limitations in direct locking mechanisms, including increased size and mass, flexing lock element fatigue, and low external load carrying capability due to point contact stresses, as well as the need for additional mechanical inputs for unlocking, which are not suitable for high-tension applications like aircraft thrust reversers.
Innovation Solution
A rotary lock assembly utilizing a multi-stage planetary gearbox with epicyclic gear assemblies and a lock rotor mechanism that automatically redirects torque to overcome binding and unlock the actuator under high loads, providing reliable locking and unlocking operations without additional control inputs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a direct locking mechanism is used in a linear actuator, then the locking reliability is improved, but the device size and mass increase
Solution Approach 1:
The patent combines the locking mechanism and motion conversion mechanism into a single integrated assembly. The lock sleeve and key are mechanically coupled to the planetary gear system, allowing the locking function to be performed without adding separate locking components that would increase mass. The integrated design achieves direct locking while maintaining compact dimensions.
2Device complexity
If a flexing lock element is used to reduce housing complexity, then the device complexity is reduced, but the reliability decreases due to fatigue
Solution Approach 1:
The locking mechanism is divided into separate rigid components: a lock sleeve with external splines and a lock key with internal splines. These segmented rigid parts engage through toothed interfaces rather than flexing, eliminating fatigue concerns while maintaining structural simplicity. The segmentation allows each component to be optimized for its specific function without requiring complex housing structures.
3Device complexity
If ball lock mechanisms are used, then the device complexity is reduced, but the external load carrying capability decreases due to point contact stresses
Solution Approach 1:
The patent uses a sleeve-and-key geometry with circumferential engagement surfaces rather than point-contact balls. The lock key features an outer cylindrical surface that engages with internal splines in the lock sleeve, distributing contact stresses over extended surface areas. This curved surface engagement provides high load carrying capability while maintaining mechanical simplicity.
4Ease of operation
If an electrically operated solenoid mechanism is used to unlock the actuator, then the ease of operation is improved, but the device complexity and power requirements increase
Solution Approach 1:
The patent replaces electrical solenoid unlocking with a purely mechanical torque-reversal unlocking mechanism. The planetary gear system naturally reverses torque direction when the ram reaches its travel limits, automatically rotating the lock sleeve to disengage the lock key. This mechanical substitution eliminates electrical components while maintaining ease of operation through automatic end-of-travel detection.
5Reliability
If a linear motion lock sleeve and key arrangement is used, then the locking reliability is improved, but the device complexity increases due to the rotary-to-linear motion conversion mechanism
Solution Approach 1:
The planetary gear system serves multiple functions simultaneously: it converts rotary motor output to linear ram motion through the screw mechanism, and it also drives the lock sleeve rotation for locking/unlocking operations. This multi-functionality eliminates the need for a separate rotary-to-linear conversion mechanism dedicated solely to locking, reducing overall device complexity while maintaining reliable locking.
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 locks linear actuators against unintended extension, ensures reliable unlocking under high mechanical loads, and provides additional torque for unlocking without additional power inputs, enhancing the reliability and efficiency of the actuator system.
Implementation Method 1
a first epicyclic gear assembly (212a) and a second epicyclic gear assembly (212b)
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A rotary lock assembly (260) that includes a first epicyclic gear assembly (210) having a first sun gear assembly (220, 230), a first ring gear assembly (222, 232), and a first planet gear assembly (224, 234) mechanically engaged to the first sun gear assembly (220, 230) and the first ring gear assembly (222, 232), and a second epicyclic gear assembly (210) having a second sun gear assembly (220, 230) configured to be rotated by the first ring gear assembly (222, 232), a second ring gear assembly (222, 232), and a second planet gear assembly (224, 234) mechanically engaged to the second sun gear assembly (220, 230) and the second ring gear assembly (222, 232).