Reverse Flow Check Valve in Hydraulic Series Circuit

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Solution Overview

Problem

In hydraulic valve assemblies, the series circuit connection allows a downstream movable member to cause unintended motion in upstream members due to shared fluid pressure, leading to incorrect operation of cylinders, where the intended retraction results in extension due to pressure imbalances across the piston and rod chambers.

Innovation Solution

Incorporating a reverse motion check valve in the downstream feed passage, which uses a spring-biased spool to prevent fluid flow from downstream to upstream when downstream pressure exceeds upstream pressure, ensuring dedicated fluid flow to each function and preventing reverse motion influence on upstream functions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If a series circuit connection is used to connect multiple movable members, then return flow from activated movable members is recycled to downstream movable members, but a downstream movable member can cause unintended motion in upstream members due to shared fluid pressure

Engineering Contradiction:

Improverecycling return flowVSAvoidunintended motion control

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent divides the series circuit into segmented flow paths by introducing check valves at specific locations. Each check valve creates a unidirectional flow path that segments the otherwise continuous series circuit, allowing return flow recycling while preventing reverse pressure transmission that causes unintended motion.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The check valve acts as an intermediary element between upstream and downstream movable members in the series circuit. It mediates the fluid flow by allowing return flow to pass through to downstream members while blocking the reverse pressure transmission that would cause unintended motion in upstream members.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If downstream pressure exceeds upstream pressure in a series circuit, then fluid flows from downstream to upstream through the shared passage, but this causes incorrect operation of cylinders where intended retraction results in extension

Engineering Contradiction:

Improveseries circuit operationVSAvoidcylinder position control

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The patent inverts the normal bidirectional flow capability by introducing check valves that enforce unidirectional flow. Instead of allowing fluid to flow freely in both directions between upstream and downstream members, the check valve reverses the flow permission, allowing only upstream-to-downstream flow while blocking downstream-to-upstream flow, thereby preventing pressure-induced incorrect operation.

Inventive Principle:

Principle #13The other way round (Inversion)

3Reliability

If a check valve is added to prevent reverse fluid flow, then unintended motion in upstream functions is prevented, but device complexity increases

Engineering Contradiction:

Improvemotion control accuracyVSAvoidvalve assembly structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The check valve is integrated into the existing series circuit valve assembly, serving multiple functions: it enables return flow recycling, prevents reverse pressure transmission, and maintains unidirectional flow control. By making the check valve a multi-functional component within the existing assembly rather than a separate add-on, the patent minimizes the increase in device complexity while achieving reliable motion control.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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

Prevents unintended motion in upstream functions by maintaining separate pressure control across the piston and rod chambers, ensuring accurate operation of hydraulic cylinders by isolating downstream and upstream pressures, thus allowing for more precise control and intended movement.

Implementation Method 1

a spring-biased spool to prevent fluid flow from downstream to upstream

Methodology Applied

Scientific EffectSpring biasing: Spring

Implementation Method 2

when downstream pressure exceeds upstream pressure

Methodology Applied

Scientific EffectPressure differential: Pressure Gradient

Implementation Method 3

allowing fluid flow from upstream to downstream

Methodology Applied

Scientific EffectPressure differential: Pressure Gradient

Data Source

PatentUS10024445B2Reverse flow check valve in hydraulic valve with series circuit

Publication Date: 2018.07.17 PARKER HANNIFIN CORP

AI summary

A valve assembly includes a valve body having at least a first bore and a second bore, a flow passage connecting the first bore to the second bore, a plurality of ports opening to each bore respectively, the first bore being upstream of the second bore. First and second spools are disposed in the first and second bores, respectively, for controlling the flow of fluid to and from the respective ports. A check valve is disposed in the flow passage and configured to prevent fluid flow from the second spool towards the first spool through the flow passage while allowing fluid flow from one of the ports in the first bore towards the second spool through the flow passage.