Spool Valve Groove Geometry for Packing Seal Stability
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Solution Overview
Problem
In spool-type switching valves, the inflow of compressed fluid between the groove bottom of the recessed groove and the inner periphery of the packing can lead to issues such as the packing separating from the groove bottom and increased sliding resistance.
Innovation Solution
The spool-type switching valve incorporates a recessed groove with an inclined surface and a connection surface, where the inner periphery of the packing is in pressure-contact with the groove bottom, concentrating stress at a specific pressure contact point, thereby reducing fluid inflow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the packing is mounted in a conventional recessed groove with a flat bottom, then the packing can be easily installed, but compressed fluid flows between the groove bottom and the inner periphery of the packing, causing the packing to separate and increasing sliding resistance
Solution Approach 1:
The recessed groove bottom is designed with a curved surface (specifically, a spherical or arc-shaped surface) instead of a flat bottom. This curved surface allows the inner periphery of the packing to make line contact or point contact with the groove bottom, eliminating the gap where compressed fluid could flow. The curvature ensures that the packing is firmly held in position while maintaining effective sealing, thus preventing fluid infiltration and packing separation.
2Object-affected harmful factors
If the packing is pressed firmly against the groove bottom to prevent fluid inflow, then sealing improves, but the packing becomes prone to separation and sliding resistance increases
Solution Approach 1:
The curved bottom surface of the recessed groove creates a geometric configuration where the packing's inner periphery contacts the groove bottom at a specific line or point. This curvature provides natural mechanical retention that prevents packing separation without requiring excessive pressing force. The geometry itself acts as a retaining feature, reducing sliding resistance while maintaining firm contact to prevent fluid inflow.
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 design effectively minimizes the inflow of compressed fluid, preventing the packing from separating from the groove bottom and reducing sliding resistance, thus enhancing the valve's operational reliability.
Implementation Method 1
the inner periphery of the packing is in pressure-contact with the groove bottom with stress concentration at a pressure contact point
Data Source
Figure 1
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AI summary
[Object] To reduce, in a spool-type switching valve in which a recessed groove in which a packing is mounted is provided at a land portion of a spool, the inflow of compressed fluid between the bottom of the recessed groove and the inner periphery of the packing as much as possible by removing the structure of the recessed groove. [Solution] In a spool-type switching valve 1 in which a recessed groove 50 in which a packing 13 is mounted is provided at a land portion 22 of a spool 20, a groove bottom 51 of the recessed groove is formed of an inclined surface 52 that has an axial length half or larger than the length of the groove bottom in the direction of an axis L and that continuously decreases in diameter from an upstream end 54 to a downstream end 55, the inner periphery 14 of the packing is brought into pressure-contact with the groove bottom with stress concentration at a pressure contact point S that defines an upstream end 52a of the inclined surface, and an angle θ that a connection surface 53 connecting the pressure contact point on the groove bottom and the upstream end forms with the axis is within the range of 0° ≤ θ ≤ α, where α is an angle that the inclined surface forms with the axis.