Data processing: measuring – calibrating – or testing – Measurement system in a specific environment – Mechanical measurement system
Reexamination Certificate
1998-11-16
2001-04-24
Wachsman, Hal (Department: 2857)
Data processing: measuring, calibrating, or testing
Measurement system in a specific environment
Mechanical measurement system
C702S050000, C702S047000, C700S282000, C073S040000, C073S04050R
Reexamination Certificate
active
06223130
ABSTRACT:
TECHNICAL FIELD
The present invention relates to fluid flow control systems and more specifically to the detection of fluid leakage in a fluid control system.
BACKGROUND
Numerous devices exist in the prior art for controlling the flow of fluid. A subclass of such devices includes fluid flow control systems. Fluid flow control systems regulate the rate of distribution of transport fluid through a line. Some examples of fluid control systems are kidney dialysis machines and intravenous blood transfusion devices. Fluid flow control system may include a cassette holder in which a disposable cassette is placed and wherein transport fluid is pumped by a membrane which is part of the cassette.
FIG. 1
shows a portion of a prior art flow control system
14
which includes a cassette
10
mounted on a cassette holder
12
. A flexible membrane
11
covers the face of the flow control system cassette
10
and is permanently attached to the cassette
10
.
The flow control system
14
has a valving chamber
17
located in the cassette and a valve control volume
19
located in the cassette holder
12
which defines a valve
50
. A portion of the flexible membrane
11
separates the valving chamber
17
and the valve control volume
19
and acts as a barrier to keep control fluid in the valve control volume
19
from mixing and contaminating transport fluid in the valving chamber
17
. The control fluid is delivered to the valve control chamber
19
through a valve control fluid line
15
.
The flow control system
14
has a pump chamber
18
located in the flow control system cassette
10
and a pump control volume
100
located in the cassette housing
12
which defines a pump
52
. A portion of the flexible membrane
11
separates the pump chamber
18
and the pump control volume
100
and acts as a barrier to keep the control fluid in the pump control chamber
100
from mixing and contaminating the transport fluid in the pump chamber
18
while transport fluid is being pumped into or out of the pump chamber
18
. The control fluid is delivered to the pump control chamber
100
through a pump control fluid line
16
.
One problem with such a system is the cassette membrane may become punctured during transportation and handling of the cassette. If pinholes develop in the cassette membrane, the transport fluid may leak into the cassette holder requiring the cassette holder to be cleaned and replaced. Additionally, the control fluid may contaminate the transport fluid. The prior art system described above did not determine if there is a leak in the cassette after it is mounted in the cassette holder and prior to any transport fluid being pumped through the cassette.
SUMMARY OF THE INVENTION
In accordance with one embodiment of the invention, a method for detecting a leakage rate of fluid through a membrane in a fluid flow control system is provided. The fluid flow control system has a first chamber and a second chamber, the membrane is disposed between the first chamber and the second chamber, the second chamber has a connection to a pressure tank, the pressure tank has a fluid with a pressure, and the connection defines a fluid path. The method includes in a first step, blocking the fluid path. The pressure of the fluid in the pressure tank is then adjusted. The pressure is measured in the pressure tank which creates a pressure measurement at each of a first set of multiple timed intervals while the fluid path is blocked and after the pressure is adjusted. A blocked pressure rate is calculated based on the pressure measurements in the pressure tank at the first set of multiple timed intervals.
Next, the fluid path is unblocked. The pressure is measured within the pressure tank creating a pressure measurement at each of a second set of multiple timed intervals after the fluid path is unblocked. Then, an unblocked pressure rate is calculated based on the pressure measurements in the pressure tank at the second set of multiple timed intervals. Finally a leakage rate is calculated based on the blocked pressure rate and the unblocked pressure rate.
In another embodiment of the method a further step is added. An alarm is caused when the leakage rate becomes greater than a predetermined threshold value. The alarm may originate in the processor. The alarm may also be either a visual alarm or an auditory alarm.
In a further related embodiment, in the step of measuring a pressure at a first set of multiple timed intervals and in the step of measuring a pressure at a second set of multiple timed intervals the pressure is measured with a transducer. In yet another related embodiment, in the step of calculating a blocked pressure rate and in the step of calculating an unblocked pressure rate, the rates are calculated in a processor.
In yet another related embodiment, additional steps are added. After the step of measuring the pressure at a first set of multiple timed intervals, each of the pressure measurements is stored in a memory unit and the pressure measurements are then provided to the processor. Additionally, after the step of measuring the pressure at a second set of multiple timed intervals, each of the pressure measurements may be stored in the memory unit and then provided to the processor.
In another embodiment of the invention, the embodiment is directed toward a flow control system. The system may include a first chamber and a second chamber with a membrane disposed between the first and second chambers. The system further includes a pressure tank containing a fluid having a pressure connected to the second chamber. A transducer is disposed within the pressure tank which creates a pressure signal. A valve is disposed between the chamber and the pressure tank. The system also includes a valve controller connected to the valve, a pump connected to the pressure tank and a processor connected to the transducer, to the pump and to the valve controller.
The processor performs the following. The processor signals the valve controller to shut the valve. The processor adjusts the pressure of the fluid in the pressure tank with the pump. The pressure signal is read from the transducer at a first set of predetermined timed intervals and a baseline leak rate is calculated based on the first set of pressure signals while the valve is shut by the processor. The processor then sends a signal to the valve controller to open the valve. The processor reads the pressure signal from the transducer at a second set of predetermined timed intervals while the valve is open and calculates a membrane leak rate based on the second set of pressure signals. A leakage rate is calculated based on the baseline leak rate and the membrane leak rate and an alarm signal is created if the leakage rate exceeds a predefined value. The alarm signal may be an auditory or a visual alarm. In a preferred embodiment the fluid may be air.
The system may further include a memory unit for storing the pressure signals at the first set of predetermined timed intervals and storing the pressure signals at the second set of predetermined timed intervals.
A computer program product is provided, in yet another embodiment of the invention. The computer program product is a computer usable medium having computer readable program code thereon. The computer readable program code includes:
program code for activating a valve controller for blocking the fluid path.
program code for adjusting the pressure of the fluid in the pressure tank;
program code for reading the pressure in the pressure tank;
program code for creating a pressure measurement at each of a first set of multiple timed intervals while the fluid path is blocked and after the pressure is adjusted;
program code for calculating a blocked pressure rate based on the pressure measurements in the pressure tank at the first set of multiple timed intervals;
program code for activating the valve controller unblocking the fluid path;
program code for reading the pressure within the pressure tank;
program code for creating a pressure measurement at each of a second set of multiple timed interva
Bryant Robert
Gray Larry
Spencer Geoffrey
Bromberg & Sunstein LLP
DEKA Products Limited Partnership
Wachsman Hal
LandOfFree
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