Propeller Shaft Locking Finger for Passive Windmilling Control
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Solution Overview
Problem
Vertical take-off aircraft propellers experience instability and energy inefficiency due to windmilling, which generates unpredictable forces and increases aerodynamic drag, and existing solutions like engine torque locking consume energy and are inefficient.
Innovation Solution
A locking system comprising a housing and indexing element that limits rotational movement to a predetermined sector, engaging only when the assemblies are in a rest position, and can be passively locked and unlocked, reducing energy consumption and instability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If engine torque is applied to lock the propeller, then propeller stability is improved, but energy consumption increases
Solution Approach 1:
The locking system uses the propeller's own windmilling rotation to drive the indexing element out of the housing, achieving automatic unlocking without external energy input. The system serves itself by converting the harmful windmilling motion into the unlocking mechanism's driving force.
Solution Approach 2:
The patent replaces the active engine torque locking mechanism with a passive mechanical indexing system. The indexing element and housing interact through mechanical engagement/disengagement based on propeller rotation, eliminating the need for continuous energy input from the engine.
2Loss of energy
If propeller is locked in position, then aerodynamic drag is reduced, but device complexity increases
Solution Approach 1:
The locking system is segmented into distinct functional components: the housing with engagement surface, the indexing element with complementary geometry, and the return device. This segmentation allows each component to perform its specific function simply, reducing overall system complexity while maintaining effectiveness.
Solution Approach 2:
The locking and unlocking functions are extracted from the main propeller drive system and implemented as a separate, independent mechanical indexing mechanism. This extraction simplifies the integration with the existing propeller system and reduces the complexity burden on the primary drive train.
3Stability of the object's composition
If indexing element is inserted into housing, then rotational movement is limited improving stability, but the system requires additional components
Solution Approach 1:
The housing serves multiple functions: it provides structural support for the propeller assembly, defines the engagement surface for the indexing element, and guides the return device. The indexing element simultaneously provides the locking engagement and acts as a cam to drive the return mechanism. This merging of functions reduces the number of separate components needed.
Solution Approach 2:
The engagement surface geometry on both the housing and indexing element serves dual purposes: it limits rotational movement to the predetermined sector for stability, and it provides the mechanical interface for both locking engagement and automatic unlocking through windmilling rotation.
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 proposed locking system effectively mitigates instability and energy inefficiency by allowing passive locking and unlocking of the propeller, reducing variability in forces applied and minimizing aerodynamic drag, thereby enhancing aircraft stability and energy efficiency.
Implementation Method 1
the return device comprises a support spring for pushing one of the indexing element and the housing towards the other, and a calibration screw in cooperation with the support spring to modify a stiffness of the return device
Implementation Method 2
the indexing element comprises a rolling element capable of being introduced into the housing
Data Source
Figure 1A~1B
Figure 1C~1D
Figure 2A~2B
AI summary
Disclosed is an aircraft comprising a primary propeller (100) rotated by a motor (200), the motor having a first assembly (210) and a second assembly (220) rotatable relative to one another about an axis of rotation (300), the primary propeller being constrained to rotate with one of the first assembly and the second assembly, the first assembly and the second assembly being movable in translation relative to one another in a translation direction (320) defined by the axis of rotation, between a rest position and a service position, characterised in that the aircraft comprises a locking system (400), comprising a recess (420, 421, 422) and an indexing element (410, 410'), the recess being formed in one among the first assembly and the second assembly, the indexing element being rigidly attached to the other among the first assembly and the second assembly, the locking system having an engaged configuration in which the indexing element is at least partially inserted in the recess, and a free configuration in which the indexing element is not at least partially inserted in the recess, the locking system being configured such that in the engaged configuration, the rotation of the first assembly relative to the second assembly is limited to an angular sector less than 5°, in that the locking system can only be in the engaged configuration when the first assembly and the second assembly are in the rest position, and in that the locking system is configured so as to pass from the engaged configuration to the free configuration when the motor applies a rotational torque greater than a threshold torque value on the first assembly or on the second assembly.