JPS6138539A - Flow controller - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field] TECHNICAL FIELD The present invention relates primarily to a flow control device for performing gas analysis.

The invention particularly relates to a flow control apparatus comprising: a source of gas to be analyzed; a source of vacuum; a conduit; means for connecting one end of the conduit to the source of gas; and a means for connecting the other end of the conduit to the source of vacuum. means for connecting a gas analyzer; means for connecting a one-person analyzer in a duct between one end of the conduit and a vacuum source; and a conduit having a Peclet number of at least 4 between one end thereof and the predetermined point.
SUMMARY OF THE INVENTION During hospital visits or during examinations, it is often necessary to monitor gases, such as oxygen, utilized by patients receiving respiratory support.

Gas monitoring is preferably carried out during the breathing period in order to determine the composition of the relevant gases, hereinafter simply referred to as gases. It is useful to maintain precise testing procedures with suitable and accurate analyzers so that changes in breathing gases do not interfere with the monitoring process and also ensure uniform or near-uniform testing conditions. .

〔Example〕

To provide such a test or controlled environment, a breathing tube 6 is disclosed. One end of the tube is connected to the patient in a well known manner, eg, with a face mask, and the other end is connected in a standard manner. Gas flows through the breathing tube at different times and in different directions during the patient's breathing cycle.

This is indicated by arrow 7.

A tube 8 is provided for sampling such gas. This pipe intersects the pipe 6 at a suitable point and furthermore preferably has a control valve 9 therein which allows control of the gas flow area.
have. The pipe 8 is connected to the conductor W12 via the connector 11.
guided by. Conduit 12 forms part of a circuit branch.

Connector 13 opens into conduit 12 at a first predetermined point. The connector 13 can also be connected to a suitable type of gas analyzer 14.
is combined with The analyzer extends into tube 17 via connector 16. Tube 17 forms part of another circuit branch parallel to conduit 12. One circuit branch is conduit 12 and conduit 1.
7 and forming a dual passageway for gas flow coupling. Tube 17 is connected to block 19 by tube 18. Block 19 opens to a source 21 of vacuum or sub-ambient pressure. This pressure source can be a well-known vacuum pump, in particular a two-stage pump.
At a second predetermined point, preferably amp), the conduit 12 is connected to a coupling 24 via a T return pipe 22 and a 5!4 valve 23. Coupling 24 is connected to block 19. It also communicates with a vacuum source 21. conduit 1
2, coupling 24, and block 19 provide a first circuit, branch, flow path, or conduit for vacuum source 21.

Conduit 12, connector 13, gas analyzer 13, connector 16, and tubes 17 and 18 provide a second separate circuit, branch, flow path, or conduit for vacuum source 21. The pressure transducer 26 is connected to the block 19 via a pipe 27, thereby communicating with the block 19 and being affected by the associated circuit branch. Transducer 26 provides an electrical signal to conductor 28. This signal corresponds to the pressure applied to the transducer. The signal on conductor 28 enters servo machine groove 28 and enters valve 3
Control 1. In this case, the valve 31 is preferably operated magnetically. The valve 31 is connected to an inlet pipe 32 which is open to the atmosphere and further extends through an N bacteria filter 33 to the inlet of the valve 31 . Outlet 34 from valve 31 is connected to T-return pipe 22 . Valve 31 is controlled by a signal obtained from transducer 26 via servo circuit 29, lead 36, and conductor 28. Position of valve 31 and T from surroundings
Flow to return pipe 22 and beyond is to pressure transducer 2
It is under the control of 6. A pressure transducer or gauge 41 indicating the instantaneous pressure within the tube 12 mates with the conduit 12 near the gas analyzer connector 13.

In the present invention, the structure of the conduit 12 is special. The length and internal dimensions of the conduit 12 are determined such that its Péclet number is preferably 6 or more, and even 4 or more.

The vector V number is a dogless element, and represents the relationship between the bulk flow due to the gas velocity and the magnitude of gas mass transport through the pipe 12 due to the gas diffusivity, and is expressed by the following equation.

Here, V=, Vsuf0- (cm/sec) L=characteristic flow path length (am) D=mass diffusivity (011127 seconds) Initially, in the present invention, it is applied to the T-wall tube 22 via the inlet 32. Nitrogen was used as pressure compensation gas. However, this nitrogen diffused upstream relative to the breathing gas (oxygen) flowing downstream, thus contaminating the breathing gas entering the gas analyzer 14. This appeared as a reading error. For this reason, we studied gas diffusion, especially mass diffusion. The gas diffusivity is approximately given by the following formula.

Here, T = Humid temperature T''K) M = Molecular weight P = Ambient pressure δAB = Intermolecular interference distance (A) ΩD, AB = Dimensionless relationship between temperature and intermolecular field B ird, S teu+ard, lightf
[Trans-sport Phenom] by Mr.oot
According to the experimental results at enal, δAB, ΩD, and AB can be determined for oxygen and nitrogen. T=298°
If P=1) or 1/760 atm, then DAB
= 165cm2/sec.

According to this relational expression, the distance in the axial direction of the conduit 12 between the center of the hollow connector 13 and the center of the T-wall tube 22 is approximately 13
cm. The diameter of the conduit 12 is 0.93c+n (0,3
75 inches). Flow rate is 5 m at standard temperature and pressure
It is l/akin. The pressure is 1.0 torr and ■ is 0111
The time is 7 seconds, and the Péclet number is 6.0. And there is no upstream flow of polluting gas.

The Péclet number can be selected to a desired value depending on the corresponding relationships of the seven actors involved. In reality, even if there is some contamination, the Péclet number may be low, e.g.
It may be 4 or 5.

Under the disclosed conditions, the Péclet number may be 6 when there is no contamination. The proportions and relative relationships could be set to higher values, i.e., with a Péclet number of 10, but for values above 6 there is no particular benefit with respect to contamination. As long as the above-mentioned relationship is maintained, the structure can be satisfied.

The tube 6 is connected and configured as a person's natural or transparent breathing line. Valve 23 is set to a selected value and has a new resistance value.

The circuitry is then energized and the vacuum pump 21 is operating. Gas flows from the restriction valve 21 to the vacuum source 21,
There is a corresponding pressure drop. Gas flows from the breathing tube 6 through the connector 13 and the gas analyzer 14. This is because the analyzer is also coupled to vacuum source 21 via block 17 and 18 and block 19.

Gas flows continuously to the analyzer so that the analyzer can direct the flow of breathing gas to the analyzer in an instantaneous, current value. The pressure of the diverted gas is indicated by the monitoring stage 41. The pressure and flow in tube 6 is subject to large variations. This means that only the patient is connected to the breathing tube.
Or, it depends on the connection to it, such as whether a breathing device is also connected.

The general gas flow flows through conduit 12 from left to right in the figure and to the vacuum source. The flow rate is controlled, in part, by the position of variable valve 23 and its adjustment amount. conduit 12
The flow from the branch containing pipe 17.18 and the flow from the branch containing pipe 17.18 are combined in block 19, the pressure of which is
to the pressure transducer 26 via. This pressure change becomes a signal and is applied to the valve 31 via the conductor 28, the servo circuit 29, and the conductor 36. This valve correspondingly opens and closes at least partially to alter the inflow of ambient air or other supply gas through leak 32, filter 33, and valve 31 into T-wall tube 22.

Is the amount of this incoming air the pressure of the conduit 12? It is preferable to maintain it at a constant value. A portion of this incoming air flows through the valve 23 to the vacuum source 21.

A portion of this air tends to flow by diffusion upstream or from the T-wall tube 22 to the connector 13, i.e. in the opposite direction to the gas entering from the breathing tube 6, and under special Unless otherwise configured, conduit 12 is placed in two directions of gas flow at the same time. Due to the pressure drop, one of the two flows takes the direction from the left in the drawing. That is, for example, from the connector 11 to the T-wall pipe 22
The flow of <, t is toward the left in the drawing (that is, the flow of T type 2
2 to connector 11 (molecular diffusion flow. Pressure drop flow as well as molecular diffusion flow are fine under some conditions, but under other conditions they are very harmful.

Thus, for example, ambient air flows into the gas analyzer and contaminates the respiratory gas sample provided to the gas analyzer via tube 6. This results in inaccurate results.

In order to inhibit or control such contamination by upstream molecular streams, the dimensions and shape of conduit 12 are carefully chosen to provide the Peclet failure described above. Under the above conditions, T-type 92
The upstream flow of molecular diffusion from connector 2 to connector 11 is no greater than the downstream flow of breathing gas from connector 11 to T-wall tube 22; the gas reaching T-wall tube 22 from tube 32 is cannot diffuse upstream through the connector 13, cannot enter the analyzer 14 through the connector 13,
It does not contaminate the breathing gas during the test and therefore has no effect on the results provided by the gas analyzer.

Such a configuration makes the gas analysis of the analyzer highly accurate by properly controlling the pressure of the flow flowing through conduit 12 despite changes in velocity and pressure due to breathing gas from tube 6. That's a big deal. *There is also no problem of contamination due to the introduction of other gases to regulate and maintain the internal pressure within the conduit 12.

[Brief explanation of the drawing]

The attached drawings show an FR diagram of the flow control device of the present invention, with some parts broken away and some parts shown in cross sections. Explanation of symbols

Claims (6)

[Claims] (1) a source of gas to be analyzed, a source of vacuum, a conduit, means for connecting one end of the conduit to the source of gas, means for connecting the other end of the conduit to the source of vacuum, and a gas analyzer. and means for connecting the gas analyzer in a duct between one end of the conduit and the vacuum source, and means for introducing another gas into the conduit at a predetermined point between the one end of the conduit and the vacuum source. and the conduit having a Péclet number of at least 4 between one end thereof and the predetermined point. 2. The flow control device according to claim 1, further comprising means for restricting the flow of gas from the gas source. 3. A flow control device according to claim 1, further comprising means for closing said duct to restrict flow to said vacuum source. (4) Claim No. (1), (2) or (
3) Flow control device according to item 3). 5. The flow control device according to claim 4, further comprising a pressure transducer placed under the pressure of the conduit to vary the variable valve. (6) The conduit has a Peclet number of about 6 between its one end and the predetermined point.
) to (6).