Diaphragm Pump Volume Measurement Using Pneumatic Pressure Equalization
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Solution Overview
Problem
The complexity and size of past machines and associated disposables for various Automated Peritoneal Dialysis (APD) modalities have dampened widespread patient acceptance, necessitating improved accuracy and efficiency in measuring fluid volumes within diaphragm pumps used in these systems.
Innovation Solution
A system and method for measuring liquid volumes in a pneumatically actuated diaphragm pump using an ideal gas model, involving pressure equalization processes and polytropic/adiabatic modeling to calculate chamber volumes, with a controller managing valves and sensors to enhance accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional fluid measurement methods are used in diaphragm pumps, then the system structure remains simple, but measurement precision is insufficient for accurate fluid volume control
Solution Approach 1:
The patent replaces conventional mechanical fluid measurement methods with a pneumatic measurement system. A reference chamber of known volume is connected to the control chamber via a conduit, and pressure changes are measured using pressure sensors. The fluid volume is calculated based on pressure equalization principles and the ideal gas law, substituting direct mechanical measurement with a pneumatic-indirect measurement approach that achieves higher precision.
Solution Approach 2:
The patent introduces a reference chamber as an intermediary element between the control chamber and the measurement system. The reference chamber with known volume serves as a reference standard, allowing indirect measurement of fluid volume through pressure comparison. This intermediary enables accurate measurement without directly measuring the fluid itself, resolving the contradiction between precision and complexity.
2Measurement precision
If multiple fluid lines are used to improve measurement accuracy, then measurement precision improves, but device complexity increases
Solution Approach 1:
The patent makes the control chamber serve multiple functions: it acts as both the pumping control chamber and the measurement chamber. The same control chamber used for diaphragm actuation also serves as the reference chamber for fluid volume measurement. This multi-functionality eliminates the need for separate measurement chambers and fluid lines, achieving high measurement precision without proportionally increasing device complexity.
3Productivity
If manual drain and fill procedures are used, then device complexity is low, but productivity is reduced due to time-consuming procedures
Solution Approach 1:
The patent enables the diaphragm pump to automatically measure and control fluid volumes without external intervention. The pneumatic measurement system continuously monitors pressure changes and calculates fluid volume in real-time, allowing the system to self-regulate fill and drain volumes. This automation eliminates manual measurement and adjustment procedures, significantly improving productivity while the modular design keeps complexity manageable.
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
Enhances the precision and efficiency of fluid measurement in diaphragm pumps, improving the functionality and user experience of APD systems, thereby increasing patient acceptance and flexibility.
Implementation Method 1
connect the control chamber to the reference chamber, measure a third equalized pneumatic pressure in the control and reference chambers
Implementation Method 2
compute a control chamber volume based on an ideal gas model that assumes an adiabatic pressure equalization process in the reference chamber and a polytropic pressure equalization process in the control chamber
Implementation Method 3
a pneumatically actuated diaphragm pump
Implementation Method 4
a diaphragm separating a pneumatically actuated control chamber from the pumping chamber
Data Source
AI summary
Improvements in fluid volume measurement systems are disclosed for a pneumatically actuated diaphragm pump in general, and a peritoneal dialysis cycler using a pump cassette in particular. Pump fluid volume measurements are based on pressure measurements in a pump control chamber and a reference chamber in a two-chamber model, with different sections being modeled using a combination of adiabatic, isothermal and polytropic processes. Real time or instantaneous fluid flow measurements in a pump chamber of the diaphragm pump are also disclosed, in this case using a one-chamber ideal gas model and using a high speed processor to obtain and process pump control chamber pressures during fluid flow into or out of the pump chamber. Improved heater control circuitry is also disclosed, to provide added or redundant safety measures, or to reduce current leakage from a heater element during pulse width modulation control of the heater element. Improvements are also disclosed in an application of negative pressure during a drain phase in peritoneal dialysis therapy, and to control an amount of intraperitoneal fluid accumulation during the therapy. Improvements in efficiency are also disclosed in movement of fluid into and out of a two-pump cassette and a heater bag of the peritoneal dialysis cycler, and in synchronization of operation of two or more pumps in the peritoneal dialysis cycler or other fluid handling devices using a multi-pump arrangement.