Spool Valve Seal Structure With Pressure-Activated Packing
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Solution Overview
Problem
The existing seal structure in spool-type switching valves faces issues with packing deformation and wear due to prolonged contact with the spool hole, leading to reduced spool performance and packing damage from frictional resistance and repeated loading.
Innovation Solution
A seal structure featuring an annular groove in the spool's land portions with a packing that has smaller sealing portions than the spool hole diameter, where pressurized fluid elongates the packing to narrow the gap between the spool and hole, reducing contact and friction, and an adhesive fixes the packing's inner end to the groove.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the packing is pressed against the slide surface of the spool hole to ensure sealing, then sealing performance is improved, but the packing undergoes permanent deformation and sticking due to prolonged contact
Solution Approach 1:
The packing is designed to dynamically adjust its sealing mechanism based on spool position. During idle periods, the packing is separated from the slide surface to prevent permanent deformation. During active operation, fluid pressure causes the packing to elastically deform and seal the gap between the spool and spool hole, achieving sealing performance without prolonged static contact.
Solution Approach 2:
The packing engages in periodic contact with the slide surface only when the spool is actively switching positions, rather than continuous contact. This periodic sealing action during operational phases while remaining separated during idle phases prevents accumulation of frictional damage and extends packing service life.
2Reliability
If the packing is continuously pressed against the slide surface to prevent leakage, then sealing is improved, but frictional resistance causes wear and twisting of the packing
Solution Approach 1:
The packing transitions from a static continuously-contacting seal to a dynamic seal that engages only when needed. During spool movement, fluid pressure causes the packing to elastically deform and seal the gap. During idle periods, the packing is separated from the slide surface, eliminating frictional resistance and preventing wear and twisting.
Solution Approach 2:
The harmful continuous contact between the packing and slide surface is extracted/removed during idle periods. The packing is designed to be separable from the slide surface when the spool is not actively switching, thereby removing the source of frictional resistance while maintaining sealing capability during operational phases.
3Reliability
If the packing is made larger than the spool hole diameter to ensure sealing, then sealing performance is improved, but repeated hitting against the channel recess opening edge causes damage
Solution Approach 1:
The packing size and engagement are made dynamic rather than static. The packing is sized to engage the slide surface during active operation when fluid pressure is present, but is designed to be separated from the channel recess opening edge during idle periods, preventing repeated impact damage while maintaining adequate sealing capability during use.
Solution Approach 2:
The packing design anticipates potential impact damage by controlling when and how the packing engages with the channel recess opening edge. By ensuring the packing is separated during idle periods and only engages during active operation under fluid pressure, the design prevents beforehand the accumulation of impact damage that would lead to packing failure.
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 prevents packing deformation and damage, enhances spool operation, and extends the packing's service life by minimizing contact with the spool hole and reducing frictional resistance.
Implementation Method 1
an edge portion of the packing positioned near the space to which the pressurized fluid is supplied is elastically elongated in the radial direction due to pressure of the pressurized fluid
Implementation Method 2
an adhesive fixes the packing's inner end to the groove
Data Source
AI summary
A sealing structure is configured in the following manner. When a packing having a pair of sealing portions formed at opposite edge portions of the outer peripheral surface thereof is installed in a land portion of a spool, the outside diameter of the packing is made smaller than the diameter of a slide surface of a spool hole. In a state in which the outer periphery of the land portion opposes the slide surface and a pressurized fluid is supplied from a gas supply channel to the first space of first and second spaces that are partitioned by the land portion, the edge portion of the packing positioned near the first space is elastically elongated in a radial direction due to pressure of the pressurized fluid and thereby narrows a gap formed between the first sealing portion and the slide surface of the spool hole or abuts the slide surface.