Pressure-Throttling Shutoff Valve for Hydraulic Actuator Stall Loads
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Solution Overview
Problem
Hydraulic actuators in aircraft systems face issues with kinematic devices becoming inoperable due to icing, Foreign Object Debris (FOD), or increased friction, leading to potential damage when load exceeds the actuator's sizing limit, necessitating a solution to prevent damage to the actuator and linked components.
Innovation Solution
An electrohydraulic servo valve system with a shutoff valve that passively limits the load by blocking fluid and pressure communication between the actuator and controller when excessive force is detected, preventing damage to kinematic devices and structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the load to the linear hydraulic actuator exceeds the sizing limit to overcome binding or friction in kinematic devices, then the kinematic device can be operated, but damage can occur to the kinematic device, linking mechanism, actuator, or mounting structure
Solution Approach 1:
A shear pin is introduced as an intermediary sacrificial component between the actuator and the kinematic device. The shear pin is designed to fail at a predetermined load threshold, thereby protecting the more valuable components (actuator, kinematic device, mounting structure) from damage while still allowing the system to operate when the kinematic device is temporarily stalled due to binding or friction
Solution Approach 2:
The shear pin is designed as a disposable, low-cost component that is intentionally meant to fail under excessive load conditions. After the shear pin shears, the system can be quickly reset by replacing the pin, allowing continuous operation without permanent loss of the expensive actuator or kinematic device
2Strength
If a shear pin is used to physically disconnect the actuator from the kinematic device when load exceeds threshold, then damage to components is prevented, but the kinematic device becomes inoperable following the sheering event even when the cause is temporary
Solution Approach 1:
The system discards the shear pin (a cheap, sacrificial component) to recover and protect the expensive kinematic device and actuator. After the shear pin fails, the system can be quickly reset by replacing just the pin, allowing the kinematic device to resume operation if the temporary stall condition (icing, binding) has resolved, thereby minimizing operational disruption
3Strength
If the actuator is continuously monitored and controlled to prevent excessive load, then component damage is prevented, but system complexity increases
Solution Approach 1:
The shear pin provides passive, self-service protection without requiring external monitoring or control systems. The pin automatically fails when the load exceeds its predetermined shear strength, providing inherent protection based on the physics of material failure. This eliminates the need for complex sensors, controllers, or active monitoring systems while still achieving the goal of preventing component damage
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 system effectively prevents damage to kinematic devices and structures by temporarily deactivating the actuator when excessive force is applied, ensuring safe operation and reducing potential damage during binding or seizing events.
Implementation Method 1
A first spring is between the spool and the valve housing. The first spring biases the land to an equilibrium position between the second port and the third port.
Implementation Method 2
The shutoff valve that passively limits the load by blocking fluid and pressure communication between the actuator and controller when excessive force is detected
Data Source
AI summary
A system includes a control valve with a first control port and a second control port. An actuator of the system includes a piston between an extend chamber and a retract chamber. The system also includes a shutoff valve fluidically connected between the control valve and the actuator. The shutoff valve is passively controlled by a pressure differential between the extend chamber and the retract chamber. If the pressure differential between the extend chamber and the retract chamber exceeds normal operating pressures for the actuator, the shutoff valve closes to stop pressure and flow communication between the control valve and the actuator, thereby pausing the actuator. When the pressure differential between the extend chamber and the retract chamber returns to the normal operating pressures for the actuator, the shutoff valve passively returns to an equilibrium position that allows the actuator to resume operation.