Self-Locking Screw Drive With Automatic Nut Retraction Lock
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Solution Overview
Problem
Screw drive systems with mechanical locking mechanisms fail to automatically and reliably fix the axial position of the nut when retracted, especially under external loads, requiring electrical power to maintain the lock.
Innovation Solution
A linear actuator system that automatically engages a mechanical lock when the nut is fully retracted, using a torque transmitting screw drive member with a sliding gear and locking segments that disengage and engage without electrical power, allowing the nut to extend and retract while maintaining positional stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a mechanical locking mechanism is added to fix the axial position of the nut, then the reliability of position fixation is improved, but the device complexity increases
Solution Approach 1:
The locking mechanism is integrated with the existing screw drive components. The locking segments are incorporated into the nut structure, and the drive member serves dual purposes: transmitting torque to rotate the screw and simultaneously engaging/disengaging the locking segments. This merging eliminates the need for separate locking components and control systems.
Solution Approach 2:
The locking mechanism operates automatically based on the operational state of the screw drive. When the drive member translates axially to engage the screw, the locking segments are automatically positioned to engage with the screw shaft. When the drive member retracts, the locking segments automatically disengage. This self-service operation eliminates the need for external control signals or additional actuators.
2Ease of operation
If electrical power is used to maintain the lock, then the ease of operation is improved, but the use of energy increases
Solution Approach 1:
The patent replaces electrical locking mechanisms with a purely mechanical solution. The locking segments engage with the screw shaft through mechanical interaction driven by the axial translation of the drive member. This mechanical substitution eliminates the need for electrical power to maintain the lock, while the automatic engagement/disengagement based on drive member position maintains ease of operation.
Solution Approach 2:
The locking mechanism transitions from a static, power-dependent lock to a dynamic, motion-driven lock. The locking state is determined by the axial position and motion of the drive member rather than by electrical power application. This dynamic approach allows the lock to engage automatically during retraction and disengage automatically during extension, eliminating continuous power consumption.
3Productivity
If the locking mechanism engages automatically during retraction, then the productivity is improved, but the device complexity increases
Solution Approach 1:
The drive member is designed to translate axially in advance of the locking engagement. As the drive member moves axially during the retraction stroke, it preliminarily positions the locking segments and the screw shaft relative to each other, preparing for automatic engagement. This preliminary action ensures that when the retraction is complete, the locking segments are already in position to engage with the screw shaft, enabling automatic locking without additional time or complexity.
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 system effectively prevents uncommanded motion of the nut by automatically locking and unlocking the nut during normal operation, ensuring axial position fixation without the need for electrical power, enhancing reliability and stability under external loads.
Implementation Method 1
a spring arranged within the nut and biased in a radial direction toward the locking segment
Implementation Method 2
a screw including a first end portion and a second end portion... a screw thread defined on an exterior surface of the second cylindrical portion
Data Source
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AI summary
A screw type linear actuator that includes a system for automatically fixing the nut in an axial position when it is retracted. When the system is commanded to operate the screw, the nut can automatically unlock. When the system screw is retracted fully, it automatically engages a mechanical lock. The lock does not require electrical power to remain engaged.