Centrifuge

Abstract

Test tube retainers are mounted on annular supports on opposite sides of the axis of rotation of a rotor. The annular supports have a chamber adapted to contain a liquid. Oppositely disposed chambers communicate with one another by a conduit means. The tube retainers apply a force to the liquid whereby centrifugal reaction forces on the rotor are balanced.

Description

This invention is directed to a centrifuge structurally interrelated in a manner so that centrifugal reaction forces on a motor driven rotor are balanced.

The main drive motor is mounted on support structure. A rotor is connected to the motor for rotation about a first axis. Two annular supports are mounted on the rotor for rotation therewith about the first axis.

The annular supports are mounted on the rotor on opposite sides of said first axis. The annular supports are rotatably supported by the rotor for rotation about a second axis perpendicular to said first axis. Each annular support has a chamber for containing a liquid. Conduit means provides communication between the chambers. A tube retainer is supported by each annular support. A means is associated with each tube retainer for applying pressure to the liquid in the chamber of the annular support associated therewith.

The centrifuge constructed in accordance with the present invention has test tube support structure which is hydraulically balanced. As a result thereof, it is no longer necessary to perform the tedious, time consuming chore of weighing the contents of the test tubes on a balance scale to be certain that the respective test tubes contain the same weight specimen and/or making weight adjustments on the centrifuge. Thus, balance of centrifugal reaction forces on the rotor and/or motor is automatically attained up to a predetermined amount.

It is an object of the present invention to provide a hydraulically balanced centrifuge which automatically compensates for imbalance between oppositely disposed test tube support structures.

Other objects will appear hereinafter.

For the purpose of illustrating the invention, there is shown in the drawings a form which is presently preferred; it being understood, however, that this invention is not limited to the precise arrangements and instrumentalities shown.

FIG. 1 is a vertical sectional view through a centrifuge embodying the present invention.

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

FIG. 3 is a sectional view taken along the line 3--3 in FIG. 2.

FIG. 4 is a sectional view of an alternative support structure.

Referring to the drawing in detail, wherein like numerals indicate like elements, there is shown in FIG. 1 a centrifuge designated generally as 10 and embodying the present invention. The structural details of the centrifuge, except for the balancing feature, as illustrated in FIG. 1 are merely exemplary of a wide variety of different centrifuges which may incorporate the present invention.

The centrifuge 10 as shown in the drawing includes a base 12 supporting a variable speed motor 14 having an output shaft 16. A rotor 18 is mounted on the shaft 16 and retained thereon in any convenient manner.

The rotor 18 is rotatably driven by the motor 14 about the longitudinal axis of shaft 16. For purposes of illustration, the centrifuge 10 is of the type adapted to accommodate two test tubes. It is within the scope of the present invention to utilize a rotor adapted to support a plurality of oppositely disposed sets of structure for supporting a plurality of sets of test tubes such as 4, 6, 8, etc. test tubes.

The rotor 18, as illustrated, is provided with test tube support structure designated generally as 17 and 19 on opposite sides of the axis of shaft 16. Each of the support structures 17 and 19 is identical. Accordingly, only support structure 19 will be described in detail with corresponding primed numerals being provided for corresponding elements on support structure 17.

Referring to FIGS. 2 and 3, the rotor 18 terminates in a pair of arms 20 and 21. An annular support 22 is provided with outwardly directed projections 24 and 26. The longitudinal axis of projections 24 and 26 is perpendicular to longitudinal axis of the motor output shaft 16. Projection 24 is rotatably supported by bearing 28 in arm 20. Projection 26 is rotatably supported by bearing 30 in arm 21.

A tube retainer 32, open at one end and closed on the other end, is slidably supported by the bottom wall of the annular support 22. In order to provide a seal, the bottom wall of support 22 may be provided with an 0-ring seal in contact with the outer periphery of the tube retainer 32. See FIG. 2.

The annular support 22 is hollow and contains a chamber therein. Within the chamber, the tube retainer 32 is provided with a flange 34 which overlies the ring-shaped spacer 36. Spacer 36 has a tight sliding fit with the juxtaposed coaxial surfaces of the annular support 22 and tube retainer 32 while being movable in an axial direction with respect thereto. An incompressible liquid 38, such as mercury, is provided within the chamber below the spacer 32. A means is provided to communicate the chamber of annular support 22 with the chamber of annular support 22'. Such last mentioned means is preferably in the form of a flexible conduit 40 which, as shown, contains a loop and extends between the respective chambers below the shield 42 on the rotor 18. The central portion of conduit 40 extends along-side the shaft 16 but may extend through or over shaft 16. The retainer 32 is adapted to support a test tube 44. The retainer 32' is adapted to support a test tube 46.

A guard ring 48 may be provided radially outwardly from the test tube support structures 17 and 19. Ring 48 is supported at spaced locations by arms 50 and 50' connected to a support ring 52 on the base 12 and coaxial with the motor 14.

The operation of the centrifuge 10 is as follows: A liquid 54 is placed in the test tube 44 up to the level 56. A similar liquid is placed in the test tube 46 up to a level 58. The quantity of liquid 54 in the test tube 44 is greater than the amount of corresponding liquid in test tube 46 as indicated by the locations of the levels 56 and 58.

In a conventional centrifuge, adjustments would have to be made in order to offset the imbalance reaction forces due to the differences in the levels 56 and 58. No such adjustments are needed with the centrifuge of the present invention. Hence, the tedious time consuming chore of ascertaining the amount of the imbalance and then making the adjustment is no longer necessary. Further, a higher speed may be attained due to less friction and wear. As the rotor 18 is driven by the motor 14 at the desired speed, the annular supports 22, 22' together with their respective tube retainers and test tubes rotate about the axis of the projections 24 and 26.

The centrifugal force applied to the liquid 54 in the test tube 44 will cause the tube retainer 32 to move downwardly or outwardly in its annular support 22, depending the inclination of retainer 32, thereby applying pressure to the liquid 38 in annular support 22. The pressure thus applied will cause some of the liquid 38 to flow through conduit 40 to the chamber in annular support 22 until the respective centrifugal forces on the test tubes 44 and 46 are balanced.

The balancing concept of the present invention may be applied to centrifuges of a wide variety of constructions. The balancing effect is achieved in a manner which is simple, reliable, and more accurate than the methods utilized heretofore which are subject to human error and inaccuracies in the instruments utilized to achieve a balance.

The weight imbalance of tubes 44 and 46 is limited by the weight of the displaced liquid 38. Liquid 38 is preferably mercury because of its high specific gravity. If the contents of tube 44 is light in weight, such as 50 grams of a liquid whose specific gravity is less than 2, it would not be necessary to use tube 46 or make any adjustments. Thus, centrifuge 10 may be used with only one test tube. The weight of the contents of a single test tube which can be accommodated with automatic balancing is a function of the volume of liquid 38. To accommodate transfer of liquid 38 from one chamber to another, the chambers are only partially filled with liquid 38.

Flexible conduit 40 need not physically extend between the structures 17 and 19. The rotor 18 may have a bore connected at its end by a flexible conduit to each support 22.

As shown in FIG. 4, the tube retainer 32' may contain the liquid 38 therein. Retainer 32' has a pair of projections 60 (only one shown) rotatably supported by arms 62 (only one shown) on a rotor such as rotor 18. Conduit 40' communicates with liquid 38 in each pair of oppositely disposed retainers 32'. A disc-like spacer 64 transmits centrifugal forces from tube 44 through spacer 64 to force liquid 38 out through flexible conduit 40' when there is an imbalance as described above. Thus, in this instance, the retainers 32' are the annular supports.

The present invention may be embodied in other specific forms without department from the spirit or essential attributes thereof and, accordingly, reference should be made to the appended claims, rather than to the foregoing specification as indicating the scope of the invention.

Claims

1. A centrifuge comprising a motor mounted on a support structure, a rotor connected to the motor for rotation about a first axis, two annular supports on said rotor for rotation therewith about said axis, said annular supports being on opposite sides of said first axis and mounted for rotation about a second axis which is perpendicular to said first axis, each annular support having a chamber for containing a liquid, conduit means providing communication between said chambers, each annular support being adapted to receive a test tube, and means associated with each support for applying pressure to liquid in the chamber associated with its support in response to centrifugal force on a test tube.

2. A centrifuge in accordance with claim 1 wherein said means associated with each support for applying pressure includes a tube retainer.

3. A centrifuge in accordance with claim 1 wherein said conduit means includes a flexible conduit communicating with each of said chambers at the bottom portion thereof.

4. A centrifuge comprising a variable speed motor mounted on a support structure, a rotor connected to the motor for rotation about a first axis, at least two test tube support structures supported by said rotor adjacent the outer periphery thereof, each test tube support structure being mounted on said rotor diametrically opposite another test tube support structure, each test tube support structure being mounted on said rotor for rotation about a second axis perpendicular to said first axis, each test tube support structure being constructed and arranged to support a test tube, each test tube support structure including a chamber for containing a liquid, and conduit means extending from each chamber to a diametrically opposite chamber, and each test tube support structure including means for applying a force to liquid in its associated chamber as a function of the weight of the test tube supported thereby, said conduit means extending between diametrically opposite chambers adjacent to said first axis of rotation.

5. A centrifuge in accordance with claim 4 wherein said conduit means includes a flexible conduit connected to the bottom portions of diametrically opposite chambers.

6. A centrifuge in accordance with claim 4 wherein each test tube support structure includes a tube retainer having a radially outwardly directed flange which constitutes said force applying means.

7. A centrifuge in accordance with claim 6 wherein each test tube support structure includes a chamber constructed and arranged so as to surround its respective tube retainer and the flange thereon.

8. A centrifuge in accordance with claim 4 wherein each chamber is partially filled with liquid mercury.