Spherical Thrust Seat for Butterfly Valve Shaft Deflection
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Solution Overview
Problem
Butterfly valves with shouldered shafts face increased torque loads and binding issues due to high shaft deflections, especially under differential pressures, as the low clearance between the shoulder and thrust plate leads to friction loading and binding problems.
Innovation Solution
The butterfly valve incorporates a thrust assembly with a cavity larger than the shoulder diameter, featuring upper and lower thrust plates with apertures exceeding the shaft diameter, a piston seal, shim, and ball bearings between the thrust plates, allowing for low-friction coatings and plating to facilitate rotation and deflection of the shaft.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a shouldered shaft is used to extend outside the housing, then the shaft can provide external access and positioning, but the torque loads increase and binding potential increases due to shaft deflection under high differential pressure
Solution Approach 1:
The patent replaces the traditional flat shoulder with a spherical shoulder that fits into a spherical recess in the thrust plate. This curved geometry allows the shaft to deflect under pressure while maintaining continuous contact through the spherical interface, preventing binding while still allowing external shaft extension for operation
Solution Approach 2:
The invention changes the geometric parameters of the shaft-thrust plate interface from a rigid flat shoulder to a spherical configuration with specific radius ratios. The spherical radius is designed to be proportional to the shaft radius, creating a self-aligning mechanism that accommodates deflection while maintaining reliable contact under varying pressure conditions
2Ease of manufacture
If a shouldered shaft with flat surfaces is used, then manufacturing is simplified, but friction loading increases and binding occurs due to low clearance and shaft deflection
Solution Approach 1:
The flat shoulder surfaces are replaced with spherical surfaces that have specific radius relationships. This curvature reduces friction loading by distributing contact forces more evenly and allowing the shaft to rotate smoothly within the spherical recess, while still being manufacturable through standard machining processes
Solution Approach 2:
The spherical interface creates a dynamic contact system where the contact point moves along the spherical surface as the shaft deflects and rotates. This dynamic adaptation maintains low friction throughout the operating range, unlike static flat surfaces that bind when deflection occurs
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 configuration enables the shaft to rotate and deflect while maintaining low friction, accommodating high loads and preventing binding, thus reducing torque loads and enhancing operational reliability.
Implementation Method 1
ball bearings are interposed between the upper surface of the lower thrust plate and the lower surface of the intermediate thrust plate
Data Source
Figure 1~2
Figure 3
Figure 4~6
AI summary
An intermediate thrust plate (23) is provided to absorb thrust loads while permitting rotation and deflection of a butterfly valve shaft. The intermediate thrust plate includes a body having upper (231) and lower (230) surfaces and defining an aperture extending through the body between the upper and lower surfaces, the upper surface extending annularly about the aperture and being substantially flat, the lower surface extending annularly about the aperture and having a spherical shape and at least the lower surface including a low-friction material.