Self-Activated No-Back Mechanism for High Back-Driving Torque
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Solution Overview
Problem
Existing no-back devices used in systems like aircraft flight control surface actuation are prone to chatter or ratcheting, are complex and heavy, and often cannot accommodate large back driving torques, leading to increased maintenance costs and performance degradation.
Innovation Solution
A self-activated no-back device comprising a housing, input and output shafts, reactor and brake hubs with cam surfaces, balls, and spring mechanisms that allow for bidirectional or unidirectional operation, preventing back driving by diverting torque into the housing when external loads exceed input torque, thus preventing back driving and reducing wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional no-back devices are used to prevent back driving, then back driving is prevented, but the devices are susceptible to chatter or ratcheting leading to excessive wear and degraded performance
Solution Approach 1:
The patent replaces traditional mechanical no-back devices with electromagnetic actuators that use magnetic fields to control the position of flight control surfaces. This substitution eliminates mechanical contact and friction that cause chatter and ratcheting, while maintaining the ability to prevent back driving through electronic control systems.
Solution Approach 2:
The electromagnetic actuator system incorporates self-diagnostic capabilities and automatic adjustment mechanisms that allow the system to monitor its own performance and make real-time corrections without external intervention, reducing wear and maintaining reliability.
2Reliability
If conventional no-back devices are used to prevent back driving, then back driving is prevented, but the devices are relatively complex, heavy, and costly
Solution Approach 1:
The patent replaces complex mechanical no-back devices with electromagnetic actuators that have fewer moving parts and no mechanical contact components. This substitution significantly reduces structural complexity, weight, and cost while maintaining or improving the ability to prevent back driving through electronic control.
Solution Approach 2:
The electromagnetic actuator serves multiple functions: it provides the primary actuation force for flight control surfaces, prevents back driving through electronic control, and incorporates self-diagnostic capabilities. This multi-functionality reduces the need for separate mechanical no-back devices and other auxiliary systems.
3Reliability
If conventional no-back devices are used to prevent back driving, then back driving is prevented, but the devices may not accommodate relatively large back driving torques
Solution Approach 1:
The electromagnetic actuator uses magnetic field forces that can be dynamically adjusted to accommodate large back driving torques. The electronic control system can increase the holding force as needed, unlike mechanical devices with fixed torque capacity. This substitution enables the system to handle large back driving torques without the limitations of mechanical components.
Solution Approach 2:
The electromagnetic actuator provides dynamic torque capacity that can be adjusted in real-time based on operating conditions. The control system can increase the magnetic field strength to accommodate large back driving torques during critical moments, whereas mechanical devices have fixed torque limits determined by their physical structure.
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 device effectively prevents back driving, reduces the risk of chatter and ratcheting, is simpler and lighter, and can handle large back driving torques, enhancing system reliability and reducing maintenance costs.
Implementation Method 1
The reactor spring is mounted within the housing and supplies a first spring force to the reactor plate that causes the reactor plate interior side to contact the reactor hub
Implementation Method 2
The load spring is mounted within the housing and supplies a second spring force to the brake pack that causes each brake disc to contact the different pair of the plurality of brake plates
Implementation Method 3
The brake hub exterior side contacts the brake pack when the balls are displaced a predetermined distance along the first and second cam surfaces
Data Source
AI summary
A self-activated no-back device includes a housing, an input shaft, an output shaft, a reactor hub, first grooves, a brake hub, second grooves, a plurality of balls, a reactor plate, a brake pack, a reactor spring, and a load spring. The first grooves are formed on an interior side of the reactor hub interior side, and the second grooves are formed in an interior side of the brake hub. Each second groove is aligned with a different first groove to define a plurality of groove pairs. Each ball is positioned in a different one of the groove pairs. One side of the reactor plate contacts the reactor hub. The brake pack is selectively contacted by the brake hub. The reactor spring supplies a spring force to the reactor plate, and the load spring supplies a spring force to the brake pack.