Linear Actuator Self-Locking via Segmented Screw Pitches
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Solution Overview
Problem
Existing linear actuators used in prosthetic or orthotic joints face challenges in balancing self-locking properties with the speed of linear displacement, as smaller thread pitches improve self-locking but reduce axial motion speed.
Innovation Solution
The actuator design incorporates an electric motor with stator windings, an elongate rotor, and an elongate magnet, featuring two screws with different thread pitches and diameters to enhance self-locking while maintaining axial displacement efficiency, eliminating the need for bearings and optimizing friction surfaces to screws and nut threads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If smaller thread pitch is used, then self-locking properties are improved, but speed of linear motion is reduced
Solution Approach 1:
The actuator is divided into two separate screw-nut assemblies (first and second screws with respective nuts) that operate in parallel. This segmentation allows each screw to have different thread pitches optimized for different functions: one screw prioritizes self-locking with smaller pitch, while the other prioritizes speed with larger pitch, thereby resolving the contradiction between reliability and speed.
Solution Approach 2:
Different thread pitches are applied to different screws within the same actuator system. The first screw uses a smaller thread pitch for enhanced self-locking properties, while the second screw uses a larger thread pitch for faster linear motion. This local differentiation of quality parameters allows simultaneous optimization of both contradictory requirements in different parts of the system.
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 achieves improved self-locking properties without sacrificing axial response, allowing for efficient and balanced locking force and speed of linear displacement, suitable for prosthetic joints and other applications.
Implementation Method 1
an electric motor having stator windings, an elongate rotor
Implementation Method 2
The elongate magnet is operatively coupled to the rotor and radially interposed between the first and second screws and the motor
Implementation Method 3
The interaction of the threads of the screw and nut can generate a friction force that inhibits rotation of the screw and nut relative to each other
Data Source
AI summary
Linear actuators that allow for improved self-locking properties without sacrificing axial response are provided. A linear actuator can have two screws extending from opposite ends of the actuator. The screws are joined by and threadably coupled to an elongate rotating nut. An elongate magnet is disposed around and coupled to the nut, and a stator including coils surrounds the magnet and nut. The magnet and nut are not axially fixed with respect to the stator. Rotation of the nut causes axial displacement of both screws, causing the screws to move closer together or farther apart. A pitch of the screw threads can be selected to enhance self-locking properties.