Ball Nut Locking Actuator for Compact Thrust Reverser Stowage
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Solution Overview
Problem
Existing thrust reverser actuator locking mechanisms, such as tine locks, suffer from fatigue and potential failure due to repeated flexing of clawed fingers, which can lead to accidental deployment of thrust reversers, and require longer overall lengths for increased fatigue life, compromising system design.
Innovation Solution
A ball nut locking mechanism featuring a lock housing with a sleeve and a locking collar that engages with a chamfered locking projection on the ball nut, utilizing a solenoid or hydraulic system to disengage the locking element, allowing for secure stowage and reduced overall actuator length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a tine lock with clawed fingers is used to lock the ball nut, then the actuator can be locked in the stowed position, but the repeated flexing of the clawed fingers leads to fatigue and potential failure
Solution Approach 1:
The patent replaces the mechanical tine lock system with a ball screw-driven locking mechanism. The locking collar moves axially along the ball screw thread to engage or disengage from the ball nut, eliminating the need for flexing clawed fingers. This substitution of the mechanical locking principle fundamentally resolves the fatigue issue while maintaining reliable locking functionality.
Solution Approach 2:
The patent employs a solenoid actuator that utilizes electromagnetic force (analogous to pneumatic/hydraulic actuation principles) to move the locking collar axially. The solenoid converts electrical energy to mechanical motion, driving the locking collar into engagement with or disengagement from the ball nut, providing controlled and reliable locking without mechanical flexing components.
2Duration of action of stationary object
If the clawed fingers are made longer to increase fatigue life, then the fatigue life increases, but the overall length of the actuator must be increased
Solution Approach 1:
The patent eliminates the need for long flexing fingers by replacing the tine lock mechanism with a ball screw-based locking system. The locking collar engages directly with the ball nut through axial movement along the ball screw thread, providing sufficient fatigue life without requiring increased component length. This resolves the contradiction by changing the fundamental locking mechanism rather than scaling up the existing one.
3Reliability
If a locking mechanism is provided to prevent accidental deployment, then the actuator can be locked in the stowed position, but the mechanism adds complexity to the actuator design
Solution Approach 1:
The patent merges the locking mechanism with the existing ball screw drive system. The locking collar utilizes the ball screw thread for both driving motion and locking engagement, eliminating the need for separate locking components. This integration reduces overall complexity while maintaining reliable locking functionality against accidental deployment.
Solution Approach 2:
The ball screw serves multiple functions: it provides the primary driving motion for the actuator and simultaneously serves as the locking mechanism through the locking collar's engagement. This multi-functionality reduces the number of separate components needed, thereby reducing overall system complexity while ensuring 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 provides a robust locking mechanism that enhances the fatigue life of the actuator while maintaining a compact design, reducing the risk of accidental deployment and allowing for efficient reverse thrust operation.
Implementation Method 1
The actuator may comprise a solenoid which drives movement of the locking collar
Implementation Method 2
The ball nut may be connected to the thrust reverser arrangement such that movement of the ball nut along the ball screw shaft between a stowed and deployed position moves the thrust reverser arrangement correspondingly
Data Source
Figure 1
Figure 2(a)~2(e)
Figure 3(a)~3(e)
AI summary
An actuator comprises a ball nut (10) and a lock housing (20) arranged radially outuvardly of the ball nut and overlapping a proximal end of the ball nut when the ball nut is in a stowed position. The lock housing (20) comprises a sleeve (21) in which is located an aperture (23), and a locking element (30) is retained within the aperture and can move in a radial direction through the aperture. When the ball nut (10) is in the stowed position, the locking element (30) engages with a locking projection (15) on the ball nut (10), to retain the ball nut in the stowed position.