Patent ID: 7445716

Claim:
A method of increasing the productive duration of filtering, in a pressure liquid filter unit, of feed liquid including a carrier liquid and coalescing solids bits which tend to stick together and thus blind a filter element gap, comprising: providing a filter housing having a crossflow passage with an inlet and an outlet spaced apart in said filter housing, a filtrate passage having a filtrate port through which filtrate exits said filter housing, and a filter element having a filter wall which separates said crossflow passage from said filtrate passage wherein an inlet face of said filter element defined by said filter wall faces said crossflow passage on a crossflow side of said filter element to filter said solids bits from said feed liquid passing through said filter element as said feed liquid flows along a crossflow path extending through said crossflow passage in a first flow direction from said inlet to said outlet; crossflowing feed liquid through said crossflow passage so as to flow in said first flow direction along said inlet face of said filter element disposed in said filter housing and thereby washing at least portions of said solids bits from said inlet face, while ultrasonically driving a drive member within said filter housing extending along said inlet face on said crossflow side and thereby reducing the ability of solids bits to stick to said inlet face; passing a portion of said feed liquid through said filter element into and along said filtrate passage to said filtrate port in a second flow direction opposite said first flow direction and passing said portion of said feed liquid out of said filter housing through said filtrate port as filtrate with at least larger solids bits removed by said filter element; passing the remainder of said feed liquid in said first flow direction beyond said filter element to said outlet and expelling same from said outlet of said filter housing as retentate; and said filter element having a mounted filter end supported by said filter housing so as to depend therefrom and a terminal filter end projecting within said filter housing, said filter element being tubular such that said filter wall is surrounded by said crossflowing feed liquid and defines said filtrate passage within the interior of said filter element wherein said filtrate passage communicates with said filtrate port at said mounted filter end and said drive member is disposed exteriorly of said filter element, said crossflowing feed liquid flowing in said first flow direction along said filter wall and past said terminal filter end for said washing of said solids bits beyond said terminal filter end of said filter element, and said filtrate oppositely flowing through said filter passage in said second flow direction away from said terminal filter end.