CA1159803A

CA1159803A - Centrifuge assembly

Info

Publication number: CA1159803A
Application number: CA000326115A
Authority: CA
Inventors: Alfred P. Mulzet
Original assignee: International Business Machines Corp
Current assignee: International Business Machines Corp
Priority date: 1978-07-21
Filing date: 1979-04-23
Publication date: 1984-01-03
Also published as: NL7905622A; IT7923938A0; GB2025797A; DE2925010A1; GB2095588A; ES482170A1; FR2460718B1; JPS575585B2; SE7906179L; JPS5515688A; IT1165127B; GB2095588B; FR2460718A1; GB2025797B

Abstract

CENTRIFUGE ASSEMBLY
ABSTRACT
An improved centrifuge assembly comprising a channeled rotor assem-bly and a fluid container disposed in the channel, whereby the centri-fugal separation effects in the fluid container are determined by the geometry of the channel in the rotor. This arrangement is particularly useful for two-stage blood platelet separation. The fluid container is preferably formed from semirigid plastic material and is considered a disposable item to be discarded after a single use. The rotor assembly preferably includes a removable filler piece or center piece formed from a single piece of material, such as rigid plastic, as by machining or molding, and having therein an open-topped channel having dimensions appropriate to receive the semirigid container, which is suitably curved and placed in the channel. Fluid connections are provided from a multi-chambered cavity attached to the ends of the container to an axially located multi-channel rotating seal. The connections lie in a plurality of radial slots in the filler piece. The channel is divided into two distinct portions, the first portion of the channel being circular, and the second portion being spiral-like and having a plurality of radiuses, each measured from a different center, the spiral increasing radially outward from its juncture of the first stage and the second stage. A
transition section connects the two portions, and forms a spillway be-tween the two portions. The channels are proportioned and arrayed so that the centrifuged red cells move toward the outer wall of the first portion, from whence they retroflow to an entry chamber and thence to a fluid connection by which the red cells are drawn off.

Description

1 ~L~d3 - CENTRIFUGE ASSEMBLY
Background of the Invention (1) Field of the Invention Previous centrifuges for separating the components of blood are known in which the centrifuge bowl is reusable, and is provided with relatively complex channeling or grooves, and fluid connections, making the device expensive and difficult to clean and sterilize for each use.

(2) Description of the Prior Art The present invention provides an improved centrifuge bowl and container assembly for use with blood cell separators of the type shown, for example, in U.S. Patent 3,4~9,145 issued January 13, 1970. In this prior arrangement a solid centrifuge element was used, having appropriate channels cast or machined therein, and did not contemplate reusable bags.
Bag structures not requiring channeled support elements are disclosed in U.S. Patents 3,748,101 issued July 24, 1973 and 4,007,871 issued February 15, 1977. However, such arrangements are not as efficient or economically manufactured as the subject invention. None of this art or other known prior art provides a centrifuge assembly comprising a solid reusable rigid center element arranged to provide a conformed channel for a disposable tube of semirigid material, having fluid connections to appropriate ends thereof. U.S~ Patent 4,010,894 issued March ~, 1977 also discloses a centrifuge container which can be used for two-stage platelet separation, but it has been found that the present invention provides a much higher yield.
A Canadian application, Serial No. 300,376, filed April 4, 1978, discloses and claims a centrifuge assembly including a container having a circular portion and a spiral portion, but which does not correspond to the detailed geometry of the EN9-78-009 - ~ '~

1 1 5 ~
present invention as described and claimed herein. A
publication of the U.S. Department of Commerce, National Technical Information Service, No. PB-277 242 dated 19 July 1977, and titled "Blood Cell Separator" shows and describes an - ~N9-78-009 -la-,.~. ......

1 ~5~8~33 1 arrangement using a helical blood bag, but does not disclose the de-2 tailed geometry of the present invention.

3 A selection of papers dealing with blood centrifuging is entitled

4 "Leucocytes: Separation Collection and Transfusion" edited by J.M.
Goldman and R.M. Lowenthal, and published in 1975 by Academic Press.
6 Summary of the Invention 7 It is a general object of this invention to provide an improved 8 rotor assembly for a centrifuge.
9 Another object of the invention is to provide an improved rotor assembly utilizing a disposable container for centrifuging blood to 11 obtain different fractions therefrom.
12 A further object of the invention is to provide an improved rotor 13 assembly and associated container for centrifuging blood, which is 14 simple and economical in construction, and the container is disposable after a single use.
16 Still another object of the invention is to provide an improved 17 blood centrifuge assembly particularly suited for efficient two-stage 18 platelet separation.
19 The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular descrip-21 tion of preferred embodiments of the invention, as illustrated in the 22 accompanying drawings and described in connection therewith in the 23 annexed specification.
24 Briefly described, the improved assembly provided by this invention comprises a rotor assembly, which comprises, in a first embodiment, a 26 centrifuge bowl and a filler or center piece, which can be removable 27 from the bowl.
28 An open-topped channel, substantially rectangular in cross section, 29 is machined, molded or othrwise formed in the filler piece. The channel has a first portion which is circular, having a radius which extends 31 from a point which is slightly offset from the true center. This first 32 portion extends through a first angular distance, of the order of 150 EN9-~,009 - 2 -l 159~03 1 degrees, for example, from the innermost end of the channel. A short 2 transition portion connects the terminal end of the first portion with 3 the initial end of the second or spiral-like portion of the channel, 4 which initial end is located at a shorter radius than the radius of the first portion.
6 The transition portion has a second arcuate dimension of approx-7 imately 24 degrees, for example, and is directed radially inward, and 8 rapidly norrowing to the dimension of the second spiral portion.
g The second or spiral-like portion comprises a plurality of arcuate segments, of increasing radius, and having centers displaced from the 11 true center. The spiral-like portion progresses radially outward, and 12 terminates near the angular location of the initial end of the circular 13 portion.
14 Fitted into the channel described above is a fluid container com-15 prising a tube having a rectangular or substantially rectangular cross 16 section, closed at both ends by a cavity member providing inlet and 17 outlet chambers and provided with a plurality of fluid connections or 18 inlet and outlet tubes. These tubes, together with a suitable rotating 19 seal, permit the introduction of whole blood into the container and the 20 withdrawal of blood fractions following centrifugal separation. The 21 cross-sectional area of the second portion of the container is sub-22 stantially one-fourth of the cross-sectional area of the first portion 23 of the container, in order to achieve higher flow velocity in the second 24 portion. The fluid container and the tubing connections may be formed 25 of medical grade polyvinyl chloride.
26 The cross section of the second portion is designed to have a 27 greater vertical height than the vertical height of the first portion, 28 and conversely, the width of the second portion is less than the width 29 of the first portion.
In another embodiment, the entire rotor assembly is made in one 31 pi ece by molding and/or machining, with a channel as above described 32 formed in the rotor.

.~ . .

1 ~5g8~
1 Brief Description of the Drawings 2 In the drawings, FIG. 1 is a diagrammatic perspective view showing 3 a centrifuge bowl, a filler or center piece, and a fluid container in an 4 exploded relation in accordance with one preferred form of the inven-tion;
6 FIG. 2 is a diagrammatic plan view of the filler piece shown in 7 FIG. 1;
8 FIG. 3 is a sectional elevation view of the filler piece of FIG. 2 9 taken at the section 3-3.
FIG. 4 is a diagrammatic partial cross section elevation view of a 11 centrifuge assembly using a one-piece rotor, in accordance with another 1~ with another preferred embodiment of the invention;
13 FIG. 5A is an exploded plan view of the cavity and its top, in 14 which the ends of the container are cemented and wherein the various input and output lines are terminated; and 16 FIG. 5B is an exploded elevational view of the cavity.
17 Similar reference characters refer to similar parts in each of the 1~ several views.
19 Detailed Description of the Preferred Embodiments Referring to the drawings, there is shown, in FIG. 1, a centrifuge 21 bowl 1, arranged to be spun around an axis of rotation by suitable 22 means, not shown since the specific rotating means is not germane to 23 this invention. The bowl can be formed of any suitable material such as 24 metal or plastic or a combination of materials.
Seated within the bowl I is a filler or center piece 3 which can be 26 formed of any suitable material, by molding and/or machining. The 27 filler piece 3 is dimensioned so that when in place in the bowl 1, the 28 filler will be concentric with the bowl. It can be retained in place on 29 a central hub, or on the outer rim or a plurality of distributed bosses or pins. A channel 5, described later in detail, is machined, molded or 31 otherwise formed in the top surface of filler piece 3. The filler piece 32 3 has a central hole or opening 7 which accommodates the 9-78-009 ~ 4 ~

1 fluid connections to the fluid container, to be subsequently described, 2 and a rotating seal 9. Also the opening may be dimensioned to fit over 3 a central hub in the bowl, to accurately locate and retain the filler 4 piece. The seal 9 may be of the type shown in U.S. Patent 3,489,145 issued January 13, 1970, for example. Filler piece 3 also has a plur-6 ality of radial slots 11 in the upper portion of the piece, which re-7 ceive the fluid connections or tubes to the container.
8 The fluid container comprises a length of semi-rigid plastic 9 tubing 13, preferably of medical grade polyvinyl chloride and having a substantially rectangular cross section. Different cross-sectional 11 areas are provided, as later described. The tubing is formed in a 1~ spiral-like configuration as shown, with each end sealed in a cavity 16.
13 The container is generally shaped to fit the channel 5. Fluid connec-14 tions to the container are provided by a plurality of tubing connections 17, 18, 19 and 20, to the cavity 16, one of which (17) serves as an in-16 put connection. The cavity 16 is provided with two separate chambers, 17 one of which serves a dual function as the input chamber and red blood 1~ cell chamber and the other of which serves as the collection chamber For 19 the platelet concentrate and the plasma. Connection 18 is for extrac-tion of the red cells, connection 19 serves as an output connection for 21 plasma, and connection 20 serves as a platelet concentrate outlet. When 22 the container 13 is placed in channel 5, the tubes 17 through 20 are 23 placed in the appropriate slots 11 in filler piece 3.
24 FIG. 2 is a plan view of the filler piece shown in FIG. 1, and further shows the relationship between the various elements, particularly 26 the geometric relationships for the various portions of the channel, and 27 hence for the container.
28 It should first be noted that the channel, and hence the container, 29 have two basic geometric patterns. The innermost or first portion, ex-3~ tending for substantially 130 degrees, is circular-like for the first 31 part thereof (ARC1) and is spiral-like inward for approximately the last 32 38 degrees of arc (ARC2). The outermost or second portion comprises EN9-78-~09 5 _ ~' 1 ~9~
1 four ar~uate segments (ARC3, ARC4, ARC5, ARC6), each having a differ-2 ent radius of different decreasing magnitudes respectively, and extend-3 ing from different centers C3, C4, C5 and C6, which are located at 4 variously displaced distances from the true center TC. These segments extend through arcs ARC3, ARC4, ARC5 and ARC6, respectively, and total 6 to substantially 180 degrees. The spiral is defined by the equation:
7 r = 138.9e~-230 , in millimeters, 8 and is approximated by four circular arcs having four different radii 9 and turned from four different centers. The radii, center location and angular extremes of the four arcs are defined in the following table:
CENTER LOCATION ANGULAR EXTREMES

12 ARC1 Cl 83.1 1.0 0 2014' 15021' 13 ARC2 C2 51.9 26.1 15.4 15021' 20922' 14 ARC3 C3 77.4 8.2 15.7 17535' 21535' ARC4 C4 91.0 19.3 7.8 21535' 25535' 16 ARC5 C5 106.9 23.2 7.6 25535' 29535' 17 ARC6 C6 125.5 15.2 24.4 29535' 33535' 18 The liner measurements are in millimeters.
19 These segments taken together form a spiral-like portion for plate-let concentrate collection as subsequently described. A short trans-21 ition portion TP couples the first and second portions together. As 22 shown, the transition section leads radially inward from the outlet 23 end of the first portion to the inlet end of the second portion. The 24 inlet connection 17 for the whole blood is connected to the inlet chamber of the cavity joining the ends of the tubing. Also, the fluid 26 connection 18 to the inlet chamber is provided for removing the red 27 blood cells which are centrifuged against the outer wall of the first 28 portion. The end of connection 18 extends outwardly almost to the 29 outer wall of the inlet chamber, so that the packed red cells can be removed without removing any of the incoming whole blood.
31 The geometry of the first portion is such that the red blood cells 32 which move to the outer wall flow against the direction of flow of the ,~,....

8t~3 l incoming whole blood, and reach the bottom of the inlet chamber, from 2 whence they are removed by the connection 18. The input line 17 is 3 terminated at the top or inward end of the inlet chamber, so that the 4 whole blood and the packed red cells are adequately separated.
Separation of platelets occurs in both the first (inner) and second 6 (outer) portions. Some of the platelets which separate in the inner or 7 first portion settle on the interface between the red cell and plasma at8 the downstream dam of the channel in the transition portion TP. These 9 platelets tend to be the largest and therefore, most desireable plate-lets to collect. Consequently, the first portion of the assembly is 11 designed such that these separated platelets can easily be spilled over 12 into the second portion without spilling many red cells.
13 The essential design features of the first portion of the assembly 14 are as follows:
1. The inner wall of the first portion is smooth, coninuous and 16 gently changing so that the interface can be drawn to the 17 innermost radial point of the channel without any substantial 18 turbulence in the flow which would cause an excessive mixing 19 of the red cell-platelet-plasma interface.
2. The majority of the first portion channel is slightly offset 21 from the true center to assist in pumping the separated red 22 cells back to the RbC port.
23 3. At the downstream extreme, the first portion of the channel 24 deflects inwardly. This provides a comfortable operating point for the interface at which the plasma layer in the 26 majority of the channel is very thin and the risk of acciden-27 tally spilling red cells to the second channel is minimal.
28 Keeping the plasma layer thin is essential to high yields 29 because the thin layer yields a high plasma velocity which assists in keeping the platelets moving toward the second 31 stage.
32 4. The first portion of the channel narrows just prior to the ~99 f'~

~ 3 1 entrance to the second portion. This narrowing is used to 2 concentrate the platelets which are intentionally spilled to 3 the second portion after collecting on the interface of the 4 First portion. The narrowing makes it easier to detect when the majority of the platelet concentrate has been spilled.
6 Using conventional stroboscopic techniques, the operator of the 7 centrifuge can observe the interface at the transition portion TP, and 8 adjust the flow rates so that the interface approaches very closely the g inner wall of the container at the exit bend from the first portion.
Such platelets as have already been separated will then move at high 11 velocity through the transition portion and into the second smaller 12 spiral-like portion of the container. It has been found that high flow 13 velocity of the concentrate is very necessary if the platelets are not 14 to aggregate into clumps, which would then require a resuspension opera-tion. ~or this reason, the inner width of the container for the second 16 portion is reduced to substantially one quarter the inner width of the 17 first portion, for example, one sixteenth inch and one quarter inch 18 respectively. Reduction in the cross section results in higher flow 19 velocity in the narrower portion.
At the terminal or outlet end of the second sprial-like portion of 21 the container, there is provided a collecting chamber 23 in the cavity Z2 16. This is a closed chamber in the cavity, with the exit end of con-23 tainer 13 entering at one side thereof, slightly above the outward wall 24 or bottom of the cup. A small bore tube extends from the inward or top end of the well down to, but not touching the bottom. This tube 20 is 26 the platelet concentrate outlet connection. As noted previously, it is 27 necessary to keep the cross-sectional area relatively small in order to 28 achieve high flow rates. Thus the platelet concentrate connection 20 is 29 on the order of one thirty-second of an inch I. D. as compared with three-sixteenths inch I. D. for the other connections. A plasma outlet 31 connection 19 is provided at the top of the collecting well or chamber 3~ 23.

~ 3 1 FIG. 3 is a cross-sectional elevation view taken along the section 2 line 3-3 in FIG. 2, and shows as the vertical alignment of the two por-3 tions.
4 It will be readily apparent to those skilled in the art that the embodiment described above provides an assembly in which a plurality of 6 filler pieces could be interchangeably utilized in the same centrifuge 7 bowl, including the one described above. If such interchangeability is 8 undesirable or unnecessary, a one-piece rotor may be used, forming, with 9 the container, another preFerred embodiment of the invention. Such a structure will be apparent from the cross-sectional view shown in FIG.
11 4, showing how the bowl and center piece can be formed from one piece of 12 material, either by molding or machining.
1~ Referring to FIGS. 5A and 5B, the cavity 23 comprises a bottom 14 portion 25 and a top or plug 27, each preferably molded from suitable plastic, and then cemented together. The boss or projection 29 on the 16 top 27 contacts the portion 31 of bottom 25 and is cemented thereto to 17 effectively divide the cavity into two chambers, an inlet chamber gen-18 erally designated by reference character 33 and an outlet chamber 23.
19 The side opening 37 receives the inlet end of the first spiral portion of the fluid container, and the side opening 39 receives the outlet end 21 of the second spiral portion of the container. The whole blood input 22 line 17 is received in the portion of cap 27 at the top of the inlet 23 chamber 33. The red blood cell line 18 has an extension 41 which extends 24 to the bottom of inlet chamber 33, where the red blood cells collect after retroflow in the first spiral portion of the container. Plasma 26 outlet line 19 is terminated in the top of cap 27, on the side comprising 27 the outlet chamber 23. The platelet output line 20 is received in a 28 groove 43 extending along the cavity and having its outer end cemented 29 in a passage which opens into the outermost end of the outlet chamber 23.
31 From the foregoing, it will be apparent that the present invention 32 provides a novel centrifuge assembly which is advantageous from the 33 standpoint of being economical to fabricate and includes a low cost 9~ 7 8--o o g "~

1 ~ 5~33 1 simple disposable fluid container to be discarded after a single use, thereby removing the expensive duties of cleaning and sterilizing re-3 quired with reusable centrifuge containers.
4 While the invention has been particularly shown and described withreference to several preferred embodiments thereof, it will be under-6 stood by those skilled in the art that various changes in form and 7 details may be made therein without departing from the spirit and scope8 of the invention.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A disposable elongated container of semi-rigid material for use in a centrifuge rotor bowl, said container having first and second ends, a first portion of said container being adapted to have circular-like configuration, and a second portion of said container being adapted to have spiral-like configuration with an increasing radius, a transition portion connecting the terminal end of the first portion with the initial end of the second portion, said initial end of the second portion being adapted to be located radially inward of the terminal end of the first portion, a plurality of fluid connections to the first end of said elongated container for introducing fluid through an inlet near the inner wall thereof and for withdrawing the component of said fluid which accumulates beyond the inlet, at least one fluid connection to the second end of said elongated container for withdrawing the remaining fluid, and said first portion of said container, when inserted in a rotor bowl, having a substantially constant radious offset from the center of rotation of the rotor bowl whereby some of the fluid that enters at the first end of said container counterflows back to said first end and exits at said first end while the remaining fluid exits at said second end.

2. A centrifuge assembly for use in a centrifuge having a rotor bowl, comprising, in combination:
means forming a channel which has first and second portions connected seriatim, said first portion having a circular configuration and said second portion having a spiral-like configuration, a disposable elongated container of semirigid material contained in said channel, said container having first and second portions corresponding to the first and second portions of said channel, each of said first and second portions having first and second ends, a transition portion connecting the second end of first portion with the first end of the second portion said first end of the second portion being located radially inward of the second end of the first portion, and a plurality of fluid connections to the first end of said elongated container for introducing fluid through an inlet near the inner wall and for withdrawing the component of said fluid which accumulates beyond the inlet, at least one fluid connection to the second end of said elongated container for withdrawing the remaining fluid, and, said first portion of said channel having a substantially constant radius offset from the true center of said rotor bowl whereby some of the fluid that enters at the first end of said container counterflows back to said first end and exits at said first end while the remaining fluid exits at said second end.

3. A container as claimed in claim 1 in which said fluid connections comprise an inlet connection to one end of said container, and at least one output connection to the other end of said container.

4. A container as claimed in claim 2 in which said container is formed from medical grade polyvinyl chloride.

5. A centrifuge assembly as claimed in claim 2 in which said means for forming a channel comprises a filler piece is provided with a plurality of radial slots to receive said fluid connections.

6. A disposable elongated container as claimed in claim 1 characterized by said container comprising a length of semirigid tubing having a substantially rectangular cross section.

7. A container as claimed in claim 6 in which the height and width of the container correspond to the height and width of said channel.

8. A centrifuge assembly as claimed in claim 2 wherein the width of the disposable container in said second spiral portion is substantially one-fourth of the width of the container in said first spiral portion.

9. A disposable container as claimed in claim 1 in which said container is provided with a collecting well at the outlet end thereof, and outlet fluid connections at the outlet end of the container are terminated in said collecting well.