Biflex film valves

A check valve, comprising:

• a fluid passage defined by a channel wall forming a channel surface with downstream and upstream ends capable of containing and guiding flowable material as fluid,
• a flexible film device comprising top and bottom surfaces with downstream, upstream, and side edges longitudinally positioned in and extending laterally across said fluid passage and said film device top surface capable of conforming to and sealing with said channel surface,
• an attachment means capable of affixing at least said upstream edge and side edges of said film device to or in a portion of said channel wall so as to define a fluid channel wherein all said flowable material moving through said passage passes between said top surface and said channel surface and the ends of said downstream edge of said film device are affixed to portions of said channel wall so as to leave a portion of said downstream edge unattached and capable of sufficient flexibility so at least a portion of said top surface of said film device is capable of contact with said channel surface;
• and,
• a downstream edge control means capable of preventing a portion of said downstream edge bottom from contact with and effectively sealing with said channel surface and
• to effectively allow pressurized downstream backflow fluid access to said bottom surface of said film device so as to move and position by means of backflow fluidic pressure as a motive force a portion of said top surface of said film device against said channel surface and
• to substantially block by sealing off said fluid channel to pressurized said downstream backflow fluid moving upstream when said backflow fluid is motivated by downstream fluidic pressure greater than upstream fluidic pressure
• yet same film device unblocks and opens said fluid channel to upstream fluid flow moving downstream when said upstream fluid flow is motivated by upstream fluidic pressure greater than downstream fluidic pressure.