Chemical apparatus and process disinfecting – deodorizing – preser – Control element responsive to a sensed operating condition
Reexamination Certificate
1999-09-08
2001-11-27
Warden, Jill (Department: 1743)
Chemical apparatus and process disinfecting, deodorizing, preser
Control element responsive to a sensed operating condition
C422S105000, C422S106000, C422S105000
Reexamination Certificate
active
06322752
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to improvements in methods and apparatus for aspirating a volume of liquid (e.g., whole blood) from a container (e.g., a test tube or vial) and for dispensing a precise aliquot of such volume to a work station for processing or analysis. The invention is particularly useful in the fields of hematology, flow cytometry and blood chemistry in which it is often necessary to aspirate and dispense, with high precision, relatively tiny volumes (e.g., 10-100 microliters) of blood for analysis.
2. Discussion of the Prior Art
Automated hematology instruments typically comprise apparatus for aspirating a blood sample from an open or sealed container, and for dispensing one or more precise aliquots or volumes of the aspirated sample to a workstation for analysis. In general, such liquid aspiration/dispensing apparatus is either of two types: (i) those that use blood sampling valves (BSV's) to segment an aspirated blood sample into one or more precise volumes or aliquots for subsequent dispensing; and (ii) those that use a syringe pump to “suck and spit” a precise volume of blood.
Automated hematology instruments manufactured by Beckman Coulter, Inc. (e.g., the MAXM™, STKS™ and GEN•S™ blood analyzers) employ BSV's for segmenting aspirated blood samples into multiple aliquots for analysis. When operating in a fully automated mode, these instruments operate to cause an aspirating needle to (i) puncture the respective septum's of sealed vials containing a blood sample, (ii) dip below the surface of the blood sample in the vial, and (iii) aspirate a relatively large volume (e.g., 250 mircoliters) of blood into a fluid conduit connecting the aspiration needle and a vacuum pump used to provide the negative pressure required for aspiration. Positioned within the fluid conduit some distance from the aspiration probe is the BSV assembly that serves to segment the aspirated blood into several precise aliquots of differing volumes for subsequent dispensing. The BSV typically comprises three confronting and concentrically arranged disc elements, the center element being rotatably mounted for movement with respect to the outer elements. At least one disc element defines one or more aliquoting chambers, either in the form of (i) a groove(s) formed in a planar surface thereof that confronts a similar planar surface of one of the other discs, (ii) a through-hole connecting opposing planar surfaces of one of the disc elements, and/or (iii) one or more external loops of conduit connected to such grooves and/or through holes. The physical volume of each chamber(s) is sized to be equal to that of the aliquot(s) desired. A typical volume for an aliquot of blood to be analyzed in a hematology instrument is between approximately 5 and 75 mircoliters. When the rotatable disc is in a first position, the aliquoting chamber(s) is operatively connected to the aspirated blood supply, thereby enabling blood to enter and fill the chamber(s) under a vacuum force provided by the vacuum pump. When the rotatable disc is rotated to a second position, the blood supply is sheared off from the aliquoting chamber(s), and the desired volume of blood is trapped in the chamber(s). When the rotatable disc is subsequently rotated to a third position, the trapped blood can be dispensed from the aliquoting chamber(s) and advanced to a workstation for processing or analysis. Blood sampling valves of the type described are disclosed in the commonly assigned U.S. Pat. Nos. 4,445,391; 4,507,977; 4,702,889; 4,896,546; 5,158,751; 5,255,568; and 5,460,055.
To assure that the aliquoting chamber(s) of the BSV are filled with blood, it is common in the above instruments to position a pair of bubble detectors on opposites sides (i.e., on the upstream and downstream sides) of the valve. The detectors serve to sense that the valve is positioned within the aspirated volume of blood transported through the conduit, as well as to sense any air bubbles in the blood that would indicate that the valve chamber(s) are not full of blood at the time the rotatable disc element shears off the blood supply as it rotates to its second position. Such an arrangement is described in the commonly assigned U.S. Pat. No. 5,094,961.
When operating in a fully automated mode, hematology instruments of the above type are highly effective in quickly aspirating and dispensing precisely metered volumes of blood from a continuous supply of sealed vials. As noted above, they do require that each blood sample processed be relatively large in volume (e.g., 250 mircoliters or more) in order to enable the BSV to be located at a convenient distance from the aspirating needle. This large volume requirement can be problematic when the source of the blood sample is not large, as in the case when the blood is drawn from an infant or newborn. To enable the analysis of small, as well as other “special” blood samples, the above instruments are designed to operate in a “walk-up” mode in which a secondary aspiration probe directly coupled to the BSV (i.e., without any intervening conduit) is used to aspirate the “special” sample directly into the BSV. While this arrangement significantly reduces the blood volume requirement, it still requires that the probe itself be filled before any sample reaches the BSV for segmentation. Also, the secondary probe is not adapted to aspirate blood from sealed vials. Thus, in the “walk-up” mode, an operator must manually present an open vial sample to the secondary aspiration probe and visually assure that the probe tip is sufficiently below the level of blood in the vial as not to aspirate any air into the BSV's aliquoting chambers. This manual involvement is disadvantageous in that it reduces the throughput of the instrument.
As regards the syringe pump approach for aspirating and dispensing liquid, this approach requires precision movement of a plunger or diaphragm to move in a fluid circuit. As the plunger or diaphragm moves in a first direction, a negative pressure (vacuum) is created in an aspiration probe, thereby causing liquid to be sucked into the probe and its associated liquid conduit through the probe tip. As the plunger or diaphragm moves in the opposite direction, a positive pressure is created in the circuit, causing any liquid in the circuit to be ejected (dispensed or “spit”) through the probe tip. Obviously, the accuracy of this apparatus depends on the accuracy of movement of the moving member. While this apparatus is advantageous from the standpoint that it can aspirate and dispense very small volumes of liquid (since no conduit needs to be filled before aliquoting can occur, as is the case of the aforementioned BSV apparatus, it is less accurate than the BSV apparatus since the volume of liquid aspirated/dispensed relies entirely on the repeatability of the plunger/diaphragm movement. Typically, the accuracy of a syringe pump apparatus can vary by as much as 1-5 mircoliters between successive actuations.
SUMMARY OF THE INVENTION
In view of the foregoing, an object of the present invention is to provide an improved liquid aspiration/dispensing apparatus of the type described, an apparatus that is improved at least from the standpoint that it provides both the accuracy of the aforementioned BSV apparatus and the low volume feature of the aforementioned syringe pump apparatus.
The liquid aspirating/dispensing apparatus of the invention basically comprises:
(a) an aspirating probe (or needle) having a tubular housing with a proximal end and a distal end adapted to access a liquid in a container, the tubular housing having an internal volume substantially equal to a desired predetermined volume of liquid to be ultimately dispensed;
(b) aspiration means for causing liquid in the container to enter the distal end of the aspirating probe and to completely fill the tubular housing, whereby the aspirating probe contains a desired predetermined volume of liquid;
(c) sensing means for sensing that the tubular housing is completely filled with as
Cabrera Pedro P.
del Valle Roberto
Siddiqui Imran T.
Vargas Santos
Alter Mitchell E.
Coulter International Corp.
Gordon Brian R
Kurz Warren W.
Warden Jill
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