Actuator No-Back Arrangement with Segmented Brake Controller
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Solution Overview
Problem
Conventional no-back devices for screw actuators in aircraft require axial loading and torque transmission, limiting design options and complicating maintenance, as they need to be disassembled for maintenance due to integrated axial and torque feedback, which can lead to wear and increased complexity.
Innovation Solution
A no-back device design that allows for off-axis placement and independent operation of the brake controller, using a biasing device to engage braking torque without axial feedback forces, and a brake controller to reduce braking torque when the motor is activated, enabling flexible placement and easier maintenance by decoupling axial and rotational movements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the no-back device is integrated to receive both axial loading and torque from the screw shaft, then the braking function is effective, but the design options are limited and maintenance complexity increases
Solution Approach 1:
The no-back device is segmented into separate functional components: the brake controller is separated from the brake members, and the axial loading path is decoupled from the torque transmission path. This allows the brake controller to be positioned independently and accessed for maintenance without removing the entire actuator assembly.
Solution Approach 2:
The brake controller is extracted from the integrated no-back device assembly and positioned separately. This extraction allows the brake controller to be accessed and maintained independently while the brake members remain engaged with the screw shaft, simplifying maintenance procedures.
2Reliability
If the brake members are constantly engaged to prevent feedback torque, then the screw shaft is protected from unwanted rotation, but the motor must overcome brake friction during operation
Solution Approach 1:
The brake controller dynamically adjusts the engagement state of the brake members based on operational conditions. During motor operation, the brake controller disengages the brake members to eliminate friction resistance. When the motor is not operating, the brake members are engaged to prevent unwanted rotation of the screw shaft from feedback torque.
Solution Approach 2:
The system uses feedback from the motor operation state to control the brake engagement. The brake controller monitors whether the motor is activated and相应地 adjusts the brake member engagement, ensuring the brake is applied only when needed to prevent unwanted rotation, not during motor operation.
3Power
If the no-back device is placed on-axis with the screw shaft, then torque transmission is direct, but the placement options are restricted
Solution Approach 1:
The no-back device is divided into two separable components: brake members that remain on-axis with the screw shaft for direct torque transmission, and a brake controller that can be positioned off-axis. This segmentation allows the brake members to maintain efficient torque transmission while the brake controller can be placed in various locations for ease of access and integration.
Solution Approach 2:
A mechanical linkage or actuation mechanism serves as an intermediary between the off-axis brake controller and the on-axis brake members. This intermediary transmits the control force from the remotely positioned brake controller to the brake members engaged with the screw shaft, enabling flexible placement while maintaining functional effectiveness.
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
This design enhances design flexibility, reduces maintenance complexity, and eliminates the need for axial feedback forces to activate the braking system, allowing for more reliable and efficient operation of screw actuators by reducing the motor's workload against brake friction.
Implementation Method 1
a biasing device for providing a force to urge the brake members to engage with one another when the motor is not activated
Implementation Method 2
a brake comprising a no-back device brake member for engagement with a screw shaft brake member connected to the screw shaft in order to generate a braking torque on the screw shaft when the brake members engage with one another
Data Source
Figure 1A~1C
Figure 2A~2B
Figure 3
AI summary
A screw actuator 16 comprises a screw shaft 17 for threaded engagement with an actuator output device 21 such that rotation of the screw shaft 17 causes linear movement of the actuator output device 21; and a motor 12 for driving rotation of the screw shaft 17. A no-back device 10; 20; 30 is included for restricting movement of the screw shaft 17 in response to feedback torque applied due to external forces on the actuator output device 21, and the no-back device 10; 20; 30 comprises a brake 104, 108; 314, 308 and a brake controller 22; 212 the brake 104, 108; 314, 308 comprising a no-back device brake member 104; 314 for engagement with a screw shaft brake member 108; 308 connected to the screw shaft 17 in order to generate a braking torque on the screw shaft 17 when the brake members 104, 108; 314, 308 engage with one another, and a biasing device 102; 202; 302 for providing a force to urge the brake members 104, 108; 314, 308 to engage with one another when the motor 12 is not activated, this force hence resulting in a braking torque that resists rotation of the screw shaft 17 under feedback torque; and the brake controller 22; 212 being arranged to provide a force to urge the brake members 104, 108; 314, 308 to disengage with one another, this force being applied upon activation of the motor 12 for rotating the screw shaft 17, in order that the braking torque is reduced when the motor 12 is activated.