Fluid Cassette Valve Actuation Using Hydrostatic Pressure

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Solution Overview

Problem

Existing fluid processing systems for blood and blood component processing face challenges in maintaining fluid flow without collapsing flexible sheeting in the cassette passageways, often requiring the use of vacuums to prevent obstruction.

Innovation Solution

The system employs a combination of pumps and hydrostatic pressure to maintain positive pressure upstream of the valve station, preventing the collapse of flexible sheeting by using a fluid supply container positioned above the cassette, which provides sufficient pressure to counteract pressure drops during fluid flow.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If flexible sheeting is used in the cassette passageway, then the system is more adaptable and easier to manufacture, but the flexible sheeting collapses under negative pressure causing fluid flow obstruction

Engineering Contradiction:

Improvecassette design flexibilityVSAvoidfluid flow continuity

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The system applies preliminary positive pressure to the flexible sheeting before negative pressure is applied during fluid flow. The pump is configured to maintain positive pressure upstream of the valve station, which counteracts the collapsing effect of negative pressure downstream, preventing fluid flow obstruction before it can occur

Inventive Principle:

Principle #9Preliminary anti-action

Solution Approach 2:

The system changes the pressure parameter from negative to positive by positioning the pump downstream of the valve station. This parameter change prevents the flexible sheeting from collapsing while maintaining adaptability of the cassette design

Inventive Principle:

Principle #35Parameter changes

2Reliability

If vacuum is used to prevent sheeting collapse, then fluid flow is maintained, but the system complexity increases and energy consumption increases

Engineering Contradiction:

Improvefluid flow continuityVSAvoidsystem complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

Instead of using vacuum (negative pressure) to prevent sheeting collapse as in conventional systems, this invention inverts the approach by using positive pressure from a pump positioned downstream of the valve station. This reversal eliminates the need for complex vacuum systems while maintaining fluid flow continuity

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The invention extracts the vacuum system from the configuration by positioning the pump downstream of the valve station rather than using a vacuum source upstream. This removes the need for vacuum generation equipment and simplifies the overall system design

Inventive Principle:

Principle #2Taking out (Extraction)

3Reliability

If pump is positioned downstream of valve station, then positive pressure prevents sheeting collapse, but the pressure drop during fluid flow increases

Engineering Contradiction:

Improveflexible sheeting stabilityVSAvoidpressure drop

Core Design Contradiction:

ReliabilityVSStress or pressure

Solution Approach 1:

The pump is configured to apply positive pressure preliminarily to the flexible sheeting before fluid flow begins or during flow to counteract pressure drops. This preliminary action ensures the sheeting remains stable throughout the fluid flow process despite the downstream positioning

Inventive Principle:

Principle #10Preliminary action

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 solution allows for efficient fluid flow without the need for vacuums, ensuring consistent operation and preventing sheeting collapse, thereby maintaining fluid flow integrity and system functionality.

Implementation Method 1

A fluid supply container is in communication with the defined passageway and disposed at a height above the cassette to provide positive hydrostatic pressure at the valve location when the first pump draws fluid away from the valve location

Methodology Applied

Scientific EffectHydrostatic pressure: Pressure Gradient

Implementation Method 2

A first pump is configured to draw fluid away from the valve location along the defined passageway, and the first pump is disposed downstream of the valve location

Methodology Applied

Scientific EffectSuction: Suction

Implementation Method 3

A second pump is configured to pump fluid towards the valve location along the defined passageway, and the second pump is disposed upstream of the valve location

Methodology Applied

Scientific EffectPressure increase: Pressurisation

Data Source

PatentUS10441706B2System and method for improved fluid flow control within a fluid circuit cassette

Publication Date: 2019.10.15 FENWAL INC

AI summary

A fluid processing system for controlling fluid flow comprises a cassette having a defined passageway on a first side. The first side includes flexible sheeting disposed over the passageway. The system comprises a durable processing device configured to engage the first side of the cassette, the durable processing device comprising a valve actuator configured to engage the flexible sheeting at a valve location along the passageway. The system comprises a first pump configured to draw fluid away from the valve location along the passageway. The first pump is disposed downstream of the valve location. The system comprises a second pump configured to pump fluid towards the valve location along the defined passageway. The second pump is disposed upstream of the valve location. The first and second pumps are configured to operate in concert and configured to provide pressure to prevent collapsing of the flexible sheeting against the passageway during operation.