Torque-Sensitive Locking Mechanism for Bistable Pitch Propellers
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Solution Overview
Problem
Current bistable pitch propellers rely on RPM-sensitive switching mechanisms, which can disrupt natural flight patterns and are undesirable, as they require speed changes to switch pitch angles, leading to inefficient and unattractive solutions for aircraft propulsion.
Innovation Solution
A torque-sensitive locking and release mechanism using a clutch module with metal balls and detents, where the clutch module locks at a first pitch angle and releases to switch to a second pitch angle when torque exceeds a threshold, allowing for organic pitch angle changes without relying on RPM.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If an RPM-sensitive switching mechanism is used to change pitch angles, then the pitch angle can be switched between two positions, but the mechanism disrupts natural flight patterns and requires speed changes to switch pitch angles
Solution Approach 1:
The patent changes the control parameter from RPM (rotational speed) to torque. The torque-sensitive locking and release mechanism responds to torque thresholds rather than rotational speed, allowing pitch angle switching based on aerodynamic loads and flight conditions rather than requiring specific RPM ranges. This enables more organic pitch transitions that adapt to natural flight patterns.
2Stability of the object's composition
If the bistable pitch propeller stays out of the RPM switching range to hold current pitch angle, then pitch stability is maintained, but pitch angle changes require speeding up or slowing down which interrupts natural flying
Solution Approach 1:
The patent replaces the RPM-sensitive mechanical switching mechanism with a torque-sensitive locking and release mechanism. Instead of using rotational speed sensors and control systems, the invention uses torque thresholds detected through mechanical means (such as spring-loaded detents or friction-based locking) to trigger pitch angle changes. This substitution eliminates the need to manage RPM ranges for pitch stability while maintaining stable pitch holding through torque-based locking.
3Measurement precision
If active control mechanisms (hydraulic systems) are used to adjust pitch angle, then precise pitch control is achieved, but the propeller becomes expensive and heavy
Solution Approach 1:
The torque-sensitive locking and release mechanism is a passive system that automatically responds to torque conditions without requiring external power sources, control electronics, or active intervention. The mechanism uses the aerodynamic torque itself as the control signal, with spring-loaded detents or friction elements that automatically lock or release based on torque thresholds. This self-service approach eliminates heavy hydraulic systems while maintaining precise bistable pitch control.
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
Enables bistable pitch propellers to switch between pitch angles in a more organic and efficient manner, optimizing thrust for various flight modes by maintaining the first pitch angle as a default for forward flight and switching to a second pitch angle for hovering, improving aircraft performance and reducing mechanical complexity.
Implementation Method 1
a Belleville spring, in the clutch module, to press a ball, in the clutch module, into a detent
Implementation Method 2
A torque-sensitive locking and release mechanism using a clutch module with metal balls and detents
Data Source
AI summary
A bistable pitch propeller includes a ball, a spring, and a clutch module where the clutch module has a range of rotational movement between a locked end position and a released end position. The clutch module includes a detent, where the ball sits inside and outside of the detent when the clutch module is in the locked end position and released end position, respectively. In response to an input torque and a spring force from the spring, the clutch module rotates toward the released end position and the locked end position, respectively. The bistable pitch propeller also includes an aircraft blade where the aircraft blade is at the first pitch angle and the second pitch angle when the clutch module is in the locked end position and the released end position, respectively.