Liquid purification or separation – Processes – Separating
Reexamination Certificate
1999-11-04
2001-06-26
Kim, John (Department: 1723)
Liquid purification or separation
Processes
Separating
C210S416100, C210S436000, C210S472000
Reexamination Certificate
active
06251292
ABSTRACT:
FIELD OF INVENTION
This invention relates generally to liquid filtration devices. More particularly, this invention relates to an in-line gravity driven liquid filtration device usable to filter blood, blood products, cells and to remove chemical agents used to disinfect or otherwise treat blood or blood products.
BACKGROUND OF THE INVENTION
Typically, gravity feed blood filtration devices require user manipulation of vent filters during the filtration process. The manipulation of the vent filters must occur at the proper time during the filtration process or the system will not filter properly and blood being filtered may be rendered unusable. Since user manipulation of vent filters is time consuming and costly, it is desirable to achieve a liquid filtration device which may filter blood without the manipulation of vent filters or filtration devices. Moreover, blood filtration devices usually allow liquid to remain within the filtration device after filtration has occurred. This remaining liquid, referred to as a hold up volume, is often greater than the desired maximum amount. Also, blood filtration devices allow an undesirably high amount of air that is purged therefrom to be left in the receiving blood bag.
The filtration device disclosed in U.S. Pat. No. 5,472,605, and entitled “A Filtration Device Usable for Removal of Leukocytes and Other Blood Components” issued Dec. 5, 1995, and the filtration device disclosed in U.S. Ser. No. 08/524,049, and entitled “an In-Line Liquid Filtration Device Usable for Blood, Blood Products and the Like” filed Sep. 6, 1995, and the filtration device disclosed in U.S. Ser. No. 08/449,362, and entitled “A Filtration Device Usable for Removal of Leukocytes and Other Blood Components” filed May 24, 1995, and the filtration device disclosed in U.S. Ser. No. 08/661,804, and entitled “A Filtration Device Usable for Removal of Leukocytes and Other Blood Components” filed Jun. 11, 1996, which are hereby incorporated by reference and made a part of the disclosure herein, overcome the aforementioned vent filter manipulation problem. However it is desirable to further reduce the hold up volume of this device, and to allow the device to be used in a vertical orientation, and not drain the outlet tubing so that the blood left in the outlet tubing can be used for cross matching, and to further reduce the manufacturing cost thereof, while maintaining an acceptable total filtration time.
Furthermore, it is desirable to eliminate air pockets within the device. Air pockets will reduce the effective filtration system area by reducing the area of the filter elements where blood may flow.
Although blood filtration devices may provide a means to separate gas from liquid and then vent the gas from the device to atmosphere, they are usually not designed to automatically drain the liquid from the upstream side of the device once filtration has stopped. Moreover, blood filtration devices typically do not have features which prevent the tubing attached thereto from becoming kinked thus impeding blood flow. It is, therefore, desirable to achieve a liquid filtration device which filters blood without the manipulation of vent filters, minimizes hold up volume, that automatically drains the upstream side of the device when the filtration process is complete, that minimizes the volume of air that is added to the receiving blood bag, that reduces air pocket therein, that reduces the possibility of kinked tubing when the device is assembled into a filtration system and packaged for shipping, that can be used in a vertical orientation, and that does not drain the outlet tubing.
SUMMARY OF THE INVENTION
The shortcomings of the prior art may be alleviated and the aforementioned goals achieved by using a filtration device constructed in accordance with the principles of the present invention. The filtration device of the present invention is capable of filtering blood to remove leukocytes, other blood components, cells, and chemical agents which may be used to treat the blood.
The filtration device includes an outlet and inlet therein, a filtration media located within the outlet, and a first channel downstream of the filtration media in fluid flow relationship with the outlet and the filtration media. The cross sectional area of the first channel is defined, in part, by the distance between the filtration media and a surface of the filtration device. The cross sectional area is sized so that filtered biological liquid forces air in the first channel and through the outlet. The cross sectional area of the first channel should be less than or equal to the cross sectional area of the outlet.
The first channel may also be in fluid flow relationship with a second channel having a cross sectional area defined, in part, by the distance between the filtration media and a bottom of the second channel. The cross sectional area of the second channel may be sized so that filtered biological liquid forces air within the second channel to flow into the first channel and through the outlet. The second channel may be a circular shaped channel extending about the perimeter of the active area of the filtration media which intersects with the first channel at a single location. The cross sectional area of the second channel should be less than or equal to the cross sectional area of the first channel.
A plurality of parallel flow channels may be located so that filtered biological liquid therein flows into the first channel and through the outlet. The parallel flow channels have a cross sectional area defined, in part, by the distance between the filtration media and the bottom of the parallel flow channels. The cross sectional area of the parallel flow channel is sized to allow filtered liquid to force air therein to flow into the outlet. The space between each parallel channel should be greater than or equal to twice the width of the parallel flow channel. Also, the height of the parallel flow channels should be less than or equal to approximately twice the width of the channels.
A plurality of cross flow channels may intersect or flow between the parallel flow channels. The cross flow channels may have a cross sectional area defined, in part, by the distance between the filtration media and the bottom of the cross flow channels. The cross sectional areas of the cross flow channels are sized to allow filtered liquid therein to force air therein to flow into the parallel channels and into said outlet. The cross sectional area of the cross flow channels may be less than the cross sectional area of the parallel flow channels. The width of the cross flow channels should be approximately less than or equal to the width of the parallel flow channels. Also, the depth of the cross flow channels should be less than or equal to approximately half the depth of the parallel flow channels.
Air is prevented from becoming entrapped within the filtration device by flowing biological liquid through the filtration system and through the filtration device, creating a negative pressure downstream of filtration media within the filtration device, and forcing air within the filtration device downstream of the filtration media to flow through an outlet. The liquid is forced to flow at a flow rate sufficient to force air to flow into the outlet thereby preventing air from becoming trapped in the filtration media or downstream of the filtration media within the filtration device.
Air located downstream of said filtration device may be forced to flow into a flow path comprising a first channel leading to the outlet of the device using filtered biological liquid. Filtered biological liquid from a second channel may flow into the first channel at a flow rate sufficient to force air from therein into the first channel. Filtered biological liquid from parallel channels may flow into the second channel at a flow rate sufficient to force air from the parallel channels into the second channel. Moreover, filtered biological liquid from cross flow channels may flow into the parallel channels at a flow rate sufficient to force
Clement, Esq. Candice J.
Hemasure Inc.
Kim John
LandOfFree
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