Rotor Blade Connection Means with Longitudinal Bolt Alignment
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Solution Overview
Problem
Conventional rotor blade connections to rotor hubs experience unfavorable stress distribution and delamination due to offset bolt arrangements, leading to bulky and drag-prone designs that compromise aerodynamic performance and safety.
Innovation Solution
The connection means feature two bolts aligned along the rotor blade's longitudinal axis, with an intermediate beam element and tapered transitions to optimize stress distribution, allowing for a narrower, more aerodynamic design with improved torsional and lead-lag stiffness, and an optional third bolt for enhanced safety and damping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If two bolts are arranged side by side offset from the longitudinal axis, then the rotor blade connection can be achieved, but unfavorable stress distribution and delamination occur leading to bulky connection means with increased aerodynamic drag
Solution Approach 1:
The patent applies asymmetry by transitioning from a symmetric offset bolt arrangement to an asymmetric alignment where bolts are positioned along the longitudinal axis. This asymmetric repositioning optimizes the force flow path, eliminating delamination issues while reducing the cross-sectional area of the connection means, thereby reducing aerodynamic drag without compromising strength
Solution Approach 2:
The patent inverts the conventional bolt arrangement approach by placing bolts along the longitudinal axis rather than offset from it. This inversion fundamentally changes the stress distribution pattern, transforming the unfavorable delamination-prone stress flow into a favorable axial force flow that maintains strength while minimizing connection cross-section and aerodynamic drag
2Strength
If two bolts are arranged side by side offset from the longitudinal axis, then the rotor blade connection can be achieved, but reinforced connection means with bigger cross sections are required
Solution Approach 1:
The asymmetric longitudinal alignment of bolts along the rotor blade's longitudinal axis creates an optimized force flow path that concentrates stresses favorably. This eliminates the need for reinforced connection means with larger cross-sections, as the aligned arrangement naturally distributes loads more efficiently through the connection means, reducing the required volume while maintaining strength
Solution Approach 2:
By inverting the conventional offset arrangement to a longitudinal axis alignment, the patent fundamentally changes how forces are transmitted. This inversion allows the connection means to be smaller in cross-section because the axial alignment creates a more efficient load path that requires less material to achieve the same strength
3Stress or pressure
If bolts are aligned along the longitudinal axis, then favorable force flow and optimized stresses are achieved, but each bolt must carry full centrifugal load independently requiring higher edge distances
Solution Approach 1:
The patent applies local quality by optimizing the bolt arrangement specifically along the longitudinal axis where the centrifugal forces act. This localized optimization creates favorable force flow in the critical stress regions, and the increased edge distances provide localized reinforcement zones that allow each bolt to independently handle full centrifugal loads while maintaining overall stress optimization
Data Source
AI summary
A connection means (1) for mounting a rotor blade (2) to a rotor hub, particularly for mounting a rotor blade (2) to a rotor hub of a helicopter, with at least two bolts (4, 5) inserted vertically relative to a main plane of said rotor blade (2) into an end (7) of said rotor blade (2) that is generally directed towards the rotor hub. At least two bolts (4, 5) are arranged distant from each other along a longitudinal axis (6) of said rotor blade (2) to said rotor hub.