Shrinking Shock Strut for Landing Gear
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Solution Overview
Problem
Existing aircraft landing gear systems require heavy mechanical linkages and high hydraulic fluid flow rates to shrink struts during retraction, which can increase the landing gear envelope and are not independent of the retract actuator, limiting space efficiency and flexibility.
Innovation Solution
A compact shrinking shock strut system that operates independently of the retract actuator, using a transfer device to 'step-down' hydraulic pressure and provide a higher hydraulic fluid flow rate, eliminating the need for heavy mechanical linkages and integrating a hydraulic compensator to maintain pressure and fluid volume.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If heavy mechanical linkages are used to exert axial shrinking force on the strut, then the strut can be shrunk during retraction, but the landing gear envelope increases and the system becomes more complex
Solution Approach 1:
The patent replaces heavy mechanical linkages with a hydraulic system. A hydraulic actuator uses fluid pressure to generate the axial shrinking force on the strut, eliminating the need for complex mechanical linkage systems while achieving the same shrinking function with reduced space requirements
Solution Approach 2:
The patent employs a hydraulic system where hydraulic fluid is directed to an actuator that converts hydraulic pressure into mechanical force for shrinking the strut. This hydraulic approach provides a compact, high-force solution that reduces the landing gear envelope compared to mechanical linkage systems
2Length of moving object
If high hydraulic fluid flow rates are used to shrink the strut, then the shrinking function is achieved, but the hydraulic system requirements increase and the system becomes less compatible with standard aircraft hydraulic systems
Solution Approach 1:
The patent changes the hydraulic system parameters by using a hydraulic actuator with a large piston area that converts standard hydraulic pressure into high force. This allows the system to achieve strut shrinking with conventional hydraulic flow rates rather than requiring high flow rates, making it compatible with standard aircraft hydraulic systems
Solution Approach 2:
The patent applies local quality by designing the hydraulic actuator with a large piston area at the point where force is needed, allowing the conversion of moderate flow rate at high pressure into the high force required for strut shrinking, thus maintaining compatibility with standard hydraulic systems
3Extent of automation
If the shrinking system is mechanically linked to the retract actuator, then the system is integrated, but the shrinking operation cannot be controlled independently from retraction
Solution Approach 1:
The patent segments the landing gear system into independent functional modules: the retract actuator for retraction/deployment and the hydraulic actuator for shrinking. This segmentation allows each function to be controlled independently through separate hydraulic control valves, enabling independent operation while maintaining system integration
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 efficient and compact strut shortening without increasing the landing gear envelope, allowing for independent operation and reduced hydraulic demand, while maintaining strut length control and fluid volume stability.
Implementation Method 1
The transfer device transfers hydraulic fluid to the strut shrink chamber independent of movement of the retract actuator
Implementation Method 2
the pressurized gas that was transferred to the transfer cylinder drives the transfer fluid from the strut shrink chamber back into the transfer cylinder. As the transfer fluid exits the strut shrink chamber, the pressurized gas returns to the strut from the transfer cylinder and causes the strut to return to its extended length
Data Source
Figure 1A~1B
Figure 2
Figure 3A~3B
AI summary
A shrinking shock strut (11) system for an aircraft landing gear (10) having a retract actuator (17) that is moveable in length to deploy or retract the landing gear (10), that includes a shrink strut (11) and a transfer device. The shrink strut (11) may be compressed in length for stowage in the fuselage. The transfer device may be in closed fluid communication with the strut shrink (11) for transferring and receiving hydraulic fluid to and from the strut shrink (11). When actuated by an aircraft hydraulic system independent of any motion of the retract actuator (17), the transfer device may drive hydraulic fluid to the strut shrink thereby compressing or shrinking the shrink strut (11) to a partially compressed length.