Articulable Rotational Coupling for Aircraft Airfoil Control
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Solution Overview
Problem
Universal joint boots in aircraft wing airfoil surface control systems often become damaged and disengaged at large angles, allowing dirt and moisture to enter and causing corrosion and premature wear, due to their design limitations during installation and operation.
Innovation Solution
An articulable rotational coupling with a universal joint and a stop assembly that limits the articulation between shafts to a second maximum angle less than the first, using a knuckle and yokes with protrusions and pockets to prevent excessive movement and maintain lubrication, thereby preventing boot disengagement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the universal joint is designed to accommodate large angles, then the articulation flexibility is improved, but the boot becomes damaged or disengaged resulting in contamination and wear
Solution Approach 1:
The stop assembly is pre-installed on the universal joint structure before operation, establishing a predetermined angle limit that prevents the boot from being subjected to damaging large angles during normal operation
Solution Approach 2:
The stop assembly provides a counteracting mechanical constraint that prevents the universal joint from reaching angles that would cause boot damage, effectively anticipating and preventing the harmful condition before it occurs
2Reliability
If the universal joint boot is protected from large angles, then the reliability is improved, but the articulation range is reduced
Solution Approach 1:
The stop assembly modifies the operational parameters of the universal joint by establishing a maximum safe angle threshold, allowing full articulation flexibility within safe limits while preventing excursions beyond those limits that would compromise reliability
3Reliability
If the stop assembly is added to limit angles, then the boot protection is improved, but the device complexity increases
Solution Approach 1:
The protection function is segmented into a separate stop assembly component that can be independently manufactured and installed on the universal joint, rather than integrating the angle limitation into the main universal joint structure itself
Solution Approach 2:
The stop assembly acts as an intermediary mechanical element between the universal joint and the boot, providing angle limitation protection without requiring modification of the universal joint or boot themselves
Data Source
Figure 1
Figure 2A~2E
Figure 3A~3B
AI summary
An airfoil surface control system includes a movable surface. An actuator, 28, is coupled to the surface. The airfoil surface control system includes a motor, 22. A torque tube assembly, 26, operatively couples the motor, 22, and actuator, 28, and includes first and second shafts, 30, 32, coupled by a universal joint. The universal joint, 36, is configured to provide a first maximum angle between the first and second shafts, 30, 32. A stop is configured to provide a second maximum angle between the first and second shafts, 30, 32, that is less than the first maximum angle.