Plasma separator -- cord stop type

Abstract

A blood collection and separator assembly of the type suitable for use in centrifuging blood to separate the plasma or serum, the light phase, from the cellular portion, the heavy phase. The assembly includes a collection container and a piston disposed therein for sealing off one phase from the other after centrifuging is terminated. The piston is formed having a specific gravity heavier than the light phase of the blood. The piston is slidably disposed in the container with its outer surfaces in sealing contact with the inner surface of the container and is provided with means which, under sufficient centrifugal force, permit the light phase of the blood to pass the piston as the piston moves down through the light phase while retaining sealing engagement with the inner surface of the container. Cord means interconnecting the piston and the top closure of the container stop the piston at a predetermined distance above the bottom of the container whereupon the piston serves as an impervious barrier between the two phases of the blood.

Description

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 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 resilient piston 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 serum/plasma separator assembly including a collection container and a piston slidably disposed in the container, which piston has means permitting, under sufficient centrifugal force, the light phase of the blood to pass the piston as the piston moves through the light phase, means to stop the piston at a predetermined distance above the bottom of the container, and means to seal the piston in the container at the plasma/serum-cellular interface.

It is another object of the invention to provide a serum/plasma separator assembly which is economical to manufacture and can be used in conjunction with standard blood collecting equipment.

DESCRIPTION OF THE DRAWINGS

For a better understanding of the invention, references are made to the drawings which illustrate the preferred embodiment of the invention herein.

FIG. 1 is a sectional, elevational view showing the plasma/serum separator assembly of the present invention and also illustrating a pointed cannula penetrating one of the stoppered ends of the container through which blood is introduced into the container prior to blood separation into its light and heavy phases.

FIG. 2 is a sectional, elevational view similar to the view of FIG. 1, showing the piston stopped at a predetermined distance above the bottom of the container determined by the length of the cord connecting the top closure to the piston, said piston sealing the container at the plasma/serum-cellular interface.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

For a better understanding of the invention herein a description of the drawings of the illustrative embodiments is had with particular reference to FIGS. 1 and 2.

In FIG. 1 the separator assembly 10 comprises a tubular member or container 11 which is sealed at its open ends by closure members 12 and 13. Such tubular member or container is preferably formed of glass but any other suitable material may be employed. Closure members 12 and 13 are preferably made of rubber. Closure 12 is capable of being penetrated by a cannula 14, so that blood can be transferred from a blood source into the container under aseptic conditions. The closures 12 and 13 are preferably made of elastomeric material and should be self-sealing so that when the cannula 14 is removed from the closure 12 there will be no loss of blood.

Disposed in container 11 is piston 15 which is preferably made of an elastomeric material and is made to provide an interference fit within container 11. The piston is formed of material having a specific gravity heavier than the liquid phase of blood. After cannula 14 is removed, the assembly is centrifuged first at a low speed and later at a high speed. Piston 15 is made with sufficient friction to stay up during low speed spin but move downwardly during the high speed spin, down through the plasma/serum phase, 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 elastomeric (preferably rubber) portion of piston 15 has one or more very flexible axially spaced sealing fins 15a encircling the periphery of the piston. These fins contact the inner wall surface 11a of the container 11 in sealing engagement. Such fins preferably extend in a diagonally upward direction so that when centrifugal force is applied to the assembly the fins will yield and permit the liquid phase to pass up around the outer periphery of the piston as the piston descends. When the piston has reached its stopping point just above the interface these fins will reestablish a seal relative to the inner wall 11a of the container 11.

One end of cord 16 is secured to the piston 15 and at the other end to the closure member 13. Such a cord can be a monofilament of plastic or other suitable material. The closure member 13 is provided with a recess 13a so that the cord can be coiled within the recess. The cord is of a predetermined length to stop the piston 15 at a predetermined distance from the bottom of the container. Such a cord is made to position the piston slightly above the serum/plasma-cellular interface.

As illustrated in FIG. 2, piston 15 has completed its travel within container 11 and is stopped from further downward movement in container 11 by the cord stop means and the piston fins 15a are resealed relative to the tube 11. Also 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 14 penetrates closure 12 blood will fill container 11. It is also important when filling the assembly 10 that blood be introduced into container 11 through the stopper 12 mounted on the bottom of the container to obviate the possibility of having blood cells trapped between the piston 15 and stopper 13 which will later separate to form the chamber where the light phase will be collected. Blood cells above piston 15 would contaminate the serum/plasma.

When the centrifuging is terminated, 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

Having described the invention what is claimed is:

1. A separator assembly, capable of separating blood into its component phases of plasma or serum vs cellular portion, comprising:

a. a container having first and second open ends, and adapted to receive blood for subsequent separation into a light phase and a heavy phase;

b. first and second closures sealing both ends of the container, the first of said closures being formed from 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 light phase of the blood and slidably mounted in the container, said piston having means on an outer surface in sealing engagement with an inner surface of the container, said sealing means being constructed and arranged to maintain said piston at a first position adjacent the second of said closures when subjected to a first centrifugal force and to disengage when subjected to a second greater centrifugal force so that when said container is subjected to said first centrifugal force the blood separates into its light phase and heavy phase but the piston stays in said first position and subsequently when said second greater centrifugal force is used the sealing means automatically disengages, the light phase thereby passing around the sealing means enabling the piston to move down through the light phase; and

d. stop means comprising a cord of a predetermined length extending from said second closure to the piston whereby the piston when moving through the light phase will stop a predetermined distance from said first end of the container.

2. The separator of claim 1 wherein the sealing means associated with the said piston comprises flexible sealing fins on the outer surface of the piston in sealing engagement with an inner surface of the container which fins are slanted in an upward direction and are adapted when centrifugal force is applied to the assembly to permit the light phase to pass around the periphery of the piston when the piston moves down through the light phase.