US3363834A - Centrifuge rotors - Google Patents

Description

\ Filed Aug. 9, 1

1968 R. A. CHAPMAN ETAL 3,36 4

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R. vA. CHAPMAN ETAL 3,363,834

- CENTRIF'UGE ROTORS' Jan. 16,1968 7 2 Sheets-Sheet 2 Filed Aug. O, 1965 @JMZQM United States Patent Ofiice 3,363,834 Patented Jan. 16, 1968 3,363,834 CENTRIFUGE ROTORS Richard A. Chapman, Scituate, Robert R. Daniels, West Newton, and Gerald D. Fox, Quincy, Mass, assignors to International Equipment Company, Needhaln Heights, Mass., a corporation of Massachusetts Filed Aug. 9, 1965, Ser. No. 478,270 6 Claims. (Cl. 23326) ABSTRACT OF THE DISCLOSURE Rotors for ultracentrifuges, each characterized by a substantial reduction in its inertia without reduction in the speed at which it may be safely rotated as compared with a rotor of the same material and for use with the same number of containers of the same volumetric capacity.

The present invention relates to centrifuge rotors that have substantially reduced inertia at and are adapted to be rotated at the same or higher speeds than presently available rotors made from the same metal and having the same number of cavities of the same dimensions.

The size and, accordingly, the weight of a centrifuge rotor depends on the number of container-receiving cavities which it has and on their dimensions and also on the maximum rate at which a rotor is to be rotated. By way of example, it may be desired to centrifuge, for thirty minutes at 15,000 r.p.m., a relatively large volume of a liquid making desirable the use of containers in the 500 ml. capacity range. Such a rotor, as represented by model 865, manufactured by International Equipment Company of Needham, Mass. weighs fifty-three and three-quarters pounds. The time required to bring such a rotor up to speed is in the thirty-to-forty minute range. Deceleration intervals are approximately double the acceleration time of any rotor.

It will be apparent that the rotor acceleration and deceleration times are real limitations on the number of runs per diem that can be made with a centrifuge and entail, for any one run, a substantial waste of a technicians time. As a consequence, since acceleration and deccleration times are a function of rotor weight, the reduction of the inertia of centrifuge rotors is an important objective of the invention.

It will be appreciated that reduced inertia can be achieved simply by reducing the weight of any rotor. This weight reduction would be of little value if attended by a drop in the maximum speed at Which the rotor could be safely rotated, Another objective of the invention, is accordingly, to attain reduced inertia of a rotor while maintaining or increasing the maximum safe speeds at which it may be rotated in relation to those recommended for centrifuge rotors of conventional construction made from the same metal and having the same number of cavities of the same dimensions.

The above principal objectives are attained, in accord ance with the invention, by providing a centrifuge rotor with a series of peripheral portions with each such portion having an upwardly opening, cylindrical, containersupporting cavity disposed with its axis inclined upwardly and inwardly towards the axis of the rotor. The containerreceiving portions are uniformly spaced with reference to the rotor axis and to each other. The rotor also has a central portion for attachment to a centrifuge drive with which the upper ends of the container-receiving portions merge and which includes an outwardly projecting web structure joining the container-receiving portions together, and a series of radially disposed ribs, one for the lower end of each container-receiving portion and joined thereto and extending upwardly from the bottom thereof. The container-receiving portions are approximately cylindrical,

except where they are connected to the central portion.

In the accompanying drawings, there is shown an illustrative embodiment of the invention from which these and other of its objectives, novel features, and advantages Will be apparent.

In the drawings:

FIGURE 1 is a top plan view of a centrifuge rotor in accordance with the invention,

FIGURES 2 and 3 are sections taken approximately along the indicated lines 2-2 and 33 respectively, of FIGURE 1, and

FIGURE 4 is a bottom plan view of the rotor.

The centrifuge rotor illustrated by the drawings is shown as having a plurality of peripheral portions 10 each having a cylindrical cavity 11 dimensioned to receive a container of particular dimensions and having its axis inclined upwardly and inwardly towards the axis of the rotor and uniformly spaced with reference thereto and to each other. The container may be of the type fully detailed in the co-pending application of David F. Mitchell, Ser. No. 349,837, filed Mar. 6, 1964, now Patent No. 3,265,296. While such containers are available in other sizes, it may be assumed to have a capacity in the neighborhood of 500 ml.

The rotor is shown as having a central portion 12 provided with an axial bore 13 to receive the spindle of a centrifuge drive and the upper ends of the containerreceiving portions 10 merge therewith. The central portion 12 has outwardly projecting Webs 14 joining the upper ends of the container-receiving portions 10 and radially disposed ribs 15, one for each container-receiving portion 10 and connected thereto from the bottom thereof upwardly to its junction with the central portion 12. The ribs 15 are shown as including relatively narrow, radially disposed supporting portions 15A extending below and under the bottom ends of the container-receiving portions 10 and these may be ground as necessary to balance the rotor. The container-receiving portions 10, except for their connections with the central portion 12 are shown as approximately cylindrical and the Width of the ribs 15 is less than the diameter of the container-receiving cavities 11.

In practice, approximately the upper half of each contamer-receiving portion is joined to the central portion 12 and each rib 15 extends lengthwise of approximately the lower half of the container-receiving portion 10 to which it is joined. The webs 14 are downwardly and inwardly curved and merge with the central portion 12 approximaiely midway between its ends and the lower part of the central portion 12 is downwardly and inwardly tapered.

The centrifuge rotor shown in the drawings has the same maximum diameter, the same maximum height, the same number of cavities of the same diameter and depth as the rotors manufactured by International Equipment Company identified above as Model #865. In contrast With the Model #865 weight of fifty-three and threequarters pounds, the rotor shown in the drawings weighs fourteen and one-half pounds with an acceleration period to 15,000 rpm. in the neighborhood of ten minutes. If made of the same metal as model #865, an aluminum alloy identified as 2014-T6 instead of an aluminum alloy identified as 356-T6, its maximum rate of rotation would be in the order of 20,000 rpm. Different alloys would permit yet higher rotor speeds.

Centrifuges that can be operated to provide rotor speeds above 15,000 rpm. are regarded as high speed centrifuges and as ultracentrifuges if their rotor receiving chambers are evacuated and their rotor speeds may be in the neighborhood of 25,000 rpm. Unless a rotor in accordance with the invention is provided with a skirt or shield or unless it is used in an ultracentrifuge, for ex- 3 ample, a model B35 or B60 made by International Equipment Company of Needham, Mass, its use would result in objectionable air turbulence.

It will be appreciated from the foregoing that centrifuge rotors in accordance with the invention meet the dual requirements of a substantial reduction in acceleration and deceleration times and strength such that they may be rotated at the same or increased speeds as compared with conventional rotors designed for use with the same number or" containers of the same dimensions.

We claim:

1. An ultracentrifuge rotor of the fixed angle type comprising a series of upwardly and inwardly inclined peripheral portions, each portion having a downwardly and inwardly inclined upper face and a closed bottom, closed sidewall, cylindrical container receiving cavity opening upwardly through the face and with its axis upwardly and inwardly inclined towards the axis of the rotor, the remote edge portions of the cavities spaced above a plane inclusive of the proximate edge portions of said cavities thereof, said portions and said cavities being uniformly spaced with reference to the rotor axis and to each other, and a central portion for attachment to a centrifuge drive and into which corresponding parts of the upper ends of said container receiving portions merge and which includes outwardly projecting webs, one between each two adjacent container-receiving portions with its outer edge approximately tangential with respect thereto and joining outwardly disposed proximate parts of the upper ends thereof in zones extending above and below said plane, and of a length at least equal to the cavity radius, and said central portion also including radially disposed ribs, one for each container-receiving portion and joined thereto and extending upwardly from its bottom for the full length of its lower nd and merging into said webs.

Z. The rotor of claim 1 in which the under surfaces of the webs taper downwardly and inwardly.

3. The rotor of claim 1 in which the under surfaces of the webs taper downwardly and inwardly to the zone in which the container-receiver portions merge with the central portion.

4. The rotor of claim 3 in which the merger zone is approximately midway between the ends of the containerreceiving portions.

5. The rotor of tapers downwardly claim 3 in which the central portion and inwardly below the merger zone. 6. The rotor of claim 2 in which the rotor includes relatively narrow, radially disposed, and downwardly projecting portions below the container-receiving portions.

References Cited UNITED STATES PATENTS 8/1948 Greomeier 23326 1/1955 Allen et a1. 233-26 OTHER REFERENCES HENRY T. KLINKSIEK, Primary Examiner.

M. CARY NELSON, Examiner.

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