Torque Limiter With Over-Speed Governor
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Solution Overview
Problem
Existing torque limiters in aircraft flight control systems do not provide protection against over-speed conditions, where a torque tube failure leads to dangerous high rotational speeds, despite effectively preventing over-torque damage.
Innovation Solution
A torque limiter apparatus that includes an over-speed governor, which reduces the torque limit by releasing a preload setting shaft when rotational speed exceeds a limit, triggering the torque limiter to brake rotation, and is resettable using various methods such as a push button, puller tool, or pressurized fluid, allowing continued operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an over-speed governor is added to the torque limiter, then over-speed protection is achieved, but the device complexity increases
Solution Approach 1:
The patent designs the over-speed governor to utilize existing components of the torque limiter for multiple functions. The input element, output element, and braking mechanism serve both torque limiting and over-speed protection functions. The spring-loaded balls and recessed pockets mechanism is used for both torque sensing and speed sensing, reducing the need for additional dedicated components.
Solution Approach 2:
The over-speed governor mechanism is nested within the existing torque limiter structure. The flyweights are positioned within the housing of the torque limiter, and the preload setting shaft is integrated with the spring mechanism already present in the torque limiter. This nesting approach allows the over-speed function to be added without significantly increasing external dimensions or requiring separate mounting space.
2Reliability
If the preload setting shaft is released to reduce torque limit during over-speed, then over-speed protection is triggered, but the torque limiter requires resetting after activation
Solution Approach 1:
The patent incorporates a button-operated resetting mechanism that allows the operator to reset the device by simply pressing a button, without requiring disassembly or complex procedures. The button is accessible from the exterior of the housing and directly actuates the preload setting shaft to restore the spring preload and reset the flyweights to their normal positions.
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 prevents damage from over-speed conditions by integrating over-speed protection into the torque limiter, ensuring safety without requiring additional components or external controls, and allowing for reset without disassembly.
Implementation Method 1
When the rotational speed of the input element exceeds the rotational speed limit, each fly weight moves radially outward by centrifugal force, thereby releasing the preload setting shaft to permit axial displacement of the preload setting shaft relative to the structural ground.
Implementation Method 2
a torque limit setting spring having a preload which defines the torque limit
Implementation Method 3
the balls roll out of the pockets and axially displace the braking element against the spring bias into frictional engagement with grounded disc brakes to frictionally brake rotation of the input and output elements
Data Source
AI summary
An apparatus for connecting a rotational drive member to a rotational driven member brakes rotation when either the torque transmitted between the members exceeds a predetermined torque limit or the rotational speed of the drive member exceeds a predetermined rotational speed limit. The apparatus includes a torque limiter configured to actuate a braking mechanism or disconnect transmission when the torque limit is exceeded, and an over-speed governor configured to trigger the torque limiter when the rotational speed of the input element exceeds the rotational speed limit. The over-speed governor may trigger the torque limiter by reducing the torque limit of the torque limiter, or by introducing rotational drag in the apparatus to increase transmitted torque.