Serum/plasma separator with centrifugal valve seal

Abstract

A self-contained fluid separator assembly is disclosed capable of separating blood into its component parts of plasma or serum, the light phase, and the cellular portion, the heavy phase. The assembly comprises a container having at least one open end for receiving blood for subsequent separation and a closure sealing the open end of the container. The closure is formed of a self-sealing elastomeric material which is penetrable by a pointed hollow needle through which the blood to be separated is conducted into the container. A piston is slidably disposed in the container with its outer surfaces in sealing contact with the inner surfaces of the container. Centrifugally actuated valve means in the form of a distortable closed end tube with side slit, normally closed, is provided on the piston and automatically opens in response to centrifugal force. When blood in the container is subjected to centrifugal force it first separates into its light phase and heavy phase. Thereafter the piston with open valve moves down through the light phase while retaining sealing engagement with the inner surfaces of the container. Positive stop means is provided on the container between its ends so that the piston as it moves through the light phase will contact the stop means and stop at a predetermined distance above the closure bottom of the tube. Upon termination of the centrifugal force, the valve means automatically closes to provide an impervious barrier between the separated light and heavy phases of the blood. SU BACKGROUND OF THE INVENTION 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 collectd 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 distortable piston made of a resilient material or valve means associated with the piston to affect a sealed separation after centrifugation. FIELD OF THE INVENTION The present invention relates to separators and more particularly to a device for separating blood plasma from cellular material of the type disclosed in commonly assigned application Ser. No. 247,483 filed Apr. 25, 1972. SUMMARY OF THE INVENTION The invention generally contemplates the provision of an improved self-contained sealed fluid separator assembly capable of separating blood into its component parts of plasma or serum as the light phase and the cellular portion as the heavy phase and establishing a sealed barrier therebetween without the necessity of opening the container or decanting the separated light phase from the heavy phase. It is an object of the invention to automatically separate blood into its component phases by simply subjecting the self-contained assembly to centrifugal force so that upon completion of the centrifuging operation an impervious barrier separates the light phase from the heavy phase of the blood. The assembly is capable of withstanding rough handling through the mails, inversion of the container without remixing the component phases and preventing various chemical constituents in the light phase from leaking into and mixing with the heavy phase or vice versa. It is a further object of the invention to provide a self-contained assembly for separating blood into its component parts which is inexpensive to manufacture, simple to assemble and easy to use. The separator assembly for separating blood into its component parts of plasma or serum, the light phase, and cellular portion, the heavy phase, is a self-contained unit which requires only that a sample of blood to be separated be provided within the container. The container is formed having at least one open end which is adapted to receive blood for separation into its component phases. A closure is mounted in the open end for sealing the container, this closure being formed of a self-sealing elastomeric material which is penetrable by a pointed hollow needle through which blood to be separated is conducted into the container. A piston is slidably mounted in the container having its outer cylindrical surfaces in sealing engagement with the inner surfaces of the container. Centrifugally actuated valve means in the form of a distortable closed end tube with side slit, is disposed on said piston and is normally closed when there is a minimum of centrifugal force acting on the piston. The valve means automatically opens in response to a substantial increase of centrifugal force. When the container is subjected first to moderate centrifugal force the piston stays at the top of container 12 and the blood separates into its light phase and heavy phase. When the centrifugal force thereafter is substantially increased, the valve means automatically opens with the light phase passing up through the valve means while the piston moves down through the light phase retaining its sealing engagement with the inner surfaces of the container. A stop means is formed on the container and disposed a predetermined distance from the bottom of the container which is remote from the piston in its initial position. The piston after moving through a major part of the light phase is caused to stop when it reaches the stop means. When centrifugation ceases, the valve means automatically shifts from the open position to the closed position to provide an impervious barrier between the separated light phase and heavy phase of the blood. Thereafter, the separated sample is ready for testing.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the invention reference is had to the drawings which illustrate the preferred embodiments of the invention herein.

FIG. 1 is a sectional elevational view of the separator assembly illustrating a pointed cannula penetrating one of the closures through which blood is introduced into the container prior to separation with the centrifugally actuated valve in closed position; and

FIG. 2 is a view similar to FIG. 1 illustrating the separation of the blood into the light phase and heavy phase with the valve open and the piston travelling towards the stop means.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In FIG. 1, the separator assembly 10 comprises a tubular member or container 12 having mounted in each of the open ends 11 and 15 closures 14 and 16. Closures 14 and 16 are made of a self-sealing elastomeric material such as rubber. Closure 16 is capable of being penetrated by cannula 18 for conducting blood into the container. When the cannula is removed, the closure reseals with no loss of blood.

Closure 14 is formed with a depending cylindrical body portion 20 and an integral flanged head portion 22. Body portion 20 has a diameter slightly greater than the internal diameter of the container 12 so that closure 14 when mounted into end 11 provides an interference fit to seal this end. Head portion 22 may be shaped in the form of a hexagon and is slightly greater in diameter than body portion 20 which permits the assembly to be positioned on its side without danger of rolling.

Stopper 16 has a cylindrical body portion 28 and an integrally formed cylindrical head portion 30 having an axial recess 24. Body portion 28 has an annular recess 29 to provide a self-sealing penetrable zone 31 to facilitate insertion of cannula or pointed hollow needle 18 with minimum force while maintaining a sealed closure. As noted above, stopper or closure 14 as well as 16 is inserted into ends 11 and 15 in compression to maintain ends 11 and 15 of container 12 in sealed gas tight engagement.

Tubular member or container 12 is formed preferably of glass but any other suitable material may be employed. Intermediate ends 11 and 15 of tubular member 12 is an annular groove 32 forming a constriction and a stop means 34 as a part of the inner surfaces of container 12. Thus, as piston 40 moves from the initial starting position illustrated in FIG. 1 to the terminal position after the separation of the light phase from the heavy phase, the piston comes to rest at the stop means 34. The piston may be formed of elastomeric material and preferably has greater specific gravity than blood so that the centrifugal valve will open and so that the piston will move through the light phase when the increased centrifugal force is applied to the assembly and eventually automatically come to rest at stop means 34. The seal of the piston with respect to the inner surfaces of the container is constant throughout its travel from its initial position of FIG. 1 to its terminal postion. Piston 40 includes a tubular metal insert 52 which is mounted in annular recess 54. Metal insert 52 is preferably made of stainless steel or other rigid, chemically inert material having a specific gravity greater than blood. Annular recess 54 is dimensioned to receive tubular member 52 in an interference fit so that no air space remains in annular recess 54.

The elastomeric portion of piston 40 comprises an outer wall 48 and spaced therefrom is inner wall 46 which defines annular recess 54. Formed integrally with wall 48 are a plurality of axially spaced sealing rings 50 which contact the inner wall surfaces 13 of container 12 in sealing engagement. Piston 40 when mounted in container 12 will maintain sealing contact with inner surface 13 of container 12 throughout its path of travel within container 12.

During high speed centrifuging piston 40 will start to move downwardly. At the same time and in most instances before, because of the greater specific gravity of the valve means 42 as compared with the blood, closed end tube 44 will distort downwardly and the side slit 45 will automatically open and will enable the separated light phase liquid to pass upwardly through the opening and enable piston 40 to move from its initial position of FIG. 1 to its final position while maintaining sealing engagement with the inner wall 13 of container 12. When piston 40 stops its movement in container 12 and comes to rest on stop means 34, and when centrifugal force is terminated the closed end tube 44 will return to its normal position so that the side slit 45 is closed. A portion of the light phase remains above the separated heavy phase and is not utilized as part of the separated light phase.

When operating the separator assembly of the invention herein it is preferred that the assembly be evacuated so that when cannula 18 penetrates closure 16 blood will automatically fill container 12. It is also contemplated to provide a separator assembly suitable for use with the blood collecting assembly disclosed in U.S. Pat. Nos. 2,460,641; 3,469,572 and 3,494,352. It is important when filling the assembly 10 that blood be introduced into container 12 through the stopper 16 mounted on the bottom of the container to obviate the possibility of having blood cells trapped between the piston 40 and stopper 22 which will later separate to form the chamber where the light phase will be collected thus contaminating the light phase with blood.

After cannula 18 is withdrawn and container 12 is filled with blood the assembly is placed in a centrifuge and the blood is separated initially employing moderate centrifugal forces which do not cause the piston 40 to move from its initial position nor valve means 42 to open. This precipitates or separates the blood cells or blood clot into the tube portion below constriction stop means 34. Thereafter the rotational speed of the centrifuge is increased which causes a substantial downward thrust on the piston. Before the time piston 40 starts to move valve means 42 automatically opens and thereafter the piston moves downwardly through the light phase with the light phase passing up through the valve means. Piston 40 maintains sliding and sealing engagement with the inner surface 13 of container 12. The piston completes its movement when it engages stop means 34 and then centrifuging is terminated. The valve means 42 will close to thereby establish an impervious barrier between the light and heavy phase of the blood.

The separated blood sample is ready for use. As desired, the serum or plasma can be taken from one end and/or the concentrated red cells can be taken from the other end.

While variations of the invention herein may be had, the objectives of the invention have been illustrated and described.

Claims

I claim:

1. A self-contained fluid separator assembly, capable of separating blood into its component parts of light phase plasma or serum and heavy phase cellular portion, comprising:

a. 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;

b. 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;

c. a piston having a specific gravity relatively greater than the cellular portion of the blood and slidably mounted in the container and having means on an outer surface in sealing engagement with an inner surface of the container;

d. centrifugally actuated valve means associated with said piston, said valve means being in the form of a downwardly projecting distortable closed end tube with a side slit and having a specific gravity greater than blood said slit openable when the valve means distorts due to substantial centrifugal force acting upon it, said valve means being normally closed when there is a minimum of centrifugal force acting on the valve means, so that when said container is subjected to moderate centrifugal force the blood separates into its light phase and heavy phase but the piston stays in the upper portion of the container, and subsequently when increased centrifugal force is used the valve means automatically opens with the light phase passing up through the valve means enabling the piston to move down through the light phase while retaining sealing engagement with the inner surface of the container; and

e. mechanical stop means on the container whereby the piston when moving through the light phase will stop a predetermined distance from one of the ends of the container followed by termination of substantial centrifugal force which permits the valve means to close to provide an impervious barrier between the separated light phase and heavy phase of the blood.

2. A self-container fluid separator of claim 1, wherein the stop means on the container is an annular groove interposed between the ends of the container forming an annular constriction of the inner surface of the container so that said piston is prevented from passing the stop means when subjected to centrifugal forces.

3. The invention in accordance with claim 1, wherein at least one annular sealing ring is provided on the periphery of the piston and in sealing engagement with the interior of the container.

4. The invention in accordance with claim 1, wherein the valve means is independent of the piston sealing means.

5. The piston of claim 1, wherein the piston includes a central passageway and a distortable tube having an opened upper end and forms an integral downward extension of the piston, the bore of the tube being aligned with the piston central passageway, the bottom end of the tube being closed, and the side slit being interposed between the ends of the tube and extending only partially across the tube with the uncut part of the tube opposite the slit being the distortable zone of the tube about which distortion takes place when the closed end tube is subjected to centrifugal force.