Measuring and testing – Liquid level or depth gauge
Reexamination Certificate
2002-10-21
2003-07-29
Kwok, Helen (Department: 2856)
Measuring and testing
Liquid level or depth gauge
C073S864830, C073S864910, C340S621000, C422S106000, C220S495010
Reexamination Certificate
active
06598474
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to automatic sensing of liquid level in a sample container, and more particularly to a novel adapter for holding a sample container to facilitate liquid level sensing, and a novel method of sensing liquid level in a sample container.
Ultrasonic liquid level sensing is often used in automatic sample analysis systems of the type disclosed in U.S. Pat. Nos. 5,268,167 and 5,399,497. During automated sample analysis a liquid sample, such as blood serum, is subjected to a variety of tests. The serum sample, which is used as a source material for the tests, is usually placed in a relatively small container of fixed diameter, such as a Microtainer® tube, since the desired tests can be performed with relatively small amounts of diluted sample. For each discrete test on the serum a selected amount of diluted sample is aspirated from the sample container and combined with a predetermined amount of reagent to produce a chemical reaction that corresponds to a distinctive test on the sample.
The sample tests provide chemical information relating to different characteristics of the blood to assist in determining the health or well being of the individual being tested.
The quantity of sample which is used in each reagent test must be precisely controlled because test interpretation is based on an expectation that a predetermined amount of sample is combined with a predetermined amount of reagent. One known way of ensuring that the reagent tests are based on selected amounts of sample and reagent is to measure the sample level in a sample container before and after each aspiration of sample and to perform corresponding measurements on the reagent in a reagent container.
The liquid level measurement information will confirm that the intended amount of sample has in fact been used in a specific test. Thus consecutive measurements of sample level in a sample container provide confirmation that the required amount of liquid is removed from the sample container for each test. The sample level measurements for each test also provide an ongoing determination of the amount of liquid that remains in the sample container.
In known sample analysis systems of the type previously referred to it is common practice to transport one or more sample containers to different locations in the sample analysis system. Sample containers are usually transported in sample tube racks that carry larger diameter tubes than the Microtainer® tube, such as Vacutainer® tubes which have other uses in the sample analysis system. The sample tube rack preferably maintains tubes of all sizes in an upright position since the tubes are often in an open condition.
In order to simultaneously transport relatively small sample containers, such as Microtainer® tubes with other larger diameter tubes, each Microtainer® tube is usually supported in a larger diameter tube. However, because of a great disparity in size between the Microtainer® tube and the Vacutainer® tube it is necessary to cradle the Microtainer® tube in an intermediate holding device such as an Easi-nest® holder.
The Easi-nest® holder, which is open at one end and closed at the opposite end, has a tapered inside surface that is sized to bear against the Microtainer® tube when the Microtainer® tube is pushed into the Easi-nest® holder. The Easi-nest® holder also has a flange at the mouth portion that is large enough to rest on the mouth portion of the Vacutainer® tube. The support of a Microtainer® tube in an Easi-nest® holder held in a Vacutainer® tube is referred to herein as a sample tube support system or a Microtainer® tube support system.
The sensing of liquid level in the Microtainer® tube can be accomplished while the Microtainer® tube is supported in an Easi-nest® holder and elevated in a Vacutainer® tube held in a test tube rack or sample tube rack.
One known method of sensing liquid level is to employ an ultrasound detector. The ultrasound detector is located at a predetermined elevation over the travel path of the sample tube rack that holds the Microtainer® tube support system.
During liquid level sensing the ultrasound detector emits an ultrasonic wave directed against a horizontal surface of the Microtainer® tube support system that is proximate the liquid level. The ultrasonic wave is reflected as a sound echo from the horizontal surface back to the ultrasound detector. The characteristics of the echo are interpreted in a known manner by the ultrasound detector to indicate the distance between the ultrasound detector and the surface that reflected or produced the echo.
If the echo producing surface is in fact the liquid level in the Microtainer® tube than the distance between the liquid surface and the ultrasound detector can be determined by measuring the duration of time between the emission of the ultrasound wave and the receipt of the echo from the liquid level.
However, when a sample rack includes a Microtainer® tube supported in an Easi-nest® holder and a Vacutainer® tube it is difficult to selectively direct an ultrasonic wave against only the liquid level in the Microtainer® tube. To deal with this problem an ultrasonic wave is periodically emitted as the sample rack passes under the ultrasound detector. Ultrasonic waves are thus sequentially directed against other horizontal surfaces of the Microtainer® tube support system in addition to the liquid level. These horizontal surfaces include the mouth portion of the Microtainer® tube and the mouth portion of the Easi-nest® holder.
Based on a known height of the mouth portion of the Microtainer® tube from a reference level we can determine a first distance between the ultrasound detector and the mouth portion of the Microtainer® tube. Also based on a known height of the mouth portion of the Easi-nest® holder from the reference level we can determine a second distance between the ultrasound detector and the mouth portion of the Easi-nest® holder. Thus the mouth portion surfaces of the Microtainer® tube and the Easi-nest® holder can be identified from their corresponding echoes. The remaining echo would thus be associated with the liquid level in the Microtainer® tube.
Generally the liquid level
110
in a Microtainer® tube
20
is initially at a higher level than the mouth portion
140
of the Easi-nest® holder
132
(see FIGS.
10
and
11
). However, as liquid
80
is depleted from the Microtainer® tube
20
the liquid level
110
recedes toward the mouth level
140
of the Easi-nest® holder
132
. When liquid level
110
in the Microtainer® tube
20
closely approaches the level of the mouth portion
140
of the Easi-nest® holder
132
it becomes difficult to distinguish between the echo from the liquid level
110
in the Microtainer® tube
20
and the echo from the mouth portion
140
of the Easi-nest® holder
132
. Thus there is a range of liquid level
110
in the Microtainer® tube
20
that can be confused with the level of the mouth portion
140
of the Easi-nest® holder
132
which can lead to errors in liquid level sensing.
It is thus desirable to provide a sample tube support structure for a sample container such as a Microtainer® tube that facilitates distinguishing a liquid level surface echo from an echo produced by a structural surface of the Microtainer® tube support system.
Another problem in measuring liquid level in a Microtainer® tube supported in an Easi-nest® holder is that the amount by which a Microtainer® tube projects from an Easi-nest® holder may vary due to manufacturing tolerances. Inconsistent positioning of the Microtainer® tube in the Easi-nest® holder is also common because the Microtainer® tube is usually manually pushed into snug engagement with the tapered surface of the Easi-nest® holder and there is no fixed stop position for the Microtainer® tube in the Easi-nest® holder. It is thus desirable to provide a Microtainer® tube support system wherein the Microtainer® tube is always located in the same position in the support system.
OBJECTS AND SUMMARY OF THE INVENTION
Among the several objects of the invention may be n
De Young Thomas W.
Purpura Paul E.
Bayer Corporation
Klawitter Andrew L
Kwok Helen
Paolino John M.
Rodman & Rodman
LandOfFree
Adapter for holding a sample container to facilitate sensing... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Adapter for holding a sample container to facilitate sensing..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Adapter for holding a sample container to facilitate sensing... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3021908