US3825178A

US3825178A - Centrifuge rotor

Info

Publication number: US3825178A
Application number: US00209272A
Authority: US
Inventors: D Burg
Original assignee: American Hospital Supply Corp
Current assignee: American Hospital Supply Corp; Baxter Healthcare Corp
Priority date: 1971-12-17
Filing date: 1971-12-17
Publication date: 1974-07-23
Anticipated expiration: 1991-07-23
Also published as: CH581502A5; GB1423334A; FR2270945A1; CA996525A; DE2419865C2; FR2270945B1; DE2419865A1; BE815067A

Abstract

A fixed angle centrifuge rotor is provided which can be molded from a single cavity mold with no secondary operations. The rotor includes a central hub portion and a generally frusto-conical outer portion extending downwardly and radially outwardly from the central portion for holding the tubes to be centrifuged. The frusto-conical portion is provided with a plurality of radially outwardly extending recesses, each recess being defined by radially-spaced bottom wall portions and radially-spaced top wall portions, the top wall portions being aligned with the spaces in the bottom wall portions. A tube positioned within a recess is held securely by a pair of bottom wall portions and a pair of top wall portions, but at any cylindrical cross section through the frusto-conical wall the tube is held by only a top wall or a bottom wall.

Description

United States Patent [1 1 mg July 23, 1974 CENTRlFUGE ROTOR [75] lnventorz Donald E. Burg, Miami, Fla. [57] ABSTRACT A fixed angle centrifuge rotor is provided which can [73] Assgnee' i g fl be molded from a single cavity mold with no seconorpora vanston dary operations. The rotor includes a central hub por- [22] Filed: Dec. 17, 1971 tion and a generally frusto-conical outer portion ex- 7 tending downwardly and radially outwardly from the [21] Appl 209272 central portion for holding the tubes to be centrifuged. The frusto-conical portion is provided with a plurality [52] U.S. Cl. 233/26 f radially outwardly xt nding re ss s, a h r ess [51] Int. Cl B04b 9/12 being defined by radially-spaced bottom wall portions [58] Field of Search 233/26, 27, 28, 46, 16, and radially-spaced top wall portions, the top wall por- 233/21, 1 R tions being aligned with the spaces in the bottom wall 1 portions. A tube positioned within a recess is held se- [56] References Cited curely by a pair of bottom wall portions and a pair of UNITED STATES PATENTS top wall portions, but' at any cylindrical cross section 3,235,173 2/1966 Unger 233/26 x through the frusto'comcal wall the tube held by only Primary ExaminerGeorge H. Krizmanich a top wall or a bottom wall.

v 17 Claims, 8 Drawing Figures 8A 2\5 32 I6 2a 1 CENTRIFUGE ROTOR BACKGROUND AND SUMMARY This invention relates to a centrifuge rotor, and, more particularly, to a fixed angle centrifuge rotor which can be molded by a single cavity mold without secondary operations such as drilling or milling.

Fixed angle centrifuge rotors generally include a central hub portion for attaching the rotor to the centrifuge and an outer tube-holding portion for holding a plurality of generally radially extending tubes at an angle to the plane of rotation. Heretofore, the fabrication of such rotors generally required a plurality of steps including secondary or finishing operations such as drilling the holes for the tubes.

The invention provides a rotor which can be molded is a single operation in asingle cavity mold and does not require secondary operations. The rotor can therefore be produced very economically, and the resultant integrally molded structure has characteristic high structural integrity.

DESCRIPTION OF THE DRAWING The invention will be explained in conjunction with an illustrative embodiment shown in the accompanying drawing, in which FIG. 1 is a top perspective view of a centrifuge rotor which is formed in accordance with the invention and which is holding a number of tubes to be centrifuged;

FIG. 2 is a top plan view of the centrifuge rotor without the tubes;

FIG. 3 is an elevational view of the rotor;

FIG. 4 is a sectional view taken along the line 4-4 of FIG. 2;

' FIG. 5 is an enlarged fragmentary view of a portion of FIG. 4 showing a tube positioned in one of the tubeholding recesses of the rotor;

FIG. 6 is a bottom plan view of the rotor;

FIG. 7 is a fragmentary sectional view taken along the line 77 of FIG. 4; and

FIG. 8 is a fragmentary sectional view taken along the line 8-8 of FIG. 4.

DESCRIPTION OF SPECIFIC EMBODIMENT Referring now to the drawing, the numeral 10 designates generally a centrifuge rotor having a generally circular configuration. The rotor includes a generally circular central hub portion 11 having a central opening 12 and a generally frusto-conical outer tube wall. A cylindrical attaching sleeve 17 of metal or other suitable material is secured within the cylindrical wall 16 and provided with diametrically opposed key ways or slots 18 which permit the rotor to be secured for rotation with the rotary drive shaft of the centrifuge.

A cylindrical wall-or rib 20 extends generally perpendicularly upwardly from the outer periphery of the hub portion and is provided with a plurality of circumferentially spaced openings 21 adjacent the hub portion. A frusto-conical wall 22 extends outwardly and downwardly from the cylindrical wall 20 adjacent the upper ends of the openings 21 and is interrupted by a plurality of slots, recesses, or openings 23 which are aligned with the openings 21 and which extend parallel to the radial direction of the rotor, i.e., the slots 23 extend in planes which pass through the center of the hub and which extend vertically in FIGS. 3 and 4. The frusto-conical wall 22 terminates at a second cylindrical wall or rib 24 which extends concentrically with the inner cylindrical wall 20 and which is also provided with a plurality of circumferentially spaced openings 25 which are aligned with the slots 23 and openings 21. A generally V- shaped end or outer wall 27 is connected to the bottom of the outer cylindrical wall 24 and includes an upwardly and outwardly inclined frusto-conical portion 28 and a generally cylindrical outer portion 29. A generally U-shaped tube-supporting wall 30 extends between each adjacent pair of the interrupted portions of the frusto-conical wall 22 to provide a bottom support for each of the tubes. Referring to FIG. 7, eachsupporting wall 30 includes a pair of side wall portions 31 which extend downwardly from the frustoconical wall 22 and an arcuate central or bottom wall portion 32 which extends outwardly and downwardly relative to the hub portion. As can be seen best in FIGS. 4 and 5, each bottom wall 30 includes an inner end 33 which terminates slightly outwardly of the outer surface of the cylindrical wall 20 and an outer end 34 which terminates slightly inwardly of the inner surface of the outer cylindrical wall 24. The outer periphery of the planar wall 15 of the hub terminates inwardly of the inner surface of the cylindrical wall 20 adjacent the openings 21 therein as at 35, and the end wall 27 terminates outwardly as at 36 of the outer surface of the cylindrical wall 24 adjacent the openings 25 therein.

A plurality of tube-receiving recesses are thereby provided by the rotor in which eachU-shaped wall 30 provides longitudinally extending side and inclined bottom support for the tube and the

cylindrical walls

20 and 24 at the upper ends of the

openings

21 and 25 therethrough provide top retaining walls. The upper ends of these openings are arcuately shaped and have inclined surfaces which extend parallel with the cylindrical outer surface of the tube 14 when supported by the bottom wall 32 for mating engagement with the cylindrical tube, and each pair of side walls 31 and the side portions of the

openings

21 and 25 are spaced apart approximately the diameter of the tube. The tube is thereby received relatively snugly in the recess and is secured against movement in any transverse direction. Upward movement is restrained by the cylindrical walls 20 and24, downward movement is prevented by the bottom Wall 32, and transverse or side movement is prevented by the side walls 31 and the sides of the

openings

21 and 25. Pivotal movement of the tube is prevented by the spaced-apart top walls provided by the

walls

20 and 24 in cooperation with the elongated bottom wall 32. Further, in the particular embodiment illustrated, additional bottom support for the tube is provided by the portion of the planar wall 15 of the hub which is aligned with the axis of the tube. This portion of the planar wall 15 may advantageously be beveled as at 37'to extend parallel with the outer surface of the tube to provide a slightly longitudinally extending supporting surface for the tube.

A tube containing material to be centrifuged may be inserted into each recess by inserting the tube closed end first through an opening 21 in the inner cylindrical wall 20 at the same inclination as the bottom wall 32. The tube is pushed along the bottom wall until the closed end 14a thereof passes through the opening 25 and engages the inclined frusto-conical wall 28 (FIG. The frusto-conical wall 28 extends generally transversely to the axis of the tube to provide an abutment or stop for the closed end of the tube, and the tube is thereby secured against outward movement under the influence of centrifugal force as the rotor rotates.

I have found it advantageous to provide the inner cylindrical wall with a substantial axial extent above the frusto-conical wall 22 to protect the inner ends of the tubes and to provide a convenient portion for gripping and lifting the rotor. However, the axial length of the wall 20, the angle of inclination and the length of the tubes, and the radius of the hub are such that each tube can be inserted and withdrawn without interference from the other tubes.

Referring to FIG. 4, the rotor does not include any vertically spaced parts, i.e., parts which are spaced in the axial direction of any cylindrical cross section taken about the center of the rotor. Accordingly, it will be apparent that the rotor can be molded in a single shot by a single cavity two-part mold, relative movement of the two mold parts being in the axial direction of the rotor. The rotor can thereby be molded in a single operation, and no finishing or secondary operation such as drilling or milling are required to provide the tube-receiving recesses. The tubular attaching sleeve 17 can be positioned in the stationary mold half before the molding operation so that the rotor is molded in place around the sleeve. If desired, port or recess identification numbers or other indicia can be formed on the frustoconical wall 22 adjacent each recess by the mold. The rotor can be molded either from thermoplastic or thermosetting resin material or from metal.

It is desirable to provide at least three upper and lower retaining surfaces for the tube in any longitudinal cross section in order to prevent pivoting of the tube, two of the retaining surfaces being positioned on one side of the tube at spaced locations and the other supporting surface being positioned on the other side of the tube between the spaced surfaces. While in the specific embodiment illustrated the tube is prevented from pivoting in a radially extending plane by the two top retaining surfaces provided by the

walls

20 and 24 and the bottom retaining surface 32, it will be understood that a single top retaining surface can be provided between a pair of spaced bottom retaining surfaces. Such a structure could still be molded in a single operation since the top surface would not be aligned in any cylindrical cross section with either of the bottom supporting surfaces. Although it is desirable to use at least three retaining surfaces, more may be used if desired. For example, in the specific embodiment illustrated a fourth retaining surface is provided by the beveled portion 37 of the hub.

Although I have used specific terms in describing the various portions of the rotor, it will be understood that the structure can be described in other ways and various portions of the rotor can be replaced by equivalent structures. For example, the retaining surfaces for the tubes which are provided by the continuously extending

cylindrical walls

20 and 24 can be provided by relatively short cross ribs or the like which extend only across the openings in the frusto-conical wall 22 between the side walls 31. The frusto-conical wall could then be joined directly to the outer wall 27. Also, the tenn recess is meant to include any space into which the tube can be inserted longitudinally and in which the tube is restrained against transverse movement in any direction and is not to be limited to a space which is defined by longitudinally extending walls.

While in the foregoing specification a detailed description of a specific embodiment of the invention was set forth for the purpose of illustration, it is to be'understood that many of the details herein given may be varied considerably by those skilled in the art without departing from the spirit and scope of the invention.

I claim:

1. A molded centrifuge rotor comprising a generally circular generally horizontally extending central hub portion adapted to be connected to a centrifuge and an annular tube-holding portion extending outwardly from the hub portion, the tube-holding portion being provided with a plurality of recesses extending outwardly from the hub portion, each recess adapted to receive an elongated tube and being defined by a pair of opposed side walls, a bottom wall extending between the side walls and being spaced from the hub portion, and a top wall spaced upwardly from the bottom wall to permit a tube to be inserted between the top wall and the bottom wall, the top wall'extending between the side walls in vertical alignment with the spacing between the bottom wall and the hub portion, no portion of the top wall being in vertical alignment with any portion of the bottom wall whereby a tube may be secured against transverse movement within each recess and the rotor may be formed in one operation by molding.

2. The rotor of claim 1 in which the hub portion is generally planar and has top and bottom surfaces and the tube-holding portion is generally frusto-conical, the recesses extending radially outwardly and downwardly from the hub portion at circumferentially spaced locations along the periphery of the hub portion.

3. The rotor of claim 2 in which the bottom wall of each recess has an inner end spaced from the hub portion and an outer end, the rotor including a second top wall for each recess spaced upwardly from the bottom wall to permit a tube to be inserted between the second top wall and the bottom wall, each second top wall extending between the side walls of the associated recess outwardly of the outer end of the associated bottom wall so that no portion of the second top wall is vertically aligned with any portion of the bottom wall.

4. The rotor of claim 3 in which the end wall for each recess is provided by a continuous generally cylindrical outer wall.

'5. The rotor of claim 1 including an end wall for each recess engageable with the outer end of a tube received by the recess for preventing outward movement of the tube.

6. The rotor of claim 5 in which the end wall for each recess is spaced from the bottom wall for the recess, the rotor including a second top wall for each recess spaced upwardly from the bottom wall to permit a tube to be inserted between the second top wall and the bottom wall, each second top wall extending between the side walls of the associated recess in vertical alignment with the spacing between the bottom wall and the end wall of the associated recess, no portions of the second top wall and the bottom wall for each recess being in vertical alignment. 4

7. The rotor of claim 1 including connecting portions extending between the side walls of each adjacent pair of recesses.

8. The rotor of claim 7 in which the top wall for each recess is provided by a continuous circularly extending wall joined to the side walls of each recess and too said connecting portions.

9. The rotor of claim 1 in which every part which is spaced vertically above another part is not aligned vertically with the other part.

10. A molded centrifuge rotor comprising a generally circular generally horizontally extending central hub portion adapted to be connected to a centrifuge and having upper and lower surfaces and a generally annular tube-holding portion extending outwardly and downwardly from the hub portion, the tube-holding portion having a generally frusto-conical wall provided with a plurality of openings, each opening in the frustoconical wall extending in a vertical plane passing through the center of the hub portion, a generally U- shaped tube-supporting wall extending downwardly from the frusto-conical wall at each opening therein and having an inner end spaced from the hub portion and an outer end, a pair of spaced-apart cross members extending across each opening in the frusto-conical wall, one of the cross members of each pair being positioned vertically above the space between the inner end of the associated tube-supporting wall and the hub portion and'the other cross member of each pair being po- I sitioned outwardly of the outer end of the associated tube-supporting wall, no portion of said one cross member being in vertical alignment with any portion of either the associated tube-supporting wall or the hub portion and no portion of said other cross member being in vertical alignment with any portion of the associated tube-supporting wall whereby an elongated cylindrical tube may be secured against transverse movement in each opening in the frusto-conical wall and the rotor may be formed in one operation by molding.

' 11. The rotor of claim 10 in which each of the cross members has an arcuate lower surface for mating with the other surface of a cylindrical tube.

12. The rotor of claim 10 including a generally circularly extending outer wall spaced outwardly of said other cross members and secured to the frusto-conical wall for preventing outward movement of the tubes beyond the outer wall as the rotor is rotated.

13. The rotor. of claim 10 in which said one cross member of each pair is provided by a continuous generally cylindrical wall extending upwardly from the frusto-conical wall above the inner ends of the tubes received by the openings.

14. The rotor of claim 10 in which said one cross members are provided by a first continuous circularly extending rib projecting upwardly from the frustocorlical wall and said other cross members are provided by a second continuous circularly extending rib projecting upwardly from the frusto-conical wall.

15. The rotor of claim 10 in which every part which is spaced vertically above another part is not aligned vertically with the other part.

16. A molded centrifuge rotor comprising a generally circular central hub portion adapted to be connected to a centrifuge and an annular tube-holding portion extending outwardly from the hub portion, the tubeholding portion being provided with a plurality of recesses extending outwardly from the hub portion, each recess adapted to receive an elongated tube and being defined by a pair of opposed side retaining means on the tube-holding portion for restraining sideways movement of the tube, bottom retaining means on the tubeholding portion having an inner end spaced from the hub portion for restraining downward movement of the tube, and top retaining means on the tube-holding portion positioned inwardly of the inner end of the bottom retaining means and outwardly of the hub portion for restraining upward movement of the tube, no portion 'of the top retaining means being in vertical alignment with any portion of either the associated bottom retaining means or the hub portion whereby a tube may be secured against transverse movement within each recess and the rotor may be formed in one operation by molding.

17. The rotor of claim 16 in which every part which is spaced vertically above another part is not aligned vertically with the other part.

Claims

1. A molded centrifuge rotor comprising a generally circular generally horizontally extending central hub portion adapted to be connected to a centrifuge and an annular tube-holding portion extending outwardly from the hub portion, the tube-holding portion being provided with a plurality of recesses extending outwardly from the hub portion, each recess adapted to receive an elongated tube and being defined by a pair of opposed side walls, a bottom wall extending between the side walls and being spaced from the hub portion, and a top wall spaced upwardly from the bottom wall to permit a tube to be inserted between the top wall and the bottom wall, the top wall extending between the side walls in vertical alignment with the spacing between the bottom wall and the hub portion, no portion of the top wall being in vertical alignment with any portion of the bottom wall whereby a tube may be secured against transverse movement within each recess and the rotor may be formed in one operation by molding.

5. The rotor of claim 1 including an end wall for each recess engageable with the outer end of a tube received by the recess for preventing outward movement of the tube.

6. The rotor of claim 5 in which the end wall for each recess is spaced from the bottom wall for the recess, the rotor including a second top wall for each recess spaced upwardly from the bottom wall to permit a tube to be inserted between the second top wall and the bottom wall, each second top wall extending between the side walls of the associated recess in vertical alignment with the spacing between the bottom wall and the end wall of the associated recess, no portions of the second top wall and the bottom wall for each recess being in vertical alignment.

10. A molded centrifuge rotor comprising a generally circular generally horizontally extending central hub portion adapted to be connected to a centrifuge and having upper and lower surfaces and a generally annular tube-holding portion extending outwardly and downwardly from the hub portion, the tube-holding portion having a generally frusto-conical wall provided with a plurality of openings, each opening in the frusto-conical wall extending in a vertical plane passing through the center of the hub portion, a generally U-shaped tube-supporting wall extending downwardly from the frusto-conical wall at each opening therein and having an inner end spaced From the hub portion and an outer end, a pair of spaced-apart cross members extending across each opening in the frusto-conical wall, one of the cross members of each pair being positioned vertically above the space between the inner end of the associated tube-supporting wall and the hub portion and the other cross member of each pair being positioned outwardly of the outer end of the associated tube-supporting wall, no portion of said one cross member being in vertical alignment with any portion of either the associated tube-supporting wall or the hub portion and no portion of said other cross member being in vertical alignment with any portion of the associated tube-supporting wall whereby an elongated cylindrical tube may be secured against transverse movement in each opening in the frusto-conical wall and the rotor may be formed in one operation by molding.

11. The rotor of claim 10 in which each of the cross members has an arcuate lower surface for mating with the other surface of a cylindrical tube.

13. The rotor of claim 10 in which said one cross member of each pair is provided by a continuous generally cylindrical wall extending upwardly from the frusto-conical wall above the inner ends of the tubes received by the openings.

14. The rotor of claim 10 in which said one cross members are provided by a first continuous circularly extending rib projecting upwardly from the frusto-conical wall and said other cross members are provided by a second continuous circularly extending rib projecting upwardly from the frusto-conical wall.

16. A molded centrifuge rotor comprising a generally circular central hub portion adapted to be connected to a centrifuge and an annular tube-holding portion extending outwardly from the hub portion, the tube-holding portion being provided with a plurality of recesses extending outwardly from the hub portion, each recess adapted to receive an elongated tube and being defined by a pair of opposed side retaining means on the tube-holding portion for restraining sideways movement of the tube, bottom retaining means on the tube-holding portion having an inner end spaced from the hub portion for restraining downward movement of the tube, and top retaining means on the tube-holding portion positioned inwardly of the inner end of the bottom retaining means and outwardly of the hub portion for restraining upward movement of the tube, no portion of the top retaining means being in vertical alignment with any portion of either the associated bottom retaining means or the hub portion whereby a tube may be secured against transverse movement within each recess and the rotor may be formed in one operation by molding.