Coiled Metal Stop Pin for Low-Drag Ball Screw End Stops
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Solution Overview
Problem
Existing ball screw assemblies face challenges with costly machining and increased torque due to drag between the stop ball and screw, particularly in non-recirculating designs.
Innovation Solution
A ball screw assembly with a stop pin formed by a coiled strip of metal, which is disposed in a recess of the ball nut, providing a rotational stop for the spring assembly and reducing tilting and friction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a machined wall or fitted insert is used as an end stop in the ball nut, then the stop function is provided, but machining costs increase
Solution Approach 1:
The patent replaces expensive machined walls or fitted inserts with a simple ball-shaped stop element that can be easily manufactured and installed. This ball stop provides the necessary end stop function without requiring complex machining operations on the ball nut, thereby reducing manufacturing costs while maintaining reliability.
Solution Approach 2:
The invention extracts the end stop function from the main ball nut structure by using a separate, removable ball-shaped stop element. This separation allows the stop function to be provided independently without requiring costly machining of the ball nut itself, simplifying manufacturing while maintaining the necessary functional reliability.
2Reliability
If a radial feature or tangential feature is used as an end stop, then the stop function is provided, but torque drag increases
Solution Approach 1:
The patent employs a ball-shaped stop element with a curved surface that contacts the spring assembly. This spherical geometry allows for smooth contact and rotation without creating radial or tangential features that would generate drag. The curved surface enables the spring to pivot freely, minimizing torque drag while maintaining reliable end stop functionality.
3Ease of manufacture
If the stop pin is formed by a coiled strip of metal, then manufacturing cost is reduced, but structural strength must be maintained
Solution Approach 1:
The patent utilizes the elastic properties of the coiled strip material, changing its physical state from a rigid structure to a flexible spring element. This allows the stop pin to be formed from a coiled strip of metal that can deflect under load and return to its original position, providing both cost-effective manufacturing and sufficient structural strength through material elasticity rather than rigid geometry.
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 solution enhances efficient screw power transmission by minimizing tilting and friction, while also reducing machining costs and torque drag.
Implementation Method 1
a stop pin disposed in the first recess so that a first end of the stop pin extends inwardly into the ball groove of the inner surface of the ball nut, wherein the stop pin is formed by a coiled strip of metal
Data Source
AI summary
A ball screw having a threaded stem including a ball groove formed in an outer surface thereof, a ball nut including a central bore formed by an inner surface thereof, the inner surface defining a ball groove, a first recess extending inwardly from an end face of the ball nut and into the ball groove of the inner surface, and a stop pin disposed in the first recess so that a first end of the stop pin extends inwardly into the ball groove of the inner surface of the ball nut, wherein the stop pin is formed by a coiled strip of metal.