Cowl Door Actuator Gap Design for Thermal Expansion Compensation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional hydraulic actuators for aircraft cowl doors lack precise thermal compensation, leading to undetected fluid retention, potential leakage, and risk of cowl door opening during flight due to thermal expansion, as they require additional complex components and internal sealing which can fail.
Innovation Solution
A hydraulic actuator design with a piston rod that moves axially to accommodate thermal expansion, using the stroke of the piston rod for both actuation and thermal compensation, eliminating the need for separate seals and providing external verification of fluid displacement through a visual indicator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thermal compensation mechanism with spring or accumulator is used internally within the actuator, then thermal expansion of fluid can be compensated, but the actuator structure becomes more complex and prone to leakage at multiple sealing locations
Solution Approach 1:
The patent removes the internal thermal compensation mechanism (spring or accumulator) from the actuator and replaces it with an external compensation reservoir. This extraction eliminates the need for internal seals at the piston rod and thermal compensation component interfaces, reducing leakage points while maintaining thermal expansion compensation capability through the external reservoir connection
Solution Approach 2:
The patent introduces an external compensation reservoir as an intermediary component that mediates between the actuator and the thermal expansion compensation function. This external reservoir serves as a mediator that absorbs thermal expansion without requiring internal integration, thereby simplifying the actuator structure while preserving the compensation function
2Reliability
If multiple seals are installed within the actuator for piston rod and thermal compensation components, then sealing effectiveness is improved, but the risk of leakage increases at multiple sealing locations
Solution Approach 1:
The patent extracts the thermal compensation component from the internal actuator structure and relocates it to an external reservoir. This removal eliminates the need for additional seals at the piston rod and thermal compensation component interfaces, directly reducing the number of potential leakage points while maintaining sealing effectiveness at the remaining critical locations
3Volume of moving object
If the thermal compensation mechanism is arranged internally within the actuator, then compact design is achieved, but the mechanic cannot precisely determine when all fluid is pushed out
Solution Approach 1:
The patent uses an external compensation reservoir as an intermediary that provides visual verification capability. The reservoir's transparent or observable nature allows the mechanic to precisely determine when fluid has been completely pushed out, while the reservoir's external placement maintains a compact actuator design by separating the verification function from the actuation mechanism
4Ease of operation
If a predetermined waiting time is used after cowl door closure to assume fluid removal, then flight preparation is simplified, but undetected fluid retention may occur leading to cowl door opening during flight
Solution Approach 1:
The patent implements visual feedback through the external compensation reservoir that allows the mechanic to directly observe when fluid has been completely pushed out. This feedback mechanism replaces the unreliable predetermined waiting time assumption with real-time visual confirmation, ensuring fluid removal is actually achieved while maintaining simple flight preparation procedures
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 ensures the cowl door remains closed during flight by accommodating thermal expansion without exerting force, reduces leakage risks with fewer seals, and allows external verification of fluid removal, ensuring aircraft safety.
Implementation Method 1
the gap between the piston rod and the rod end enables an axial displacement of the piston rod that occurs due to thermal expansion of fluid remaining in the actuator
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
A cowl door actuator (16) is arranged between a head end (22) and a rod end (24) connected to a cowl door (20) in an aircraft. The cowl door (20) has a closed position and an open position, and the cowl door actuator (16) includes a piston rod (26) that is axially moveable between the head end (22) and the rod end (24). The piston rod (26) has an extended position (64) in which the piston rod (26) contacts the rod end (24) to move the cowl door (20) to the open position, and a retracted position (72) in which the piston rod (26) is axially spaced from the rod end (24). When the cowl door (20) is in the closed position, the gap (62) between the piston rod (26) and the rod end (24) enables an axial displacement of the piston rod (26) toward the extended position (64) during thermal expansion of fluid remaining in the actuator (16), such that the cowl door (20) is maintained in the closed position.