Helicopter Rotor Constant Velocity Universal Joint
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Solution Overview
Problem
Helicopter rotors, particularly two-bladed and three-bladed rotors, face challenges with torsional oscillations and loss of control during low-g or zero-g flight due to complex mechanical systems and non-homokinetic transmission, leading to vibrations and instability.
Innovation Solution
A constant velocity universal joint using concentric cardanic rings and bisector devices maintains a homokinetic plane, ensuring constant velocity transmission between the rotor hub and driving shaft, reducing oscillations and enhancing control authority with a simplified, robust, and adaptable design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a simple gimbal central hinge of flapping is used in two-bladed rotors, then the rotor can achieve flapping motion and disk inclination control, but torsional oscillating stresses are induced on the driving shaft at twice the rotational frequency
Solution Approach 1:
The patent introduces an intermediate constant velocity universal joint mechanism between the driving shaft and rotor hub. This intermediary system includes a driving shaft yoke, constant velocity universal joint, and driven shaft yoke that collectively mediate the power transmission while eliminating the harmful torsional oscillations generated by simple gimbal hinges.
Solution Approach 2:
The patent replaces the simple non-homokinetic gimbal hinge mechanical system with a constant velocity universal joint mechanism. This substitution transforms the mechanical power transmission system to achieve homokinetic motion, thereby eliminating the torsional oscillating stresses that occur at twice the rotational frequency in traditional systems.
2Device complexity
If traditional non-homokinetic transmission systems are used, then the rotor hub can be connected to the driving shaft, but torsional oscillations propagate to the helicopter structure causing vibrations
Solution Approach 1:
The patent substitutes the traditional non-homokinetic transmission system with a constant velocity universal joint mechanism. This replacement eliminates the generation of torsional oscillations at twice the rotational frequency, preventing vibration propagation to the helicopter structure while maintaining the necessary rotational power transmission.
3Object-generated harmful factors
If a constant velocity universal joint is implemented, then homokinetic transmission is achieved eliminating torsional oscillations, but the device complexity increases with additional components
Solution Approach 1:
The patent segments the constant velocity universal joint into distinct modular components: a driving shaft yoke with transverse pins, a constant velocity universal joint with needle bearings, and a driven shaft yoke with longitudinal pins. This segmentation allows for easier manufacturing, assembly, and maintenance while achieving the benefit of homokinetic transmission.
Solution Approach 2:
The patent employs dynamic elements including needle bearings within the constant velocity universal joint and pins that can rotate within their respective yokes. These dynamic components enable the mechanism to accommodate angular misalignments and maintain smooth homokinetic power transmission throughout the rotational cycle.
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
The solution effectively reduces torsional oscillations and maintains rotor control during varying flight conditions, improving stability and reducing the complexity of mechanical components, making it suitable for both two-bladed and three-bladed rotors.
Implementation Method 1
the homokinetic transmission of the rotational motion and the driving torque is obtained by means of rigid and non-resilient elements
Implementation Method 2
a hub, connected to that driving shaft by means of two concentric cardanic rings housed inside a cavity of the hub itself
Implementation Method 3
at least one alignment device said 'bisector', preferably two bisectors, to maintain the common axis of the pins connecting the two cardanic rings in a plane called 'homokinetic'
Implementation Method 4
in the yokes the blades are fixed by means of horizontal eccentric hinges of known type and commonly called 'taper'
Data Source
Figure 1
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AI summary
The invention relates to a constant velocity universal joint for each type of transmission and in particular for helicopters with rotors called gimballed, in which the hub (2) of a rotor equipped with blades (7) is supported on a transmission shaft (1), said "mast", by means of a cardan's suspension composed of two concentric rings ( 5A and 5B), a first inner ring (5A) has a revolute connection to two opposite pins (31) of the carrier (3) connected to transmission shaft (1) and a second outer ring (5B) has a revolute connection to two opposite pins (22) of the hub (2).The two concentric rings are also interconnected by a pair of swivel opposite pins (542), in quadrature with respect to the pins (31) connected to the transmission shaft and to the pins (22) of the hub, whose common axis (00) is stably maintained in a plane, said homokinetic, which bisects the angle between the axis of rotation of the hub (2) and the axis of rotation of the transmission shaft (1), by means of at least one (but preferably two) devices (6), original and improved, said bisectors, which are connected both to the transmission shaft and to hub, thus obtaining a homokinetic transmission of rotational motion between said transmission shaft (1) and said hub (2), to which the blades (7) are fixed irrespective of the angle of inclination the hub assumes with respect to the drive shaft.