Non-extruding lid seal for centrifuges

Abstract

A centrifuge rotor having chambers for sample containers and a cover is formed with fluid release openings in the cover to form what amounts to a pressure relief valve. The release openings communicate with a seal-ring groove in the cover. This guards against possible expulsion of the seal ring from the seal-ring groove in the event that one or more of the containers should rupture so that the fluid escaping from the container, producing centrifugal force and fluid pressure acting upon the cover, should bend it up sufficiently to open a gap for expulsion of the sealing ring thereby permitting the fluid to escape. The provision of the fluid release openings communicating between the seal-ring groove and the exterior of the cover permits sufficient fluid to escape through the opening in the event of partial distortion of the sealing ring upon the bending of the cover to allow the cover to return to sealing condition and to retain the remainder of the fluid within the rotor.

Description

BACKGROUND OF THE INVENTION

Fixed angle centrifuge rotors have been provided with a body having cavities for sealed sample tubes and a lid for the body with a seal to isolate the interior of the rotor from the high vacuum environment of the centrifuge chamber. This isolation is desirable to prevent possible leakage of contents of the centrifuge tubes from contaminating the vacuum system if the contents are corrosive or infectious. Conventional lid seal systems have been satisfactory for preventing minor leakage but difficulties may arise in case of a gross leakage resulting from faulty tubes or improper assembly techniques.

In case of a gross leakage, the rotor lid flexes under the influence of increasing fluid pressure so that the lid may bend far enough away from the rotor body to open a gap large enough to permit the seal ring to be expelled from the rotor. In that event, at least the seal ring must be replaced, and at most it can cause severe rotor imbalance, permanent lid deformation and great difficulty in lid removal.

It is accordingly an object of the invention to overcome the difficulties of existing centrifuge constructions and to make the centrifuge in such a manner as to form a pressure sensitive relief valve which will release only sufficient fluid to permit re-establishment of contact of the seal ring in the seal ring groove after a build up of fluid pressure has caused the rotor lid and the body of the rotor to part somewhat, and to distort the seal ring partially.

Other and further objects, features and advantages of the invention will become apparent as the description proceeds.

SUMMARY OF THE INVENTION

In carrying out the invention in a preferred embodiment of a centrifuge rotor having a vertical axis of rotation, the rotor is generally formed in a conventional manner with a body having an interior adapted to hold, in inclined positions, sealed tubes of samples to be centrifuged and having a cover or lid for the body with a seal between the lid and the rotor body to prevent fluid from escaping from the rotor in case some defect should cause some leakage of fluid from one or more of the sample tubes. In conventional apparatus the seal consists of a deformable sealing ring in an annular sealing groove formed in the cover at the surface thereof which confronts a contiguous surface of the body of the rotor.

However, in accordance with the invention, one or more openings are provided from the intersection of the horizontal and outer vertical walls of the sealing ring groove to release some of the fluid in case of a gross leakage from the tubes permitting fluid to escape from the tubes to the interior of the body of the rotor. Release of some fluid relieves the pressure of fluid which has escaped from the sample tubes sufficiently to permit the gap between the cover and the body of the rotor caused by such fluid pressure to close again and to restore the sealing ring to its normal position in the groove to prevent expulsion of the sealing ring from its groove and to retain the remainder of the fluid in the interior of the rotor.

A better understanding of the invention will be afforded by the following detailed description considered in conjunction with the accompanying drawing.

DRAWINGS

In the drawings:

FIG. 1 is a fragmentary view of a section cut by a plane through the vertical axis of rotation of a fixed angle centrifuge rotor forming an embodiment of the invention;

FIG. 2 is a half, top plan view of the embodiment of FIG. 1;

FIG. 3 is a series of diagrams fragmentarily illustrating the sealing ring portion of a conventional construction and illustrating the manner in which the sealing ring is expelled and the entire body of fluid in the interior of a centrifuge rotor is permitted to escape in the event that a gross leakage of fluid from a tube in the centrifuge should take place and exert fluid pressure and centrifugal force tending to pry up the cover of the rotor;

FIG. 4 is a series of diagrams corresponding to the diagrams of FIG. 3 illustrating the behavior of a centrifuge rotor constructed in accordance with the invention under the conditions represented in FIG. 3 and illustrating the manner in which pressure is relieved to prevent expulsion of the sealing ring and permit reclosure of the gap between the cover and the rotor body;

FIG. 5 is a pair of diagrams fragmentarily representing the sealing ring portion of the rotor in accordance with a modified embodiment of the invention.

Like reference characters are utilized throughout the drawing to designate like parts.

DETAILED DESCRIPTION

In a typical fixed angle centrifuge rotor, the rotor is formed with a body 11 having a vertical axis of rotation 12 and provided with a cover 13. The body has an externally threaded stem 14 to receive an internally threaded handle 15 to secure the cover 13 upon the body 11. The body has inclined chambers 16 for receiving tubes 17 of fluid samples to be centrifuged and the tubes 17 are provided with caps 18 which normally seal in the contents of the tubes 17. There is some space in the interior of the body 11 above each sample chamber 16 and under the cover 13 to form a cavity 19 into which fluid from the tubes 17 may escape in the event that any of them should be defective or improperly mounted or the caps 18 should have defective seals.

In order to retain such escaping fluid in the interior of the rotor, there are sealing rings 21 and 22, retained in annular grooves 23 and 24, respectively.

The sealing rings serve to prevent escape of any fluid in the cavity 19 when there is a minor leakage from one or more of the tubes 17. However, in the event of a gross leakage, sufficient centrifugal force and fluid pressure may build up under the cover 13 to bend up the outer edges and cause confronting faces 25 and 26 (shown in FIG. 3) of the body 11 and the cover 13, respectively, to part and form a gap 27 as shown in FIG. 3B.

In accordance with the invention, the construction is arranged to provide means for discharging fluid until fluid pressure has been sufficiently relieved. In the embodiment of the invention illustrated in FIGS. 1, 2 and 4, this is accomplished by providing holes 28 in the cover 13 extending to the exterior from the intersection of the plane-surfaced wall 31, perpendicular to the rotor axis of rotation 12, and the cylindrical-surface outer wall 32 of the annular groove 24 which is concentric with the rotor axis of rotation 12. This provides a discharge passageway from the peripheral groove 24 to the exterior of the rotor.

PRIOR ART OPERATION

The performance in a typical prior art construction when gross leakage of fluid from sample tubes builds up and a quantity of fluid is present in the cavity 19 is illustrated in FIG. 3. If there is a sufficient body of fluid 33 which, being subject to centrifugal force, exerts a fluid pressure to pry the circumferential portion of the cover 13 upward, the confronting surfaces 25 and 26 part so that they are no longer contiguous as illustrated in FIG. 3A and form a gap 27 as illustrated in FIG. 3B. Fluid pressure acting upon the sealing ring 22 tends to deform it as illustrated in FIG. 3B, pressing it away from the inside wall 34 of the groove 24. If the body of fluid 33 builds up as illustrated in FIG. 3C, there is still greater centrifugal force and fluid pressure so that the gap 27 becomes still greater and there is still further distortion of the shape in cross section of the sealing ring 22. Then when the bending force upon the cover 13 has become sufficiently great, the surfaces 25 and 26 part to such an extent as to form a gap 27 of sufficient width that the force of the liquid on the sealing ring 22 causes the ring to be expelled instead of merely being partially extruded and the entire body of liquid 33 escapes from the rotor. This has several deleterious effects.

Not only is the body of liquid lost in the vacuum lines and is the centrifuge system subjected to the contamination or corrosion of the entire body of fluid, but the cover 13 may be warped or distorted to such an extent as to be permanently damaged. Moreover, there may be great difficulty in removing the cover 13 and at the very least a new sealing ring 22 must be installed. Still worse, the distortion of the rotor cover 13 may cause such serious imbalance of the rapidly rotating rotor as to damage the mountings or create a safety hazard.

OPERATION IN ACCORDANCE WITH THE INVENTION

The results of the presence of a body of leakage fluid 33 in a rotor having the relief passageway 28 is illustrated in FIG. 4. Before the leakage of fluid 33 into the cavity 19 takes place, the confronting surfaces 25 and 26 are properly in contact, as illustrated in FIG. 4A. Then upon the presence of leakage fluid 33, as illustrated in FIG. 3B, a parting of confronting surfaces again takes place and the sealing ring 22 is partially extruded into the gap 27 as a result of deformation thereof.

With a still greater mass of fluid 33, as illustrated in FIG. 4C, still greater distortion and extrusion of the sealing ring 22 take place. As in the case of FIG. 3C, the sealing ring 22 is also pressed away from the inner wall 34 of the groove 24 so that sealing no longer takes place at this wall. Moreover, the sealing ring 22 also begins to be pulled away from the upper wall 31 of the groove 24, thus breaking the seal between the ring 22 and the upper wall 31. Consequently, as shown in FIG. 4D, there is an open escape passageway for the body of fluid 33 from the gap 35 between the parted surfaces (but inward from the ring 22 which is still retained in the groove 24 because the confronting surfaces have not sufficiently parted to permit the expulsion of the ring 22), the space between the ring 22 and the inner wall 34 of the groove 24, the space between the ring 22 and the upper wall 31 of the groove, and the hole 28.

Consequently, a small stream 36 of fluid is discharged. However, as soon as this occurs, the mass of fluid 33 is reduced, there is no longer sufficient centrifugal force and fluid pressure to cause the parting of confronting surfaces which resulted in the gap 35 so that the gap recloses and the confronting surfaces 25 and 26 are again in contact as illustrated in FIG. 4A.

It will be observed that the discharge of fluid from the hole 28 has taken place before the gap 35 has become great enough to permit expulsion of the sealing ring 22. Consequently, the sealing ring 22 is retained in the annular groove 24; the seal by the ring 22 between the surface 25 of the body 11 of the rotor and the surfaces of the groove 24, particularly in the upper wall 31 and the outer wall 32, is restored so that there is again a complete seal between the cover 13 and the body 11. Thus, a condition of equilibrium exists in which a maximum amount of fluid is retained in the rotor without the risk of the severe consequences associated with sealing systems not having the pressure relief means described. In this way, the construction described is basically a relief valve which is pressure sensitive. Fluid release may be provided either by the vertical openings 28, or by radial openings 28'.

By way of illustration an embodiment of the invention has been illustrated and described in which pressure relief is achieved by means of the holes 28 in the cover 13 extending to the exterior from the intersection of the upper and outer walls of the groove 24. However, the invention is not limited thereto and does not exclude other means for providing such pressure relief. For example, as illustrated in FIG. 5A and FIG. 5D, one or more fluid release openings 37 may be provided in the peripheral walls of the rotor body 11 which extend from the intersection 38 of the lower wall 39, perpendicular to the rotor axis of rotation, and the outer cylindrical wall 41 of an annular groove 42 formed in the surface 25 of the body 11.

While certain embodiments of the invention have been fully illustrated and described, it will be obvious to those skilled in the art that various modifications and alterations may be made therein and it is intended to cover all such modifications and alterations as may fall within the spirit and scope of the invention.

Claims

What is claimed is:

1. In a rotating receptacle having a chambered rotor and a cover therefor, a fluid pressure and centrifugal force relieving seal comprising:

confronting peripheral portions of the rotor and the cover having confronting, normally contiguous, contacting surfaces, one of the members comprising the rotor and the cover having an annular groove at the confronting surface thereof, said groove having a first wall substantially parallel to the plane of the contacting surfaces and an outer cylindrical wall intersecting the first wall, the grooved member having a pressure-releasing hole extending to the exterior thereof from the intersection of said intersecting walls, and

a resilient deformable sealing ring in said groove of such cross-sectional dimensions as normally to lie tangent to walls of the groove in the grooved member and to the confronting surface of the other member for sealing the confronting surfaces, whereby distortion of either of the members by fluid pressure or centrifugal force causing parting of the confronting surfaces of sufficient magnitude to distort the sealing ring out of tangency with either of the said groove walls opens said hole to permit release of sufficient fluid pressure to permit restoration of contact between said contiguous surfaces.

2. The seal defined in claim 1 wherein the pressure releasing hole extends radially.

3. The seal defined in claim 1 wherein the cover is the grooved member.

4. The seal defined in claim 1 wherein the cover is the grooved member and the pressure releasing hole extends parallel to the axis of rotation of the rotor.

5. The seal defined in claim 1 wherein the rotor is the grooved member.

6. The seal defined in claim 5 wherein the pressure releasing hole extends radially.