Imperforate bowl: centrifugal separators – Rotatable bowl – Including housing for bowl
Reexamination Certificate
2001-11-02
2004-05-18
Cooley, Charles E. (Department: 1723)
Imperforate bowl: centrifugal separators
Rotatable bowl
Including housing for bowl
C494S067000, C494S084000
Reexamination Certificate
active
06736768
ABSTRACT:
INTRODUCTION
The present invention is directed generally to centrifugal fluid separation devices and is more particularly concerned with a pressure driven and/or balanced separation device preferably having a disposable, non-invasively driven, loopless rotor disposed in a rotating-sealless relationship with the entry and exit flow tubing lines.
BACKGROUND OF THE INVENTION
A number of fluid separation devices have been known and various models are currently available for the separation of blood or other composite fluids into the various component elements thereof. For example, a variety of centrifugal machines are available for separating blood into component elements such as red blood cells, platelets and plasma, inter alia.
Centrifugation for such purposes has come in many forms in both continuous and batch types. For example, in the widely used process known as continuous centrifugation, as generally opposed to batch process centrifugation, a continuous input of a composite fluid is flowed into the separation device or chamber while at the same time the components of that composite fluid are substantially continuously separated and these separated components are usually then also substantially continuously removed therefrom. Many currently popular forms of such continuous fluid separation devices include loops of entry and exit flow tubing lines connected to the separation centrifuge chamber such that each loop is rotated in a relative one-omega—two-omega (1&ohgr;-2&ohgr;) relationship to the centrifuge chamber itself so that the tubing lines will remain free from twisting about themselves.
An alternative form of tubing line connection to a continuous centrifugal separation device is also available in the art which does not have such a loop, but which instead requires one or more rotating seals at the respective connections of the tubing line or lines to the centrifuge separation chamber, again to maintain the tubing lines free from twisting.
Batch-type centrifugation, on the other hand, usually involves separation of a composite fluid such as whole blood in a closed container, often a deformable bag, followed by a usually complicated process of automated and/or manual expression of one or more of the separated components out of the separation container or bag. A great deal of control, either automated, such as by optical interface detection, or by a diligent human operator watching a moving interface, is required with such previous batch-type processes. Indeed, various means and methods have been used in prior centrifugal separation devices both continuous and batch, for driving fluid flow and for maintaining desirable interface position control between the component elements being separated thereby. For example, as mentioned, many optical control feedback methods and devices have been employed in the art. Various pumping and valving arrangements are also used in various of these and other systems. Alternative, relatively automatic volume flow and density relationship interface controls have also been used. For example, in a continuous system, control outlet ports may be disposed in strategic locations relative to the separated component outlet ports.
Nevertheless, many facets of these prior separation devices, though satisfactorily productive, may provide certain features which are less efficient than a desired optimum. For example, centrifugal separation devices using loops of tubing lines rotated in the above-described 1&ohgr;-2&ohgr; relationship with the centrifuge separation chamber generally require significant, usually large drive mechanisms which thereby mandate that each such entire device then also be necessarily of a relatively large scale. Rotating seal devices, on the other hand, require intricate and often operationally problematic rotating seal structures. Sterility may also be an obstacle for rotating seals. Still further, many prior drive and/or interface control systems have either been overly complex as in the case of most of the optical control models, and/or automatic volume flow/density controls may not be as desirably efficient in separation due to the usually inherent re-mixing of some quantities of the centrifugally separated components.
Hence, substantial desiderata remain to provide more highly efficient centrifugal separation devices in terms of increased efficiency fluid flow drive and separation interface controls; reduced rotor drive mechanization, quantity and/or scale; and/or reduced seal need and/or intricacy. It is toward any one or more of these or other goals as may be apparent throughout this specification that the present invention is directed.
BRIEF SUMMARY OF THE INVENTION
The present invention is directed generally to centrifugal separation devices and/or systems for use in centrifugally separating composite fluids into the component elements thereof. Such centrifugal separation devices and/or systems include unique centrifugal rotor and rotor housing combinations in which each rotor may be disposed in a freely rotatable disposition relative to the rotational device housing. Freely rotatable indicates loopless and rotating sealless as well as a preference that these rotors may be magnetically or otherwise non-invasively driven. A totally closed system may thus be provided with simple sterilization and disposability of the rotor and/or the rotor/housing combination and/or the tubing set associated therewith.
Each rotor has a substantially central fluid receiving/containing area and several fluid flow channels defined therein. In a preferred embodiment, a composite fluid to be separated into component parts may then be delivered to the fluid receiving area from which it may travel under centrifuge conditions through a fluid transport channel to a circumferential fluid separation channel where it may be subjected to substantial centrifugal forces which may separate the composite fluid into respective components. These components may then travel to distinct first and second separated fluid outlet channels. The separated fluid components may then exit from these outlet channels and may then be moved from the separation device to a collection bag for storage or further processing or may then be returned to the donor. The composite fluid may be of various sorts, but is preferably whole blood, and the respective components may then be plasma and red blood cells (RBCs), although buffy coats and/or platelets, inter alia, may also be separated and harvested herewith.
The inlet channel and the first and second fluid outlet channels are preferably pre-selected to have respective inlet and first and second outlet lengths or “heights” (or relative radial distances) that are selected to be related to each other so as to provide a substantial hydraulic or hydrostatic fluid pressure balance between the outlets for the respective separated fluids flowing therethrough. Such a pressure relationship provides for forcing the fluid flow and the outlet balance preferably controls the desired location of the interface between the separated fluid components within the circumferential separation channel. The preferred outlet channel length or height relationship which provides this hydraulic balance may be derived from the general hydrostatic equation &rgr;
2
g
2
h
2
=&rgr;
3
g
3
h
3
wherein the length or height of the first outlet channel in this equation is h
2
, and the length or height of the second outlet channel is h
3
. These relative lengths or heights, h
2
and h
3
, may then be selected so as to provide the appropriate preferred pressure balance given a separating composite fluid to be flowed in separated fluid component parts therethrough. The other variables in the above equation are either fluid dependent, see e.g., &rgr;
2
and &rgr;
3
which represent the respective densities of the separated fluids in the first and second outlet channels, or are otherwise relatively non-selectable and/or for the most part not as consequential or are relatively non-governing in the general equation, e.g., the g
2
and g
3
variables are gravitational o
Felt Thomas J.
Hlavinka Dennis J.
Cooley Charles E.
Gambro Inc
Merkling John R.
Scull Peter B.
Sorkin David
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