Imperforate bowl: centrifugal separators – Process
Reexamination Certificate
1999-04-23
2002-03-05
Cooley, Charles E. (Department: 1723)
Imperforate bowl: centrifugal separators
Process
Reexamination Certificate
active
06352499
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention describes a process for operating a centrifuging unit, which includes a centrifuging container, in particular a centrifuging bowl, for separating the components of a liquid containing components with different specific weights, specifically blood. The centrifuging container contains a separation chamber, an inlet for the liquid to the separation chamber, and an outlet for a separated component from the separation chamber. The inlet and outlet extend through a revolving passage at the upper end of the container. The inlet is connected to an inlet channel which empties in the lower area of the container into a separation chamber. The unit includes a pump device to fill and/or empty the centrifuging container, whereby the liquid to be centrifuged is led to the inlet.
In addition, the invention has to do with a centrifuging unit, with a centrifuging container, in particular a centrifuging bowl, for separating components of a liquid containing components with different specific weights, specifically blood. The centrifuging container contains a separation chamber, an inlet for the liquid to the separation chamber, and an outlet for a separated component from the separation chamber. The inlet and outlet extend through a revolving passage at the upper end of the container. The inlet is connected to an inlet channel which empties in the lower area of the container into a separation chamber. The unit includes a pump device to fill and/or empty the centrifuging container.
It is the custom to use centrifuging units to separate components of a fluid with differing specific weights. Such centrifuging units, particularly centrifuging bowls, are used in separating blood, to separate the blood into its components. After donation, blood is normally broken down into its main components, i.e., blood plasma, low-molecular substances and proteins, and the cellular elements, of which red blood cells make up the major portion.
It is known that blood is centrifuged in batch fashion using a centrifuging bowl having an admission volume of several hundred milliliters. For each centrifuging process, this centrifuging bowl is filled with blood and centrifuged until the blood components with differing weights have formed layers and have separated from each other in the bowl. Thereafter, when the centrifuging unit has stopped, the individual components are removed from the bowl.
Such previously customary centrifuging permits only the overflow (i.e., the components with the smallest specific weight) to be obtained when the bowl rotates, until it is filled with heavy components. Then the bowl is stopped and once at rest the heavy components are removed from the stationary bowl. If these heavy components are needed (red blood cells erythrocytes- as a rule, in blood centrifuging), then this step presents the obtaining of the end product. Stopping the bowl, emptying it and refilling it, in order to separate several liters of blood into its individual components, is time-consuming.
One centrifuging unit with a bowl of the type mentioned initially for centrifuging blood is known from the U.S. Pat. No. 3,145,713. As depicted in the figures of this publication, the bowl in one embodiment shape is a cylindrical or conical container with an outer annular chamber which is formed between the exterior container wall and an inner insert. By means of a revolving passage on the outer side of the centrifuge container, blood is fed in via an inlet, roughly in the container's rotational axis. From this inlet, a channel leads to the base of the centrifuging container, where the blood, still not separated, is passed into the annular chamber. In the upper part of the annular chamber, provision is made for a connection with an outlet which runs through the revolving passage, by means of which the separated, lighter components are removed. After the annular chamber or separation chamber is filled with the heavy red blood cells separated from the blood, the process of admitting is interrupted, and the rotation of the bowl is stopped. Then the red blood cells are appropriately processed and subjected to deep freezing in the bowl, so that the entire unit with the red blood cells can be stored in deep-freeze fashion. It is necessary to equalize pressure in the centrifuging container between the inlet and outlet. To accomplish this, in the upper area, i.e., in the area where rotation takes place, a connection exists between the inlet area and the outlet area or the separation chamber.
Another centrifuge with a container or a bowl is known from the European Patent No. EP-B1-0 015 288. That text essentially is concerned with the special configuration of the rotating passage in the area of which the inlet and outlet are provided. Also in that bowl, the inlet is run via an inlet channel to the bottom area of the bowl, from which the admitted blood is transferred radially outward via a radial channel into an annular separation chamber. The inlet, placed in the area of the container's axis, is surrounded by an axial annular chamber, leading from the bottom of the bowl to its upper area, where it is short-circuited, i.e., connected, with the outlet or the separation chamber. This connection also serves to equalize pressure between individual chamber areas of the bowl.
Another procedure for separating blood into its components is published in European Patent Application No. EP-A1-0 014 093. The arrangement for carrying out the procedure includes a centrifuge with a rotating basin. In that basin, viewed in the radial direction, two bag-like containers are placed atop each other. Into one of these containers, the blood, not yet separated, is admitted and filled. Following separation, the rotor is stopped and the second container is filled with a liquid. The influx of the liquid into the second container pushes the first component separated from the blood out of the first container.
As the above description of the state of the art shows, and as was already explained, procedures according to the state of the art are carried out in batch fashion, i.e., in each instance, pre-set quantities of blood are processed which match the maximum container filling volume of the centrifuging rotor. Or, the volume of the rotor is used to collect a separated component such as red blood cells. Then the separation chamber, having been filled with these red blood cells, is emptied. Or, this separated component is frozen directly in the centrifuging bowl and stored. If small amounts that are less than the filling volume of such a centrifuging rotor are separated, a danger exists that after the rotor is stopped, the separated component may be mixed with the other separated components.
From the description above it is evident that for separating large quantities of liquid that exceed the filling volume of the centrifuging container, separation into individual batches is necessary, implying multiple starts and stops of the centrifuge, resulting in a time-consuming procedure.
In not only medical technology, but also in biotechnology areas, since separating suspensions using separator bowls by means of gravity gradients results in only slight gravity gradient differences, the liquids to be separated are subject to loads of multiple thousands of g (1 g is simple ground acceleration). Seen in physics terms, in the interior of the separation bowl, the desired gravitational field is created by its rotation. Thus, a centrifugal force F(Z) acts on each particle in the bowl. This force results from the product of the particle's density and the centrifugal acceleration b(z).
The product of the radius r and the angular velocity squared make up centrifugal acceleration b(z).
Classical bowls have the outlet configured as passing via two closely situated, static disks, which act like a pump or like a sliced disk (see aforementioned U.S. Pat. No. 3,145,713, column 5, lines 20 to 32). The liquid column that forms during operation grows with increasing filling until it reaches the outer edges of this pump. Liquid that touches the d
Cooley Charles E.
Milde Hoffberg & Macklin, LLP
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