Imperforate bowl: centrifugal separators – Process
Reexamination Certificate
1999-01-19
2001-08-14
Cooley, Charles E. (Department: 1723)
Imperforate bowl: centrifugal separators
Process
C494S083000
Reexamination Certificate
active
06273849
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a centrifuge, in particular a flow-through centrifuge free of rotating seals, for centrifuging biological fluids and a line for supplying and/or removing at least one fluid from the separation unit of such a centrifuge to a stationary connection.
RELATED TECHNOLOGY
There are known centrifuges where the biological fluid is centrifuged in a flow-through process. The fluid is supplied to the rotating centrifuge chamber and removed from it through a line. However, guidance of the line has proven to be problematical because of the relative movement of the centrifuge chamber and the stationary connection of the line. To prevent twisting of the line, rotating seals are used at the connections on conventional flow-through centrifuges. Although such centrifuges permit a high speed of rotation, they have the disadvantage that the rotating couplings can lead to abrasion, leakage and thus contamination and damage of the components present in the fluid.
A flow-through centrifuge free of rotating seals is disclosed in German Patent Application No. 32 42 541 A. With this centrifuge, which is free of rotating seals, the line is passed from a stationary connection in a loop around the centrifuge chamber. To that end, the line is connected to a rotating frame which rotates at half speed in comparison with the centrifuge chamber. Such a flow-through centrifuge is also disclosed, for example, in German Patent Application No. 42 20 232 A. With this flow-through centrifuge free of rotating seals, the line is subjected to relatively great mechanical stresses, which increase greatly with increased speed of rotation. Under the influence of centrifugal forces, the line develops a loop which protrudes outward, as a result of which high alternate bending stresses develop at the stationary connection and the connection to the separation unit. The steep incoming and outgoing angles at the connections lead to additional friction between the adapters and the line, which in turn results in increased abrasion. The alternate bending stresses and the abrasion are factors that limit the life of the line and the maximum rotational speed of the centrifuge.
There are known flow-through centrifuges free of rotating seals which use bearings to support the line. International Patent Application No. WO 95/17261 describes a flow-through centrifuge whose centrifuge hose is supported by a roller bearing. The roller bearing, which has an inside and an outside bearing shell with the rolling element, is part of the line. The roller bearing does offer the advantage of low bearing friction, but it has the disadvantage that manufacture is expensive and thus the price is relatively high. This is a particular disadvantage since the centrifuge line is a disposable article which is discarded after use.
European Patent Application No. 112 990 A describes a flow-through centrifuge whose centrifuge hose is supported between the stationary connection and the connection of the separation unit by two friction bearings. The friction bearings each have inside and outside bearing shells with a cylindrical running surface which are part of the centrifuge hose, which is why the hose is relatively expensive to manufacture. The sliding surface is large, thereby producing high abrasion and heat. In addition, this bearing arrangement does not have sufficient axial support to prevent the bushing from slipping out of the sleeve.
SUMMARY OF THE INVENTION
An object of the present invention is to create a centrifuge whose line for supplying and/or removing at least one fluid is exposed to relatively minor mechanical stresses, but can nevertheless be manufactured easily and inexpensively as a disposable article.
The present invention provides a centrifuge with a rotating frame (
1
) which is rotatably mounted on a base (
2
), a separation unit (
4
) which is rotatably mounted on the base (
2
) and can be driven in the same direction as the rotating frame but at twice the speed, a line (
6
) for supplying and/or removing at least one fluid leading from a stationary connection (
5
) around the separation unit (
4
) and connected to the separation unit on a side facing away from the stationary connection, and at least one bearing (
7
) to support the line (
6
), having a sliding bushing (
9
) and a bearing shell (
13
) sitting on the line. The centrifuge is characterized in that the bearing shell (
13
) is mounted on the rotating frame (
1
), with the bearing shell and the sliding bushing (
9
) each having a sliding surface (
11
,
15
) with a widening radius, so that the sliding bushing is supported on the bearing shell in the axial and radial directions.
Another object of the present invention is to provide a line for supplying and/or removing at least one fluid to and/or from the separation unit of a centrifuge that will be simple and inexpensive to manufacture and will permit operation of the centrifuge at high rotation speeds with relatively minor mechanical stresses on the line.
The present invention provides a line for supplying and/or removing at least one fluid from a separation unit rotatably mounted on a rotating frame, which is in turn rotatably mounted on a base, where the separation unit is driven in the same direction of rotation as the rotating frame but at twice the speed, with at least one sliding bushing (
9
) sitting on the line. The line is characterized in that the sliding bushing (
9
) has a sliding surface (
1
) with a widening increasing radius, so that the sliding bushing can be inserted into a bearing shell and is supported in the axial and radial directions.
With the centrifuge according to the present invention, a sliding bushing with a widening, preferably conical, sliding surface sits on the line for supplying and/or removing at least one fluid, while a bearing shell is mounted on the rotating frame of the centrifuge with a sliding surface that also widens. The bearing shell here is preferably open to ensure easy insertion of the bushing. The bearing arrangement preferably has a catch option, with an elongated slot-shaped opening in the bearing shell being slightly narrower than the diameter of the bushing. However, conventional insertion mechanisms may also be used and are covered by the present invention.
Since the line includes only the sliding bushing, it is simple and inexpensive to manufacture. The sliding bushing may be designed as a separate part, preferably an injection molded part, which is pushed onto the line and attached to the line in a rotationally fixed manner, e.g., by welding or gluing. As an alternative, the sliding bushing may also be manufactured in one piece with the line.
In this context, a line for supplying and/or removing at least one fluid is understood to refer not only to a hose with one or more lumens but also an arrangement of multiple single-lumen hoses.
In a preferred embodiment, the sliding bushing is made of a material of less hardness than the material of which the bearing shell is made. This has the advantage that it ensures the fatigue strength of the bearing shell, which is not replaceable. Wear on the sliding bushing, however, is not a problem since this is part of the line intended for a single use.
With the bearing composed of sliding bushing and bearing shell, the centrifugal forces acting on the line are transmitted to the rotating frame, thus relieving the load on the line. Parts of the sliding surfaces of the bearing shell and the friction bearing which come in contact are so small that heat and abrasion are low and little noise is generated. The widening of the sliding surface and a peripheral projection ensure accurate centering and concentric running of the line. This permits an increase in the rotational speed of the centrifuge and prevents the bushing from slipping out of the bearing shell. There is also a speed-dependent pressing of the sliding bushing in the bearing shell with minimal friction losses.
The sliding bushing is preferably made of plastic, especially a polyacetal plastic (POM) or TEFLON brand polytetrafluo
Cooley Charles E.
Fresenius AG
Kenyon & Kenyon
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