Dual blood filter

Claim 2

A blood filter element cascade which can be used in blood transfusions without blockage, and which is capable of removing large particles, such as blood clots, and also small particles down to approximately 20 Mu in size, while passing platelets, red blood cells and at least a substantial proportion of white blood cells, comprising in combination, two filter sheets, arranged in downstream flow sequence in order of progressively increasing fineness; a. the first filter sheet comprising coarse open netting of plastic filamentary material having a pore size within the range from about 800 to about 4,000 microns, small enough to remove blood clots, and coarse enough to do so without being subject to blocking by the blood clots that are strained out, and b. the second filter sheet comprising an open mesh fabric of plastic monofilaments, having a pore size within the range from about 20 to about 50 microns, capable of removing microemboli, lipids and debris, and gas emboli, that pass through the first filter element while passing platelets, white blood cells, and red blood cells.

Claim 3

A blood filter element cascade according to claim 1, in which the first filter sheet is an open-mesh netting prepared by extruding, casting, or molding plastic and having an integral filamentary structure.

Claim 4

A blood filter element cascade according to claim 2, in which the plastic material is selected from polypropylene, polyethylene, polyester, polyamide, and polycarbonate.

Claim 5

A blood filter element cascade according to claim 1, in which the second filter sheet is a woven square-weave mesh of plastic monofilaments having a pore size within the range from about 20 to about 50 microns, the filaments being locked in place at their crossing points.

Claim 6

A blood filter element cascade in accordance with claim 4, in which the monofilaments have a diameter within the range from about 25 to about 50 microns.

Claim 7

A blood filter element cascade in accordance with claim 4, in which the plastic monofilaments are of polyester plastic.

Claim 8

A blood filter element cascade in accordance with claim 1, in which the filaments are heat set to lock them in place.

Claim 9

A blood filter element cascade according to claim 1, in which the two filter sheets are in close juxtaposition, and corrugated or convoluted to provide a high surface area to flow.

Claim 10

A blood filter element cascade according to claim 8, in which second filter sheet is juxtaposed to a spacer having a pore size at least as large as the first filter sheet, and within the range from about 800 to about 10,000 microns.

Claim 11

A blood filter element cascade according to claim 9, in which the spacer has an uneven surface so as to provide drainage and prevent blocking of the filter sheet by the spacer.

Claim 12

A disposable blood filter unit comprising a blood filter element cascade according to claim 1, and a housing having an inlet and an outlet and line connections thereat for fluid flow into and out from the housing, the blood filter element cascade being disposed in the housing across the line of flow therebetween so that fluid flow therebetween must pass through the filter element cascade.

Claim 13

A disposable blood filter unit in accordance with claim 11, in which the blood filter element cascade is in the form of a cylinder, and one line connection has a direct fluid flow conNection to the interior of the filter cylinder.

Claim 14

A disposable filter unit in accordance with claim 11, having a housing made in two portions bonded together.

Claim 15

A disposable filter unit in accordance with claim 13, made of plastic, with the portions fused together into one piece.

Claim 16

A disposable filter unit in accordance with claim 14, including line connection integral with the housing.

Claim 17

A disposable filter unit in accordance with claim 14, having the filter unit bonded to one housing portion.

Claim 18

A disposable filter unit in accordance with claim 16, having the filter unit bonded to one housing portion at the outlet with a direct fluid flow line connection from the filtrate-flow side of the filter element to the outlet.

Claim 19

A disposable blood filter unit according to claim 11, in which the housing is composed at least of first and second generally channel-shaped housing portions, defining therebetween a fluid chamber open at two sides, the first and second housing portions having opposed sides, with mating sections abutting and bonded in a fluid-tight seal to each other, and the blood filter element cascade in sheet form extending across the fluid chamber, across the line of fluid flow between the fluid ports and held at opposed side portions to at least one of the first and second housing portions, and side caps bonded to the first and second housing portions in a fluid-tight seal across the open sides of the fluid chamber and to the sides of the blood filter element cascade extending along such open sides, the side caps and the housing portions holding the sides of the blood filter element cascade, positioning the blood filter element cascade across the fluid chamber, and sealing all the sides of the blood filter element cascade to the housing, so that the fluid flow between the fluid ports must pass through the blood filter element cascade.

Claim 20

A disposable blood filter unit in accordance with claim 18, having four sides, two of the sides being defined by the side caps and two of the sides by the first and second housing portions, and the blood filter element cascade is in four-sided sheet form.

Claim 21

A disposable blood filter unit in accordance with claim 19, in which the blood filter element cascade is in four-sided corrugated sheet form.

Claim 22

A disposable blood filter unit in accordance with claim 18, in which the first and the second housing portions and the fluid ports therein are arranged so that the fluid ports are coaxial.

Claim 23

A disposable blood filter unit in accordance with claim 18, in which all of the housing portions are of plastic material.

Claim 24

A disposable blood filter unit in accordance with claim 22, in which the plastic material is a thermoplastic resin.

Claim 25

A disposable blood filter unit in accordance with claim 23, in which the thermoplastic resin is polypropylene.

Claim 26

A disposable blood filter unit in accordance with claim 22, in which the housing portions are integrated together to form a one-piece housing.

Claim 27

A disposable blood filter unit in accordance with claim 18, in which the blood filter element cascade is held at opposed side portions between the mating sections of the first and second housing portions.

Claim 28

A disposable blood filter unit in accordance with claim 26, in which the blood filter element cascade is integrated to the mating sections by fusion thereof through the pores of the blood filter element cascade.

Claim 29

A disposable blood filter unit in accordance with claim 18, in which the side caps are integrated to the housing portions to form an integral one-piece filter unit.

Claim 30

A disposable blood filter unit in accordance with claim 18, in which each of the housing portions includes at least one projecting portion engaging and supporting opposite sides of the blood filter element cascade, and extending with the blood filter element cascade across the fluid chamber.

Claim 31

A disposable blood filter unit in accordance with claim 18, in which one housing portion comprises a projectIng member holding the opposite end portions of the blood filter element cascade against the other housing portion.

Claim 32

A disposable blood filter unit in accordance with claim 30, in which the mating sections of each housing portion have first projecting members extending towards each other, and abutting endwise, with the first housing portion having second projecting members extending internally of the two abutting portions, and engaging the blood filter element cascade at a portion near its edge.

Claim 33

A disposable blood filter unit in accordance with claim 30, in which the second projecting members also hold the blood filter element cascade tightly against an internal wall of the second housing portion.