Rotary Lock Assembly for Self-Unlocking Linear Actuators
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Solution Overview
Problem
Conventional linear actuators face challenges such as indirect locking mechanisms, increased size and mass, fatigue issues, low external load carrying capability, and the need for additional mechanical inputs for unlocking, particularly under high mechanical loads.
Innovation Solution
A rotary-to-linear motion conversion device utilizing a multi-stage planetary gearbox with a rotary lock assembly that includes epicyclic gear assemblies, a lock key, and a lock rotor, which automatically redirects torque to overcome binding and facilitate unlocking without additional control or power inputs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional lock mechanism is used, then the actuator can be locked in a fixed position, but the locking is indirect and requires additional mechanical inputs for unlocking
Solution Approach 1:
The planetary gear assembly automatically redirects torque from the ring gear to the sun gear to rotate the lock rotor and unlock the lock keys, enabling the system to unlock itself without external mechanical inputs. The high mechanical advantage of the planetary gears provides sufficient torque multiplication to overcome binding forces during automatic unlocking.
2Reliability
If a multi-piece housing with direct locking is used, then direct locking is achieved, but the size and mass of the actuator increase
Solution Approach 1:
The locking mechanism components (lock rotor, lock keys, planetary gear assembly) are integrated within a single-piece housing, eliminating the need for multiple separate housing pieces. This integration maintains direct locking capability while reducing overall actuator mass and simplifying the structure.
3Ease of operation
If ball lock mechanisms are used, then the actuator can be operated by a rotary source, but the external load carrying capability is limited due to point contact stresses
Solution Approach 1:
The lock keys are designed with increased contact area dimensions compared to point-contact ball locks. The lock keys engage with the linear output assembly over a larger surface area, distributing contact stresses and enabling the actuator to handle higher external loads while maintaining rotary source operation.
4Reliability
If a rotary-to-linear motion conversion mechanism is used for the lock sleeve, then locking functionality is achieved, but the device complexity increases
Solution Approach 1:
The planetary gear assembly serves dual functions: it provides the rotary-to-linear motion conversion needed for lock key engagement, and simultaneously provides torque multiplication for automatic unlocking. This multi-functionality reduces overall device complexity compared to separate mechanisms for each function.
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, provides reliable unlocking operations under high mechanical loads, and automatically supplies the necessary torque for unlocking, enhancing the system's reliability and efficiency.
Implementation Method 1
a first epicyclic gear assembly (212a) including a sun gear assembly (220), a ring gear assembly (222), and a planet gear assembly (224) mechanically engaged to the sun gear assembly and the ring gear assembly
Implementation Method 2
a screw lead (282) engaged to the planet gear assembly and responsive to revolution of the planet gear assembly, and a nut (284) engaged with the screw lead and axially movable along the screw lead in response to rotation of the screw lead
Implementation Method 3
configured to receive the lock key in the first lock key configuration and be prevented from moving linearly based on mechanical interference between the lock key and at least one of the first axial groove face and the second axial groove face
Data Source
AI summary
The subject matter of this specification can be embodied in, among other things, a rotary lock assembly that includes a first epicyclic gear assembly having a first sun gear assembly, a first ring gear assembly, and a first planet gear assembly mechanically engaged to the first sun gear assembly and the first ring gear assembly, and a second epicyclic gear assembly having a second sun gear assembly configured to be rotated by the first ring gear assembly, a second ring gear assembly, and a second planet gear assembly mechanically engaged to the second sun gear assembly and the second ring gear assembly.