Ball Screw Return Passage Oval Cross Section Spacer Jamming
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In ball screws, spacers between neighboring balls often contact the inner periphery of the return path, leading to interference and jamming, especially in miniaturized designs where the reduced radius of curvature exacerbates the issue, and existing solutions from linear guideway technologies are not applicable due to structural differences.
Innovation Solution
A circulation passage structure with a return passage having an oval cross section, featuring non-concentric inner and outer guiding surfaces with a smaller inner curve length than half the circumference, allowing spacers to pass without contacting the inner guiding surface, and adjusting the curvature to accommodate the spacer's inward displacement, ensuring smooth passage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the radius of curvature of the return path is reduced for miniaturization, then the ball screw can be miniaturized and lightweighted, but the spacer will contact the inner periphery of the return path causing interference and jamming
Solution Approach 1:
The patent applies asymmetry by making the cross-section of the return passage oval-shaped rather than circular, with the inner curve having a smaller radius than the outer curve. This asymmetric geometry creates sufficient clearance between the spacer and the inner guiding surface while maintaining a compact overall size, thereby preventing spacer contact and jamming in miniaturized ball screws.
Solution Approach 2:
The patent changes the geometric parameters of the return passage by specifying that the inner curve length is less than half the circumference of the cross-section and that the inner and outer curves are non-concentrically arranged. These parameter changes optimize the space utilization and ensure smooth spacer passage while maintaining miniaturization.
2Ease of operation
If the size of the spacer is reduced to fit in the circulation passage, then the spacer can pass through the return path, but the spacer becomes loose and may fall down and jam the balls
Solution Approach 1:
The asymmetric oval cross-section with non-concentric inner and outer curves provides optimized clearance that allows the spacer to maintain its size for stability while still passing through the return path smoothly without contact with the inner guiding surface.
3Device complexity
If the return path is designed with conventional circular cross-section, then the structure is simple, but the spacer contacts the inner periphery causing interference
Solution Approach 1:
The patent adopts an asymmetric oval cross-section for the return passage, which increases structural complexity slightly but dramatically improves the ease of operation by eliminating spacer contact with the inner guiding surface through optimized clearance design.
Data Source
AI summary
A circulation passage structure for a ball screw, the circulation passage structure is used to connect the helical groove and the circulation hole of the nut, so as to form a circulation path for a plurality of balls and spacers. Due to the spacers move in a manner of being clamped between two balls, the spacer inside the return path will be pushed to move inward. The degree of curvature of the inner guiding surface connected to the inner curve can be moderated by shifting outward the location of the center of the inner curve and increasing its radius of curvature. By such arrangement, the spacer will not contact the inner guiding surface when it is pushed to move inward, and the spacer can pass through the return passage easily without the problem of impacting the return passage.