U.S. patent number 3,831,618 [Application Number 05/317,753] was granted by the patent office on 1974-08-27 for apparatus for the precision metering of fluids.
This patent grant is currently assigned to Abbott Laboratories. Invention is credited to Max D. Liston.
United States Patent |
3,831,618 |
Liston |
August 27, 1974 |
APPARATUS FOR THE PRECISION METERING OF FLUIDS
Abstract
There is disclosed a first capillary conduit having a minute
aperture therein, the aperture dividing the first conduit into a
separate and a common section, there being a first fluid conducting
path formed through the separate and common sections. A second
capillary conduit has one end thereof intersecting the first
conduit and mating with the minute aperture to form a second fluid
conducting path through the second conduit and the common section
of the first conduit. The minute aperture forms a first precise
interface between the first fluid path and the second conduit. The
capillary cross-section of the first conduit separate section
adjacent the minute aperture forms a second precise interface
between the second fluid conducting path and the separate section,
whereby fluid can traverse the first fluid path substantially free
from contamination from fluids adjacent the first precise interface
and fluids can traverse the second path substantially free from
contamination from fluid adjacent the second precise interface.
Inventors: |
Liston; Max D. (Newport Beach,
CA) |
Assignee: |
Abbott Laboratories (North
Chicago, IL)
|
Family
ID: |
23235124 |
Appl.
No.: |
05/317,753 |
Filed: |
December 22, 1972 |
Current U.S.
Class: |
137/154;
73/864.12; 73/864.22; 422/82; 422/926 |
Current CPC
Class: |
G01N
35/1016 (20130101); G01F 11/029 (20130101); B01L
3/0227 (20130101); G01N 1/38 (20130101); Y10T
137/2931 (20150401) |
Current International
Class: |
B01L
3/02 (20060101); G01N 1/38 (20060101); G01N
1/00 (20060101); G01F 11/02 (20060101); F16k
019/00 () |
Field of
Search: |
;137/154 ;23/258.5,259
;73/423A,425.6 ;417/92 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Nilson; Robert G.
Attorney, Agent or Firm: Madsen; Raymond L.
Claims
What is claimed is:
1. Apparatus for the precision metering of fluids, comprising:
a first capillary conduit having a minute aperture therein, said
aperture dividing said first conduit into a separate and common
section, said first conduit forming a first fluid conducting path
through said separate and common section;
a second capillary conduit having one end thereof intersecting said
first conduit and mating with said minute aperture to form a second
fluid conducting path through said second conduit and said common
section of said first conduit, said minute aperture forming a first
precise interface between said first fluid path and said second
conduit, and the capillary cross section of said first conduit's
separate section adjacent said minute aperture forming a second
precise interface between said second fluid conducting path and
said separate section whereby fluid can traverse said first path
substantially free from contamination from fluids adjacent said
first precise interface and fluids can traverse said second path
substantially free from contamination from fluids adjacent said
second precise interface;
a first syringe connected to the end of said first conduit separate
section, said first syringe having a movable piston to change the
volume thereof whereby fluids can be aspirated and dispersed
through said first fluid path;
a second syringe connected to the end of said second conduit, said
second syringe having a movable piston to change the volume thereof
whereby fluids can be aspirated and dispersed through said second
fluid path;
a first fluid contained within said first syringe and within said
first conduit separate section up to said second precise interface
whereby decreasing the volume of said first syringe by a precise
amount forces said first fluid past said second precise interface
and into said first conduit common section thereby displacing any
fluid contained in said common section; and
a second fluid contained in said second syringe and within said
second conduit and said common section whereby increasing the
volume of said second syringe aspirates through said common section
and into said second conduit a test fluid into which the end of
said common section is immersed, said test fluid in said common
section being displaced therefrom by said first fluid, and whereby
decreasing said volume of said second syringe in metered increments
dispenses said test fluid in precise amounts from said second
conduit into said common section wherefrom said precise amounts may
be displaced by said first fluid.
2. The apparatus as described in claim 1 wherein said second fluid
is a silicone oil.
3. The apparatus as described in claim 2 wherein said first fluid
is a saline solution and said test fluid is blood serum.
4. The apparatus as described in claim 3 further including;
first coupling means connected to said piston of said first
syringe; and
a first digital stepping motor connected to said first coupling
means whereby said piston of said first syringe is moved to
increase and decrease the volume of said first syringe.
5. The apparatus as described in claim 4 further including:
second coupling means connected to said piston of said second
syringe; and
a second digital stepping motor connected to said second coupling
means whereby said piston of said second syringe is moved to
increase and decrease the volume of said second syringe.
6. The apparatus as described in claim 5 whereby each of said first
and second coupling means, respectively, is a screw drive mechanism
comprising:
a threaded shaft attached to and turned by said digital stepping
motor; and
means having a threaded opening therein for engaging said threaded
shaft, said means being attached to said piston of said syringe
whereby said volume of said syringe is increased and decreased.
7. The apparatus as described in claim 6 further including:
a pair of electronic circuit means each being connected to one
digital motor for driving said digital motor; and
a pair of control means each separately attached to one of said
pair of electronic circuit means for generating a coded electronic
signal to said one of each pair of circuit means whereby each of
said digital motors is driven in steps related to said coded
signal.
8. The apparatus as described in claim 7 further including:
a reservoir syringe for containing a reserve of saline solution;
and
a fluid port located in the side of said second syringe and
connected to said reservoir syringe for receiving fluid from said
reservoir syringe.
9. The apparatus as described in claim 8 further including:
a reservoir syringe for containing a reserve of silicone oil fluid;
and
a fluid port located in the side of said first syringe and
connected to said reservoir syringe for receiving fluid from said
reservoir syringe.
Description
The present invention relates to the precision aspiration and
dispersion of fluid and more particularly to sample aspirating and
dispensing systems for chemical analysis of blood serum.
In the field of chemical analysis of blood serum, it has been the
general practice to employ automated and semiautomated equipment to
perform the desired chemical and analytical tests upon blood serum.
These automated systems duplicate actual test tube procedures. Each
test is treated as a discrete entity and must be free from
cross-contamination or carry-over between the various chemical
tests performed. In these automated systems, samples generally are
placed in small cups that are positioned on a movable sample table.
In order to perform the desired test, a predetermined quantity of
sample must be dispensed into an individual reaction tube. These
reaction tubes are advanced by a conveyor system through a series
of reaction stations where reagents are added, as required, and
reactions proceed under precise temperature control. The contents
of each reaction tube are sequentially scanned colorimetrically to
provide a measurement of concentration or reaction activity. An
essential and critical part of the automated blood chemistry system
is the serum aspirating and dispensing apparatus. This apparatus
aspirates the serum sample from the sample cup and dispenses it
into the reaction tubes. These functions have been accomplished by
a hydraulic system which gives a high degree of precision and
accuracy. Initially, a serum arm moves over the sample table and an
aspiration-dispensing needle travels to a pick-up position. It has
been the practice to introduce an air-interface between the
hydraulic fluid which is generally de-ionized water and the serum
aspirated into the apparatus. The air interface prevents any mixing
between the de-ionized water and the serum. In one prior art
system, after the required amount of sample is aspirated, a
delivery is made back into the sample cup to assure that all test
deliveries will be correct. The arm then moves over the reaction
tube and programmed deliveries of predetermined amounts of serum
are deposited into each individual reaction tube. When sample
dispensing into the reaction tube is completed, the needle is
washed and the system is flushed with the de-ionized water. In a
typical system, the amount of sample aspirated is about 0.25
milliliters, or 250 lambda, plus a volume for each test to be
performed, which averages about 0.05 milliliters or 50 lambda.
Therefore, the total sample volume required ranges from 0.3
milliliters for one test and 1.05 milliliters for 16 tests.
Although the serum sample aspirating and dispensing devices have
served the purpose, they have not proved entirely satisfactory
under all conditions of service for the reason that considerable
difficulty has been experienced in precisely controlling the
aspirated and dispensed amounts of serum to accuracies approaching
1/2 lambda. These problems have resulted from the volume
inaccuracies produced by the cushioning effect of the air interface
between the de-ionized water hydraulic fluid and the serum and in
the formation of surface tension drops of serum at the end of the
aspirating and dispensing needle, which can be of a size having a
volume of 10 lambda.
Those concerned with the development of serum aspirating and
dispensing systems have long recognized the need for aspirating
dispensing apparatus which accurately controls serum volumes
approaching 1/2 lambda in precision and accuracy. The present
invention fulfills this need.
One of the most critical problems confronting designers of
apparatus for the precision volume dispensing of blood serums has
been the prevention of contamination and uncontrolled dilution of
the serum. The present invention overcomes this problem.
The general purpose of this invention is to provide a precision
fluid metering device which embraces all the advantages of
similarity employed fluid aspirators and dispensers and possesses
none of the aforedescribed disadvantages. To obtain this, the
present invention contemplates a unique combination of a silicone
oil hydraulic fluid and an intersecting capillary conduit
arrangement in the fluid pick-up and dispensing needle whereby
inaccuracies of surface tension drops and fluid interface mixing
are avoided.
An object of the present invention is the provision of the
precision aspiration and dispersion of fluid free from inaccuracies
of surface tension drops.
Another object is to provide precision hydraulic aspiration and
dispersion of fluids wherein the hydraulic fluid does not mix or
contaminate the fluids aspirated and dispersed.
A further object of the invention is the provision of a dual
hydraulic fluid aspiration and dispersion system whereby a test
fluid may be aspirated and dispersed by one hydraulic fluid which
does not mix or contaminate the test fluid and whereby the test
fluid may be dispersed by the other hydraulic fluid to avoid
inaccuracies of surface tension drops of the test fluid.
Still another object is to provide a first precise interface
between fluid flowing in a first fluid path and fluid in a second
fluid path and a second precise interface between fluid flowing in
a second fluid path and fluid in the first fluid path.
Another object of the present invention is the provision of two
separate fluid paths having a common section with a first precise
interface between fluid traversing one fluid path and fluid in the
other fluid path and a second precise interface between fluid in
the one fluid path and fluid traversing the other fluid path.
Other objects and many of the intended advantages of this invention
will be readily appreciated as the same becomes better understood
by reference to the following detailed description when considered
in connection with the accompanying drawing in which like reference
numerals designate like parts throughout the figures thereof and
wherein:
FIG. 1 illustrates a partly mechanical and partly block diagram of
a preferred system embodiment of the invention;
FIG. 2 illustrates a cross-sectional view of the fluid pick-up and
dispensing needle probe of FIG. 1;
FIGS. 3(a), (b), (c), (d), and (e) illustrate various fluid
positions in the pick-up and dispensing probe encountered during
the operation of the fluid aspiration and dispersion system of FIG.
1; and
FIG. 4 illustrates a pictorial view of the pick-up probe embodiment
of the invention.
Referring now to the drawings, there is shown in FIG. 1 (which
illustrates a preferred embodiment) a probe having common capillary
conduit sections 7 and separate capillary conduit section 9 which
together form a first capillary conduit and a first fluid path. A
second capillary conduit 11 intersects the first capillary conduit
at a minute aperature therein to provide a second fluid path
through common section 7 and second capillary conduit 11. Fluid
conduit 13 connects separate section 9 of the first capillary
conduit to diluent syringe 15. Fluid conduit 17 connects second
capillary conduit 11 to silicone oil syringe 19. Diluent syringe 15
has fluid port or opening 21 in the side thereof connected to
diluent reservoir syringe 23. Piston 25 is located within diluent
syringe 15 and piston 27 is located within diluent reservoir
syringe 23. The interior volume of diluent reservoir syringe 23 is
designated as volume 28. Shaft 29 connects piston 25 to bracket 31
which in turn has a threaded opening therein into which screw 33 is
engaged to form a screw-drive mechanism. Screw 33 in turn is
connected to shaft 37 of digital stepping motor 30 by coupling 35.
Digital motor 39 is connected to electrical control 41 which in
turn is connected to program control 43. Electrical control 41 may
be a typical electrical circuit used to drive digital stepping
motors, which circuit is well known to those skilled in the
application and control of stepping motors. Electrical control 41
may also have an input circuit which can convert a digital input
code to a corresponding electrical signal to drive the stepping
motor through a predetermined angular excursion. Circuits of this
nature are well known and widely used to control the angular
position of a digital stepping motor. Program control 43 may be a
series of thumbwheel switches which may be rotated to produce a
desired digital code to the input circuit of electrical control
41.
Silicone oil syringe 19 has fluid port or opening 45 in the side
thereof connected to silicone oil reservoir syringe 47. Piston 49
is located within the interior volume of silicone oil syringe 19
and piston 51 is located within the interior volume 52 of silicone
oil reservoir syringe 47. Shaft 53 is connected to piston 49 and to
bracket 55, bracket 55 having a threaded opening therein which
engages screw 57 to form a screw-drive mechanism. Screw 57 is
connected to coupling 59 which in turn is connected to shaft 51 of
digital motor 63. Digital motor 63 is connected to electrical
control 65 which in turn is connected to program control 67.
Electrical control 65 may be identical to electrical control 41 and
program control 67 identical to program control 43.
Turning now to FIG. 2, there is illustrated a cross-sectional view
of a preferred embodiment of the pick-up and dispensing probe of
the invention. The first fluid capillary conduit path comprising
common section 7 and separate section 9 is a short length of a thin
walled capillary tubing having a minute aperture 8 located in the
side thereof between common section 7 and separate section 9. Block
12, having second capillary conduit 11 drilled therein by drilling
two intersecting right angle capillary lumens, is soldered to the
side of the first capillary conduit path tubing so that one end of
second capillary conduit path 11 intersects and mates with minute
aperture 8. Fluid conduit 13, which may be a flexible plastic or
teflon capillary lumen, is attached to the end of separate section
9 of the first fluid capillary conduit tubing. A short section of
capillary tubing 14 is soldered into the other end of second
capillary conduit path 11 in block 12. Fluid conduit 17, which may
be a flexible plastic or teflon capillary lumen similar to conduit
13 is fastened to capillary tubing 14.
FIGS. 3(a), (b), (c), (d), and (e) illustrate the fluid positions
within the pick-up and dispersing probe during the different
operating conditions of the probe. In FIG. 3(a), the probe is shown
in the fluid aspirating condition wherein fluid B, which may be a
silicone oil, fills common section 7 and second fluid conduit path
11; and fluid A, which may be a saline solution fills separate
section 9, forming an interface with fluid B at the end of separate
section 9 adjacent to minute aperture 8.
FIG. 3(b) illustrates the fluids within the probe just after a test
fluid C, which may be a blood serum, has been aspirated therein.
Fluid C fills common section 7 and second capillary conduit path 11
and continues on into fluid conduit 17 interfacing with fluid B
therein. Fluid A in separate section 9 interfaces with Fluid C at
the end of separate section 9 adjacent to minute aperture 8.
FIG. 3(c) illustrates the position of fluid within the probe after
test fluid C has been flushed from common section 7 by forcing
fluid A through common section 7 to the end thereof. Fluid A fills
both common section 7 and separate section 9 and forms an interface
with fluid C at minute aperture 8. Fluid C fills second capillary
conduit path 11 and continues upward into fluid conduit 17 where it
interfaces with fluid B. The amount of fluid C contained in second
capillary conduit path 11 and fluid conduit 17 depends upon the
amount of test fluid C aspirated therein.
FIG. 3(d) illustrates the fluid position within the probe when a
particular aliquot of test fluid C has been dispersed from conduit
17 and second conduit path 11 into common section 7. The volume
size of the aliquot can be extremely small and may occupy all or a
portion of common section 7, forcing fluid A therein out of the end
of common section 7. In this manner, precision aliquots of one
lambda or less may be obtained. The aliquot is dispersed from
common section 7 by forcing fluid A from separate section 9 through
common section 7 to the end thereof such that the fluids are in the
position illustrated in FIG. 3(c).
FIG. 3(e) illustrates the fluid positions within the probe when all
of the test fluid C has been dispersed from conduit 17 and second
conduit path 11 and the probe has been flushed out by dispersing
fluid A from separate section 9 through common section 7 and out of
the end thereof.
Turning now to FIG. 4, a pictorial view of a preferred embodiment
of the pick-up and dispersing probe is illustrated. The first
capillary conduit path tubing comprising common section 7 and
separate section 9 is shown soldered to block 12 containing second
capillary conduit path 11 (not shown) which is connected to short
section of capillary tubing 14.
Operation of the invention can best be described first by reference
to FIG. 1. Piston 25 of diluent syringe 15 is positioned to open
port 21 to allow fluid from diluent reservoir syringe 23 to be
forced from volume 21 by piston 27 into the interior of diluent
syringe 15. Piston 27 is moved into volume 28 until the diluent
fluid is expelled and dispersed out of common section 7 of the
pick-up and dispersing probe, thereby filling the interior volume
of diluent syringe 15, fluid conduit 13 and separate and common
sections 9 and 7 of the pick-up and dispersing probe. Piston 25 is
then moved to close port 21, placing the diluent syringe in
position for operation.
Similarly, piston 49 is moved to open port 45 in silicone oil
syringe 19 to permit fluid to be forced from volume 52 of silicone
oil reservoir syringe 47 by moving piston 51 into volume 52. Fluid
from reservoir syringe 47 is forced into the interior volume of
syringe 19, fluid conduit 17, second capillary conduit path 11 and
common section 7 of the pick-up and dispersing probe. Because of
the small capillary cross-sections of the first capillary conduit
tubing forming common section 7 and separate section 9, a very
small interface is formed between diluent fluid A (FIG. 3) and
silicone oil B (FIG. 3) thereby minimizing contamination and
mixing. Further, the chemical and physical properties of silicone
oil B further reduce the mixing with diluent A and provide a
substantially independent hydraulic fluid path within the
probe.
Piston 49 is then moved into the interior of silicone oil syringe
19 closing port 45 and further dispersing the contents of silicone
oil syringe 19 into fluid conduit 17 through the probe and out of
common section 7. This prepares silicone oil syringe 19 for the
aspiration of a test fluid into the probe with the fluids in the
position shown in FIG. 3(a).
Program control 67, which may contain finger operated digital
switches, programs electrical control 65 to produce a predetermined
driving signal to digital motor 63 causing shaft 61 to rotate
through a predetermined angle which in turn rotates screw 57 to
move bracket 55 and piston 49 in a direction to increase the
interior volume of silicone oil syringe 19 and aspirate test fluid
C into the probe as illustrated in FIG. 3(b). The use of silicone
oil provides a non-mixing interface between test fluid C and
silicone oil B. Furthermore, the small cross-sectional area of the
capillary tubing provides a precise interface between diluent fluid
A and test fluid C at the end of separate section 9 adjacent to
minute aperture 8. Since silicone oil syringe 19 may be a precision
bore calibrated syringe, program control 67 can be operated to
produce a precise volume change of silicone oil syringe 19 to
aspirate a precise volume of test fluid C into the probe and into
fluid conduit 17.
Before test fluid C is dispersed from the probe, fluid A may be
forced into common section 7 of the probe as illustrated in FIG.
3(c) to remove and flush test fluid C therefrom thereby removing
any surface tension drops at the end of the probe and enabling the
dispersing of precision aliquots of test fluid approaching one
lambda. This is done by moving piston 25 a fixed amount by
operation of program control 43 to program electrical control 41 to
produce a drive signal to digital motor 39 to turn shaft 37 through
a predetermined angle thereby turning screw 33 to move bracket 31
and piston 25 a given amount into the internal volume of diluent
syringe 15 equivalent to the volume of common section 7. The amount
of diluent fluid A used to perform this dispersion need be no more
than the volume of the capillary common section 7.
To disperse test fluid C, the thumb-wheel switches of program
control 67 may be operated to program electrical control 65 to
produce a drive signal to digital motor 63 to turn shaft 61 and
screw 57 through a predetermined angle to move bracket 55 and
piston 49 a precise amount corresponding to the precision volume of
test fluid to be dispersed. Turning to FIG. 3(d), dispersion of
test fluid C into common section 7 forces an equivalent amount of
diluent fluid A contained in common section 7 out of the probe in
front of the precision volume of test fluid C dispersed therein.
Therefore, a very small and precise aliquot of test fluid C is
forced in common section 7 which can be a fractional part of the
volume of common section 7. It should be clear that volumes of test
fluid C larger than common section 7 can be dispersed with equal
precision. To complete the test fluid dispersion operation, piston
25 of diluent syringe 15 may be further moved a predetermined fixed
amout to rinse the aliquot of test fluid C contained in common
section 7 from the probe again placing the fluids in the position
of FIG. 3(c). It should be noted that the amount of diluent in
every dispersing action added to the test aliquot is always
precisely the same and is equivalent to the volume of common
section 7. Therefore, comparative tests can be made on successive
test aliquots without inaccuracies caused by effects of varying
dilutions.
After the last of test fluid C has been dispersed into common
section 7, the section is flushed by forcing fluid A therethrough
whereby the fluids take the position illustrated in FIG. 3(e). Here
diluent fluid A now occupies separate section 9 and common section
7 and interfaces with silicone oil B at minute aperture 8. The
probe is then flushed with silicone oil from second conduit path 11
to take the fluid position illustrated in FIG. 3(a) where the probe
is ready once more for aspiration of test fluid C.
It should be clear at this point that the invention provides a
precision aspirating and dispersing probe that eliminates the
inaccuracies of aspiration and dispersion of fluids caused by the
formation of surface tension droplets at the end of the probe. This
makes it possible to obtain accuracies in fluid dispersion and
aspiration heretofore unobtainable. Furthermore, the use of
silicone oil as a non-mixing, non-contaminating hydraulic fluid to
interface with the test fluids which are being aspirated and
dispersed provides an unique advancement in achieving further
precision and accuracy heretofore unobtainable in systems using air
interface and other types of hydraulic fluids.
The present invention finds particular use in the field of blood
serum analysis where precision aliquots of one lambda or less are
desired and where dispersing into a multilicity of containers from
one sample container is required. Test fluids which are blood sera
may be precisely aspirated and dispersed to enable a larger number
of chemical tests from a given volume of serum than heretofore
possible. Since more chemical tests can be performed on a given
blood sample, the amount of blood taken from a patient for a given
set of tests is minimized. The smaller test volumes also enable
more rapid testing since less time is required for aspirating and
dispersing serum test aliquots.
It now should be apparent that the present invention provides a
probe arrangement and an inert hydraulic fluid which may be
employed in conjunction with a precision fluid metering system for
the precise and accurate aspiration and dispersion of blood sera
for chemical testing without the unwanted contamination and sample
volume errors associated with the sampling systems used heretofore
and with sample aliquots of smaller precision volumes than achieved
heretofore.
Although particular components, etc., have been discussed in
connection with a specific embodiment of a precision fluid metering
probe and control systems constructed in accordance with the
teachings of the present invention, others may be utilized.
Furthermore, it will be understood that although an exemplary
embodiment of the present invention has been disclosed and
discussed, other applications and circuit arrangements are possible
in that the embodiment disclosed may be subjected to various
changes, modifications and substitutions without necessarily
departing from the spirit of the inveniton.
* * * * *