Everted Ball Screw Actuator for Compact Buckling-Resistant Motion
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Solution Overview
Problem
Conventional ball screw assemblies require significant space due to their large diameter and length, and are prone to buckling under eccentric loads due to their small effective radius, necessitating additional support structures.
Innovation Solution
An everted ball screw assembly with a hollow screw shaft and a ball cylinder featuring an internal return path, allowing for a smaller overall length and increased effective radius, which supports eccentric loads without additional support structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a conventional ball screw assembly is used, then linear motion conversion is achieved with high mechanical efficiency, but the assembly requires significant space due to large diameter and length
Solution Approach 1:
The patent inverts the conventional ball screw configuration by placing the return pathway inside the ball nut rather than externally. This inversion allows the ball screw assembly to achieve compact dimensions while maintaining high mechanical efficiency, directly resolving the contradiction between space requirements and efficiency
2Volume of moving object
If a conventional ball screw assembly with small effective radius is used, then space is reduced, but eccentric loads generate high forces causing buckling
Solution Approach 1:
The patent introduces an internal return pathway within the ball nut, utilizing the radial dimension efficiently. This dimensional reorganization allows the ball screw to achieve a larger effective radius for buckling resistance while maintaining compact overall dimensions, resolving the contradiction between space and strength
3Strength
If additional support structures are added to prevent buckling, then strength is improved, but device complexity increases
Solution Approach 1:
The patent merges the return pathway function with the ball nut structure by incorporating it internally. This integration eliminates the need for separate external support structures, achieving both buckling resistance and compact design without increasing device 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 everted ball screw assembly operates efficiently in a smaller space and withstands eccentric loads without buckling, maintaining precision and durability.
Implementation Method 1
a ball screw converts rotational motion to linear motion with high mechanical efficiency and accuracy
Implementation Method 2
a ball screw converts rotational motion to linear motion with high mechanical efficiency and accuracy
Data Source
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AI summary
Linear actuators driven by everted bail screw assemblies are described herein. In some examples, the everted ball screw assembly includes a hollow screw shaft with internal threads, a ball cylinder concentrically positioned therein and having external threads, and a plurality of balls sized to fit m a substantially contiguous series along a working pathway that is defined by the space between the internal and external threads. One or more limiters prevent the ball cylinder from rotating. A motor rotates the hollow screw7 shaft, thereby driving the balls along the pathway and imparting linear motion to the bail cylinder, which is coupled to a connecting rod for actuating a load. The ball cylinder in some examples includes an internal return path w7ith scoop elements that are sized and shaped to guide the bails into the internal return path and then back onto the working pathway.