U.S. patent number 3,628,891 [Application Number 05/071,777] was granted by the patent office on 1971-12-21 for method for the minimization of the effects of pulsations in intermittent pumping systems.
This patent grant is currently assigned to Technicon Corporation. Invention is credited to Robert Dannewitz, Jack Isreeli, Aaron Kassel.
United States Patent |
3,628,891 |
Isreeli , et al. |
December 21, 1971 |
METHOD FOR THE MINIMIZATION OF THE EFFECTS OF PULSATIONS IN
INTERMITTENT PUMPING SYSTEMS
Abstract
New and improved method for minimizing the effects of pulsations
which occur during the operation of intermittent pumping systems is
provided and, as disclosed, is applied to a peristaltic pump which
is utilized in a fluid sample supply, treatment and analysis system
and comprises the minimization of the effects of the pulsation
which occurs each time a pump roller occludes the compressible pump
tube, and the minimization of the effects of the pulsation which
occurs each time a pump roller discontinues the occlusion of the
compressible pump tube.
Inventors: |
Isreeli; Jack (Mamaroneck,
NY), Kassel; Aaron (Brooklyn, NY), Dannewitz; Robert
(Yonkers, NY) |
Assignee: |
Technicon Corporation
(Tarrytown, NY)
|
Family
ID: |
22103521 |
Appl.
No.: |
05/071,777 |
Filed: |
September 14, 1970 |
Current U.S.
Class: |
417/53;
417/477.14 |
Current CPC
Class: |
F04B
43/1223 (20130101); G01N 35/08 (20130101); F04B
11/0075 (20130101) |
Current International
Class: |
F04B
11/00 (20060101); G01N 35/08 (20060101); F04B
43/12 (20060101); F04b 043/12 (); F04b
045/08 () |
Field of
Search: |
;417/53,54,474,475,476,477 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Croyle; Carlton R.
Assistant Examiner: Gluck; Richard E.
Claims
What is claimed is:
1. In a method for minimizing the effects of pulsations in an
intermittent pumping system having a pump which operates by the
alternating intake through pump inlet means of sample fluid and
separating fluid, respectively, to provide a fluid stream which
comprises a series of sample fluid portions spaced by separating
fluid portions, and wherein said pulsations travel in said fluid
stream to said pump inlet means, the steps of, operating said
pumping system to provide for the intake of said sample fluid
through said pump inlet means substantially concomitantly with the
arrival of said pulsations at said pump inlet means.
2. In a method as in claim 1 further comprising, the steps of,
operating said pumping system to respectively provide for sample
fluid portions of substantially the same volume, and to provide for
separating fluid portions of substantially the same volume.
3. In a method as in claim 1 wherein said pump comprises a
progressively occludable pump tube and said method further
comprises, the steps of, operating said pumping system to provide
separating fluid portions of the minimum volume required to occlude
said pump tube.
4. In a method as in claim 2 further comprising, the steps of,
operating said pumping system to provide sample fluid portion
volumes which are greater than said separating fluid portion
volumes.
5. In a method as in claim 4 wherein said pump comprises a
progressively occludable pump tube and said method further
comprises, the steps of, operating said pumping system to provide
separating fluid portions of the minimum volume required to occlude
said pump tube.
6. In a method for minimizing the effects of pulsations in an
intermittent pumping system having a pump, the steps of,
alternately immersing the pump inlet means in different ones of a
plurality of fluids which are successively supplied thereto, and
exposing said pump inlet means to the ambient air, respectively, to
provide a fluid stream which comprises a series of different fluid
portions spaced, in each instance, by a separating fluid portion
which comprises an air segment, and in which fluid stream said
pulsations travel upstream to said pump inlet means, and operating
said pump and said pump inlet means to provide for the immersion of
said pump inlet means in a said fluid substantially concomitantly
with the arrival of said pulsations at said pump inlet means.
7. In a method as in claim 6 further comprising, the steps of,
operating said pump and said pump inlet means to respectively
provide for fluid portions of substantially the same volume, and to
provide for air segments of substantially the same volume.
8. In a method as in claim 6 wherein said pump comprises a
progressively occludable pump tube and said method further
comprises, the steps of, operating said pump and said pump inlet
means to provide air segments of the minimum volume required to
occlude said pump tube.
9. In a method as in claim 7 further comprising, the steps of,
operating said pump and said pump inlet means to provide fluid
portion volumes which are greater than said air segment
volumes.
10. In a method as in claim 9 wherein said pump comprises a
progressively occludable pump tube and said method further
comprises, the steps of, operating said pump and said pump inlet
means to provide air segments of the minimum volume required to
occlude said pump tube.
11. In a method of minimizing the effects of pulsations on the
proportionate merger of a first fluid and a second fluid at the
juncture of the flow path of a first fluid stream which comprises a
series of first fluid portions spaced, in each instance, by a
separating fluid portion, with the flow path of a second fluid
stream, wherein said first fluid stream is intermittently pumped by
a pumping means to result in the occurrence of said pulsations
which travel in said first fluid stream to said flow path juncture,
the steps of, arranging said fluid stream flow paths to provide for
the substantially concomitant arrival of said pulsations and said
separating fluid portions at said flow path juncture.
12. In a method as in claim 11 wherein, the steps of arranging said
fluid stream flow paths comprise the establishment of the length of
said first fluid stream flow path between the outlet side of said
pumping means and said flow path juncture in accordance with the
flow rate through said first fluid stream flow path to provide for
said substantially concomitant pulsations and separating fluid
portions arrivals at said flow path juncture.
13. In a method for respectively minimizing the effects of
pulsations on a first fluid stream, and on the proportionate merger
of said first fluid stream and a second fluid stream at the
juncture of the flow paths thereof, in an intermittent pumping
system having a pump which operates by the alternating intake
through pump inlet means of said first fluid and a separating
fluid, respectively, to provide said first fluid stream which
comprises a series of fluid portions spaced, in each instance, by a
separating fluid portion, and wherein said pulsations travel in
said first fluid stream to said pump inlet means and said flow
paths juncture, respectively, the steps of, operating said pumping
system to provide for the intake of said first fluid through said
pump inlet means substantially concomitantly with the arrival of
said pulsations at said pump inlet means, and arranging said fluid
stream flow paths to provide for the substantially concomitant
arrival of said pulsations and said separating fluid portions at
said flow paths juncture.
14. In a method as in claim 13 further comprising, the steps of,
operating said pumping system to respectively provide for fluid
portions of substantially the same volume, and to provide for
separating fluid portions of substantially the same volume.
15. In a method as in claim 13 wherein said pump comprises a
progressively occludable pump tube and said method further
comprises, the steps of, operating said pumping system to provide
separating fluid portions of the minimum volume required to occlude
said pump tube.
16. In a method as in claim 14 further comprising, the steps of,
operating said pumping system to provide fluid portion volumes
which are greater than said separating fluid portion volumes.
17. In a method as in claim 16 wherein said pump comprises a
progressively occludable pump tube and said method further
comprises, the steps of, operating said pumping system to provide
separating fluid portions of the minimum volume required to occlude
said pump tube.
18. In a method as in claim 15 wherein, the steps of arranging said
fluid stream flow paths comprise the establishment of the length of
said first fluid stream flow path between the outlet side of said
pumping means and said flow path juncture in accordance with the
flow rate through said first fluid stream flow path to provide for
said substantially concomitant pulsations and separating fluids
portions arrivals at said flow path juncture.
19. In a method as in claim 17 wherein, the steps of arranging said
fluid stream flow paths comprise the establishment of the length of
said first fluid stream flow path between the outlet side of said
pumping means and said flow path juncture in accordance with the
flow rate through said first fluid stream flow path to provide for
said substantially concomitant pulsations and separating fluid
portions arrivals at said flow path juncture.
20. In a method for respectively minimizing the effects of
pulsations on a first fluid stream, and on the proportionate merger
of said first fluid stream and a second fluid stream at the
juncture of the flow paths thereof, in an intermittent pumping
system having a pump, the steps of, alternately immersing the pump
inlet means in different ones of a plurality of fluids which are
successively supplied thereto, and exposing said pump inlet means
to the ambient air, respectively, to provide a first fluid stream
which comprises a series of different fluid portions spaced, in
each instance, by a separating fluid portion which comprises an air
segment, and wherein said pulsations travel in said first fluid
stream to said pump inlet means and to said flow paths juncture,
respectively, operating said pump and said pump inlet means to
provide for the immersion of said pump inlet means in a said fluid
substantially concomitantly with the arrival of said pulsations at
said pump inlet means, and arranging said fluid stream flow paths
to provide for the substantially concomitant arrival of said
pulsations and said separating fluid portions at said flow paths
juncture.
21. In a method as in claim 20 further comprising, the steps of,
operating said pump and said pump inlet means to respectively
provide for air segments of substantially the same volume, and to
provide for air segments of substantially the same volume.
22. In a method as in claim 20 wherein said pump comprises a
progressively occludable pump tube and said method further
comprises, the steps of, operating said pump and said pump inlet
means to provide air segments of the minimum volume required to
occlude said pump tube.
23. In a method as in claim 21 further comprising, the steps of,
operating said pump and said pump inlet means to provide fluid
portion volumes which are greater than said air segment
volumes.
24. In a method as in claim 23 wherein said pump comprises a
progressively occludable pump tube and said method further
comprises, the steps of, operating said pump and said pump inlet
means to provide air segments of the minimum volume required to
occlude said pump tube.
25. In a method as in claim 24 wherein, the steps of arranging said
fluid stream flow paths comprise the establishment of the length of
said first fluid stream flow path between the outlet side of said
pumping means and said flow path juncture in accordance with the
flow rate through said first fluid stream flow path to provide for
said substantially concomitant pulsations and separating fluid
portions arrivals at said flow path juncture.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to new and improved method for minimizing
the effects of pulsations which occur during the operation of
intermittent pumping systems.
2. Description of the Prior Art
In any intermittent pumping system in the nature, for example, of a
peristaltic pumping system or a pressure-pumped exchange valve and
pilot fluid pumping system, it may be understood that intermittent
pulsations in the provided flow rate will, of necessity, occur. For
use, for example, in automatic, sequentially operable substantially
constant flow rate fluid sample supply, treatment and analysis
means of the nature disclosed in U.S. Pat. No. 3,241,432 issued
Mar. 22, 1966 and assigned to the assignee hereof, and which are
operable to supply, treat and analyze a stream consisting of
successive sample portions, it may be understood that such
intermittent pumping systems may be utilized without significant
regard for such pulsations because of the minimization of the
effects of the latter as provided by the relatively long sample
portion sampling times and the relatively high flow rates and
volumes of said sample portions, which, in essence, combine to
function to average or spread out such effects over relatively long
periods of time and throughout relatively large sample portion
volumes to thereby render the same tolerable. For use of such
intermittent pumping systems with newly developed and highly
improved versions of such sample supply, treatment and analysis
means which are operable, to significant advantage, at
substantially reduced sample portion sampling times and with
substantially reduced sample portion flow rates and volumes,
however, it may be understood that a method must be provided to
minimize the effects of such pulsations, or that unacceptable
variations in the essential sample portion phasing and in the
essential sample portion-sample treatment fluid proportioning will
result.
OBJECTS OF THE INVENTION
It is, accordingly, an object of this invention to provide new and
improved method to minimize the effects of pulsations which occur
during the operation of intermittent pumping systems.
Another object of this invention is to provide method as above
which may be applied to said intermittent pumping systems without
structural modification of the latter.
A further object of this invention is the provision of method as
above which is particularly adaptable for use in intermittent
pumping systems which form part of automatically operable,
substantially constant flow rate fluid sample supply, treatment and
analysis means.
SUMMARY OF THE INVENTION
As specifically disclosed herein by way of illustration, the method
of the invention is applied to a peristaltic pump which is
operable, in a fluid sample analysis system, through the
progressive occlusion of a compressible pump tube by a plurality of
substantially equally spaced pump rollers to pump fluid sample
portions in a precisely phased successive stream thereof from fluid
sample supply means to fluid sample treatment and analysis means. A
separating fluid portion which includes an air segment is provided
in said fluid sample portion stream intermediate adjacent fluid
sample portions. A pulsation in the pump delivery rate occurs each
time a said pump roller occludes said pump tube, and each time a
said pump roller discontinues the occlusion of said pump tube. Said
fluid sample portions are supplied to said compressible pump tube
by the aspiration thereof from sample container means through the
inlet end of a connected sample offtake device which functions as
pump inlet means, and each of said fluid sample portions is treated
downstream of said compressible tube pump by the mixture thereof in
precisely determined proportion with a sample treatment fluid
through the merger of a stream of the latter with said sample
portion stream. The method of the invention minimizes the effects
of the first-mentioned pulsation by insuring, through proper
control of the operational timing of said pump rollers and said
pump inlet means flow path length determination, that said offtake
device inlet end is not exposed to the air at the time said
pulsation arrives thereat to thus insure the aspiration of the
separating fluid portion air segment of the required volume. The
method of the invention minimizes the effects of the
second-mentioned pulsation by insuring, through proper
determination of the flow path length between said pump roller as
the latter discontinues said occluding contact, and the point at
which said sample portion stream merges with said sample treatment
fluid stream, that one of said separating fluid portion air
segments is disposed at said merger point at the time of the
arrival thereat of said pulsation to thus minimize the extent of
the change, if any caused thereby in said sample portion-sample
treatment fluid proportion and, in any event, restrict the same to
the beginning or end part of each of said sample portions to render
the same incapable of modifying the recorded sample portion
analysis results.
DESCRIPTION OF THE DRAWINGS
The above and other objects of he invention are believed made clear
by the following detailed description thereof taken in conjunction
with the accompanying drawings wherein:
FIG. 1 is a flow diagram illustrating the application of the method
of the invention to the operation of peristaltic pump means in a
fluid sample supply, treatment and analysis system, and depicts
said pump means in a first operational position thereof;
FIG. 2 is a flow diagram depicting the peristaltic pump of FIG. 1
in a second operational position thereof;
FIG. 3 is a graph depicting pump delivery plotted against time and
illustrates the pump pulsations of interest;
FIG. 4 is a graph depicting treated sample portion optical density
plotted against time and illustrates the minimization of the
effects of one of the pulsations of FIG. 3; and
FIG. 5 is a flow diagram illustrating fluid flow through the
peristaltic pump of FIG. 1 when the same is used in a somewhat
differently operable fluid sample supply, treatment and analysis
system.
DETAILED DESCRIPTION OF THE INVENTION
Referring now to FIG. 1, new and improved sample supply system
constructed and operative in accordance with the teachings of this
invention are indicated generally at 8, and comprise compressible
tube pump means as indicated generally at 10 and operatively
associated sample supply means as indicated generally at 12.
The sample supply means 12 may, for example, take the form of those
shown and described in U.S. Pat. No. 3,134,263 issued May 26, 1964
to Edward B. M. DeJong, and comprise a turntable 14 upon which is
disposed a generally circular array of sample containers 16. A
sample offtake device is indicated generally at 18 and comprises a
sample offtake tube 20 and offtake tube operating-means 22,
respectively. A wash liquid receptacle 24 is disposed as shown
adjacent the turntable 14, while sample supply device drive means
are indicated at 26 and are operative to drive each of the
turntable 14 and the sample offtake device 18 as indicated by the
dashed lines extending therebetween.
In operation, the turntable 14 is intermittently rotated, or
indexed, to present each of the sample containers 16 in turn to the
sample offtake device 18, while the latter is operated to immerse
the inlet end or offtake tube 20 in a thusly presented sample
container for a predetermined period of time to aspirate (as
described in detail hereinbelow) a measured volume of the sample
therefrom, to then transfer the said offtake tube inlet end through
the ambient air for immersion in the wash liquid receptacle for a
predetermined period of time to thus aspirate a measured volume of
ambient air followed by a measured volume of said wash liquid, and
to then again transfer the said offtake tube inlet and through the
ambient air for immersion in the next-presented sample container 16
for a predetermined period of time to thus aspirate aNother
measured volume of ambient air and commence the aspiration of a
measured volume of the sample from said next-presented sample
container.
As a result, it may be understood that a stream S consisting of
successive ones of portions of said samples of substantially equal
predetermined volume as spaced, in each instance, by a segment of
air A, a segment of wash liquid W and a segment of air A,
respectively, will be supplied to the offtake tube 20.
The compressible tube or peristaltic pump 10 may, for example, take
the general form of that shown and described in U.S. Pat. No.
3,227,091 issued Jan. 4, 1966 to Jack Isreeli et al., and comprises
spaced pump tube mounting blocks as indicated at 32 and 34.
A compressible pump tube 36, which is made from any suitably
resilient material of appropriate strength characteristics in the
nature, for example, of silicone rubber, is extended as shown
between the said pump tube mounting blocks and affixed thereto by
means of the placement of said pump tube in nonillustrated aligned
mounting grooves formed in said pump tube mounting blocks, and the
attachment of collar elements 38 and 40, as shown to opposite end
portions of said pump tube, all in a manner made clear in said U.S.
Pat. No. 3,227,091. The inlet end of the compressible pump tube 36
is connected as indicated at 41 to the outlet end of the sample
offtake tube 20.
A pump roller assembly is indicated generally at 42 and comprises
an endless chain 44 which is disposed as shown around a chain guide
member 46 and is driveable therearound in the indicated clockwise
direction through the driven rotation of a chain drive sprocket
48.
A plurality of substantially equally spaced pump rollers 50A, 50B,
50C and 50D are rotatably mounted in any convenient manner on
endless chain 44 as shown, whereby may be understood that those of
said rollers which are, at any given point in time, mounted on the
upper throw of the endless chain 44 will be movable with the latter
in the direction from left to right as seen in FIG. 1. Although for
simplicity of illustration only one chain and drive sprocket are
depicted, it may be understood that at least two of the same would
be provided in spaced, general alignment, and that the respective
pump rollers would, of course, extend therebetween.
A pump platen is indicated at 52 and may be understood to be
movable, as by pivotal movement, from a nonillustrated "open"
position thereof to the depicted "closed" position thereof wherein
the pump tube 36 will be disposed as shown in firm contact with the
undersurface of said platen, and will be forced to conform with the
configuration of the bottom surface 54 of said groove and pressed
thereby against the respective relevant rollers 50, all again as
described in detail in said U.S. Pat. No. 3,227,091.
Pump drive means, which may, for example, take the form of any
suitable electric motor, are indicated at 56, and are operatively
connected, as indicated by the dashed line, to the chain drive
sprocket 48 to drivingly rotate the latter. In addition, and for
reasons described in detail hereinbelow, the operation of sample
supply device drive means 26 is synchronized with the operation of
the pump drive means 56, and this may be understood to be indicated
in the drawings by the extension of lead 58 therebetween.
Alternatively, it is believed clear that a single drive means in
the nature of a suitable electric drive motor may be provided and
operatively connected, as by conventional mechanical connecting
means, to both the pump 10 and the sample supply device 12 to drive
the same in the described synchronized manner.
With the respective pump components arranged and operative as
described, it may be understood that driven, clockwise rotation of
the chain drive sprocket 48 will effect movement of the rollers 50
affixed to the upper throw of endless chain 44 from left to right
as seen in FIG. 1 with the result that the compressible pump tube
36 will be progressively compressed or occluded thereby in said
direction to in turn pump fluids therethrough. Accordingly, may be
understood that the successive sample stream S will be supplied as
indicated from the compressible pump tube 36 to a sample stream
supply conduit 62, which is connected to the former as shown at 64,
for supply through said sample supply conduit as indicated to the
nonillustrated sample treatment and analysis means. In addition, it
is reiterated that the sample portions which constitute this sample
portion stream will be spaced, each from the other, by a separating
fluid portion which, in this instance, will be constituted as
described by a segment of air A1, a slug of wash liquid W, and a
segment of air A2, arranged in that order.
Sample treatment fluid supply means are indicated generally at 66
and may be understood to function to supply a sample treatment
fluid to the sample portion stream supply conduit 62 for mixture
therewithin in carefully predetermined proportion with each of said
sample portions being pumped therethrough.
The sample treatment fluid supply means 66 may, for example, take
the general form of those shown and described in the copending
application for U.S. Pat. Ser. No. 120,153 of Edward B. M. DeJong
filed Mar. 2, 1971 and assigned to the assignee hereof
(continuation in part of U.S. Pat. Ser. No. 712,431 filed Mar. 12,
1968, now abandoned) and, as such, will comprise a tank 68 of air
at suitable pressure, as, for example, 2,200 p.s.i. connected as
shown by conduit 70 through suitable pressure regulator means 72 to
a T-fitting 74 to maintain the latter at substantially constant
pressure in the order, for example, of 66.8 cm. Hg. For use in
applications wherein the respective samples are constituted by
blood serum samples from different patients, the sample treatment
fluid of interest may, for example, be constituted by a
color-producing reagent liquid which, when mixed with said sample
portions, will enable the respective colorimetric quantitative
analyses thereof with respect to a predetermined blood sample
constituent, all as described in greater detail in said U.S. Pat.
No. 3,241,432.
A conduit 78 extends as shown from outlet of the T-fitting 74
through the screw-on cover 80 of a reagent liquid flask 82 to thus
pressurize the interior of the latter at said substantially
constant pressure. An outlet conduit 84 connects the interior of
the flask 82 to the inlet of a precisely calibrated high flow
resistance coil 86, the outlet of which is in turn connected as
shown by reagent liquid supply conduit 88 to one inlet of a
T-fitting 90 which is interposed in the sample portion stream
supply conduit 62.
The other outlet of the T-fitting 74 is connected as shown by
conduit 92 to the inlet of a precisely calibrated high flow
resistance coil 94, and the outlet of the latter is connected by
air supply conduit 96 to a T-fitting 98 which is interposed as
shown in the reagent liquid supply conduit 88.
For use as described in greater detail hereinbelow in automatically
operable, blood serum sample treatment and analysis means, the high
flow resistance coil 86 will preferably be disposed in a
temperature control bath as indicated in dashed lines at 99 to
maintain the temperature thereof at a suitable, substantially
constant level as, for example, 37.degree. C. to in turn maintain
the temperature, and accordingly the viscosity and flow rate of the
reagent liquid flowing therethrough at substantially constant,
predetermined values. If necessary, and/or desired, the respective
reagent liquid flask 82 and portions at least of the respective
conduits 84 and 88 may also be immersed in said temperature control
bath.
By this arrangement is believed made clear that the pressurized air
from tank 68 will be effective to pump the reagent liquid R from
the flask 82 at a substantially constant, predetermined flow rate
through the high flow resistance coil 86 and therefrom, through
reagent liquid supply conduit 88, to the sample stream supply
conduit 62 for merger therewithin with the sample portion stream S
flowing through the latter. Concomitantly, it may be understood
that the pressurized air from tank 68 will be flowed, again at
substantially constant, predetermined flow rate, through high flow
resistance coil 94 and therefrom through air supply conduit 96 for
merger with the reagent liquid stream flowing in reagent supply
conduit 88 to air segment the same as shown to promote proper
mixing thereof with the sample stream S upon the merger thereof as
discussed hereinabove.
Although compressible tube proportioning pumps in the nature of the
pump 10 have, to date, proven preferable for use in automatically
operable, substantially constant flow rate sample treatment and
analysis means of the nature disclosed in said U.S. Pat. No.
3,241,432, it may be understood that there is one operational
characteristic of said pumps which must be taken in consideration
for such use, and especially when applied to improved versions of
said sample treatment and analysis means which are operable at
substantially reduced sample volumes and substantially increased
sample analysis rates. More specifically, and as seen in FIG. 3
wherein the graph 100 represents proportioning pump delivery as
plotted against time for the travel of one of the compressible pump
rollers 50 through one tube compressing cycle thereof, it may be
understood that pulsations as indicated at 102 and 104 will
respectively occur in said pump delivery rate as the said pump
roller makes contact with and occludes the pump tube 36 at the
commencement of the pumping cycle of interest, and as the said pump
roller terminates the occluding contact thereof with said
compressible pump tube at the termination of said pumping
cycle.
Sample treatment and analysis means of the nature discussed may be
understood to be satisfactorily operable only at substantially
constant flow rate, and to further depend for satisfactory constant
flow rate, and to precise proportioning between each of the sample
portions and the reagent liquid which is merged therewith, and upon
the substantially precise maintenance of a predetermined phase
relationship between the respective sample portions. Accordingly,
it becomes essential that the effects of pulsations as indicated at
102 and 104 in FIG. 3 upon such flow rate, proportioning and sample
portion phase relationship be minimized, if not altogether
removed.
Considering first the pulsation 102 which occurs as set forth
hereinabove as a pump roller commences the occlusion of the
compressible pump tube 36, it may be understood that this point in
the operation of the compressible tube pump 10 as illustrated in
FIG. 1 wherein the pump roller 50B is depicted as commencing the
occlusion of the compressible pump tube 36. At this occurs, it may
be understood that the pulsation 102 of FIG. 3 will, of course,
travel in both directions from the point of roller-pump tube
contact through the sample portion stream S then flowing in said
pump tube. The travel of this pulsation in the direction from left
to right as seen in FIG. 1, or, that is to say, the downstream
direction, will be terminated at the roller 50A since the latter
is, at this point in time, fully occluding the compressible pump
tube 36 to thereby render substantially impossible further travel
of said pulsation in this direction.
The travel of this pulsation in the direction from right to left as
seen in FIG. 1 or, that is to say, the upstream direction will,
however, be unrestricted to and through the inlet end of the sample
offtake tube 20. As a result, it may be understood that the said
offtake tube, the turntable 14 and the compressible pump tube 10
are arranged in accordance with the teachings of this invention, as
through careful predetermination and control of the operational
timing of the respective sample supply device drive means 26 and
the pump drive means 56, to insure that the said offtake tube inlet
end is not exposed to the ambient air at the time that the
pulsation 102 reaches the said offtake tube inlet end. More
specifically, and bearing in mind the substantial importance of
proper phasing of the respective sample portions which are pumped
through the compressible pump tube 36, and the obviously essential
function of the respective air segments A of predetermined uniform
volume in maintaining such phasing and, in conjunction with the
slug of wash liquid W, in providing for intersample portion
cleansing to inhibit the contamination of a succeeding sample
portion by the residue of a preceding sample portion, it is
believed clear that if the inlet end of the offtake tube 20 is
exposed to the ambient air at the time the said pulsation arrives
thereat, the effect of the latter will, of course, be to
substantially reduce, if not eliminate, the amount of air which is
at that time aspirated to form an air segment A.
If the amount of air aspirated is simply reduced but is still
adequate to form a leading air segment as indicated at A1 in FIG. 1
of at least the minimum volume required to occlude the nonuniform
tube 36, it may be understood that the said air segment A1 will be
smaller than and thus of nonuniform volume with regard to the
trailing air segment as indicated at A2, whereby the essential
sample portion phase relationship may be modified to obvious
disadvantage. If, on the other hand, the amount of air aspirated is
reduced to the extent that insufficient air is provided for the
formation of an air segment A of minimum volume to fully occlude
the pump tube 36--thereby resulting only in the formation of a
suspended air bubble--or if no air is aspirated at all, it is
believed clear that the essential inter sample portion cleansing
and sample portion separating functions of the air segment A which
was to have been formed will also be eliminated along with the
phase relationship destruction as discussed hereinabove.
To better illustrate this, if it is assumed, for example, that a
total of 12 seconds are available for the aspiration of each of the
sample portions and the separating fluid portion which is
constituted by the respective air segments A and slug of wash
liquid W which precede the same, that only 1.5 of these 12 seconds
are available for the aspiration of said air segments and wash
liquid slug, that the pulsation 102 is of 1 second duration, and
that the sample supply system 8 is arranged to operate to aspirate
air to form segments A of the minimum volume required to occlude
the compressible pump tube 36, it is believed clear that the
arrival of the pulsation 102 at the inlet end of offtake tube 20
during that portion of the 1.5 seconds air-wash liquid aspiration
time in which air is being aspirated will, in all probability,
result in the aspiration of an air volume, if any, which is
insufficient to occlude the compressible pump tube 36 to obviously
unacceptable effect as discussed in detail directly
hereinabove.
Preferably, the sample offtake tube 20 will be arranged as
illustrated so that the inlet end thereof will be immersed in a
sample container 16 generally intermediate the aspiration of a
sample portion at the time of the arrival of the pulsation 102 at
said inlet end, with resultant substantial absorption of said
pulsation to render the effects of the latter substantially
undetectable during the steady state flow rate portion of sample
stream flow.
Alternatively, the sample offtake tube 20 may be arranged so that
the inlet end thereof will be immersed in the wash liquid
receptacle 24 at the time of arrival of the pulsation 102 thereat
although this may, of course, prove unacceptable in instances as
discussed hereinabove wherein the total time for wash liquid slug
aspiration is so short in relation to the duration of the pulsation
102 that the former cannot accommodate the latter and still provide
for the aspiration of a wash liquid slug W of suitable volume.
Considering now the effect of the pulsation 104 which occurs as set
forth hereinabove as a pump roller discontinues the occlusion of
the compressible pump tube 36, it may be understood that this point
in the operation of the compressible tube pump 10 is illustrated in
FIG. 2 wherein the pump roller 50A is depicted as discontinuing
occluding contact with said pump tube. Travel of the resultant
pulsation 104 in the upstream direction through the sample portion
stream S will be substantially terminated at the pump roller 50B
which is, at this point in time, occluding the compressible pump
tube 36. Travel of this pulsation in the downstream direction
through said sample portion stream to and through the T-fitting 90
wherein said stream is being merged with the stream of reagent
liquid R from reagent liquid supply conduit 88 will, however,
occur, to thus give rise to the possibility of improper sample
portion-reagent liquid proportioning. This is to say that if said
pulsation arrives at said T-fitting concomitantly with a sample
portion and a segment R of reagent liquid, the attendant momentary
reduction in the sample portion stream flow rate will, of course,
result in the merger therewith of a substantially greater
proportion of reagent liquid than that desired with attendant
inordinate dilution of said sample portion. To prevent this from
occurring or, to at least minimize the effects thereof upon sample
portion analysis as discussed in greater detail hereinbelow, it may
be understood that the length of the fluid flow path through the
compressible pump tube 36 from the point thereon whereat the
respective pump rollers discontinue occluding contact therewith as
illustrated by the position of pump roller 50A in FIG. 1, and the
T-fitting 90, is precisely predetermined in accordance with the
fluid flow rate therethrough to insure that the arrival of the
pulsation 104 at the said T-fitting will occur substantially
concomitantly with the arrival of an air segment A1 or A2 thereat.
As a result, it may be understood that disruptive effects, if any,
of the pulsation 104 upon the requisite substantially precise
sample portion-reagent liquid proportioning will be minimized and
will, in any event, occur at the beginning or end of each of said
sample portions so as not to interfere with the results of the
analysis thereof.
More specifically--and bearing in mind that the nonillustrated
sample treatment and analysis means of the type discussed include
colorimeter means through which the appropriately treated sample
portions which then constitute the sample portion stream S are
successively flowed, and operatively connected null balance-type
strip chart recorder means which provide a record of the
colorimetric analysis of said sample portion, all as described in
detail in said U.S. Pat. No. 3,241,432--FIG. 4 which depicts a
graph 106 of treated sample portion optical density plotted against
time for the successive passage of three treated sample portions
through the colorimeter flow cell is believed to make clear that it
is only the result of the colorimetric quantitative analysis of the
respective generally central parts of said treated sample portions
which are recorded to thereby make clear that any nonrepresentative
changes in sample portion optical density which might occur as a
result of improper sample portion-reagent liquid proportioning at
the beginning or end of each sample portion will have no effect
upon the recorded results of interest.
Although disclosed in FIGS. 1 and 2 as functioning to aspirate a
segment of air A, a segment of wash liquid W and a segment of air
A, respectively, prior to the aspiration of each of the sample
portions from the respective sample containers 16, it is believed
clear that the sample portion supply means 12 could be modified by
the deletion of the wash liquid reservoir 24 and the arrangement of
the sample offtake means 18 to aspirate repeated small volumes of
each of the samples as spaced, each from the other, by a small
segment of air A, prior to the aspiration of the main body of the
sample portion--with said small sample portion volumes functioning
in the manner of the wash liquid in conjunction with said air
segments as the separating fluid portion to remove the residue, if
any, of the preceding sample portion and inhibit the contamination
of the succeeding sample portion thereby--and that the teachings of
the invention should be equally applicable to such system. More
specifically, and as seen in FIG. 5 which illustrates the sample
portion stream which would result from such operation, it may be
understood that the respective turntable 14, sample offtake tubes
20, proportioning pump 10 and T-fitting 90 would respectively again
be arranged as described in detail hereinabove to insure that the
offtake tube inlet end would be immersed in a sample container
concomitantly with the arrival thereat of the pulsation 102 for
each of the pump rollers 50, and to insure that the arrival of the
pulsation 104 for each of the pump rollers at the T-fitting 90
would occur substantially concomitantly with the arrival of one of
said air segments A thereat.
Preferably, the apparatus of the invention are arranged as
illustrated and described so that each of the pump rollers makes
occluding contact with the compressible pump tube 36 generally
intermediate a sample portion as shown as at S1, S2, S3, etc.,
rather than at a separating fluid portion, to thus prevent the
breaking up of the respective air segments A by such occluding
contact into air bubbles which may not reform as air segments and
thus would no longer function to occlude the compressible pump tube
36 to very significant disadvantage as discussed in detail
hereinabove.
Too, and although disclosed as involving one pump tube occluding
contact by a pump roller per sample portion, it is believed clear
that the proportioning pump 10 may alternatively be arranged to
operate with one such pump tube occluding contact per two or more
sample portions to, in any event, minimize the number of pump
roller-compressible pump tube contacts per sample portion and thus
minimize compressible pump tube wear as should be obvious.
In addition, and although disclosed by way of illustration as
applied to a sample supply system which operates to supply blood
serum samples for mixture with a suitable color-producing reagent
liquid, it is believed clear that the teachings of this invention
would be equally applicable to sample supply systems which operate
to supply a wide variety of different sample treatment fluids.
Further, and although disclosed in conjunction with a sample supply
system which utilizes a compressible tube or peristaltic
proportioning pump, it may be understood that the teachings of this
invention would be equally applicable to such system wherein it
utilized another and different form of pumping means which gave
rise to pulsations in the nature of those discussed.
While we have shown and described the preferred embodiment of our
invention, it will be understood that the invention may be embodied
otherwise than as herein specifically illustrated or described, and
that certain changes in the form and arrangement of parts and in
the specific manner of practicing the invention may be made without
departing from the underlying idea or principles of this invention
within the scope of the appended claims.
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