Flowable material passage with interposable slide member

Means for filtration of a flowable material comprising, in combination,

• a body defining upstream and downstream passages and having a transverse filter channel and a closed annular flat first sealing surface defining a first opening communicating between one of said passages and said channel,
• a seal member having a closed annular flat second sealing surface directly opposing said first sealing surface and defining a second opening opposing said first opening, said second opening communicating between the other of said passages and said channel,
• a filter movable through the filter channel and comprising a flat bearing plate in slidable contact with one of said sealing surfaces and a filter sheet between the bearing plate and the other of said sealing surfaces,
• means to move the filter from a first position to a second position relative to said openings, and
• means urging the seal member and said filter toward one another and adapted to produce a sealing force therebetween which is constant and uniformly distributed over the contacting surfaces thereof at all positions of the filter in said movement, the bearing plate having a pattern of perforations covered by said filter sheet and dimensioned relative to the sealing surfaces so that at all positions of the filter in said movement, flow of material into said channel through the perforations at the sealing surfaces is prevented and a substantially uniform and constant configuration of the filter is in communication with said passages.