Tapered Valve Stem-Plug Joint for Vibration-Resistant Alignment
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Solution Overview
Problem
Existing valve stem and plug connections in control valves often experience misalignment and loosening due to manufacturing tolerances and environmental factors like high temperatures and vibrations, leading to poor shut-off performance and increased maintenance needs.
Innovation Solution
The implementation of a self-locking valve stem and plug connection using tapered sections with a gradual angle (about 1.5°) that creates a frictional force to resist movement and maintain alignment, along with a staking tool that deforms the stem's rim to prevent nut rotation, ensuring secure assembly without misalignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If threads are used to connect the valve stem to the valve plug, then the connection is easier to manufacture, but misalignment occurs due to manufacturing tolerances
Solution Approach 1:
The patent changes the geometric parameters of the connection interface by replacing threaded connections with tapered surfaces. The taper angle and surface geometry are optimized to provide self-aligning properties, ensuring that the valve stem automatically centers in the valve plug regardless of manufacturing tolerances, thus achieving both ease of manufacture and high alignment precision
Solution Approach 2:
The tapered connection surfaces create an asymmetric geometry where the contact area gradually increases from the small end to the large end of the taper. This asymmetric design provides natural alignment guidance, with the taper angle specifically selected to ensure self-centering while maintaining ease of assembly and manufacturing
2Device complexity
If a drive pin is used to fix the valve stem, then the connection is simpler, but misalignment and integrity issues occur
Solution Approach 1:
The patent removes the drive pin component entirely from the connection system. Instead of using a separate fastening element that requires precise positioning, the design relies on the tapered surfaces themselves to provide both the connection and alignment functions, thereby simplifying the device structure while improving reliability
Solution Approach 2:
The patent merges the alignment function and connection function into a single tapered interface. The tapered surfaces simultaneously provide mechanical attachment and automatic alignment, eliminating the need for separate alignment features or fastening elements, thus reducing complexity and improving reliability
3Manufacturing precision
If material is removed to create a neck or bevel for alignment, then alignment is improved, but the valve stem becomes weaker
Solution Approach 1:
The patent optimizes the taper angle parameter to a specific range that simultaneously provides excellent alignment characteristics and maintains full material integrity. By carefully selecting the taper angle, the design achieves self-aligning properties without requiring material removal that would create weak sections or stress concentration points
4Adaptability or versatility
If the valve stem is exposed to high temperatures and vibrations, then the valve operates in harsh environments, but the stem becomes worn and loosens
Solution Approach 1:
The tapered connection surfaces are designed with inherent friction-based self-locking properties that prevent loosening before it can occur. The geometry of the taper creates a mechanical interference that resists separation forces, providing built-in protection against the effects of vibration and thermal expansion before they can cause loosening or wear
Solution Approach 2:
The patent converts the potentially harmful effects of vibration and thermal expansion into beneficial forces. The tapered geometry is designed so that vibrational forces and thermal growth actually increase the contact pressure and friction between the tapered surfaces, thereby enhancing the self-locking effect and preventing loosening rather than causing it
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 solution achieves improved alignment and resistance to wear and loosening, meeting Class V shut-off standards, and simplifies manufacturing and assembly while enhancing the valve's ability to withstand high temperatures and vibrations.
Implementation Method 1
The tapers of the first portion of the valve plug and the third section of the valve stem create a frictional force that resists movement of the valve stem out of the bore
Data Source
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AI summary
Example valve stem and plug connections and example staking tools are described herein. An example apparatus includes a valve plug having a first side, a second side opposite the first side and a bore extending from the first side to the second side. A first portion of the bore is tapered from a first diameter to a second diameter smaller than the first diameter. A valve stem is disposed within the bore of the valve plug. The valve stem includes a first section, a second section and a third section between the first and second sections. The third section is tapered from a third diameter to a fourth diameter smaller than the third diameter. The tapers of the first portion of the valve plug and the third section of the valve stem, when engaged, create a frictional force that resists movement of the valve stem out of the bore.