Preloaded Concentric Torque Shaft for Low-Deflection Flight Control
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Solution Overview
Problem
Conventional aircraft torque shafts experience significant axial, torsional, and lateral deflections under load, which can lead to inaccurate control surface actuation and mechanical interference due to limited envelope space in aircraft wings.
Innovation Solution
A torque shaft assembly comprising concentric tubes with axial and torsional preloads, and a composite wrap to mitigate deflections, where the second tube is inserted through the first tube with strategically aligned pin holes and preloaded to minimize deflections, and a composite wrap applied under torsional and compressive loads to enhance structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional torque shafts are used in control surface actuation assemblies, then the assembly can be constructed with standard components, but the torque shaft experiences significant axial, torsional, and lateral deflections under load leading to inaccurate control surface actuation
Solution Approach 1:
The torque shaft assembly employs concentric tubes where an inner tube is nested within an outer tube. This nested configuration allows both tubes to share the mechanical load, significantly reducing axial, torsional, and lateral deflections compared to a conventional single-tube shaft, thereby improving control surface actuation precision while maintaining structural stability
Solution Approach 2:
The invention uses a composite structure combining two separate tubes (inner and outer tubes) with different structural characteristics. This composite tube assembly provides enhanced stiffness and strength properties that mitigate deflection under load, resolving the contradiction between maintaining structural stability and achieving precise actuation
2Area of stationary object
If the envelope space within the aircraft wing is reduced to accommodate actuation assemblies, then more space is available for other mechanical systems, but the limited space causes mechanical interference and restricts torque shaft movement
Solution Approach 1:
The concentric tube configuration compactly packs the torque transmission components within a smaller radial envelope, reducing the space required within the aircraft wing while maintaining structural integrity and preventing mechanical interference with other systems
Solution Approach 2:
The nested tube design transitions from a single large-diameter shaft occupying significant radial space to concentric tubes that utilize axial spacing, effectively reducing the radial envelope and available wing space for other mechanical systems
3Manufacturing precision
If a single heavy-duty torque shaft is used to prevent deflection, then control surface actuation precision is improved, but the weight of the actuation assembly increases
Solution Approach 1:
The torque shaft is segmented into two separate concentric tubes that share the load. This segmentation allows each tube to be optimized for specific load components, achieving the required precision with lighter individual tubes compared to a single heavy-duty shaft, thereby reducing overall assembly weight
Solution Approach 2:
The composite tube assembly distributes mechanical loads across two separate structural elements, enabling weight optimization through selective material placement and cross-sectional geometry, achieving precision actuation with reduced weight compared to a monolithic heavy shaft
4Productivity
If higher operating speeds are permitted to improve productivity, then control surface response time is reduced, but vibration and deflection increase reducing safety
Solution Approach 1:
The concentric tube configuration enhances torsional and lateral stiffness, allowing the actuation system to operate at higher speeds without excessive vibration or deflection, thereby improving control surface response time while maintaining operational safety and reliability
Solution Approach 2:
The circular cross-section of the concentric tubes provides optimal torsional resistance and uniform stress distribution, enabling higher operating speeds with reduced vibration compared to non-circular sections, thus improving productivity while maintaining safety
Data Source
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AI summary
Presented are a method and apparatus for an aircraft flight surface actuation system including a motor having an output shaft. A gearbox is coupled with the output shaft, whereby a first driving force output via the motor is converted to a second driving force. A torque shaft assembly is driveably coupled with the gearbox. The torque shaft assembly includes a first tube, a second tube located at least partially through the first tube and located coaxial therewith, wherein the first tube comprises an axial preload operable to mitigate lateral deflection, and wherein the first tube comprises a torsional preload operable to mitigate torsional deflection. In addition, the aircraft flight surface actuation system includes an eccentric cam mechanism driveably coupled with the torque shaft assembly, and a flight surface coupled with the eccentric cam mechanism.