Centrifuge Rotor Cover

Abstract

There is disclosed a cover for a centrifuge rotor which is affixed thereto by being screwed onto the hub of the rotor. The cover is constructed in a manner to provide a depending skirt which seats against an upstanding rim of a rotor of a centrifuge. This cover is constructed to seat tighter under the centrifugal forces encountered whereby a portion of the skirt is urged outwardly and down against the seat on the rim. The cover is also designed to have an annular well for collecting small quantities of overflow fluid. The cover is also consructed with a means to preliminarily provide communication between the outside and inside the rotor of the centrifuge in order to establish equilibrium therebetween prior to removal of the cover.

Description

BACKGROUND OF THE INVENTION

During the last few years chemical laboratory procedures, especially with regard to clinical chemistry, have demanded that centrifuges be capable of rotating at ever greater speeds. As a result, an ultra-centrifuge has been developed which employs a rotor normally used at revolutions per minute in an excess of 60,000. Of course, such rotors are carefully constructed to provide accurate balance and good strength integrity so that the rotor does not fly apart under the terrific centrifugal forces built up as it is rotated. The centrifuge tubes employed in such ultracentrifuges are capped and sealed after the liquid contents are added to the tubes. In many cases it is necessary to insure a sealed environment within the rotary even though the tubes themselves have been sealed. The tubes are sealed at ambient atmospheric pressure as is the rotor itself by means of a centrifuge rotor cover. However, the rotor is operated in a vacuum.

Under the terrific forces created, the caps may not seal as well as desired and some of the liquid contents therein may gradually creep out of the tube. To retain the liquid that may be spilled from the tubes during centrifugation a rotor must have a cover. As the tubes may contain liquids which are radioactive or which possess dangerous biological materials, it will be apparent that serious problems could follow if there would be leakage beyond the confines of the rotor. As the rotor is in a vacuum chamber, the vacuum pump would remove any spilled materials from the chamber and expell at least some of such materials into the laboratory atmosphere. A well working cover that performs its task even though being subjected to considerable centrifugal forces and hydrostatic forces from accumulated tube leakage is the subject matter of the present invention.

SUMMARY OF THE INVENTION

The cover of the present invention has an overall disc-like configuration. A downwardly depending skirt is designed to have a portion thereof seat itself internally with respect to an upwardly extending peripheral rim on the rotor. The cover has a concentric aperture. A core is slidably positioned in the aperture. The core has a portion of sufficient diameter whereby it fits relatively snugly within the aperture. The core has a recessed shoulder approximately flush with the upper surface of the cover directly associated therewith. The core has an upwardly extending portion about which is positioned a hollow outer shell. The shell is designed so that a downwardly facing surface bridges the shoulder of the core and a portion of the surface of the cover. The outer shell and core near the upper portion thereof are held together by a common acting handle. The other end of the core possesses means whereby it is screwed to the hub of the rotor. As the cover is screwed to the hub, the outer shell and core which has an O-ring move slightly relative to the cover whereby a sealing action occurs as the O-ring is squeezed between the core and inside the aperture of the cover. This sealing action occurs at the end of the operation to tighten the cover. Conversely, when the cover is to be removed the core and outer shell by first being loosened makes it possible to establish gas pressure equilibrium between the atmosphere and the space in the rotor.

Of considerable importance to the instant invention is the fact that the cover has a relatively thinned portion intermediate the aperture and the outer periphery of the cover. As the centrifugal forces exert themselves, the skirt will tend to be thrust radially outwardly and downwardly to seat itself more securely against the rim which is more resistant to enlargement.

Additionally, the skirt is provided with an annular well internally with respect to the skirt whereby most of the liquid which may escape from the centrifuge tubes and creeps upwardly will be captured by the well and the subsequent hydrostatic pressure will be self contained minimizing any tendency to lift the lid.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a rotor of an ultracentrifuge with the cover of the present invention attached thereto.

FIG. 2 is a cross section taken along line 2--2 of FIG. 1 with the cover not yet completely secured.

FIG. 3 is a similar view as in FIG. 2 with the cover completely secured.

FIG. 4 is a close-up cross-sectional view to provide a detail view of the manner of seating the cover of the present invention with respect to an upstanding annular rim of the rotor of the centrifuge.

DETAILED DESCRIPTION OF THE INVENTION

Beginning with FIG. 1 the cover shown, generally, by reference numeral 10, depicts the cover of the present invention. It will be noted that the cover is secured to a rotor 11 of a centrifuge. The rotor is of the ultra-high speed type usually machined from a single metal block with fixed recesses designed to accept specially constructed centrifuge tubes. These tubes are utilized in a sealed tightly capped condition. More details with respect to the centrifuge rotor can be gleaned from FIGS. 2 and 3. The recesses 12 for the centrifuge tubes can be seen.

Again, with particular reference to FIGS. 2 and 3, the cover 10 includes a disc means having an annular portion. The annular portion has a centrally located aperture 14. The annular portion terminates in a downwardly depending annular skirt 15. It will be seen that the annular portion has a flat section 16 facing upwardly. The other or underside 17 is inclined upwardly. As the two surfaces, i.e., section 16, and underside 17 are not in the same plane the annular portion will tend to decrease in thickness and at 18 assumes its thinnest dimension. The flat section 16 terminates at 18 into an upwardly extending radial portion 19. Portion 19 will be seen to be somewhat thicker than at 18.

The depending skirt 15 has an outwardly facing shoulder 21, as seen in greater detail in FIG. 4. The shoulder includes a downwardly facing flat surface 22. The skirt 15 is inclined inwardly to form portion 23. An outwardly facing peripheral groove 24 is located in portion 23. The groove 24 is adapted to accommodate O-ring 25. The O-ring will be seen to be in confrontation with the internal portion of the rim 26 of the centrifuge rotor 11. More about this will be stated below.

Within the aperture is cylindrically shaped core 30. The portion 31 constituting a first portion of the core is designed to fit slidably but rather snugly within the aperture. The outwardly extending periphery has an annular groove 32 into which is fitted a suitable O-ring 33. The aperture 14 has a lower wider diameter portion so that the aperture 14 is somewhat larger at the bottom than at the top. Near substantially the bottom of the portion 31 of the core is an outwardly radially extending flange 35. The flange 35 enlarges the lower part of the core to an extent whereby it cannot be removed upwardly from its position in the aperture.

The core extends upwardly beyond the plane of the upper flat surface of section 16 to form a second portion. The core has a shoulder 36 with a flat upwardly facing section approximately in the same plane as section 16. An outer shell 38 having a bore encompasses the remainder of the upwardly extending core. It has a downwardly facing recess 39 adapted to bridge the shoulder 36 and a portion of section 16. A peripheral downwardly extending flange 53 forms one wall of the recess. The flange is adapted to fit into annular groove 54 in section 16. An annular washer 40 is positioned in the recess 39 and the upwardly facing section and section 16. The washer 40 acts to prevent wear.

The upper part of the outer shell and the core therein are rotated by a handle 41 which extends radially therefrom. It is positioned in a bore 42 normal with respect to the axis of the core. The handle 41 is also in alignment with bores 43 and 44 in the outer shell 38. The handle is retained in position by a set screw 45.

The portion 31 of the core has an internally threaded recess 47 adapted to receive a suitably threaded male member 48, constituting the hub of the rotor. In order to secure the cover of the present invention the core is screwed onto the hub of the rotor. As the core is tightened the outer shell moves downwardly with the core. The annular portion 13 is, of course, positioned on the rim of the rotor at its outer peripheral extremity. The part adjacent the aperture 14 is between the outer shell and the flange 35 of the core. From FIG. 2 it will be seen that the core and outer shell are withdrawn from the annular portion 13 to the extent permitted by the cooperation of the flange 35 and the widened portion of aperture 14. With the core and outer shell withdrawn the O-ring 33, thereby providing a gaseous communication with respect to one side of the cover to the other. When the cover is screwed onto the rotor the core and outershell are screwed onto the rotor therewith carrying the annular portion to a sealing condition.

In unscrewing the cover the opposite relative movement occurs so that the core and outer shell recedes from its sealing engaging position to provide pressure or vacuum relief to the space in the rotor.

Not mentioned before, is the ingenious annular well 50 internally around the skirt. As this is the furthermost space from the axis of the cover any liquid escaping from the recesses 12 of the rotor and finding its way into the internal spaced defined by the cover will become segregated in this well.

As was stated heretofore the rotor is fabricated of high strength metal materials. Likewise, the cover of the present invention should be constructed of similar materials as the cover is subjected to the same enormous centrifugal forces as the rotor when the centrifuge is operated.

Claims

What is claimed is:

1. A cover for a centrifuge rotor comprising a substantially disc means, said disc means having a downwardly depending skirt substantially along the periphery thereof, said disc means having a centrally positioned circular aperture, a cylindrical core means, said core means having a first portion adapted and constructed to fit slidably relatively snugly within said circular aperture, said core means having a second portion above said first portion which has a diameter less than the diameter of said first portion thereby forming a shoulder on said core means, an outer shell means, said outer shell means having a bore adapted and constructed to slidably encompass said second portion of said core means, the disc means having an upper radially extending flat surface portion radiating directly from said aperture and a concomitantly lower upwardly inclined radially extending surface whereby the disc decreases in thickness, the said upper flat surface terminating in an upwardly radially extending portion having an increasing thickness, the said upwardly radially extending portion substantially terminating with said skirt, the said skirt having a downwardly facing shoulder along the outer periphery thereof, said skirt beginning at said shoulder having an inwardly inclined terminal portion adapted to rest against an annular seat on a centrifugal rotor, the outer shell having a thickness sufficient to bridge the said first portion and the said upper flat surface, said core means having means at the bottom portion thereof for screwing said cover onto cooperating means on a rotor of a centrifuge, said core means and said outer shell means having joint handle means at their respective upper portions thereof.

2. The cover for a centrifuge according to claim 1 wherein an annular washer means is positioned between the said outer shell bridging the said first portion and the said upper flat surface.

3. The cover for a centrifuge according to claim 1 wherein the means for screwing the cover to the rotor of a centrifuge includes an internally threaded recess at the bottom of said core means adapted to be threaded onto a threaded male portion of a rotor.

4. The cover for centrifuge according to claim 1 wherein the said handle means radially extends through said core means and said outer shell means.

5. The cover for a centrifuge according to claim 1 wherein the first portion of said core means has an outwardly radially extending flange and said aperture has a lower wider diameter portion adapted and constructed to engage said flange whereby the said core means is restrained from parting from said disc means.

6. The cover for a centrifuge according to claim 5 wherein an annular washer means is positioned between the said outer shell bridging the said first portion and the said upper flat surface.

7. The cover for a centrifuge according to claim 6 wherein the means for screwing the cover to the rotor of a centrifuge includes an internally threaded recess at the bottom of said core means adapted to be threaded onto a threaded male portion of a rotor.

8. The cover for a centrifuge according to claim 7 wherein the said handle means radially extends through said core means and said outer shell means.