U.S. patent application number 09/845304 was filed with the patent office on 2001-10-11 for tube bottom sensing for small fluid samples.
Invention is credited to Babson, Arthur L., Tyberg, William.
Application Number | 20010028864 09/845304 |
Document ID | / |
Family ID | 23619825 |
Filed Date | 2001-10-11 |
United States Patent
Application |
20010028864 |
Kind Code |
A1 |
Tyberg, William ; et
al. |
October 11, 2001 |
Tube bottom sensing for small fluid samples
Abstract
A pipetting station having a bottom sensing device is provided
in conjunction with one of any known liquid level sensing devices.
The bottom sensing device includes a pipetting probe spring mounted
to a pipetting arm of the pipetting station. The bottom sensing
device also includes a sensor for determining when a pipetting tip
of the pipetting probe is in contact with a bottom of a tube. The
bottom sensing device permits the pipetting probe to measure an
exact volume of fluid in the tube by allowing the pipetting tip to
be lowered to the bottom of the tube beyond the sensed fluid
level.
Inventors: |
Tyberg, William; (Spring
Valley, NY) ; Babson, Arthur L.; (Chester,
NJ) |
Correspondence
Address: |
Whitham, Curtis & Whitham
Reston International Center
Suite 900
11800 Sunrise Valley Dr.
Reston
VA
20191
US
|
Family ID: |
23619825 |
Appl. No.: |
09/845304 |
Filed: |
May 1, 2001 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
09845304 |
May 1, 2001 |
|
|
|
09409282 |
Sep 30, 1999 |
|
|
|
6270726 |
|
|
|
|
Current U.S.
Class: |
422/509 ;
422/180; 422/67; 73/149; 73/864.24 |
Current CPC
Class: |
Y10T 436/2575 20150115;
Y10T 436/115831 20150115; Y10T 436/12 20150115; Y10T 436/119163
20150115; G01N 35/1011 20130101 |
Class at
Publication: |
422/100 ; 422/67;
73/864.24; 73/149; 422/180 |
International
Class: |
G01N 021/00; B01L
003/02; G01N 035/10 |
Claims
Having thus described our invention, what we claim as new and
desire to secure by Letters Patent is as follows:
1. A bottom sensing device for determining a bottom of a container,
comprising: mounting means for mounting a pipetting probe on a
pipetting arm, the mounting means allowing the pipetting arm to
move an incremental distance independent of the pipetting probe
when the pipetting tip contacts a bottom of the container; and
sensing means for sensing when the pipetting tip is in contact with
the bottom of the container, the sensing means being activated when
the pipetting arm moves the incremental distance.
2. The bottom sensing device of claim 1, wherein the container is
one of a test tube and a reagent container.
3. The bottom sensing device of claim 1, further comprising
calculating means for calculating a volume of the fluid in the
container, the volume being calculated based on (i) a known shape
of a type of container used to hold a sample fluid, (ii) a top
level of the sample fluid in the container as sensed by a sensing
means, and (iii) a distance of movement of the pipetting arm from
the top level of the sample fluid to when the pipetting tip is in
contact with the bottom of the container.
4. The bottom sensing device of claim 3, wherein the calculating
means further calculates a distance from the top level of the fluid
to the bottom of the container by subtracting the incremental
distance of the pipetting arm from an entire distance of movement
of the pipetting arm.
5. The bottom sensing device of claim 1, wherein the mounting means
is a spring mechanism.
6. The bottom sensing device of claim 5, wherein the spring
mechanism is provided about a tip of the pipetting probe proximate
to the pipetting arm.
7. The bottom sensing device of claim 6, wherein the spring
mechanism permits the pipetting arm to move independent of the
pipetting probe.
8. A method of determining a bottom of a container, comprising:
lowering a pipetting arm having a pipetting tip to the bottom of
the container; incrementally lowering the pipetting arm while the
pipetting tip remains in contact with the bottom of the container;
triggering a sensor when the pipetting arm has been incrementally
lowered a certain distance.
9. The method of claim 8, further comprising stopping the
incrementally lowering of the pipetting arm when the when the
sensor is triggered.
10. The method of claim 8, further comprising incrementally raising
the pipetting arm when the sensor is triggered in order to
eliminate obstructions of the pipetting tip when aspirating the
fluid.
11. The method of claim 8, further comprising determining a top
level of a fluid in relation to a home position prior to the
pipetting tip contacting the bottom of the container.
12. The method of claim 11, further comprising determining a volume
of the fluid in the container, the volume being based on (i) a
known shape of a type of container used to hold a sample fluid,
(ii) the top level of the fluid and (iii) a distance from the top
level of the fluid to the bottom of the container.
13. A method of determining a volume of fluid in a container using
a pipetting station, the pipetting station including a pipetting
arm having a downward extending pipetting probe, a distal end of
the pipetting probe having a pipetting tip, the method comprising:
lowering the pipetting arm such that the pipetting tip contacts the
fluid in the container; sensing a top level of the fluid in the
container with the pipetting tip; incrementally lowering the
pipetting arm until the pipetting tip contacts a bottom of the
container; and determining the volume of the fluid in the is
container based on a distance of movement of the pipetting arm from
the top level of the fluid to when the pipetting probe is in
contact with the bottom of the container and a known volume based
on a type of container used to hold a sample fluid.
14. The method of claim 13, further comprising determining the top
level of the fluid in the container in relation to a known home
position of the pipetting arm.
15. The method of claim 13, wherein the measuring of the top level
of the fluid is performed below a near bottom container level
position.
16. The method of claim 15, wherein the near bottom container level
position is a fixed volume known to suffice any test of the
fluid.
17. The method of claim 13, further comprising determining whether
the pipetting tip contacts the bottom of the container prior to the
sensing of the fluid.
18. The method of claim 13, further comprising acquiring and
storing a position reading of the pipetting arm with relation to a
home position when the top level of the fluid is sensed.
19. The method of claim 13, further comprising continuing to lower
the pipetting arm a certain distance after the pipetting tip is in
contact with the bottom of the container, wherein the pipetting tip
remains stationary when the pipetting arm is lowered the certain
distance.
20. The method of claim 19, further comprising triggering a sensor
when the pipetting arm has traveled the certain distance.
21. The method of claim 20, further comprising stopping the
lowering of the pipetting arm when the sensor is triggered.
22. The method of claim 19, wherein the distance of movement of the
pipetting arm to reach the bottom of the container is determined by
subtracting the certain distance from an entire lowered distance of
the pipetting arm from the sensed top level of the fluid.
23. The method of claim 22, wherein the volume of the fluid in the
container is further determined by a known volume based on a type
of container used to hold a sample fluid.
24. The method of claim 13, further comprising determining a type
of container being used to hold the fluid, the determining being
based on one of at least (i) a distance the pipetting arm is
lowered prior to the pipetting tip contacting the bottom of the
container and (ii) a reading of a code placed on a rack or insert
holding the container.
25. The method of claim 24, further comprising calibrating a near
bottom container level based on the determined type of the
container.
26. The method of claim 13, further comprising determining whether
a sufficient volume of the fluid is present in the container to
perform a test based on the determined volume of fluid in the
container and a look up table including an amount of fluid needed
to perform the test.
27. The method of claim 13, further comprising prioritizing which
tests may be performed with the volume of the fluid in the
container.
28. The method of claim 13, further comprising alerting an operator
when there is not a sufficient amount of volume of fluid to perform
a test or tests based on the determined volume.
Description
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
[0001] The present invention generally relates to a method and
apparatus for sensing small fluid samples in a vessel and, more
particularly, to a method and apparatus for determining the volume
of a fluid in a vessel, such as a test tube, using a bottom sensing
device (e.g., tip jam device).
BACKGROUND DESCRIPTION
[0002] Analyses of fluids, especially bodily fluids such as urine
and blood, are important to the diagnoses and treatment of various
illness and other conditions. These illnesses and conditions can
range from various forms of cancers to blood diseases to drug use
and others.
[0003] In order to analyze a bodily fluid, a sample of fluid is
first taken from a person and analyzed either by hand or by an
automatic analyzer or other device of the type well known in the
art. In the case of an automatic analyzer, for example, the bodily
fluid is disposed in a tube which, in turn, is disposed on a
carousel or other conveying mechanism. The carousel or other
conveying mechanism conveys the tube though scanning stations, for
example, and under a pipetting station in order for a pipetting
probe to aspirate a sample of the fluid.
[0004] The pipetting probe is then lowered into the tube in order
to aspirate a sample of the fluid. Thereafter, and depending on the
specific test or tests to be performed on the fluid, a specific
reagent may be combined with the fluid in order for a chemical
reaction to occur. This chemical reaction is then analyzed to
determine, for example, the amount of analyte in a sample of
fluid.
[0005] It is not uncommon for many different tests to be performed
on the sample fluid using different reagents. However, in order for
the appropriate tests to be performed on the sample fluid a
sufficient amount of the sample fluid must be present in the tube.
Accordingly, when using automatic analyzers, the sample level in
the tube is normally determined by the pipette probe which is
connected to a sample sensing means such as a capacitive or
conductive circuit. The sensing means is triggered upon contact of
the pipette tip with the surface of the sample. The pipette probe
is then further lowered a distance into the sample sufficient to
allow withdrawal of the required volume. However, to ensure that an
insufficient volume of sample will not be drawn, owing to the
sample level being too close to the bottom of the tube, the pipette
tip will only be allowed to be lowered to a certain level within
the tube resulting in a volume of sample, called the dead volume,
that is unavailable for testing. The maximal distance the pipette
tip is allowed to be lowered, and thus the nominal dead volume, is
set by the manufacturer of the automatic analyzer. It is noted that
the actual dead volume is variable and is dependent on several
dimensional tolerances that exist within and between different
instruments. A more dimensionally precise automatic analyzer would
allow the pipette tip to aspirate fluids at a lower level than
other less precise automatic analyzers, and thereby allow the
manufacturer to set a smaller sample dead volume. Any amount of
sample fluid below the preset dead volume level can not be utilized
to perform a test or tests thereon despite the fact that the fluid
in the test tube below the dead volume level may still be
sufficient to perform a test or tests thereon.
[0006] Thus, what is needed is a system that determines the exact
volume of a fluid below a threshold level which may be defined as a
near bottom tube level. It is noted that the near bottom tube level
is an arbitrary level of fluid in the tube, and may be predefined
by the manufacturer of an automatic analyzer. The determination of
the exact volume of a fluid in the tube will allow the automatic
analyzer or other device to determine whether there is a sufficient
amount of fluid in the tube in order to perform a certain
predetermined test or tests.
SUMMARY OF THE INVENTION
[0007] It is therefore an object of the present invention to
provide a system and method for determining a bottom of a tube or
other container.
[0008] It is a further object of the present invention to provide a
system and method for determining the volume of a fluid in a tube
or other container.
[0009] It is also an object of the present invention to provide a
system and method of measuring a reagent in a reagent
container.
[0010] It is still another object of the present invention to
provide a system and method for determining whether a sufficient
amount of fluid is present in a tube for a specific test or
tests.
[0011] In order to accomplish the objects of the present invention,
a pipetting station having a bottom sensing device is provided in
conjunction with one of any known liquid level sensing devices. The
bottom sensing device includes a pipetting probe spring mounted to
a pipetting arm of the pipetting station. The bottom sensing device
also includes a sensor for determining when a pipetting tip of the
pipetting probe is in contact with a bottom of a tube.
[0012] The bottom sensing device of the present invention permits
the pipetting probe to measure the volume of fluid in the tube by
allowing the pipetting tip to be lowered to the bottom of the tube
beyond the sensed fluid level (and the near bottom tube level). In
the embodiments of the present invention, the pipetting arm is
further lowered until the pipetting probe triggers a sensor which
stops the downward movement of the pipetting arm. The exact
distance between actual tip jam and triggering of the tip jam
sensor, and therefore the actual bottom of the tube, is known and
configured for each instrument.
[0013] A determination is then made as to (i) an exact volume of
fluid and (ii) whether there is sufficient sample fluid in the tube
to perform a test or tests thereon. The determination of the volume
of fluid in the tube is based on (i) the sensed level of the fluid
as determined by the level sensor (in relation to a "home" position
of the pipetting arm), (ii) the distance the pipetting arm traveled
from the level of the sample fluid to the time when the pipette tip
contacts the bottom of the tube and (iii) the type of tube used for
holding the fluid. If sufficient fluid is present, then the
pipetting tip is raised slightly above the known tube bottom level
in order to aspirate sample fluid or reagent therefrom.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The foregoing and other objects, aspects and advantages will
be better understood from the following detailed description of a
preferred embodiment of the invention with reference to the
drawings, in which:
[0015] FIG. 1 is generalized block diagram of an instrument used
with the present invention;
[0016] FIG. 2 is a partial view of an automated analyzer used with
the present invention;
[0017] FIG. 3a is a pipetting station in a raised position using a
bottom sensing device of the present invention;
[0018] FIG. 3b is a pipetting station in a lowered position using a
bottom sensing device of the present invention;
[0019] FIG. 3c is a pipetting station in a lowered position with
the bottom sensing device of the present invention being
activated;
[0020] FIG. 4 is a comparison of a standard tube and a conical
bottom tube located in a tube holding device;
[0021] FIG. 5 is a flow chart of the processing steps of the
present invention; and
[0022] FIG. 6 is an alternate flow chart of the processing steps of
the present invention.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION
[0023] The present invention is directed to a method and apparatus
for sensing fluids of small samples in a tube and, more
specifically, to a method and apparatus for determining the volume
of a fluid in a tube that is below a near bottom tube level using a
bottom sensing device. The bottom sensing device is used to
determine the volume of a fluid in a tube, as described in detail
below. By using the apparatus and method of the present invention,
a pipetting station of an automatic analyzer or other device may
aspirate fluids of small samples for testing thereon.
[0024] In order to accomplish the objectives of the present
invention, a bottom sensing device is implemented in conjunction
with a pipetting tip having a capacitive level sensor or other
means of sensing fluid levels. A pipetting capacitive level sensor
contemplated for use with the present invention is disclosed in
U.S. Pat. No. 5,648,727 and is incorporated herein by reference in
its entirety. In general, the capacitive level sensor disclosed in
U.S. Pat. No. 5,648,727 includes a pipetting probe having an
elongated shaft having a conductive tip, and an integrated circuit
chip containing a capacitive sensing circuitry. When the conductive
tip is lowered and contacts a sample fluid, an increase in
capacitance is sensed. This sensed increase in capacitance is used
to determine the level of the sample fluid in relation to a "home"
position of the pipetting arm. It is well understood that other
level sensors may also be used with the present invention, such as,
for example, electrically conductive sensors or air pressure
sensors.
[0025] The bottom sensing device includes a spring loaded pipetting
arm having a sensor which senses when the pipetting tip is in
contact with the bottom of the tube. It is noted that the automatic
analyzer or other device does not identify that the pipetting tip
is in contact with the bottom of the tube until after the sensor is
triggered. Accordingly, the automatic analyzer or other device
identifies the bottom of the tube when the spring loaded pipetting
arm travels until the sensor is "flagged" (e.g., triggered). The
distance between the actual tube bottom and the triggering of the
sensor is a known configured number of steps on a stepper motor. In
a preferred embodiment, the triggering of the sensor will stop the
downward movement of the pipetting arm.
[0026] In the preferred embodiments, once the pipetting arm is
raised or during raising thereof, a determination may be made as to
(i) the volume of fluid and (ii) whether there is sufficient sample
fluid in the tube to perform a test or tests thereon. The
determination of the volume of fluid in the tube is based on, in
part, (i) the distance the pipetting arm traveled from the level of
the sample fluid to the time when the sensor was triggered minus
the certain distance traveled after the pipetting tip is in contact
with the bottom of the tube and (ii) the known shape of the type of
tube used to hold a sample fluid. FIGS. 3a-3c show a detailed view
of the pipetting station using the bottom sensing device of the
present invention, and FIGS. 5 and 6 show a detailed flow diagram
explaining a process used with the bottom sensing device of the
present invention.
[0027] In order to practice the present invention, an automatic
analyzer or other known device is needed to perform the specific
tests on the fluid samples. In general, FIG. 1 shows a block
diagram of an automatic analyzer which may be used with the present
invention. The automatic analyzer 10 is connected to a computer 12
via data communication lines 14 which are used to supply
information from the automatic analyzer 10 to the computer 12. This
information may be, for example, bar coded information placed on
the sample fluid tubes. The automatic analyzer 10 is preferably
operated under the direction of on-board microprocessors (not
shown). It is well understood that the block diagram of FIG. 1 is
not critical to the understanding of the present invention and that
other devices depicted in other block diagrams may equally be used
with the present invention, including non-medical devices.
[0028] FIG. 2 shows a partial view of the automatic analyzer 10 in
greater detail. It is noted that the automatic analyzer 10 of FIG.
2 is an IMMULITE 2000.TM. manufactured by DPC.RTM. Cirrus (a
subsidiary of Diagnostic Products Corporation) of Randolph, N.J.;
however, it is noted that the automatic analyzer of FIG. 2 is
merely representative of one automatic analyzer used with the
present invention and it is well understood that the present
invention may easily be implemented with other automatic analyzers
or other fluid sample devices known to one of ordinary skill in the
art. It is further important to note that the automatic analyzer of
FIG. 2 is merely described herein for illustrative purposes and to
better understand the present invention, and that only the bottom
sensing device of the pipetting station and the method of use
discussed herein (with reference to FIGS. 3a-6) are part of the
present invention.
[0029] Referring more specifically now to FIG. 2, a sample carrier
tube 20 is transported by a carousel 22 towards a reagent pipetting
station 24 and sample pipetting station 24A. Prior to being
transported to the pipetting stations 24 or 24A, the sample carrier
tube 20 may be transported through a bar code reader 26. In the
embodiments of the present invention, the bar code reader 26 may
identify the person (of which the sample fluid belongs to) or type
of tube being used such as, for example, a pediatrics or micro
sample tube. In the case of a pediatrics or micro sample tube, the
computer of FIG. 1 will include an alternative look-up table in
order to calculate the volume of the fluid in the sample, as
discussed below.
[0030] It is noted that the information from the bar code reader 26
is sent to the memory of the computer 12, which may also track the
position of the sample carrier tube 20 on the carousel 22. It is
further noted that the computer may be preprogrammed to include the
volume table of known volumes of tubes (such as conical bottom
tubes and micro sample tubes) as well as the volume of fluid needed
to perform a certain test or tests on the fluid. The computer may
also be programmed to prioritize which tests may be performed with
the amount of fluid present in the tube. For example, if three
tests must be performed on the fluid, the system and method of the
present invention may prioritize that the first and third test be
performed to the exclusion of the second test since only enough
sample fluid is present in the tube to perform the first and third
test. Of course other variations may also be provided for by the
present invention.
[0031] As seen further in FIG. 2, the reagent pipetting station 24
and sample pipetting station 24A include a reagent pipetting arm 32
and a sample pipetting arm 32A, respectively, which both may travel
a circular path. (Hereinafter, the reagent pipetting station 24 and
sample pipetting station 24A are referred to as the pipetting
station 24 and the reagent pipetting arm 32 and sample pipetting
arm 32A are referred to as the pipetting arm 32.) In this path, the
pipetting arm 32 may extend to the sample carrier tube 20 in the
carousel 22, a reagent 28 in the reagent carousel 40, and a probe
wash station 30. The pipetting arm 32 may also travel in other
paths, and may equally extend to other carriers or stations, such
as for example, a sample dilution well 31. A downward projecting
pipetting tip (shown in FIGS. 3a-3c) is positioned at the free end
of the pipetting arm 32. To perform pipetting operations, the
pipetting tip is inserted into and out of the sample carrier tubes
20 and other stations along its Z-axis (perpendicular to the plane
of the paper).
[0032] Referring now to FIG. 3a, a detailed view of the pipetting
station in a "home" position is shown. The pipetting station 24
includes the pipetting arm 32 that moves in the direction of arrow
42, and a pipetting probe 34 spring mounted to the pipetting arm 32
of the pipetting station 24. The pipetting probe 34 includes a
pipetting tip 36 having a capacitive level sensor as described with
reference to U.S. Pat. No. 5,648,727. The capacitive sensor senses
a level of the fluid and determines that level in relation to a
known "home" position. The tube 20 is placed in a holding device
(see FIG. 4) so that a bottom of the tube 20 is at the reference
line "X" which is used as a reference point for discussion purposes
only.
[0033] The bottom sensing device of the present invention includes
a spring mechanism 38 and a sensor 40 mounted between the pipetting
probe 34 and the pipetting arm 32. Specifically, the spring
mechanism 38 is mounted to the pipetting probe 34 in the pipetting
arm 32 and permits the pipetting arm 32 to work independently of
the pipetting probe 34 as seen more clearly with reference to FIG.
3b and FIG. 3c. In general, the pipetting arm 32 lowers the
pipetting probe 34 until the pipetting tip 36 is in contact with
the bottom of the tube 20 (past a near bottom tube level) (FIG.
3b). The pipetting arm 32 is then further capable of being lowered
an incremental distance while the pipetting probe 34 remains
stationary and the pipetting tip 36 is in contact with the bottom
of the tube 20 (FIG. 3c).
[0034] The sensor 40, preferably positioned proximate the pipetting
arm 32, determines when the pipetting arm 32 has traveled the
incremental distance, such as, for example, approximately in the
range of 1 mm to 4 mm or more, while the pipetting probe 34 remains
stationary (represented as "Z" distance in FIGS. 3b and 3c). It is
noted that the bottom sensing device of the present invention
determines that the pipetting tip 36 is in contact with the bottom
of the tube 20 when the sensor 40 is triggered, at which time the
downward movement of the pipetting arm 32 is stopped, and in
embodiments the pipetting tip 36 may be raised an incremental
amount within the fluid so that pipetting tip 36 will not become
occluded when aspiration of the fluid begins.
[0035] FIG. 3b shows the pipetting probe 34 in a lowered position
and the pipetting tip 36 in contact with the bottom of the tube 20.
As seen with reference to the line "X", the tube 20 remains
stationary throughout the process while the pipetting arm 32 and
pipetting probe 34 are lowered. It is readily apparent that the
pipetting arm 32 and the pipetting probe 34 are synchronously
lowered until the pipetting tip 36 is in contact with the bottom of
the tube 20.
[0036] FIG. 3c shows the pipetting arm 32 being lowered an
incremental distance "Z" while the pipetting probe 34 is stationary
and the pipetting tip 36 is in contact with the bottom of the tube.
At this stage the sensor 40 is activated after the pipetting arm
has been lowered the incremental distance "Z". The independent
movement of the pipetting arm 32 with relation to the pipetting
probe 34 is due to the spring loaded mechanism 38 described with
reference to FIG. 3a. It is noted that the incremental distance
between the actual bottom of the tube and the triggering of the
sensor of the pipetting arm 32 is configured for each individual
pipetting station 24 such that the traveled distance may vary
between different pipetting stations.
[0037] Thus, by using the bottom sensing device of the present
invention, the pipetting tip 36 can be lowered past the level of
the fluid and the volume measurement of the fluid in the tube 20
can be determined. This is provided by the use of the spring loaded
mechanism 38 in conjunction with the independent movement of the
pipetting arm 32 and the activation of the sensor 40 as discussed
with reference to FIGS. 3a-3c. Once the volume of fluid is known,
the system of the present invention can determine whether a
sufficient amount of fluid remains in the tube 20 in order to
perform a certain predefined test. The volume of the sample fluid
in the tube 20 is calculated by (i) a known volume based on a type
of tube used to hold a sample fluid, (ii) a top level of the sample
fluid in the tube as sensed by the level sensor, and (iii) a
distance of movement of the pipetting arm minus the certain
distance the pipetting arm traveled after the pipetting tip is in
contact with the bottom of the tube. Alternatively, the present
invention can prioritize between which tests are to be performed on
the fluid, as discussed above.
[0038] FIG. 4 shows a comparison between a standard tube (having a
rounded bottom) and a conical bottom tube in a tube holding device.
Specifically, the standard tube is held in the tube holding device
42 by use of a resilient spring 44 biasing the standard tube
against a wall 47 of an opining 45. At a bottom of the tube holding
device 42 is an opening 46. The opening 46 is configured such that
the bottom of the standard test tube remains at the reference line
"X" as discussed with reference to FIGS. 3a-3c. However, the
opening 46 allows the bottom of the conical shape tube to exceed
beyond the reference line "X" to reference line "Y". In the
preferred embodiment, the distance between the reference line "X"
and the reference line "Y" is about 0.10 inches; however, it is
well understood that any other distance may also be contemplated
for use with the present invention. As discussed in more detail
with reference to FIGS. 5 and 6, the pipetting tip may be lowered
past the reference line "X" (step S58a) to reference line "Y" such
that the system of the present invention will automatically
identify that a conical shaped bottom tube is being used with the
present invention. In this case, when the system of the present
invention automatically identifies that such a conical shaped
bottom tube is being used, the sample volume of the tube will be
calculated by reference to an alterative look-up table which is
different from the look-up table for the standard tube.
[0039] Prior to discussing FIGS. 5 and 6, it is noted that the
calculation of the volume of the fluid in the tube is calculated by
the CPU of the computer or other similar device. It is also readily
understood by one of ordinary skill in the art that all other
calculations and determinations discussed herein are also
calculated by the CPU of the computer or other similar device.
These calculations and determinations may further include the
prioritization of the tests being performed on the fluid as well as
the near tube bottom position (e.g., the position of prior art
systems in which one was assured that there was enough fluid to run
a specific test or tests).
[0040] More specifically, the invention can be implemented using a
plurality of separate dedicated or programmable integrated or other
electronic circuits or devices (e.g., hardwired electronic or logic
circuits such as discrete element circuits, or programmable logic
devices such as PLDs, PLAs, PALs, or the like). A suitably
programmed general purpose computer, e.g., a microprocessor,
microcontroller or other processor device (CPU or MPU), either
alone or in conjunction with one or more peripheral (e.g.,
integrated circuit) data and signal processing devices can be used
to implement the invention. In general, any device or assembly of
devices on which a finite state machine capable of implementing the
flow charts shown in FIGS. 5 and 6 can be used as a controller with
the invention.
[0041] FIG. 5 is a flow diagram showing the process of using the
bottom sensing device of the present invention. Specifically, at
step S40, a "home position" is determined and stored in the memory
of the computer. At step S42, the pipetting arm is lowered and, at
step S44, a determination is made as to whether any fluid is sensed
at or above a near tube bottom level position, typically 250 .mu.l
or other determined level. If fluid is sensed at the near bottom
tube level position, at step S46, a sample of the fluid is
aspirated into the pipetting probe and a test is performed thereon.
However, if no fluid is sensed at the near bottom tube level
position, at step 48, the pipetting arm is lowered until a fluid
level is sensed. At this step, it is preferred that the lowering of
the pipetting arm be slower than the previous movement of the
pipetting arm to ensure that the pipetting tip does not contact the
bottom of the tube at such a rate of speed as to damage or destroy
the tube or pipetting tip or arm.
[0042] At step S50, a determination is made as to whether the
pipetting tip is in contact with the bottom (discussed in detail
below) of the tube fluid prior to sensing any fluid within the
tube. If no fluid is sensed, a determination is made that there is
no fluid in the tube and the process of the present invention
stops, at step S52. However, if a fluid is sensed, at step S54, a
position reading of the pipetting arm (or probe or tip) with
relation to a "home" position is determined and stored in the
memory of the computer. The position reading is determinative of
the level of sensed fluid.
[0043] At step S56, the pipetting tip is lowered until it is in
contact with the bottom of the tube. As discussed above, the
pipetting station does not know that the pipetting tip is in
contact with the bottom of the tube at this step. Thus, in order to
determine that the pipetting tip is in contact with the tube, at
step S58, the pipetting arm is lowered an incremental distance
while the pipetting probe remains stationary until the sensor is
triggered. Once the sensor is triggered at step S58, the downward
movement of the pipetting arm is stopped. At step S60, the
pipetting arm and pipetting probe may be raised an incremental
amount within the fluid, preferably just above the known tube
bottom level, so that the pipetting tip 36 will not become occluded
when the fluid is aspirated by the pipetting probe. It is at this
step S58, that the pipetting station knows that the pipetting tip
is in contact with the bottom of the tube and may thus determine
the volume of fluid present in the tube.
[0044] In an alternate embodiment, the pipetting tip may be lowered
past the reference line "X" (step S58a) by a certain distance such
that the system of the present invention will identify that a
conical shaped bottom tube is being used with the present
invention. This is based on the fact that the conical shaped tube,
in the embodiments of the present invention, preferably extend past
the reference line "X" so that when the pipetting tip passes the
reference line "X" the system of the present invention will
automatically identify that such a conical shaped bottom tube is
being used herein. In this case, the sample volume will be
calculated by reference to an alterative look-up table which is
different from the look-up table for a standard tube.
[0045] At step S62, the volume of fluid in the tube is determined
(as described above with reference to FIG. 3a). That is, the volume
of the tube is calculated by using a look-up table for the tube and
by(i) a known shape of the type of tube used to hold a sample
fluid, (ii) a top level of the sample fluid in the tube as sensed
by the liquid level sensor, and (iii) a distance of movement of the
pipetting arm minus the certain distance the pipetting arm traveled
after the pipetting tip is in contact with the bottom of the
tube.
[0046] At step S66, a determination is made as to whether there is
sufficient amount of fluid in the tube to perform desired specific
tests. If there is not a sufficient amount of fluid, then the
process of the present ends at step S68. However, if there is
enough fluid present in the tube, then at step S70, the present
system may prioritize which tests may be performed on the fluid
sample and being aspiration of the fluid for testing thereon.
Alternatively, the operator can be alerted that insufficient sample
is available to complete all of the required tests, and the
operator can then select manually which test or tests may be
performed on the sample fluid.
[0047] As discussed above, a known volume table for tubes is
provided to the system of the present invention. This allows the
present invention to "look up" an appropriate table in order to
calculate the volume of the tube based on the movement of the
pipetting arm with relation to a sensed level of the fluid and a
determined bottom position of the tube. It is also readily
understood by one of ordinary skill in the art that the system of
the present invention also stores in memory or the like the amount
of fluid needed for the specific test or tests.
[0048] FIG. 6 is a flow diagram showing an alternative process of
using the bottom sensing device of the present invention. In this
embodiment, the sample tube is a conical or a round bottom micro
tube which is contained in a special bar coded insert or rack. In
the case of the micro tube (and in embodiments the conical bottom
tube), an identification is provided by a second interrogation of
the sample carousel or conveyer by the bar code reading station.
The preconfigured new tube bottom position based on the detected
tubes would be different from each of these tubes as well as being
different from the standard tube. It is further noted that each
tube has its own look-up table such that the sample volume of each
different tube may be calculated by reference to a specific look-up
table.
[0049] More specifically, after step S40, the tube is passed by a
bar code scanner for reading of a bar code (step S41a). This step
may also be performed prior to step S40. The bar code reader
provides the bar code information to the computer such as, but not
limited to, (i) the type of tube being used to hold the fluid and
(iii) the identifying information of the fluid (e.g., person). In
this embodiment of the present invention, the system of the present
invention may also consult a look up table to determine the amount
of fluid needed for a specific test or tests to be performed on the
fluid. The remaining steps of FIG. 5 may then be implemented.
[0050] It is noted that when using the conical bottom tube, the
system of the present invention will automatically identify such a
conical bottom tube when the pipetting tip exceeds the reference
line "X" at step S56.
[0051] While the invention has been described in terms of a single
preferred embodiment, those skilled in the art will recognize that
the invention can be practiced with modification within the spirit
and scope of the appended claims.
* * * * *