Ball Spline Detour Tracks for Nut Rotation Without Collision
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Solution Overview
Problem
Conventional ball splines do not allow the nut to rotate with respect to the spline shaft, leading to collisions and potential damage during rack and pinion engagement, which restricts their application in scenarios requiring rotational movement.
Innovation Solution
The introduction of detour tracks on the spline shaft and nut, with balls circulating between these tracks and load track grooves, enables the nut to rotate by creating gaps for smooth engagement and reducing contact points, thereby preventing damage and enhancing bending resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the conventional ball spline structure is used with fixed nut position, then the structure is simple and reliable, but the nut cannot rotate with respect to the spline shaft causing collisions during rack and pinion engagement
Solution Approach 1:
The track groove is divided into multiple sections: a first track groove section with a first radius of curvature, a second track groove section with a second radius of curvature, and a third track groove section. This segmentation allows different portions of the track to serve different functions - the first section guides ball entry, the second section (with larger radius) creates clearance for rotation, and the third section maintains linear motion, thereby enabling nut rotation capability while maintaining structural integrity
Solution Approach 2:
The track groove has non-uniform curvature radii at different locations. Specifically, the second track groove section has a larger radius of curvature than the first and third sections. This local variation in geometric properties creates the necessary clearance space that allows the nut to rotate relative to the spline shaft during rack and pinion engagement, solving the adaptability issue without requiring complete structural redesign
2Ease of operation
If the track groove has uniform curvature, then the manufacturing is simple, but the balls cannot fall down into the load track grooves and circulation is hindered
Solution Approach 1:
The track groove is designed with varying curvature radii at different sections. The first section has a smaller radius that guides balls into position, while the second section has a larger radius that prevents balls from falling down and facilitates smooth circulation. This localized variation in geometric properties optimizes ball circulation while remaining manufacturable through standard machining processes
3Adaptability or versatility
If the balls have 4-point contacts in the track groove, then the load distribution is improved, but the nut cannot rotate with respect to the spline shaft
Solution Approach 1:
The track groove is segmented into different curvature sections that control ball positioning. The second track groove section with its larger radius of curvature creates a clearance zone that allows the nut to rotate relative to the spline shaft during rack and pinion engagement, while the first and third sections maintain proper ball contact for load transmission
Solution Approach 2:
The ball-spline system transitions from a static configuration to a dynamic one where the nut can rotate within a given angle range. The variable curvature track groove design enables this dynamic behavior by providing clearance space in the second section while maintaining stable contact in other sections, allowing the system to adapt between linear motion and rotational movement modes
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 ball spline with detour tracks allows the nut to rotate within a given range, preventing damage to the inclined track grooves and retainers, and improves bending resistance, enabling smooth rack and pinion engagement without collisions.
Implementation Method 1
The balls, which move along the load track grooves 2, enter non-load circulating holes 5 along circulating grooves 4 of retainers 3, and are thus circulated endlessly
Data Source
AI summary
A ball spline with detour tracks includes spline shaft, nut part movable along a longitudinal direction of the spline shaft, and balls between the nut part and the spline shaft, wherein the nut part includes nut adapted to insert the spline shaft thereinto and retainers on longitudinal sides of the nut, the spline shaft includes tracks extended along the longitudinal direction, the nut includes load track grooves formed in longitudinal direction on inner peripheral surface into which the spline shaft is inserted and non-load circulating portions formed in the longitudinal direction, each retainer includes circulating grooves on the inner peripheral surface to face the load track groove and non-load circulating portion, the balls run between the tracks and the load track grooves, and each track includes track groove formed in longitudinal direction of the spline shaft and detour tracks whose longitudinal sides are connected to the track groove.