Combination Shaft Assembly for Radial Centering and Heat Isolation
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Solution Overview
Problem
Threaded connections in air valve systems face issues with eccentricity and heat transfer, particularly in hot environments, and existing solutions are not economically viable.
Innovation Solution
A combination shaft design featuring a first shaft with a titanium material and a second shaft made of Inconel, utilizing a threaded connection with precise radial clearances and a locking insert, along with a through-hole for cooling, to minimize eccentricity and enhance heat transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If threaded connections are used to mitigate excessive heat transfer, then heat transfer is reduced, but eccentricity issues occur
Solution Approach 1:
The shaft is divided into two separate shafts (first shaft and second shaft) connected by a threaded connection, allowing each shaft to be optimized for its specific function while managing heat transfer and eccentricity separately
Solution Approach 2:
A keyed connection acts as an intermediary between the threaded connection and the radial centering mechanism, providing a stable reference that eliminates eccentricity while allowing the threaded portion to manage heat transfer
2Ease of manufacture
If threaded shafts are assembled through guides/bushing, then assembly is achieved, but seizing issues occur
Solution Approach 1:
The threading is extracted from the portion of the shaft that passes through the bushing, so only a smooth, non-threaded section traverses the bushing, eliminating seizing while maintaining assembly capability
Solution Approach 2:
The shaft is segmented into threaded and non-threaded portions, with the threaded portion located away from the bushing area, allowing threading to provide structural function without interfering with smooth passage through guides
3Manufacturing precision
If radial centering is provided with tight clearances, then centering precision is improved, but manufacturing complexity increases
Solution Approach 1:
Radial centering is established preliminarily through the keyed connection and precise fitting surfaces before the threaded connection is engaged, simplifying the overall assembly process while maintaining tight clearances
Data Source
Figure 1
Figure 2~3
AI summary
A combination shaft includes a first shaft (110) including an axial protrusion (116) including a first circumferential surface defining a first outer diameter and a second circumferential surface defining a second outer diameter, having external threads (128), and a second shaft (122) having a cavity (124) therein configured to receive at least a portion of the first shaft and being configured to drive an air valve (100), having internal threads (128), and defining at least a first inner radial surface having a first inner diameter and a second inner radial surface having second inner diameter, the internal threads being engagable with the external threads to prevent axial movement between the first shaft and the second shaft and the first inner radial surface being engagable with the first circumferential surface and the second inner radial surface being engagable with the second circumferential surface to provide radial centering of the first shaft to the second shaft.