Linear Actuator Free-Fall Decoupling for Screw Jamming Safety
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Solution Overview
Problem
Linear actuators with screw structures often experience jamming due to sticking between the screw member and the operating nut, leading to halted operation and potential safety issues, especially in critical applications like aircraft landing gear.
Innovation Solution
A linear actuator design incorporating a free fall function, where the piston-rod member can decouple from the operating nut and freely fall in the direction of applied load when jamming occurs, utilizing a key member and rotary roller members to facilitate this movement, and a load-locking unit to secure the piston-rod member in its maximum extended position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the screw member and operating nut are tightly coupled to prevent slippage, then the transmission reliability is improved, but the risk of jamming due to sticking increases
Solution Approach 1:
The connection between the piston-rod member and operating nut is segmented into two states: coupled state (for normal operation) and decoupled state (for free fall). The key member creates separable connection portions that allow the system to switch between these states, enabling the piston-rod member to be connected during normal operation and disconnected during jamming events.
Solution Approach 2:
The connection state between the piston-rod member and operating nut is made dynamic rather than static. The key member with its elastic support allows the connection to adapt between coupled and decoupled states based on operating conditions, enabling automatic response to jamming events while maintaining tight coupling during normal operation.
2Manufacturing precision
If the piston-rod member is firmly connected to the operating nut, then the operational precision is improved, but the ability to freely fall during jamming is reduced
Solution Approach 1:
The connection is segmented into coupled and decoupled states through the key member structure. During normal operation, the key member engages with the operating nut to ensure precise movement. During jamming, the connection portions can separate, allowing free fall while maintaining structural integrity.
Solution Approach 2:
The connection parameter between piston-rod member and operating nut changes from fixed (coupled) to variable (decoupled) based on operating conditions. The elastic support of the key member allows the connection stiffness to change, enabling both precise operation and free fall capability.
3Reliability
If a decoupling mechanism is added to enable free fall, then the safety during jamming is improved, but the device complexity increases
Solution Approach 1:
The key member serves multiple functions: it connects the piston-rod member to the operating nut during normal operation, allows decoupling during jamming events, and provides elastic support for both states. This multi-functionality reduces the need for separate dedicated components for each function.
Solution Approach 2:
The key member is nested within the piston-rod member structure, with the elastic support integrated into the key member assembly. The connection portions are nested within the cylindrical chamber, allowing the decoupling mechanism to be compact and integrated rather than additive.
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
Ensures the piston-rod member can achieve its maximum stretched length even in jammed conditions, enhancing safety and reliability, particularly for applications like aircraft landing gear by preventing disasters due to malfunction.
Implementation Method 1
a key member (700) protruding from an outer circumferential surface of the operating nut (300), and located to be caught by an inner circumferential surface of the nut receptacle (411), when in an engaged position in which the piston-rod member (400) is coupled to the operating nut (300); and an elastic support (800) elastically supporting the key member (700)
Implementation Method 2
the piston-rod member (400) being moved back and forth integrally with the operating nut (300); wherein when the operating nut (300) and the screw member (200) are stuck to and rotate integrally with each other, the piston-rod member (400) is decoupled from the operating nut (300) to advance in a direction in which load is applied
Data Source
AI summary
A linear actuator having a free fall function. The linear actuator moves a piston-rod member back and forth using torque of a rotary motor. Here, the piston-rod member is disposed within a portion of a cylinder body to be movable back and forth. In the event of jamming in which the piston-rod member is stopped due to sticking between an operating nut and a screw member, the piston-rod member is caused to freely fall in a direction in which load is applied. This can consequently obtain the maximum stretched length of the piston-rod member, thereby providing safety in an emergency.