Waterproof Ball Screw Spline Cover With Rotary Seal Separation
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Solution Overview
Problem
Existing waterproof structures for horizontally articulated robots using bellows-shaped cover members face challenges with high costs due to the need for expensive oil seals and inferior performance with labyrinth seals, particularly when dealing with rotating parts.
Innovation Solution
A waterproof structure that includes an extension shaft coaxial with a ball screw spline shaft, a cylindrical cover member, and a rotary connection unit allowing relative rotation, utilizing fixed seals and labyrinth seals to maintain waterproofing without the need for costly oil seals, and reducing torsional forces on the cover member.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If oil seals are used for sealing rotating parts, then waterproof performance is improved, but cost increases significantly
Solution Approach 1:
The sealing system is divided into two independent parts: a fixed seal for the stationary ball screw spline shaft and a labyrinth seal for the rotating extension shaft. This segmentation allows each seal to be optimized independently, eliminating the need for expensive oil seals while maintaining effective waterproofing for both rotating and stationary components.
Solution Approach 2:
A rotary connection unit is introduced as an intermediary mechanism between the fixed ball screw spline shaft and the rotating extension shaft. This rotary connection unit enables relative rotation while maintaining sealing through the combination of fixed and labyrinth seals, providing a cost-effective alternative to expensive rotation-capable oil seals.
2Ease of manufacture
If labyrinth seals are used for sealing, then cost is reduced, but waterproof performance deteriorates
Solution Approach 1:
The sealing function is segmented into two types: fixed seal for the non-rotating ball screw spline shaft and labyrinth seal for the rotating extension shaft. This segmentation allows the labyrinth seal to be used only where rotation occurs, maintaining cost-effectiveness while the fixed seal provides robust sealing where rotation is absent, thus improving overall waterproof performance.
Solution Approach 2:
Different sealing qualities are applied to different locations based on their functional requirements. The fixed seal provides high-quality sealing for the stationary shaft, while the labyrinth seal provides adequate sealing for the rotating shaft. This local differentiation optimizes both cost and performance by matching seal type to operational needs.
3Reliability
If the cover member is made long to cover both shafts, then waterproof coverage is improved, but torsional forces increase
Solution Approach 1:
The cover member is segmented into two separate components: a first cover for the ball screw spline shaft and a second cover for the extension shaft. This segmentation allows each cover to be optimized independently in length, preventing excessive torsional forces while maintaining adequate waterproof coverage for each respective shaft.
Solution Approach 2:
Instead of using one long cover member to cover both shafts, the invention inverts the approach by using two separate cover members of appropriate lengths. This inversion eliminates the torsional force problem caused by excessive cover length while maintaining comprehensive waterproof protection through the coordinated arrangement of multiple covers.
Data Source
AI summary
A waterproof structure including an extension shaft disposed at an upper side of a vertically extending ball screw spline shaft so as to be coaxial with the ball screw spline shaft, a cylindrical cover member that covers the extension shaft and the ball screw spline shaft and is configured to be extended and shortened in a direction along a longitudinal axis of the extension shaft, and a rotary connection unit that connects the ball screw spline shaft and the extension shaft to each other so that the ball screw spline shaft and the extension shaft are configured to rotate relative to each other around the longitudinal axis, where an upper end of the cover member is fixed to an upper end of the extension shaft.