Torque Transfer Strut Clamping Fitting for Cryogenic Reliability
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Solution Overview
Problem
Torque transfer struts for superconducting rotating electrical machines face challenges in maintaining a secure connection at cryogenic temperatures due to differential thermal expansion of materials, leading to potential loosening of clamping forces.
Innovation Solution
A mechanical assembly with a clamping fitting system that includes an annular clamping member and a clamping wedge, designed to maintain constant radial clamping force across temperature changes by using materials with different coefficients of thermal expansion, ensuring a secure connection between the elongate member and the clamping fitting at both ambient and cryogenic temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a rigid clamping fitting is used to secure the elongate member at ambient temperature, then a secure connection is achieved at ambient temperature, but the connection becomes loose at cryogenic temperatures due to differential thermal contraction
Solution Approach 1:
The patent applies thermal expansion principle by selecting materials with different coefficients of thermal expansion for the clamping fitting and the elongate member. The clamping fitting is made of a material with a lower coefficient of thermal expansion than the elongate member, so that when both are cooled from ambient to cryogenic temperatures, the elongate member contracts more than the clamping fitting. This differential contraction maintains the radial clamping force on the elongate member throughout the temperature change, preventing loosening of the connection.
2Reliability
If the radial clamping force is increased to prevent loosening, then connection security is improved, but the risk of damaging the elongate member or creating excessive stress increases
Solution Approach 1:
The patent changes the physical parameter of thermal contraction by selecting materials with different coefficients of thermal expansion. This parameter change allows the system to automatically adjust the clamping force through differential contraction, maintaining adequate connection security without applying excessive initial clamping force that could damage the elongate member or create unwanted stress.
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 compensates for thermal expansion differences, maintaining a rigid and secure connection throughout temperature changes, preventing loosening and ensuring reliable torque transfer in superconducting rotating electrical machines.
Implementation Method 1
the clamping fitting is adapted to compensate for any reduction in the radial clamping force that would otherwise occur during cooling as component parts with different coefficients of thermal expansion shrink by different amounts
Data Source
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AI summary
The present invention relates to a mechanical assembly such as a torque transfer strut (1) for a rotating superconducting machine. The torque transfer strut (1) includes a composite tube (42) having a first end that is received in a clamping fitting. The clamping fitting can include an end housing or lug (2), a clamping wedge (18) that is screwed onto a screw-threaded part (8) of the end housing, and an annular clamping member (20) that applies a radial clamping force to the first end of the composite tube (42) when the torque transfer strut (1) is at ambient temperature. The clamping fitting is adapted such that when the torque transfer strut (1) is cooled in use, e.g. a cryogenic temperature, shrinkage of the end housing (2) in the axial direction due to cooling causes the annular clamping member (20) to substantially maintain or increase the radial clamping force. More particularly, the shrinkage of the end housing (2) causes the clamping wedge (18) to apply a progressively increasing radial force to a radially inner member (22) of the annular clamping member (20) to deflect radially outwardly a plurality of circumferentially-spaced axial fingers (32). The first end of the composite tube (42) therefore remains securely clamped between the radially inner member (22) and a radially outer member (24) that together define an annular channel (26) into which the first end of the composite tube is received.