Seal for a joint or juncture – Seal between relatively movable parts – Circumferential contact seal for other than piston
Reexamination Certificate
1998-09-10
2001-09-11
Knight, Anthony (Department: 3626)
Seal for a joint or juncture
Seal between relatively movable parts
Circumferential contact seal for other than piston
C277S567000, C277S572000, C073S001870, C494S038000
Reexamination Certificate
active
06286838
ABSTRACT:
The present application claims priority to German Patent Application No. 198 07 668.1, filed Feb. 25, 1998, which claims priority to German Patent Application No. 197 40 270.4, filed Sep. 15, 1997, which, for purposes of disclosure, are incorporated herein by specific reference.
BACKGROUND OF THE INVENTION
1. The Field of Invention
The present invention relates to centrifuge rotors and, more specifically, centrifuge rotors which can be sealed closed so as to prevent accidental dispersion of material held within the rotor during operation of the centrifuge.
2. The Relevant Technology
Centrifuges are used in a variety of different environments for facilitating such services as separating substances of different densities, removing moisture from materials, and for simulating gravitational effects. A conventional laboratory centrifuge includes a rotor housing which is attached to the drive shaft of a motor. The rotor body is configured to receive test tubes which hold a desired substance. As the motor is operated, the rotor is rapidly spun so as to produce an increased gravitational affect on the substance within the test tubes. Where the substance is a solution, the elements of the solution are then separated by density.
To increase the operational safety of centrifuges, a lid is typically removably secured to the rotor body. Should a test tube accidentally fail, the lid helps to prevent parts of the test tube and/or the substance it contains from being thrown or dispersed into the surrounding environment. This is particularly important where the centrifuge is spinning a hazardous substances.
Although lids are helpful in containing the substance of failed test tubes, it is still possible for the spilled substance to seep out at the joint between the lid and the rotor body. To help prevent leaking at the joint, attempts have been made to position a seal between the lid and rotor housing. The seals, however, are often distorted and fail under the tremendous centrifugal force applied thereto
In one attempt at incorporating a seal, German Patent No. 29 07 001 C2 and corresponding U.S. Pat. No. 4,202,487 disclose a rotor housing with a screw-on lid. A sealing O-ring is positioned along the periphery between the rotor housing and rotor lid so that the sealing action of the O-ring is reinforced when the centrifuge is in operation. That is, this arrangement generates a moment of rotation which produces a radial centrifugal force, and it also generates a sealing force in the axial direction. It thereby becomes possible to bring about a sealing with a reliable sealing action even if the lid is screwed on only loosely. Due to the construction of the rotor lid and the rotor housing, the O-ring is held in its correct position in order to obtain a favorable sealing during the centrifugation procedure.
Although useful, some problems have been shown to arise with the above arrangement. For example, O-rings require a relatively narrow tolerance range. In addition, the above assembly does not facilitate the collection of spilled fluids in the rotor.
OBJECTS AND BRIEF SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a rotor assembly which is sealable so as to retain liquid with high certainty in the rotor during centrifugation.
Another object of the present invention is to provide a rotor assembly as above, wherein the sealing effectiveness increases as the centrifugal force increases.
Yet another object of the present invention is to provide a rotor assembly as above which functions to collect spilled materials within the rotor.
Finally, another object of the present invention is to provide a rotor assembly as above which can be easily manufactured having relatively large tolerances.
To achieve the foregoing objects, and in accordance with the invention as embodied and broadly described herein, a sealable centrifuge rotor assembly is provided. The rotor assembly includes a rotor body having a loading region encircled by an annular first bearing surface. The loading region is formed having recesses configured to receive test tubes or other centrifugable containers. A lid is configured to be removably secured over the loading region of the rotor body. The lid has an annular second bearing surface.
The rotor assembly further includes an annular sealing element having a substantially U-shaped transverse cross-section. The sealing element includes an outwardly facing base. An annular first sealing lip projects inwardly and upwardly from the top end of the base. A second sealing lip projects inwardly and downwardly from the bottom end of the base. An annular collecting groove is formed on the inside face of the sealing element between the first sealing lip and the second sealing lip.
As the lid is secured to the rotor housing, the first sealing lip of the sealing element is biased in sealing engagement against the bearing surface of the lid. Likewise, the second sealing lip of the sealing element is biased in sealing engagement against the bearing surface of the rotor body. An annular jacket flange which projects from the lid and/or the rotor body is disposed against the outward facing surface of the base of the sealing element. In this position, the lid and rotor housing are sealed together when in an idle position.
During centrifugation, the jacket flange functions to hold the base of the sealing element in position. Simultaneously, the centrifugal force functions to spread the sealing lips apart from each other so that the sealing lips of the sealing element further bias against their corresponding bearing surface. Accordingly, the greater the centrifugal force, the greater the effective seal between the sealing lips and the bearing surfaces. Furthermore, the bearing surfaces of the lid and rotor body are angled so as to form a gap therebetween which narrows radially outward. Accordingly, as the sealing element is forced outward under the centrifugal force, the sealing element is compressed within the narrowing gap between the bearing surfaces, thereby further increasing the effective seal therebetween.
In one embodiment, the sealing element is constructed to be symmetrical when viewed in a transverse cross-section. As such, the sealing element is rotationally symmetrical. The simple handling of the sealing element due to its symmetric construction proves to be advantageous.
An additional advantage of the present invention is that the U-shaped collecting groove on the sealing element functions to collect liquids or other materials that may have spilled within the loading region without stressing the sealing gap. That is, as the liquid is collected between the sealing lips of the sealing element, the liquid is not being forced between the sealing lips and the bearing surfaces. As such, the potential for the substance seeping between the sealing lips and the bearing surfaces is minimized.
Furthermore, in an advantageous arrangement it is possible to divide the collecting groove of the sealing element into sectors by lamellar walls. In so doing, it is also possible to construct the recess in the sealing element in the form of borings in the radial direction.
In one embodiment, an annular inner flange extends from the lid and/or rotor housing such that the inner flange is adjacent to the inside face of the sealing element. In this embodiment, the outer face of the sealing element is bounded by the jacket flange and the inner face of the sealing element is at least partially bounded by the inner flange.
One of the advantages of the present invention is that it can be manufactured inexpensively. That is, as a result of the expandable nature of the sealing element, the rotor assembly can be manufactured from plastic parts having relatively large tolerances. Moreover, the symmetry of the sealing element allows its insertion without the risk of confusion. In addition, by way of example, it appears that liquid volumes up to about 0.5 ml can be retained within the collecting groove without stressing the sealing gap.
These and other objects, features, and advantages of t
Betke Viktor
Eigemeier Frank
Kruger Helmut
Kendro Labatory Products GmbH
Knight Anthony
Patel Vishal
Workman & Nydegger & Seeley
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