No-Back Device Ground Integrity Test Using Preload Springs
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Solution Overview
Problem
Existing no-back devices for ball screws used in aircraft to control airfoil surfaces cannot effectively determine operational integrity when the aircraft is on the ground and the airfoil surface is unloaded, as they require external loads to function properly.
Innovation Solution
A no-back device with a braking mechanism and preload springs that simulate external loads, allowing for the assessment of operational integrity by applying different torque thresholds and motor current comparisons when no external load is applied, ensuring the device functions correctly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a no-back device is used without external loads, then the device cannot effectively determine operational integrity, but applying external loads is not feasible when the aircraft is on the ground with unloaded airfoil surfaces
Solution Approach 1:
The patent applies preliminary action by using springs to pre-load the braking mechanism before actual operation or testing. The springs simulate the presence of external loads that would normally be applied during flight, enabling operational integrity verification to be performed in advance on the ground without requiring actual external loads or flight conditions.
2Reliability
If preload forces are applied to simulate external loads, then operational integrity can be checked on the ground, but the device complexity increases with additional springs and mechanisms
Solution Approach 1:
The patent applies universality by designing the springs to serve multiple functions: they pre-load the braking mechanism to simulate external loads, enable ground-based operational integrity testing, and maintain the no-back device's normal braking function during flight. This multi-functionality reduces the need for separate testing equipment while achieving reliable ground verification.
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
Enables the testing and validation of operational integrity of the no-back device on the ground without external loads, preventing unintended ball screw rotation and ensuring the device's functionality before flight.
Implementation Method 1
a first spring acting between the housing and the braking mechanism for exerting a first preload force on the braking mechanism
Implementation Method 2
a second spring acting between the housing and the braking mechanism for exerting a second preload force on the braking mechanism
Implementation Method 3
a braking mechanism acting between the housing and the ball screw for producing a force that resists movement of the ball screw in the direction of an aiding load
Data Source
AI summary
This invention provides an improvement in a no-back device having a ball screw connected to a variable load of reversible polarity (±L) and having a portion penetrating a housing. The device includes a braking mechanism acting between the housing and the ball screw for producing a force that resists movement of the ball screw in the direction of an “aiding” load, but does not substantially resist movement of the ball screw in the direction of an “opposing” load. The improvement broadly includes: a first spring acting between the housing and the braking mechanism for exerting a first preload force (F1) on the braking mechanism for simulating the application of an external load on the ball screw in one of the directions; whereby the apparent operational integrity of the no-back device may be checked when no external load is applied to the ball screw. In use, the apparatus performs the steps of: providing a first spring; causing the first spring to exert a first preload force (F1) on the braking mechanism; determining the actual torque (Ta) required to move the ball screw while the aircraft is on the ground; comparing the actual torque with a theoretical torque (Tt) required to move the ball screw; and inferring that the no-back device is not operating correctly if the actual torque is less than the theoretical torque; thereby to test the apparent operational integrity of the no-back device when the aircraft is on the ground.