Breakable Coupling Device for Aircraft Trim Actuator Torque Limiting
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Solution Overview
Problem
Current trim actuators in aircraft, particularly helicopters, face issues with catastrophic failure due to engine seizure, leading to incomplete uncoupling from flight controls, which can result in residual forces and operational difficulties during actuator blockages.
Innovation Solution
A retractable coupling device with a locking and compression mechanism, featuring a first discontinuous and second continuous housing, ensures irreversible uncoupling of the trim actuator from the flight control above a predetermined torque, preventing re-engagement without human intervention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fusible pin is used to uncouple the trim actuator from the flight control, then the connection can be broken in the event of blocking, but the pin requires delicate sizing and may not break optimally, leaving residual forces that hamper flight controls
Solution Approach 1:
The coupling device is segmented into distinct functional components: a locking means with discontinuous housing, a compression means with continuous housing, and a drive means (ball) that transitions between them. This segmentation allows the system to provide definitive uncoupling by moving the drive means from the locking housing to the compression housing, eliminating residual forces that plague single-component fuse pin designs
Solution Approach 2:
The drive means (ball) acts as an intermediary element that mediates between the locking means and compression means. When torque exceeds the predetermined threshold, this intermediary element moves from the discontinuous housing of the locking means to the continuous housing of the compression means, definitively uncoupling the trim actuator from the flight control while eliminating residual forces
2Force
If a torque limiter with balls moving between orifices is implemented, then torque can be limited to a predetermined value, but the balls continuously leaving and returning require constant pilot struggle and are not transposable inside a trim cylinder
Solution Approach 1:
Instead of allowing balls to continuously leave and return between orifices (which causes constant struggle), the invention inverts the approach by using a discontinuous housing that permanently retains the ball below the torque threshold. When torque exceeds the threshold, the ball moves to a continuous housing, providing torque limitation without continuous ball movement, thereby maintaining ease of operation
Solution Approach 2:
The system dynamically transitions from a locked state (ball in discontinuous housing) to an uncoupled state (ball in continuous housing) based on torque conditions. This dynamic behavior provides torque limitation while ensuring that once uncoupled, the flight controls can be maneuvered without constant pilot struggle, as the ball remains in the continuous housing
3Strength
If a locking means with discontinuous housing is used to retain the drive means below predetermined torque, then coupling is secure, but above the torque the drive means must move to a continuous housing to allow definitive uncoupling
Solution Approach 1:
The housing structure is segmented into two distinct parts: a discontinuous housing for secure retention below torque threshold and a continuous housing for definitive uncoupling above the threshold. This segmentation provides both strong coupling when needed and definitive uncoupling when necessary, while the modular design keeps the overall device complexity manageable
Solution Approach 2:
The housing structure employs asymmetry with a discontinuous housing (providing retention) and a continuous housing (providing uncoupling). This asymmetric design allows the system to provide both strong coupling and definitive uncoupling functions within a single device, balancing the strength requirement with acceptable device complexity
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 definitive and safe uncoupling of the trim actuator from the flight control, eliminating residual forces and ensuring the pilot is not confronted with operational challenges during actuator blockages, thereby enhancing safety and operational reliability.
Implementation Method 1
a compression means (30) compressing the drive means (40) in the first housing (21) of the locking means (20)
Implementation Method 2
the displacement means (50) moving the drive means (40) from the first housing (21) to the second housing (22)
Data Source
Figure 1~3
Figure 4~6
AI summary
The device (10) has a drive unit (40) for connecting a blocking unit (20) and a compression unit (30) together in rotation around a longitudinal rotation axis (AX) below predetermined torque. The blocking unit has a discontinuous housing (21) for receiving the drive unit below the predetermined torque and a continuous housing (22) forming a closed loop. A displacement unit (50) displaces the drive unit non-reversibly from the discontinuous housing towards the continuous housing when torque exerted on the drive unit is greater than the predetermined torque. An independent claim is also included for a trim actuator of an aircraft, comprising a crank.