Non-Uniform Drive Key for Misaligned Rotary Ball Valves
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Solution Overview
Problem
Rotary valve systems in twin bed treatment systems face challenges with hysteresis and irregular compression of seals due to center line misalignment and tolerance stack-ups, leading to delayed or non-uniform rotation of ball valves and potential leakage.
Innovation Solution
A rotary valve design incorporating a drive key with non-uniform thickness, thinner in the middle and thicker at the ends, which allows for slight angular adjustment between slotted openings to accommodate misalignment while minimizing hysteresis and ensuring proper seal registration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a uniform thickness drive key is used to connect ball valves, then the structure is simple and manufacturing is easy, but center line misalignment and tolerance stack-ups cause hysteresis and irregular seal compression
Solution Approach 1:
The drive key transitions from uniform thickness to non-uniform thickness, with the middle section being thinner than the end sections. This local variation in geometry allows the drive key to accommodate center line misalignment and tolerance stack-ups between ball valves, reducing hysteresis while maintaining reliable seal compression and synchronized rotation.
2Reliability
If tolerance stack-ups are reduced to minimize hysteresis, then rotation synchronization improves, but manufacturing precision requirements increase
Solution Approach 1:
The drive key geometry is modified by changing the thickness parameter along its length. The non-uniform thickness distribution (thinner middle, thicker ends) compensates for cumulative tolerances in the assembly, allowing standard manufacturing tolerances to achieve the desired rotation synchronization without requiring ultra-precise manufacturing.
3Adaptability or versatility
If the drive key thickness is reduced to accommodate misalignment, then angular adjustment flexibility increases, but hysteresis increases due to excessive clearance
Solution Approach 1:
The non-uniform thickness distribution optimizes the balance between adaptability and hysteresis. The thinner middle section provides angular adjustment flexibility for misalignment, while the thicker end sections maintain sufficient contact pressure and minimize clearance-induced hysteresis, ensuring reliable seal compression.
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
A rotary valve includes a first ball valve (52a) including a first stem (252a) extending from a first proximal stem end (358a) to a first distal stem end (356a) outward from the first ball valve. The first stem (252a) including a first slotted (260a) opening extending from the first distal stem end into the first stem. The rotary valve includes a second ball valve (52b) including a second stem (252b) extending from a second proximal stem end (358b) to a second distal stem end (356b) outward from the second ball valve. The second stem including a second slotted opening (260b) extending from the second distal stem end into the second stem, wherein the second stem extends towards the first stem. The rotary valve includes a drive key (400) located within the first slotted opening (260a) and the second slotted opening (260b). The drive key (400) operably connects the first ball valve (52a) to the second ball valve (52b). The drive key (400) has a non-uniform thickness.