Patent ID: 7011755

Claim:
A filtration funnel with integral prefilter comprising: an open top funnel comprising a reservoir for holding unfiltered fluid therein and an outlet, said funnel further including an inner wall, a final microporous filter including an upstream side, and a downstream side, disposed between said reservoir and said outlet, said final filter sealed with a non-releasable leak-tight seal to said funnel to prevent unfiltered fluid from flowing between said final filter and said outlet, with the downstream side of said final filter in fluid flow communication with said outlet, one or more prefilters disposed between said reservoir and the upstream side of said final filter, with the pore size of said one or more prefilters being greater than or equal to the pore size of said final filter, said one or more prefilters including an upstream surface, a seal ring comprising a ring having a half cross-section with a substantially horizontal top surface, a substantially horizontal bottom surface, with an inner end surface extending from an inner edge of the top surface to an inner edge of the bottom surface, and with an outer end surface extending from an outer edge of the top surface to an outer edge of the bottom surface, the seal ring disposed inside of the funnel above said one or more prefilters, with the shape and size of the perimeter of the outer surface of the seal ring substantially matching the shape and size of the perimeter of a portion of the inner wall of the funnel adjacent to the outer surface of seal ring, with the shape of the perimeter of the inner surface of the seal ring being substantially the same as the shape of the perimeter of the outer surface of the seal ring, with the perimeter of the inner surface of the seal ring being offset inward from the perimeter of the outer surface of the seal ring at all points around the perimeter of the outer surface of the seal ring a sufficient distance to seal the outer periphery of the prefilters disposed below the bottom surface of the seal ring, thereby creating a through hole inside of the perimeter of the inner surface of the seal ring, with the surface area of the through hole being substantially the same as the usable surface area of the final filter, said seal ring sealed to said funnel, with the bottom surfaced of said seal ring pressing against the outer periphery of the upstream surface of said one or more prefilters, thereby sealing said one or more prefilters to said funnel with a non-absolute seal, thereby causing said unfiltered fluid to flow through said one or more prefilters before flowing through said final filter, thereby increasing the volume of fluid that the filtration funnel can filter.