Sliding Spool Valve In-Bore Seals for Low-Stiction Assembly

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Solution Overview

Problem

Piston mounted seals in sliding spool valves face challenges such as difficult assembly and maintenance, potential damage during these processes, high stiction due to compression requirements, and the need for precise manufacturing tolerances, which limits design flexibility and increases costs.

Innovation Solution

The spool valve design incorporates in-bore seals and spacers within the bore, with a removable retention component to facilitate easy assembly and disassembly, reducing stiction through optimized seal compression, and allowing for more compact and flexible valve designs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If piston mounted seals are used in sliding spool valves, then fluid sealing is achieved, but assembly and maintenance become difficult

Engineering Contradiction:

Improvefluid sealingVSAvoidassembly difficulty

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent inverts the conventional arrangement by mounting seals on the stationary bore instead of on the moving piston. The bore now carries the seals in locating grooves, while the piston slides over these stationary seals. This inversion eliminates the need to install seals onto the piston during assembly, as the seals are already positioned on the bore before piston installation.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent extracts the seals from the piston structure and places them independently on the bore. This separation allows the seals to be installed and positioned on the bore without requiring the piston to be present, simplifying the assembly process. The piston then simply slides over the pre-installed seals during normal operation.

Inventive Principle:

Principle #2Taking out (Extraction)

2Reliability

If piston mounted seals are compressed into the bore, then fluid sealing is achieved, but stiction and operational forces increase

Engineering Contradiction:

Improvefluid sealingVSAvoidstiction

Core Design Contradiction:

ReliabilityVSForce

Solution Approach 1:

By inverting the seal mounting location from piston to bore, the seal compression geometry changes. The seals mounted on the bore experience more favorable compression angles and distribution when the piston slides over them, reducing the peak contact pressures and resulting stiction forces compared to seals mounted on the piston.

Inventive Principle:

Principle #13The other way round (Inversion)

3Ease of manufacture

If seals are stretched over large sections of the piston, then assembly is attempted, but seal damage occurs

Engineering Contradiction:

Improveassembly attemptVSAvoidseal integrity

Core Design Contradiction:

Ease of manufactureVSStrength

Solution Approach 1:

The patent eliminates the need to stretch seals over large sections by inverting the mounting arrangement. Seals mounted on the stationary bore do not require stretching during piston installation, as the piston simply slides over the pre-positioned seals. This preserves seal integrity and eliminates the risk of stretching damage.

Inventive Principle:

Principle #13The other way round (Inversion)

4Ease of operation

If locating grooves have sharp edges, then seal location is achieved, but seal damage occurs during assembly and maintenance

Engineering Contradiction:

Improveseal locationVSAvoidseal integrity

Core Design Contradiction:

Ease of operationVSStrength

Solution Approach 1:

The patent applies preliminary action by providing rounded leading edges on the locating grooves before seal installation. This pre-modification of the groove geometry prevents seal damage during the assembly process, eliminating the need for careful manual handling or special installation tools that would otherwise be required to protect sharp-edged grooves.

Inventive Principle:

Principle #10Preliminary action

5Device complexity

If single seals are used for simplicity, then device complexity is reduced, but maintenance becomes difficult

Engineering Contradiction:

Improveseal quantityVSAvoidmaintenance difficulty

Core Design Contradiction:

Device complexityVSEase of repair

Solution Approach 1:

The patent segments the sealing system by using multiple seals positioned at different locations along the bore. This segmentation allows individual seals to be accessed and replaced independently during maintenance. The modular arrangement with multiple seals actually simplifies maintenance compared to a single seal, as damaged seals can be replaced without affecting the entire sealing system.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS12222040B2Sliding spool valves, and methods therefor

Publication Date: 2025.02.11 GLOBALFORCE IP LTD

AI summary

Disclosed is a spool valve to valve a fluid between at least one inlet port and at least one outlet port, having a bore with a spool operably associated therein. The bore has one or more inlet ports and at least one outlet port. Located in the bore is at least one in-bore seal, the seal fluidly sealing on a seal outer diameter to an inside diameter of the bore, and selectively fluidly sealing on a seal inside diameter to a spool outside diameter. Present also is at least one spacer located in the bore, adjacent the at least one in-bore seal having a fluid communication from a spacer internal diameter to a spacer external diameter with at least one inlet port, or the at least one outlet port. The spool moves to allow or prevent flow from an inlet port to outlet port.