Recirculating Screw Seal Assembly for Lubricant Containment
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Solution Overview
Problem
Existing screw actuators, such as ballscrews, face challenges in maintaining lubrication due to the helical nature of the screw shaft, leading to lubricant migration and the need for frequent re-lubrication, which is particularly problematic in aerospace applications where maintenance downtime is minimized.
Innovation Solution
A seal design featuring a seal body with internal chambers and external ports that allow for the re-circulation of lubricant material within the screw assembly, utilizing openings on the inner surface to facilitate the transfer of lubricant between the screw shaft and internal chamber, and external ports for fluid transfer, creating a re-circulating path to contain lubricant material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing sealing techniques are used to contain lubricant in screw assemblies, then lubricant containment is attempted, but the helical nature of the screw shaft causes lubricant migration and loss over time
Solution Approach 1:
The seal body is divided into multiple functional zones: an internal chamber for lubricant storage, openings on the inner surface for lubricant transfer, and external ports for additional lubricant introduction. This segmentation allows the seal to actively manage lubricant distribution rather than passively containing it, preventing migration loss while maintaining containment.
Solution Approach 2:
The internal chamber acts as an intermediary reservoir between the external environment and the screw shaft lubrication points. Lubricant is transferred from the internal chamber through openings on the inner surface directly to where it is needed on the screw shaft, creating a controlled delivery system that prevents uncontrolled migration.
2Duration of action of moving object
If lubricant is contained within the screw assembly using traditional seals, then some lubrication is maintained, but periodic re-lubrication is still required due to migration
Solution Approach 1:
The seal is pre-filled with lubricant in the internal chamber during manufacturing or initial installation. This preliminary action ensures that lubricant is already available in the system before operation begins, eliminating the need for frequent top-up operations and extending the time between maintenance events.
Solution Approach 2:
The seal design enables self-lubrication through its internal chamber and opening system. As the screw shaft rotates, lubricant is automatically transferred from the internal chamber through the openings on the inner surface to the contact points, creating a self-sustaining lubrication system that reduces maintenance requirements.
3Reliability
If the seal body includes internal chambers and openings for lubricant transfer, then lubricant re-circulation is improved, but the seal structure becomes more complex
Solution Approach 1:
The seal body performs multiple functions within a single integrated structure: it seals against the screw shaft, stores lubricant in the internal chamber, transfers lubricant through openings on the inner surface, and provides external ports for lubricant introduction. This multi-functionality reduces the need for separate components while achieving effective lubricant management.
Solution Approach 2:
The internal chamber is nested within the seal body structure, with openings on the inner surface creating a nested pathway system for lubricant transfer. This nested arrangement allows complex lubricant management functionality to be integrated within the compact seal geometry without significantly increasing external dimensions.
Data Source
AI summary
Disclosed herein is a screw assembly comprising an internal re-circulating path for re-circulating lubricant fluid between a threaded screw shaft and seals provided at the ends of the screw assembly via internal chambers provided within the seals and passages formed within the nut. Also disclosed are seals for use within such assemblies.