U.S. patent number 3,559,880 [Application Number 04/795,934] was granted by the patent office on 1971-02-02 for apparatus for blood plasma separation.
This patent grant is currently assigned to The Green Cross Corporation. Invention is credited to Ryoichi Naito, Osamu Yamaji.
United States Patent |
3,559,880 |
Naito , et al. |
February 2, 1971 |
APPARATUS FOR BLOOD PLASMA SEPARATION
Abstract
An apparatus for centrifugally separating blood plasma from red
blood cells, said apparatus being adapted for use with a blood bag
set composed of a pair of mother bags and a daughter bag
communicating therewith, said apparatus comprising a blood bag
receiving box of generally inverted V-shape cross section having a
pair of bottom plates hinged for upward movements, rotary drum,
flywheel of larger inertia than that of the drum and a mechanism
operable, after completion of blood plasma separation within said
mother bags and after switching off of the power source of the
apparatus, to upwardly urge the bottom plates of the blood bag box
against the cover thereof by virtue of the difference in inertial
rotation between the drum and the flywheel to thereby automatically
squeeze the separated fluid of blood plasma out of the mother bags
into the daughter bag.
Inventors: |
Naito; Ryoichi (Osaka,
JA), Yamaji; Osamu (Osaka, JA) |
Assignee: |
The Green Cross Corporation
(Osaka, JA)
|
Family
ID: |
33250864 |
Appl.
No.: |
04/795,934 |
Filed: |
February 3, 1969 |
Foreign Application Priority Data
|
|
|
|
|
Oct 3, 1968 [JA] |
|
|
43/86264 |
|
Current U.S.
Class: |
494/21 |
Current CPC
Class: |
B04B
5/0428 (20130101) |
Current International
Class: |
B04B
5/00 (20060101); B04B 5/04 (20060101); B04b
001/00 (); B04b 009/14 () |
Field of
Search: |
;233/1,26,17,27,28 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Price; William I.
Claims
We claim:
1. An apparatus for separating fluid of blood plasma from red blood
cells, said apparatus being adapted for use with a blood bag set
composed of a pair of mother bags and a daughter bag communicated
therewith, said apparatus comprising a box of substantially
inverted V-shape for receiving said blood bag set in such a manner
that said mother bags extend outwardly downwardly in diametrally
opposite directions and said daughter bag hangs down, said box
having bottom plates hinged for upward movement, a main rotary body
on which said box is mounted, a flywheel of larger inertia
rotatably mounted onto said rotary body for free rotation within a
predetermined range, substantially vertical levers pivotably
connected to said rotary body and having their upper ends in
contact with said bottom plates of said blood bag box horizontal
levers pivotably mounted at one ends onto said flywheel and having
recesses therein, said vertical levers having their lower ends
received in said recesses in said horizontal levers, respectively,
tension springs connected to the other end of said horizontal
levers for biasing same inwardly toward said rotary body, said
horizontal levers having shoulders in the inner faces thereof next
to said recesses toward said the other ends whereby, upon outward
displacements of said horizontal levers due to centrifugal force,
said lower ends of said vertical levers are brought into
engagements with said shoulders of said horizontal levers.
Description
BACKGROUND OF THE INVENTION
Field of the Invention
This invention relates to an apparatus for blood plasma separation,
and more particularly, to an apparatus for centrifugally separating
blood into red blood cells and fluid of plasma.
Blood comprises corpuscles mostly of red blood cells and fluid of
plasma rich in proteins. Once blood is taken out from the body, red
blood cells hardly survive long, whereas plasma can be preserved
for a long period of time and can further be fractionated and
purified into several useful preparations according to the
respective specific properties of each protein fraction. It is a
well-known fact in physiology that plasma proteins are replenished
in the body within a short time after blood donation but red blood
cells require a rather long time for their reconstitution. From the
viewpoint of donor's health, therefore, it is advisable that red
blood cells be separated from liquid of plasma and returned back
into the circulation of the donor.
The series of procedures; collection of blood from vein of a donor
into a container with anticoagulant, separation of plasma,
resuspension of red blood cells and giving back of the suspension
into the vein of the donor, are called as "plasmapheresis" in this
field and becoming commonner in practice.
For this reason, a variety of methods have already been developed
for separation of blood plasma. They are roughly classified into
following two categories:
1. A method using glass bottle; and
2. A method using flexible and soft blood bag.
1. Glass bottle method
A glass bottle of 500 ml. capacity and containing 10 percent
aqueous sodium citrate solution is sterilized and used as a blood
container for bleeding, into which blood is collected from the vein
of a donor. After separation of red blood cells and plasma by means
of centrifugal separator, the supernate is taken out through a fine
tubing, leaving the packed red blood cells at the lower part of the
bottle. Normal saline or other equivalent solution is added to
suspend the red blood cells and return the suspension to the vein
of the donor.
2. Flexible blood bag method
A blood bag such as one shown in FIG. 1 is usually used. The blood
bag is made of polyvinyl chloride or other qualitatively equivalent
material for flexibility of the bag. The bag is composed of a
mother bag 1, a daughter bag 2 and a tubing 3 interconnecting them.
The mother bag is added with an anticoagulant solution such as
sodium citrate solution and is sterilized. Venous blood is
collected in the mother bag through a short tubing 4 connecting a
venous needle and the mother bag. The bag is then mounted on a
centrifuge and rotated thereby with the tubing 3 collapsibly closed
and with an outlet 5 disposed close to the rotatory shaft whereby
most of the red blood cells are gathered at the bottom 6 of the
mother bag. After the centrifugation and stop of the centrifuge,
the mother bag is placed between and pressed with two hinged
transparent boards for squeezing the plasma out of the mother bag
through the outlet 5 and the tubing 3 into the daughter bag 2. The
tubing is cut to separate the daughter bag containing the plasma
from the mother bag. The latter is supplied with normal saline to
suspend the packed red blood cells and reinfuse to the donor's
vein. It is generally accepted that, as compared with the glass
bottle method, this blood bag method maintains better sterility
during the procedures in addition to its causing less damages to
the red blood cells because of flexibility of bags and connection
of a mother bag and a daughter bag through tubing.
Whichever method may be employed, 20 to 30 minutes are required for
the procedures in which the blood collected from a donor is
subjected to centrifugal separation of plasma by use of a
centrifuge which has operative acceleration and deceleration stages
in rotational speed. Thus, the donor suffers from a mental pain in
having a long wait and from a physical pain in holding a bleeding
needle in the vein for a long time.
SUMMARY OF THE INVENTION
It is, therefore, a primary object of the present invention to
provide an improved blood plasma separation apparatus which is
designed to be used with a flexible blood bag set consisting of
mother and daughter bags and containing blood collected from donors
and which is operable to centrifugally separate the blood into red
blood cells and fluid of plasma and, after switch-off of the power
source of the apparatus, automatically press the mother bags for
squeezing out the separated fluid of plasma therefrom during
inertial rotation of the apparatus thereby to greatly shorten the
time required for transfer of plasma.
According to the present invention, there is provided an apparatus
for separating fluid of blood plasma from red blood cells, said
apparatus being adapted for use with a blood bag set composed of a
pair of mother bags and a daughter bag communicated therewith, said
apparatus comprising a box of substantially inverted V-shape for
receiving said blood bag set in such a manner that said mother bags
extend outwardly downwardly in diametrically opposite directions
and said daughter bag hangs down, said box having bottom plates
hinged for upward movement, a main rotary body on which said box is
mounted, a flywheel of larger inertia rotatably mounted onto said
rotary body for free rotation within a predetermined range,
substantially vertical levers pivotably connected to said rotary
body and having their upper ends in contact with said bottom plates
of said blood bag box, horizontal levers pivotably mounted at one
ends onto said flywheel and having recesses therein, said vertical
levers having their lower ends received in said recesses in said
horizontal levers, respectively, tension springs connected to the
other end of said horizontal levers for biasing same inwardly
toward said rotary body, said horizontal levers having shoulders in
the inner faces thereof next to said recesses toward said the other
ends whereby, upon outward displacement of said horizontal levers
due to centrifugal force, said lower ends of said vertical levers
are brought into engagement with said shoulders of said horizontal
levers.
BRIEF DESCRIPTION OF THE DRAWINGS
Other objects and features of the present invention will be made
apparent from the following description in conjunction with the
accompanying drawings, and in which:
FIG. 1 schematically illustrates, in perspective view, a commonly
used prior art blood bag set;
FIG. 2 is a view similar to FIG. 1 but illustrating a blood bag set
according to the present invention;
FIG. 3 is a vertical sectional view of an embodiment of the blood
plasma separation apparatus according to the present invention;
FIG. 4 is a plan view of a rotary section of the apparatus shown in
FIG. 1 with a part removed away;
FIG. 5 is a perspective view of a frame for holding a blood bag
receiving box;
FIG. 5A is a cross-sectional view taken along line VA-VA in FIG.
5;
FIG. 5B is a cross-sectional view taken along line VB-VB in FIG.
5;
FIG. 6 is a perspective view of the blood bag receiving box;
FIG. 7 is a fragmentary perspective view showing a cover of the
blood bag receiving box in FIG. 6 and means for fastening the
cover, with parts removed and cut away;
FIG. 8 illustrates in plan view engagement between vertical and
horizontal levers;
FIG. 9 is a view similar to FIG. 8 but illustrating the levers in
slightly different position;
FIG. 10 illustrates in vertical section the levers in the position
shown in FIG. 9;
FIG. 11 is a view similar to FIG. 9 but illustrating the levers in
further different position; and
FIG. 12 illustrates in vertical section the levers in the position
shown in FIG. 11.
DESCRIPTION OF PREFERRED EMBODIMENT
Referring now to FIG. 2, the blood bag set according to the present
invention is indicated generally at 10 and comprises a pair of
mother bags 11, 11' communicating with each other through an
intermediate or bridge portion 11a interconnecting the mother bags
at their tops, a small daughter bag 12 disposed between the mother
bags and a pair of tubings 13, 13' connecting the daughter bag 12
to the bridge portion 11a for communicating the interiors of the
mother bags with that of the daughter bag. The mother bags 11, 11'
are connected with short tubings 14, 14' adapted to be connected
with bleeding needles through appropriate tubings, respectively.
Formed centrally of the bridge portion 11a are openings in the top
and the bottom walls of the bridge portion. The peripheral edges of
the openings are heat-sealed together. A ring 15 is fitted to the
sealed edge of the opening. The blood bag set 10 is made of
polyvinyl chloride or the like material. Preferably, the material
is transparent or semitransparent for enabling one to observe the
interiors of the bags from the outside thereof. Also, the material
is required to withstand a steam pressure sterilization at
121.degree. C. for 30 minutes. The whole bag set is subjected to a
heat sterilization after putting of an anticoagulant solution, such
as aqueous solution of sodium citrate or heparin, of proper
concentration into the mother bags. For collection of blood, all
bags of a set are placed in a closed container, whose inner
pressure is then reduced. A negative atmospheric pressure sucks the
blood from the vein of a donor through a bleeding needle and one of
the short tubings 14, 14' into the mother bags. During the
bleeding, the tubings 13, 13' are pressed and closed with a clamp
to prevent the blood from flowing into the daughter bag 12. The
blood collected in the mother bags 11, 11' is well mixed with the
anticoagulant solution and is divided equally into two masses to
balance the mother bags.
A description will next be made, with reference to FIGS. 3 to 7, of
a centrifugal machine according to the present invention and
adapted to be used with the blood bag set 10 shown in FIG. 2.
Referring first to FIG. 3, there is shown an embodiment of the
centrifugal machine generally designated at 20. The machine
includes a base 21 housing therein an electric motor (not shown)
having its shaft 22 projecting upwardly. Onto the top of the base
21 is secured a generally cylindrical casing 23 having an open top.
An annular fitting 24 is mounted by means of bolts and nuts on the
casing 23 around the opening in the top thereof. Fitted to the
annular fitting 24 is an annular shock-absorbing air-tube 25 over
which is detachably mounted a cover 26 having a bearing 27 mounted
in a central aperture in the cover. The bearing 27 is adapted for
rotatably receiving therein a shaft 28 for the purpose which will
be described later.
Within the casing 23 is disposed a bottomed drum 30 having a boss
31 extending downwardly from the bottom through which the motor
shaft 22 extends upwardly into the interior of the drum. The latter
is fastened to the motor shaft by means of a nut 29. The drum 30
has, at the intermediate portion of the height, a radially
outwardly projecting annular flange which is cut at diametrically
opposite sides to form two substantially arcuate flanges 32, 32'
and two straight and parallel surface 33, 33' as shown in FIG. 4.
The distance from the center of the drum 30 to each of the surfaces
33, 33' is the same as the outer radius of the drum as measured at
the portion just above the flanges 32, 32'. The drum 30 is also
provided with two pairs of radial projections 34 and 34' . The
arcuate flanges are respectively formed, at central portions, with
notches 32a, 32'a having their bottoms extending outwardly
downwardly, the center of the notch in each of the flanges 32, 32'
being in vertical alignment with the center of each pair of the
radial projections.
A substantially rectangular frame 35 is secured to the drum 30 by
means of a ring 36 threadably engaging the upper portion of the
drum. More specifically, the frame 35 includes two longitudinal
bars 35A, 35A', lateral bars 35B, 35B' interconnecting the bars
35A, 35A' at the opposite ends thereof and a lateral bridge 35C
interconnecting the longitudinal bars at the central portion of the
frame 35 as best seen in FIG. 5. The bridge 35C is coplanar at the
top surface, with the top surfaces of the bars 35A, 35A', 35B, 35B'
but is substantially one half in thickness the bars, as shown in
FIGS. 5-A and 5-B. The bridge 35C is formed therein with an annular
opening whose diameter is the same as the distance between the
inner surfaces of the longitudinal bars 35A, 35A', which distance
is, in turn, the same as or slightly larger than the diameter of
the drum 30 as measured at the portion just above the flanges 32,
32'. It will, thus, be apparent that, when the frame 35 is mounted
over the drum 30, the annular opening in the bridge 35C of the
frame 35 snugly receives the upper portion of the drum with the
bottom surface of the bridge in contact with the upper shoulders of
the arcuate flanges 32, 32' and with the inner surfaces of the
frame bars 35A, 35A' at longitudinally intermediate portions of the
surfaces tightly contacting the opposite parallel surfaces 33, 33'
of the drum 30. When the ring 36 is fastened downwardly on the drum
30, therefore, the frame 35 is rigidly connected to the drum for
rotation therewith.
The frame 35 further includes a pair of ears 35D, 35D' connected to
the outer surfaces of the longitudinal bars 35A, 35A' centrally
thereof. Studs 35E, 35E' having enlarged heads are rigidly planted
in the ears 35D, 35D' for the purpose described later. In addition,
the bridge 35C of the frame 35 has downwardly outwardly inclined
outer surfaces and is also provided with a pair of notches 35C',
35C" in the inclined outer surfaces centrally thereof,
respectively. The bottom surfaces of the notches 35C', 35C" incline
downwardly inwardly, as best seen in FIG. 5-B. Thus, it will be
appreciated that, when the frame 35 is mounted in position on the
drum 30, one of the notches in the arcuate flanges 32, 32' and one
of the notches 35C', 35C" in the frame bridge 35C are in vertical
alignment and the inclined bottom surfaces of the vertically
aligned notches cooperate to define two recesses in the combined
drum 30 and frame 35 for the purpose described hereinafter.
The pairs of projections 34, 34' have pins 36, 36', respectively,
on which two-armed generally vertical levers 37, 37' are pivotably
mounted at substantially intermediate points of their lengths. The
levers 37, 37' are respectively provided with rollers 38, 38' at
their upper ends. The length of each of the lever 37, 37' between
its pivotal axis and the upper end is dimensioned such that the
upper roller 38 or 38' is received by and rests in the recess
defined by the inclined bottom surfaces of the notches in the
arcuate flange 32 or 32' and in the bridge 35C of the frame 35.
A flywheel 40 is mounted around the boss 31 of the drum 30.
Specifically, the wheel 40 has a central boss 41 which extends
upwardly from the bottom of the wheel 40 and which surrounds a unit
of rotary and thrust bearing 42 disposed around the drum boss 31. A
nut 42a is disposed around the drum boss 31 under the bearing unit
42 for rotatably supporting the flywheel assembly on the drum
30.
A pair of elongated arcuate horizontal levers 43, 43' are disposed
radially outwardly of the vertical levers 37, 37', respectively,
and have their one ends pivotally connected by means of pins 44,
44' on the bottom of the flywheel 40 adjacent the upstanding
peripheral wall thereof. The other end of each horizontal lever is
connected with a tension spring 45 or 45' anchored on the flywheel
bottom on the point substantially diametrically opposite to the
pivotal axis of the horizontal lever so as to pivotally move the
free end thereof inwardly toward the drum 30 about the pin 44 44'.
Stops 46, 46' are provided on the flywheel bottom adjacent the free
or forward ends of the horizontal levers 43, 43' for preventing the
free ends of the horizontal levers beyond a predetermined range.
The horizontal levers are formed with recesses 47, 47' of
substantial width and having inwardly downwardly inclined bottom
surfaces for receiving lower rollers 39, 39' of the vertical levers
37, 37'. Each of the horizontal levers is thinned at the portion
next to the recess 47 or 47' and then widened or enlarged to form a
step or shoulder 48 or 48' with which the lower roller 39 or 39' of
corresponding vertical lever is brought into engagement when the
horizontal levers are moved outwardly against the tension springs
45, 45' by centrifugal force. It will thus be noted that the
horizontal levers rotate with the flywheel about the rotational
axis thereof relative to the vertical levers as will be described
in detail hereinafter. Rotatably mounted around the flywheel boss
41 is a ring 49 having diametrically opposing projections 49a,49b
which are linked to the free ends of the horizontal levers 43, 43',
respectively, by means of link rods 50, 50' whereby the pairs of
horizontal levers are controlled to have equalized movements.
Disposed over the drum 30 is a blood bag receiving box or container
generally designated at 50 in FIG. 3. The box 50 has generally
rooflike or inverted V-shape cross section and is composed of a
body 51 and a cover 52. As will be seen in FIG. 6, the body 51 of
the blood bag box 50 has opposite side plates or walls 53, 53' of
generally inverted V-shape and generally rectangular opposite end
walls 54, 54' interconnecting the opposite sidewalls at their
opposite ends. Disposed between the opposite sidewalls 53, 53' are
spaced intermediate plates 55, 55' of substantial thickness for
interconnecting the sidewalls at their intermediate portions. The
intermediate plates have outwardly downwardly inclined upper
surfaces and horizontal bottom surfaces. A pair of bottom plates
56, 56' are connected to the intermediate plates 55, 55'
respectively by means of hinge means 57, 57' for upward swinging
movements. The inner surfaces of the end plates 54, 54' are arcuate
for this purpose. The sidewalls 53, 53' are formed with larger
notches 58, 58' at the top apeces and small notches 59, 59'
adjacent the notches 58, 58', respectively, for the purpose which
will become apparent later. The sidewalls have their horizontal
bottom edges in the plane in which the bottom surfaces of the
intermediate plates 55, 55' extend. The horizontal bottom edges of
the sidewalls 53, 53' have the dimension the same as or slightly
larger than the outer diameter of the drum 30 as measured on the
top thereof. Furthermore, each of the end walls 54, 54' is partly
cut so as to form a vertical plane, the distance between the
vertical planes in the opposite end plates 54, 54' being the same
as or slightly smaller than the distance between the inner surfaces
of the lateral bars 35B, 35B' in the frame 35. It will, thus, be
appreciated that, when the blood bag box body 51 is disposed over
the drum 30, the bottom surfaces of the intermediate plates 55, 55'
are supported by the top of the drum 30 and the vertical planes in
the end plates 54, 54' of the box body 51 tightly contact the inner
surfaces of the lateral bars 35B, 35B' of the frame 35, with the
bottom plates 56, 56' of the box 50 being in contact with and
supported by the inclined surfaces of the bridge 35C of the frame
35 and the upper roller 38, 38' of the vertical levers 37, 37'. The
side plates 53, 53' of the body 51 of the box 50 are shaped such
that, vertical planes in the end plates 54, 54' engage the inner
surfaces of the lateral bars 35B, 35B' in the lower halves
thereof.
The cover 52 of apparent blood bag container 50 is dimensioned and
shaped to match the size and configuration of the body portion 51
of the container and has a pair of parallel side plates 53a 53a'as
seen in FIG. 7, a pair of vertical end walls 54a,54a' as seen in
FIG. 3 and a top plate 56a of a single piece structure. In the
illustrated embodiment, the end walls 54a,54a' and the top plate
56a are formed integrally, but they may be formed separately. A
disc 71 is rigidly secured to the top plate 56a on the apex and
centrally thereof. A hole 72 is formed through the plate 71 and the
top plate 56a. Each of the side plates 53a,53a' is formed with a
semicircular notch 59a,59a' (only the note 59a' is shown in FIG. 3)
at a location corresponding to that of the notch 59 or 59' in each
of the side plates 53, 53' of the body 51. It will, therefore, be
apparent that, when the cover 52 is mounted over the body 51 in the
machine 20, the side plates 53a,53a' and end walls 54a,54a' of the
cover snugly ride on the corresponding parts in the container body
51 with the outer surfaces of the end walls and a part of the outer
surfaces of the side plates in close contact with the inner
surfaces of the lateral bars 35B, 35B' of the frame 35 in the
remaining upper halves of the bar surfaces. It will also be
apparent that, in this position of the box 50, the two pairs of
notches 59 and 59a; 59' and 59a' define two annular openings, one
of which is seen in FIG. 3.
A rod 60, having notches in the opposite sides adjacent the
opposite ends thereof, spans the studs 35E, 35E' above the cover 52
of the blood bag 50 with said notches receiving therein the shanks
of the studs 35E, 35E', as will be seen in FIG. 7. As will be seen
in FIG. 3, the rod 60 is formed, at the intermediate portion, with
a threaded hole 61 with which the above-mentioned shaft 28 engages
at its threaded portion 28a. The shaft 28 further has a reduced
lower portion 28b extending downwardly from the threaded portion
28a into the interior of the blood bag box 50 through a hole 72 in
the disc 71 on the top plate 56a of the cover 52. Thus, it will be
noted that the shaft 28 has a downwardly facing annular shoulder
which engages the top surface of the disc 71. It will be further
noted that, when the shaft 28 is rotated in one of the directions,
it is moved down relative to the rod 60 to press the disc 71
downwardly for rigidly holding the cover 52 of the box 50 against
upward separation from the body portion 51 of the box. In this
state, the upper surface of the rod 60 is urged against the under
surfaces of the enlarged heads of the studs 35E, 35E'.
A description will be made hereunder of the operation of the
above-described centrifugal machine.
When it is desired to place the blood bag set 10 in the centrifugal
machine 20, the shaft 28 is loosed to disengage the rod 60 from the
studs 35E, 35E' and to remove the rod 60 together with the cover 26
from the machine. Then, the cover 52 of the blood bag box 50 is
lifted away from the body 51 of the box and from the supporting
frame 35. Then, the above-described blood bag set 10 is placed in
the box 50 in such a manner that the mother bags 11, 11' extend
downwardly and outwardly along the bottom plates 56, 56' of the box
body 51, respectively, with the short tubings 14, 14' received in
the notches 59, 59' in the box side plates 53, 53' and extending
therethrough into the exterior of the box 50, respectively, and
that the daughter bag 12 extends downwardly into the interior of
the drum 30, with the curved portions of the connecting tubes 13,
13' received in the notches 58, 58' in the side plates 53, 53'. In
this position of the blood bags, the clips on the connecting
tubings 13, 13' are removed so as to provide communication between
the interiors of the mother and daughter bags. The cover 52 is then
placed over the box body 51 and is fastened by means of the shaft
28, the rod 60 and the pair of studs 35E, 35E' in the manner as
described in the above. It will be noted that, when the shaft 28 is
screwed down, the reduced diameter lower end 28b of the shaft 28
extends through the ring 15 on the blood bag set 10 contained in
the box 50.
Upon completion of the above preparation, the motor of the machine
is switched on to rotate its shaft 22 and thus the drum 30
connected thereto. The rotation of the drum is transmitted by the
frame 32 mounted thereon to the blood bag box 50 and thus to the
blood bag set 10 contained in the box with the mother bags 11, 11'
held in inclined state. The machine is operated at 2,000 to 3,000
r.p.m. The blood in the mother bags is, thus, subjected to
centrifugal force by which the red blood cells are gradually moved
down and collected in the bottom portions 16, 16' of the mother
bags 11, 11' whereas the fluid of the blood plasma is gathered in
the upper portions of the bags due to the difference in specific
gravity between the red blood cell and the plasma.
At the start of the operation of the centrifugal machine, each of
the horizontal levers 43, 43' are in their innermost positions in
which they are held in contact with the stops 46, 46' by the
tension springs 45, 45', respectively, and in which the lower
rollers 39, 39' of the vertical levers 37, 37' are positioned on
the radially outer edges of the recesses 47, 47' in the levers 43,
43', respectively, as seen in FIG. 4. The rotation of the drum 30
indicated by an arrow a in FIG. 8 causes the vertical levers to
urge, at the lower ends, the horizontal levers in counterclockwise
direction, which in turn rotates the flywheel 40 in the same
direction. As the rotational speed of the drum 30 increases, the
horizontal levers 43, 43' are moved outwardly against the springs
45, 45' by the centrifugal force, whereas the lower rollers 39, 39'
remain engaging the recesses 47, 47' even at high speed rotation
(FIG. 8).
After a predetermined period of time known from experience as being
sufficient for the red blood cells to be completely separated out
from the liquid of blood plasma, the motor is switched off. The
machine continues rotating due to inertia in such a manner that the
rotational speed is gradually reduced by the resistances of air and
friction generated between mechanical elements. However, the
flywheel 40 has a greater inertia and, thus, has a smaller
deceleration as compared with those of the rotary drum 30. This
produces a relative rotation between the flywheel and the drum.
Namely, the rotary drum becomes to have a lower speed than that of
the flywheel, so that the rollers 39, 39' are disengaged from their
recesses 47, 47' in the horizontal levers 43, 43' down into inside
of the latter and are brought into engagement with the shoulders
48, 48' of the levers as shown in FIGS. 9 and 10. Thereafter, the
inertial rotation of the flywheel as indicated by an arrow b in
FIG. 9 is transmitted through the horizontal and vertical levers
43, 43'; 37, 37' to the drum 30 for rotating the latter together
with the flywheel.
The speed of the flywheel is slowed down in a while and the
centrifugal force in the horizontal levers are reduced so that the
springs 45, 45' bias the free ends of the levers inwardly. these
inward movements of the horizontal levers urge the lower rollers
39, 39' of the vertical levers 37, 37' inwardly to cause them to
rotate about their pivotal axes or pins 36, 36' whereupon the upper
rollers 38, 38' of the vertical levers upwardly urge the bottom
plates 56, 56' of the blood bag box 50 to press the mother bags 11,
11' between the bottom plates and the top plate 56a of the box 50.
Thus, the fluid of blood plasma is squeezed out of the mother bags
11, 11' through tubings 13, 13' into the daughter bag 12. The
arrangement of the above structural elements is such that, when the
horizontal levers 43, 43' are moved to their innermost positions in
which they contact their stops 46, 46' almost all of the liquid of
blood plasma are removed from the mother bags 11, 11' into the
daughter bag 12 leaving the red blood cells with the mother
bags.
At about a time the blood plasma separation is completed, the
flywheel stops its rotation. Then, the cover 52 of the blood bag
box 50 is removed in the above-described manner to replace the
blood bag set 10 from the machine. The lower rollers 39, 39' of the
vertical levers 37, 37' are manually shifted from the shoulders 48,
48' of the horizontal levers 43, 43' into the recesses 47, 47'
therein for the next operation.
Thus, it will be appreciated that, with the apparatus of the
present invention, blood plasma separation is completed during the
period from the time the motor of the centrifugal machine is
switched off to the time the rotation of the machine stops.
The present invention has been described with reference to a
preferred embodiment. It is to be understood that the embodiment
above described is only for illustrative purpose and the present
invention may have various modifications and changes within the
scope and spirit of the invention which is defined by the appended
claims. For example, the set of blood bag 10 in FIG. 1 may be
provided with a pair of additional tubings each interconnecting the
mother bags 11 and 11' at their lower ends for balancing the
quantities of the blood contained therein during initial stage of
centrifugal operation. In addition, the casing 23 in FIG. 3 may be
provided around the cylindrical wall thereof with a circular jacket
through which cooling liquid, such as ethyleneglycol, of a
temperature ranging from 2 to - 3.degree. C. may be circulated for
maintaining the temperature in the casing and thus of the blood in
the blood bags in the casing lower than about 10.degree. C. during
centrifugal separation of the blood.
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