Linear Roller Bearing Strap Tensioning for Stirling Engines
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Solution Overview
Problem
Current linear bearing technologies for Stirling engines and cryocoolers face limitations in stroke capability, frequency of operation, radial load capacity, and susceptibility to wear and contamination, particularly due to the loosening of straps around rollers, leading to undesirable wear and friction, which compromises performance and efficiency.
Innovation Solution
A roller bearing sub-assembly design featuring mounting portions, rollers, and straps wrapped partially around the rollers, allowing for linear motion along a selected direction for a distance equal to the circumference of the roller, with radial spring preload to maintain contact and precision, and surface treatments to enhance load capacity and conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If straps are wrapped around rollers to provide linear bearing support, then radial load capacity is improved, but straps loosen over time causing roller lateral slide and rotational slip
Solution Approach 1:
The patent applies dynamics by making the strap tensioning system adjustable and adaptable during operation. The tensioning device allows operators to tighten straps that have loosened over time, restoring proper tension and preventing roller lateral slide and rotational slip. This dynamic adjustment capability maintains reliable linear bearing support throughout the service life of the equipment.
Solution Approach 2:
The tensioning device enables operators to perform maintenance and restore proper strap tension without replacing the entire bearing assembly. This self-service capability extends the service life of the bearing system by allowing in-field adjustment and repair of loose straps, maintaining radial load capacity and preventing performance degradation.
2Measurement precision
If straps are tightened to prevent roller lateral slide, then guidance precision is improved, but friction and wear increase
Solution Approach 1:
The patent applies parameter changes by allowing adjustment of strap tension over time. Initially, straps are tensioned sufficiently to prevent roller lateral slide and maintain guidance precision. As straps naturally loosen during operation, the tensioning device allows operators to restore proper tension levels, maintaining optimal guidance precision while minimizing excessive friction and wear that would result from permanently overtightened straps.
3Length of moving object
If stroke length is increased to improve machine performance, then power output is improved, but frequency of operation must be increased
Solution Approach 1:
The patent applies dynamics by enabling the bearing assembly to operate reliably at higher frequencies through the adjustable tensioning system. The ability to maintain proper strap tension dynamically allows the system to withstand the increased operational demands of high-frequency reciprocating motion over longer stroke lengths, supporting both improved power output and productivity.
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 provides increased guidance precision, stroke length, and frequency of operation while minimizing wear and friction, thereby enhancing the performance and efficiency of Stirling engines and cryocoolers by ensuring concentricity and preventing contact between moving parts.
Implementation Method 1
radial spring preload to maintain contact and precision
Data Source
AI summary
A roller bearing sub-assembly can include a first mounting portion, a second mounting portion spaced apart from the first mounting portion, a first roller disposed between the first and second mounting portions and straps wrapped partially around different portions of the first roller. The first mounting portion, second mounting portion, first roller and straps are configured such that the first and second mounting portions are moveable relative to each other along a selected direction for a distance that is approximately equal to a circumference of the first roller in opposite directions from a mid-stroke position. Linear roller bearing assemblies and methods of forming linear roller bearing assemblies are also disclosed, as are multi-cylinder Stirling engines and a thermal energy recovery system.