U.S. patent number 3,849,072 [Application Number 05/247,483] was granted by the patent office on 1974-11-19 for plasma separator.
This patent grant is currently assigned to Becton, Dickson and Company. Invention is credited to Waldemar A. Ayres.
United States Patent |
3,849,072 |
Ayres |
November 19, 1974 |
PLASMA SEPARATOR
Abstract
An evacuated tube having both ends closed has a ball type valve
fixedly disposed between the ends for dividing the tube into upper
and lower chambers. The valve is formed and arranged to provide a
passageway between the upper and lower chambers when subjected to a
force of proper intensity and direction. Upon cessation of the
force, the valve closes to provide a separation between the upper
and lower chambers.
Inventors: |
Ayres; Waldemar A. (Rutherford,
NJ) |
Assignee: |
Becton, Dickson and Company
(East Rutherford, NJ)
|
Family
ID: |
22935107 |
Appl.
No.: |
05/247,483 |
Filed: |
April 25, 1972 |
Current U.S.
Class: |
210/789;
137/533.11; 215/355; 494/16; 494/38; 422/918; 210/359; 494/1;
494/37 |
Current CPC
Class: |
B01L
3/5021 (20130101); Y10T 137/791 (20150401) |
Current International
Class: |
B01L
3/14 (20060101); G01n 009/30 (); B01d 021/26 () |
Field of
Search: |
;23/258.5,259,292
;233/1R,2R,26 ;424/101 ;210/136,DIG.23 ;252/349 ;128/2F ;215/47
;137/DIG.4,533.11,539 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Wolk; Morris O.
Assistant Examiner: Hagan; Timothy W.
Attorney, Agent or Firm: Kane, Dalsimer, Kane, Sullivan and
Kurucz
Claims
What is claimed is:
1. A separator device for separating light liquid constituents from
heavier solid constituents of mixtures thereof, comprising:
a hollow elongate member having at least one end adapted for
receiving the mixture;
means for sealing the open ends of said hollow member; and
valve means fixedly positioned in said member for dividing the
member into first and second sealed chambers, said valve means
being normally closed to seal said first chamber and said second
chamber from each other, said valve being responsive to a force in
one direction for opening the valve so that the first and second
chambers are in communication with each other while the force is
applied and said valve closing to interrupt said communication
after the force terminates.
2. A separator device as described in claim 1, wherein at least one
of the means for sealing is penetrable with a cannula.
3. A separator device as described in claim 1, wherein the valve
means comprises:
an elastomeric body having a passageway formed therethrough, said
passageway including an enlarged cavity; and
a sealing element disposed in said cavity.
4. A separator device as described in claim 3, wherein said cavity
is partially defined by a sealing surface formed and arranged for
sealing engagement with said sealing element; and the valve means
additionally includes resilient means for urging said sealing
element into sealing engagement with the sealing surface.
5. A separator device as described in claim 3, wherein the sealing
element comprises a spherical member.
6. A separator device as described in claim 4, wherein the means
for urging the sealing element into sealing engagement comprises,
resilient members formed integrally with said valve, said resilient
members are disposed opposite the sealing surface and partially
define the cavity.
7. A separator device as described in claim 3, wherein the hollow
member is tubular and the passageway includes a cylindrical portion
positioned concentrically with the hollow member, and the valve
means additionally includes an annular groove formed in said valve
concentric with said passageway.
8. A separator device as described in claim 1, wherein the valve
means includes a conical surface, adjacent the first chamber, which
forms a funnel that is in communication with a passageway that
extends from the center of the conical surface through the valve
means.
9. A separator device as described in claim 8, additionally
comprising at least one boss formed on said conical surface.
10. A separator device as described in claim 4, wherein the means
for urging said sealing element into sealing engagement comprises a
thin wall formed integrally with said valve, said wall partially
defining the cavity and having at least one opening formed therein
in communication with the passageway.
11. A separator device as described in claim 9, wherein the hollow
member comprises a glass tube having one closed end and one open
end.
12. A separator device for separating mixed light liquid and heavy
solid constituents of blood and establishing a permanent barrier
between them, including:
a tubular container having at least one open end;
elastomeric closure means for closing the open end and adapted to
be penetrated by a pointed cannula for filling the container with
blood;
elastomeric barrier means fixedly located to separate the container
into upper and lower chambers which are sealed apart from each
other by said barrier means as hereinafter described;
a passageway through the barrier means connecting the upper and
lower chambers;
a wall of the passageway comprising a valve seat;
a resilient restraining means including at least one aperture
therethrough; and
movable valve closure means having a specific gravity greater than
blood and adapted to be forced by centrifugal force from the upper
chamber, down through the connecting passageway, past the valve
seat and against the restraining means, which is maintained in a
stretched elongated condition by the centrifugal force acting on
the valve closure means so that the connecting passageway remains
open and the light blood liquid component flows into the upper
chamber and the heavier blood solid component moves into the lower
chamber, following the completion of which, centrifugation is
stopped and the resilient restraining means urges the movable valve
closure means against the valve seat establishing a permanent seal
between the first and second chambers.
13. The method of separation of blood, contained in an elongated
container, into its lighter liquid and heavier solid constituents
and transferring these constituents into upper and lower chambers
separated by a sealed barrier, fixedly positioned in the container
comprising the steps of:
transferring the heavier blood constituents into the lower chamber
and transferring displaced lighter blood constituents into the
upper chamber by centrifugation;
moving a valve closure member from the upper chamber through a
connecting passageway formed in the barrier and connecting the
upper and lower chambers to a position beyond a valve seat means
formed adjacent said passageway, by using centrifugation;
maintaining said valve closure member in a position beyond said
valve seat by centrifugation; and
moving the valve closure member to a position against the valve
seat means whereby the connecting passageway between the upper and
lower chambers is sealed closed, by terminating the
centrifugation.
14. A separator device for separating constituents of blood into
heavier solid and lighter liquid portions, comprising:
an elongated container;
a centrifugally operated valve means fixedly positioned in said
container for separating the container into two sealed chambers and
for opening and connecting the two chambers while being centrifuged
and for closing and sealing apart the chambers when centrifugation
terminates.
15. A separator device for separating lighter liquid constituents
of blood from the heavier solid constituents thereof which
comprises:
an elongated tubular container having at least one open end;
and
closure means for said open end of said container said closure
means having no surfaces on the inner portion thereof which will
contact liquid contained within said container, presenting a
surface parallel to the plane normal to the longitudinal axis of
said tubular container.
16. As in claim 15, wherein the fluid-contacting surfaces of the
closure means are made of a hydrophobic material.
17. A device as in claim 16, wherein said closure has at least one
air channel in the lower sidewall contacting the interior walls of
said container, said channel having an upper surface which forms an
angle of less than 90.degree. relative to the adjacent container
wall of said tubular container.
18. As in claim 16, wherein the said surfaces are made of a
hydrophobic material.
19. The method of separation of blood into its lighter liquid and
heavier solid constituents which consists of the steps of:
filling with blood an elongated container having at least one open
end sealed by a closure member; and
centrifuging the container with the closure member in sealing
location whereby the blood is centrifuged off the closure member
and is separated into its lighter and heavier constituents, said
closure member having no surface on the inner portion thereof which
will contact liquid contained within said container, presenting a
surface parallel to the plane normal to the longitudinal axis of
said tubular container.
20. The method of separation according to claim 19 wherein said
closure has a fluid-contacting surface adjacent the container inner
wall contacting portion which forms an angle greater than 5.degree.
relative to the adjacent inner wall of the container.
21. The method of separation according to claim 19 wherein said
closure has a skirt portion extending toward the opposite end of
the container and has an edge portion at the lower end of said
skirt which forms an angle less than 120.degree. with the adjacent
inner wall of said container.
22. A method according to claim 19 wherein the closure member has
at least one air channel in the lower sidewall contacting the
interior walls of said container, said channel having an upper
surface which forms an angle of less than 90.degree. relative to
the adjacent container wall of said tubular container.
23. The method of separation of blood into its constituents of
light liquid phase and heavier solid phase and establishing a
permanent barrier between said phases, comprising the steps of:
centrifuging blood contained in an elongated container having first
and second chambers separated by a barrier, said barrier fixedly
positioned in the container having a passageway formed therethrough
so that the light liquid phase of the blood flows to the first
chamber and the heavier solid phase flows to the second chamber;
and
sealing the barrier passageway to provide a permanent barrier
between the light liquid phase and the heavier solid phase of the
blood constituents.
24. A method as described in claim 23, wherein the step of sealing
the barrier passageway includes the step of subjecting a force
activated sealing means to a predetermined force sufficient to
activate the sealing means.
25. A method of separation of blood, contained in an elongated
container, into its constituents of light liquid phase and heavier
solid phase and transferring these phases into first and second
chambers formed in the container by a fixed barrier disposed
between the ends of the container, comprising the steps of:
opening a valve closure means having a specific gravity greater
than the blood, said valve closure means being associated with the
barrier separating the chambers so that the chambers are connected
by the open valve means;
centrifuging the container so that the heavier solid phase is
concentrated in the second chamber and the light liquid phase is
displaced and flows through the open valve means into the first
chamber; and
closing the valve closure means after completion of the separation
of the blood constituents into the light liquid phase and the
heavier solid phase.
26. The method of separating blood into its constituents of light
liquid phase and heavier solid phase and providing a permanent
barrier therebetween, comprising the steps of:
centrifuging an elongated container in which the blood is
contained, said container including first and second chambers
separated by a barrier fixedly positioned in the container and
having a passageway connecting the first and second chambers so
that the heavier solid phase becomes concentrated in the second
chamber and the light liquid phase is displaced and flows through
the passageway into the first chamber; and
sealing the passageway to provide a permanent barrier between the
first and second chambers by moving a closure member from the first
chamber into sealing engagement with the passageway.
27. A separator device for separating blood into its constituents
of light liquid phase and heavier solid phase and for establishing
a permanent barrier between the phases, including:
a tubular container closed at both ends containing the blood to be
separated;
barrier means fixedly located for separating the container into
first and second chambers which are sealed apart from each other as
hereinafter described;
a passageway through the barrier means connecting the first and
second chambers; and
force activated sealing means for sealing the passageway through
the barrier means upon application of a predetermined force.
28. A separator device as described in claim 27, wherein the
barrier means is formed of an elastomeric material and the sealing
means comprises a closure member having specific gravity greater
than blood and adapted to be forced by a predetermined centrifugal
force from the first chamber into the passageway to thereby
permanently seal and separate the first and second chambers.
29. A separator device for separating mixed light liquid phase and
heavy solid phase constituents of blood and establishing a
permanent barrier between said phases, including:
a tubular container closed at both ends containing the blood to be
separated;
elastomeric barrier means fixedly located to separate the container
into first and second chambers which are sealed apart from each
other by said barrier as hereinafter described;
a passageway through the barrier means connecting the first and
second chambers;
a wall of the passageway comprising a valve seat; and
movable valve closure means within the container having a specific
gravity greater than blood for coupling with the valve seat to seal
off the passageway and provide a permanent barrier seal isolating
the first and second chambers.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to separators and more particularly
to a device for separating blood plasma from cellular material.
2. Description of the Prior Art
With the development of modern pathological laboratories, it has
become the common practice to send blood samples to a centralized
laboratory facility for analysis. The normal procedure requires
that the patient's blood sample be taken at a doctor's office or a
clinic and thereafter mailed in a proper container to a centrally
located laboratory to be tested. In many instances, it is desirable
that the cellular material contained in a blood sample be separated
from the blood plasma shortly after the sample is taken from the
patient and prior to mailing. Centrifuging has become the accepted
method for separation of the suspended cellular material from the
blood plasma.
For proper testing of the blood sample, it is essential that pure
blood plasma be made available at the laboratory and therefore the
plasma must be separated from the cellular material in such a
manner so as to prevent remixing of the blood constituents during
mailing. Heretofore, the blood plasma was removed from the specimen
tube after the blood was centrifuged to prevent the remixing of the
plasma and the blood cells. A conventional syringe was used to draw
the plasma from the specimen tube after which the plasma was
deposited in a second container for mailing separately from the
cellular material, which remained in the original container.
The use of a conventional syringe for removal of the blood plasma
was extremely inefficient and time consuming since the technician
had to be careful not to disturb the cellular material which
remained in the bottom of the specimen tube. The blood sample was
subject to contamination by contaminants present in the syringe or
the second container. Another undesirable aspect of the system was
that two containers were required for mailing the blood sample and
on occasion, the containers would become separated and
identification problems resulted.
Various devices have been developed for drawing blood plasma from
the specimen tube and one such is taught by U.S. Pat. No.
3,586,064. These devices all suffered from some form of shortcoming
in that they were either complicated and expensive or required
considerable time for separation of the plasma. When considering
the large number of blood samples processed by modern medical
facilities, the time factor has become an extremely critical factor
in the overall cost of blood tests.
SUMMARY OF THE INVENTION
The present invention contemplates an evacuated tube having closed
ends and a valve fixedly disposed between the ends to divide the
tube into upper and lower chambers. The valve includes an
elastomeric body having a centrally located cylindrical opening
with a cone-shaped valve seat formed around a lower end of the
opening. A ball, preferably of stainless steel, is disposed
adjacent the cone-shaped seat and is retained against the seat by
elastomeric members formed as an integral part of the valve
body.
In a first embodiment, a tube is used having an opening at each
end, said openings being closed with penetrable stoppers. The tube
is evacuated through the lower end so that the lower chamber is
evacuated first. A pressure differential is developed across the
ball which causes the elastomeric members to be stretched
downwardly and the ball to move down and away from the valve seat.
When the ball is unseated, the upper and lower chambers come into
communication so that the upper chamber is also evacuated.
The tube is filled with blood by puncturing the stopper disposed in
the upper end of the tube and the vacuum in the upper chamber draws
blood into the tube in a manner well known to the art. As the upper
chamber is filled with blood, a pressure differential is developed
across the ball causing the ball to exert a force downwardly on the
elastomeric members thereby causing the ball to be unseated and the
blood to flow into the evacuated lower chamber. Thus, the entire
container is filled with a blood sample.
Upon subsequent centrifuging, the heavy ball is forced against the
elastomeric members which stretch causing the ball to be unseated
and a passage to be formed communicating the upper and lower
chambers so that the heavier blood cells flow in a downwardly
direction causing the lighter plasma to be displaced into the upper
chamber of the tube.
When centrifuging is discontinued, the elastomeric members again
force the ball into a seated position so that the ball provides a
seal between the cellular material and the plasma. The seal is
tight enough so that the tube may be mailed to a laboratory without
fear of the plasma being remixed with the cellular material.
Heretofore, when centrifuging a tubular container of blood to
separate the cellular material from the plasma, it has been a
frequent practice to remove the stopper at the upper end of the
container prior to centifuging. This is done because very
frequently if it is not done drops or other small portions of the
blood containing cellular material hang onto the stopper or stay in
crevices between portions of the rubber stopper and the glass
container despite the centrifugal force applied. Then later, after
centrifugation is stopped, and the stopper is removed for decanting
the plasma, any such cellular material retained at the glass wall
may contaminate the plasma as the plasma is poured out over the
retained cellular material. One object of this invention is to
provide an improved container which can be kept sealed while being
centrifuged, without removal of the stopper, and which later can be
inverted, shaken, handled roughly, or sent through the mail from a
doctor's office to an analytical laboratory, without any of the red
cells contaminating the plasma. To accomplish this, it has been
necessary to invent improvements for the upper stopper also to
eliminate retention of any blood containing cellular material, as
will be shown and described later.
In a second embodiment, the component and assembly costs are
reduced by the use of a single ended tube and a valve, having a
slightly different structure. During assembly, a stainless steel
ball is merely deposited in the upper chamber and is prevented from
seating by the use of bosses which space the ball from the
elastomeric body which ensures an opening connecting passageway
between the upper and lower chambers prior to centrifuging so that
both the upper and lower chambers may be evacuated and filled with
blood from the top end. The blood flows unimpeded from the upper to
the lower chamber through the passageway while obtaining a blood
sample from a patient.
Upon subsequent centrifuging, the heavy stainless steel ball is
driven by centrifugal force through the passageway and beyond the
valve seat into cavity within the elastomeric body thereby
completing assembly of the valve. The ball displaces an elastomeric
member and remains in an unseated position until centrifuging is
terminated after which the said elastomeric member pulls the ball
into a seated position to separate the upper and lower chambers in
a manner substantially identical to that of the first
embodiment.
The primary objective of the present invention is to provide a
device that may be used to collect a blood sample from a patient,
separate the blood sample into its constituents, and maintain the
constituents separate while the sample is mailed to a
laboratory.
Another objective of the present invention is to provide a blood
plasma separator that is less expensive than those heretofore
provided.
Another objective of the present invention is to provide a blood
plasma separator that simplifies the procedure required for the
separation and shipment of a blood sample.
Another objective of the present invention is to provide an
improved closure for a blood container whereby all the cellular
material of the blood will be removed by centrifugation to prevent
later contamination of the plasma with cellular material, and the
usual necessity of removing the stopper prior to centrifuging is
eliminated.
The foregoing objectives and advantages of the invention will
appear more fully hereinafter from a consideration of the detailed
description which follows, taken together with the accompanying
drawings, wherein two embodiments of the invention are illustrated
by way of example. It is to be expressly understood, however, that
the drawings are for illustrative purposes only and are not to be
considered as defining the limits of the invention.
DESCRIPTION OF THE DRAWINGS
FIG. 1 is a vertical section of a first embodiment of the present
invention.
FIG. 2 is a view of the present invention taken along line 2--2 of
FIG. 1.
FIG. 3 is a vertical section of a second embodiment of the present
invention.
FIG. 4 is a view taken along line 4--4 of FIG. 3.
FIG. 5 is a view taken along line 5--5 of FIG. 3.
FIG. 6 is a plan view looking up at the bottom of the stopper 14 of
FIG. 1.
FIG. 7 is a vertical section of the stopper 14 of FIG. 1.
FIG. 8 is a vertical section of a common prior art stopper shown
for comparison.
DESCRIPTION OF THE INVENTION
The present invention will be described as a plasma separator;
however, it is to be understood that the invention could be used
for the separation of material suspended in a liquid, for
separating emulsions or for separating fluid constituents having
different specific gravities.
Referring to FIG. 1, there is shown a glass tube 10, having
openings at each end which are closed by stoppers 12 and 14.
Stoppers 12 and 14 are preferably resilient and penetrable by a
cannula for purposes of evacuating or filling the tube. Tube 10 has
a constriction 16 in the form of a reduced diameter formed at a
predetermined position between the ends. The constriction is used
to properly position a ball-valve 18 which is disposed within tube
10 to divide the tube into an upper chamber 11 and a lower chamber
13.
It is to be understood that the valve could be positioned in many
ways well known in the art. As an example, the fit between the
valve and the inside diameter of the tube may be of sufficient
tightness so that once the valve is forced into a particular
position during assembly the frictional forces between the valve
and the tube will retain the valve at the desired position during
its life including periods of centrifuging.
The valve is positioned so that it is above an interface 17 that is
formed between the plasma and the cellular material of the blood
after centrifuging. This is essential so that the plasma remains
free of cellular material during mailing of the sample.
Valve 18 is made of an elastomeric material such as a soft inert
rubber or plastic material. A ball 20 is positioned within valve 18
and is formed of one of a variety of materials having a specific
gravity greater than that of blood plasma which is approximately
1.03. The material from which the ball is manufactured must be
chemically inert with blood and the preferred materials are glass,
ceramic or stainless steel.
Valve 18 has a conical-shaped upper surface 22 forming a funnel
that is in communication with a cylindrical opening 24 formed in
the center of the valve and extending therethrough. The upper
periphery of surface 22 terminates in a feather edge which seals
against the inner surface of tube 10 to facilitate unrestricted
flow of cellular material through the valve during centrifuging and
to prevent cellular material from being caught between the valve
and the inner surface of the tube. An annular opening 26 is formed
in the lower side of valve 18 to reduce the effect of variations of
internal diameter of the glass tube 10 upon the diameter of opening
24.
Valve 18 has an internal cavity 28 defined by conical surface 30, a
cylindrical surface 31 and the inner surface of spokes 32 which are
connected at the center of valve 18 as shown most clearly in FIG.
2.
Ball 20 is inserted into valve 18 by pushing the ball through the
opening 24 prior to the valve being inserted into tube 10. The ball
is disposed within cavity 28 and is supported by spokes 32 which
presses the ball against conical surface 30 to seal opening 24.
When a downward force is exerted on ball 20, spokes 32 stretch
enabling ball 20 to be displaced in a downwardly direction and
unseated from surface 30 thereby providing a passage between the
upper chamber and lower chamber. This force may be exerted by a
pressure differential between the two chambers or by centrifuging
the tube.
After the valve is inserted in tube 10, stoppers 12 and 14 are
placed in their respective ends and the tube is evacuated in a
manner well known in the art. Evacuation of the lower chamber
causes a pressure differential across ball 20 thereby causing the
ball to be displaced downwardly opening a passageway to the upper
chamber so that it too is evacuated.
When the tube is to be filled with a blood sample, stopper 14 is
punctured with a pointed cannula connected with a patient so that
blood is drawn into the evacuated upper chamber. As the upper
chamber fills with blood, a pressure differential is again created
across ball 20 causing it to be displaced downwardly and be
unseated from surface 30. The unseating of ball 20 allows blood to
flow into the lower chamber so that the entire tube is filled with
the blood sample.
In order to separate the plasma from cellular material, the entire
device is centrifuged so that centrifugal force is exerted in the
direction of stopper 12. Since ball 20 has a specific gravity
greater than blood, the ball is urged in a downwardly direction
stretching spokes 32 and unseating the ball so that a passage is
formed between the upper and lower chambers. The heavier red blood
cells flow in a downwardly direction displacing the plasma in the
lower chamber so that it flows in an upwardly direction into the
upper chamber until a plasma-cellular material interface 17 is
established below valve 18. When interface 17 is established,
centrifuging is stopped and spokes 32 contract causing ball 20 to
be seated against conical surface 30 thereby creating a permanent
separation between the upper and lower chambers. A seal created by
the ball and conical surface 30 is sufficiently tight so that the
tube may thereafter be shipped by mail to a laboratory without the
cellular material being remixed with the plasma.
FIGS. 1, 3, 6 and 7 show an improved form of upper stopper
especially designed to eliminate the usual necessity of removing
the upper stopper prior to centrifugation to avoid the possibility
that blood droplets or other blood portions containing red cells
will remain on the stopper or between the glass tube and the
stopper, as discussed in greater detail above. Study of such usual
malfunctions of prior art stoppers shows that blood with red cells
at 64 in FIG. 8, frequently remains on horizontal portions of the
stoppers as at 60, 61 and 62, and/or in small crevices where the
rubber of the stopper forms an acute angle relative to the adjacent
glass wall 65 of the tubular container, as at 63, even though
substantial centrifugal force is employed to separate the red cells
from the plasma. The stoppers 14 and 36 are designed to eliminate
this difficulty while at the same time enabling the blood
containers to be kept stoppered throughout centrifuging and
subsequent handling prior to chemical analysis, thus keeping out
dirt, air born bacteria, spores, etc..
FIG. 8 shows a very well known type of prior-art stopper inserted
in its glass blood container, shown for analysis and comparison.
The roof portion, which is at 90.degree. to the long axis of the
blood container and to the direction of the centrifugal force,
frequently has one or more drops of blood, as shown at 64, still
remaining wetting this horizontal surface. Similarly, surfaces 61
and 62, at 90.degree. relative to the tube axis, are surfaces
having a high retentivity for droplets. Blood has high wetting
characteristics relative to rubber surfaces. In FIGS. 1, 3 and 7
note that these 90.degree. surfaces have been eliminated and have
been replaced with diagonal surfaces, relative to the tube axis, so
that provision is made for "run-off" of the blood droplets,
comparable to rain on a slanted roof. This is shown by the slanted
surfaces 66, 67 and 68 in FIG. 7.
The FIG. 6 is a bottom view of FIG. 7 and shows three air channels,
each also having a diagonal surface 68 for "run-off" of blood
droplets. These channels aid in the evacuation of the tube 34, FIG.
3, where a plurality of such tubes may have their stoppers
partially inserted, but not far enough to occlude the passageways,
then be placed in an evacuating enclosure, and then have the
stoppers pushed all the way into the glass tubes thus sealing in
the vacuum.
Note that the stopper in FIG. 3 is shown rotated slightly, as
compared with FIGS. 6 and 7, but the design is the same.
As an optional feature, the blood contacting surfaces of this
improved stopper may be coated with a hydrophobic material, such as
a wax, teflon or other suitable fluorocarbon, AC polyethylene
available from Allied Chemical Corp., or any other preferred
material which reduces the wetting action relative to blood and
thus will increase the "run-off" action of blood while being
centrifuged.
An additional design feature of this improved stopper is to provide
a tapered or thin skirt portion on the bottom of the stopper, as at
67, FIG. 7, preferably terminating with a sharp edge, its cross
section having a small included angle. The function of this feature
is that when a droplet of blood "runs off" any of the diagonal or
vertical surfaces down to the edge of this skirt under the
influence of centrifugal force, this small included angle,
constituting a sharp edge (69 and 70 in FIG. 7), substantially
reduces the wetted adherence of the drop, relative to the mass of
the drop, so that the centrifugal force more readily and more
completely causes the droplet to be spun off this sharp edge.
Minor modifications may be made to the above-described device that
fall within the inventive concepts of the invention. Ball 20 may be
replaced with an element having a conical surface juxaposed with
surface 30.
The previously described device has certain characteristics that
may be somewhat undesirable. The preassembled valve is normally
closed when it is in the tube and opens only when a downwardly
directed force is exerted on the ball. Thus, it is essential that a
double ended tube be utilized so that the chambers may be evacuated
from one end and filled with blood from the other end. The need for
a double ended tube necessitates the use of a second stopper whichs
adds to the overall cost of the device and also increases the
assembly cost. The assembly cost is also increased by the necessity
that the ball be placed within the valve prior to insertion of the
valve in tube 10. A second embodiment shown in FIG. 3 is provided
to overcome these somewhat undesirable features.
The device shown in FIG. 3 has an opening connecting the upper and
lower chambers so that both chambers may be evacuated and filled
with the patient's blood from one end of the device. A standard
single ended glass tube 34 has a penetrable stopper 36 inserted in
the end. A valve 38 is fixedly disposed approximately midway the
tube 34 and may be positioned by the use of an annular depression
such as in the embodiment shown in FIG. 1 or by the use of a tight
frictional fit as previously described.
Valve 38 has a conical upper surface 40 having an opening 42 formed
in the center thereof which is in communication with a cylindrical
opening 43 extending through the valve. Three raised bosses 44 are
formed on the conical surface 40 and are equally spaced around the
surface. An annular opening 46 is formed in the lower surface of
valve 38 to compensate for variations in the inside diameter of
tube 34. A cavity 48 is formed in valve 38 and is defined by a
conical surface 50, a cylindrical surface 51 and the inner surface
52 of a thin wall 54 formed on the bottom of valve 38. Wall 54 has
three openings 56 formed therein for communicating cavity 48 with
the lower chamber of the tube as shown most clearly in FIG. 4.
During assembly of the device shown in FIG. 3, valve 38 is
positioned within tube 34 and a ball 58, preferably of stainless
steel, is placed in the upper chamber. Anti-coagulant may be added
to the tube and thereafter penetrable stopper 36 is pushed into
position in the end of the tube 34. The tube is then evacuated in
any suitable manner well known in the art. Both the upper and lower
chambers are evacuated because ball 58 rests on bosses 44 rather
than on surface 40. Bosses 44 hold ball 58 in spaced relationship
to surface 40 so that an opening is formed between the ball and
surface 40 to allow for evacuation of both chambers through one
end. The ball has a diameter somewhat larger than opening 42 and
therefore does not pass through opening 42 when placed into the
upper chamber.
A double pointed cannula is inserted into a patient and the second
end inserted into stopper 36 is used to fill the upper and lower
chambers with blood. Both chambers are filled becauses bosses 44
prevent the ball from seating on the valve. After the tube is
filled with blood, it is centifuged. Because of the high specific
gravity of the ball, it is driven in a downwardly direction by the
centrifugal force through the openings 42 and 43 in valve 38. The
ball thereafter remains in cavity 48 of the valve. During
centrifuging, the ball continues to press against wall 54 causing
the wall to deflect, in a downwardly direction, a sufficient
distance so that the ball does not seat against conical surface 50.
When the ball is not seated, an interconnecting passage between the
upper and lower chambers is provided so that the heavier blood
cells may flow in a downwardly direction and displace plasma which
flows in an upwardly direction through the valve. When the
centrifuging is completed, the elasticity of the thin wall 54 again
becomes a dominant force pushing ball 58 into a seated position
against conical surface 50 thereby sealing the plasma in the upper
chamber from the cellular material contained in the lower
chamber.
Thus, the embodiment shown in FIG. 3 reduces the component cost of
the device by the elimination of a second stopper and also reduces
assembly costs since the ball need not be inserted into the valve
but merely may be dropped into the upper chamber, after which
centrifugal force drives the ball into its proper position. Since
ball 58 initially rests on bosses 44 and does not form a seal with
surface 40, both chambers may be evacuated from one end of the tube
and both chambers may also be filled with blood from the same end
of the tube.
Thus, the present invention provides an inexpensive and
uncomplicated device for taking blood samples, for separating the
blood into its constituents and for shipping the separated
constituents to a laboratory for analysis without the need for
placing the constituents in separate containers.
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