External Circulation Ball Screw Return Device Segmentation
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Solution Overview
Problem
Conventional external circulation type ball screws face issues with processing the pipe hole of the nut, unstable return device positioning, increased assembly time, and noise due to vibrating components, as well as difficulties in manufacturing and fixing the return device, leading to potential damage and failure.
Innovation Solution
A hollow nut with a rolling groove and helical groove design, featuring guiding members and a cover with threaded holes and fixing elements, allows for stable assembly and positioning of the return device without requiring a multi-spindle processing machine, enabling smooth circulation of rolling elements and mass production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional return device with bent pipe is used, then the rolling elements can circulate, but the bent portion weakens due to high-speed impact and causes instability
Solution Approach 1:
The return device is divided into multiple components: a return pipe with through holes, fixing members (screws), and guiding members. This segmentation allows each part to be optimized independently and assembled flexibly, eliminating the weak bent portion while maintaining circulation function
Solution Approach 2:
The return pipe is designed with through holes that extend in the axial direction, creating a new dimensional pathway for rolling elements. This allows the rolling elements to exit and re-enter the circulation path without requiring bent portions, thereby eliminating the strength weakness while maintaining reliability
2Ease of manufacture
If multi-sectional bent pipe is used for return device, then the return path is achieved, but the structure becomes unstable and processing becomes difficult
Solution Approach 1:
The return device is segmented into a return pipe, fixing members, and guiding members that can be manufactured separately using standard processing methods, then assembled together. This eliminates the need for complex multi-spindle processing while ensuring structural stability through proper assembly
Solution Approach 2:
Fixing members (screws) serve as intermediaries to connect the return pipe to the nut body, providing a stable structural connection that is easier to manufacture than integrated multi-sectional bent pipes while ensuring the return device remains firmly positioned
3Reliability
If return device is fixed by mounting on outer diameter of nut, then the return device is secured, but the outer diameter increases and stability decreases
Solution Approach 1:
The return device components (return pipe, fixing members, guiding members) are nested within the nut structure, with the return pipe positioned inside the nut body and secured through internal fixing holes. This nested arrangement secures the return device without increasing the outer diameter of the nut
4Productivity
If conventional return device is used, then the rolling elements can circulate, but the position relative to nut is hard to control and assembly time increases
Solution Approach 1:
Guiding members with guiding passages are pre-installed in the nut body through the through holes before the return pipe is assembled. This preliminary action establishes precise positioning references that control the return device's position relative to the nut, ensuring manufacturing precision while reducing final assembly time
Data Source
AI summary
An external circulation type ball screw comprises a screw, a nut, rolling elements and a return member. The nut is a hollow structure mounted on the screw. The rolling elements are received in the helical groove of the screw and the rolling groove of the nut. The return member is disposed on the nut and includes a guiding member and a cover. The guiding member is defined with two guiding portions and a first half pipe, and each guiding portion is fixed in the fixing hole of the nut. The cover includes a fixing portion for covering the guiding portion and a second half pipe for covering the first half pipe. The return member is installed in the fixing hole through the guiding portion, and then the cover is used to cover the guiding member, thus finishing the assembly of the return member. In addition, the return device can be produced by molding process, and it solves the problem that the conventional return device is difficult to assemble.