Undulated Plastic Radial Bearings for Thermal Expansion Mismatch
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Solution Overview
Problem
Plastic radial bearings face limitations due to higher thermal expansion coefficients compared to metals, leading to challenges in accommodating thermal changes and material constraints in supporting radial loads for rotating and reciprocating applications.
Innovation Solution
The use of a cylindrical plastic bearing body with undulations that form gradual radially inward and outward waves, along with circumferentially spaced grooves, to accommodate thermal expansion differences between plastic and metal components, while minimizing friction through lubricant flow and high-performance plastic materials like PEEK.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If plastic material is used for radial bearings, then weight is reduced and dry friction is reduced, but thermal expansion difference with metal housing and shaft causes reliability issues
Solution Approach 1:
The patent modifies the physical parameters of the plastic bearing by introducing undulations that change the effective thermal expansion characteristics. The undulated geometry allows the bearing to expand and contract in a controlled manner, changing how the material responds to thermal changes while maintaining the lightweight plastic construction.
Solution Approach 2:
The undulations create a dynamic structure that can adapt to thermal expansion differences. As temperature changes, the undulated surface allows the bearing to flex and adjust its geometry, dynamically accommodating the differential expansion between plastic and metal components rather than maintaining a rigid fixed geometry.
2Ease of manufacture
If plastic material is used for radial bearings, then ease of manufacturing is improved, but material limits reduce adaptability to high performance applications
Solution Approach 1:
The undulated geometry changes the functional parameters of the plastic bearing, enabling it to operate in higher performance applications. The wave-like structure modifies load distribution and thermal response characteristics, allowing plastic material to adapt to demanding rotating and reciprocating applications that would normally require metal bearings.
3Reliability
If undulations are added to plastic bearing body, then thermal expansion accommodation is improved, but device complexity increases
Solution Approach 1:
The undulated surface segments the bearing geometry into multiple wave-like sections. This segmentation allows each portion of the bearing to independently respond to thermal expansion, distributing the accommodation function across multiple segments rather than requiring a complex overall structure. The repeated undulation pattern creates modular thermal response zones.
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 undulations effectively manage thermal expansion, reducing plastic deformation and minimizing both lubricated and dry friction, thereby enhancing the performance and reliability of plastic radial bearings in mixed-material systems.
Implementation Method 1
Thermal expansion for plastics is much higher than metals and this thermal expansion difference along with their material limits pose challenges to use of plastic as radial bearing elements. The undulations accommodate for thermal expansion of the plastic bearing relative to a metal housing and shaft.
Implementation Method 2
minimizing friction through lubricant flow
Data Source
AI summary
A bearing for use between an outer member and an inner member that is movable relative to the outer member. The bearing includes a generally cylindrical plastic body having a plurality of undulations that form gradual radially inward and radially outward waves relative to a circular path.