US3862042A

US3862042A - Serum/plasma separator - piston with red-cell trapping surfaces

Info

Publication number: US3862042A
Application number: US446391A
Authority: US
Inventors: Waldemar A Ayres
Original assignee: Becton Dickinson and Co
Current assignee: Becton Dickinson and Co
Priority date: 1974-02-27
Filing date: 1974-02-27
Publication date: 1975-01-21
Anticipated expiration: 1992-01-21

Abstract

A self-contained fluid separator assembly capable of separating blood into its component parts of plasma or serum, the light phase, and cellular portion, the heavy phase, is disclosed. A piston is slidably disposed in a container having its lateral outer surfaces in sealing contact with the inner surfaces of the container. Pressure responsive valve means is provided on the piston. The piston also has a throat portion leading from its lower surface to the orifices of the valve means. The walls of the throat are serrated, with a series of ridges which serve to create cavitites or pockets where the velocity of fluids flowing through the throat is reduced. A stop means is formed on the container so that the piston as it moves through the light phase will contact the stop means and stop a predetermined distance from the closure means.

Description

[ 1 Jan. 21, 1975 SERUM/PLASMA SEPARATOR PISTON WITH RED-CELL TRAPPING SURFACES [75] Inventor: Waldemar A. Ayres, Rutherford,

[73] Assignee: Becton, Dickinson and Company,

East Rutherford, NJ.

22 Filed: Feb. 27, 1974 211 Appl. No.: 446,391

[52] U.S. Cl 210/516, 23/359, 128/272, 210/532, 210/DIG. 23 [51] Int. Cl B0ld 21/26 [58] Field of Search 23/230 B, 258.5, 259, 292; 128/214 R, 2 F, 272, 218 M; 210/83, 84, 131, 359, 514-518, 532, DIG. 23, DIG. 24;

Primary Examiner-John Adee Assistant ExaminerRobert G. Mukai Attorney, Agent, or Firm-Kane, Dalsimer, Kane, Sullivan and Kurucz [57] ABSTRACT A self-contained fluid separator assembly capable of separating blood into its component parts of plasma or serum, the light phase, and cellular portion, the heavy phase, is disclosed. A piston is slidably disposed in a container having its lateral outer surfaces in sealing contact with the inner surfaces of the container. Pressure responsive valve means is provided on the piston. The piston also has a throat portion leading from its lower surface to the orifices of the valve means. The walls of the throat are serrated, with a series of ridges which serve to create cavitites or pockets where the velocity of fluids flowing through the throat is reduced. A stop means is formed on the container so that the piston as it moves through the light phase will contact the stop means and stop a predetermined distance from the closure means.

5 Claims, 2 Drawing Figures SERUM/PLASMA SEPARATOR PISTON WITH RED-CELL TRAPPING SURFACES BACKGROUND OF THE INVENTION 1. Field of the Invention The invention concerns apparatus for the separation and isolation of blood plasma and blood serum from whole blood.

2. Brief Description of the Prior Art It is known to separate blood into its component parts by centrifugation, particularly employing a sealed container such as is disclosed in U.S. Pat. No. 2,460,641. This patent discloses a container having a closure at its open end which is capable of being penetrated by a cannula through which blood passes into the container. Clinical laboratories have heretofore used this device to collect a blood sample for subsequent separation into a light phase, i.e., the serum or plasma and the heavy phase, i.e., the cellular portion. The light phase is then decanted from the cellular portion by any conventional means, for example by the use of a syringe fitted with a cannula, or a pipette, or the like.

An apparatus also heretofore employed for the separation of blood is disclosed in US. Pat. No. 3,508,653. This patent discloses a self-contained assembly for separation of body fluid, such as blood, in which a deformable piston is disposed in the container and is positioned initially adjacent the stopper for closing the container. After the blood to be separated is in the container the assembly is centrifuged. After the blood is separated, increased centrifugal force is applied to the container, the seal between the inner surface of the container and piston is broken and the piston is deformed, moving down through the light phase with the light phase passing solely around the lateral surfaces of the piston and the inner surfaces of the container. When the piston reaches the interface between the light phase and the heavy phase, the piston movement is stopped, the force is terminated, and the seal is reestablished between the inner surface of the container and the resilient piston to present a barrier between the two phases.

Disclosed in my US. Pat. No. 3,799,383 is a serumplasma separator of the type contemplated herein and as compared with which the present apparatus utilizes certain different principles and different structures. The piston component of this prior art device is disclosed as having a valve means in association therewith through which the light phase blood component passes during piston descent by centrifugation. A smoothwalled throat leading to the valve means directs the flow of liquid phase component to the valve means. In recognition of the fact that small particles of solid materials normally found in blood may be carried with liquid components through the valve means, a preferred embodiment of the apparatus disclosed in US. Pat. No. 3,779,383 comprises one wherein a filter element is disposed in the throat leading to the valve means.

The present invention, provides means increasing the likelihood of trapping small blood clots or other undesirable material.

Other devices known to the art are generally the filtration devices which separate blood into its component phases such as those disclosed in US. Pat. Nos. 3,481,477 and 3,512,940.

SUMMARY OF THE INVENTION The invention comprises: a self-contained fluid separator assembly capable of separating blood into its component parts of plasma or serum and cellular part 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 selfsealing 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 greater than the cellular portion of the blood and slidably mounted in the container and having means on its lateral outer surface in sealing engagement with the inner surfaces of the container; (d) pressure responsive valve means associated with said piston, said valve means being normally closed when there is a minimum of pressure differential on different portion of the valve means and which automatically opens in response to a substantial pressure differential 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; (e) a throat within said piston leading from the lower surface thereof to the orifices of said valve means and having walls which are interrupted with a series of ridges and through which the said light phase must pass to reach said valve means; and (f) 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 the differential pressure which permits the valve means to automatically shift from an open position to a closed position to provide an impervious barrier between the separated light phase and heavy phase of the blood.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional side elevational view of a separator assembly of the invention illustrating a cannula penetrating one of the closures through which blood is introduced into the container prior to separatlon.

FIG. 2 is a view similar to FIG. 1 illustrating the sepa ration of the blood into the light phase and heavy phase with the improved piston engaging the stop means.

DETAILED DESCRIPTION OF THE INVENTION For a better understanding of the invention, a description of the drawings of the illustrative embodiments is had, particularly with respect to the embodiments shown in FIGS. 1 through 2.

Referring to FIG. 1, it is seen that the separator assembly 10 comprises a tubular member or container 12 having mounted in each open end 11, 15 closures l4 and 16. Closures l4 and 16 are made of a self-sealing elastomeric material, such as rubber, which are capable of receiving cannula 18 penetrated therethrough as illustrated in FIG. 1, for conducting blood into the container. When the cannula is removed the closure is resealed with no loss of blood passing through the penetration portion as illustrated in FIG. 2.

Closure 14 is formed having a depending cylindrical body portion and a flanged head portion 22 integrally formed therewith. 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 a pressure fit to seal the end. Head portion 22 is 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 is formed preferably of the same material as stopper l4. Stopper 16 has a cylindrical body portion 28 and an integrally formed 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 18 with minimum force while maintaining a sealed closure. As noted above, stoppers l4 and 16 are inserted respectively into ends 11 and 15, in compression, to maintain ends 11 and 15 of container 12 in sealed engagement.

Tubular member or container 12 is formed preferably of glass but a suitable plastic material may be employed. Intermediate ends 11 and 15 of tubular member 12 is an annular groove 32 which forms a stop means 34 as a part of the inner surfaces of container 12. Piston 40 is heavier than the light phase of the blood and moves downwardly through the blood during high speed centrifugation. 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, as shown in FIG. 2, the piston comes to rest at the stop means 34 formed by annular groove 32 of container 12. The seal of the piston, with respect to the inner surface of the container, is maintained throughout its travel-from its initial position of FIG. 1 to its terminal position of FIG. 2.

Piston 40 includes a tubular metal insert 52 which is mounted in annular recess 54 of piston 40. Metal insert 52 is preferably made of stainless steel or other rigid, chemically inert material having a specific gravity greater than blood. Piston 40 is formed of elastomeric material and is provided with annular recess 54 which is dimensioned to receive tubular member 52 in interference fit sothat 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 the centrifuging operation piston 40 descends and this produces a pressure differential on the opposite sides of the diaphragm portion 44 of piston 40. Diaphragm 44 has a relatively small thickness and lies adjacent stopper 14 in its initial position as seen in FIG. 1. Diaphragm 44 is made of a resilient material and is provided with a plurality of apertures 42 extending therethrough. Diaphragm portion 44 of piston 40 normally closes throat 80 within piston 40 which leads from the lower surface 82 of piston 40 to apertures 42. As the assembly is being subjected to increased centrifugal force causing the piston to descend, the light phase, which is separated from the heavy phase of the blood, will pass into throat and be guided to apertures 42. Also, since the centrifugal force acting on piston 40 will start to move the piston downwardly, the diaphragm 44 will stretch into a dome shape which will open resilient apertures 42. This will enable light phase liquid to flow up through apertures 42 and permit piston 40 to move from its initial position of FIG. 1 to its final position of FIG. 2 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, the pressure differential on each side of diaphragm 44 becomes substantially equalized and valve means 42 automatically shifts from the open position to the closed position even though the assembly is still being subjected to centrifugal forces.

As seen in FIG. 1, the inner surface 86 of wall 46 defining throat 80 is serrated to provide ridges 88. This series of ridges 88 provide a rough throat wall 86 which creates pockets or regions of relatively low fluid velocity in the flow of light phase blood component through the throat 80. Particulate matter entrained in the flow of light phase material is deposited in the crevices behind the ridges 88 as a result of lower velocity, thereby preventing it from being carried through the apertures 42 and into the upper chamber of assembly 10.

Piston 40 as noted above includes tubular insert 52 which is mounted in annular recess 54 by an interference fit with no air space therearound. When piston 40 is subjected to centrifugal forces the radial outward thrust of hydrostatic force acting on wall 46 is transferred to tubular insert 52 which resists this thrust and will not transmit it to the sealing rings 50 which would cause increase of friction between piston 40 and wall 13 of container 12. Such increase of friction could stall the piston and prevent it from descending. Therefor, this excess friction must be eliminated, which is accomplished as described.

As illustrated in FIG. 2, piston 40 has completed its travel within container 12 and is stopped from further movement in container 12 by stop means 34 and valve means 42 are closed. Also, a portion of the light phase remains above the separated heavy phase and is not utilized as part of the separated light phases.

When operating the separator assembly of the invention herein it is preferred that the assembly be evacuated so that when cannula l8 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 US. Pat. Nos. 2,460,641; 3,469,572; 3,494,352 and 3,779,383. It is important when filling assembly 10 that blood be introduced into container 12 through stopper 16 to obviate the possibility of having blood cells trapped on the top of piston 40 which later will form part of the chamber where the light phase will be collected and would contaminate the light phase with red cells and/or clotted material.

After cannula 18 is withdrawn and container 12 is filled with blood the assembly is placed in a centrifuge and is separated employing moderate centrifugal force which does not cause the piston to move from its initial position. Thereafter the rotational speed of the centrifuge is increased which causes the piston to slide downwardly thereby producing a substantial differential pressure on the diaphragm. The valve means 42 automatically opens and the piston moves downwardly through the light phase with the light phase passing through the throat and valve means. Piston 40 maintains sealing engagement with the inner wall 13 of container 12. The piston completes its movement when it engages stop means 34 and terminates the pressure differential, automatically closing the valve means while the assembly is subjected to centrifugal forces. Thus, diaphragm 44 comprises an impervious barrier between the light phase of blood and the heavy phase of blood when piston 40 is in the position illustrated in FIG. 2. Then centrifugal forces are terminated and the separated blood components are ready for use What is claimed is:

1. A self-contained fluid separator assembly capable of separating blood into its component parts of plasma or serum and 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;

. 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;

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

(1. pressure responsive valve means associated with said piston, said valve means being normally closed when there is a pressure differential on different portions of the valve means below a predetermined value and which automatically opens in response to a pressure differential which is greater than said value 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 surfaces of the container;

e. a throat within said piston leading from the lower surface thereof to said valve means, said throat having walls which are serrated with a series of ridges for trapping unwanted cellular material; and

. mechanical stop means on the container whereby the piston when moving through the light phase will stop a predetermined distance from one ofthe ends of the container followed by termination of the differential pressure which permits the valve means to automatically shift from an open position to a closed position to provide an impervious barrier between the separated light phase and heavy phase of the blood.

2. The self-contained fluid separator of claim 1 wherein said container comprises a tubular body open at each end in which closures formed of elastomeric material are mounted in sealing engagement with the tubular body and a piston disposed adjacent one of said closures.

3. The self-contained fluid separator of claim 1 wherein the piston includes a rigid tubular sleeve mounted in a generally tubular outer body portion formed of rubber and having a plurality of spaced radial ribs on its outer portion for sealing engagement with the inner walls of the container and a diaphragm forming a wall across one end of the generally tubular rubber sleeve and having apertures formed therein which are normally closed but which automatically open when subjected to a substantial pressure differential on each side of the diaphragm.

4. The piston of claim 1 wherein a tubular metal sleeve is mounted in sealing engagement in a complementary annular recess formed in a rubber body portion having an interference fit so that substantially no air space is provided between the walls defining the an nular recess and the inner and outer walls of the rigid tubular member.

5. The self-contained fluid separator of claim 1 wherein the stop means formed on the container is an annular groove interposed between the ends of the container forming an annular rim on the inner surfaces of the container so that said piston is prevented from passing the stop means when subjected to centrifugal forces.

Claims

1. A self-contained fluid separator assembly capable of separating blood into its component parts of plasma or serum and 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 upper portion of the container and having means on its lateral outer surface in sealing engagement with the inner surfaces of the container; d. pressure responsive valve means associated with said piston, said valve means being normally closed when there is a pressure differential on different portions of the valve means below a predetermined value and which automatically opens in response to a pressure differential which is greater than said value 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 surfaces of the container; e. a throat within said piston leading from the lower surface thereof to said valve means, said throat having walls which are serrated with a series of ridges for trapping unwanted cellular material; and f. 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 the differential pressure which permits the valve means to automatically shift from an open position to a closed position to provide an impervious barrier between the separated light phase and heavy phase of the blood.

4. The piston of claim 1 wherein a tubular metal sleeve is mounted in sealing engagement in a complementary annular recess formed in a rubber body portion having an interference fit so that substantially no air space is provided between the walls defining the annular recess and the inner and outer walls of the rigid tubular member.