US3536252A

US3536252A - Apparatus for centrifuging

Info

Publication number: US3536252A
Application number: US630140A
Authority: US
Inventors: Thomas H Oster
Original assignee: Ford Motor Co
Current assignee: Ford Motor Co
Priority date: 1967-04-11
Filing date: 1967-04-11
Publication date: 1970-10-27
Anticipated expiration: 1987-10-27

Description

United States Patent Inventor Appl. No

Filed Patented Assignee APPARATUS FOR CENTRIFUGING 7 Claims, 2 Drawing Figs.

U.S. Cl.....

Int. Cl 1304b 5/02, B04b 9/ 1 2, B04b 9/ 14 Field ofSearclI 233/11, 17. 26, 25

Primary Examiner- Henry T. Klinksiek ABSTRACT: A centrifuge apparatus comprising a rotor, an annulus in spaced coaxial relationship to the rotor and sur rounding the latter, and at least one centrifugatable material cylindrical container or tube interposed between the peripheral or external bearing surface of the rotor and the opposed internal cylindrical bearing surface of the annulus. A retention means maintains the cylindrical container or tube for rotation about its longitudinal axis in the interposed relationship and against displacement axially of the rotor, while allowing free rolling engagement of the container or tube with the internal cylindrical surface of the annulus.

Patented Oct. 27, 1970 3,536,252

Sheet 1 012 THOMAS H. OSTER INVENT ATI'ORN EYS Patented Oct. 27, 1970 Sheet THOMAS H. 05 T51? ATTORN EYS APPARATUS FOR CENTRIFUGING This application is a continuation of application Ser. No. 4l7,702, filed Dec. 1 l, I964 and now abandoned.

This invention relates to centrifuging apparatus operable in supercentrifugal or ultracentrifugal speed ranges and to a method of centrifuging substances at supercentrifugal or ultracentrifugal speeds.

In general, centrifuges designed to operate at very high speeds to perform centrifugal separations impossible in standard centrifuges are complex, precision-made and expensive pieces of apparatus. For example, the rotor in which the centrifuging cells are mounted must be precision machined, stress relieved, dynamically balanced and precisely mounted. High speed rotation is achieved by driving the rotor with an air turbine, and elaborate bearing systems, including cooling means, are utilized to support the rotor for such high speed rotation. The very complexity of the apparatus and the skill required in its operation has limited the use of such supercentrifuges or ultracentrifuges to the advanced research laboratory.

It is an object of the present invention to provide a centrifuge which may be operated to perform centrifuging separations impossible in standard centrifuges, but which does not require the prohibitively costly components found in laboratory type supercentrifuges or ultracentrifuges. Centrifuges embodying the present invention may be constructed of readily available and relatively inexpensive materials and components that do not require more than ordinary mechanical skill to assemble into a workable and usable apparatus.

The basic components of the centrifuge herein disclosed comprise a rotor or disk, a ring in spaced coaxial relationship to the disk, a plurality of cages secured to the periphery of the disk in interposed relationship to the disk and ring, and centrifugable material containers or tubes carried within the cages. Each tube is mounted for free rotation about a longitudinal axis which substantially parallels the axis of the disk. Drive means are provided that are operable to rotate the disk relative to the coaxial ring or to rotate the disk and the ring at independently controlled speeds of rotation.

The materials used in the construction of the present centrifuge are those found in ordinary machines having rotating parts. The disk and coaxial ring are adapted to be machined or cast from steel or iron alloys such as used for flywheels or pulleys designed to be rotated at speeds up to 10,000 r.p.m. The tubes for containing the centrifugable substances are adapted to be manufactured from tubing made of medium carbon semihard steel. The drive means are adapted to comprise standard shaft components mounted in ordinary bearings and to be driven by commercially available electric. fluid or air motors. The high speed turbines and bearing systems used to drive and support the rotor of laboratory type supercentrifuges or ultracentrifuges are not required.

Other objects, advantages and features of this invention will be made more apparent as this description proceeds, particularly when considered in connection with the accompanying drawing, wherein:

FIG. 1 is a side elevation, in part fragmentary and in part sectional, illustrating the basic components of a centrifuge constructed and arranged in accordance with a preferred embodiment of the present invention;

FIG. 2 is a sectional view taken substantially on the line 2-2 of FIG. 1;

FIG. 3 is a fragmentary view in part similar to FIG. 2 illustrating a second embodiment of the present invention;

FIG. 4 is a sectional view taken substantially on the line 4-4 of FIG. 3

Referring now to FIGS. 1 and 2, the centrifuge embodying the present invention comprises a rotor or disk 11 which may be machined from a steel plate or cast from suitable metal of a quality comparable to that used for flywheels, high speed pulleys or the like. The rotor or disk 11 is keyed, as at 12, or otherwise coupled to a shaft 13 of an electric motor 14.

The rotor or disk 11 is rotatable within a coaxial ring 15 made of metal comparable to that used for the rotor or disk ll. The inner circumferential surface l6'or ring 15 is spaced from the cylindrical peripheral surface 17 of the rotor or disk 11. The ring 15 is carried on a yoke 18 coupled to the shaft 19 of a second electric motor 21.

Although the two motor shafts l3 and 19, the rotor or disk 11 and the ring 15 are illustrated as being rotatable about a common horizontal axis or coincident horizontal axes, it will be understood that the apparatus will operate as well about a vertical axis of rotation.

Secured to the periphery 17 of the rotor or disk 11 are a plurality of substantially U-shaped channel sections 22. The longitudinal axis of each channel section parallels the axis of rotation of the rotor or disk 11. The channel sections open outwardly toward the ring 15. Each channel section functions as a cage adapted to receive a tube 23.

The tubes 23 are thin-walled and of an external diameter less than the depth and width of the channel sections 22. The tubes 23 may be formed of metal commonly known as drillrod stock, a medium carbon semihard steel. The tubes 23 are held against axial displacement from the channel sections by pins or wires 24 that extend across the open ends of the channel sections 22.

From the foregoing, it will be seen that the tubes are loosely held within the cages or channel sections 22 against substantial axial or peripheral displacement relative to the rotor or disk 11. As the rotor or disk 11 is rotated, the tubes 23 are thrown outwardly into rolling engagement with the inner circumferential surface of the coaxial ring 15. This rolling engagement causes the tubes 23 to be rotated about their own axes at a highly multiplied r.p.m. As will be more fully explained,'the ultimate speed of rotation of each tube 23 is dependent on the speed or rotation of the motor or disk 11 relative to the coaxial ring 15. Before setting up illustrative problems to demonstrate this, brief reference will be made to the embodiment of the invention shown in FIGS. 3 and 4.

In the embodiment of the invention illustrated in FIGS. 3 and 4, the channel sections or cages 22 are not used. The tubes, herein designated 25, are of a diameter such that they fit tightly between the periphery 17 of the rotor or disk 11 and the inner circumferential surface 16 of ring 15. The tubes 25 are thus in rolling engagement with both the periphery of the rotor or disk II and the inner circumferential surface of the ring 15. The tubes are held against axial displacement by rods or wires 26 which extend through the tube walls outwardly of the side surfaces of the rotor or disk II and ring is.

Returning now to the embodiment of the invention illustrated in FIGS. l and 2, several illustrative examples may be set up to demonstrate the centrifugal speeds and forces obtainable with an apparatus enbodying the present invention.

For the purpose of the calculations to be used to demonstrate the centrifugal speeds and forces obtainable, the following dimensions may be considered representative:

Diameter of disk or rotor 11: 9 inches Internal diameter of ring l5: [0 inches Mean diameter of tubes 23: .34 inches Inner circumferential length of ring 15: 31.416 inches Diameter of path travelled by center of tubes 23 orbiting about axis of rotation of disk 1 l: 9.66 inches CASE I speed of rotor or disk II: 7,200 r.p.m.

Speed or ring 15: 0 r.p.m.

The velocity of a tube 23 rolling over internal circumference 16 of ring 15 in feet per second:

31.416 7,200 T X- m- -314.16 ft./sec. Centrifugal force acting on unit mass of contents of tube 23 due to rotation about its own axis:

my 1 X31416 F Tg 17 32 2 CASE ll Speed of rotor l 1: 7,200 r.p.m. Speed of ring 15: 7,200 r.p.n1. Velocity of tube 23 about axis of rotation of rotor 11:

Case I above demonstrates the centrifugal force acting on a unit mass of the contents of a tube 23 due to the rotation of the tube 23 about its own axis when the rotor or disk ll is rotated at 7200 rpm. and ring 15 is held stationary.

Case ll demonstrates the centrifugal force action on a unit mass of the contents of a tube 23 when there is no rotation of the tube 23 about its own axis. This occurs when the rotor 11 and disk 15 are rotated by the respective motors l4 and 21 at the same speed. The centrifugal force acting on the contents of a tube 23 is then solely that caused by the orbital movement of the tube 23 about the axis of rotation of the rotor 11.

From the foregoing it is believed readily apparent that the centrifugal force acting on the contents of a tube 23 readily may be controlled by selected rotation of the ring 15. This is demonstrated by case lll.

CASE lll Speed or rotor 11 7,200 rpm.

Speed of ring 15 3,600 rpm.

(Rotor and disk direction of rotation the same.)

Velocity of tube rolling over circumferential surface 16 of ring 15 is one-half that of case I or l 57.08 ft./sec.

Centrifugal forceacting on contents of tube 23 due to the rotation of tube about its own axis:

Centrifugal force acting on contents of tube 23 due to orbital movement of tube about the axis of rotation of rotor 11 remains the same as case ll or.7,l06 g.

CASE IV In order that a flow of material be created through the tube 23, the material hurled against the tube wall must be loosened by rotating the tube about its own axis at a speed at which the centrifugal force on the contents of the tube due to the rotation of the latter becomes substantially less than the centrifugal force on the contents resulting from the movement of the tube about the orbital axis of the axis of rotation of the rotor 11.

Since the centrifugal force due to the orbital movement at 7,200 r.p.m. of the rotor or disk 11 has been calculated as being approximately 7,100 g., it will be assumed that rotation of the tube 23 should not result in a centrifugal force in excess of 5,000 g. on the contents of the tube due to rotation of the latter about its own axis. The problem then becomes simply a reverse calculation to determine the speed at which ring must be rotated to obtain 5,000 g. on the tube contents.

v.=47.21 ftJsec.

Speed of ring 15 must then be 3l4.l6 47.2l= 266.95 ftJsec. or approximately 6,400 r.p.m.

It will be understood that the case lV example is only for the purpose of illustrating the method of calculation. The 5,000 g. assumption is an empirical assumption and the actual value would depend on the nature of the centrifugable substance involved.

If the direction of rotation of ring 15 relative to the direction of rotation of the rotor or disk 11 is reversed, even greater centrifugal force on the contents of the tube 23 may be achieved than illustrated in case I. But under the dimensions set forth and the material described for the tubes 23, it has been found the internal stresses on the tubes themselves are such that failure of the tubes is imminent when the centrifugal force exceeds 200,000 g. The use of tube material of higher strength characteristics than medium carbon semihard steel would affect the maximum forces obtainable.

It has been found that friction effects are negligible in the apparatus as described. As a result little heat is generated by the tubes as they roll against the surface of ring 15 and against the driving surfaces of the respective channel sections 22. The apparatus thus operates without the necessity of providing the elaborate cooling accessories usually required in supercentrifuges to prevent heat build-up that would effect the centrifuging action.

it will be apparent that with an apparatus constructed in accordance with the embodiment of FIGS. 1 and 2, there must be rotation of the rotor or disk 11 in order to achieve a centrifuging action. With the embodiment of FIGS. 3 and 4, rotation of either the rotor 11 or the ring 15 will result in orbital movement of the tubes 23 about the axis of rotorll and rotation ofeach tube 23 about its own axis. It is believed, however, unnecessary to demonstrate the centrifugal forces that may be achieved since the same principles apply as were demonstrated with respect to the embodiment of H68. 1 and 2.

It will be understood that the invention is not to be limited to the exact construction shown and described, but that various changes and modifications may be made without departing from the spirit and scope of the invention, as defined in the appended claims.

lclaim:

l. A centrifuge comprising a rotor,

an annulus surrounding said rotor in spaced relationship thereto,

drive means connected to at least said rotor for imparting rotation thereto,

a tube for the material to be centrifuged,

said tube being interposed between the peripheral surface of said rotor and an opposed internal cylindrical surface of said annulus with the longitudinal axis of said tube substantially paralleling the axis of rotation of said rotor,

and retention means on said rotor constructed and arranged to maintain said tube for rotation about its longitudinal axis in said interposed relationship and against substantial displacement axially of the rotor,

said retention means having nonaxial bearing engagement with said tube to prevent axial separation of the rotor and the tube and to allow the latter to move radially of said rotor freely into rolling engagement with the internal cylindrical surface of said annulus, and

the rate of rotation of said tube resulting from rolling engagernent with said annulus surface being a function of the circumferential length of the tube and the length of the annulus surface over which said tube rolls per each revolution of said rotor.

2. A centrifuge according to claim 1, in which: both the rotor and the annulus are operable by drive means, and said drive. means being independently operable to selectively rotate said rotor and annulus at the same or at different rates of rotation to cause relative rotary movement therebetween.

3. A centrifuge according to claim 2, in which: when said rotor and annulus are rotated in the same direction at the the material in said tube becomes a function of the rate of rotation of said rotor and said annulus and the distance of the center of the tube from the axis of rotation of said rotor and said annulus.

4. A centrifuge according to Claim 1, in which: the retention means comprises a cage secured to the periphery of the rotor, and said cage being open on the side thereof facing the annulus surface to accommodate the radially outwardly movement of the tube into engagement with the annulus surface.

5. A centrifuge comprising a first member mounted for rotation about a fixed axis and having an external cylindrical bearing surface,

a second member around said first member also mounted for rotation and having an internal cylindrical bearing surface the axis of which coincides with said fixed axis,

said internal cylindrical bearing surface being in spaced opposed relation to said external cylindrical bearing surface,

drive means connected to said members operable to rotate the latter in the same or opposite directions at independently controlled rates of rotation about said fixed axis,

at least one cylindrical member having means adapted to receive centrifugatable matter,

said cylindrical member being interposed between the external cylindrical surface of said first member and the internal cylindrical surface of said second member,

and retention means on at least one of said members retaining said cylindrical member against axial displacement from between said first and second members, and

said cylindrical member being frictionally engaged with at least one of said first or second members for (1) rotation about its own axis upon relative rotation of said first and second members in opposite directions, or for (2) com bined rotation about its own axis and orbital movement about said fixed axis upon rotation of said first and second members at different rates of speed, or for (3) orbital movement about said fixed axis upon rotation of said first and second members at a common rate and direction of movement.

6. A centrifuge comprising a disk member mounted for rotation about a fixed axis,

a ring member encircling said disk member in spaced relationship thereto and having an internal cylindrical surface the axis of which coincides with said fixed axis,

means selectively operable to rotate said disk member relative to said ring member while holding the latter stationary or to rotate both of said members in the same or opposite directions at independently controlled rates of rotation about said fixed axis.

cylindrical members having means adapted to receive centrifugatable matter,

and retention means carried on the peripheral surface of said disk member holding said cylindrical members inter posed between the periphery of said disk member and the internal surface of said ring member,

said retention means being in nonaxial bearing engagement with said cylindrical members to prevent axial separation of said cylindrical members from said disk member, and

each of said cylindrical members being frictionally engaged with the internal surface of said ring member for simultaneous rotation about its own axis and orbital movement about said fixed axis upon; 1. said disk member being rotated and said ring member being held stationary, or 2. said disk member and said ring member being rotated in opposite directions at selected speeds.

7. A centrifuge comprising a disk member,

a ring member encircling said disk member,

said ring member having an internal cylindrical surface in spaced concentric relationship to the peripheral surface of said disk member,

means connected to said members selectively operable to rotate said disk member relative to said ring member while holding the latter stationary or to rotate both in the same or opposite directions at independently controlled rates of rotation, cylindrical members having means adapted to receive centrifugal matter,

and cage means carried on said disk member holding said cylindrical members in juxtaposition to the peripheral surface thereof against substantial axial and peripheral displacement and for radial movement outwardly from the axis of rotation into rolling engagement with the internal cylindrical surface of said ring member,

the radial movement of the cylindrical members outwardly relative to the axis of rotation being limited only by the extent of the space between the in ernal cylindrical surface of said ring member and the peripheral surface of said disk member, and

each of said cylindrical members being centrifugally urged outwardly into said rolling engagement with said ring member surface and being rotated about its own axis and orbited about the axis of said disk member upon rotation of the latter with said ring member being held stationary or having a retrograde motion relative to said disk member.