Variable-Pitch Aircraft Propeller With Shear-Release Counterweight
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Solution Overview
Problem
Existing aircraft turbine engine propeller systems with variable-pitch vanes and counterweight devices are prone to mechanical and aerodynamic imbalances due to blockages caused by seizures in the counterweight device, leading to potential in-flight incidents and performance limitations.
Innovation Solution
Incorporation of shear bolts that disengage the toothed wheel portion from the base in case of counterweight device failure, preventing mechanical and aerodynamic imbalances by allowing the pitch actuation kinematic to be freed, thus protecting the variable pitch vane and its base.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a counterweight device with conical pinion gearing and bearings is used to control vane pitch, then the vane can be returned to the feathered position in normal operation, but the device may seize and block the pitch setting mechanism
Solution Approach 1:
The patent divides the counterweight device into separate functional components: the counterweight assembly, the conical pinion, the toothed wheel portion, and the base with shear section. This segmentation allows the shear section to fail independently, preventing complete blockage of the pitch setting mechanism while maintaining the counterweight function.
Solution Approach 2:
The patent extracts the shear section as a separate, sacrificial element from the main counterweight device. This shear section is designed to fail first under excessive load, removing the blocking force from the pitch setting mechanism while leaving the counterweight and other components intact and functional.
2Reliability
If a shear section is added to the counterweight device to prevent blocking, then the pitch setting mechanism remains operational after seizure, but the device complexity increases
Solution Approach 1:
The shear section acts as an intermediary element between the counterweight device and the pitch setting mechanism. It mediates the force transmission, allowing normal operation while providing a controlled failure mode that protects the main mechanism from blocking when seizure occurs.
3Device complexity
If conventional counterweight devices are used, then the structure is simple, but seizure of the conical pinion or bearings blocks the entire pitch setting mechanism
Solution Approach 1:
The shear section is designed beforehand as a sacrificial element that will fail under excessive load conditions. This prior cushioning approach ensures that when seizure occurs, the failure is already planned and contained to the shear section, preventing propagation to the main pitch setting mechanism.
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
Prevents mechanical and aerodynamic imbalances by ensuring the pitch change mechanism remains operational even in the event of counterweight device failure, enhancing safety and performance of the turbine engine.
Implementation Method 1
the or each shear bolt comprises a first head bearing on said toothed wheel portion, and a first body which passes through first orifices in this portion and in the base; said first body comprises a first segment threaded and screwed into the first orifice of the base, which is tapped, and a second segment defining a smaller section of the first body
Implementation Method 2
The movable shaft of the counterweight device is connected to a weight and therefore to a conical pinion, which is meshed with a portion of the toothed wheel that is secured in rotation with the vane
Implementation Method 3
The shaft is generally centred and guided in rotation by at least one bearing, for example a ball bearing
Implementation Method 4
the feathering is achieved by direct counterweight devices whose inertia, which is much greater than that of the propeller vanes, must ensure that the return of the latter to the pre-defined feathered position
Data Source
AI summary
An assembly for a propeller of a turbine engine of an aircraft is provided. The assembly includes a variable-pitch vane having a blade connected to a root, the vane having a longitudinal axis aligned with a vane pitch axis which passes through the root, a base rigidly connected to the vane to rotate together with the vane about the axis and connected to a portion of a toothed wheel extending around the axis, and a counterweight device having a shaft which can rotate about an axis substantially perpendicular to the axis, the shaft being connected to at least one flyweight and to a pinion meshed with the toothed wheel portion. The toothed wheel portion can be attached to the base by at least one shear pin.