Telescopic Actuator with Controllable Nut Release
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Solution Overview
Problem
Telescopic actuators used in aircraft landing gear and similar applications often fail to shorten under load when the drive mechanism is faulty or power is lost, preventing free movement of the undercarriage due to the inability to release the nut from the rod without a reversible screw/nut connection.
Innovation Solution
A telescopic actuator design featuring a nut retained by controllable claws and a locking sleeve that can be rotated from a locking to a release position, allowing the rod to shorten under load even without functional drive means, using a rotatable locking sleeve and actuating member to control the release of the nut.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional telescopic actuator with a fixed nut is used, then the actuator maintains structural integrity and prevents unintended movement, but it cannot shorten under load when the drive mechanism fails or power is lost
Solution Approach 1:
The nut is designed with movable claws that can dynamically change their state between locked and released positions. The claws are spring-loaded to maintain engagement with the rod during normal operation, but can be actively released when needed, allowing the actuator to adapt its behavior based on operational requirements rather than remaining statically fixed.
Solution Approach 2:
A locking sleeve is introduced as an intermediary component between the claws and the rod. This sleeve can rotate to either lock the claws in their engaged position or allow them to release from the rod. The locking sleeve acts as a mediator that controls the interaction between the nut and rod, enabling controlled shortening under load while maintaining structural integrity during normal operation.
2Adaptability or versatility
If a reversible screw/nut connection is used to allow shortening under load, then the actuator can free-move during failure, but the device complexity increases and reversibility is not always possible
Solution Approach 1:
The connection between the nut and rod is segmented into discrete engagement points through the claw design. Instead of a continuous reversible thread connection, the claws provide discrete mechanical engagement points that can be selectively locked or released. This segmentation simplifies the release mechanism compared to full reversibility while achieving the desired functionality.
Solution Approach 2:
The locking mechanism uses a simplified copying approach where the locking sleeve replicates the locking function through rotational positioning rather than requiring a complex reversible threading mechanism. The sleeve's angular position copies the desired locked or released state without needing the full reversibility of a screw/nut connection.
3Ease of operation
If the lead screw is axially releasable to allow free sliding, then the rod can move freely under load, but the actuator cannot prevent unintended shortening during normal operation
Solution Approach 1:
The claws are pre-loaded by springs to maintain engagement with the rod before any failure occurs. This preliminary locking action ensures the actuator maintains its length under normal operational conditions. Only when the locking sleeve is actively rotated to the release position do the claws disengage, allowing shortening under load. The preliminary action of locking prevents unintended movement while enabling controlled release when needed.
Data Source
Figure 1~2
Figure 3
Figure 4~7
AI summary
The invention relates to a telescopic actuator comprising a body (1) defining a cylindrical cavity with longitudinal axis (X); a rod (3) mounted for telescopic sliding within the cylinder along said axis; a nut (7) fixed to the rod; a leadscrew (4) mounted on the cylinder to extend and rotate about said axis (X) and cooperate with the nut such that a rotation of the leadscrew causes a telescopic displacement of the rod within the cylinder; and means (8, 9, 10) for driving the leadscrew in rotation. According to the invention, the nut is mounted on the rod and is axially retained thereon by retaining means (12, 13, 14; 30 to 38) which are controllable to axially release the nut from the rod.