Rotary-to-Linear Actuator with Ball Screw and Backdrive Locking
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Solution Overview
Problem
Existing rotary to linear (RTL) actuators in brake systems face inefficiencies due to self-locking threading, which hinders the conversion of rotational movement into linear movement and allows backdrive, resulting in incomplete clamping forces.
Innovation Solution
The implementation of a nut and spindle combination without self-locking threading, utilizing a lead screw to self-lock and prevent backdrive, and incorporating ball bearings to enhance movement efficiency, with a secondary nut for self-locking to maintain clamping force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If self-locking threading is used in the nut and spindle, then backdrive is prevented, but the efficiency of converting rotational movement into linear movement decreases
Solution Approach 1:
The patent divides the nut into two separate components: a first nut with self-locking threading that prevents backdrive, and a second nut without self-locking threading that efficiently converts rotation to linear movement. This segmentation allows each component to specialize in one function, resolving the contradiction between reliability and productivity
Solution Approach 2:
The patent introduces a ball screw as an intermediary mechanism between the drive shaft and the piston. The ball screw provides efficient rotational to linear movement conversion without self-locking, while the separate first nut with self-locking threads handles the backdrive prevention function, mediating between the conflicting requirements
2Productivity
If self-locking threading is removed from the nut and spindle, then efficiency of movement conversion improves, but backdrive occurs causing incomplete clamping force
Solution Approach 1:
The patent segments the nut into two distinct parts with different threading characteristics. The second nut has non-self-locking threads for efficient movement conversion, while the first nut has self-locking threads to prevent backdrive and maintain clamping force, thus resolving the contradiction between productivity and reliability
Solution Approach 2:
The patent merges the functions of two different nut types into a single integrated assembly. The first nut with self-locking threads and the second nut without self-locking threads work together in the same mechanism, combining the benefits of both designs to simultaneously achieve high efficiency and reliable clamping force maintenance
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 allows for efficient linear movement of the piston during clamping while preventing backdrive, ensuring consistent clamping force and improved efficiency in brake systems.
Implementation Method 1
frequently utilizing one or more ball bearings to improve movement
Implementation Method 2
the threading of the lead screw self-locks with the internal threading of the spindle to prevent backdrive
Data Source
AI summary
A rotary to linear actuator comprising: (a) a nut having a threading; (b) a spindle having an external threading and positioned at least partially within the nut; and (c) a drive shaft in communication with the nut to rotate the nut; wherein rotation of the drive shaft rotates the nut, and the threading of the nut engages the external threading of the spindle to move the spindle axially away from the drive shaft to drive a piston.