Tapered Plug Stem Alignment in Control Valve Couplings
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Solution Overview
Problem
The existing methods for connecting a stem to a valve member in control valves often result in misalignment due to the press-fitting of a pin, which affects the integrity of the coupling and can lead to non-perpendicular positioning of the stem relative to the valve member.
Innovation Solution
The proposed solution involves using a stem with exterior threads and a tapered plug that expands to secure the stem to the valve member, ensuring solid contact alignment through a slot in the threaded opening, and additional features like counter bores and aligned passages to prevent rotation, thereby minimizing misalignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pin is press-fitted into the stem and valve member to secure the stem, then the stem is locked in position and rotation is prevented, but misalignment between the stem and valve member occurs affecting coupling integrity
Solution Approach 1:
The slot is formed in the stem at the threaded opening before the stem is threaded into the valve member. This preliminary preparation allows the tapered plug to expand within the slot during the threading process, ensuring proper alignment is maintained throughout the assembly process rather than being compromised by post-assembly pin press-fitting
Solution Approach 2:
The tapered plug changes its dimensional parameters (expands radially) as it is driven into the stem through the slot. This expansion creates a wedging action that secures the stem to the valve member while maintaining alignment, replacing the need for separate pin press-fitting that causes misalignment
2Strength
If the stem is threaded tightly into the valve member to secure the connection, then the coupling strength is improved, but misalignment occurs due to the subsequent pin press-fitting process
Solution Approach 1:
The slot and tapered plug mechanism merges the alignment function and securing function into a single integrated system. As the tapered plug expands within the slot during threading, it simultaneously maintains alignment and secures the connection, eliminating the need for separate pin press-fitting that compromises perpendicular positioning
Solution Approach 2:
The tapered plug acts as an intermediary element between the stem and valve member. It mediates the connection by expanding within the slot to provide both alignment and securing functions, replacing the harmful direct press-fitting of a pin that causes misalignment
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
This approach ensures consistent and secure attachment of the stem to the valve member, reducing misalignment and enhancing the integrity of the coupling, ensuring precise control of fluid flow in industrial applications.
Implementation Method 1
pressing the tapered plug into the threaded opening of the stem causes the tapered plug to expand
Implementation Method 2
The exterior threads of the tapered plug are engaged by the interior threads of the threaded opening adjacent the end of the stem
Data Source
Figure 1
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AI summary
Apparatus to connect a stem to a valve member and, more particularly, apparatus to connect a threaded stem to a valve member of a control valve are disclosed. An example apparatus includes the threaded stem received in a threaded opening of the valve member and a plug received in an opening of the stem to expand diametrically the end of the stem to secure the threaded stem to the valve member.