Imperforate bowl: centrifugal separators – Process
Reexamination Certificate
1999-09-22
2001-10-16
Cooley, Charles E. (Department: 1723)
Imperforate bowl: centrifugal separators
Process
C494S010000, C494S027000, C494S041000, C494S042000
Reexamination Certificate
active
06302836
ABSTRACT:
BACKGROUND—FIELD OF INVENTION
This invention relates to a method for partitioning a blood sample and obtaining clean serum from an unopened vacuum blood collection tube assembly.
BACKGROUND—DESCRIPTION OF PRIOR ART
Hospital clinical laboratories often analyze blood serum for various chemical constituents by using automated analyzers. The blood is first drawn from a patient into a vacuum blood collection tube assembly. After the blood clots this tube is placed in a centrifuge which causes the clot material to move to the end of the tube away from the tube stopper. The less dense serum is then between the clot material and the tube stopper.
Serum is then removed from the tube and presented by various methods to a blood serum chemistry analyzer. One method requires removal of the stopper and removal of the serum by pipetting or decanting the serum into a serum cup from which serum is dispensed to an analyzer. These operations may be manual or automated or a mixture of these methods.
Serum may be removed from an unopened vacuum blood collection tube assembly following centrifugation without removal of the stopper by piercing the elastomeric stopper with a cannula so that the distal end of the cannula is fully immersed in serum. Serum is then aspirated from the tube via the cannula by a syringe or pump and delivered to a serum cup or an analyzer. These operations may be manual or automated or a mixture of these methods.
Various apparatus have been constructed to automate the operations of separating serum from the clot by centrifugation, removal of the stopper, and removing and dispensing of serum. Automation of centrifugal separation of serum and clot using conventional centrifuges has proven to be complex and costly due to the large number of separate operations required. These include the following:
(a) removing the blood tube from a carousel or rack
(b) placing the blood tube in a centrifuge rotor
(c) repeating (a) and (b) for a number of blood tubes
(d) balancing the centrifuge rotor
(e) closing the centrifuge lid
(f) rotating the centrifuge rotor for a predetermined time and speed sufficient to separate serum from the clot
(g) stopping the centrifuge rotor
(h) opening the centrifuge lid
(i) removing each tube from the centrifuge rotor
(j) placing each blood tube in a carousel or rack suitable for subsequent operations of serum removal and dispensing.
These operations have proven to be difficult to automate economically rendering this approach of limited value.
In an effort to more readily automate the centrifugation step McEwen et al in U.S. Pat. No. 5,308,506 issued May 3, 1994 employ the method of rotating the vacuum blood collection tube assembly about its longitudinal axis. This method thus avoids most of the above (a) through (j) steps. However, McEwen et al then employ a slidable piston positioned within the vacuum blood collection tube assembly during centrifugation to preserve the separation of serum and clot after rotation of the blood tube ceases. McEwen et al also use a special device, shown on
FIG. 8
of his patent, to remove and dispense serum from an unopened vacuum blood collection tube assembly. Removal of serum from an unopened vacuum blood collection tube assembly is highly desirable since it avoids biohazardous aerosols sometimes generated by removal of the blood tube stopper. These aerosols have caused infections with HIV and hepatitis.
The McEwen invention suffers from the following shortcomings which have limited its utility:
1. It requires a special vacuum blood collection tube assembly containing a slidable piston which adds cost to the blood tube. It also adds more work and the need for more storage space in the laboratory stockroom.
2. It requires a special device to remove serum from an unopened vacuum blood collection tube assembly which adds cost to the process since the special device must either be disposable or must be washed after each use to avoid sample carryover problems. It also adds more work and the need for more storage space in the laboratory stockroom if disposable.
3. It requires a special centrifuge apparatus to rotate the vacuum blood collection tube assembly about its longitudinal axis.
4. The operations of serum separation by centrifugation, serum removal, and serum dispensing are all separate operations not easily automated and integrated. They thus require manual interventions which lead to significant time and labor costs.
5. There is no provision for the removal from the dispensed serum contaminants such as air, microclots, and cellular aggregates which can cause malfunction of automated serum chemistry analyzers.
OBJECTS AND ADVANTAGES
Accordingly, in addition to avoiding many of the shortcomings of the McEwen invention, further objects and advantages of the present invention are;
(a) to provide an apparatus and method which fully automates and integrates the operations of separation of serum from clots, removal of serum from an unopened vacuum blood collection tube assembly, and dispensing of removed serum to a remote receiver vessel.
(b) to provide the operations of (a) while using a standard, unmodified vacuum blood collection tube assembly without any special features such as an enclosed slidable piston
(c) to provide the operations of (a) without requiring any one time use or disposable device
(d) to provide the operations of (a) and delivering clean serum free from contaminants such as air, microclots, cellular aggregates, or fibrin strands
(e) to provide clean serum from an unopened vacuum blood collection tube assembly including the operations of separating serum from the clot, removing and cleaning serum, and dispensing a metered volume of serum in less than one minute
(f) to provide the operations of (e) with significantly less cost for labor and materials than conventional methods
(g) to provide the operations of (e) without use of devices requiring disposal
(h) to provide for the washing and drying of reusable serum conduits to reduce sample carryover to acceptable levels
(i) to provide means for dispensing a predetermined volume of clean serum from an unopened vacuum blood collection tube assembly to a remote receiver vessel.
Other objects and advantages will become apparent from a consideration of the ensuing description and drawings.
REFERENCES:
patent: 3061280 (1962-10-01), Kraft et al.
patent: 3159384 (1964-12-01), Davis
patent: 3190547 (1965-06-01), Shanley
patent: 3199775 (1965-08-01), Drucker
patent: 3235173 (1966-02-01), Unger
patent: 3596673 (1971-08-01), Laucournet
patent: 3882716 (1975-05-01), Beiman
patent: 4004883 (1977-01-01), Meyer et al.
patent: 4555183 (1985-11-01), Thomas
patent: 4828716 (1989-05-01), McEwen et al.
patent: 5030341 (1991-07-01), McEwen et al.
patent: 5195825 (1993-03-01), Ringrose
patent: 5308506 (1994-05-01), McEwen et al.
patent: 5840253 (1998-11-01), Chase et al.
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