Coaxial double filter with integrated filter support
A filter for blood or the like provides for concentric filtration tubes of flexible permeable filtration material held concentrically for flow in parallel through the filtration material of the filtration tubes. Manufacture of the filter may in-mold support rings and pillars to flexible filtration media, the lowermost support rings which may then be assembled together and fit into a filter housing.
1. A filter comprising:
an inner filter portion having a flexible tubular filter element with upper and lower ends separated along a length of the flexible tubular filter element and at least one thermoplastic upper support, and at least one thermoplastic lower support in-molded to the upper and lower ends supporting the upper and lower ends against deformation, and at least one thermoplastic pillar extending between the thermoplastic upper and lower supports and in -molded to the flexible tubular filter element supporting the upper and lower ends in separation;
an outer filter portion surrounding the inner filter portion and having a flexible tubular filter element with upper and lower ends separated along a length of the flexible tubular filter element and at least one thermoplastic upper support, and at least one thermoplastic lower support in -molded to the upper and lower ends supporting the upper and lower ends against deformation, and at least one thermoplastic pillar extending between the thermoplastic upper and lower supports and in-molded to the flexible tubular filter element supporting the upper and lower ends in separation;
a housing surrounding the inner and outer filter portions and having end walls providing an upper coupler and lower coupler respectively on opposite sides of the inner and outer filter portions to receive fluid flow into the housing through the upper coupler to be conducted through at least one of the inner and outer filter portions to exit the housing through the lower coupler;
wherein the thermoplastic lower supports of the inner and outer filter portions join to provide a continuous fluid-blocking wall extending between the lower ends of the inner and outer filter portions, wherein the couplers are adapted to fit within intravenous tubing; and
wherein the thermoplastic upper support of the outer filter portion extends outward to contact an inner wall of the housing to guide fluid flow from the upper coupler to a first chamber between the outer filter portion and the inner filter portion so that fluid may flow from the first chamber along two separate paths, a first path passing only through the outer filter portion to a second chamber formed between the outer filter portion and the housing to flow from the second chamber to the lower coupler and a second path passing only through the inner filter portion to a third chamber within the inner filter portion to flow from the third chamber to the lower coupler;
whereby each of the two separate paths of fluid flow may be filtered by a different one of the inner and outer filter portions.
2. The filter of claim 1 wherein the thermoplastic upper support for the flexible tubular filter element of the inner filter portion blocks fluid flow through the upper end of the flexible tubular filter element of the inner filter portion into the inner filter portion and the thermoplastic upper support for the flexible tubular filter element of the outer filter portion is open to allow fluid flow through the upper end of the flexible tubular filter element of the outer filter portion and into the outer filter portion.
3. The filter of claim 1 wherein an axial length of the flexible tubular filter element for the inner filter portion is substantially less than an axial length of the flexible tubular filter element for the outer filter portion.
4. The filter of claim 1 wherein the thermoplastic lower supports for the flexible tubular filter elements of the inner and outer filter portions include mating connectors allowing mechanical inter-engagement of the thermoplastic lower supports to provide the continuous fluid-blocking wall.
5. The filter of claim 4 wherein the mating connectors provide a snap connection of the lower supports for the inner and outer filter portions into the continuous fluid-blocking wall.
6. The filter of claim 1 wherein each of the flexible tubular filter elements comprises a flexible planar filter medium formed in a tube and has a seam and wherein a thermoplastic pillar of the at least one thermoplastic pillar is in-molded over the seam.
7. The filter of claim 1 wherein the outer filter portion includes two diametrically opposed thermoplastic pillars extending between the thermoplastic upper and lower supports of the outer filter portion and in-molded to the flexible tubular filter element of the outer filter portion.
8. The filter of claim 1 further including standoffs extending between a lower wall of the housing and the thermoplastic lower support of the flexible tubular filter element of the outer filter portion, the standoffs supporting the lower thermoplastic support of the flexible tubular filter element of the outer filter portion to provide fluid flow around the lower thermoplastic support of the flexible tubular filter element of the outer filter portion out of an opening in the lower wall.
9. The filter of claim 1 wherein the thermoplastic upper support for the inner filter portion provides a continuous fluid-blocking wall sealing the top of the inner filter portion to block fluid flow from the upper coupler into the third chamber except through sidewalls of the inner filter portion.
10. The filter of claim 1 wherein the thermoplastic upper support for the outer filter portion provides a continuous fluid-blocking wall sealing the top of the outer filter portion to the housing to block fluid flow from the upper coupler into the second chamber except through sidewalls of the outer filter portion.