Ball Screw Nut Sealing via Segmented Counterbores
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Solution Overview
Problem
In ball screws, the O-ring sealing performance is degraded during assembly due to shearing when nuts are pressed together while rotating, leading to reduced workability and increased assembly time, especially when cooled by coolant through-holes.
Innovation Solution
The design features counterbores on opposing end faces of nuts with a ring-shaped sealing member having two O-rings, where one counterbore accommodates the entire sealing member and the other is smaller, allowing for preload positioning and preventing O-ring shearing by pushing the sealing member into the smaller counterbore.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the O-ring is pressed while rotating the nuts during assembly, then the nuts can be coupled together, but the O-ring may be sheared and sealing performance degrades
Solution Approach 1:
The sealing function is segmented into two separate O-rings positioned in different locations: one O-ring seals the coolant flow path while the other seals the mating surface between nuts. This segmentation allows each O-ring to perform its specific sealing function independently without being subjected to shearing forces during assembly, thus maintaining sealing performance while enabling easy nut coupling.
Solution Approach 2:
A ridge structure is introduced as an intermediary element between the two nuts. The ridge fits into grooves on both nuts and serves as a mediator that guides the nuts together during assembly, preventing misalignment and reducing the force required to couple the nuts, thereby preventing O-ring shearing while maintaining ease of operation.
2Reliability
If the two nuts are brought into contact while detached from the threaded shaft, then O-ring shearing is avoided, but workability is reduced and assembling time increases
Solution Approach 1:
The ridge structure is preliminarily positioned on one of the nuts before assembly begins. This preliminary action allows the second nut to be guided into proper alignment and coupled with the first nut in a single operation while both nuts remain on the threaded shaft, avoiding the need to detach and reattach them, thus maintaining both sealing performance and assembly efficiency.
3Ease of operation
If a single deep counterbore is used to accommodate the sealing member, then assembly is simplified, but the sealing member cannot be properly positioned for preload application
Solution Approach 1:
The counterbore is segmented into two separate counterbores of different depths: a first counterbore in one nut and a second counterbore in the other nut. The ridge structure fits into both counterbores, with the shallower second counterbore providing precise positioning for preload application while the deeper first counterbore accommodates the ridge structure. This segmentation achieves both assembly simplicity and precise preload positioning.
Solution Approach 2:
Different depths of counterbores are provided at different locations to serve different functions: the first counterbore has sufficient depth to accommodate the ridge structure and allow easy assembly, while the second counterbore has a controlled shallower depth to provide precise positioning for preload application. This local differentiation of counterbore depths achieves both assembly simplicity and manufacturing precision.
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 improves workability and sealing performance by preventing O-ring shearing and ensuring coolant sealing without detaching nuts from the shaft, maintaining effective coolant sealing during assembly.
Implementation Method 1
the nuts are cooled by flowing a coolant through through-holes formed in the nuts in axial directions of the nuts
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
To improve workability and sealing performance of a coolant when a plurality of nuts in a ball screw are brought into contact with one another, the plurality of nuts being coupled to one another, assembled to one threaded shaft and cooled by flowing the coolant through through-holes formed in the plurality of nuts in axial directions of the plurality of nuts. The ball screw (1) includes counterbores (4, 5) of the through-holes (3) formed on opposing end faces of both of adjoining nuts (21, 22), and a ring-shaped sealing member (6) inserted thereto. The counterbores (4, 5) are formed such that a depth (D2) of one counterbore is larger than a length of the sealing member (6) (D2 > L), and the a depth (D1) of the other counterbore is smaller than the length of the sealing member (6) (D1 < L), and such that circumferential positions of the counterbore (4, 5) of the adjoining nuts (21, 22) face each other when a desired preload is exerted.