EP0199696A2

EP0199696A2 - Laboratory centrifuge

Info

Publication number: EP0199696A2
Application number: EP86850144A
Authority: EP
Inventors: Ingemar Wahl
Original assignee: Landstingens Inkopscentral LIC
Current assignee: Landstingens Inkopscentral LIC
Priority date: 1985-04-22
Filing date: 1986-04-21
Publication date: 1986-10-29
Also published as: EP0199696A3; SE8501947D0; SE8501947L

Abstract

The present invention briefly concerns a centrifugal rotor for laboratory centrifuges, comprising a disk (1) and a cover (10), whereby a ring-shaped carrier (5) of capillary tubes (9) is attached to the bottom of the disk (1). The disk (1) has at its outer periphery an axially projecting flange (3) which is inclined relative to the axis of rotation of the centrifugal rotor, so that any liquid escaping out into the centrifugal rotor is urged by the centrifugal force to the ring-shaped, circular edge (20) formed between the flange (3) and the bottom (2, 17) of the disk (1). Preferably, the cover has a peripherally outer portion with a step in the form of an axially extended portion (13). which continues in a radially ring-shaped edge portion (14), the axially extended portion (13) having a height greater than the thickness of the folded-back portion (4) of the axially projecting flange of the disk (1) and a gasket ring positioned thereon.

Description

The present invention is relative to centrifuges. In particular it concerns a laboratory centrifuge for centrifuging capillary tubes.
In order to determine presence of diseases and their extent, a common procedure is to fill a capillary tube, a so-called hematocrit tube, with blood. The tube, which extends radially in the centrifuge, is then centrifuged at a high number of revolutions.
Since during this type of procedure it can be a matter of not only contagious but of often dangerous diseases, the work when centrifuging should be done without any risk what so ever for the personnel carrying out the centrifugal procedure. Centrifugation is normally done at a number of revolutions at approximately 10.000 RPM, causing a relative centrifugal force (RCF) of approximately 10.000 grams for a normal size of the centrifugal disk. It is thus a matter of tremendous force, to which the thin hematocrit tubes are subjected, and these tubes, which are made of glassy, can easily break due to for instance invisible, small manufacturing defects or their mal- positioning in the carrier.
The handling of broken tubes is per se no large problem, although we would rather be without that nuisance. The real problem occurs when one or several tubes break during centrifugation and liquid from the tubes ends up in and about the centrifuge. The great centrifugal force of the tubes causes, when the tubes break, what can resemble a minor explosion and liquid is flung out in all directions. The liquid is then urged by the centrifugal force to stream along the inside of the centrifugal disk and cover towards their peripheries.
If the cover and the disk do not form a tight unit, air will stream through the container formed by said cover and disk. This air tears away particles from the liquid and a fog or an aerosol is generated outside of the centrifugal container. The aerosol can easily be inhaled by the personnel operating the centrifuge and thus communicating infection to them. One problem of centrifuges of today is to provide a seal between disk and cover exactly at the periphery thereof. This seal functions at the prevailing rotary force during centrifuging.
The purpose of the present invention is to eliminate the above problem. This objective is achieved by a centrifugal rotor of the kind stated in the claims, wherein it will also be evident what in particular is characteristic of the invention.
The invention will be described below more in detail in conjunction with the accompanying drawings, in which

FIG. 1 is a perspective top view of a centrifugal disk for centrifuging hematocrit tubes,
FIG. 2 is a perspective top view, partially in a cross section, of a lid for covering said centrifugal disk shown in Fig. 1,
FIG. 3 is a cut away showing an alternative embodiment of the edge of the lid, and
FIG. 4 is a cut away through a centrifugal disk and a lid in their ready-to-be assembled position.

The centrifugal disk 1 consists of an essentially plane, circular base 2 and a circumferential flange 3 projecting essentially perpendicular from the base 2. The free, upper edge of the flange 3 is folded at 4, thus extending over base 2. A tube carrier 5 in the form of a ring-like tray is positioned on the base 2 concentrically around a hub 7, which is adapted to be positioned on the output shaft proper of the centrifugal machine. The tube carrier 5 is preferably made of cellular plastic and has radial, regularly spaced grooves in which the hematocrit tubes 9 are placeable.
The cover 10 shown in Fig. 2 reminds us of a conventional pan lid and has a central fastening bolt 11, a plane portion 12 extending around said bolt and which plane portion is designed at the circumferential edge as a step with a portion 13, which is axially projecting from said plane portion 12, and a portion 14, which continues again radially projecting from said portion 13. The axial portion 13 is adapted to fit inside of the folded-back portion of the centrifugal disk 1, and the radial portion 14 is adapted to rest against the outside of the folded-back portion 4.
With reference to Fig. 3 there is shown a preferred, alternative embodiment of the circumferential edge of the cover 10, where the radial portion 14 is continued at its free edge by a downwardly folded flange 15, which is adapted to fit around the circumferential flange 3 of the centrifugal disk 1.
It is obvious from Fig. 4 how cover 10 and disk 1 fit together with the axial portion 13 fitting inside of the folded back flange portion 4, and the radial portion can fold against this axial portion 13. In use there is inserted a gasket. The fastening bolt 11 of the cover 10 is pivoted relative-to the cover itself, but is sealed relative to said cover so that no significant air passage is present at the tightening of the bolt 11.
In use the bottom 2 of the disk 1 is inclined outwardly and upwardly from the hub 7 approximately 1-2 degrees. At a distance inside of the circumferential flange 3 there is designed a circular step 16 in the shown embodiment, radially outside of which step the bottom forms an angular surface 17 situated above the bottom surface 2 but in a plane parallel to said bottom surface. This step is an indicator of the position of the tube carrier or insert 5, which retains the tubes 9 during centrifugation. In the represented embodiment this tube carrier 5 is made of a cellular plastic material, which insulates against the heat that tends to emerge from the centrifugal machine positioned under the disk.
During mounting of said disk 1 and cover 10 the underside of the plane portion 12 of cover 10 at the axial portion 13 will end up positioned below the level of the underside of the folded-back flange portion 4. It is true that the cover 10 is shown some-what arched in the drawings, but this is not a necessity. The important thing is that the plane portion 12 of cover 10 at the axial portion 13, even with a gasket between the radial portion 14 and the folded-back flange portion 4, is situated inside of the inner surface of this flange portion 4. This means that liquid, which is forced to run along the inside of the cover 10 by the centrifugal force, ends up in the ring-shaped canal 19 situated at the disk edge.
The circumferential flange 3 projects perpendicular from the slightly angled bottom 2, which means that the edge 20 between the ring-shaped surface 17 and the circumferential flange 3 will lie as a circular ring having the largest distance from the rotary centre, that is the hub 7, of any part of the disk 1. The tubes 9 are retained in the carrier 5 parallel with the bottom 2, and since the circumferential flange 3 is perpendicular to the bottom 2, the ends of the tubes 9 being barred perpendicularly will steadily rest against this inside of the flange. For the tubes 9 at the outer ends to be sealed, a plug of putty of wax is inserted into the tubes. As an extra security there is a flexible ring 21 positioned against the inside of the flange 3, against which the tube ends are pressed during centrifugation.
In case that one or several tubes 9 would burst during centrifugation the liquid is therefore flung out into the hollow space that is made up by the disk 1 and the cover 10. Since this hollow space is tight there is no air stream through it, and neither gas nor aerosol will thus be generated. The liquid is however forced outwardly by the centrifugal force, and the liquid portion following the inside of the cover 10 will abandon said cover at the axial portion 13 and be caught in the ring-shaped canal 19. The liquid portion remaining in the disk 1 is urged along the upper surface of the carrier 5 and is also caught in the canal 19. Since, as is mentioned above, the circumferential flange 3 is inclined relative to the axis of rotation, the liquid is pressed along its inside and down into the circular edge 20.
If there would be an opening present between disk 1 and cover 10 at their peripheries, the described design will prevent liquid particles from being flung out in case a tube bursts. There is however no risk for gas or aerosol to be generated, since no air is capable of passing through the centrifugal rotor constituted by cover 10 and disk 1.
Drawbacks inherent in previously known laboratory centrifuges are thus overcome by the present invention. It is obvious to a person skilled in the art that the described centrifuge can be varied in detail, but such variations are intended to stay within the frame of the appended claims.

Claims

1. A centrifugal rotor comprising a disk (1) and a cover (10), wherein the disk (1) includes a carrier (5) of the capillary tubes (9) to be centrifuged, characterized in that the disk (1) at its outer periphery has an axially projecting flange (3) which relative to the axis of rotation of the centrifugal rotor, is inclined so that any liquid escaping out into the centrifugal rotor is forced by the centrifugal force to the ring-shaped circular edge (20) formed between the flange (3) and the bottom (2, 17) of the disk (1).

- 2. A centrifugal rotor according to claim 1, characterized in that the cover has a circumferential outer portion with a step in the form of an axially extended portion (13), which continues in a radially ring-shaped edge portion (14), the axially extended portion (13) having a height which is greater than the thickness of the folded-back portion (4) of the axially projecting flange of the disk (1) and a gasket ring positioned thereon.

3. A centrifugal rotor according to any of preceding claims, characterized in that this rotor is tight in its assembled state.