Ballscrew Seal With PTFE Scraper for Low-Friction Water Exclusion
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Solution Overview
Problem
Ballscrew assemblies face challenges in effectively sealing lubricant leakage and water ingress while minimizing frictional forces, which is critical for applications like aircraft systems where moisture exposure can contaminate the lubricant and impair functionality.
Innovation Solution
A ballscrew assembly with an annular seal comprising a resilient body made of elastomeric material and a PTFE layer, combined with an annular scraper to expel fluid, and a casing for protection, which reduces friction and prevents water ingress by using a scraper to remove water before it reaches the seal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If seals made of rigid materials energized by spring members are used to prevent lubricant leakage and water ingress, then sealing effectiveness is improved, but frictional forces increase and binding occurs
Solution Approach 1:
The patent changes the material parameters of the seal from rigid to compliant/elastomeric material. This allows the seal to deform and conform to the mating surfaces, maintaining effective sealing contact while accommodating dimensional variations and thermal expansion, thereby reducing friction and preventing binding while preserving sealing effectiveness.
Solution Approach 2:
The patent employs composite material construction for the seal, combining elastomeric or compliant material with potentially reinforced layers or coatings. This composite structure provides both the compliance needed for low-friction operation and the durability required for effective sealing in demanding applications.
2Force
If large clearances are designed in seals to avoid frictional binding, then friction is reduced, but sealing effectiveness deteriorates
Solution Approach 1:
The patent utilizes the elastic properties and compliance of the seal material to maintain sealing contact despite larger clearances. The compliant material deforms to fill gaps and maintain intimate contact with mating surfaces, achieving effective sealing without requiring tight tolerances that would increase friction.
Solution Approach 2:
The patent introduces dynamic adaptability through compliant seal material that can deform and adjust its shape in response to operating conditions, clearance variations, and load changes. This dynamic behavior allows the seal to maintain effective contact across varying clearances while accommodating movement without binding.
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 solution effectively limits lubricant leakage and water ingress while maintaining low frictional forces, enhancing the reliability and longevity of ballscrew assemblies in adverse conditions.
Implementation Method 1
the seal comprising a resilient body
Implementation Method 2
a layer formed of PTFE and disposed radially between the resilient body and the screw and configured to contact the radially outer surface of the screw
Data Source
AI summary
A ballscrew assembly includes a nut having a first helical groove formed on a radially inner surface and defining an axis, a screw disposed along the axis (X) and within the nut and that includes a second helical groove formed on a radially outer surface and opposed to the first helical groove so as to form a helical raceway. The assembly also includes a plurality of balls disposed in the helical raceway and an annular seal disposed radially between the nut and the screw. The seal includes a resilient body and a layer formed of PTFE and disposed radially between the resilient body and the screw and configured to contact the radially outer surface of the screw. An optional annular scraper is disposed axially adjacent to the seal and is configured to receive fluid at one axial end and expel fluid at a second axial end.