U.S. patent number 3,897,337 [Application Number 05/446,370] was granted by the patent office on 1975-07-29 for plasma separator assembly having interface-seeking piston with centrifugal valve.
This patent grant is currently assigned to Becton, Dickinson and Company. Invention is credited to Waldemar A. Ayres.
United States Patent |
3,897,337 |
Ayres |
* July 29, 1975 |
Plasma separator assembly having interface-seeking piston with
centrifugal valve
Abstract
A blood collection and separator assembly of the type suitable
for centrifuging to separate the plasma or serum from the cellular
phase of blood is disclosed. The assembly includes a collection
container and an interface-seeking piston having a centrifugal
valve associated therewith being slidably disposed therein for
opening the valve during centrifugation and for sealing off the
plasma or serum phase from the cellular or heavy phase of blood
after centrifuging is terminated. The piston is formed having a
specific gravity greater than the specific gravity of blood. The
piston is provided with a valve assembly which automatically opens
the valve when the assembly is subjected to centrifugal force.
Disposed in tandem relationship with the valve means is a filter
assembly to filter the plasma or serum as it passes through the
valve means when the assembly is being centrifuged and the piston
is moving downwardly into the container. The piston automatically
stops at the plasma/serum-cellular interface by clogging the filter
assembly with the cellular phase. When the centrifugal force is
terminated the valve means is closed and the piston forms a barrier
between the plasma or serum phase and the cellular phase.
Inventors: |
Ayres; Waldemar A. (Rutherford,
NJ) |
Assignee: |
Becton, Dickinson and Company
(East Rutherford, NJ)
|
[*] Notice: |
The portion of the term of this patent
subsequent to July 15, 1992 has been disclaimed. |
Family
ID: |
23772336 |
Appl.
No.: |
05/446,370 |
Filed: |
February 27, 1974 |
Current U.S.
Class: |
210/136; 210/314;
210/359; 210/516; 210/789; 422/918 |
Current CPC
Class: |
B01L
3/50215 (20130101) |
Current International
Class: |
B01L
3/14 (20060101); B01d 021/26 () |
Field of
Search: |
;23/23B,258.5,259,292
;128/2F,214R,218M,272
;210/83,84,109,131,359,514-518,DIG.23,DIG.24,136,314,316
;233/1A,1R,26 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Adee; John
Assistant Examiner: Spitzer; Robert H.
Attorney, Agent or Firm: Kane, Dalsimer, Kane, Sullivan and
Kurucz
Claims
What is claimed is:
1. A separator assembly capable of separating blood into a
plasma/serum or light phase and a cellular or heavy phase
comprising:
a container having at least one open end which is adapted to
receive blood for subsequent separation into a light phase and a
heavy phase;
a closure sealing the open end of the container, the closure being
formed of a self-sealing, elastomeric material which is penetrable
by a cannula through which blood to be separated is conducted into
the container;
an interface-seeking piston having a specific gravity relatively
greater than blood and slidably mounted in the container adjacent
one end thereof and being movable downwardly in said container due
to the influence of centrifugal force and having means on an outer
surface for providing sealing engagement with an inner surface of
the container;
a valve assembly mounted on the piston and disposed at the lower
end thereof, said assembly comprises a lower resilient diaphragm
mounted on the lower end of said piston and having apertures formed
therein, said apertures being normally closed and adapted to open
during the downward movement of the piston; an upper resilient
diaphragm mounted on the upper end of said piston, having apertures
formed therein, said apertures being normally closed and adapted to
open during the downward movement of the piston;
a filter assembly mounted between said valve assembly and said
upper diaphragm and being in fluid communication with the valve
assembly, said filter assembly including a lower coarse filter
having an average pore opening larger than the diameter of blood
cells, disposed adjacent said valve assembly and an upper fine
filter having an average pore opening smaller than the diameter of
blood cells, said fine filter disposed between the upper diaphragm
and said coarse filter, said filter assembly being capable of
removing substantially all solid material from the separated
plasma/serum phase; and
said fine filter providing piston stop means when said piston is at
the plasma/serum-cellular interface whereby the cellular phase
clogs the fine filter to prevent further upward flow of fluid
through the fine filter so that the piston automatically stops at
said interface and the upper diaphragm apertures close.
2. The separator assembly of claim 1 wherein the valve assembly
includes a weight mass disposed on the upper surface of said lower
diaphragm, said mass being forced downward against the lower
resilient diaphragm when the assembly is subjected to centrifugal
force whereby said lower diaphragm is stretched and the apertures
therein are opened.
3. The separator assembly of claim 1 wherein said filter assembly
is disposed in a passage formed through said piston, the upper and
lower ends of said passage being closed by said upper and lower
resilient diaphragms respectively.
4. An interface-seeking piston adapted for use for separating the
serum or plasma phase from the cellular phase of blood in a
separator assembly including a container, said piston having a
specific gravity relatively greater than blood and adapted to be
slidably mounted adjacent one end of the container and movable
downwardly in said container due to the influence of centrifugal
force and having means on an outer surface thereof for providing
sealing engagement with an inner surface of the container;
a valve assembly mounted on the piston and disposed at the lower
end thereof, said assembly comprises a lower resilient diaphragm
mounted on the lower end of said piston and having apertures
therein, said apertures being normally closed and adapted to open
during the downward movement of the piston;
a resilient upper diaphragm having apertures formed therein and
mounted at the upper end of said piston with said apertures being
normally closed and adapted to open during the downward movement of
the piston;
a filter assembly mounted between said valve assembly and said
upper diaphragm and being in fluid communication with the valve
assembly, said filter assembly including a lower coarse filter
having an average pore opening larger than the cellular phase,
disposed adjacent said valve assembly and an upper fine filter
having an average pore opening smaller than cellular phase; said
fine filter disposed between said upper diaphragm and said coarse
filter, said filter assembly being capable of removing
substantially all solid material from the separated plasma/serum
phase and said fine filter being adapted to provide piston stop
means when said piston is at the plasma/serum-cellular
interface.
5. The piston of claim 4 wherein the valve assembly includes a
weight-mass disposed on the upper surface of said lower diaphragm,
said mass being forced downward against the resilient lower
diaphragm when the piston is subjected to centrifugal force whereby
said lower diaphragm is stretched and the apertures therein are
opened.
6. The piston of claim 4 wherein said filter assembly is disposed
in a passage formed through said piston, the upper and lower ends
of said passage being closed by said upper and lower resilient
diaphragms respectively.
Description
BACKGROUND OF THE INVENTION
This invention plasma/serum generally to plasma/serum separator
assemblies and particularly to a plasma/serving separator having an
interface-seeking piston with a centrifugal valve assembly. The
piston is slidably disposed in a collection container for receiving
blood. The piston includes valve means which is normally closed but
which will automatically open when the assembly is subjected to
centrifugal force. The piston also includes a filter means disposed
in fluid communication with the valve means so that as the plasma
or serum passes through the valve means it is filtered to remove
any solid materials that may be present in the plasma or serum
phase and which provides means for stopping the piston at the
interface between the serum/plasma and cellular phase.
DESCRIPTION OF THE PRIOR ART
It is known to separate blood into its component parts by
centrifugation, for example, the assembly disclosed in U.S. Pat.
No. 2,460,641. However, this particular assembly does not employ a
means for sealing the separated plasma or serum phase from the
cellular phase.
It is also known to provide assemblies for manually separating the
plasma or serum phase from the cellular phase, for example, as
disclosed in U.S. Pat. Nos. 3,586,064; 3,661,265; 3,355,098;
3,481,477; 3,512,940 and 3,693,804. In all of these devices the
serum is collected in a blood collection container and means are
provided for separating the plasma or serum phase from the cellular
phase employing filters, valves, transfer tubes or the like.
It is also known to provide assemblies for the sealed separation of
blood in which a piston is actuated by centrifugal force such as is
disclosed in U.S. Pat. Nos. 3,508,653 and 3,779,383. These devices
use either a deformable piston made of a resilient material or
valve means associated with the piston to effect a sealed
separation after centrifugation.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a plasma/serum
separator assembly in which an interface-seeking piston
automatically stops when centrifuged at the plasma/serum-cellular
interface.
It is another object of the invention to provide a piston having a
centrifugal valve means that will not be accidentally opened when
the container is being filled with blood by the pressure difference
of blood at atmospheric pressure and the vacuum on the other side
of the valve. It is also an object of the invention to provide a
piston having a filter assembly which will prevent cellular
materials contained in the blood from passing into the separated
plasma or serum phase.
It is another object of the invention to provide a plasma/serum
separator assembly which is economical to manufacture and can be
used in conjunction with standard blood collecting equipment.
My invention generally contemplates the provision of a separator
assembly which includes a blood collection container for receiving
blood, the container having at least one open end which is adapted
to receive a closure for sealing the end of the container. An
interface-seeking piston is formed having a specific gravity
greater than the specific gravity of blood and having a centrifugal
valve means which automatically opens when the assembly is
subjected to centrifugal force. A filter assembly is disposed in
the piston in fluid communication with the valve means so that the
plasma and/or serum after passing through the valve means is
filtered to remove any solid materials contained therein. The
piston automatically stops when the filter assembly becomes clogged
with the heavy phase at the plasma/serum-cellular interface.
DESCRIPTION OF THE DRAWINGS
For a better understanding of the invention reference is had to the
drawings which illustrate a preferred embodiment of the invention
herein.
FIG. 1 is a sectional, elevational view of the plasma/serum
separator assembly illustrating a pointed cannula penetrating one
of the stoppered ends of the container through which blood is
introduced into the container prior to its separation.
FIG. 2 is an enlarged sectional, elevational view partly broken
away illustrating the position of the piston approaching the
plasma/serum-cellular interface while the assembly is being
centrifuged.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
For a better understanding of the invention herein a description of
the preferred embodiment is had which is illustrated in FIGS. 1 and
2.
In FIG. 1 separator assembly 10 comprises a tubular member or
container 12 which is sealed at its open ends by closure members 14
and 15. Closure members 14 and 15 are preferably made of
elastomeric material, for example, rubber, and are capable of being
penetrated by a cannula 16 so that blood can be transferred from a
blood source into the container under aseptic conditions. Closures
14 and 15 should be self-sealing so that when the cannula is
removed from closure 14 there will be no loss of blood passing
through the penetration portion of closure 14. As depicted in FIG.
1, blood is being conducted through cannula 16 and is shown filling
container 12 to about the point where piston 18 is positioned
adjacent closure member 15. Thereafter, cannula 16 is removed and
assembly 10 is ready for centrifuging for subsequent separation of
the collected blood into the plasma or serum phase and the cellular
phase. In this connection, apertures 37 of diaphragm 36 remain
closed while blood is filling container 12 and will not
accidentally open by the pressure differential between blood at
atmospheric pressure and the vacuum that is present in the filter
40 and at the top surface of diaphragm 36.
Disposed in container 12 is piston 18 which includes a tubular
metal insert 22 which is mounted in the annular recess 23 of piston
18. Metal insert 22 is preferably made of stainless steel or other
rigid chemically inert material having a specific gravity
substantially greater than blood. The body of piston 18 is
preferably formed of elastomeric material and is provided with
annular recess 23 which is dimensioned to receive tubular member 22
in an interference fit so that no air space remains in annular
recess 23.
The elastomeric portion of piston 18 comprises an outer wall 26 and
spaced therefrom is inner wall 28 in which their respective wall
surfaces define annular recess 23. Formed integrally with wall 26
is a plurality of radially spaced resilient sealing rings 30 which
contact the inner wall surface of container 12 in sealing
liquid-tight engagement. Piston 18 when mounted in the container
will maintain a liquid-tight sealing contact with the inner wall of
container 12 throughout the piston's path of travel within the
container during centrifuging. A longitudinally extending bore 32
provides a chamber for housing filter assembly 40. Valve means 34
includes a resilient diaphragm 36 and weighted mass 39. Diaphragm
36 is formed across the lower end of piston 18 to provide a barrier
or closure for bore 32 and is made of a suitable elastomer, for
example rubber. Also, positioned adjacent valve means 34, in bore
32, is filter assembly 40. Positioned within bore 32 and contacting
the inner face of diaphragm 36 is a weighted mass or tubular insert
39 preferably cylindrical and having a diameter substantially less
than the diameter of bore 32 which provides centrifugal valve
opening means for diaphragm 36. Mass 39 has a loose fit relative to
filter assembly 40. When the blood separator assembly is
centrifuged to effect separation of the cellular phase from the
plasma or serum phase, mass 39 presses against diaphragm 36 with
sufficient force to stretch diaphragm 36 downwardly to thereby open
apertures 37.
As shown in FIG. 2, filter assembly 40 includes coarse filter 42
which is mounted in bore 32 of piston 18 and fine filter 44 which
is secured with a suitable adhesive on to piston 18 so that it
covers the upper opening of bore 32. Filter 42 has an interference
fit relative to bore 32 so that filter 42 remains in fixed
position. Diaphragm 38 is also made of a suitable elastomer, for
example rubber, and is cemented or otherwise secured to the top of
wall 26 of piston 18. Diaphragm 38 is formed having one or more
apertures or slits which are normally closed but which are opened
when plasma/serum is passing through piston 18 as illustrated by
the direction of the arrows in FIG. 2.
Fine filter 44 has average pore openings less than the average
diameter of the red blood cells so that any plasma or serum
containing solid materials of the diameter of a red blood cell or
larger will be removed by filter 44 before passing through
apertures 39 of diaphragm 38. Coarse filter 42 has an average pore
size greater than the cellular phase of blood and serves as a
prefilter to take out larger particles such as fibrin strands or
clots from the plasma or serum before it reaches fine filter
44.
FIG. 2, which is an enlarged sectional view partly broken away,
illustrates the position of piston 18 approaching the
plasma/serum-cellular interface 50 during centrifugation and before
the cells pass through coarse filter 42 and clog fine filter 44
thereby stopping the descent of piston 18 at the interface. It
should be noted that apertures 37 and 41 of diaphragms 36 and 38
are open during the descent of piston 18 in container 12 but
apertures 41 will automatically close when fine filter 44 clogs
with red cells while apertures 37 of diaphragm 36 remain open even
though centrifuging continues. When centrifuging ceases apertures
37 of diaphragm 36 will automatically close. It should be noted
that piston 18 has a specific gravity substantially greater than
the specific gravity of blood. However, piston 18 will
automatically stop at the plasma/serum-cellular interface 50 when
filter 44 of piston 18 becomes clogged with the heavy cellular
phase, such as the red blood cells, thereby separating the light
phase plasma or serum from the heavy phase cellular material of
blood and will form a barrier between the two phases when
centrifuging is completed.
When using the assembly illustrated in FIGS. 1 and 2 after the
blood has been collected, assembly 10 is placed in a centrifuge
and, at first, is subjected to a spin speed which is suitable to
cause the heavy or cellular phase material to pass downwardly in
the container toward stopper 14 but the spin speed is insufficient
to cause the piston 18 to slide downwardly through the plasma/serum
phase. Then, the assembly is subjected to a higher spin speed which
causes mass 39 to press downwardly on diaphragm 36 additionally to
open apertures 37 in piston 18. Piston 18 then starts its movement
downwardly in the container and separated plasma or serum pass
through apertures 37 and through coarse filter 42 and fine filter
44. The hydrostatic pressure of the plasma/serum exerted against
diaphragm 38 causes it to stretch upwardly thereby opening valve
apertures 41 to permit the passage of separated plasma or serum to
the top side of piston 18. When piston 18 reaches the
plasma/serum-cellular interface, red cells and other portions of
the cellular phase pass through coarse filter 42 and are stopped by
fine filter 44 thereby causing filter 44 to become clogged and
effectively stop piston 18 at the plasma/serum-cellular interface
50. Thereafter, even though centrifuging continues diaphragm 38
returns to its normal relaxed position as in FIG. 1 with apertures
41 closed. However, until centrifuging ceases apertures 37 of
diaphragm 36 remain open due to mass 39 exerting a force against
diaphragm 36. When centrifuging ceases, resilient diaphragm 36
moves mass 39 to its normal position thereby automatically closing
apertures 37. When centrifuging is completed the piston is
established as a sealed barrier at the interface between the
serum/plasma phase and the cellular phase.
From the foregoing, it is readily observed that a plasma/serum
separator assembly in which an interface-seeking piston with a
centrifugal valve is disclosed the assembly is described in which
blood can be collected, centrifuged, separated into its component
phases and is capable of being shipped through the mail for further
analytical determinations without the plasma or serum mixing with
the cellular phase even though the assembly is inverted and handled
roughly.
While variations of the invention herein may be had the objectives
of the invention have been illustrated and described and it is
contemplated that changes in design can be made without departing
from the spirit of the invention described herein.
* * * * *