Centrifuge And Self-positioning Tube Holder Therefor

Abstract

A centrifuge having a rotor equipped with a plurality of tube holders, each holder being provided with a movable weight which shifts into different stations, depending on the direction of rotation of the rotor, to alter the center of mass of the holder and thereby pivot the same into different selected positions. Such a construction is particularly useful in a mixing and decanting centrifuge in which the centrifuge tubes are to assume one operating position for filling and/or centrifuging and another operating position for decanting.

Description

BACKGROUND

Various mechanical and electro-mechanical systems have been used to hold centrifuge tubes at more than one fixed position during rotor operation. Co-owned U.S. Pat. No. 3,401,876 discloses a cell-washing centrifuge in which the upper ends of the tubes bear against a dome-shaped cover when the rotor is in operation. By selectively controlling the elevation of the cover the tube angle is varied for filling, centrifuging, and then decanting. In other subsequent designs tiltable tube holders have been provided and electro-magnets have been used to control the positions of such holders. In still other instances, mechanical connections with the tube holders have caused such holders to pivot into the different positions of adjustment. Whatever the case, prior mechanisms for achieving variable tube position have been relatively complex and expensive. Because of their complexity, such mechanisms have often been associated with problems of adjustment, breakdown, and repair.

SUMMARY

The present invention is concerned with a centrifuge having multiple position tubes in which changes in the position of each tube are achieved by varying the center of mass of each holder-tube assembly. The result is a centrifuge which overcomes the disadvantages of prior constructions and, specifically, one which is relatively simple in construction and operation and which does not require mechanical or electro-mechanical connections with the holders for the purpose of shifting such holders into each of their operating positions.

One aspect of the invention lies in the discovery that tube holders may be made to shift into different operating positions if such holders are equipped with movable weights which assume one position or another depending on the direction of rotation of the centrifuge rotor. In a preferred form of the invention the weight is solid and takes the shape of a sphere; however, other shapes are believed suitable and it is conceivable that non-solid (i.e., liquid) weights may be used. The weight is retained in a J-shaped guide passage or track and, when the rotor is at rest, is disposed in the intermediate zone between the leg portions of that passage. If the rotor is then driven in one direction, say forwardly, the weight is directed into the short leg of the passage, whereas if the rotor is driven in its reverse direction the weight moves to the end of the longer leg. In either case, the weight moves along the respective leg of the passage, and is retained at the distal end of that leg during rotation of the rotor, by reason of centrifugal force acting upon the weight. When the weight is in its first position adjacent the end of the shorter leg the center of mass of the holder-tube assembly is such that during rotor operation the holder pivots so that the open-ended tube slopes upwardly and inwardly. In a mixing and decanting centrifuge, such a tube position is suitable not only for centrifuging but also for filling the tubes while the rotor is in operation. Upon reversal of the rotor, the weights assumes a second position adjacent the end of the longer leg, thereby reorienting the center of mass of the holder-tube assembly and causing the holder to pivot so that the tube extends generally upwardly in a decanting position. Stops, which may be adjustable, limit the extent of pivotal movement of the holder in each direction. Since such stops simply limit the extent of movement, the tube holders are essentially self-positioning in response to the condition of operation (i.e., direction of operation, or non-operation) of the rotor.

DRAWINGS

FIG. 1 is a perspective view, partially diagrammatic, of the rotor and motor portions of a centrifuge embodying the present invention;

FIG. 2 is an enlarged perspective view showing a tube holder;

FIG. 3 is another perspective view of the holder taken from the side opposite from that shown in FIG. 2;

FIG. 4 is a sectional view taken along line 4--4 of FIG. 2 and illustrating three positions of the weight in the passage of the holder;

FIG. 5 is a fragmentary top view of the rotor;

FIG. 6 is an enlarged sectional view taken along line 6--6 of FIG. 5 and illustrating an adjustable stop for a tube holder;

FIG. 7 is an enlarged vertical sectional view of a tube holder illustrating three positions of the weight within the holder passage;

FIG. 8 is a top plan view taken along line 8--8 of FIG. 7;

FIG. 9 is a vertical sectional view showing the relative positions of the parts when the rotor is at rest;

FIG. 10 is a schematic representation accompanying FIG. 9 and indicating that when the rotor is viewed in the direction of line 10--10 of FIG. 9 such rotor is stationary or "at rest;"

FIGS. 11 and 12 correspond with FIGS. 9 and 10 but illustrate the relationship of parts when the rotor rotates in a clockwise direction, as during a filling operation;

FIGS. 13 and 14 also correspond with FIGS. 9 and 10 but illustrate the relationship of parts when the rotor turns in a counterclockwise direction, as during a decanting operation.

DESCRIPTION

Referring to the drawings, the numeral 10 generally designates the rotor portion of a centrifuge. The rotor is equipped with a plurality of circumferentially-spaced holders 11 which support open-topped centrifuge tubes 12. A motor 13, diagrammatically illustrated in FIG. 1, is operatively connected to the rotor to drive the rotor selectively and reversibly in either direction about a vertical axis of centrifugation 14. It is to be understood that the centrifuge is also equipped with a housing, cover, and related parts; however, such elements have been omitted from the drawings for clarity of illustration.

In the illustrated embodiment, each holder 11 takes the form of a body which may be molded from plastic, metal, or other suitable material. A horizontal bore 15 receives a pin 16 (FIG. 9) which supports each holder upon the rotor for tipping movement about a pivot axis 17, each such axis being tangent to a horizontal line circumscribing the vertical axis of centrifugation 14. As shown most clearly in FIGS. 1, 5 and 9, each holder is supported by pin 16 within a recess 18 of the rotor. Preferably the flat top surface 11a of each holder is flush with the top surface 10a of the cylindrical rotor when the rotor is at rest (FIGS. 1 and 9).

The open-topped centrifuge tubes 12 are received within cylindrical cavities 19 which extend downwardly from top surfaces 11a of the holders. In the case of a centrifuge intended for use in clinical laboratories, it is preferable that the tubes be formed as separate parts and be removable from the cavities in which they are supported. Thus, the cylindrical tubes 12 may be formed of glass, plastic, or any other suitable material and may, in the embodiment shown in the drawings, be inserted into or removed from the cavities 19. It is to be understood, however, that in some applications it may be desirable to mount the tubes permanently within the cavities, or to form such tubes as integral parts of the holders.

Referring to FIGS. 2 and 4, it will be observed that each holder 11 is also provided with an internal J-shaped passage or track 20 having a relatively short leg 20a, a relatively long leg 20b and an arcuate connecting portion 20c. The legs 20a and 20b of the passage extend along a sloping plane parallel with pivot axis 17 of the holder. Specifically, the legs of the passage extend upwardly and outwardly and in radial directions from the vertical axis of centrifugation 14. The connecting portion 20c of the passage is disposed below pivot axis 17. It is to be noted that the distal end 20d of the short leg of the passage is also disposed below pivot axis 17 but that the distal end 20e of leg 20b is disposed above axis 17.

A weight in the form of a ball or sphere 21 is movable along the length of passage 20 between a first operating position or station A adjacent the distal end of passage leg 20a, an intermediate position or station B along arcuate connecting portion 20c, and a second operating position or station C adjacent the distal end of leg 20b (FIGS. 4, 7 and 8). While a spherical weight is preferred because of the low frictional resistance to movement along the length of the passage, it is believed apparent that such weight need not be spherical or even solid (it might, for example, be liquid) and, if solid, need not take the form of a single member or element. Thus, the weight might be a body of material in particulate form, such as granules, microspheres, etc. The important fact is that the weight, in whatever form it takes, be capable of moving under the influence of centrifugal force from the intermediate or rest position B into either of the operating positions A and C, and of returning (when the rotor is at rest) under the influence of gravity back into the rest position B.

Whether the weight moves into one operating station or the other depends on the direction of rotation of the rotor 10. As previously indicated, and as shown in FIGS. 9 and 10, weight 21 is in its rest position B in the passage's connecting portion 20c when the rotor is stationary. It will be observed that the connecting portion constitutes the lowermost region of the J-shaped passage 20. Under such conditions, the mass of body 21 is insufficient to cause the holder 11 to pivot in a counterclockwise direction about the axis of pin 16 and, consequently, centrifuge tube 12 remains in the generally upstanding position illustrated in FIG. 9.

Should the reversible motor 13 be energized to drive the rotor in a clockwise direction when viewed from above, such direction also being referred to for convenience as the "forward" direction, weight 21 is urged by its own inertia into the shorter leg 20a of the passage. At the same time, centrifugal force acting upon the weight urges it outwardly into position A at the distal end 20b of the shorter leg. As long as the centrifuge continues to operate in the same direction, the weight is in effect locked by centrifugal force in position A. In that position, with the rotor operating at full speed, the mass distribution of the holder-tube assembly causes that assembly to pivot about the axis of pin 16. As shown in FIG. 11 the assembly pivots to tip the centrifuge tube upwardly and inwardly into a centrifuging position. A portion of the holder engages a stop in the form of inclined surface 22 of the rotor to limit the extent of such pivotal movement. Even when the assembly is fully pivoted into the centrifuging position of FIG. 11, it will be observed that the legs of passage 20 slope outwardly as well as upwardly, thereby insuring that centrifugal force acting upon weight 21 will retain that weight in station A at the end of leg 20a.

FIG. 11 reveals that the tipped position of tube 12 may be used advantageously to achieve automatic filling of the tube. For that purpose, rotor 10 is provided with a central manifold chamber 23 having radially extending discharge ports or nozzles 24 alignable with the open ends of the centrifuge tubes 12 when such tubes are tipped upwardly and inwardly as illustrated in the drawing. Liquid from the manifold chamber is discharged from the nozzles under the influence of centrifugal force and passes into the open ends of the tubes as shown in FIG. 11.

At the completion of a filling or centrifuging step, rotor 10 is again brought to rest, the weight 21 of each holder returns to position B, and the centrifuge tubes 12 again assume their generally vertical positions as indicated in FIG. 9. To decant some or all of the liquid from the centrifuge tubes, the motor is simply reversed to drive the rotor in its reverse or counterclockwise direction (FIGS. 13 and 14). At this time the inertia of each weight 21 directs such weight into the longer leg 20b of the passage and centrifugal force urges the weight into position C at the distal end of that leg. In that position, with the rotor rotating at full speed in the reverse direction, the mass center of the holder-tube assembly is such that centrifugal force tends to urge the assembly in a clockwise direction about the axis of pivot pin 16 (as viewed in FIG. 13). Such pivotal movement is limited by engagement between the outer portion of the holder 11 and stop means 25. In the embodiment illustrated, stop means 25 takes the form of an adjustable screw element, the threaded adjustment of that element determining just how far the holder 11 pivots as it moves into its decanting position. It is to be understood that a similar screw element may be threadedly mounted in wall 22 of the rotor so that adjustment of the extent of inward tipping movement of the holder may also be made.

When the holder is in the decanting position of FIG. 13, or in the rest position of FIG. 9, tube 12 has been described as being in a generally vertical or upstanding position. It will be observed from FIGS. 9 and 13 that the tube actually slopes outwardly to a slight but discernible extent. The precise extent may, as already indicated, be adjusted by threading or unthreading stop member 25. The purpose of such adjustment is to insure that at a given operating speed, and with any given liquid contained in tube 12, a predetermined amount of that liquid will be discharged from the open end of the tube under the influence of centrifugal force without at the same time discharging any solid material contained within the tube. The centrifuge may therefore be used as a sample washing device, a sample in tube 12 being first mixed with a washing fluid (normally water) introduced forceably into the tube under centrifugal force in the filling step of FIG. 11, and then discharged from the tube (following centrifugation) in the decanting step of FIG. 13. In the somewhat schematic view of FIG. 13, the solid material is designated by the numeral 26 and the liquid by numeral 27.

In the preferred embodiment shown and described herein, the connecting portion 20c of passage 20 is arcuate. Because of the arcuate shape of portion 20c, the weight 21 is guided smoothly into passage portions 20a or 20b, depending upon the direction of rotation of the rotor. However, it is to be understood that portion 20c may be of somewhat different shape, such as of a V-shaped configuration, or even of a right angular configuration, and still achieve to an appreciable extent the function and advantages of the illustrated construction.

While in the foregoing I have disclosed an embodiment of the invention in considerable detail for purposes of illustration, it will be understood by those skilled in the art that many of these details may be varied without departing from the spirit and scope of the invention.

Claims

I claim:

1. A centrifuge having a rotor mounted for rotation about a substantially vertical axis of centrifugation and having a plurality of circumferentially-spaced holders adapted to support plural open-topped centrifuge containers, each of said holders being mounted for pivotal movement about a pivot axis generally tangent to a horizontal line circumscribing said axis of centrifugation, and motor means for rotating said rotor, wherein the improvement comprises said motor means being operatively connected to said rotor for selective rotation of said rotor in forward and reverse directions, each holder being provided with a weight shiftable with respect to such holder between a first position when said rotor turns in its forward direction and a second position when said rotor turns in its reverse direction, said weight when in said first position urging said holder to pivot the open top of said container inwardly towards said axis of centrifugation and when in said second position urging said holder to pivot the open top of said container outwardly away from said axis of centrifugation.

2. The structure of claim 1 in which said weight is also shiftable into an intermediate position between said first and second positions when said rotor is at rest, said weight being movable from said intermediate position into said first and second positions under the influence of said centrifugal force.

3. The structure of claim 2 in which each holder is provided with a guide passage supporting said weight for movement between its respective positions.

4. The structure of claim 3 in which said weight is solid.

5. The structure of claim 4 in which said solid weight is spherical and is supported by said guide passage for rolling movement therealong.

6. The structure of claim 3 in which said guide passage is generally J-shaped having a relatively long leg portion, a relatively short leg portion, and an intermediate connecting portion, said weight being disposed adjacent the distal end of said short leg portion when said weight is in its first position and being disposed adjacent the distal end of said long leg portion when said weight is in its second position.

7. The structure of claim 6 in which said weight is disposed along said interconnecting portion of said passage when said weight is in its intermediate position.

8. The structure of claim 6 wherein said interconnecting portion of said passage is arcuate.

9. The structure of claim 6 in which said leg portions extend along a plane parallel with the pivot axis of said holder.

10. The structure of claim 7 in which said leg portions of each holder extend upwardly and outwardly away from said axis of centrifugation.

11. The structure of claim 10 in which said leg portions of each holder also extend along a plane parallel with the pivot axis of such holder.

12. The structure of claim 2 in which said rotor is provided with stop means for limiting the extent of pivotal movement of each holder about the pivot axis thereof.

13. The structure of claim 12 in which said stop means is adjustable.

14. A centrifuge having a rotor mounted for rotation about a substantially vertical axis of centrifugation and having a plurality of circumferentially-spaced holders equipped with a plurality of open-topped centrifuge tubes, each of said holders being mounted for pivotal movement about a pivot axis generally tangent to a horizontal line circumscribing said axis of centrifugation, and motor means for turning said rotor, wherein the improvement comprises said motor means being selectively reversible for turning said rotor in forward and reverse directions, each holder being provided with a weight movably mounted with respect thereto and being shiftable under the influence of centrifugal force from a rest position when said rotor is stationary into a first operating position when said rotor turns in its forward direction and into a second operating position when said rotor turns in its reverse direction, said weight when in said first operating position orienting the mass center of said holder and tube to pivot said holder so that the top of said tube tips inwardly towards said axis of centrifugation, and when in said second operating position re-orienting the mass center of said holder and tube to pivot said holder so that the open top of said tube is urged in an outward direction away from said axis of centrifugation, and a pair of stops for limiting the extent of tipping movement of each holder as the weight thereof is shifted between its first and second operating positions.

15. The structure of claim 14 in which at least one of said stops is adjustable.

16. The structure of claim 14 in which said weight, when in said first operating position, urges said holder to orient said tube in an upwardly and inwardly inclined filling-centrifuging position, and means provided by said rotor for selectively introducing fluid into said tube when the same is in its filling-centrifuging position.

17. The structure of claim 16 in which said last-mentioned means includes a manifold chamber and a plurality of nozzles projecting outwardly from said rotor and communicating with said chamber, each nozzle registering with one of said tubes for discharging fluid therein when said tubes are in their filling-centrifuging positions.

18. The structure of claim 14 in which said weight, when in said second operating position, urges said holder to orient said tube in a generally upstanding decanting position, whereby, fluid contained within said tube is discharged from the open end thereof under the influence of centrifugal force when said rotor turns in its reverse direction.

19. The structure of claim 14 in which each holder is provided with a guide passage supporting said weight for movement between its respective positions.

20. The structure of claim 19 in which said weight is of solid material.

21. The structure of claim 20 in which said weight is a spherical solid and is supported by said guide passage for rolling movement therealong.

22. The structure of claim 19 in which said guide passage is generally J-shaped having a relatively long leg portion, a relatively short leg portion, and an interconnecting portion, said weight being disposed adjacent the distal end of said short leg portion when said weight is in its first operating position and being disposed adjacent the distal end of said long leg portion when said weight is in its second operating position.

23. The structure of claim 22 in which said weight is disposed along said interconnecting portion of said passage when said weight is in its rest position.

24. The structure of claim 22 in which said interconnecting portion of said passage is arcuate.

25. The structure of claim 22 in which said leg portions extend along a plane parallel with the pivot axis of said holder.

26. The structure of claim 23 in which said leg portions extend upwardly and outwardly away from said axis of centrifugation.

27. The structure of claim 26 in which said leg portions extend along a plane parallel with the pivot axis of said holder.