Aircraft Blade Folding Device Reducing Aerodynamic Drag
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Solution Overview
Problem
Aircraft rotor blades with existing folding mechanisms suffer from significant aerodynamic drag due to the bulky design of the sleeve and yoke arrangement, leading to decreased performance and increased fuel consumption.
Innovation Solution
A folding device with a unique configuration featuring a fitting secured to the spar of the lift element, utilizing a vertical pin for rotation around a horizontal axis, reducing the frontal surface area and aerodynamic drag, while allowing for efficient folding and attachment to the hub.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a traditional sleeve with yoke arrangement is used to connect the lift element to the hub, then the blade folding functionality is achieved, but the frontal surface area increases leading to significant aerodynamic drag
Solution Approach 1:
The patent repositions the broaching axes from a vertical arrangement (perpendicular to the rotor plane) to a horizontal arrangement (parallel to the rotor plane). This dimensional change allows the fitting to connect to the sleeve without projecting vertically, thereby reducing the frontal surface area and aerodynamic drag while maintaining folding capability through horizontal broaching axes
Solution Approach 2:
Instead of having the sleeve with horizontal flanges arranged on either side of the lift element (traditional configuration), the patent inverts the arrangement by positioning the fitting's broaching axes horizontally and connecting them to the sleeve through lateral arms. This inversion eliminates the need for a bulky vertical yoke structure around the lift element
2Strength
If a yoke arrangement with flanges on either side of the lift element is used, then the structural connection is achieved, but the height in elevation increases creating significant drag
Solution Approach 1:
The patent transitions from a vertical connection architecture (yoke flanges above and below the lift element) to a horizontal connection architecture (broaching axes extending laterally). This dimensional shift reduces the elevation height of the assembly while maintaining structural integrity through the horizontal broaching mechanism and lateral arm connections
3Reliability
If connecting pins pass through flanges arranged in elevation on either side of the lift element, then the lift element is securely fixed to the sleeve, but the aerodynamic profile is degraded
Solution Approach 1:
The patent inverts the traditional attachment approach by having the fitting's broaching axes extend horizontally rather than vertically. The lateral arms connect these horizontal axes to the sleeve, with pins passing through horizontal rather than vertical flanges. This inversion maintains secure attachment while eliminating the bulky vertical profile that causes aerodynamic drag
Data Source
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AI summary
A device (20) for folding a blade (5), the device comprising a fitting (30) and a cuff (50) connected to said fitting (30). The fitting (30) has at least one horizontal pin axis (31) perpendicular to a radial direction (AX2) and a clevis (35) axially offset relative to the horizontal pin axis (31) in the radial direction (AX2). The cuff (50) has an insert (51) inserted in said clevis (35), a vertical pin (70) passing through said clevis (35) and said insert (51). The cuff (50) includes at least one horizontal fastener pin axis (55) axially offset relative to said insert (51) along the radial direction (AX2), at least one lateral arm (80) connects said horizontal pin axis (31) to said fastener pin axis (55).