Patent ID: 6916420

Claim:
A cross-flow filter cassette comprising multiple adjacent filtration cells ( 2 ), each of said filtration cells comprising the following stacked elements: (a) a retentate spacer ( 3 ); (b) two retentate spacer frames ( 3 ′, 3 ″) located on opposite sides of said retentate spacer ( 3 ); (c) a divided feed flow passage ( 4 ); (d) a first microporous membrane ( 5 ); (e) a permeate spacer ( 6 ); (f) a permeate collection passage ( 7 ); and (g) a second microporous membrane ( 8 ) separated from said first microporous membrane ( 5 ), said stacked elements having aligned openings in their peripheries that form fluid conduits that are substantially perpendicular to the surfaces of said stacked elements, and wherein said retentate spacer ( 3 ) and said two retentate spacer frames ( 3 ′, 3 ″) together form said divided feed flow passage ( 4 ) and wherein said retentate spacer ( 3 ) comprises an open mesh matrix ( 16 ) with intersecting longitudinal ( 17 ) and transverse ( 18 ) threads that are separated from each other by a distance equal to from about 5 to about 15 times their thickness.