Actuator Transmission Structure With Ratchet-Guided Screw Nut
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Solution Overview
Problem
The existing screw nut structure in actuators experiences excessive frictional force between the screw nut and the screw rod, leading to impaired axial movement due to cold contraction and poor thread precision, causing the screw nut to fail in driving the inner tube outward or inward.
Innovation Solution
A transmission structure incorporating a screw nut with extended pawls and a ratchet guiding sleeve, where the pawl is blocked and retained by a ring ratchet to maintain controlled frictional force, allowing smooth extension and quick inward retraction of the inner tube.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the screw nut is attached to the inner tube via frictional force, then the screw nut can drive the inner tube to extend outward, but the frictional force between the screw nut and the screw rod becomes greater than that between the screw nut and the inner tube, causing the screw nut to be unable to move vertically on the screw rod
Solution Approach 1:
A ratchet guiding sleeve is introduced as an intermediary component between the screw nut and the outer tube. The ratchet guiding sleeve includes a ring ratchet that interacts with a pawl on the screw nut, and a track slot that guides the screw nut's axial movement. This intermediary structure controls the frictional force between the screw rod and screw nut while maintaining reliable driving capability, preventing the screw nut from sticking due to excessive friction.
2Reliability
If the thread processing precision is poor or cold contraction occurs, then the frictional force between the screw nut and the screw rod increases, but this causes the screw nut to fail in driving the inner tube outward or retracting inward
Solution Approach 1:
The ratchet guiding sleeve acts as a mediator that decouples the thread engagement reliability from the axial movement responsiveness. The ring ratchet and pawl mechanism ensures reliable unidirectional locking, while the track slot provides smooth guiding for axial movement. This allows the system to maintain reliable thread engagement even with poor processing precision or temperature variations, while ensuring swift response for both extension and retraction operations.
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
This configuration stabilizes the screw nut's ability to drive the inner tube outward while enabling swift inward retraction, preventing excessive friction and ensuring smooth movement and one-way quick release in the actuator and transmission structure.
Implementation Method 1
the frictional force between the lead screw and the screw nut may be maintained within a predefined value
Implementation Method 2
the ratchet guiding sleeve having a ring ratchet disposed on an inner circumference thereof and a plurality of track slots disposed on an outer circumference thereof, and the at least one pawl abutting against the ring ratchet
Implementation Method 3
The screw nut has a hollow shape and the screw rod penetrates therethrough. The inner side of one end of the screw nut is formed of threads for engaging with the screw rod. The motor is connected to the screw rod and drives the screw rod to rotate. When the screw rod rotates, it drives the screw nut to move axially
Implementation Method 4
since the aforementioned screw nut is attached to the inner tube via frictional force
Data Source
AI summary
An actuator and a transmission structure thereof. The transmission structure (3) includes a screw nut (31) and a ratchet guiding sleeve (32). The screw nut (31) includes one or a plurality of pawls (311). The ratchet guiding sleeve (32) is mounted on the screw nut (31), and the screw nut (31) is able to rotate relative to the ratchet guiding sleeve (32). The ratchet guiding sleeve (32) includes a ring ratchet (321) disposed on an inner circumference thereof and a plurality of track slots (322) disposed on an outer circumference thereof. One or a plurality of pawls (311) abut against the ring ratchet (321), thereby achieving the effect of smooth movements of the actuator (10) and the transmission structure (3).