US3897337A - Plasma separator assembly having interface-seeking piston with centrifugal valve - Google Patents

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/serumcellular 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.

Description

United States Patent Ayres INTERFACE-SEEKING PISTON WITH CENTRIFUGAL VALVE PLASMA SEPARATOR ASSEMBLY HAVING [75] Inventor: Waldemar A. Ayres, Rutherford,

[73] 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.

[22] Filed: Feb. 27, 1974 [21] Appl. No.: 446,370

[52] US. Cl. 210/136; 210/314; 210/359;

210/516; 210/DIG. 23

[51] Int. Cl B01d 21/26 [58] Field ofSearch 23/230 B, 258.5, 259, 292;

128/2 F, 214 R, 218 M, 272; 210/83, 84, 109,131, 359, 514-518, DIG. 23, DIG. 24,

Primary Examiner-John Adee Assistant EraminerRobert H. Spitzer Attorney, Agent, or Firm-Kane, Dalsimer, Kane, Sullivan and Kurucz [57] 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 theplasma 136, 314, 316', 233/1 A, l R, 26 or serum as it passes through the valve means when the assembly is being centrifuged and the piston is [56] References Cited moving downwardly into the container. The piston au- UNITED STATES PATENTS tomatically stops at the plasma/serum-cellular inter- 2,577,7s0 12/1951 Lockhart 128/272 X face by cloggmg the filter assembly.wlth T cellular 3 539 300 11/1970 Stone n ZIO/DIG. 24 phase. When thecentrifugal force 18 terminated the 3:647:07) 3/1972 Adler I l 210/83 valve means is closed and the piston forms a barrier 3,661,265 5/1972 Greenspan 210/359 between the plasma or Serum Phase and the cellular 3,741,400 6/1973 Dick 2lO/DIG. 23 phase. 3,782,548 1/1974 Bowen 2l0/D1G. 23

6 Claims, 2 Drawing Figures IO "T= 1::

1 PLASMA SEPARATOR ASSEMBLY HAVING INTERFACE-SEEKING PISTON WITH CENTRIFUGAL VALVE 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 US. 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 plas ma/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 interfaceseeking 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 orcontainer 12 which is sealed at its open ends byclosure 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 acannula 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 fromclosure 14 there will be no loss of blood passing through the penetration portion ofclosure 14. As depicted in FIG. 1, blood is being conducted through cannula l6 and is shown fillingcontainer 12 to about the point wherepiston 18 is positionedadjacent 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 ofdiaphragm 36 remain closed while blood is fillingcontainer 12 and will not accidentally open by the pressure differential between blood at atmospheric pressure and the vacuum that is present in thefilter 40 and at the top surface ofdiaphragm 36.

Disposed incontainer 12 ispiston 18 which includes atubular metal insert 22 which is mounted in theannular recess 23 ofpiston 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 ofpiston 18 is preferably formed of elastomeric material and is provided withannular recess 23 which is dimensioned to receivetubular member 22 in an interference fit so that no air space remains inannular recess 23.

The elastomeric portion ofpiston 18 comprises anouter wall 26 and spaced therefrom isinner wall 28 in which their respective wall surfaces defineannular recess 23. Formed integrally withwall 26 is a plurality of radially spacedresilient sealing rings 30 which contact the inner wall surface ofcontainer 12 in sealing liquidtight engagement. Piston 18 when mounted in the container will maintain a liquidtight sealing contact with the inner wall ofcontainer 12 throughout the pistons path of travel within the container during centrifuging. A longitudinally extendingbore 32 provides a chamber forhousing filter assembly 40. Valve means 34 includes aresilient diaphragm 36 and weightedmass 39.Diaphragm 36 is formed across the lower end ofpiston 18 to provide a barrier or closure forbore 32 and is made of a suitable elastomer, for example rubber. Also, positioned adjacent valve means 34, inbore 32, isfilter assembly 40. Positioned withinbore 32 and contacting the inner face ofdiaphragm 36 is a weighted mass ortubular insert 39 preferably cylindrical and having a diameter substantially less than the diameter ofbore 32 which provides centrifugal valve opening means fordiaphragm 36.Mass 39 has a loose fit relative to filterassembly 40. When the blood separator assembly is centrifuged to effect separation of the cellular phase from the plasma or serum phase,mass 39 presses againstdiaphragm 36 with sufficient force to stretchdiaphragm 36 downwardly to therebyopen apertures 37.

As shown in FIG. 2,filter assembly 40 includescoarse filter 42 which is mounted inbore 32 ofpiston 18 andfine filter 44 which is secured with a suitable adhesive on topiston 18 so that it covers the upper opening ofbore 32.Filter 42 has an interference fit relative to bore 32 so thatfilter 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 ofwall 26 ofpiston 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 throughpiston 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 byfilter 44 before passing throughapertures 39 ofdiaphragm 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 reachesfine filter 44.

FIG. 2, which is an enlarged sectional view partly broken away, illustrates the position ofpiston 18 approaching the plasma/serum-cellular interface 50 during centrifugation and before the cells pass throughcoarse filter 42 and clogfine filter 44 thereby stopping the descent ofpiston 18 at the interface. It should be noted thatapertures 37 and 41 ofdiaphragms 36 and 38 are open during the descent ofpiston 18 incontainer 12 butapertures 41 will automatically close whenfine filter 44 clogs with red cells whileapertures 37 ofdiaphragm 36 remain open even though centrifuging continues. When centrifuging ceasesapertures 37 ofdiaphragm 36 will automatically close. It should be noted thatpiston 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 whenfilter 44 ofpiston 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 towardstopper 14 but the spin speed is insufficient to cause thepiston 18 to slide downwardly through the plasma/serum phase. Then, the assembly is subjected to a higher spin speed which causesmass 39 to press downwardly ondiaphragm 36 additionally to openapertures 37 inpiston 18.Piston 18 then starts its movement downwardly in the container and separated plasma or serum pass throughapertures 37 and throughcoarse filter 42 andfine filter 44. The hydrostatic pressure of the plasma/serum exerted againstdiaphragm 38 causes it to stretch upwardly thereby openingvalve apertures 41 to permit the passage of separated plasma or serum to the top side ofpiston 18. Whenpiston 18 reaches the plasma/serum-cellular interface, red cells and other portions of the cellular phase pass throughcoarse filter 42 and are stopped byfine filter 44 thereby causingfilter 44 to become clogged and effectively stoppiston 18 at the plasma/serum-cellular interface 50. Thereafter, even though centrifuging continuesdiaphragm 38 returns to its normal relaxed position as in FIG. 1 withapertures 41 closed. However, until centrifuging ceasesapertures 37 ofdiaphragm 36 remain open due tomass 39 exerting a force againstdiaphragm 36. When centrifuging ceases,resilient diaphragm 36 movesmass 39 to its normal position thereby automatically closingapertures 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 interfaceseeking 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.

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.

Claims (6)

1. A SEPARATOR ASSEMBLY CAPABLE OF SEPARATING BLOOD INTO A PLASMA/SERUM ORLIGHT PHASE AND A CELLULAR OR HEAVY PHASE COMPRISING: A CONTAINER HAVING AT LEAST ONE OPEN ND 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 EHICH 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 HE REFLUENCE 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 IAPHRAGM SAID 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.

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