Actuator Rate Control with Energy Absorbing Pressure Relief
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Solution Overview
Problem
Emergency doors on commercial aircraft require an actuator assembly that effectively controls the opening rate and provides energy absorption to manage loads, while also ensuring pressure relief in case of orifice blockages.
Innovation Solution
An actuator assembly with a cylindrical housing containing hydraulic fluid, a piston assembly with a piston rod and piston head having fixed orifices and a check valve, pre-loaded springs for energy storage, and a pressure relief valve mechanism that enables fluid flow when orifices are blocked, ensuring consistent spring force and controlled opening.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a piston assembly with fixed orifices is used to control the opening rate, then the opening rate control is improved, but the system becomes vulnerable to blockages that can disable fluid movement
Solution Approach 1:
The pressure relief valve is pre-configured with a spring-loaded piston that remains closed during normal operation but automatically opens when pressure exceeds a predetermined threshold, providing advance protection against complete system failure due to orifice blockages
Solution Approach 2:
The pressure relief valve acts as an intermediary safety mechanism between the restricted orifices and the hydraulic system, providing an alternative fluid path when the primary orifices become blocked, thus maintaining system reliability
2Force
If spring means are used to provide opening force, then the actuation force is improved, but the spring force may vary with temperature changes
Solution Approach 1:
The hydraulic fluid system compensates for temperature-induced spring force variations by maintaining consistent fluid pressure and flow characteristics across a wide temperature range, ensuring stable actuator performance despite environmental changes
3Strength
If a shock absorbing end stop is incorporated to prevent high load, then the protection against overload is improved, but the system complexity increases
Solution Approach 1:
The shock absorbing end stop incorporates spring means that are pre-compressed to store energy, providing cushioning protection against sudden loads or impacts before they can damage the actuator components, thereby protecting the system without requiring complex active control mechanisms
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 actuator assembly provides consistent spring force over a wide temperature range, controls the opening rate of the emergency door, decelerates the door at full extension, and ensures the door can be opened even if piston head orifice holes become plugged, thereby ensuring safe operation.
Implementation Method 1
spring means disposed in relation to the piston head, wherein the spring means includes at least one spring at the distal end of the piston rod and distal of the piston head, being preloaded in compression to create energy storage
Implementation Method 2
The piston head includes at least one orifice that permits fluidic flow between defined chambers to produce a resisting force to control the opening rate of the door
Implementation Method 3
a check valve disposed in another orifice... The check valve prevents fluid from moving through the orifice when the assembly housing is moved in tension
Implementation Method 4
The pressure relief valve is enabled by movement of the piston head against the spring means... and enabling fluid flow along a flat of the piston rod through a defined flow path from the high pressure side to the low pressure side
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
An actuator includes a piston assembly movably disposed within an assembly housing having a fixedly supported end and an opposing end that receives a movable piston assembly. The piston assembly includes a piston rod and an attached piston head having a fixed orifice as well as an orifice with a check valve to create rate control of the assembly. Hydraulic fluid is caused to move through the axially movable piston head based on compressive and tensile loads imparted to the assembly. A plurality of pre-loaded springs are configured to selectively provide pressure relief in the event the orifices of the piston become clogged, wherein the plurality of pre-loaded springs, such as disc springs, further provide an energy absorbing function of the assembly based on loading conditions.